ELECTROMAGNETIC WAVE TRANSPARENT LAMINATE

Abstract

A laminate exhibits permeability to electromagnetic waves. The laminate comprises a substrate made of a synthetic resin and an ink layer laminated to the substrate. The relative dielectric constant of the ink layer ranges from 3.1 to 66.7. The effective dielectric constant of the laminate is greater than the relative dielectric constant of the substrate and less than or equal to 3.0.

Description

BACKGROUND1. Area

[0001] The present disclosure relates to a laminate transparent to electromagnetic waves. 2. Description of the state of the art

[0002] Japanese Patent No. 4158646 discloses a front grille for a car (hereinafter referred to as a front grille) provided in a beam path of a radar device. The front grille disclosed in this document includes a base made of a synthetic resin, a titanium nitride layer covering the outer surface of the base, and an aluminum nitride layer covering the titanium nitride layer. The front grille has millimeter-wave transmittance. The relative dielectric constants of the titanium nitride layer and the aluminum nitride layer are set to be substantially the same as those of the base. The relative dielectric constant of the base made of a synthetic resin is less than or equal to 3.0.

[0003] Pigment paints used for automotive components contain metallic fillers. The relative dielectric constant of a coating film containing metallic fillers exceeds 3.0. Therefore, it is considered difficult to ensure electromagnetic wave permeability for a front grille with a coating film containing metallic fillers. SUMMARY

[0004] This summary is intended to provide a selection of concepts in simplified form, which are further described in the detailed description below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0005] According to a general aspect, an electromagnetic wave-transmissive laminate having electromagnetic wave transmittance comprises a substrate made of a synthetic resin and an ink layer laminated on the substrate. A relative dielectric constant of the ink layer is in a range of 3.1 to 66.7. An effective dielectric constant of the laminate is greater than a relative dielectric constant of the substrate and less than or equal to 3.0.

[0006] Other features and aspects will become apparent from the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a positional relationship between a laminate according to an embodiment and a millimeter wave radar device. Fig.2 is a cross-sectional view showing a layer structure of the laminate used in Fig. 1 is shown.

[0007] In the figures and the detailed description, the same reference numerals refer to the same elements. The drawings are not necessarily to scale, and the relative size, proportions, and representation of elements in the drawings may be exaggerated for clarity, illustration, and simplicity. DETAILED DESCRIPTION

[0008] This description provides a comprehensive understanding of the methods, devices, and / or systems described. Modifications and equivalents of the methods, devices, and / or systems described will be obvious to one skilled in the art. Sequences of operations are merely exemplary and may be changed as obvious to one skilled in the art, except for operations that necessarily occur in a particular order. Descriptions of functions and constructions known to one skilled in the art may be omitted.

[0009] Example embodiments may take various forms and are not limited to the described examples. However, the described examples are detailed and complete, and will fully convey the scope of the disclosure to one skilled in the art.

[0010] In this description, “at least one of A and B” should be understood to mean “only A, only B, or both A and B”.

[0011] A laminate 10 according to an embodiment will now be described with reference to Fig. 1 and Fig. 2. The laminate 10 is used as an exterior component of a vehicle.

[0012] In the following description, a front side and a rear side in a front-rear direction of a vehicle are each simply referred to as a front side and a rear side.

[0013] As if by a line with long and two short strokes in Fig. As shown in Figure 1, the vehicle is equipped with a known millimeter-wave radar device 20. The millimeter-wave radar device 20 is provided in a front part of the vehicle and emits millimeter waves forward.

[0014] The laminate 10, which is an exterior component covering the millimeter-wave radar device 20, is arranged in front of the millimeter-wave radar device 20. The laminate 10 is, for example, a grille cover that forms a front part of the vehicle exterior body.

[0015] The laminate 10 has a permeability for millimeter waves.

[0016] Next, the layer structure of the laminate 10 is described.

[0017] As in Fig. 2, the laminate 10 comprises, from the back side, in sequence a substrate 11, a primer layer 12, a color layer 13 and a protective layer 14.

[0018] The substrate 11 is made of a synthetic resin and has millimeter wave transmittance. Examples of the resin material constituting the substrate 11 include, for example, thermoplastic resins such as polypropylene (PP), polyvinyl chloride (PVC), polymethyl methacrylate resin (PMMA), acrylonitrile-butadiene-styrene copolymer (ABS) resin, acrylonitrile-ethylene-propylene-diene-styrene (AES) resin, acrylonitrile-styrene-acrylate copolymer (ASA) resin, and polycarbonate (PC). The substrate 11 of the present embodiment is made of polycarbonate.

[0019] The primer layer 12 improves the adhesion of the ink layer 13 to the substrate 11 and is laminated to the substrate 11. The primer layer 12 is made of a synthetic resin and has millimeter-wave transmittance. The primer layer 12 is formed from a known resin primer.

[0020] The relative dielectric constant of the primer layer 12 is preferably in the range of 3.1 to 66.

[0021] The color layer 13 is designed to provide the appearance color of the laminate 10 and is laminated on the primer layer 12. The color layer 13 is made of a synthetic resin and has millimeter wave transmittance. The color layer 13 is formed by applying a paint containing a base resin and fillers to the front surface of the primer layer 12. Examples of an application method include known application methods such as a spray coating method, a dipping method, a shower coating method, a flow coating method, and a roller coating method.

[0022] Examples of the material for the base resin include resin materials contained in a known resin paint, such as an acrylic resin-based paint, a urethane resin-based paint, a polyester resin-based paint, an epoxy resin-based paint, a melamine resin-based paint, an alkyd resin-based paint, or a phenolic resin-based paint.

[0023] The filler materials can have higher relative dielectric constants than the base resin. Examples of fillers include: glitter materials such as mica particles, frosted mica particles, and glass flakes; metallic conductive filler particles such as aluminum flakes; metal oxide-based conductive filler particles such as zinc oxide flakes; and metal-coated conductive filler particles obtained by coating the surfaces of mica or glass flakes with a metal such as aluminum or nickel.

[0024] The relative dielectric constant of the ink layer 13 is in a range from 3.1 to 66.7. The relative dielectric constant of the ink layer 13 is preferably greater than or equal to 3.5. The relative dielectric constant of the ink layer 13 is more preferably greater than or equal to 4.0.

[0025] The protective layer 14 imparts durability to the laminate 10 and is laminated to the ink layer 13. The protective layer 14 is made of a synthetic resin and has millimeter-wave permeability. The protective layer 14 is a so-called clear coating and is formed from a known resin ink for a clear coating.

[0026] The effective dielectric constant of the laminate 10 is greater than the relative dielectric constant of the substrate 11 and less than or equal to 3.0. The relative dielectric constant of the substrate 11 of the present embodiment is 2.67.

[0027] From the viewpoint of increasing the millimeter wave transmittance of the laminate 10, it is preferable to reduce the reflection attenuation of the laminate 10.

[0028] The primary factor contributing to the increased reflection attenuation of laminate 10 is considered to be the color layer 13, which has a high relative dielectric constant. Accordingly, in conventional approaches, the color layer 13 was formed using materials with a relative dielectric constant comparable to that of the substrate 11, specifically, a material with a relative dielectric constant of 3.0 or less. In such cases, however, the range of materials available for forming the color layer 13 is limited, resulting in limited flexibility in designing the appearance colors of the laminate 10.

[0029] The inventors of the present application varied the effective dielectric constant of the laminate 10 by varying only the relative dielectric constant of the ink layer 13 from the parameters of the layers constituting the laminate 10, as shown in Table 1. Based on the derived effective dielectric constant, the reflection attenuation of the laminate 10 was calculated. Furthermore, the inventors identified the range of values ​​of the relative dielectric constant for the ink layer 13 that results in a reflection attenuation of the laminate of 10 -18 dB or less, which serves as an indicator of relatively high millimeter wave transmittance.

[0030] The effective dielectric constant refers to the relative dielectric constant of the entire laminate 10, taking into account its total thickness. The effective dielectric constant is determined by a function that includes the refractive index, relative dielectric constant, and thickness of each layer, as well as the wavelength of the millimeter waves. [Table 1] Thickness of the paint layer [µm] 30 30 30 30 30 Relative dielectric constant of the color layer 3,1 4,0 10,0 20,0 66,7 Effective dielectric constant of the laminate 2,72 2,73 2,78 2,84 3,00 Reflection attenuation of the laminate [dB] -18,52 -18,93 -21,22 -25,22 -27,18

[0031] In the present embodiment, the parameters of the respective layers of the laminate 10 when deriving the effective dielectric constant and the reflection attenuation were set as follows: Thickness of substrate 11: 2.2 mm Relative dielectric constant of substrate 11: 2.67 Thickness of primer layer 12: 30 µm Relative dielectric constant of primer layer 12: 7.0 Thickness of the paint layer 13: 30 µm Thickness of protective layer 14: 30 µm Relative dielectric constant of the protective layer 14: 3.0

[0032] As shown in Table 1, when the relative dielectric constant of the ink layer 13 was in the range of 3.1 to 66.7, the effective dielectric constant of the laminate 10 was determined to be in the range of 2.72 to 3.00. In addition, the reflection loss of the laminate 10 was determined to be in the range of -27.18 dB to -18.52 dB.

[0033] An effect of the present embodiment will be described.

[0034] The inventors of the present application have found that when the effective dielectric constant of the laminate 10 is greater than the relative dielectric constant of the substrate 11 and does not exceed 3.0, the reflection attenuation of electromagnetic waves in the laminate 10 remains at -18 dB or below even when the relative dielectric constant of the ink layer 13 is in the range of 3.1 to 66.7.

[0035] The present embodiment has the following advantages.

[0036] (1) The laminate 10 has electromagnetic wave permeability and includes the substrate 11 made of a synthetic resin and an ink layer 13 laminated on the substrate 11. The relative dielectric constant of the ink layer 13 is in a range of 3.1 to 66.7. The effective dielectric constant of the laminate 10 is greater than the relative dielectric constant of the substrate 11 and less than or equal to 3.0.

[0037] With this configuration, since the effects of the above-described embodiment are achieved, the electromagnetic wave transmittance of the laminate 10 is improved while the flexibility in designing its appearance color is increased.

[0038] (2) The primer layer 12 is laminated on the substrate 11. The color layer 13 is laminated on the primer layer 12.

[0039] This configuration, in which the ink layer 13 is laminated on the primer layer 12 laminated on the substrate 11, improves the adhesion between the substrate 11 and the ink layer 13. Modifications

[0040] The above-described embodiment may be modified as follows. The above-described embodiment and the following modifications may be combined with each other as long as the combined modifications remain technically consistent with each other.

[0041] The color layer 13 may not contain any fillers.

[0042] If the adhesion between the substrate 11 and the color layer 13 can be improved, the primer layer 12 can be omitted.

[0043] Various changes in form and details may be made to the above examples without departing from the spirit and scope of the claims and their equivalents. The examples are for the purpose of description only and not of limitation. Descriptions of features of each example are intended to be applicable to similar features or aspects of other examples. Suitable results may be obtained when sequences are performed in a different order and / or when components in a described system, architecture, device, or circuit are combined differently and / or are substituted for or assisted by other components or their equivalents. The scope of the disclosure is not determined by the detailed description, but by the claims and their equivalents.All variations within the scope of the claims and their equivalents are included in the disclosure. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 4158646

[0002]

Claims

[1] Electromagnetic wave-permeable laminate (10) having a permeability to electromagnetic waves, comprising: a substrate (11) made of a synthetic resin; and a color layer (13) laminated on the substrate (11), wherein a relative dielectric constant of the color layer (13) is in a range of 3.1 to 66.7 and an effective dielectric constant of the laminate (10) is greater than a relative dielectric constant of the substrate (11) and less than or equal to 3.

0. [2] An electromagnetic wave transmitting laminate according to claim 1, wherein a primer layer (12) is laminated on the substrate (11) and the color layer (13) is laminated on the primer layer (12).

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