Radio wave scatterer and member for attenuating radio waves equipped with the radio wave scatterer

Abstract

To provide a member with a novel structure that can transmit and attenuate incident radio waves without the need to mix dielectric loss materials such as carbon particles or magnetic loss materials such as iron oxide powder, radio wave absorbing materials, or scatterers. The radio wave scatterer is configured to transmit at least a portion of the incident radio waves and emit the transmitted radio waves in a scattered state, and is characterized by being made of a resin composition containing resin as a main component.

Description

[Technical Field]

[0001] The present invention relates to a radio wave scatterer for attenuating incident radio waves and a member for attenuating radio waves that includes a radio wave scatterer. [Background technology]

[0002] In recent years, information detection means using radio waves (especially millimeter waves) as an information communication medium have been studied in fields such as automobiles, home appliances, and life sciences. For example, in the field of automobile technology, there are collision prevention systems that use radar using radio waves with frequencies of 24 to 81 GHz to detect obstacles and automatically apply the brakes, or measure the speed and distance of surrounding vehicles to control the speed and distance of the vehicle itself. For collision prevention systems to function properly, it is important to minimize the reception of unnecessary radio waves (noise) to prevent misidentification.

[0003] Figure 1 shows an example of the installation of a radar used in such a collision prevention system, in which a radar 36 and a cover member 31 for the radar 36 are placed inside a bumper 38 of an automobile. The radar 36 is attached so as to be surrounded by a side wall 34 of the cover member 31. Radio waves β1 emitted from the radar 36 normally pass through the bumper 38, but some of the radio waves (radio waves β2) are reflected (including multiple reflections) by the bumper 38 and reach the radar 36 or the vicinity of the radar 36. This can cause the radar to malfunction.

[0004] In order to prevent such malfunction, a technology has been proposed in which a radio wave absorber is provided on the surface of the cover member 31 to absorb and eliminate unnecessary radio waves, thereby reducing the amount of radio waves β2 reaching the radar 36 and preventing malfunction of the radar 36. As a radio wave absorber, for example, as shown in Patent Document 1 below, a radio wave absorber mixed with carbon particles that absorb radio waves has been proposed. Also, for example, as shown in Patent Document 2 below, a radio wave absorber mixed with scatterers that scatter radio waves has been proposed. It is also described that a large number of recesses are formed on the radio wave incident surface, but this is premised on the inclusion of scatterers.

[0005] In addition, to prevent the waves reflected by the bumper 38 from becoming strong radio waves in a specific direction, a technology has been proposed in which a component with a surface shaped to diffusely reflect incident radio waves is provided at the reflection points of the bumper 38 or at necessary locations on the shielding plate, thereby dispersing the energy of the reflected waves (Patent Document 3 below). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-230587 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-153135 [Patent Document 3] Patent No. 5696781 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the radio wave absorber disclosed in Patent Document 1 is expensive because carbon particles are mixed in, and the weight of the radio wave absorber is large because the carbon particles mixed in are heavy.

[0008] Furthermore, the radio wave absorber as shown in Patent Document 2 is expensive because it contains a scatterer (second dielectric material), and requires some ingenuity to disperse and arrange the scatterer within the radio wave absorber.

[0009] The inventors have discovered that even a component made solely of a resin composition that transmits incident radio waves can be designed to scatter the radio waves emitted from the component, thereby attenuating the intensity of the emitted radio waves per unit area. Specifically, the inventors discovered that incident radio waves can be attenuated without the need to incorporate a dielectric loss material such as carbon particles, a magnetic loss material such as iron oxide powder, or a scatterer into the resin composition that transmits incident radio waves. Furthermore, the inventors discovered that incident radio waves can be attenuated using a configuration that differs from a configuration that diffusely reflects incident radio waves. Figure 2 is a conceptual diagram showing the scattering of emitted radio waves using this novel configuration.

[0010] One of the objects of the present invention is to provide a component with a novel configuration that can transmit and attenuate incident radio waves without the need to mix in a dielectric loss material such as carbon particles, a magnetic loss material such as iron oxide powder, or a scatterer. [Means for solving the problem]

[0011] One aspect of the present invention provides a radio wave scatterer that is configured to transmit at least a portion of incident radio waves and emit the transmitted radio waves in a scattered state, and that is made of a resin composition containing a resin as a main component.

[0012] The resin composition may transmit at least 20% of radio waves that are incident perpendicularly onto a 3 mm thick flat plate made of the resin composition.

[0013] The radio wave scatterer may have at least two surfaces, one of which constitutes a radio wave incident surface and the other of which constitutes an exit surface, and at least one of the two surfaces may have a structure formed thereon that scatters radio waves.

[0014] The structure may be configured to include at least one protrusion and / or hole.

[0015] When the wavelength of the incident radio wave is λ, the height of the convex portion can be 0.26λ or more, the width of the convex portion can be 0.12λ or more, and the spacing between the convex portions can be 5.1λ or less, and / or the depth of the hole portion can be 0.26λ or more, the width of the hole portion can be 5.1λ or less, and the spacing between the hole portions can be 0.12λ or more.

[0016] The resin composition may have a complex relative dielectric constant, and the imaginary part ε'' of the relative dielectric constant may be 0.1 or less at any frequency between 10 and 300 GHz.

[0017] The resin composition may have a real part ε' of the relative dielectric constant of 2 or more and 4 or less at any frequency of 10 to 300 GHz.

[0018] One aspect of the present invention provides a member for attenuating radio waves, which includes the radio wave scatterer.

[0019] The member for attenuating radio waves may be a molded body, and the radio wave scatterer may be formed on at least a part of the molded body.

[0020] The member for attenuating radio waves may be a cover member for a radar.

[0021] One aspect of the present invention provides a radar assembly in which a radar is attached to the radar cover member.

[0022] One aspect of the present invention provides a bumper including a member for attenuating radio waves.

[0023] One aspect of the present invention provides a vehicle including the member, the radar assembly, and / or the bumper.

[0024] As mentioned above, there have been conventional technologies for absorbing (attenuating) unwanted radio waves. The technology described in Patent Document 1 actively introduces a radio wave loss material into a resin layer into which radio waves are incident, and this radio wave loss material absorbs (attenuates) the unwanted radio waves. The technology described in Patent Document 2 incorporates a scatterer (e.g., air) that scatters radio waves into the resin layer into which radio waves are incident, causing internal scattering within the resin layer to absorb (attenuate) the unwanted radio waves. The technology described in Patent Document 3 suppresses unwanted radio waves by actively diffusely reflecting and attenuating the incident radio waves, or by changing the angle of the reflected wave relative to the incident wave through reflection. In this way, the conventionally known techniques described in Patent Documents 1 to 3 and the technique of the present invention for attenuating radio waves transmitted through a resin layer by scattering them are considered to be different techniques. [Effects of the Invention]

[0025] According to the present invention, a novel configuration can be provided that can attenuate incident radio waves without the need to mix a dielectric loss material such as carbon particles, a magnetic loss material such as iron oxide powder, or a scatterer.

[0026] Hereinafter, embodiments of the radio wave scatterer according to the present invention will be described in detail with reference to the drawings. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a diagram illustrating an example of installation of a radar used in a collision prevention system. [Figure 2] FIG. 10 is a conceptual diagram showing scattering of emitted radio waves by a new configuration. [Figure 3] 1 is a perspective view showing an embodiment of a radio wave scatterer according to the present invention. [Figure 4] 1 is a plan view showing an embodiment of a radio wave scatterer according to the present invention. [Figure 5] FIG. 5 is a cross-sectional view of FIG. 4 . [Figure 6] FIG. 1 is a diagram illustrating an outline of a method for measuring scattering rate. [Figure 7]FIG. 1 is a conceptual diagram showing the relationship between the scattering state and the method for measuring the scattering rate. [Figure 8] FIG. 10 is a diagram showing the relationship between the amount of transmission attenuation and the height of the convex portion based on actual measurements. [Figure 9] FIG. 10 is a diagram showing the relationship between transmittance and height of a convex portion based on scalar diffraction theory. [Figure 10] FIG. 10 is a cross-sectional view of an example of a radio wave scatterer having a shape in which units in which convex portions of different widths are arranged are repeated. [Figure 11] FIG. 10 is a graph showing a comparison of the transmission attenuation at each angle between the sample of Example 14 and the sample of Example 3. [Figure 12] FIG. 10 is a cross-sectional view of another embodiment of a radio wave scatterer according to the present invention. [Figure 13] FIG. 10 is a cross-sectional view of another embodiment of a radio wave scatterer according to the present invention. [Figure 14] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 15] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 16] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 17] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 18] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 19] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 20] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 21] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 22] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 23] 10A and 10B are a plan view and a cross-sectional view of an example of a configuration in which a hole is provided in a support portion of a radio wave scatterer. [Figure 24]FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 25] FIG. 10 is a plan view of another embodiment of a radio wave scatterer according to the present invention. [Figure 26] FIG. 10 is a diagram illustrating the concept of a convex portion volume ratio. [Figure 27] 1 is a perspective view of one embodiment of a member for attenuating radio waves according to the present invention; [Figure 28A] 1 is a plan view of one embodiment of a member for attenuating radio waves according to the present invention; [Figure 28B] 20B is a cross-sectional view of FIG. 20A taken along the line YY. [Figure 28C] 20C is a cross-sectional view of FIG. 20B. [Figure 29A] FIG. 10 is a plan view of another embodiment of a member for attenuating radio waves according to the present invention. [Figure 29B] 21B is a cross-sectional view of FIG. 21A. [Figure 30A] 4A and 4B are diagrams illustrating ridges formed on the inner surface of the peripheral side wall of one embodiment of a member for attenuating radio waves according to the present invention. [Figure 30B] 10A and 10B are diagrams illustrating modified examples of ridges formed on the inner surface of the peripheral side wall of one embodiment of the member for attenuating radio waves according to the present invention. [Figure 30C] 10A and 10B are diagrams illustrating modified examples of ridges formed on the inner surface of the peripheral side wall of one embodiment of the member for attenuating radio waves according to the present invention. [Figure 31] 1 is a perspective view of one embodiment of a radar assembly according to the present invention; [Figure 32] 1 is a diagram showing an overview of one embodiment of a bumper according to the present invention. [Figure 33] 1 is a diagram showing an overview of one embodiment of a vehicle according to the present invention; [Figure 34] FIG. 1 is a diagram illustrating an outline of a method for measuring return loss. [Figure 35A] FIG. 10 is a diagram illustrating an example of curve fitting in the calculation of transmittance. [Figure 35B]FIG. 10 is a diagram illustrating an example of curve fitting in the calculation of transmittance. DETAILED DESCRIPTION OF THE INVENTION

[0028] [Radio wave scatterer] The radio wave scatterer of the present invention is configured to transmit at least a portion of incident radio waves and emit the transmitted radio waves in a scattered state, and is made of a resin composition containing a resin as a main component.

[0029] In the radio wave scatterer of the present invention, the resin composition transmits at least 50% of radio waves incident perpendicularly to a 3 mm-thick flat plate made of the resin composition. This transmittance is preferably 65% ​​or more, and more preferably 85% or more. By achieving at least this preferred transmittance, the addition of a dielectric loss material or the like is unnecessary, enabling weight reduction and low-cost production. The reason why the transmittance of the radio wave scatterer is specified as the transmittance of radio waves incident perpendicularly to a 3 mm-thick flat plate made of the resin composition constituting the radio wave scatterer is as follows: One is that the ratio of total incident power to total emitted power changes depending on the shape of the radio wave scatterer. Another is that it is difficult to measure the total emitted power. As described above, in the present invention, even a component made only of a resin composition that transmits incident radio waves can be scattered by adjusting its shape. Therefore, it is reasonable to specify the characteristics in terms of the transmittance of a component made of a flat plate-shaped resin composition, which is a typical shape that does not scatter emitted radio waves.

[0030] Fig. 3 is a perspective view showing one embodiment of a radio wave scatterer according to the present invention, Fig. 4 is a plan view showing one embodiment of a radio wave scatterer according to the present invention, and Fig. 5 is a VV cross-sectional view of Fig. 4.

[0031] The radio wave scatterer 1 has a support section 4 having a first main surface 2 and a second main surface 3, and a structural section 5 that scatters radio waves is formed on the first main surface 2. The structural section 5 is made up of a plurality of protrusions 6. In this embodiment, the protrusions 6 are ridges that all extend in the same direction and are formed parallel to each other.

[0032] Although the width Q and length P (see FIG. 4) of the radio wave scatterer 1 vary depending on the size of the object to which it is attached, they are usually 1 to 50 cm, more preferably 1.5 to 40 cm, and even more preferably 3 to 30 cm. From the viewpoint of the balance between strength and weight, the thickness T1 of the support portion 3 shown in FIG. 5 is preferably designed to be in the range of 0.5 to 10 mm, more preferably 0.7 to 5 mm, and even more preferably 1 to 3 mm. Furthermore, the thickness T2 of the radio wave scatterer 1, including the height H of the protrusions 6, is preferably designed to be in the range of 0.5 to 20 mm, more preferably 1 to 15 mm, and even more preferably 2 to 10 mm, in order to achieve a sufficient radio wave scattering effect.

[0033] The height H of the convex portion 6 is preferably designed to be in the range of 0.26λ or more, more preferably in the range of 0.51λ or more and 1.5λ or less, and even more preferably in the range of 0.77λ or more and 1.3λ or less, where λ is the wavelength of the incident radio wave.

[0034] The width dimension W of the protrusion 6 at the portion rising from the first main surface 2 is preferably designed to be in the range of 0.26λ or more, more preferably in the range of 0.26λ or more and 3.1λ or less, where λ is the wavelength of the incident radio wave, and even more preferably in the range of 0.51λ or more and 3.1λ or less when the protrusion 6 is dot-shaped.

[0035] Furthermore, when the wavelength of the incident radio wave is λ, the interval S between adjacent protrusions 6 is preferably designed to be 5.1λ or less, more preferably 0.26λ or more and 3.1λ or less, and even more preferably 0.51λ or more and 2.6λ or less. Here, a more preferable range of the interval S is 0.26λ or more and 2.8λ or less when the protrusions 6 are ridge-shaped, and 0.51λ or more and 2.6λ or less when the protrusions 6 are dot-shaped. Note that the interval S is a value measured between the portions of the opposing protrusions 6 rising from the first main surface 2.

[0036] When the wavelength of the incident radio wave is λ, the height H, width W, and spacing S of the protrusions 6 are preferably designed to be in the ranges of 0.26λ or more, 0.12λ or more, and 5.1λ or less, more preferably 0.51λ or more and 1.5λ or less, 0.26λ or more and 3.1λ or less, and 0.26λ or more and 3.1λ or less, and even more preferably 0.51λ or more and 1.5λ or less, 0.26λ or more and 3.1λ or less, and 0.51λ or more and 2.6λ or less. More preferable ranges of the height H, width W, and interval S are 0.51λ or more and 1.5λ or less, 0.26λ or more and 3.1λ or less, and 0.26λ or more and 2.8λ or less when the protrusions 6 are ridge-shaped, and 0.51λ or more and 1.5λ or less, 0.51λ or more and 3.1λ or less, and 0.51λ or more and 2.6λ or less when the protrusions 6 are dot-shaped.

[0037] The performance of the radio wave scatterer with respect to the height H, width W, and spacing S of the convex portions 6 may be verified by preparing and evaluating a sample using the method described in the examples of the present application, or by electromagnetic field analysis simulation.

[0038] As described above, the radio wave scatterer of the present invention is configured to transmit at least a portion of incident radio waves and to emit the transmitted radio waves in a scattered state, and "the transmitted radio waves are emitted in a scattered state" means that the scattering rate is a predetermined value (a "scattering rate III" described below is 1.0% or more) based on measurements obtained by the following measurement. Here, the scattering rate is considered to be "scattering rate I," which is the ratio of scattered waves to straight-traveling transmitted waves of radio waves incident on the radio wave scatterer, and "scattering rate II" or "scattering rate III," which are the ratios of scattered waves to all transmitted waves.

[0039] The method for measuring the scattering rate will now be described. Figure 6 is a diagram outlining the method for measuring the scattering rate. Figure 7 is a conceptual diagram showing the relationship between the scattering state and the method for measuring the scattering rate. The transmission attenuation is measured in the range of 60-90 GHz using a radio wave transmitter / receiver (EAS03, manufactured by Keycom Co., Ltd.) according to the procedure shown below, with reference to JIS R 1679. The transmission attenuation is expressed as the absolute value calculated by the following formula (1). 10Log|P i / P0|···(1) (P i : receiving power, P0: transmitting power)

[0040] As shown in Figure 6, a sample holder 11, a millimeter-wave lens 12, a transmitter 9, and a receiver 10 are arranged. A radio wave with a diameter of 150 mm is transmitted from the transmitter 9. Radio waves are transmitted and received with nothing set in the sample holder 11. The state in which the transmission attenuation is 0 dB (all radio waves are transmitted) is used as the reference for measuring the transmission attenuation of normal incidence to the surface direction of each sample. Next, after setting the samples in the sample holder 11, the receiver is placed at angles of 0°, 15°, 30°, 45°, 60°, and 75° relative to the direction from the transmitter 9 to the receiver 10, which is perpendicular to the surface direction of each sample, as shown in Figure 7. Radio waves are transmitted and received, and the transmission attenuation at 76.5 GHz is measured. Note that if the radio wave scatterer structure is a ridge, the measurement is performed with the longitudinal direction of the ridge formed on the first principal surface perpendicular to the electric field amplitude direction of the incident wave. Based on the measured transmission attenuation at each angle of 0°, 15°, 30°, 45°, 60°, and 75°, each P is calculated from the above equation (1). i / P0 (received / transmitted power ratio) and calculate each P i Based on / P0 (reception / transmission power ratio), the scattering rate I and scattering rate II are calculated using the following equations (2.1) and (2.2). (Scattering coefficient I) = (P at 15°, 30°, 45°, 60°, 75°) i / P0 (total of received / transmitted power ratio) / (P at 0° i / P0 (receive / transmit power ratio) × 100 (2.1) (Scattering coefficient II) = (P at 15°, 30°, 45°, 60°, 75°) i / P0 (total of received / transmitted power ratio) / (P at 0°, 15°, 30°, 45°, 60°, 75° i / P0 (total of reception / transmission power ratio) × 100 (2.2) Here, if scattering rate I is d1 and scattering rate II is d2, they can be converted using the following formula (2.3). d2=(100d1 / (100+100d1))×100...(2.3)

[0041] Furthermore, in the above-mentioned method for measuring the scattering rate, the reception angle of the transmitted wave is set at 5° intervals, and the scattering rate III is calculated using the following formula (2.4). (Scattering coefficient III) = (P at 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°) i / P0 (total of receive / transmit power ratio) / (P at 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75° i / P0 (total of receive / transmit power ratio) × 100 (2.4)

[0042] The scattering rate II of the flat plate-shaped members of Comparative Examples 1 to 5 described below, which are examples of members that do not have a structure 5 that scatters radio waves formed on the first main surface 2, was 0.1% to 0.2%, so as mentioned above, ``the transmitted radio waves are emitted in a scattered state'' means that the scattering rate III is 1.0% or more.

[0043] Ideally, the scattering rate should be based on the ratio of the power of radio waves in the 0° direction to the total power of all the radio waves scattered three-dimensionally in other angular directions, but at present, it is technically difficult to measure this, so the scattering rate is specified as in the above formulas (2.1), (2.2), and (2.4). Furthermore, based on the scattering rate specified in this way, the above-mentioned phrase "transmitted radio waves are emitted in a scattered state" means that the scattering rate II is 1.0% or more.

[0044] Since the sample according to Comparative Example 1 does not have any convex portions formed, the scattering rate, which is the ratio of the total amount of power received when the receiver is installed at 15, 30, 45, 60, and 75 degrees to the power received when installed in the 0 degree direction, is 0.06%, meaning that most of the transmitted radio waves are not scattered. In contrast, the scattered radio wave rate for Example 3 (described below), which has convex portions formed, is 385.38%, indicating that the transmitted radio waves are scattered.

[0045] There are thought to be several mechanisms by which the formation of convex portions enables transmitted radio waves to be emitted in a scattered state, but one main mechanism is thought to be that the convex portions act as a diffraction grating.

[0046] Therefore, we will consider the case where the cross section of the convex portion is rectangular, using diffraction theory as an example. Figure 8 shows the relationship between the transmission attenuation and the height of the convex portion for the samples of Examples 4, 4.1, 4.2, 4.3, and 4.4 described below, calculated using the above measurement method. Figure 8 shows that the transmission attenuation was greatest when the height of the convex portion was 3 mm, and the transmission attenuation tended to decrease as the height of the convex portion increased from 3 mm.

[0047] In the diffraction of light, for a diffraction grating with a rectangular cross section, the zero-order light transmittance is I0 and the real part of the dielectric constant is ε r It is known that the following relation holds (scalar diffraction theory), where h is the height of the convex portion and λ is the wavelength. TIFF2022103156000002.tif1598When λ is fixed at 76.5 GHz and the wavelength is 3.92 mm, I0 is ε r and h, and as in the example, ε r When the dielectric constant is set to 2.6, the relationship between the height of the convex portion and I0 is as shown in Figure 9. As can be seen from Figure 9, I0 is lowest when the height of the convex portion is 3 mm, and I0 tends to increase as the height increases from 3 mm. Here, the zero-order optical transmittance I0 indicates the ratio of the intensity of the straight transmitted light to the total transmitted light, and can be considered to correspond to the transmission attenuation of the straight transmitted wave in the present invention. Then, since the behavior obtained by actual measurement in Figure 8 and the theoretical behavior in Figure 9 are roughly similar, it is inferred that the radio wave scatterer in the present invention is related to the scalar diffraction theory of light. Therefore, by controlling the real part of the permittivity εr and the height of the convex portion h, a radio wave scatterer appropriate for the target radio wave frequency can be obtained.

[0048] Furthermore, according to Bragg's law, the direction (angle) of scattered waves due to diffraction is determined by the period of the convexities (the sum of the width and spacing). Diffracted waves that pass between convexities form constructive and destructive interference fringes. At this time, the constructive parts are observed as scattered waves. The angle at which the transmitted radio waves constructively or destructively interfere with each other is expressed by the following equations (4) and (5). (d: period m; integer) Constructive case: dsinθ=mλ (4) In the destructive case: dsinθ=(m+1 / 2)λ (5) When λ is fixed, the only variables are the constructive angle θ and the period d, so the angle of the scattered wave changes depending on the period. Table 1 shows the change in the constructive angle of the diffracted waves, i.e., the angle of the scattered wave, when the period d is changed.

[0049] [Table 1]

[0050] In contrast, Table 2 corresponds to Example 3 described below, and shows the results of measuring the transmission attenuation by creating a sample with a length P of 150 mm and a width Q of 150 mm, and installing receivers at angles of 0°, 15°, 30°, 45°, 60°, and 75° using a device used to measure scattering efficiency.

[0051] [Table 2]

[0052] From Table 2, it can be seen that the angle at which the transmission attenuation is smallest, i.e., the angle at which scattered waves are observed, is 30°. The width of the convex portions of the sample in Example 3 is 4 mm, and the interval between them is also 4 mm, so the period d is 8, which can be confirmed to be almost the same as the scattered wave direction of 29° for d = 8 in Table 1. Therefore, it can be inferred that the radio wave scatterer of the present invention is also related to Bragg's law. Therefore, the interval between the convex portions can be appropriately arranged based on equations (4) and (5).

[0053] From the above considerations, it can be inferred that the convex portions of the radio wave scatterer function as a diffraction grating, and it is believed that the emission of strong radio waves in a specific direction can be suppressed by using the following configuration. As mentioned above, according to Bragg's law, when a single width and interval (period) are repeated, diffracted waves will constructively interact in a specific direction. Therefore, if different widths are mixed in a repeating structure of widths and intervals, it is thought that this constructive interaction in a specific direction can be suppressed, the amount of transmission attenuation in all directions can be made uniform, and the emission of strong radio waves in a specific direction can be suppressed. In examining these issues, we referred to the theory of optical diffraction, but applying this to millimeter waves is not easy. This is because it is necessary to take into account that radio waves, particularly millimeter and quasi-millimeter waves, have wavelengths that are three orders of magnitude longer than visible light. For example, millimeter waves have characteristics such as being less directional than visible light (more prone to diffraction) and being more likely to pass through objects such as plastic walls and paper than visible light, so it is necessary to take these characteristics into account when designing.

[0054] As an example, a comparison will be made between the radio wave scatterer of Example 14, which will be described later, and which has a shape in which units in which 2 mm, 4 mm, and 8 mm wide convex stripes are arranged in sequence at 4 mm intervals, as shown in Fig. 10, are repeated, and the radio wave scatterer of Example 3, which has a shape in which 4 mm wide convex stripes are arranged at 4 mm intervals. Table 3 and Fig. 11 show the results of measuring the transmission attenuation for the sample of Example 14 and the sample of Example 3, in the above measurement, where receivers were placed at angles of 0°, 15°, 30°, 45°, 60°, and 75°.

[0055] [Table 3]

[0056] In the radio wave scatterer of Example 3, the diffracted waves reinforce each other at around 30°, in accordance with Bragg's law, whereas in the radio wave scatterer of Example 14, where convex stripes of different widths are mixed, it was confirmed that reinforcement does not occur in a specific direction, and a uniform transmission attenuation is obtained in all directions.

[0057] Therefore, in the radio wave scatterer of the present invention, when diffraction is the main factor, by using a configuration in which different widths and spacings are mixed, the amount of transmission attenuation can be made uniform in all directions, and the emission of strong radio waves in a specific direction can be suppressed.

[0058] In the above embodiment, the protrusions 6 are ridges whose cross sections across the longitudinal direction are rectangular, but the shape of the protrusions 6 is not limited to this and can be any other appropriate shape. For example, the cross section may be triangular as shown in FIG. 12, or circular as shown in FIG. 13. When the cross section is a shape other than rectangular (for example, triangular or circular), scattering due to refraction is added to the scattering due to diffraction described above, and it is thought that the degree of scattering will be greater.

[0059] Furthermore, in the above-described embodiment, the protrusions 6 are continuous protrusions in the longitudinal direction, but they may be discontinuous protrusions in the longitudinal direction. Furthermore, the protrusions 6 may be formed in a dot pattern. Fig. 14 is a plan view of an example of a radio wave scatterer in which the protrusions 6 have a shape of a regular square pyramid (with an isosceles triangle cross section) and are arranged in a matrix with an interval S of 0. Fig. 15 is a plan view of an example of a radio wave scatterer in which the protrusions 6 have a shape of a hemisphere (with a semicircle cross section) and are arranged in a matrix with an interval S of 0. In these examples, the protrusions 6 are arranged in a matrix, but the arrangement of the protrusions 6 is not limited to this and may be any other appropriate arrangement, such as a staggered arrangement. Furthermore, the protrusions 6 can be in the form of dots and can be quadrangular prisms (with a rectangular cross section) arranged in a matrix or a staggered pattern. Fig. 16 is a plan view of an example of a radio wave scatterer in which the protrusions 6 are in the form of regular quadrangular prisms (with a rectangular cross section) and are arranged in a matrix at a predetermined interval S. Fig. 17 is a plan view of an example of a radio wave scatterer in which the protrusions 6 are in the form of regular quadrangular prisms (with a rectangular cross section) and are arranged in a staggered pattern at a predetermined interval S. Fig. 18 is a plan view of an example of a radio wave scatterer in which the protrusions 6 are in the form of regular hexagonal prisms (with a rectangular cross section) and are arranged in a honeycomb pattern at a predetermined interval S.

[0060] When the protrusions 6 are stripes, radio waves are scattered primarily in a direction perpendicular to the length of the protrusions due to their diffraction grating-like properties, with little scattering in the length direction. In contrast, when the protrusions 6 are dot-shaped, especially when they are point-symmetric in plan view, radio waves are scattered in all directions in plan view, resulting in more uniform scattering than when the protrusions 6 are stripes. Furthermore, when the protrusions 6 are dot-shaped, the scattering direction of radio waves can be controlled by their arrangement. Figures 16, 17, and 18 above show the scattering direction of radio waves for the shapes and arrangements of the protrusions 6 described above. The right side of each figure shows the results of electromagnetic field simulations using the finite element method (FEM) for transmitted waves for the shapes and arrangements of the protrusions 6 shown in the left side of each figure. When the protrusions 6 are aligned, radio waves are scattered in four directions from adjacent protrusions 6. However, by changing the arrangement to a honeycomb or staggered arrangement, the direction of radio wave diffusion can be increased. As the number of scattering directions of radio waves increases, the radio wave density per unit area decreases, further suppressing the emission of strong radio waves in specific directions.

[0061] Furthermore, in the above embodiment, the convex portions 6 are formed as convex stripes that are parallel to each other, but the convex stripes do not necessarily have to be formed parallel to each other. For example, the convex stripes may be formed so as to be arranged in a zigzag pattern, as in the radio wave scatterer of Example 84 shown in Fig. 19 and described later, or the convex stripes may be formed so as to be arranged radially, as in the radio wave scatterer of Example 85 shown in Fig. 20 and described later. However, forming the convex stripes parallel to each other is preferable because it simplifies the design.

[0062] In the above embodiment, the protrusions 6 are formed as straight protrusions, but the shape of the protrusions is not limited to this and may be formed in any other appropriate shape. For example, as shown in Fig. 21, they may be formed in a zigzag bent shape, or as shown in Fig. 22, they may be formed in a wavy shape.

[0063] Furthermore, when forming the ridges in a location where mud and dirt are likely to accumulate, it is preferable to set the longitudinal direction of the ridges perpendicular to the ground, as this makes it difficult for dirt to accumulate.

[0064] In the above embodiment, the structural portion is composed of a protrusion, but the structural portion may be composed of a hole, or may be composed of a protrusion and a hole. Here, the term "hole" is a concept that includes both a recess, i.e., a bottomed hole, and a through hole.

[0065] Providing protrusions as in the above embodiment increases the material used to fabricate the radio wave scatterer, thereby increasing its weight. Therefore, providing holes in the support section reduces the weight of the radio wave scatterer. Figure 23 shows a plan view and its cross-sectional view along the line XX of an example of a configuration in which holes are provided in the support section of a radio wave scatterer. Similar to the radio wave scatterer in the above embodiment, the radio wave scatterer 1 includes a support section 4 having a first principal surface 2 and a second principal surface 3, and a structure 5 for scattering radio waves is formed on the first principal surface 2. The structure 5 is composed of multiple protrusions 6. In this embodiment, the protrusions 6 are ridges, all extending in the same direction and parallel to each other. Additionally, cylindrical holes 7 are provided between adjacent protrusions 6. The hole 7 has a width (diameter) V and a depth D, and is arranged in a matrix with a spacing U between adjacent hole 7. The hole 7 has a bottom with a thickness T3. With this configuration, as described above, not only can the increase in the weight of the radio wave scatterer be suppressed, but it is also thought that the remaining portion of the support portion 4 adjacent to the hole portion 7 contributes to scattering of the incident radio waves in addition to the protrusion portion 6. Also, although the shape of the hole is cylindrical in Fig. 23, it does not necessarily have to be circular, and any other appropriate shape such as a triangular prism or a square prism can be used.

[0066] The hole portion 7 may be a through hole, but when the radio wave scatterer of this embodiment is applied to a cover member arranged inside the bumper of an automobile as described in the "Background Art" section above, for example, it is preferable that the hole portion 7 be a bottomed hole rather than a through hole in order to not reduce the anti-fouling function (preventing contamination of the radar surface by mud, etc.) which is the function of the cover member.

[0067] In the above embodiment, the structure portion for scattering radio waves formed in the radio wave scatterer was formed on the first principal surface, i.e., the radio wave incident surface. However, the structure portion can also be formed on the second principal surface, i.e., the radio wave exit surface, to cause radio wave scattering. Therefore, the structure portion may be formed on the radio wave exit surface or on both the radio wave incident surface and the radio wave exit surface. When convex portions are provided on both the radio wave incident surface and the radio wave exit surface, the total height of both convex portions may be within the above-mentioned preferred range. When convex portions and / or holes are formed on both the radio wave incident surface and the radio wave exit surface, better transmission attenuation is likely to be achieved by forming the convex portions and / or holes on the radio wave exit surface at positions opposite the convex portions and / or holes formed on the radio wave incident surface. FIG. 24 is a cross-sectional view of an example of a radio wave scatterer having the structure shown in FIG. 5, but with convex portions on the radio wave exit surface at positions opposite the convex portions formed on the radio wave incident surface, and the total height of both convex portions is the same as the convex portion 6 in FIG. 5.

[0068] Moreover, the shape of the convex portion may be stepped. Fig. 25 is a cross-sectional view of an example of a radio wave scatterer in which the shape of the convex portion is stepped in two steps. With such a configuration, it is considered that in addition to the lower step, the upper step also contributes to scattering of the incident radio wave.

[0069] As described above, when the wavelength of the incident radio wave is λ, it is preferable that the height of the convex portions is 0.26λ or more, the width of the convex portions is 0.26 or more, and the interval between the convex portions is 5.1λ or less. Considering that the height, width, and interval between the convex portions correspond to the depth, interval, and width of the holes, it is preferable that when the wavelength of the incident radio wave is λ, the height of the convex portions is 0.26λ or more, the width of the convex portions is 0.26 or more, and the interval between the convex portions is 5.1λ or less, and / or the depth of the holes is 0.26λ or more, the interval between the holes is 0.26λ or more, and the width of the holes is 5.1λ or less.

[0070] Moreover, the height of the convex portion and the depth of the hole are more preferably designed to be in the range of 0.51λ or more, and even more preferably to be in the range of 0.77λ or more.

[0071] Furthermore, it is more preferable that the width of the protrusions at the portions rising from the first main surface and the spacing of the holes at the portions falling from adjacent first main surfaces be designed to be in the range of 0.26λ or more, and even more preferable that they be designed to be in the range of 0.51λ or more.

[0072] Furthermore, the spacing between adjacent protrusions and the width of the holes are more preferably designed to be in the range of 3.10λ or less, and even more preferably in the range of 2.04λ or less. As described above, the spacing between adjacent protrusions is a value measured between opposing portions where the protrusions rise from the first main surface, and the width of the holes is a value measured between opposing portions where the holes fall from the first main surface.

[0073] Furthermore, the convex portion volume ratio described below is preferably designed to be in the range of 3% or more, more preferably in the range of 3.8% or more, even more preferably in the range of 15% or more, even more preferably in the range of 16.7% or more, and even more preferably in the range of 25% or more. Furthermore, the convex portion volume ratio is more preferably designed to be in the range of 90% or less, more preferably in the range of 85.2% or less, even more preferably in the range of 65% or less, even more preferably in the range of 60.9% or less, even more preferably in the range of 55% or less, and even more preferably in the range of 50.0% or less.

[0074] Here, the convex portion volume ratio is the ratio of the volume of the convex portion in a unit structure to the volume of the unit structure space of the structural part. A unit structure is a structure corresponding to a single convex portion in the structural part. The unit structure space is a space surrounded by the bottom surface of the unit structure, a plane parallel to the bottom surface and spaced from the bottom surface by the maximum height of the convex portion in the unit structure as the top surface, and a plane passing through the boundary line of the bottom surface of the unit structure and perpendicular to the bottom surface of the unit structure as the side surface. For example, in the case of a radio wave scatterer 1 shown in the plan view and F-F cross-sectional view of FIG. 26, in which the support portion 4 is flat, the convex portions 6 are dot-shaped, and have the shape of a regular square pyramid with a side length of W on the bottom surface and are arranged in a matrix at intervals of S, the unit structures 8 are the shaded portions in FIG. 26, and the unit structure space 81 is a rectangular parallelepiped space with the bottom surface 83 (a square with a side length of (W+S)) of the unit structure 8 as the bottom surface and the height H of the convex portions 6 as the height.

[0075] The performance of the radio wave scatterer with respect to the height, width, and spacing of the convex portions, as well as the depth, spacing, and width of the holes, and the convex portion volume ratio may be verified by preparing and evaluating samples using the method described in the examples, or may be verified by electromagnetic field analysis simulation.

[0076] Furthermore, in the above embodiment, the case where the incident radio waves are incident perpendicularly to the main surface of the radio wave scatterer has been described, but even when the incident radio waves are incident obliquely to the main surface of the radio wave scatterer, the outgoing radio waves can be scattered. Table 4 corresponds to Example 2 and shows an example of the change in transmission attenuation when the angle of incidence is changed, measured using a sample with a length P of 150 mm and a width Q of 150 mm using an apparatus used to measure the scattering rate.

[0077] [Table 4]

[0078] From Table 4, it can be seen that even when the incident radio wave is incident obliquely on the main surface of the radio wave scatterer, a scattered state can be produced in the outgoing radio wave.

[0079] Furthermore, in the above embodiment, the support portion is a flat plate, but the support portion may be curved.

[0080] Furthermore, in the above embodiment, millimeter waves are used as an example of incident radio waves, but the wavelength of the incident radio waves is not limited to millimeter waves and can be any other appropriate wavelength.

[0081] [Components for attenuating radio waves] A member for attenuating radio waves according to the present invention includes the radio wave scatterer described above.

[0082] FIG. 27 is a perspective view of one embodiment of a member for attenuating radio waves according to the present invention, in which the member for attenuating radio waves is the cover member 31 in the example shown in FIG. 1 in the [Background Art] section.

[0083] The cover member 31, which is a member for attenuating radio waves, is a molded body made of a resin composition, just like the radio wave scatterer 1, and has the same basic configuration as the radio wave scatterer 1. Therefore, parts having the same configuration as the radio wave scatterer 1 are given the same reference numerals, and their explanation will be omitted.

[0084] 19, the cover member 31 has a first opening 32 on its upper surface 39 and a second opening 33 on its lower surface 40, and is formed as a hollow truncated pyramid overall. A plurality of ridges 6 extending in the vertical direction are formed on the inner surface 35 of the side peripheral wall 34. The cover member 31 is usually attached so that the upper surface 39 contacts the object to be attached.

[0085] As shown in Fig. 28A in a plan view, Fig. 28B in a YY cross-sectional view, and Fig. 28C in a ZZ cross-sectional view, the cover member 31 has a height L of typically 0.5 to 25 cm, more preferably 1 to 20 cm, and even more preferably 2 to 15 cm, depending on the size of the attachment target and the radar 36. The length M and depth N are both typically 1 to 50 cm, more preferably 1.5 to 40 cm, and even more preferably 3 to 30 cm.

[0086] The cover member 31 has a plurality of ridges 6 formed on the inner surface 35 of the peripheral side wall 34, which all extend in the vertical direction (the direction connecting the upper surface 39 and the lower surface 40) and are formed so as to be parallel to each other. The width of the ridges 6 decreases with increasing distance from the inner surface 35, and the rise angle θ of the ridges 6 relative to the inner surface 35 of the peripheral side wall 34 is formed as an acute angle.

[0087] According to the above configuration, the plurality of ridges 6 are formed in a special shape on the inner surface 35 of the side wall 34 of the cover member 31, so that sufficient radio wave absorption capacity can be achieved without stacking multiple layers of materials with different dielectric constants. Therefore, it is not necessary to stack layers made of metal or other materials after forming a component of a specific shape, and the component can be provided as a molded body. Furthermore, because the rise angle θ of the ridges 6 relative to the inner surface 35 of the side wall 34 is an acute angle and the ridges 6 extend in the vertical direction, the component can be easily removed from a mold, improving production efficiency.

[0088] In the above embodiment, the entire cover member 31 is formed in a truncated pyramid shape, but the overall shape is not limited to this and may be, for example, a truncated cone shape as shown in Figures 29A and 29B. However, when the overall shape is formed in a truncated pyramid shape, as well as when it is formed in a truncated cone shape, the shape and arrangement of the multiple protrusions 6 formed on the inner surface 35 must be designed taking into consideration the ease of removal from the mold.

[0089] In the above embodiment, the entire cover member 31 is formed in a truncated pyramid shape (a quadrangular truncated pyramid shape), but it may also be in the shape of an n-sided pyramid (where n is a positive integer). The shape of the cover member 31 is not limited to a truncated pyramid shape, and it may be in any appropriate shape, such as a plate shape or a truncated pyramid shape that widens in the opposite direction to the emission direction of the radar wave, in accordance with the shape of the attachment target and the radar 36, etc.

[0090] In the above embodiment, the plurality of ridges 6 formed on the inner surface 35 of the side peripheral wall 34 are formed continuously in the vertical direction (direction connecting the upper surface 39 and the lower surface 40) on the inner surface 35 of the side peripheral wall 34 as shown in Fig. 30A, but the plurality of ridges 6 may be formed intermittently. However, if the plurality of ridges 6 are formed continuously, they tend to be easier to remove from the mold.

[0091] 30B, the plurality of ridges 6 formed on the inner surface 35 of the side peripheral wall 34 rise from the boundary between the upper surface 39 and the side peripheral wall 34 and are formed in a continuous manner (continuously) toward the lower surface 40, but as shown in 22C, the plurality of ridges 6 may rise gently from the periphery of the upper surface 39, or may rise gradually in a curve so that the upper surface 39 and the upper surfaces of the ridges 6 are continuously connected. In this way, when the plurality of ridges 6 are formed so that the upper surface 39 and the upper surfaces of the ridges 6 are continuously connected, the mold tends to be easier to remove.

[0092] Furthermore, in the above embodiment, the multiple ridges 6 formed on the inner surface 35 of the side peripheral wall 34 are formed parallel to each other on the same face of the truncated pyramid as shown in FIG. 30A . However, the multiple ridges 4 do not necessarily have to be formed parallel to each other. For example, on each face of the side peripheral wall 34, the multiple ridges 6 may be arranged in a diverging pattern from the upper surface 39 to the lower surface 40, as shown in FIG. 20 above, so that when the cover member 31 is viewed inward from the lower surface 40, the multiple ridges 6 extend radially from the upper surface 39. Alternatively, the multiple ridges 6 may be formed in a zigzag pattern as shown in FIG. 19 above. However, in terms of ease of removal from a mold, it is preferable that the multiple ridges 6 be formed parallel to each other on the same face of the truncated pyramid as shown in FIG. 29A .

[0093] In the above embodiment, the first opening 32 is provided in the upper surface 39 and the second opening 33 is provided in the lower surface 40, but the upper surface 39 does not necessarily have to have the first opening 32. If the upper surface 39 does not have the first opening 32, the radar 36 may be disposed inside the upper surface 39. Disposing the radar 36 inside the cover member 31 has the advantage that the radar 36 and the cover member 31 can be installed on the mounting target at the same time.

[0094] In the above embodiment, the radio wave scatterer is integrally molded with the cover member to form a member for attenuating radio waves, but a radio wave scatterer that is separate from the cover member may also be attached to the cover member to form a member for attenuating radio waves.

[0095] Furthermore, in the above embodiment, a radar cover member was used as an example of a member for attenuating radio waves, but the member for attenuating radio waves is not limited to this and can be a member for any other appropriate purpose.

[0096] [Radar Assembly] The radar assembly of the present invention is configured by attaching a radar to the above-described radar cover member.

[0097] Figure 31 is a perspective view of one embodiment of a radar assembly according to the present invention. The basic configuration of the radar assembly 10 is similar to that of the cover member 31 and radar 36 of the radar described above. Components having the same configuration as those of the cover member 31 and radar 36 are given the same reference numerals, and their description will be omitted. As shown in Figure 31, the radar 36 is attached to the upper surface 39 of the cover member 31, constituting the radar assembly 10.

[0098] [bumper] The bumper of the present invention includes the above-mentioned member for attenuating radio waves. FIG. 32 is a diagram showing an outline of one embodiment of a bumper according to the present invention. In the "Background Art" section, components having the same configuration as those in the collision prevention system shown in FIG. 1 and the radar assembly shown in FIG. 31 are designated by the same reference numerals, and their description will be omitted. As shown in FIG. 32, a radar assembly 10 is disposed on a chassis (not shown) inside a bumper 38 of a vehicle 11, and a radio wave attenuation plate 91, which is a member for attenuating radio waves, is disposed on the side of the radar assembly 10. In addition, a radio wave attenuation area 92, which is a radio wave scatterer, is molded in the bumper 38. If a radio wave scatterer is molded in the cover member, the radio wave attenuation plate 91 and the radio wave attenuation area 92 may be omitted. If a radio wave scatterer is not molded in the cover member, the radio wave attenuation plate 91 and / or the radio wave attenuation area 92 may be provided. The radar assembly 10 may be attached to the bumper 38.

[0099] [vehicle] The vehicle of the present invention includes the above-described member for attenuating radio waves, a radar assembly, and / or a bumper.

[0100] Figure 33 is a diagram showing an overview of one embodiment of a vehicle according to the present invention. The basic configuration of the radar assembly 10 is similar to that of the radar cover member 31 and radar 36 described above. Components having the same configuration as the cover member 31 and radar 36 are given the same reference numerals, and their description will be omitted. As shown in Figure 33, the radar assembly 10 including the radar cover member, which is a member for attenuating radio waves, is disposed inside a bumper 38 of the vehicle 11. The member for attenuating radio waves and the radar assembly can be disposed in any appropriate position in any combination.

[0101] <Resin composition> The resin composition contains a resin as a main component. The term "main component" refers to a weight ratio of the resin to the total weight of the resin composition, with the lower limit being 50% by weight or more, or 60% by weight or more, or 70% by weight or more, and the upper limit being 99% by weight or less, or 90% by weight or less, or 80% by weight or less.

[0102] The resin that is the main component of the resin composition is not particularly limited, but is preferably a thermoplastic resin, such as polyethylene, polypropylene, polyvinyl alcohol, polyethylene terephthalate, polybutylene terephthalate, ethylene-vinyl acetate copolymer resin, polystyrene, acrylonitrile-styrene resin, acrylonitrile-butadiene-styrene copolymer synthetic resin, ASA resin, AES resin, acrylic resin such as PMMA, MS resin, MBS resin, cycloolefin resin, polyacetal resin, polyamide resin, polyester resin, polycarbonate resin, polyurethane resin, liquid crystal polymer, EPDM, PPS, PEEK, PPE, polysulfone resin, polyimide resin, fluorine-containing resin, thermoplastic elastomer, acrylic elastomer, etc., with polypropylene, polyethylene, and polyamide resin being particularly preferred. Photocurable resins such as epoxy resin and acrylic resin, and thermosetting resins such as silicone resin, also require a curing process, but can also be used.

[0103] The resins constituting the resin composition can be used alone or in combination of multiple types. That is, when a single resin is used, the radio wave scatterer made of the resin composition has excellent mechanical properties, and when multiple types of resins are used in combination, the balance between strength and toughness is excellent. When multiple types of resins are used in combination, for example, polypropylene and EPDM (ethylene propylene diene rubber) can be used in combination.

[0104] The resin composition may be mixed with a filler, such as carbon black for coloring, inorganic substances such as talc, glass fiber, and minerals for improving strength, or a softener for improving flexibility.

[0105] From the viewpoint of reinforcement and moldability (injection molding, etc.), the talc for improving strength preferably has a small particle size D50, which falls within the range of 0.8 to 50 μm, preferably 2 to 30 μm, and more preferably 5 to 20 μm.

[0106] To improve the strength, the longer the glass fiber, the better. However, since the fiber breaks during processing, a length of 1 to 5 mm is sufficient. To further increase the strength, a manufacturing method is available in which a glass fiber roving is introduced into an impregnation die, the filaments are uniformly impregnated with molten thermoplastic resin, and then the fiber is cut to the required length (usually 5 to 20 mm). Furthermore, although the shape of the glass fiber is generally cylindrical, glass fibers having a flat cross-sectional shape may also be used to reduce distortion during molding.

[0107] Examples of the minerals for improving strength include calcium carbonate, silica, clay, mica, silica balloons, aluminum hydroxide, magnesium hydroxide, and titanium oxide, but calcium carbonate and silica are preferred from the viewpoint of cost.

[0108] The carbon black for coloring has, for example, a DBP absorption of 100 ml / 100 g or less as measured in accordance with JIS K 6217 or JIS K 6221. From the viewpoint of coloring power, carbon black having a small particle size and a large specific surface area is preferred, but inexpensive general-purpose carbon black can also be used.

[0109] The softener may be paraffin oil, naphthene oil, aromatic oil, or the like, but it is preferable to select one that is compatible with the resin used.

[0110] Incidentally, particularly preferred combinations of resin and filler constituting the resin composition used in the present invention include those using polypropylene or polyethylene as the resin and talc as the reinforcing filler, or those using polyamide resin as the resin and glass fiber as the reinforcing filler.

[0111] The resin composition used in the present invention may contain additives other than the resin, reinforcing material, and softener, such as flame retardants, impact resistance improvers, reinforcing agents, compatibilizers, weather resistance improvers, antioxidants, pigments, and dyes.

[0112] The resin composition containing the filler can be obtained by mixing (kneading) the filler in a predetermined ratio using, for example, a single-screw or multi-screw kneader, a batch mixer such as a Labo Plastomill, a roll kneader, etc., or by mixing the filler in a dissolved or suspended state using a solvent. From the viewpoint of productivity, the method of mixing using a kneader or a batch mixer is particularly preferred.

[0113] Methods for molding the cover member placed inside the bumper of an automobile using the above resin composition include injection molding, press molding, blow molding, vacuum molding, cutting processing, molding using a photocurable resin, and molding using a 3D printer. Among the above molding methods, injection molding is preferred because of its excellent productivity. The resin composition used in injection molding is generally prepared by mixing the materials in a twin-screw kneader and molding the mixed resin into pellets. The resin pellets are placed in an injection molding machine, melted, and then injected into a mold of a predetermined shape. After cooling and solidifying, the pellets are removed to obtain a molded product.

[0114] The resin composition can transmit at least 20% of radio waves that are incident perpendicularly onto a 3 mm thick flat plate made of the resin composition.

[0115] The resin composition has a complex dielectric constant, and the imaginary part ε'' of the dielectric constant is preferably 0.1 or less, more preferably 0.07 or less, and even more preferably 0.05 or less, at any frequency between 10 and 300 GHz. When the imaginary part ε'' of the dielectric constant has such a value, the resin composition does not need to contain a dielectric loss material or a magnetic loss material, making it possible to reduce the weight and produce at low cost. Furthermore, it is generally known that when the imaginary part ε'' of the dielectric constant has such a value, the resin composition does not absorb radio waves of the corresponding frequency.

[0116] The resin composition preferably has a real part ε' of the relative dielectric constant of 2 or more and 4 or less, more preferably 2.1 or more and 3.5 or less, and even more preferably 2.2 or more and 3.0 or less, at any frequency of 10 to 300 GHz. [Example]

[0117] The radio wave scatterer of the present invention will be further described using the following examples, but the radio wave scatterer of the present invention is not limited to these examples.

[0118] Example 1 Pellets of acrylic elastomer (Kuraray Co., Ltd., LA2330) were press-molded into a 3.0 mm thick plate using a 50 ton vacuum press (Nasho Press Co., Ltd., MS-VPF-50) at a hot plate temperature of 160°C for 20 seconds. The resulting plate-shaped resin molding was cut to produce a plate-shaped support part with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm. Next, a 2.0 mm thick plate-shaped acrylic elastomer was obtained in the same manner, and this was cut to produce a predetermined number of rectangular prisms (protrusions) with a rectangular cross section perpendicular to the longitudinal direction, a height H of 2.0 mm, a width W of 4.0 mm, and a length of 50 mm. These were attached to one surface of the support part using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that the spacing S between adjacent ridges was 4.0 mm, to produce a radio wave scatterer. The characteristics of the obtained radio wave scatterer are shown in Table 5-1.

[0119] Example 2 Except for changing the height H of the ridges to 4.0 mm, a radio wave scatterer was produced in the same manner as in Example 1. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0120] Example 3 Except for using a polypropylene plate (dielectric constant real part 2.3, imaginary part 0.0) as the resin composition, a radio wave scatterer was produced in the same manner as in Example 2. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0121] Example 4 100 parts by weight of polypropylene (EA9HD, manufactured by Japan Polypropylene Corporation) and 7.3 parts by weight of carbon black for coloring (#50, manufactured by Asahi Carbon Co., Ltd. (iodine adsorption capacity 23 mg / g, DBP absorption capacity 63 ml / 100 g)) were charged into an inlet in this order, polypropylene and carbon black, and the mixture was melt-kneaded at 200°C using a Labo Plastomill (manufactured by Toyo Seiki Seisakusho, Ltd.) to prepare a resin composition. The resin composition was removed from the Labo Plastomill and press-molded into a 3 mm thick plate using a 50 ton vacuum press (MS-VPF-50, manufactured by Nasho Press Co., Ltd.) at a hot plate temperature of 200°C for 20 seconds. The processed resin composition was cut into a piece with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm to prepare a support part. Similarly, a resin composition was processed into a flat plate with a thickness of 2.0 mm, which was then cut to produce a predetermined number of rectangular parallelepipeds as convex portions (convex strips), each with a rectangular cross section perpendicular to the longitudinal direction, a height H of 3.0 mm, a width W of 4.0 mm, and a length of 50 mm. These were then attached to one surface of the support using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that the spacing S between adjacent convex strips was 4.0 mm, to produce a radio wave scatterer. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0122] Example 4.1 Except for changing the height H of the ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 4. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0123] Example 4.2 Except for setting the height H of the ridges to 2.5 mm, a radio wave scatterer was produced in the same manner as in Example 4. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0124] Example 4.3 Except for changing the height H of the ridges to 4.0 mm, a radio wave scatterer was produced in the same manner as in Example 4. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0125] Example 4.4 Except for changing the height H of the ridges to 6.0 mm, a radio wave scatterer was produced in the same manner as in Example 4. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0126] Example 5 The resin composition prepared in the same manner as in Example 4 was press-molded into a 3 mm thick plate using a 50 ton vacuum press (MS-VPF-50, manufactured by Nasho Press Co., Ltd.) at a hot plate temperature of 200°C for 20 seconds. The processed resin composition was cut into a piece with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3 mm to prepare a support part. Similarly, a resin composition prepared in the same manner as in Example 4 was press-molded using a 50-ton vacuum press (MS-VPF-50, manufactured by Nasho Press Co., Ltd.) under conditions of a hot plate temperature of 200°C and a pressing time of 20 seconds, and processed into a 5.0 mm-thick flat plate. Two 5.0 mm-thick flat plates of resin composition were bonded together and cut to form the convex portion (protruding strip). Square pyramids with a height H of 9.0 mm and a base side W of 9.0 mm were arranged in a matrix with a spacing S between adjacent square pyramids of 0.0 mm. This was attached to one surface of the support using double-sided tape (No. 5000NS, manufactured by Nitto Denko Corporation) to produce a radio wave scatterer. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0127] Example 6 Except for the fact that the height H of the ridges was set to 1.0 mm, a radio wave scatterer was produced in the same manner as in Example 1. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0128] Example 7 A radio wave scatterer was produced in the same manner as in Example 1, except that the height H of the ridges was 3.0 mm, the width W of the ridges was 1.0 mm, and the spacing S between adjacent ridges was 2.0 mm. The properties of the obtained radio wave scatterer are shown in Table 5-1.

[0129] Example 8 A radio wave scatterer was produced in the same manner as in Example 1, except that the height H of the ridges was 3.0 mm, the width W of the ridges was 16 mm, and the spacing S between adjacent ridges was 12 mm. The properties of the obtained radio wave scatterer are shown in Table 5-2.

[0130] Example 9 Except for setting the height H of the ridges to 3.0 mm and the spacing S between adjacent ridges to 20 mm, a radio wave scatterer was produced in the same manner as in Example 1. The properties of the obtained radio wave scatterer are shown in Table 5-2.

[0131] Example 10 For the convex portions, polypropylene spheres with a diameter of 12.7 mm (1-6602-06, sold by AS ONE Corporation) were cut in half to produce hemispheres with an arc-shaped cross section, a height of 6.4 mm, and a width of 12.7 mm. These were arranged in a matrix on one surface of a flat polypropylene support member made in Example 3, with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm, so that the spacing S between adjacent hemispheres was 0.0 mm, and the hemispheres were attached using double-sided tape (Nitto Denko Corporation, No. 5000NS) to produce a radio wave scatterer. The characteristics of the obtained radio wave scatterer are shown in Table 5-2.

[0132] Example 11 This example corresponds to the embodiment shown in Figure 23. A 2.4 mm thick flat polypropylene plate (dielectric constant: real part 2.3, imaginary part 0.0) was cut into strips to create a flat support part with a width Q of 50 mm, a length P of 50 mm, and a thickness D of 2.4 mm. Φ8 through-holes were drilled in a matrix pattern over the entire surface of this support part with a 3.0 mm spacing U using a drilling machine. Next, a 2.0 mm thick polypropylene plate (dielectric constant: real part 2.3, imaginary part 0.0) was cut to create a predetermined number of rectangular parallelepipeds with a rectangular cross section perpendicular to the longitudinal direction, a height H of 2.0 mm, a width W of 2.0 mm, and a length of 50 mm. These were attached to one surface of the support part using double-sided tape (Nitto Denko Corporation, No. 5000NS) with a spacing S between adjacent ridges of 9.0 mm and so that the ridges and through-holes did not overlap. Furthermore, a polypropylene plate (dielectric constant real part 2.3, imaginary part 0.0) was cut to produce a flat plate-shaped member with a width Q of 50 mm, length P of 50 mm, and thickness T3 of 1.0 mm, which was then attached to the other surface of the support part using double-sided tape (Nitto Denko Corporation, No. 5000NS) to produce a radio wave scatterer. The characteristics of the obtained radio wave scatterer are shown in Table 5-2.

[0133] Example 12 A 1.0 mm thick nylon 6 plate (dielectric constant: real part 3.5, imaginary part 0.065) was cut into strips to create a flat support portion with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 1.0 mm. Next, a 1.0 mm thick nylon 6 plate (dielectric constant: real part 3.5, imaginary part 0.0) was cut to create a predetermined number of rectangular parallelepipeds (convex strips) with a rectangular cross section perpendicular to the longitudinal direction, a height H of 1.0 mm, a width W of 4.0 mm, and a length of 50 mm. These were attached to one surface of the support portion using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that the spacing S between adjacent convex strips was 4.0 mm, to create a radio wave scatterer. The characteristics of the obtained radio wave scatterer are shown in Table 5-2.

[0134] Example 13 Except for changing the height H of the ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 12. The properties of the obtained radio wave scatterer are shown in Table 5-2.

[0135] Example 14 In the same manner as in Example 2, a flat support portion having a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm was fabricated. Next, a 4.0 mm thick polypropylene plate (dielectric constant: real part 2.3, imaginary part 0.0) was cut to form the convex portion (convex stripe). A predetermined number of rectangular parallelepipeds, each having a height H of 4.0 mm, a width W of 2.0 mm, and a length of 50 mm, a height H of 4.0 mm, a width W of 4.0 mm, and a length of 50 mm, and a height H of 4.0 mm, a width W of 8.0 mm, and a length of 50 mm, were fabricated. These were attached to one surface of the support portion using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that units each having convex stripes with widths of 2.0 mm, 4.0 mm, and 8.0 mm arranged in sequence at intervals of 4.0 mm were repeated, thereby fabricating a radio wave scatterer. The obtained characteristics of the radio wave scatterer are shown in Table 5-2.

[0136] Example 15 Except for the fact that the width W of the ridges was set to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0137] Example 16 Except for setting the height H of the ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0138] Example 17 Except for setting the height H of the ridges to 3.0 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0139] Example 18 Except for setting the height H of the ridges to 5.0 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0140] Example 19 Except for setting the height H of the ridges to 7.0 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0141] Example 20 Except for changing the height H of the ridges to 3.0 mm, a radio wave scatterer was produced in the same manner as in Example 12. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0142] Example 21 Except for setting the height H of the ridges to 9.0 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0143] Example 22 Except for setting the height H of the ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0144] Example 23 Except for setting the width W of the ridges to 1.0 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0145] Example 24 Except for setting the height H of the ridges to 3.0 mm and the width W of the ridges to 16 mm, a radio wave scatterer was produced in the same manner as in Example 2. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0146] Example 25 Except for the fact that the width W of the ridges was set to 16 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-1.

[0147] Example 26 Except for setting the interval S between adjacent ridges to 20 mm, a radio wave scatterer was produced in the same manner as in Example 4. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0148] Example 27 Except for setting the interval S between adjacent ridges to 20 mm, a radio wave scatterer was produced in the same manner as in Example 3. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0149] Example 28 A radio wave scatterer was produced in the same manner as in Example 12, except that the height H of the convex portions was 2.0 mm, the width W of the convex stripes was 1.0 mm, and the spacing S between adjacent convex stripes was 1.0 mm. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0150] Example 29 Except for setting the interval S between adjacent ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 28. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0151] Example 30 Except for changing the width W of the ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 28. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0152] Example 31 A radio wave scatterer was produced in the same manner as in Example 28, except that the width W of the ridges was 12 mm and the spacing S between adjacent ridges was 12 mm. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0153] Example 32 A radio wave scatterer was produced in the same manner as in Example 3, except that the height H of the convex portions was 6.0 mm, the width W of the convex stripes was 1.0 mm, and the spacing S between adjacent convex stripes was 1.0 mm. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0154] Example 33 Except for setting the interval S between adjacent ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 32. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0155] Example 34 Except for changing the width W of the ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 32. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0156] Example 35 A radio wave scatterer was produced in the same manner as in Example 32, except that the width W of the ridges was 12 mm and the spacing S between adjacent ridges was 12 mm. The properties of the obtained radio wave scatterer are shown in Table 6-2.

[0157] Example 36 In the same manner as in Example 12, a flat support member having a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm was fabricated. Next, a 2.0 mm thick plate of nylon 6 (dielectric constant: real part 3.5, imaginary part 0.065) was cut to fabricate square prisms having a height H of 2.0 mm and a base side length W of 1.0 mm. These were arranged on one surface of the support member in a matrix with a spacing S between adjacent square prisms of 1.0 mm, and then attached to the support member using double-sided tape (Nitto Denko Corporation, No. 5000NS) to fabricate a radio wave scatterer. The characteristics of the resulting radio wave scatterer are shown in Table 6-3.

[0158] Example 37 Aside from setting the spacing S between adjacent square pillars to 12 mm, a radio wave scatterer was produced in the same manner as in Example 36. The properties of the obtained radio wave scatterer are shown in Table 6-3.

[0159] Example 38 Aside from setting the width W of the square prism to 12 mm, a radio wave scatterer was produced in the same manner as in Example 36. The properties of the obtained radio wave scatterer are shown in Table 6-3.

[0160] Example 39 A radio wave scatterer was produced in the same manner as in Example 36, except that the width W of the square prism was 12 mm and the spacing S between adjacent square prisms was 12 mm. The characteristics of the obtained radio wave scatterer are shown in Table 6-3.

[0161] Example 40 A radio wave scatterer was fabricated in the same manner as in Example 36 except that a flat polypropylene plate (dielectric constant real part 2.3, imaginary part 0.0) with a width Q of 50 mm, length P of 50 mm, and thickness T1 of 3.0 mm, similar to Example 3, was used as the support portion, and a polypropylene plate (dielectric constant real part 2.3, imaginary part 0.0) with a thickness of 6.0 mm was used in fabricating the square prism, and the height H of the square prism was set to 6.0 mm. The characteristics of the obtained radio wave scatterer are shown in Table 6-3.

[0162] Example 41 Except for setting the interval S between adjacent square pillars to 12 mm, a radio wave scatterer was produced in the same manner as in Example 40. The characteristics of the obtained radio wave scatterer are shown in Table 6-3.

[0163] Example 42 Except for the fact that the width W of the square prism was set to 12 mm, a radio wave scatterer was produced in the same manner as in Example 40. The characteristics of the obtained radio wave scatterer are shown in Table 6-3.

[0164] Example 43 A radio wave scatterer was produced in the same manner as in Example 40, except that the width W of the square prism was 12 mm and the interval S between adjacent square prisms was 12 mm. The characteristics of the obtained radio wave scatterer are shown in Table 6-3.

[0165] Example 44 In the same manner as in Example 12, a flat support portion having a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm was fabricated. Next, a 2.0 mm thick plate of nylon 6 (dielectric constant: real part 3.5, imaginary part 0.065) was cut to fabricate a predetermined number of convex portions (convex strips). The convex strips were triangular prisms having an isosceles triangular cross section perpendicular to the longitudinal direction, a height H of 2.0 mm, a base length (width) W of the isosceles triangle of the cross section of 1.0 mm, and a length of 50 mm. These were attached to one surface of the support portion using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that the spacing S between adjacent convex strips was 1.0 mm, thereby fabricating a radio wave scatterer. The characteristics of the resulting radio wave scatterer are shown in Table 6-4.

[0166] Example 45 Except for setting the interval S between adjacent ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 44. The properties of the obtained radio wave scatterer are shown in Table 6-4.

[0167] Example 46 Except for changing the width W of the ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 44. The properties of the obtained radio wave scatterer are shown in Table 6-4.

[0168] Example 45 A radio wave scatterer was produced in the same manner as in Example 44, except that the width W of the ridges was 12 mm and the spacing S between adjacent ridges was 12 mm. The properties of the obtained radio wave scatterer are shown in Table 6-4.

[0169] Example 48 A radio wave scatterer was produced in the same manner as in Example 44, except that the supporting portion was made of flat polypropylene (dielectric constant real part 2.3, imaginary part 0.0) with a width Q of 50 mm, length P of 50 mm, and thickness T1 of 3.0 mm, the same as in Example 3, and the triangular prism was made of a polypropylene plate (dielectric constant real part 2.3, imaginary part 0.0) with a thickness of 6.0 mm, and the height H of the convex ribs was set to 6.0 mm. The characteristics of the obtained radio wave scatterer are shown in Table 6-4.

[0170] Example 49 Except for setting the interval S between adjacent ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 48. The properties of the obtained radio wave scatterer are shown in Table 6-4.

[0171] Example 50 Except for changing the width W of the ridges to 12 mm, a radio wave scatterer was produced in the same manner as in Example 48. The properties of the obtained radio wave scatterer are shown in Table 6-4.

[0172] Example 51 A radio wave scatterer was produced in the same manner as in Example 48, except that the width W of the ridges was 12 mm and the spacing S between adjacent ridges was 12 mm. The properties of the obtained radio wave scatterer are shown in Table 6-4.

[0173] Example 52 Except for setting the interval S between adjacent ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 28. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0174] Example 53 Except for setting the interval S between adjacent ridges to 11 mm, a radio wave scatterer was produced in the same manner as in Example 19. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0175] Example 54 Except for setting the interval S between adjacent ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 30. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0176] Example 53 Except for setting the interval S between adjacent ridges to 11 mm, a radio wave scatterer was produced in the same manner as in Example 31. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0177] Example 56 Except for setting the interval S between adjacent ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 32. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0178] Example 57 Except for setting the interval S between adjacent ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 34. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0179] Example 58 Except for setting the interval S between adjacent ridges to 11 mm, a radio wave scatterer was produced in the same manner as in Example 35. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0180] Example 59 Aside from setting the width W of the square prism to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 36. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0181] Example 60 A radio wave scatterer was produced in the same manner as in Example 37, except that the width W of the square prism was 2.0 mm and the spacing S between adjacent square prisms was 10 mm. The characteristics of the obtained radio wave scatterer are shown in Table 6-5.

[0182] Example 61 Except for setting the spacing S between adjacent square pillars to 11 mm, a radio wave scatterer was produced in the same manner as in Example 39. The characteristics of the obtained radio wave scatterer are shown in Table 6-5.

[0183] Example 62 Except for the fact that the width W of the square prism was set to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 40. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0184] Example 63 Except for the fact that the width W of the square prism was set to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 41. The properties of the obtained radio wave scatterer are shown in Table 6-5.

[0185] Example 64 Except for setting the spacing S between adjacent square pillars to 11 mm, a radio wave scatterer was produced in the same manner as in Example 43. The characteristics of the obtained radio wave scatterer are shown in Table 6-5.

[0186] Example 65 Except for setting the interval S between adjacent ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 44. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0187] Example 66 Except for setting the interval S between adjacent ridges to 11 mm, a radio wave scatterer was produced in the same manner as in Example 45. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0188] Example 67 Except for setting the interval S between adjacent ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 48. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0189] Example 68 Except for setting the interval S between adjacent ridges to 11 mm, a radio wave scatterer was produced in the same manner as in Example 51. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0190] Example 69 A radio wave scatterer was produced in the same manner as in Example 40, except that the height H of the convex portions was 4.0 mm, the width W of the square pillars was 4.0 mm, and the interval S between adjacent square pillars was 4.0 mm. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0191] Example 70 A radio wave scatterer was produced in the same manner as in Example 69, except that the square prisms were arranged in a staggered pattern with the side edges of diagonally adjacent square prisms in contact and the spacing S between adjacent square prisms in the vertical and horizontal directions being 4.0 mm. The characteristics of the obtained radio wave scatterer are shown in Table 6-6.

[0192] Example 71 Aside from setting the height H of the convex portions to 4.0 mm and the width W of the convex stripes to 4.0 mm, a radio wave scatterer was produced in the same manner as in Example 48. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0193] Example 72 A radio wave scatterer was produced in the same manner as in Example 48, except that the height H of the convex portions was 4.0 mm, the width W of the convex stripes was 4.0 mm, and the spacing S between adjacent convex stripes was 2.0 mm. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0194] Example 73 A radio wave scatterer was produced in the same manner as in Example 48, except that the height H of the convex portions was 4.0 mm, the width W of the convex stripes was 4.0 mm, and the spacing S between adjacent convex stripes was 3.0 mm. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0195] Example 74 A radio wave scatterer was produced in the same manner as in Example 48, except that the height H of the convex portions was 4.0 mm, the width W of the convex stripes was 4.0 mm, and the spacing S between adjacent convex stripes was 4.0 mm. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0196] Example 75 The support part was fabricated by using a 3D printer (Keyence Corporation, Agilista) to mold UV-curable acrylic resin (dielectric constant: real part 2.5, imaginary part 0.050) into a flat plate-shaped member with a width Q of 50 mm, length P of 50 mm, and thickness T1 of 3.0 mm. Similarly, the UV-curable acrylic resin was also molded using a 3D printer (Keyence Corporation, Agilista) into a square pyramid with a height H of 4.0 mm and a base side length W of 4.0 mm. This was attached to one surface of the support part using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that the spacing S between adjacent square pyramids was 2.0 mm, creating a radio wave scatterer. The characteristics of the resulting radio wave scatterer are shown in Table 6-6.

[0197] Example 76 Except for setting the spacing S between adjacent square pyramids to 4.0 mm, a radio wave scatterer was produced in the same manner as in Example 75. The properties of the obtained radio wave scatterer are shown in Table 6-6.

[0198] Example 77 In the same manner as in Example 3, a flat support portion having a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm was prepared. Next, a polypropylene cylinder (dielectric constant: real part 2.3, imaginary part 0.0) having a diameter of 8.0 mm and a length of 50 mm was cut in half to prepare a predetermined number of semi-circular cylinders as convex portions (convex stripes), each with a semicircular cross section perpendicular to the longitudinal direction, a height H of 4.0 mm, a diameter (width) W of the semicircular cross section of 8.0 mm, and a length of 50 mm. These semi-circular cylinders were attached to one surface of the support portion using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that the spacing S between adjacent convex stripes was 1.0 mm, thereby preparing a radio wave scatterer. The characteristics of the obtained radio wave scatterer are shown in Tables 6-7.

[0199] Example 78 Except for setting the interval S between adjacent ridges to 2.0 mm, a radio wave scatterer was produced in the same manner as in Example 77. The properties of the obtained radio wave scatterer are shown in Table 6-7.

[0200] Example 79 Except for setting the interval S between adjacent ridges to 3.0 mm, a radio wave scatterer was produced in the same manner as in Example 77. The properties of the obtained radio wave scatterer are shown in Table 6-7.

[0201] Example 80 Except for setting the interval S between adjacent ridges to 4.0 mm, a radio wave scatterer was produced in the same manner as in Example 77. The properties of the obtained radio wave scatterer are shown in Table 6-7.

[0202] Example 81 A radio wave scatterer was produced in the same manner as in Example 10, except that in producing the hemispheres, polypropylene spheres with a diameter of 12.7 mm (1-6602-05, sold by AS ONE Corporation) were used and the arrangement of each hemisphere was such that the spacing S between each of the six surrounding hemispheres was 2.0 mm, resulting in a close-packed arrangement. The properties of the obtained radio wave scatterer are shown in Table 6-7.

[0203] Example 82 Except for setting the interval S between adjacent hemispheres to 4.0 mm, a radio wave scatterer was produced in the same manner as in Example 81. The properties of the obtained radio wave scatterer are shown in Table 6-7.

[0204] Example 83 A flat support member with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm was fabricated in the same manner as in Example 75. Next, a regular hexagonal prism with a height H of 5.0 mm and a base side length of 2.0 mm (width W of 4.0 mm) was created using a 3D printer (Keyence Corporation, Agilista) from UV-curable acrylic resin (dielectric constant: real part 2.5, imaginary part 0.050). These were arranged on one surface of the support member in a honeycomb configuration so that the spacing S between the six surrounding regular hexagonal prisms was all 2.0 mm, and the hexagonal prisms were attached to one surface of the support member using double-sided tape (Nitto Denko Corporation, No. 5000NS) to fabricate a radio wave scatterer. The characteristics of the resulting radio wave scatterer are shown in Tables 6-7.

[0205] Example 84 This example corresponds to the embodiment shown in FIG. 19. A radio wave scatterer was fabricated except that the width W of the protrusions 6 was 2.0 mm and the protrusions were arranged in a zigzag pattern as shown in FIG. 19. The specific arrangement of the protrusions was as follows: the height H of each protrusion was 4.0 mm, the width W was 2.0 mm, and the length was 50 mm. The eight protrusions were arranged so that one end of the leftmost protrusion roughly coincided with a corner of the support portion, and the distance between one end of adjacent protrusions (measured between the opposing portions of the protrusions 6 rising from the first principal surface 2) was 8 mm, and the other end of adjacent protrusions was in contact. In this arrangement, the distance between adjacent protrusions was 4 mm with respect to the midpoint of the protrusions in the longitudinal direction. The characteristics of the obtained radio wave scatterer are shown in Table 6-8.

[0206] Example 85 This example corresponds to the embodiment shown in FIG. 20. A radio wave scatterer was fabricated, except that the width W of the protrusions 6 was 2.0 mm and the protrusions were arranged radially as shown in FIG. 20. The specific arrangement of the protrusions was as follows: The height H of each protrusion was 4.0 mm, the width W was 2.0 mm, and the length was 50 mm. One protrusion was arranged on a line connecting the midpoints of the upper and lower sides of the support part. Next, protrusions were arranged on both sides of this protrusion so that the upper ends of adjacent protrusions were in contact and the distance between the lower ends of adjacent protrusions was 8 mm. Furthermore, protrusions were arranged on the outer sides of each of these protrusions so that the upper ends of adjacent protrusions were in contact and the distance between the lower ends of adjacent protrusions was 8 mm. The characteristics of the obtained radio wave scatterer are shown in Table 6-8.

[0207] Example 86 This example corresponds to the embodiment shown in FIG. 25. Similar to Example 3, a flat support portion having a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm was prepared. Next, a 2.0 mm thick polypropylene plate was cut to prepare a predetermined number of rectangular parallelepipeds as convex portions (convex strips), each having a rectangular cross section perpendicular to the longitudinal direction and measuring 2.0 mm in height, 4.0 mm in width, and 50 mm in length. These were attached to one surface of the support portion using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that the spacing S between adjacent convex strips was 4.0 mm. Next, a 2.0 mm thick polypropylene plate was cut to create a predetermined number of rectangular parallelepipeds as convex portions (convex strips), each with a rectangular cross section perpendicular to the longitudinal direction and a height of 2.0 mm, a width of 2.0 mm, and a length of 50 mm. Each of these was attached to the surface of each of the 4.0 mm wide convex strips mentioned above using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that their centers in the width direction were aligned with each other, thereby creating a radio wave scatterer. The properties of the obtained radio wave scatterer are shown in Table 6-8.

[0208] Example 87 This example corresponds to the embodiment in Fig. 24. A radio wave scatterer was produced in the same manner as in Example 16, except that a convex ridge with a height H of 2.0 mm was also attached to the other surface of the supporting part in a position facing the convex ridge attached to one surface of the supporting part. The characteristics of the obtained radio wave scatterer are shown in Table 6-8.

[0209] Example 88 In the same manner as in Example 3, a flat support portion having a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm was prepared. Next, a 4.0 mm thick polypropylene plate was cut to produce a predetermined number of rectangular parallelepipeds having a rectangular cross section perpendicular to the longitudinal direction, a height H of 4.0 mm, a width W of 12 mm, and a length of 50 mm. Three of the obtained rectangular parallelepipeds were then bonded together using double-sided tape (Nitto Denko Corporation, No. 5000NS) to produce a predetermined number of rectangular parallelepipeds as convex portions (convex strips) having a height H of 12 mm, a width W of 12 mm, and a length of 50 mm. These were then bonded to one surface of the support portion using double-sided tape (Nitto Denko Corporation, No. 5000NS) so that the spacing S between adjacent convex strips was 12 mm, thereby producing a radio wave scatterer. The characteristics of the obtained radio wave scatterer are shown in Tables 6-8.

[0210] Comparative Example 1 A 3.0 mm thick polypropylene plate (dielectric constant real part 2.3, imaginary part 0.0) was cut to produce a flat plate member with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm. The properties of the obtained flat plate member are shown in Table 5-2.

[0211] Comparative Example 2 The resin composition prepared in the same manner as in Example 4 was press-molded using a 50-ton vacuum press (MS-VPF-50, manufactured by Nasho Press Co., Ltd.) under conditions of a hot plate temperature of 200°C and a pressing time of 20 seconds, and processed into a 3.0 mm thick plate. The processed resin composition was cut into a plate-like member having a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm. The properties of the obtained plate-like member are shown in Table 5-2.

[0212] Comparative Example 3 Except for using an acrylic elastomer (LA2330, manufactured by Kuraray Co., Ltd.) as the resin composition, a flat plate-shaped member was produced in the same manner as in Comparative Example 1. The properties of the obtained flat plate-shaped member are shown in Table 5-2.

[0213] Comparative Example 4 A 3.0 mm thick polypropylene plate (dielectric constant: real part 3.5, imaginary part 0.065) was cut to produce a flat plate member with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm. The properties of the obtained flat plate member are shown in Table 5-2.

[0214] Comparative Example 5 A UV-curable acrylic resin (dielectric constant: real part 2.5, imaginary part 0.050) was molded into a flat plate-shaped member with a width Q of 50 mm, a length P of 50 mm, and a thickness T1 of 3.0 mm using a 3D printer (Keyence Corporation, Agilister). The properties of the obtained flat plate-shaped member are shown in Tables 6-8.

[0215] [Table 5-1] [Table 5-2] [Table 6-1] [Table 6-2] [Table 6-3] [Table 6-4] [Table 6-5] [Table 6-6] [Table 6-7] [Table 6-8]

[0216] [evaluation] (Dimensional measurements) The dimensions of the radio wave scatterer, the height, width, and length of the convex portions formed on the radio wave scatterer, and the interval between adjacent convex portions were measured using a vernier caliper.

[0217] (Measurement of scattering rate) The scattering rate was measured using the same method as described in the section above on radio wave scatterers. The transmission attenuation was measured in the range of 60 to 90 GHz using a radio wave transmitter / receiver (EAS03, manufactured by Keycom Co., Ltd.) according to the procedure shown below, with reference to JIS R 1679. The transmission attenuation is expressed as the absolute value calculated by the following formula (1). 10Log|P i / P0|···(1) (P i : receiving power, P0: transmitting power)

[0218] As shown in Figure 6, a sample holder 11, a millimeter-wave lens 12, a transmitter 9, and a receiver 10 were arranged. A radio wave with a diameter of 150 mm was transmitted from the transmitter 9. With the transmitter 9 and receiver 10 in place and nothing set in the sample holder 11, radio waves were transmitted and received. The state in which the transmission attenuation was 0 dB (all radio waves were transmitted) was used as the reference for measuring the transmission attenuation of radio waves incident perpendicularly to the surface direction of each radio wave scatterer. Next, after placing the radio wave scatterer in the sample holder 11, the receiver was placed at angles of 0°, 15°, 30°, 45°, 60°, and 75° relative to the direction from the transmitter 9 to the receiver 10, which was perpendicular to the surface direction of each sample, to transmit and receive radio waves, and the transmission attenuation at 76.5 GHz was measured. When the radio wave scatterer had a ridge structure, the measurement was performed with the longitudinal direction of the ridge formed on the first principal surface perpendicular to the amplitude direction of the electric field of the incident wave. Based on the measured transmission attenuation at each angle of 0°, 15°, 30°, 45°, 60°, and 75°, each P is calculated from the above equation (1). i / P0 (received / transmitted power ratio) and calculate each P iBased on / P0 (reception / transmission power ratio), the scattering rate I and scattering rate II were calculated using the following formulas (2.1) and (2.2). (Scattering coefficient I) = (P at 15°, 30°, 45°, 60°, 75°) i / P0 (total of received / transmitted power ratio) / (P at 0° i / P0 (receive / transmit power ratio) × 100 (2.1) (Scattering coefficient II) = (P at 15°, 30°, 45°, 60°, 75°) i / P0 (total of received / transmitted power ratio) / (P at 0°, 15°, 30°, 45°, 60°, 75° i / P0 (total of reception / transmission power ratio) × 100 (2.2) Here, if scattering rate I is d1 and scattering rate II is d2, they can be converted using the following formula (2.3). d2=(100d1 / (100+100d1))×100...(2.3)

[0219] Furthermore, in the above-mentioned method for measuring the scattering rate, the reception angle of the transmitted wave was set at 5° intervals, and the scattering rate III was calculated using the following formula (2.4). (Scattering coefficient III) = (P at 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°) i / P0 (total of receive / transmit power ratio) / (P at 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75° i / P0 (total of receive / transmit power ratio) × 100 (2.4)

[0220] (Measurement of relative permittivity and permeability) FIG. 34 is a diagram illustrating an outline of a method for measuring return loss. First, the return loss of the flat-plate members of Comparative Examples 1 to 4 was measured at 70 to 90 GHz using a radio wave transceiver (EAS02, manufactured by Keycom Corporation) according to the following procedure, with reference to JIS R 1679. As shown in FIG. 17, a sample holder 11 and a transceiver 13 were arranged, and a reference metal was set in the sample holder 11 to transmit and receive radio waves. The reference metal was a stainless steel plate with a diameter of 150 mm and a thickness of 2 mm. A return loss of 0 dB (total reflection of radio waves) was used as a standard, and this was used as the basis for measuring the return loss of normal incidence relative to the surface direction of each flat-plate member. Then, each flat-plate member was set in the sample holder 11 instead of the reference metal, and radio waves were transmitted and received to measure the return loss.

[0221] Next, the transmission attenuation of the flat plate members of Comparative Examples 1 to 4 was measured using the same measurement method as in the section (Measurement of Transmission Attenuation) described later.

[0222] Next, the transmittance was calculated as follows using the measured values ​​of the reflection attenuation and the transmission attenuation of the straight transmitted wave of the flat plate members of Comparative Examples 1 to 4.

[0223] The impedance of air is Z0, and the relative permeability μ r (=μ r '-jμ r ''), and the relative permittivity is ε r (=ε r '-jε r ''), and wavelength is λ, the material impedance Z and propagation constant γ are expressed by the following equations (6) and (7). TIFF2022103156000017.tif3285When the thickness of the object is d, the reflection loss and transmission loss can be expressed by the following equations (8) and (9) using the above Z and γ according to transmission line theory. Transmission attenuation (dB) = 20log{2 / (A+B / Z0+CZ0+D)} (8) Return loss (dB) = 20 log {(A + B / Z0 - CZ0 - D) / (A + B / Z0 + CZ0 + D) (9) Here, A = cosh(γd), B = Z sinh(γd), C = (1 / Z) sinh(γd), and D = cosh(γd). At this time, μ r , and the expected given ε r are substituted into equations (6) and (7), and based on the obtained Z, γ and the measured thickness d, the return loss and transmission loss in the range of 70 to 90 GHz are calculated from equations (8) and (9), respectively.

[0224] The curve of return loss calculated from the actual measured values ​​and the curve of return loss calculated from the above formulas (6), (7), and (9), and the curve of transmission loss calculated from the actual measured values ​​and the curve of transmission loss calculated from the above formulas (6) to (8) are fitted using the least squares method to obtain the most likely ε r is derived and used as the relative permittivity of each flat plate-like member. Figures 35A and 35B are diagrams showing an example of this curve fitting. r ε r ':3.50,ε r '':When ε is set to 0.20, as shown in Figure 35A, the two curves are separated, but r By performing curve fitting using the least squares method by varying ε, the error between the two curves becomes the smallest. r is ε r ':2.73, ε r '':0.06 is found, and then both curves are fitted as shown in Figure 35B.

[0225] Led ε r Using this, and substituting it again into equations (6) and (7), based on the obtained Z and γ, the transmittance (%) when the thickness d is 3 mm is calculated using the following equation (10). Transmittance (%)=2 / (A+B / Z0+CZ0+D)×100 (10)

[0226] (Calculation of transmission attenuation) The transmission attenuation was measured using the same method as described in the above section (Scattering Rate), except for the differences in the measurement equipment, measurement frequency, diameter of the transmitted radio wave, and the fact that the transmission attenuation was measured only for straight-through transmitted waves. The transmission attenuation was measured at 70 to 90 GHz using a radio wave transmitter / receiver (EAS02, manufactured by Keycom Co., Ltd.) according to the procedure shown below, with reference to JIS R 1679. The transmission attenuation is expressed as the absolute value calculated using the following formula (1). 10Log|P i / P0|···(1) (P i : receiving power, P0: transmitting power)

[0227] As shown in FIG. 6, a sample holder 11, a millimeter-wave lens 12, a transmitter 9, and a receiver 10 were arranged. A radio wave with a diameter of 30 mm was transmitted from the transmitter 9. With the transmitter 9 and receiver 10 in place and nothing set in the sample holder 11, radio waves were transmitted and received. The state in which the transmission attenuation was 0 dB (all radio waves were transmitted) was used as the reference for measuring the transmission attenuation of radio waves incident perpendicularly to the surface direction of each radio wave scatterer. Next, each sample was set in the sample holder 11, radio waves were transmitted and received, and the transmission attenuation at 76.5 GHz was measured. For the radio wave scatterer of the example, the sample was a support having a width Q of 50 mm and a length P of 50 mm, with designated convex portions provided. In the case of convex stripes, measurements were taken with the longitudinal direction of the convex stripes formed on the main surface perpendicular to the amplitude direction of the electric field of the incident wave. Measurements were taken at five locations, including the center of the sample, and offset by 5 mm and 10 mm to the left and right, and the average values ​​were evaluated.

[0228] (evaluation) The following was found from Tables 5-1 to 5-2 and Tables 6-1 to 6-8. The transmission attenuation of the straight-transmitted transmitted wave was 0 to 2 dB in each comparative example, whereas in each example it was 2.9 dB or more, exceeding that of each comparative example. In other words, the radio wave scatterers of each example were able to effectively attenuate the straight-transmitted transmitted wave.

[0229] Furthermore, the following was found from Tables 5-1 to 5-2 and Tables 6-1 to 6-8: The transmission attenuation of the straight transmitted wave was 0 to 2 dB in each comparative example, whereas in Examples 1 to 4, 4, 8, 9, 11, 13, 14, 16 to 19, 21, 54, 57, 60, 61, 63, 69, 70, 72 to 76, 78 to 82 (when the protrusions 6 were ridges), the height H, width W, and interval S of the protrusions 6 were set to 0.51 λ or more and 1.5 λ or less, 0.26 λ or more and 3.1 λ or less, and 0.51 λ or more and 2.6 λ or less, where λ is the wavelength of the incident radio wave. In Examples 1 to 4, 4, 7, 8, 9, 11, 13, 14, 16 to 19, 21, 23, 33, 37, 38, 42, 46, 47, 49, 50, 33, 46, 47, 52 to 58, 65 to 68, 78 to 80, in which the widths were 0.51λ to 1.5λ, 0.51λ to 3.1λ, and 0.51λ to 2.6λ when the convex portions 6 were dot-shaped, the attenuation was 4.0 dB or more, exceeding the comparative examples. That is, the radio wave scatterers of each Example were able to attenuate straight-through transmitted waves more effectively.

[0230] Furthermore, the following was found from Tables 5-1 to 5-2 and Tables 6-1 to 6-8. In each comparative example where the convex volume ratio was 0%, the transmission attenuation of the straight transmitted wave was 0 to 2 dB, whereas when the convex volume ratio was 3% or more and 90% or less, it was possible to achieve 5.0 dB or more, when the convex volume ratio was 15% or more and 65% or less, it was possible to achieve 10.0 dB or more, and when the convex volume ratio was 25% or more and 55% or less, it was possible to achieve 15.0 dB or more. In other words, it was found that in radio wave scatterers having the above convex volume ratios, it was possible to effectively attenuate the straight transmitted wave.

[0231] Furthermore, Example 11 showed a good transmission attenuation. Therefore, it is clear that the configuration in which holes are provided in the support part of the radio wave scatterer can achieve good attenuation of straight transmitted waves while suppressing an increase in the weight of the radio wave scatterer.

[0232] Table 3 and FIG. 10 show the transmission attenuation at each reception angle for Example 4 and Example 14. The following was learned from Table 3 and FIG. 10: In Example 4, the transmission attenuation was large at a reception angle of 30°, which is a specific direction; however, in Example 14, the transmission attenuation was uniform in each reception angle direction, and strong radio waves were not emitted in a specific direction, thereby effectively suppressing the emission of strong radio waves. Therefore, it is believed that by mixing different widths in a repeating structure of widths and intervals, it is possible to suppress constructive interference in a specific direction and effectively suppress the emission of strong radio waves in any emission direction.

[0233] Although the present invention has been described above with reference to the drawings with respect to specific embodiments, the present invention can be modified in many ways other than those shown and described. Therefore, the present invention is not limited to the illustrated and described configurations, and its scope should be defined only by the appended claims and their equivalents. [Explanation of symbols]

[0234] 1 Radio wave scatterer 2 First main surface 3 Second main surface 4 Support part 5 Structural part 6 Convex part 7 Hole 8 Unit Structure 81 Unit structural space 83 Unit structure base 10 Radar Assembly 11 vehicles 31 Cover member H Height of the convex part W Width of the convex part S Spacing of convex parts D Hole depth U Hole spacing V-hole width

Claims

[Claim 1] configured to transmit at least a portion of the incident radio wave and to emit the transmitted radio wave in a scattered state; A radio wave scatterer made of a resin composition whose main component is resin.

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