Electromagnetic wave permeable laminate and electromagnetic wave radar system

Abstract

This allows for greater flexibility in exterior color and effectively suppresses phase shifts in electromagnetic waves from electromagnetic radar equipment. [Solution] The laminate 10 is positioned in front of the electromagnetic wave transmission direction of the electromagnetic wave radar device and is electromagnetic wave transparent. When the front and rear of the electromagnetic wave transmission direction are designated as front and rear, respectively, the laminate 10 has a synthetic resin substrate and a coating film laminated on the front surface of the substrate. The relative permittivity of the coating film is 3.1 or more and 40 or less. The thickness of the coating film has a maximum value at the outer peripheral portion 11 of the laminate 10 and a minimum value at the inner peripheral portion 12 of the laminate 10. The difference between the maximum and minimum values ​​is 20 μm or more and 100 μm or less.

Description

Technical Field

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[0001] The present invention relates to an electromagnetic wave transmissive laminate and an electromagnetic wave radar system.

Background Art

[0002] Patent Document 1 discloses an electromagnetic wave transmissive laminate disposed in front of the traveling direction of electromagnetic waves of an electromagnetic wave radar device. The laminate is, for example, a vehicle part such as an emblem or a front grille disposed in front of a millimeter wave radar device mounted on an automobile.

[0003] As shown in FIG. 6, the laminate 110 includes a base material 120 made of a synthetic resin and a coating film 140 called a color developing layer laminated on the base material 120. The coating film 140 is for giving the exterior color of an automobile. The coating film 140 has a filler and has millimeter wave transmissivity. The coating film is formed by applying a paint to the front surface of the base material or the front surface of a primer layer provided on the front surface of the base material as needed.

[0004] The filler is made of a metal such as aluminum.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] As shown in Figure 6, paint pools 143 tend to form on the outer periphery of the coating 140, where the thickness T of the coating 140 is greater than in other areas due to the surface tension acting on the paint when applied. As mentioned above, if the coating 140 contains filler, the relative permittivity of the coating 140 increases, making it easier for the phase of millimeter waves from the millimeter-wave radar device to shift when they pass through the paint pools 143. As a result, the position detection accuracy of the millimeter-wave radar device may deteriorate. [Means for solving the problem]

[0007] This document describes various embodiments of electromagnetic wave-transparent laminates and electromagnetic wave radar systems for solving the above-mentioned problems. [Aspect 1] A laminate that is positioned in front of the electromagnetic wave transmission direction of an electromagnetic wave radar device and is transparent to electromagnetic waves, When the forward and backward directions of the electromagnetic wave transmission are defined as forward and backward, A base material made of synthetic resin, The substrate has a coating film laminated on its front surface, The relative permittivity of the coating film is 3.1 or more and 40 or less. The thickness of the coating film has a maximum value at the outer periphery of the laminate and a minimum value at the inner periphery of the laminate. The difference between the maximum value and the minimum value is 20 μm or more and 100 μm or less. Electromagnetic wave permeable laminate.

[0008] The portion of the laminate closer to the inner circumference than the outer edge has an electromagnetic wave transmission region that overlaps with the field of view of the electromagnetic wave radar device. In the electromagnetic wave transmission region, the intensity of electromagnetic waves decreases as you move away from the center, i.e., towards the outer edge. For this reason, the outer circumference of the laminate has less impact on the degradation of the position detection performance of the electromagnetic wave radar device due to the thickness of the coating film compared to the inner circumference.

[0009] The greater the thickness of the coating on the outer periphery of the laminate compared to the thickness of the coating on the inner periphery, that is, the greater the difference between the maximum and minimum thicknesses of the coating, the greater the phase shift of electromagnetic waves passing through the outer periphery. Furthermore, if the above difference is the same, the smaller the relative permittivity of the coating, the smaller the phase shift of electromagnetic waves.

[0010] Here, if the relative permittivity of the coating film is 40, then when the above difference is 100 μm, the phase shift of the electromagnetic wave is 1.0 deg. As mentioned above, paint buildup occurs at the outer edge of the coating film, making it technically difficult to reduce the above difference to less than 20 μm. If the above difference is reduced to less than 20 μm by reducing the overall thickness of the coating film, the durability of the coating film may be significantly impaired by external stresses such as flying stones and ultraviolet rays. Furthermore, the relative permittivity of a coating film containing filler is 3.1 or higher.

[0011] Based on these considerations, the above configuration allows for suppressing the phase shift of electromagnetic waves transmitted through the outer periphery of a laminate, where the relative permittivity of the coating film is between 3.1 and 40, to 1.0 degree or less. Furthermore, since the above difference is 20 μm or more, the durability of the coating film is improved. Consequently, the degree of freedom in appearance color can be increased, and the phase shift of electromagnetic waves in electromagnetic radar equipment can be appropriately suppressed.

[0012] [Aspect 2] The aforementioned coating film comprises a base resin and a filler. The electromagnetic wave-transmitting laminate described in Embodiment 1.

[0013] The dielectric constant of coatings containing fillers such as aluminum is often between 3.1 and 40. In this regard, the above configuration allows for greater freedom in the appearance color of the laminate by using a coating film containing fillers, and also effectively suppresses the phase shift of electromagnetic waves as they pass through the laminate.

[0014] [Aspect 3] Electromagnetic wave radar equipment, The electromagnetic wave radar system includes the electromagnetic wave transmissive laminate described in Embodiment 1 or Embodiment 2, which is disposed in front of the transmission direction of the electromagnetic wave of the electromagnetic wave radar device. In a portion of the laminate on the inner peripheral side rather than the peripheral portion, an electromagnetic wave transmission region overlapping with the viewing angle of the electromagnetic wave radar device is provided. The outer peripheral portion includes the outer peripheral edge of the electromagnetic wave transmission region. Electromagnetic wave radar system.

[0015] It is possible to achieve the same operational effects as the invention described in Embodiment 1 or Embodiment 2.

Advantages of the Invention

[0016] According to the present invention, the degree of freedom in appearance color can be increased, and the phase shift of the electromagnetic wave of the electromagnetic wave radar device can be appropriately suppressed.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 is a side view showing a laminate and an electromagnetic wave radar device according to an embodiment. [Figure 2] FIG. 2 is a front view of the laminate of FIG. 1. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing an enlarged portion A of FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2. [Figure 5] FIG. 5 is a graph showing the relationship between the difference between the maximum value and the minimum value of the thickness of the coating film and the magnitude of the phase shift of the electromagnetic wave when passing through the outer peripheral portion of the laminate. [Figure 6] FIG. 6 is a cross-sectional view of a conventional laminate.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, referring to FIGS. 1 to 5, an embodiment of the electromagnetic wave transmissive laminate and the electromagnetic wave radar system will be described. In this embodiment, the electromagnetic wave radar system is implemented as a millimeter-wave radar system mounted on a vehicle, and the electromagnetic wave-transparent laminate (hereinafter referred to as the laminate) is implemented as an exterior component of the vehicle.

[0019] In the following explanation, the front and rear sides of a vehicle in the longitudinal direction will be simply referred to as the front and rear sides, respectively. As shown in Figure 1, the electromagnetic wave radar system comprises an electromagnetic wave radar device 90 mounted on a vehicle and a laminated body 10 positioned in front of the electromagnetic wave transmission direction of the electromagnetic wave radar device 90.

[0020] <Electromagnetic wave radar device 90> As shown in Figure 1, the electromagnetic wave radar device 90 of this embodiment is installed at the front of the vehicle and transmits electromagnetic waves (millimeter waves in this embodiment) forward. In this embodiment, the front of the vehicle in the longitudinal direction coincides with the forward direction of electromagnetic wave transmission.

[0021] <Laminate 10> As shown in Figure 1, the laminate 10 covers the electromagnetic wave radar device 90 in front of it. The laminate 10 is, for example, a cover that forms the outer shell of the front of a vehicle.

[0022] The laminate 10 has electromagnetic wave transparency. The laminate 10 of this embodiment has millimeter wave transparency. As shown in Figure 2, the laminate 10 of this embodiment is rectangular in front view. However, the shape of the laminate 10 is not limited to a rectangular shape in front view, and can be changed as appropriate to a trapezoidal or elliptical shape, etc.

[0023] As shown in Figure 3, the laminate 10 comprises, in order from the rear, a base material 20, a primer layer 30, a coating film 40, and a protective layer 50. The base material 20 is made of synthetic resin and has electromagnetic wave permeability. The base material 20 in this embodiment has millimeter wave permeability. The resin material that forms the base material 20 is a thermoplastic resin such as polypropylene (PP), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), acrylonitrile-butadiene-styrene copolymer (ABS) resin, acrylonitrile-ethylene-propylene-diene-styrene (AES) resin, acrylonitrile-styrene-acrylate copolymer (ASA) resin, or polycarbonate (PC). The base material 20 in this embodiment is polycarbonate.

[0024] In this embodiment, the peripheral edge 13 of the front surface of the base material 20 is provided with a chamfered portion 21 with an R-chamfer (see Figure 4). The dielectric constant of the base material 20 is preferably 2.5 or higher and 3.0 or lower.

[0025] The primer layer 30 enhances the adhesion between the substrate 20 and the coating film 40, and is laminated on the front surface of the substrate 20. The primer layer 30 is made of synthetic resin and has electromagnetic wave permeability. The primer layer 30 in this embodiment has millimeter wave permeability. The primer layer 30 is formed of a well-known resin paint for primers.

[0026] The dielectric constant of the primer layer 30 is preferably 3.1 or higher and 38 or lower. The coating film 40 is for producing the appearance color of the laminate 10 and is laminated in front of the primer layer 30. In this embodiment, the coating film 40 is laminated in front of the substrate 20 via the primer layer 30.

[0027] The coating film 40 is made of synthetic resin and has electromagnetic wave permeability. The coating film 40 in this embodiment has millimeter wave permeability. The coating film 40 is formed by applying a paint containing a base resin 41 and a filler 42 to the front surface of the primer layer 30.

[0028] As for the method of applying the paint, known methods such as spray coating, dipping, shower coating, flow coating, and roll coating can be used. The base resin 41 is made from resin materials found in well-known resin coatings such as acrylic resins, urethane resins, polyester resins, epoxy resins, melamine resins, alkyd resins, and phenolic resins.

[0029] The filler 42 can have a higher dielectric constant than the base resin 41. The materials for the filler 42 include bright materials such as mica, pearl mica, and glass flakes, metallic conductive fillers such as aluminum flakes, metal oxide-based conductive fillers such as zinc oxide, and metal-coated conductive fillers in which the surface of mica or glass flakes is coated with a metal such as aluminum or nickel.

[0030] The filler 42 in this embodiment is aluminum flakes. The relative permittivity of the coating film 40 is 3.1 or higher and 40 or lower. More preferably, the relative permittivity of the coating film 40 is 4.0 or higher and 30 or lower.

[0031] The protective layer 50 provides durability to the laminate 10 and is laminated on the front surface of the coating film 40. The protective layer 50 is made of synthetic resin and has electromagnetic wave permeability. The protective layer 50 in this embodiment has millimeter wave permeability. The protective layer 50 is what is commonly called a clear coat and is formed of a well-known resin paint for clear coats.

[0032] The relative permittivity of the protective layer 50 is between 2.5 and 3.0. As shown in Figures 1 and 2, an electromagnetic wave transmission region 14 is provided in the portion of the laminate 10 that is on the inner side of the peripheral edge 13, and which overlaps with the field of view (FOV) R of the electromagnetic wave radar device 90.

[0033] As shown in Figure 2, the thickness T of the coating film 40 has a maximum value Tmax at the outer peripheral portion 11 of the laminate 10 and a minimum value Tmin at the inner peripheral portion 12 of the laminate 10.

[0034] The difference ΔT between the maximum value Tmax and the minimum value Tmin is between 20 μm and 100 μm. The inner circumference portion 12 is the inner circumference portion of the outer circumference portion 11 of the laminate 10.

[0035] The outer peripheral portion 11 includes the outer edge 15 of the electromagnetic wave transmission region 14. The distribution of the thickness T of the coating film 40 described above is achieved by adjusting the front surface shape of the substrate 20 and the coating application conditions. For example, when coating by spray coating, it is preferable to adjust at least one of the spray application angle, distance, and application time relative to the front surface of the substrate 20.

[0036] The outer peripheral portion 11 is the portion of the laminate 10 from the peripheral edge 13 toward the inner peripheral side to a predetermined length ΔL. The predetermined length ΔL is, for example, 33 mm. In the case of the laminate 10 of this embodiment, the outer peripheral portion 11 is the portion between the right peripheral edge 13 of the laminate 10 in Figure 2 and the right vertical line VL1 in Figure 2, the portion between the left peripheral edge 13 of the laminate 10 in Figure 2 and the left vertical line VL2 in Figure 2, the portion between the upper peripheral edge 13 of the laminate 10 in Figure 2 and the upper horizontal line HL1 in Figure 2, and the portion between the lower peripheral edge 13 of the laminate 10 in Figure 2 and the lower horizontal line HL2 in Figure 2.

[0037] As shown in Figure 4, the starting point of the predetermined length ΔL is the inner circumferential end 22 of the chamfered portion 21 of the base material 20, the so-called R end. As shown in Figure 2, the inner circumference portion 12 is the area enclosed by the four lines VL1, VL2, HL1, and HL2 in Figure 2.

[0038] <Operation of this embodiment> An electromagnetic wave transmission region 14 is provided in the portion of the laminate 10 that is closer to the inner circumference than the peripheral edge 13, and this region overlaps with the field of view R of the electromagnetic wave radar device 90. In the electromagnetic wave transmission region 14, the intensity of electromagnetic waves decreases as you move away from the center, i.e., towards the outer circumference. For this reason, the outer circumference portion 11 of the laminate 10 has less influence on the reduction in the position detection performance of the electromagnetic wave radar device 90 caused by the thickness T of the coating film 40 compared to the inner circumference portion 12.

[0039] Figure 5 shows the relationship between the difference ΔT between the maximum value Tmax and the minimum value Tmin of the thickness T of the coating film 40 when the relative permittivity of the coating film 40 is 40, and the magnitude of the phase shift of electromagnetic waves when they pass through the outer peripheral portion 11 of the laminate 10.

[0040] As the thickness T of the coating film 40 on the outer circumference 11 of the laminate 10 increases relative to the thickness T of the coating film 40 on the inner circumference 12, that is, as the difference ΔT between the maximum value Tmax and the minimum value Tmin of the coating film thickness T increases, the phase shift of the electromagnetic waves passing through the outer circumference 11 increases. Furthermore, if the above difference ΔT is the same, the phase shift of the electromagnetic waves decreases as the relative permittivity of the coating film 40 decreases.

[0041] As shown in Figure 5, when the relative permittivity of the coating film 40 is 40, the phase shift of the electromagnetic wave is 1.0 deg when the above difference ΔT is 100 μm. As mentioned above, paint accumulation occurs in the outer peripheral portion 11 of the coating film 40, making it technically difficult to reduce the above difference ΔT to less than 20 μm. If the overall thickness of the coating film 40 is reduced to less than 20 μm, the durability of the coating film 40 may be significantly impaired by external stresses such as flying stones and ultraviolet rays. In addition, the relative permittivity of the coating film 40 containing the filler 42 is 3.1 or higher.

[0042] Based on these findings, the laminate 10 of this embodiment allows for the phase shift of electromagnetic waves transmitted through the outer peripheral portion 11 of the laminate 10 to be suppressed to 1.0 degree or less, in a laminate 10 where the relative permittivity of the coating film 40 is 3.1 or more and 40 or less. Furthermore, since the above difference ΔT is 20 μm or more, the durability of the coating film 40 is improved.

[0043] <Effects of this embodiment> (1) The relative permittivity of the coating film 40 of the laminate 10 is 3.1 or more and 40 or less. The thickness T of the coating film 40 has a maximum value Tmax at the outer peripheral portion 11 of the laminate 10 and a minimum value Tmin at the inner peripheral portion 12 of the laminate 10. The difference ΔT between the maximum value Tmax and the minimum value Tmin is 20 μm or more and 100 μm or less.

[0044] With this configuration, the above-mentioned effects are achieved, which increases the degree of freedom in the appearance color and allows for the appropriate suppression of the phase shift of the electromagnetic waves of the electromagnetic wave radar device 90. (2) The coating film 40 contains a base resin 41 and a filler 42.

[0045] The relative permittivity of a coating film 40 containing fillers 42 such as aluminum is often between 3.1 and 40. In this regard, the above configuration allows for greater freedom in the appearance color of the laminate 10 by the coating film 40 containing the filler 42, and also allows for appropriate suppression of the phase shift of electromagnetic waves when they pass through the laminate 10.

[0046] (3) The electromagnetic wave radar system comprises an electromagnetic wave radar device 90 and a laminated body 10 positioned in front of the electromagnetic wave transmission direction of the electromagnetic wave radar device 90. The portion of the laminated body 10 that is on the inner side of the peripheral edge 13 of the laminated body 10 is provided with an electromagnetic wave transmission region 14 that overlaps with the field of view R of the electromagnetic wave radar device 90. The outer peripheral portion 11 includes the outer peripheral edge 15 of the electromagnetic wave transmission region 14.

[0047] With this configuration, the same effects as described in (1) above can be achieved. <Variation> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0048] The chamfered portion 21 on the peripheral edge 13 of the front surface of the base material 20 can be omitted. In this case, the starting point of the predetermined length ΔL can be the outer peripheral edge of the front surface of the base material 20. • If adhesion between the substrate 20 and the coating film 40 can be ensured, the primer layer 30 may be omitted.

[0049] The protective layer 50 can be omitted. The coating film 40 may have a relative permittivity of 3.1 or more and 40 or less, and may be a coating film 40 that does not contain filler 42. [Explanation of Symbols]

[0050] 10,110…Laminate 11...Outer peripheral part 12...Inner circumference 13… Peripheral area 14...Electromagnetic wave transmission area 20,120…Base material 21... Chamfered section 22...end 30…Primer layer 40,140…coating film 41…Base resin 42… Filler 50…protective layer 90... Electromagnetic wave radar device 143...Paint buildup R…Viewing angle

Claims

1. A laminate that is positioned in front of the electromagnetic wave transmission direction of an electromagnetic wave radar device and is transparent to electromagnetic waves, When the forward and backward directions of the electromagnetic wave transmission are defined as forward and backward, A base material made of synthetic resin, The substrate has a coating film laminated on its front surface, The relative permittivity of the coating film is 3.1 or more and 40 or less. The thickness of the coating film has a maximum value at the outer periphery of the laminate and a minimum value at the inner periphery of the laminate. The difference between the maximum value and the minimum value is 20 μm or more and 100 μm or less. Electromagnetic wave permeable laminate.

2. The aforementioned coating film comprises a base resin and a filler. The electromagnetic wave-transmitting laminate according to claim 1.

3. Electromagnetic wave radar equipment, The electromagnetic wave-transparent laminate according to claim 1 or claim 2 is positioned in front of the electromagnetic wave transmission direction of the electromagnetic wave radar device, In the portion of the laminated body closer to the inner circumference than the peripheral edge, an electromagnetic wave transmission region is provided that overlaps with the field of view of the electromagnetic wave radar device. The aforementioned outer peripheral portion includes the outer edge of the electromagnetic wave transmission region. Electromagnetic wave radar system.

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