Antenna system, manufacturing method thereof, and design method

Abstract

This antenna system to be used for a frequency of 1GHz or higher is provided with: a laminate comprising a plurality of high-frequency transmissive layers that are in contact with each other with an interface therebetween and that allow transmission therethrough of a high-frequency; and an antenna circuit board that includes a high-frequency insulating layer, that is disposed adjacently to the outermost one of the high-frequency transmissive layers in the laminate, and that receives a high-frequency having transmitted through the laminate. When εn denotes the dielectric constant of an n-th layer (n is an integer of 1 or more) of the plurality of high-frequency transmissive layers, λ denotes the wavelength of a high-frequency entering the laminate, and Lnmin denotes the thickness of the n-th layer in the case where the intensity of a reflected wave from the laminate, obtained as the intensity of a synthetic wave of reflected waves from the obverse surface, reverse surface, and joint interfaces of the laminate, becomes a local minimum, the thickness of the n-th layer Ln is within a range of Lnmin±λ / (10√εn).

Description

Related Application

[0001] This application claims the priority of Japanese Patent Application No. 2022-005959 filed on January 18, 2022 in Japan, and the entire disclosure thereof is incorporated herein by reference and made a part of this application.

Technical Field

[0002] The present invention relates to an antenna system useful for high-frequency communication.

Background Art

[0003] Conventionally, it has been known to dispose an antenna made of conductive strips on a moving body such as an automobile, a window glass of a building, or an electronic device such as a smartphone, and use it for transmission and reception of information. In recent years, the amount of information to be transmitted has been increasing steadily, and in order to exchange a large amount of information, an antenna for transmitting and receiving high-frequency radio waves (also simply referred to as "high frequency") in a high-frequency GHz band with a high frequency is required. For example, Patent Document 1 (International Publication No. 2019 / 177144) describes an antenna unit compatible with high frequencies, in which a radiation element made of a conductive member and a waveguide member are spaced apart via a dielectric member.

[0004] Further, Patent Document 2 (International Publication No. 2021 / 112031) describes an antenna system for use at a frequency of 1 GHz or higher, which includes a first glass layer that transmits high frequencies, a low dielectric layer that has a lower relative permittivity than the first glass layer, is adjacent to the first glass layer, and transmits the high frequencies incident from the first glass layer, and a high-frequency insulating layer that is adjacent to the low dielectric layer and receives the high frequencies incident from the low dielectric layer, and an antenna circuit board.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] For antennas installed on the windows of mobile vehicles such as automobiles, it is preferable to use antennas that are as thin as possible. The antenna unit described in Patent Document 1 is said to be capable of handling high frequencies, but it is intended for use on building windows and the unit as a whole is quite thick.

[0007] Patent Document 2 describes a thin antenna system that can be applied to the window glass of a moving object, but it determines the optimal conditions based on the case where high-frequency waves are incident from the normal direction of the window glass. However, when transmitting and receiving high-frequency waves between moving objects, or between a stationary object and a moving object, the incident direction of the high-frequency waves usually changes. Similarly, in the case of electronic devices such as smartphones, the incident direction of high-frequency waves changes, just as with moving objects. Furthermore, in the case of buildings, the incident direction of high-frequency waves can also change depending on the height at which the antenna is installed.

[0008] The present invention aims to provide an antenna system that is integrated with a glass layer and has excellent transmission characteristics in the GHz band, and that can suppress the decrease in signal strength due to changes in the incident angle of high frequencies. [Means for solving the problem]

[0009] The inventors of the present invention investigated the effect of the high-frequency incidence angle on the glass layer in an antenna system having a glass layer and a low-dielectric layer, as previously disclosed in Patent Document 2. They found that when the incidence angle deviates from the normal direction, the frequency at which transmittance is maximized shifts to the higher frequency side. After investigating various conditions that can compensate for this incidence angle dependence, they found that by controlling the thickness of the low-dielectric layer within a predetermined range, high signal strength can be secured over a relatively wide incidence angle range, thus completing the present invention.

[0010] That is, the present invention can be configured in the following aspects.

[0011] 〔Aspect 1〕 An antenna system for use at a frequency of 1 GHz or higher, comprising: A laminate composed of a plurality of high-frequency transmission layers that are in contact with each other at an interface and each transmit high-frequency waves; An antenna circuit board that includes a high-frequency insulating layer, is disposed adjacent to the outermost high-frequency transmission layer of the laminate, and receives the high-frequency waves transmitted through the laminate. In the antenna system, The relative permittivity of the n-th layer (n is an integer of 1 or more, where the high-frequency transmission layer through which the high-frequency waves first pass when the high-frequency waves enter the laminate is defined as n = 1, and the same applies hereinafter) of the plurality of high-frequency transmission layers is ε n , The wavelength of the high-frequency waves incident on the laminate is λ, The thickness of the n-th layer when the intensity of the reflected waves from the front surface, back surface, and each bonding interface of the laminate is minimized, which is obtained as the intensity of the composite wave of the reflected waves from the laminate, is L nmin Then, The thickness L of the n-th layer n is L nmin ±λ / (10√ε n ), Antenna system. 〔Aspect 2〕 In the antenna system of Aspect 1, The intensity of the reflected waves from the laminate is the square As 2 of the amplitude As that satisfies the following formula (1). Antenna system.

Equation

[0012] [Aspect 3] An antenna system according to embodiment 1 or 2, wherein the intensity of the reflected wave from the laminate is determined when the angle of incidence of high frequency to the laminate is 40° to 50°. [Aspect 4] An antenna system according to embodiment 1 or 2, wherein the intensity of the reflected wave from the laminate is determined when the angle of incidence of high frequency to the laminate is 45°. [Aspect 5] In an antenna system according to any one embodiment of embodiments 1 to 4, the high-frequency transmission layer constituting the laminate comprises at least one glass layer and the glass layer It includes at least one transmittance adjusting layer made of a resin layer having a lower dielectric constant, and when the transmittance adjusting layer is the nth layer, the thickness of the transmittance adjusting layer is L nmin ±λ / (10√ε n An antenna system that falls within the range of ). [Aspect 6] An antenna system in any one of embodiments 1 to 5, which constitutes a windowpane of a vehicle or building. [Aspect 7] An antenna system according to any one of embodiments 1 to 5, for receiving radio waves while attached to a vehicle, building, or civil engineering structure.

[0013] [Aspect 8] A method for manufacturing an antenna system for use at frequencies of 1 GHz or higher, A laminate consisting of multiple high-frequency transparent layers that are in contact with each other at their interfaces and each transmits high frequencies, When manufacturing an antenna system comprising an antenna circuit board that includes a high-frequency insulating layer, is disposed adjacent to the outermost high-frequency transmitting layer of the laminate, and receives high frequencies transmitted through the laminate, The relative permittivity of the nth layer (where n is an integer of 1 or more) of the plurality of high-frequency transmitting layers is ε n , The wavelength of the high-frequency signal incident on the laminate is λ, The thickness of the n layer at which the intensity of the reflected wave from the laminate is minimized is determined as the intensity of the composite wave of reflected waves from the surface, back surface and each bonding interface of the laminate. nmin So, The thickness L of the n layers n to L nmin ±λ / (10√ε n ) within the range A method for manufacturing an antenna system.

[0014] [Aspect 9] In the method for manufacturing the antenna system according to embodiment 8, The laminate comprises a laminate precursor including at least one glass layer, and at least one transmittance adjusting layer consisting of a resin layer having a lower dielectric constant than the glass layer included in the laminate precursor. When the transmittance adjustment layer is the nth layer, the thickness of the transmittance adjustment layer is L nmin ±λ / (10√ε n Within the scope of ), the antenna circuit board is bonded to the laminated precursor via the transmittance adjustment layer. A method for manufacturing an antenna system. [Aspect 10] In a method for manufacturing an antenna system according to embodiment 8 or 9, The intensity of the reflected wave from the laminate is the square of the amplitude As that satisfies the following equation (1): 2 A method for manufacturing an antenna system.

number

[0015] [Aspect 11] A method for manufacturing an antenna system according to any of embodiments 8 to 10, wherein the intensity of the reflected wave from the laminate is determined when the incidence angle of high frequency on the laminate is 40 to 60°.

[0016] [Aspect 12] A method for designing an antenna system according to any one of embodiments 1 to 7, The thickness L of the n layers n is L nmin ±λ / (10√ε n ) so that it falls within the range A method for designing an antenna system, comprising the step of adjusting the thickness of each layer constituting the laminate.

[0017] [Aspect 13] An antenna circuit board used in an antenna system according to any of the embodiments 1 to 7.

[0018] Furthermore, any combination of at least two components disclosed in the claims and / or the specification and / or drawings is included in the present invention. In particular, any combination of two or more claims described in the claims is included in the present invention. [Effects of the Invention]

[0019] According to the present invention, in an antenna system, by providing a high-frequency antenna circuit board and providing a high-frequency transmission layer of a predetermined thickness on this antenna circuit board, high-frequency attenuation is suppressed, improving the transmission characteristics of the antenna circuit board for high frequencies over a wide incident angle range, and enabling the exchange of large amounts of information. [Brief explanation of the drawing]

[0020] This invention will be more clearly understood from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustrative and explanatory purposes only and should not be used to define the scope of this invention. The scope of this invention is defined by the accompanying claims. In the accompanying drawings, the same part number in multiple drawings indicates the same part. The drawings are not necessarily shown to a consistent scale and are exaggerated in order to illustrate the principles of the present invention. [Figure 1] This is a schematic cross-sectional view showing the configuration of an antenna system according to one embodiment of the present invention. [Figure 2] This diagram illustrates the optical path (wavepath) when high-frequency waves are incident on a laminate of glass layers and transmittance adjustment layers that constitute an antenna system. [Figure 3] This figure shows the dependence of the amount of high-frequency signal transmitted through a glass layer on the angle of incidence. [Figure 4] This figure shows how the relationship between high-frequency frequency and transmission amount changes with the thickness of the transmittance adjustment layer. [Figure 5] This graph shows the dependence of the high-frequency transmission amount (dB) on the incident angle for each case where the thickness of the transmittance adjustment layer is changed. [Figure 6A] This graph shows the thickness dependence of the reflected high-frequency radiation intensity for each case where the angle of incidence of the high-frequency radiation is varied. [Figure 6B] This is a sum of the graphs for each angle of incidence shown in Figure 6A. [Figure 7] This graph shows the results of a simulation of the transmittance of high-frequency waves passing through a laminate. [Figure 8]This is a schematic cross-sectional view showing the configuration of an antenna system according to one embodiment of the present invention. [Figure 9] This is a schematic cross-sectional view showing the configuration of an antenna system according to another embodiment. [Figure 10] This is a schematic cross-sectional view showing the configuration of an antenna system according to another embodiment. [Figure 11] This is a schematic cross-sectional view showing the configuration of an antenna system according to another embodiment. [Figure 12] This is a schematic cross-sectional view illustrating the configuration of a multilayer circuit board included in an antenna system. [Modes for carrying out the invention]

[0021] The antenna system of the present invention is an antenna system for use at frequencies of 1 GHz or higher, and comprises a laminate consisting of a plurality of high-frequency transparent layers, and an antenna circuit board disposed adjacent to the outermost high-frequency transparent layer of the laminate and for receiving high frequencies transmitted through the laminate. The laminate may include, as a high-frequency transparent layer, at least one glass layer and at least one transmittance adjusting layer (hereinafter sometimes referred to as a low-dielectric layer) having a dielectric constant lower than that of the glass layer. Here, "disposed adjacent to" means that they may be disposed in close proximity on adjacent surfaces of an object, be bonded to adjacent surfaces of an object, or be disposed in close proximity with a space between them and the object.

[0022] The laminate is formed of multiple high-frequency transparent layers joined at their interfaces. High-frequency waves incident on the laminate are reflected from the surface, back surface, and the interfaces of each layer. In this invention, the thickness of each layer is adjusted based on the condition in which the intensity of the composite wave of these reflected waves (reflection intensity) is minimized. In a laminate consisting of multiple high-frequency transparent layers, the relative permittivity of the nth layer (n is an integer of 1 or more) is set to ε n Therefore, the thickness L of the nth layer where the amplitude of the composite wave of the incident wave is minimized based on the wavelength λ of the incident wave and the angle of incidence. nmin This can be calculated. In that case, the actual thickness L of the nth layer can be calculated. n is Ln =L nmin ±λ / (10√ε n It is sufficient to control it within the range of ). In the antenna system of the present invention, at least one layer constituting the high-frequency transmission layer may be within the above thickness range, two or more layers may be within the above thickness range, or all layers constituting the high-frequency transmission layer may be within the above thickness range.

[0023] Here, if the amplitude of the composite wave of the reflected waves is As, then the reflection intensity is A. s 2 This is the result. In one preferred embodiment, amplitude A s The following equation (1) is satisfied.

number

[0024] Furthermore, if the laminate consists of, for example, N (where N is an integer greater than or equal to 2) high-frequency transparent layers, the reflected wave includes reflections from the exit surface of the laminate, so the right-hand side of equation (1) above will be accumulated over N+1 terms. In this case, for example, in an antenna system, if the high-frequency transparent layer and the antenna circuit board are in close proximity with an air layer in between, the amplitude A of the reflected wave N+1 In the formula for calculating (ε N+1 ) 1 / 2 cosθ N+1(ε0) 1 / 2 We can set cosθ = 0.

[0025] In the above antenna system, the film thickness L of the nth layer is such that the reflection intensity is minimized. nmin It is preferable to calculate the value assuming that the incident angle θ0 of the incident wave to the laminate is 40 to 70°, preferably 40 to 60°, more preferably 40 to 50°, for example, about 45° (45±2°). As a result of the inventors' investigations, it was found that the transmittance of high-frequency waves changes depending on the incident angle, and that by controlling the thickness of the high-frequency transmitting layer within a predetermined range based on the layer thickness at which the reflection intensity of high-frequency waves is minimized, and preferably by adjusting the thickness of the high-frequency transmitting layer based on the case where the high-frequency waves are incident at an angle inclined from the normal direction, it was found that sufficient transmittance can be obtained for high frequencies over a wide range of incident angles, from low to high.

[0026] In addition to the antenna system described above and below, the present invention also includes a method for manufacturing an antenna system and a method for designing an antenna system. In the method for manufacturing an antenna system, the material and thickness of each layer should be selected to satisfy the above relationship according to the wavelength of the high frequency used. In the method for designing an antenna system, the thickness, or material and thickness of each layer should be set to satisfy the above relationship according to the wavelength of the high frequency used. In this case, if other layers have a predetermined thickness and material (relative permittivity), the transmittance adjustment layer may be used to adjust them to satisfy the above conditions. For example, the antenna system may be one in which an antenna circuit board is bonded to an existing laminated precursor (for example, a single-layer glass plate or laminated glass consisting of two glass plates and an interlayer) via a transmittance adjustment layer. In that case, the material and thickness of the transmittance adjustment layer should be determined according to the structure and material of the existing laminated precursor. For example, Description Using equation (1), the relationship between the amplitude As of the composite wave and the thickness of the transmittance adjustment layer as the nth layer can be graphed, L nmin The value of can be calculated.

[0027] The following describes the incident angle dependence of high-frequency (high-frequency radio wave) signals received by the antenna system and the method of compensating for it, with reference to the drawings. Note that the following drawings are schematic diagrams for illustrative purposes, and the sizes of each part do not reflect the actual size ratios. Common components in different drawings are denoted by the same reference numerals, and their explanations are omitted.

[0028] Figure 1 is a schematic cross-sectional view illustrating an antenna system 1 according to one embodiment of the present invention. The antenna system 1 comprises a glass layer (first glass layer) 10, a transmittance adjustment layer 20 having a dielectric constant lower than that of the glass layer 10, and an antenna circuit board 30. The transmittance adjustment layer 20 is disposed between the glass layer 10 and the antenna circuit board 30 in the thickness direction (vertical direction in the figure), and is bonded to the glass layer 10 on one side and to the antenna circuit board 30 on the other side. The transmittance adjustment layer 20 has a relative permittance ε2 that is lower than the relative permittance ε1 of the glass layer 10.

[0029] The antenna circuit board 30 comprises a circuit layer 30a, a high-frequency insulating layer 30b, and a conductor layer 30c. The antenna circuit board 30 may also be a multilayer circuit board having multiple circuit layers and multiple insulating layers, as described later. In the configuration of Figure 1, the conductor layer 30c may have a circuit pattern as needed. In the configuration shown in Figure 1, the thickness of the transmittance adjustment layer 20 discussed below can be considered as the distance from the interface between the glass layer 10 and the transmittance adjustment layer 20 to the interface between the transmittance adjustment layer 20 and the high-frequency insulating layer 30b.

[0030] Figure 2 illustrates the dependence of high-frequency waves transmitted through a laminate 2 consisting of a glass layer 10 and a transmittance adjustment layer 20 on the incident angle. An incident wave WI, incident on the laminate from the outside (upper side of the figure) at an incident angle θ0 with the normal direction being 0 degrees, is partially reflected as a first reflected wave WR1, and partially refracted at a refraction angle θ1 with the normal direction being 0 degrees, and propagates through the glass layer 10. This high-frequency wave is then partially reflected at the interface between the glass layer 10 and the transmittance adjustment layer 20, and is emitted from the surface of the glass layer 10 as a second reflected wave WR2. On the other hand, a high-frequency wave incident in the transmittance adjustment layer 20 at a refraction angle θ2 is partially emitted from the transmittance adjustment layer 20 as a transmitted wave WT, and the other part is reflected at the surface of the transmittance adjustment layer 20 (in the embodiment of Figure 1, the interface between the transmittance adjustment layer 2 and the antenna circuit board 3), and is emitted from the surface of the glass layer 10 as a third reflected wave WR3.

[0031] Figure 3 is a graph showing the dependence of high-frequency transmission through a glass layer 10 made of inorganic glass on the incident angle. The graph was derived assuming a glass thickness of 2 mm and a relative permittivity ε1 = 6.5. For example, focusing on an incident wave frequency of 28 GHz (period N = 1), it can be seen that as the incident angle increases from 0 degrees to 80 degrees, the frequency at which transmission is maximum shifts to the higher frequency side. In other words, when using a high frequency at which transmission is maximum when incident from the normal direction to the glass layer 10 (incident angle 0 degrees), as the incident angle increases, transmission decreases, and the signal strength received by the antenna decreases, as indicated by the arrows in the figure. Note that the multilayer plate reflection transmission coefficient (1D) simulator RT1D Ver.1.2.0 was used to derive the graphs in Figure 3 and Figures 4 and 5 below.

[0032] Figure 4 is a graph showing how the amount of high-frequency radiation transmitted through a laminate consisting of a glass layer 10 and a transmittance adjustment layer 20 changes depending on the thickness of the transmittance adjustment layer 20. The graph was derived with a glass layer 10 thickness of 2 mm, relative permittivity ε1 = 6.5, relative permittivity of the transmittance adjustment layer 20 ε2 = 2.7, and an incident angle of 0 degrees. Compared to the case where the transmittance adjustment layer 20 thickness is 0 mm (shown by the solid line), when the transmittance adjustment layer 20 thickness is 0.7 mm (shown by the dotted line), the frequency at which the transmission amount is maximum (maximum transmittance) is shifted to the lower frequency side.

[0033] From the comparison of the items shown in Figures 3 and 4, it can be seen that the change in the frequency of the transmitted wave WT due to the change in the incident angle θ of the high frequency can be compensated by adjusting the thickness L2 of the transmittance adjustment layer 20. Based on this viewpoint, the present invention sought conditions under which high transmittance can be obtained over a relatively wide range of incident angles.

[0034] Figure 5 is a graph showing the dependence of the high-frequency transmittance (dB) on the incident angle for each thickness L2 of the transmittance adjustment layer 20 when a 28 GHz high frequency is incident on the laminate of the glass layer 10 and the transmittance adjustment layer 20. The optimal values ​​for the thickness L2 of the transmittance adjustment layer 20 are 1.8 mm when the incident angle θ0 is 0°, 2.2 mm when it is 45°, and 2.4 mm when it is 60°. Furthermore, the graphs from Figure 5 to Figure 7 below are derived under the following conditions. Incident wave WI: frequency f=28GHz, wavelength λ=10.7mm, wave speed c=3.0×10 8 m / s Glass layer 10: Thickness L1 = 3 mm, relative permittivity ε1 = 6.5 (√ε1 = 2.55) Transmittance adjustment layer 20: relative permittivity ε2=2.7(√ε2=1.64) The relative permittivity of air ε0 = 1.0

[0035] Furthermore, according to equation (1) above, the optimal value for the thickness L2 of the transmittance adjustment layer 20 can be calculated without using an expensive simulator. Returning to Figure 2, if the wavelength of the high-frequency waves incident on the laminate 2 is λ, then the amplitudes A1 of the first reflected wave WR1, A2 of the second reflected wave WR2, and A3 of the third reflected wave WR3 are given by the general equation (1) shown above, respectively. It can be calculated as follows. A1=((ε0) 1 / 2 cosθ0-(ε1) 1 / 2 cosθ1) / ((ε0) 1 / 2 cosθ0+(ε1) 1 / 2 cosθ1) A2 = (((ε1) 1 / 2 cosθ1-(ε2) 1 / 2 cosθ2) / ((ε1)1 / 2 cosθ1+(ε2) 1 / 2 cosθ²))·(1-A1 2 ) A3 = (((ε2) 1 / 2 cosθ²-(ε₀) 1 / 2 cosθ3) / ((ε2) 1 / 2 cosθ² + (ε₀) 1 / 2 cosθ0))·(1-A1 2 )·(1-A2 2 ) This is the result. Furthermore, given the angle of incidence θ0, the angles of refraction θ1 and θ2 can be calculated from Snell's Law as follows. θ1 = arcsin(sinθ0 / √ε1) θ² = arcsin(sinθ₀ / √ε²)

[0036] Here, if we denote the phase differences from the incident wave for the first reflected wave WR1, the second reflected wave WR2, and the third reflected wave WR3 as Δx1, Δx2, and Δx3, respectively, then these depend on the optical path difference. Δx1=0, Δx² = 2L1(ε₀) 1 / 2 cosθ1, Δx³ = 2L⁻¹(ε₀) 1 / 2 cosθ1+2L2((ε2) 1 / 2 -(ε1) 1 / 2 The result is sinθ(1 / sinθ) / cosθ(2). At that time, the amplitude A of the composite wave of the reflected waves s , the phase shift is Δx s So, A s sin(2π(x+Δx s )λ)=ΣA n si n( 2π(x+Δx n )λ) (In this case, n=1,2,3) The intensity A of the composite wave of reflected waves s 2 This can be derived.

[0037] Figure 6A shows the reflection intensity (As) when a high frequency of 28 GHz is incident on a laminate 2 consisting of a glass layer 10 and a transmittance adjustment layer 20. 2This graph shows the following. The thickness at which the intensity of the reflected wave is minimized (optimal thickness) exists periodically. When the incident angle θ0 is 0°, the optimal value of the thickness L2 of the transmittance adjustment layer 20 in the first period is 1.8 mm, while at an incident angle of 45° it is 2.2 mm, and at 60° it is 2.4 mm. The optimal value obtained here matches the simulation results in Figure 5.

[0038] Figure 6B is a graph showing the sum of the reflection intensity at each incidence angle shown in Figure 6A. In this case, the minimum value on the graph appears when the thickness L2 of the transmittance adjustment layer 20 is around 2.2 mm, which roughly corresponds to the case of an incidence angle of 45°.

[0039] Figure 7 is a graph showing the simulation results of the high-frequency transmittance passing through laminate 2 under the same conditions. For the transmittance simulation below, the multilayer plate reflection and transmission coefficient (1D) simulator RT1D Ver.1.2.0 was used. This simulation software is available from the website below and calculates the transmittance by inputting the relative permittivity, thickness, and frequency. http: / / www.e-em.co.jp / App / RT1D.htm Comparing Figure 7 with Figures 5 and 6A, the thickness at which transmittance is maximized for each incidence angle closely matches the simulation results in Figure 5 and the calculation results in Figure 6A. Furthermore, this multilayer plate reflection and transmission coefficient (1D) simulator can also determine the maximum transmittance values ​​from the second period onward, which is advantageous in practical applications.

[0040] As can be seen from the graphs described above, when used in applications where high-frequency waves are incident from directions other than the normal, such as in automotive antennas, it is preferable to adjust the thickness of the transmittance adjustment layer 20 based on the case where the high-frequency waves are incident at an oblique angle. As can be seen from the graph in Figure 5, if the optimal thickness value for θ0 = 45° is used as the reference, it can be seen that high transmittance (low reflectance) can be achieved over a relatively wide range of incident angles. Therefore, generalizing, the thickness Ln of the nth layer should be the optimal value for an incident angle of 45°. n45 For example, L n45 ±λ / 10√ε nYou may adjust it to the range.

[0041] When antenna system 1 is incorporated into the window glass of a moving object such as an automobile, the angle of incidence of high-frequency waves may not be constant. Also, when high-frequency communication is performed between fixed objects such as the window glass of a building and a mobile phone base station, it is not very practical to adjust the thickness of the high-frequency transmission layer for each building on which the antenna system is installed. Therefore, in this invention, the thickness of the high-frequency transmission layer is adjusted based on the thickness at which the transmittance is maximized when high-frequency waves are incident from a predetermined inclination angle.

[0042] Looking at Figure 5, we can see that the transmittance when L2 = 2.2 mm, which is the optimal value at an incident angle of 45°, does not differ significantly at an incident angle of 30° from the transmittance when L2 = 1.8 mm, which is the optimal value at an incident angle of 0°, and does not differ significantly at an incident angle of 55° from the transmittance when L2 = 2.4 mm, which is the optimal value at an incident angle of 60°. Furthermore, in other angle ranges, significantly higher transmittance is obtained compared to the case without transmittance adjustment layer 20 to L2 = 1.4 mm. In other words, even when the exact optimal value cannot be achieved, the effect of compensating for the incident angle dependence of high-frequency transmittance can be obtained by adjusting the thickness L2 of the transmittance adjustment layer 2. From Figure 6B, it can also be seen that it is advantageous to adjust L2 based on the optimal value at an incident angle of 45°.

[0043] In the above explanation, we described the case where the thickness L2 of the transmittance adjustment layer 20 is adjusted, but if possible, the thickness L1 of the glass layer 1 may also be adjusted. Also, although the graphs in Figures 5 to 7 describe a two-layer laminate 2, the number of high-frequency transmission layers constituting the laminate 2 is not limited to two, but may be three or more. Therefore, to generalize, the thickness L of the nth high-frequency layer constituting the laminate is n The optimal value for an incident angle of 45° is L n45 For example, L n45 ±λ / 10√ε n You may adjust it to the range.

[0044] [Antenna System Embodiments] Figures 8 to 11 are schematic cross-sectional views illustrating embodiments of the antenna system. Note that, for simplicity, the laminated structure within the antenna circuit board 30 is omitted from these figures. An antenna system 1 according to one embodiment of the present invention may have the configuration shown in Figure 1, or it may be attached directly to the surface of a substrate 40 such as glass or resin, or via an adhesive layer 50, as shown in Figure 8. Alternatively, as shown in Figure 9, the antenna system 1 of the present invention may be embedded in laminated glass 3 consisting of a surface glass layer 11, an interlayer 21, and a back glass layer 12. In this case, the surface glass layer 11 may be used as the first glass layer 10 of the antenna system 1.

[0045] The interlayer 21 may be made of a different material from the transmittance adjustment layer 20, or it may be made of the same material. For example, as shown in Figure 10, the interlayer 21 (21a to 21d) of the laminated glass 3 may constitute the transmittance adjustment layer 20 of the antenna system 1. The antenna system 1 may include transmittance adjustment layers of different thicknesses and circuit boards 30 at different distances from the first glass layer 10. In the example shown in Figure 10, the interlayer of the laminated glass 3 consists of a laminate of a first interlayer 21a, a second interlayer 21b, a third interlayer 21c, and a fourth interlayer 21d, where the first interlayer 21a constitutes the transmittance adjustment layer between the first glass layer 10 and the circuit board 3a, and the first interlayer 21a and the second interlayer 21b constitute the transmittance adjustment layer between the first glass layer 10 and the circuit board 30b.

[0046] As shown in Figure 11, the circuit board 30 of the antenna system 1 may be laminated on the back of the laminated glass 3 via a transmittance adjustment layer 20. In this case, the first glass layer 10 that joins with the transmittance adjustment layer 20 in the antenna system 1 becomes the back-side glass layer 12 of the laminated glass 3. At this time, the front-side glass layer 11 and the interlayer 21 of the laminated glass 3 may also be considered as part of the antenna system 1. Even in the configuration shown in Figure 11, simulations and calculations have confirmed that by providing the transmittance adjustment layer 20 on the back side of the laminated glass 3, the decrease in transmittance dependent on the incident angle can be suppressed, and by adjusting the thickness of the transmittance adjustment layer 20 to the thickness that maximizes transmittance based on the case where the incident angle is inclined, it is possible to suppress the decrease in transmittance when the incident angle is low, while also obtaining high high-frequency transmittance when the incident angle is 40 degrees or more. In the embodiment shown in Figure 11, the surface glass layer 11, the interlayer 21, the first glass layer 10 (backside glass layer 12), and the transmittance adjustment layer 20 constitute the high-frequency transmission layer, and these are the first to fourth layers of the high-frequency transmission layer in this order.

[0047] For example, the antenna system 1 shown in Figure 11 can also be manufactured by attaching a laminate 4 of a circuit board 30 and a transmittance adjustment layer 20 to a standard laminated glass 3. Such an intermediate laminate 4 for an antenna system is also included in the present invention.

[0048] The high-frequency range targeted by the antenna system of the present invention is, for example, 1 GHz or higher, preferably 2 GHz or higher. The high-frequency range targeted by the antenna system of the present invention may be, for example, 5 to 6 GHz (e.g., 5.8 GHz), but more preferably 6 GHz or higher, and even more preferably 10 GHz or higher. Zhou The upper limit of the wavenumber is not particularly limited, but for example, it may be 400 GHz or less, preferably 300 GHz or less. As an example, the high-frequency range targeted by the antenna system of the present invention may be 10 GHz or more, 100 GHz or less, for example around 28 GHz (26 to 30 GHz, for example 28 GHz).

[0049] As illustrated in Figure 10, a single antenna system 1 may have multiple antenna circuit boards 30. In that case, the antenna system 1 may be a multiband antenna system 1 that includes a non-high frequency compatible antenna circuit board (not shown) for radio waves with frequencies below 1 GHz.

[0050] The antenna system 1 may be incorporated into, for example, the window glass of a building, or into the glass (windshield, side windows, rear windows, sunroof) of a moving object such as an automobile or train. For example, in cases where visibility is required, such as with window glass or automobile glass, it is preferable to place the antenna system circuit board 30 in a location that does not obstruct the view.

[0051] [Glass layer] The thickness L1 of the first glass layer 10 can be appropriately set according to the intended use of the object to which the first glass layer 10 is attached. For example, it may be about 0.5 to 20 mm, preferably about 1 to 15 mm, and more preferably about 1.5 to 10 mm. When the first glass layer 10 is a windowpane of a building, it may be relatively thick, but when it is the surface layer of the antenna system 1 as shown in Figure 8, it may be thin from the viewpoint of weight reduction, and the thickness L1 may be, for example, about 0.5 to 7 mm, preferably about 0.7 to 5 mm, and more preferably about 0.8 to 3 mm.

[0052] In the embodiment shown in Figure 11, the first glass layer 10 that is bonded to the transmittance adjustment layer 20 in the antenna system 1 is the back glass 12 of the laminated glass 3. The thickness of the second glass layer can also be appropriately set according to the application of the object to which the laminated glass 3 is attached, and may be, for example, about 0.5 to 20 mm, preferably about 1 to 15 mm, and more preferably about 1.5 to 10 mm.

[0053] The shape of the first glass layer 10 is not particularly limited, as long as it can transmit high frequencies and then reach the antenna circuit board via a transmittance adjustment layer. Examples include planar glass, curved glass, and other surface-like glass.

[0054] Furthermore, the materials of the first and second glass layers are not particularly limited as long as they are materials commonly used for window glass and the like, and may be various light-transmitting transparent or translucent organic glass members (e.g., acrylic members, polycarbonate members, etc.). However, from the viewpoint of weather resistance and transparency, inorganic glass members such as soda-lime glass, boric acid glass, borosilicate glass, aluminosilicate glass, and quartz glass are preferred. According to the classification by alkali component, alkali-free glass and low-alkali glass are examples. The alkali metal component content (e.g., Na2O, K2O, Li2O) of the above glass members is preferably 15% by weight or less, and more preferably 10% by weight or less.

[0055] The method for forming these glass layers can be any appropriate method depending on the shape and material of the glass. Typically, the glass components are made by melting a mixture containing main raw materials such as silica and alumina, an antifoaming agent such as Glauber's salt and antimony oxide, and a reducing agent such as carbon at a temperature of 1400°C to 1600°C, forming it into a thin sheet, and then cooling it. Examples of methods for forming thin sheets of the glass components include the slot-down draw method, the fusion method, and the float method. Glass formed into a predetermined shape such as a sheet by these methods may be thinned further or have surface irregularities added by anti-glare treatment, as needed. Furthermore, chemical polishing with a solvent such as hydrofluoric acid may be performed to improve smoothness.

[0056] The first and second glass layers may be, for example, window glass for vehicles (e.g., window glass for vehicles, trains, airplanes, ships, etc.) or window glass for buildings.

[0057] Alternatively, a second glass layer may be combined with the first glass layer, and an antenna circuit board may be placed between them. The second glass layer is generally a glass component that is placed opposite the first glass layer in the thickness direction, and the second glass layer may be made of the same material as the first glass layer or a different material.

[0058] The first and second glass layers may include colored regions, and the antenna circuit in the antenna circuit board may be located within these colored regions. The colored regions of the first and / or second glass layers may be partial (e.g., edge regions) in cases where visibility is required, such as in window glass or vehicle glass.

[0059] [Transmittance adjustment layer] Transmittance adjustment layer The (low dielectric layer) has a lower dielectric constant (relative dielectric constant) than the first glass layer and plays a role in allowing high-frequency waves incident from the first glass layer to reach the antenna circuit board. When compared at the same frequency, the low dielectric layer has a smaller dielectric constant than the first glass layer.

[0060] As for specific values, for example, at a frequency of 28 GHz, the relative permittivity εf of the low-dielectric layer may be, for example, εg-5 to εg-0.1 with respect to the relative permittivity εg of the first glass layer, preferably εg-4.5 to εg-0.5, and more preferably εg-4 to εg-1.5.

[0061] Furthermore, for measuring dielectric properties (relative permittivity and dielectric loss tangent), the microstrip line method, which allows measurement of the permittivity in the thickness direction, is preferred. In the case of isotropic materials, the dielectric properties in the planar direction, which can be measured by the Fabry-Perot method, may be used as a substitute. In this case, measurements can be performed at 28 GHz (25°C) in accordance with JIS R 1660-2 using a Fabry-Perot resonator (Model No. DPS03) manufactured by Keycom Co., Ltd. This measurement method allows for very high-precision measurements in both one direction and the direction perpendicular to it (XY direction) in the plane, and high-precision measurements are possible even for materials with low tanδ.

[0062] In one embodiment, for example, at a frequency of 28 GHz, the relative permittivity εg of the first glass layer may be 5.5 to 7.5, preferably 5.8 to 7.3, and more preferably 6.0 to 7.0, and the relative permittivity εf of the low-dielectric layer may be, for example, 2.0 to 4.0, preferably 2.2 to 3.5, and more preferably 2.4 to 3.0.

[0063] In one embodiment, for example, at a frequency of 28 GHz, the dielectric loss tangent tanδg of the first glass layer may be 0.05 or less, preferably 0.03 or less, and more preferably 0.02 or less, and the dielectric loss tangent tanδf of the low dielectric layer may be, for example, 0.05 or less, preferably 0.03 or less, and more preferably 0.01 or less.

[0064] In one embodiment, the relative permittivity and dielectric loss tangent of the second glass layer can be the same as those of the first glass layer.

[0065] In this invention, the thickness of the low dielectric layer 20 is controlled as described above. Therefore, a single low dielectric layer 20 may be used, or a laminate of two or more thin layers may be used as the low dielectric layer 20.

[0066] In one embodiment, the thickness L2 of the low dielectric layer is L 2min Within the range of ±λ / (10√ε²), it may be possible to select from a wide range of approximately 1 μm to 20.0 mm.

[0067] The low dielectric layer (transmittance adjusting layer) is not particularly limited as long as it has a predetermined dielectric constant and can be in contact with the first glass layer, and may be formed from, for example, a thermoplastic resin or thermosetting resin having a predetermined dielectric constant.

[0068] In one embodiment, it is preferable that the low dielectric layer itself is an adhesive low dielectric layer, as this allows for easy adhesion of the interface between the first glass layer and the low dielectric layer, and the interface between the low dielectric layer and the antenna circuit board. The low dielectric layer may be adhesive to the first glass layer, or it may be adhesive to the antenna circuit board, and it is preferable that it is adhesive to both.

[0069] If the low dielectric layer is thermally fusible, the low dielectric layer material may be melted to fuse the antenna circuit board and the first glass through the low dielectric layer material. Alternatively, if the solution obtained by dissolving the low dielectric layer material in a solvent is adhesive, the low dielectric layer material solution may be applied to the bonding surface of the first glass and / or the antenna circuit board to bond the antenna circuit board and the first glass through the low dielectric layer material. Furthermore, when performing fusion or bonding (hereinafter referred to as "fusion, etc."), it is preferable to do so under degassing and / or reduced pressure to prevent the mixing of air. Degassing may be performed by physically pushing air out from the bonding interface. For fusion bonding, the antenna circuit board and the low-dielectric material may be pre-fused or bonded to form a laminate, and then the laminate and the first glass may be fused under degassing and / or reduced pressure.

[0070] Examples of adhesive low-dielectric layers include polyvinyl acetal resin, olefin-vinyl carboxylate copolymer resin, ionomer resin, acrylic resin, urethane resin, polyvinyl chloride resin, fatty acid polyamide, polyester resin, silicone elastomer, epoxy resin, and polycarbonate, all of which have good affinity for glass materials such as inorganic glass and resin glass (these materials will be discussed later). When the adhesive low-dielectric layer can be bonded by heat and pressure, it is possible to suppress circuit breakage and deformation during bonding, and even if the glass substrate is curved glass such as an automobile windshield, it is possible to follow the curve and suppress foaming and peeling. Furthermore, when forming an antenna system as laminated glass with a high-frequency antenna circuit board embedded between glass substrates, lamination can be performed under general manufacturing conditions for laminated glass, thus eliminating extra steps.

[0071] (Antenna circuit board) The antenna circuit board 30 preferably includes at least one circuit layer 30a and at least one high-frequency insulating layer 30b, and its form is not particularly limited, and it can be used as various high-frequency circuit boards by known or conventional means. Figure 1 shows an antenna circuit board comprising a circuit layer 30a, a high-frequency insulating layer 30b, and a conductor layer 30c.

[0072] Furthermore, another antenna circuit board 30 may be a laminated circuit board having a plurality of circuit layers 31a (including a conductor layer 31c), a plurality of insulating layers 31b, and vias (conductive holes) 31d provided between different circuit layers 31a as needed, as shown in the schematic cross-sectional view of Figure 12.

[0073] The antenna circuit board 30 may be a circuit board (or semiconductor element mounting board) on which semiconductor elements (e.g., IC chips: not shown) are mounted. The antenna circuit board 30 can be connected to a transceiver (not shown), for example, via a conductive strip (not shown).

[0074] The antenna circuit board 30 is capable of receiving high-frequency electromagnetic waves targeted by the antenna system 1 described above. It is also preferable that the antenna circuit board 30 is capable of transmitting these high frequencies.

[0075] The circuit layer may be formed from, for example, a metal that is at least conductive, and the circuit may be formed using a known circuit processing method. The conductor forming the circuit layer may be various conductive metals, such as gold, silver, copper, iron, nickel, aluminum, or alloys thereof.

[0076] Furthermore, the antenna circuit board may include conductive layers such as a ground layer in addition to the circuit layer. The conductive layer 30c may be composed of various conductive metals, such as gold, silver, copper, iron, nickel, aluminum, or alloys thereof. The conductors constituting the circuit layer and the conductive layer may be the same or different.

[0077] The antenna circuit board may be used in various transmission lines, such as known or conventional transmission lines including coaxial lines, strip lines, microstrip lines, coplanar lines, and parallel lines, or in antennas (for example, microwave or millimeter-wave antennas). Furthermore, the circuit board may be used in an antenna device in which the antenna and transmission line are integrated.

[0078] As long as a high-frequency insulating layer is used, the antenna structure can be any known or conventional structure, such as waveguide slot antennas, horn antennas, lens antennas, chip antennas, pattern antennas, printed antennas, triplate antennas, microstrip antennas, patch antennas, and other antennas that utilize millimeter waves or microwaves. The antenna circuit board (or semiconductor element mounting board) may be used in various sensors, especially in automotive radar.

[0079] The high-frequency antenna circuit board may be capable of supporting data transmission speeds of 10 gigabits per second or more. For example, the high-frequency antenna circuit board may be a circuit board compatible with 5G and next-generation technologies.

[0080] The area of ​​the antenna circuit board is not limited, but for example, it could be around 5cm x 5cm or 3cm x 3cm, or 25cm in area. 2 Below, preferably 20 cm 2 More preferably 10 cm 2 The following small values ​​are also acceptable. The lower limit is not particularly limited as long as it functions as an antenna system, but for example, 1 cm. 2 It can be to a certain extent.

[0081] (High-frequency insulating layer) Antenna circuit boards are preferably equipped with a high-frequency insulating layer. The high-frequency insulating layer is not particularly limited as long as it is an insulating layer that can reduce the transmission loss of electrical signals in high-frequency circuits, but examples include insulating layers composed of heat-resistant resins such as thermoplastic liquid crystal polymer (LCP), polyimide (PI) (especially modified polyimide (MPI)), polyethylene naphthalate (PEN), and polyether ether ketone (PEEK). Among these, insulating layers composed of polyimide are preferably used because they have excellent heat resistance and chemical resistance. Furthermore, thermoplastic liquid crystal polymers are preferably used because they have excellent dielectric properties.

[0082] For example, the insulating layer may be formed from a thermoplastic liquid crystal polymer film or a polyimide film. In this case, an antenna circuit board can be obtained by arranging a circuit layer on the thermoplastic liquid crystal polymer film or polyimide film. The material of the high-frequency insulating layer will be described later.

[0083] The thickness of the insulating layer 30b in the antenna circuit board 30 can be appropriately set according to the required antenna performance, etc. For example, it can be selected from a wide range of 10 μm to 2.5 mm, for example, it may be about 0.1 to 2.5 mm, preferably about 0.3 to 2.0 mm, and more preferably about 0.3 to 1.0 mm. In the case of a multilayer circuit board, the thickness of the insulating layer refers to the total thickness of the insulating layers constituting the multilayer circuit board (or the sum of the thicknesses of all insulating layers).

[0084] The relative permittivity εp in both one direction and perpendicular to it in the plane of the high-frequency insulating layer may be 2.0 to 4.0, preferably 2.2 to 3.5, and more preferably 2.4 to 3.0, at a frequency of 28 GHz. Furthermore, the relative permittivity εf of the low dielectric layer and the relative permittivity εp of the high-frequency insulating layer may be εf / εp = 30 / 70 to 60 / 40, preferably 35 / 65 to 60 / 40, and more preferably 38 / 62 to 55 / 45.

[0085] The dielectric loss tangent tanδp in both one direction and perpendicular to it in the plane of the high-frequency insulating layer may be 0.010 or less, preferably 0.005 or less, and more preferably 0.003 or less, at a frequency of 28 GHz. Here, the dielectric properties are values ​​measured by the method described above.

[0086] [Manufacturing method for antenna systems] The antenna system can be manufactured in accordance with the method described in the example of Patent Document 2, except that the control range for the thickness of the transmittance adjustment layer 20 is different. A circuit is formed by heat-pressing copper foil onto both sides of an insulating film and then etching away a portion of the copper foil. A multilayer circuit board can be obtained by repeatedly pressing and etching the insulating film and copper foil. By laminating the antenna circuit board thus formed with a separately prepared low-dielectric film and glass, and then forming a laminate using a vacuum laminator or vacuum bag, an antenna system with the desired structure can be obtained. Specific examples of manufacturing methods will be described later.

[0087] [Material of the light transmission adjustment layer] The following describes materials that can be suitably used in the transmittance adjustment layer (low dielectric layer) 20 described above.

[0088] (Polyvinyl acetal resin) Examples of polyvinyl acetal resins include polyvinyl acetal resins produced by acetalizing vinyl alcohol-based resins such as polyvinyl alcohol or vinyl alcohol copolymers. When the low dielectric layer contains polyvinyl acetal resin, it may contain one type of polyvinyl acetal resin, or it may contain two or more polyvinyl acetal resins in which one or more of the following are different: viscosity-average degree of polymerization, degree of acetalization, amount of acetyl groups, amount of hydroxyl groups, ethylene content, molecular weight of the aldehyde used for acetalization, and chain length. When the layer contains two or more different polyvinyl acetal resins, it is preferable from the viewpoint of ease of melt molding, etc., that the two or more polyvinyl acetal resins are a mixture of two or more polyvinyl acetal resins in which one or more of the following are different: viscosity-average degree of polymerization, degree of acetalization, amount of acetyl groups, and amount of hydroxyl groups.

[0089] The polyvinyl acetal resin used in the present invention can be obtained by known or conventional methods. For example, an acetalization reaction is carried out by adding an aldehyde (or keto compound) and an acid catalyst to an aqueous solution of polyvinyl alcohol or a vinyl alcohol copolymer. Then, after filtering the reaction solution as necessary, a neutralizing agent such as an alkali is added to neutralize it, and the resin is filtered, washed with water, and dried to obtain the polyvinyl acetal resin.

[0090] Polyvinyl alcohol can be obtained by polymerizing vinyl ester compounds and then saponifying the resulting polyvinyl ester, while vinyl alcohol copolymers can be obtained by saponifying copolymers of vinyl ester compounds with other monomers.

[0091] Examples of vinyl ester compounds include aliphatic vinyl carboxylates such as vinyl acetate, 1-propenyl acetate, 1-methyl vinyl acetate, 1-butenyl acetate, 2-methyl-1-propenyl acetate, vinyl propionate, vinyl butanoate, vinyl pivalate, vinyl versaticate, vinyl pentanoate, vinyl hexanoate, vinyl octanoate, vinyl decanoate, vinyl dodecanoate, vinyl hexadecanate, and vinyl octadecanoate, and aromatic vinyl carboxylates such as vinyl benzoate. These vinyl ester compounds can be used alone or in combination. Of these vinyl ester compounds, vinyl acetate is preferred from the viewpoint of productivity.

[0092] Other monomers include, for example, α-olefins such as ethylene, propylene, n-butene, and isobutylene; acrylic acid and its salts; acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid and its salts; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, Methacrylic acid esters such as i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate; acrylamide; N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetoneacrylamide, acrylamidepropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts or its quaternary salts, N-methylol acrylate Examples include acrylamide derivatives such as lylamide and its derivatives; methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and its salts, methacrylamidepropyldimethylamine and its salts or quaternary salts, N-methylolmethacrylamide and its derivatives; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, and stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidenes such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid and their salts, esters or anhydrides; and vinylsilyl compounds such as vinyltrimethoxysilane. Other monomers can be used individually or in combination of two or more. Among these, ethylene is preferred as the other monomer.

[0093] The acid catalyst used in the acetalization reaction is not particularly limited, and both organic and inorganic acids can be used, such as acetic acid, p-toluenesulfonic acid, nitric acid, sulfuric acid, and hydrochloric acid. Among these, hydrochloric acid, sulfuric acid, and nitric acid are preferred from the viewpoint of acid strength and ease of removal during washing.

[0094] The aldehyde (or keto compound) used in the production of polyvinyl acetal resin is preferably linear, branched, or cyclic, having 1 to 10 carbon atoms, and more preferably linear or branched. This results in a corresponding linear or branched acetal side chain. Furthermore, the polyvinyl acetal resin used in the present invention may be obtained by acetalizing polyvinyl alcohol or vinyl alcohol copolymer with a mixture of multiple aldehydes (or keto compounds). The polyvinyl alcohol or vinyl alcohol copolymer may consist of only one of them, or it may be a mixture of polyvinyl alcohol and vinyl alcohol copolymer.

[0095] Examples of aldehydes include aliphatic, aromatic, and alicyclic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, valeraldehyde, isovaleraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, n-heptylaldehyde, n-octylaldehyde, 2-ethylhexylaldehyde, n-nonylaldehyde, n-decylaldehyde, benzaldehyde, and cinnamaldehyde. Among these, aliphatic unbranched aldehydes with 2 to 6 carbon atoms are preferred, and n-butyraldehyde is particularly preferred from the viewpoint of easily obtaining a polyvinyl acetal resin with a suitable fracture energy. These aldehydes can be used alone or in combination of two or more. Furthermore, polyfunctional aldehydes and other aldehydes having functional groups may be used in combination in a range of 20% by mass or less of the total aldehydes. When n-butyraldehyde is used, the content of n-butyraldehyde in the aldehyde used for acetalization is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 95% by mass or more, particularly preferably 99% by mass or more, and may also be 100% by mass.

[0096] The viscosity-average degree of polymerization of the polyvinyl alcohol used as a raw material for the polyvinyl acetal resin is preferably 100 or higher, more preferably 300 or higher, even more preferably 400 or higher, even more preferably 600 or higher, particularly preferably 700 or higher, and most preferably 750 or higher. When using a polyvinyl acetal resin composition containing a larger amount of plasticizer (for example, 20 parts by mass or more), the viscosity-average degree of polymerization of the polyvinyl alcohol used as a raw material for the polyvinyl acetal resin is preferably 500 or higher, more preferably 900 or higher, even more preferably 1000 or higher, even more preferably 1200 or higher, particularly preferably 1500 or higher, and most preferably 1600 or higher. Furthermore, the viscosity-average degree of polymerization of the polyvinyl alcohol is preferably 5000 or less, more preferably 3000 or less, even more preferably 2500 or less, particularly preferably 2300 or less, and most preferably 2000 or less. The viscosity-average degree of polymerization of polyvinyl alcohol can be measured, for example, based on JIS K 6726 "Test Method for Polyvinyl Alcohol".

[0097] Typically, the viscosity-average degree of polymerization of polyvinyl acetal resin matches that of the polyvinyl alcohol used as a raw material. Therefore, the preferred viscosity-average degree of polymerization of the polyvinyl alcohol matches the preferred viscosity-average degree of polymerization of the polyvinyl acetal resin. When two or more polyvinyl acetal resins with different low-dielectric layers are included, it is preferable that the viscosity-average degree of polymerization of at least one of the polyvinyl acetal resins is above the lower limit and below the upper limit.

[0098] The amount of acetyl groups in the polyvinyl acetal resin constituting the low dielectric layer may be preferably 0.01 to 20% by mass, more preferably 0.05 to 10% by mass, and even more preferably 0.1 to 5% by mass, based on the ethylene units of the polyvinyl acetal main chain. The amount of acetyl groups in the polyvinyl acetal resin can be adjusted by appropriately adjusting the degree of saponification of the raw material polyvinyl alcohol or vinyl alcohol copolymer. When the low dielectric layer contains two or more polyvinyl acetal resins with different properties, it is preferable that the amount of acetyl groups in at least one of the polyvinyl acetal resins is within the above range.

[0099] The degree of acetalization of the polyvinyl acetal resin used in the present invention is not particularly limited, but is preferably 40 to 86 mol%, more preferably 45 to 82 mol%, even more preferably 50 to 78 mol%, particularly preferably 60 to 74 mol%, and most preferably 68 to 74 mol%. The degree of acetalization of the polyvinyl acetal resin can be adjusted to the above range by appropriately adjusting the amount of aldehyde used when acetalizing the polyvinyl alcohol resin. When the degree of acetalization is within the above range, the compatibility between the polyvinyl acetal resin and the plasticizer is less likely to decrease. When two or more polyvinyl acetal resins with different low dielectric layers are included, it is preferable that the degree of acetalization of at least one of the polyvinyl acetal resins is within the above range.

[0100] The amount of hydroxyl groups in the polyvinyl acetal resin is preferably 6 to 26% by mass, more preferably 12 to 24% by mass, more preferably 15 to 22% by mass, and particularly preferably 18 to 21% by mass, based on the ethylene units of the polyvinyl acetal main chain. The amount of hydroxyl groups can be adjusted within the above range by adjusting the amount of aldehyde used when acetalizing the polyvinyl alcohol resin. When two or more polyvinyl acetal resins with different low dielectric layers are included, it is preferable that the amount of hydroxyl groups in at least one of the polyvinyl acetal resins is within the above range.

[0101] Polyvinyl acetal resin is typically composed of acetal group units, hydroxyl group units, and acetyl group units. The amount of each of these units can be measured, for example, by JIS K 6728 "Test Method for Polyvinyl Butyral" or by nuclear magnetic resonance (NMR). If the polyvinyl acetal resin contains units other than acetal group units, the amount of hydroxyl group units and acetyl group units can be measured, and the amount of acetal group units can be calculated by subtracting these two amounts from the amount of acetal group units that would be present if the resin did not contain any other units.

[0102] The low dielectric layer preferably contains uncrosslinked polyvinyl acetal from the viewpoint of easily obtaining good film-forming properties, but it can also contain crosslinked polyvinyl acetal. For example, as a method of crosslinking, the polyvinyl acetal may be crosslinked by thermal self-crosslinking with carboxyl group-containing polyvinyl acetal, or by intermolecular crosslinking with polyaldehyde, glyoxylic acid, etc.

[0103] The viscosity of the polyvinyl acetal resin can be appropriately set depending on the type used. For example, when forming a thin low-dielectric layer, the viscosity of a 10% by mass toluene / ethanol = 1 / 1 (mass ratio) solution, measured at 20°C and 30 rpm using a Brookfield (Type B) viscometer, may be 100 to 1000 mPa·s, preferably 120 to 800 mPa·s, more preferably 150 to 600 mPa·s, even more preferably 180 to 500 mPa·s, and particularly preferably 200 to 400 mPa·s. By using a polyvinyl acetal resin having a viscosity within the above range, it is easier to set the heating temperature or heating time within the desired range when bonding to a glass substrate by heat and pressure, and it is possible to reduce the amount of unmelted polyvinyl acetal resin remaining. Furthermore, it is possible to suppress displacement of the antenna circuit board even when the antenna system is exposed to high temperatures. The viscosity of a polyvinyl acetal resin can be adjusted by using or combining a polyvinyl acetal resin manufactured using a polyvinyl alcohol-based resin with a high or low viscosity-average degree of polymerization as a raw material or as part of a raw material. If the polyvinyl acetal resin used to constitute the low dielectric layer consists of a mixture of multiple resins, the viscosity is the viscosity of such a mixture.

[0104] Furthermore, the polyvinyl acetal resin may be combined with known or conventional plasticizers as needed. Examples of plasticizers include the following. These plasticizers may be used individually or in combination of two or more. For example, a low dielectric layer may be formed as a plasticized polyvinyl acetal resin composition composed of a plasticizer and polyvinyl acetal resin.

[0105] Examples of plasticizers that can be used include those listed below. • Esters of polyvalent aliphatic or aromatic acids. Examples include dialkyl adipates (e.g., dihexyl adipate, di-2-ethylbutyl adipate, dioctyl adipate, di-2-ethylhexyl adipate, hexylcyclohexyl adipate, mixtures of heptyl adipate and nonyl adipate, diisononyl adipate, heptylnonyl adipate); esters of adipic acid with alcohols containing alicyclic ester alcohols or ether compounds (e.g., di(butoxyethyl) adipate, di(butoxyethoxyethyl) adipate); dialkyl sebacates (e.g., dibutyl sebacate); esters of sebatic acid with alcohols containing alicyclic or ether compounds; esters of phthalic acid (e.g., butyl benzyl phthalate, bis-2-butoxyethyl phthalate); and esters of alicyclic polycarboxylic acids with aliphatic alcohols (e.g., 1,2-cyclohexanedicarboxylic acid diisononyl ester).

[0106] • Esters or ethers of polyhydric aliphatic or aromatic alcohols or oligoether glycols having one or more aliphatic or aromatic substituents. Examples include esters of glycerin, diglycol, triglycol, tetraglycol, etc., with linear or branched aliphatic or alicyclic carboxylic acids. Specifically, examples include diethylene glycol-bis-(2-ethylhexanoate), triethylene glycol-bis-(2-ethylhexanoate), triethylene glycol-bis-(2-ethylbutanoate), tetraethylene glycol-bis-n-heptanoate, triethylene glycol-bis-n-heptanoate, triethylene glycol-bis-n-hexanoate, tetraethylene glycol dimethyl ether, and dipropylene glycol benzoate. • Phosphate esters of aliphatic or aromatic ester alcohols. Examples include tris(2-ethylhexyl) phosphate (TOF), triethyl phosphate, diphenyl-2-ethylhexyl phosphate, and tricresyl phosphate. • Esters of citric acid, succinic acid, and / or fumaric acid.

[0107] Furthermore, polyesters or oligoesters composed of polyhydric alcohols and polyhydric carboxylic acids, their terminal esterified or etherified products, polyesters or oligoesters composed of lactones or hydroxycarboxylic acids, or their terminal esterified or etherified products may be used as plasticizers.

[0108] The plasticizer content may be, for example, 0 to 40% by mass, preferably 0 to 30% by mass, more preferably 0 to 15% by mass, even more preferably 0 to 10% by mass, and even more preferably 0 to 5% by mass, relative to the total amount of polyvinyl acetal resin and plasticizer. Preferred polyvinyl acetal resins are marketed, for example, by Kuraray Co., Ltd. under the name "Mobital (trademark)," and polyvinyl acetal resin films are marketed, for example, by Kuraray Co., Ltd. under the name "Trosifol (trademark)."

[0109] Alternatively, when bonding a low-dielectric layer made of polyvinyl acetal resin to an adherend, a plasticizer may be applied to a film made of polyvinyl acetal resin to further enhance the adhesion of the polyvinyl acetal resin. The above-mentioned plasticizers can be used as such, and since they can improve the adhesion of the low-dielectric layer, triethylene glycol-bis-(2-ethylbutanoate), triethylene glycol-bis-(2-ethylhexanoate), dihexyl adipate, dibutyl sebacate, di(butoxyethyl) adipate, and di(butoxyethoxyethyl) adipate are preferred, triethylene glycol-bis-(2-ethylhexanoate), di(butoxyethyl) adipate, and di(butoxyethoxyethyl) adipate are more preferred, and di(butoxyethyl) adipate and di(butoxyethoxyethyl) adipate are particularly preferred.

[0110] (Olefin-vinyl carboxylate copolymer resin) The olefin-vinyl carboxylate copolymer resin is not particularly limited as long as it has a dielectric constant lower than that of the first glass layer. Examples of olefins include ethylene, propylene, n-butene, isobutylene, butadiene, and isoprene, and examples of vinyl carboxylates include the vinyl ester compounds exemplified in the section on polyvinyl acetal resins. Among these, an ethylene-vinyl acetate copolymer resin, in which ethylene is used as the olefin and vinyl acetate is used as the vinyl carboxylate compound, is preferred because it allows for control of the dielectric constant and has good adhesion.

[0111] The olefin-vinyl carboxylate copolymer resin may be further copolymerized with a monomer as a third component, as long as the dielectric constant can be controlled within a predetermined range. Examples of monomers as the third component include acrylic acid esters, methacrylic acid esters, acrylamide and its derivatives, methacrylamide and its derivatives, vinyl ethers, nitriles, vinyl halides, vinylidene halides, allyl compounds, unsaturated carboxylic acids and their derivatives, and vinylsilyl compounds, as described in the section on polyvinyl acetal resins. These monomers can be used individually or in combination of two or more. When copolymerizing these other monomers, it is generally preferable to use these other monomers in a proportion of less than 10 mol% relative to the vinyl carboxylate compound.

[0112] In olefin-vinyl carboxylate copolymer resins, from the viewpoint of strength, the ratio of vinyl carboxylate units to the total of olefin units is preferably less than 50 mol%, more preferably 30 mol% or less, even more preferably 20 mol% or less, and particularly preferably 15 mol% or less. The lower limit of vinyl carboxylate is not particularly limited, but may be, for example, around 5 mol%. A preferred olefin-vinyl carboxylate copolymer resin is, for example, ethylene vinyl acetate, which is marketed by Tosoh Corporation under the name "Mersen (trademark)".

[0113] (Ionomer resin) Ionomer resins are not particularly limited, but examples include thermoplastic resins having constituent units derived from olefins such as ethylene and constituent units derived from α,β-unsaturated carboxylic acids, in which at least a portion of the α,β-unsaturated carboxylic acids are neutralized by metal ions. Examples of metal ions include alkali metal ions such as sodium ions; alkaline earth metal ions such as magnesium ions; and zinc ions.

[0114] In the ethylene-α,β-unsaturated carboxylic acid copolymer before neutralization by metal ions, the content of α,β-unsaturated carboxylic acid constituent units is preferably 2% by mass or more, and more preferably 5% by mass or more, based on the mass of the ethylene-α,β-unsaturated carboxylic acid copolymer. Furthermore, the content of α,β-unsaturated carboxylic acid constituent units is preferably 30% by mass or less, and more preferably 20% by mass or less.

[0115] Examples of α,β-unsaturated carboxylic acid-derived structural units in the ionomer resin include those derived from acrylic acid, methacrylic acid, maleic acid, monomethyl maleate, monoethyl maleate, and maleic anhydride, with structural units derived from acrylic acid or methacrylic acid being particularly preferred.

[0116] From the viewpoint of availability, ionomers of ethylene-acrylic acid copolymers and ionomers of ethylene-methacrylic acid copolymers are more preferred as the above-mentioned ionomer resins, and zinc ionomers of ethylene-acrylic acid copolymers, sodium ionomers of ethylene-acrylic acid copolymers, zinc ionomers of ethylene-methacrylic acid copolymers, and sodium ionomers of ethylene-methacrylic acid copolymers are particularly preferred. The ionomer resins can be used alone or in combination of two or more types. Preferred ionomer resin films are marketed, for example, by Kuraray Co., Ltd. under the name "Centriglass (trademark)".

[0117] (Acrylic resin) The acrylic resin is preferably a polymer obtained from acrylic acid ester monomers and / or methacrylic acid ester monomers. Examples of such monomers include alkyl acrylates such as methyl acrylate, ethyl acrylate, and n-propyl acrylate; modified acrylates such as glycidyl acrylate and 2-hydroxyethyl acrylate; polyfunctional acrylates such as ethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, neopentyl glycol diacrylate, and pentaerythritol triacrylate; alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, and n-propyl methacrylate; modified methacrylates such as glycidyl methacrylate and 2-hydroxyethyl methacrylate; and polyfunctional methacrylates such as ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, and pentaerythritol trimethacrylate. These monomers can be used individually or in combination of two or more.

[0118] Furthermore, copolymers of acrylic acid ester monomers and / or methacrylic acid ester monomers with unsaturated carboxylic acids such as acrylic acid and methacrylic acid; acrylamides such as N,N-dimethylacrylamide; and aromatic vinyl compounds such as styrene and α-methylstyrene can also be suitably used as acrylic resins.

[0119] A preferred acrylic resin is a liquid injection type resin, which is marketed by Shinko Glass Industry Co., Ltd. as "Three S Resin," among others.

[0120] The low dielectric layer may contain known or conventional additives as needed. Examples of additives include solvents, plasticizers, UV absorbers, antioxidants, adhesion modifiers, whitening agents or fluorescent whitening agents, stabilizers, dyes, processing aids, organic or inorganic nanoparticles, calcined silicic acid, and surfactants. Additives can be used individually or in combination of two or more. [Material of the high-frequency insulating layer]

[0121] From the viewpoint of excellent heat resistance, an insulating layer composed of polyimide (hereinafter sometimes referred to as a polyimide insulating layer) is preferred. The polyimide is not particularly limited as long as it is a polymer having imide groups in its structural units, but examples of polyimide resins include polyimide, polyamideimide, polybenzimidazole, polyimide ester, polyetherimide, and polysiloxaneimide.

[0122] Polyimides can be formed by imidizing (curing) a precursor polyamic acid. Polyamic acids can be synthesized by reacting a known diamine with a tetracarboxylic acid (including its acid anhydride) in the presence of a solvent. As the diamine, aromatic diamines, aliphatic diamines, alicyclic diamines, etc., can be used, and aromatic diamines are preferred from the viewpoint of heat resistance. Examples of aromatic diamines include 4,4'-diaminodiphenyl ether, 2'-methoxy-4,4'-diaminobenzanilide, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 4,4'-diaminobenzanilide, and 5-amino-2-(p-aminophenyl)benzoxazole. Furthermore, as tetracarboxylic acids, aromatic tetracarboxylic acids, aliphatic tetracarboxylic acids, alicyclic tetracarboxylic acids, and their acid anhydrides can be used, and aromatic tetracarboxylic acid anhydrides are preferred from the viewpoint of heat resistance. Examples of aromatic tetracarboxylic acid anhydrides include pyromellitic anhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride, and 4,4'-oxydiphthalic acid anhydride. These diamines and tetracarboxylic acids can each be used individually or in combination of two or more.

[0123] Polyimide films used in polyimide insulating layers can be manufactured, for example, by applying a solution of polyamic acid (polyimide precursor) obtained by reacting a diamine with a tetracarboxylic acid to a support, drying it to obtain a polyamic acid film, and then heat-treating it to cure (imidize) it. Known coating methods such as spin coating, comma coating, screen printing, slit coating, roll coating, knife coating, dip coating, and die coating can be used to apply the polyamic acid solution.

[0124] Various additives, fillers, etc., may be added to the polyimide film, as long as they do not impair the effects of the present invention.

[0125] Examples of polyimide films on the market include Kapton EN, Kapton H, and Kapton V (all trade names) manufactured by Toray DuPont Co., Ltd., Apical NPI (trade name) manufactured by Kaneka Corporation, and Yupirex S (trade name) manufactured by Ube Industries, Ltd.

[0126] From the viewpoint of excellent dielectric properties, an insulating layer composed of a thermoplastic liquid crystal polymer (hereinafter sometimes referred to as a thermoplastic liquid crystal polymer insulating layer) is preferred. The thermoplastic liquid crystal polymer film used in the thermoplastic liquid crystal polymer insulating layer is formed from a liquid crystalline polymer that can be melt-molded. This thermoplastic liquid crystal polymer is a polymer that can form an optically anisotropic molten phase, and its chemical composition is not particularly limited as long as it is a liquid crystalline polymer that can be melt-molded, but examples include thermoplastic liquid crystal polyester, or thermoplastic liquid crystal polyesteramide in which an amide bond has been introduced thereto.

[0127] Furthermore, the thermoplastic liquid crystal polymer may be a polymer in which an aromatic polyester or aromatic polyesteramide is further modified by introducing isocyanate-derived bonds such as imide bonds, carbonate bonds, carbodiimide bonds, or isocyanurate bonds.

[0128] Specific examples of thermoplastic liquid crystal polymers used in the present invention include known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyesteramides derived from compounds classified as (1) to (4) below and their derivatives. However, it goes without saying that there is an appropriate range for the combination of various raw material compounds in order to form a polymer that can form an optically anisotropic molten phase.

[0129] (1) Aromatic or aliphatic dihydroxy compounds (see Table 1 for representative examples) [Table 1]

[0130] (2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for representative examples) [Table 2]

[0131] (3) Aromatic hydroxycarboxylic acids (see Table 3 for representative examples) [Table 3]

[0132] (4) Aromatic diamines, aromatic hydroxyamines, or aromatic aminocarboxylic acids (see Table 4 for representative examples) [Table 4]

[0133] Typical examples of thermoplastic liquid crystal polymers obtained from these raw material compounds include copolymers having the structural units shown in Tables 5 and 6.

[0134] [Table 5]

[0135] [Table 6]

[0136] Of these copolymers, polymers containing p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid as at least a repeating unit are preferred, and in particular, (i) polymers containing repeating units of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, or (ii) copolymers containing repeating units of at least one aromatic hydroxycarboxylic acid selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, at least one aromatic diol and / or aromatic hydroxyamine, and at least one aromatic dicarboxylic acid are preferred.

[0137] For example, in polymer (i), if the thermoplastic liquid crystal polymer contains repeating units of at least p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, the molar ratio (A) / (B) of p-hydroxybenzoic acid in repeating unit (A) to 6-hydroxy-2-naphthoic acid in repeating unit (B) is preferably about 10 / 90 to 90 / 10 in the thermoplastic liquid crystal polymer, more preferably about 15 / 85 to 85 / 15, and even more preferably about 20 / 80 to 80 / 20.

[0138] Furthermore, in the case of the polymer of (ii), at least one aromatic hydroxycarboxylic acid (C) selected from the group consisting of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, at least one aromatic diol (D) selected from the group consisting of 4,4'-dihydroxybiphenyl, hydroquinone, phenylhydroquinone, and 4,4'-dihydroxydiphenyl ether, and at least one aromatic dicarb selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid The molar ratio of acid (E) to each repeating unit in the thermoplastic liquid crystal polymer may be approximately (C):(D):(E) = (30~80):(35~10):(35~10), more preferably (C):(D):(E) = (35~75):(32.5~12.5):(32.5~12.5), and even more preferably (C):(D):(E) = (40~70):(30~15):(30~15).

[0139] Furthermore, the molar ratio of repeating units derived from 6-hydroxy-2-naphthoic acid among the aromatic hydroxycarboxylic acid (C) may be, for example, 85 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more. The molar ratio of repeating units derived from 2,6-naphthalenedicarboxylic acid among the aromatic dicarboxylic acid (E) may be, for example, 85 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more.

[0140] Furthermore, the aromatic diol (D) may be repeating units (D1) and (D2) derived from two different aromatic diols selected from the group consisting of hydroquinone, 4,4'-dihydroxybiphenyl, phenylhydroquinone, and 4,4'-dihydroxydiphenyl ether, in which case the molar ratio of the two aromatic diols may be (D1) / (D2) = 23 / 77 to 77 / 23, more preferably 25 / 75 to 75 / 25, and even more preferably 30 / 70 to 70 / 30.

[0141] Furthermore, the molar ratio of repeating structural units derived from aromatic diols to repeating structural units derived from aromatic dicarboxylic acids is preferably (D) / (E) = 95 / 100 to 100 / 95. If the ratio deviates from this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

[0142] Furthermore, the ability to form an optically anisotropic molten phase as referred to in this invention can be determined, for example, by placing the sample on a hot stage, heating it in a nitrogen atmosphere, and observing the transmitted light of the sample.

[0143] Preferred thermoplastic liquid crystal polymers may have a melting point (hereinafter referred to as Tm0) in the range of 200 to 360°C, preferably in the range of 240 to 360°C, more preferably in the range of 260 to 360°C, and even more preferably in the range of 270 to 350°C. Tm0 is determined by measuring the temperature at which the main endothermic peak appears using a differential scanning calorimeter (DSC, Shimadzu Corporation). Specifically, the thermoplastic liquid crystal polymer sample is heated at a rate of 10°C / min until completely melted, the molten material is cooled to 50°C at a rate of 10°C / min, and then heated again at a rate of 10°C / min. The position of the endothermic peak that appears after this cooling is determined as the melting point of the thermoplastic liquid crystal polymer sample.

[0144] The thermoplastic liquid crystal polymer may contain thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyether ether ketone, and fluororesin, as well as various additives and fillers, to the extent that the effects of the present invention are not impaired.

[0145] Thermoplastic liquid crystal polymer films are obtained, for example, by extruding a molten mixture of the thermoplastic liquid crystal polymer. Any extrusion method can be used, but well-known methods such as the T-die method and the inflation method are industrially advantageous. In particular, with the inflation method, stress is applied not only in the machine axis direction (hereinafter abbreviated as the MD direction) of the thermoplastic liquid crystal polymer film but also in the direction perpendicular to it (hereinafter abbreviated as the TD direction), allowing for uniform stretching in both the MD and TD directions. As a result, thermoplastic liquid crystal polymer films with controlled molecular orientation and dielectric properties in the MD and TD directions can be obtained.

[0146] Furthermore, known or conventional heat treatments may be performed as needed to adjust the melting point and / or thermal expansion coefficient of the thermoplastic liquid crystal polymer film. The heat treatment conditions can be set appropriately according to the purpose. For example, the melting point (Tm) of the thermoplastic liquid crystal polymer film may be increased by heating it for several hours at a temperature of -10°C or higher than the melting point (Tm0) of the thermoplastic liquid crystal polymer (e.g., Tm0-10°C to Tm0+30°C, preferably Tm0°C to Tm0+20°C).

[0147] An antenna circuit board having a thermoplastic liquid crystal polymer insulating layer can be fabricated by providing a circuit layer and / or a conductor layer on the obtained thermoplastic liquid crystal polymer film using known or conventional methods.

[0148] The melting point (Tm) of the thermoplastic liquid crystal polymer insulating layer may be, for example, 200 to 380°C, and preferably in the range of 240 to 370°C. The melting point (Tm) of the thermoplastic liquid crystal polymer insulating layer can be obtained by observing the thermal behavior of a sample obtained from the thermoplastic liquid crystal polymer insulating layer (or thermoplastic liquid crystal polymer film) using a differential scanning calorimeter. Specifically, the position of the endothermic peak that appears when the thermoplastic liquid crystal polymer film sample is heated at a rate of 10°C / min can be determined as the melting point (Tm) of the thermoplastic liquid crystal polymer film.

[0149] The thermoplastic liquid crystal polymer insulating layer has, for example, a thermal expansion coefficient of 0 to 25 ppm / °C, and preferably a thermal expansion coefficient of about 5 to 22 ppm / °C. The thermal expansion coefficient can be determined by measuring the value between 30°C and 150°C using a thermomechanical analyzer (TMA) after heating from 25°C to 200°C at a rate of 5°C / min, cooling to 30°C at a rate of 20°C / min, and then heating again at a rate of 5°C / min. [Examples]

[0150] The following embodiments illustrate methods for carrying out the present invention, but the present invention is not limited in any way by these embodiments.

[0151] [Relative permittivity and dielectric loss tangent] For films used as low-dielectric and high-frequency insulating layers, the relative permittivity and dielectric loss tangent in the thickness direction can be measured using the microstrip line method. Furthermore, the relative permittivity and dielectric loss tangent in the planar direction can be measured at a frequency of 28 GHz (25°C) in accordance with JIS R 1660-2 using a KEYCOM Co., Ltd. Model No. DPS03 (Fabry-Perot resonator). Measurements are performed in both one direction in the plane and in directions perpendicular to it (XY directions).

[0152] [Antenna circuit board, thickness of the low dielectric layer] The thickness of the antenna circuit board can be measured using a micrometer (Mitutoyo Corporation, model 227-201-CLM-15QM). The thickness of the low-dielectric layer is measured using the film used as the low-dielectric layer. Alternatively, the thickness of the entire antenna system, as well as the thickness of the antenna circuit board and glass within the antenna system, may be measured separately, and the thickness of the low-dielectric layer may be obtained by subtracting the thickness of the antenna circuit board and glass from the total thickness of the antenna system.

[0153] [Solution viscosity of polyvinyl acetal resin] A solution is prepared by dissolving the polyvinyl acetal resin, which constitutes the polyvinyl acetal resin film, in a toluene / ethanol mixed solvent of 1 / 1 (mass ratio) to a concentration of 10% by mass. The viscosity of this solution is measured using a Brookfield type (Type B) viscometer at 20°C and a rotation speed of 30 rpm.

[0154] [Calculation of optimal layer thickness - 1] Using the multilayer reflectance and transmission coefficient (1D) simulator RT1D Ver.1.2.0, the thickness L2 of the transmittance adjustment layer at which transmittance is maximized was calculated for each case of high-frequency incidence angles of 0°, 30°, 45°, 60°, and 75° to the laminate of glass and transmittance adjustment layer, assuming a relative permittivity of 6.5 for the glass layer and a relative permittivity of 2.7 for the transmittance adjustment layer. The results are shown in Table 7.

[0155] [Table 7]

[0156] Here, since the wavelength of the high frequency is 10.7 mm, λ / 10√ε2 is 0.65 mm. For example, using the optimal value of 45° as a reference, if the glass layer is 2 mm thick, the transmittance adjustment layer thickness L2 should be adjusted to the range of 0.6 ± 0.65 mm or 4.2 ± 0.65 mm, and if the glass layer is 3 mm thick, it should be adjusted to the range of 2.1 ± 0.65 mm or 5.7 ± 0.65 mm.

[0157] [Calculation of optimal layer thickness - 2] For the cases of a frequency of 5.8 GHz and a glass thickness of 3 mm, and for the cases of a frequency of 28 GHz and a glass thickness of 3 mm, assuming a relative permittivity of 6.5 for the glass layer and 2.7 for the transmittance adjustment layer, the high-frequency incidence angles to the laminate of glass and transmittance adjustment layer are 0°, 30°, 45°, 60°, and 75°. The above formulaUsing (1), the thickness L2 at which the intensity of the reflected wave is minimized was determined. Specifically, a graph showing the thickness dependence of the reflected intensity, similar to that in Figure 6A, was created using the conditions for the case where there are two high-frequency transmission layers as described above, and the optimal value was read. The calculation results are shown in Table 8.

[0158] [Table 8]

[0159] In the case of a high frequency of 28 GHz and a glass layer thickness of 3 mm, the optimal value for the transmittance adjustment layer thickness L2, which can be determined from the minimum value of the reflectance intensity, is a value that approximates the value obtained from the transmittance simulation shown in Table 7. Here, when the frequency is 5.8 GHz, the wavelength of the high frequency is 51.7 mm, so λ / 10√ε² is 3.15 mm, and when the frequency is 28 GHz, as above, λ / 10√ε² is 0.65 mm. Therefore, the thickness of the transmittance adjustment layer may be controlled within a range of ±3.15 mm when the high frequency is 5.8 GHz and ±0.65 mm when the high frequency is 28 GHz, relative to the optimal layer thickness for an incident angle of 45° determined from the table. The optimal thickness of the high-frequency transmission layer (in this case, the transmittance adjustment layer) obtained as described above can be applied, for example, to the manufacture of the antenna system described below.

[0160] (Fabrication of antenna circuit board) Copper foil (electrolytic copper foil "H9A" manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd., 12 μm thick) is layered on both sides of a thermoplastic liquid crystal polymer film (Vecter®, manufactured by Kuraray Co., Ltd., 50 μm thick, relative permittivity in the X direction: 3.4, relative permittivity in the Y direction: 3.4, dielectric loss tangent in the X direction: 0.002, dielectric loss tangent in the Y direction: 0.002). Using a vacuum heat press, the heating plate is set to 290°C and the layers are pressed together under a pressure of 4 MPa for 15 minutes to produce a copper-clad laminate with a copper foil / thermoplastic liquid crystal polymer film / copper foil configuration. A portion of the copper foil on one side of the obtained copper-clad laminate is removed with an etching solution to form a circuit, and this operation is repeated to produce an antenna circuit board (5 cm long, 5 cm wide) with a thickness of 400 μm.

[0161] (Preparation of polyvinyl acetal resin film) Polyvinyl butyral resin 1 (hydroxyl group content 19.8% by mass, degree of acetalization 70.8 mol%, acetyl group content 1.0% by mass, resin viscosity 152 mPa·s) and polyvinyl butyral resin 2 (hydroxyl group content 20.1% by mass, degree of acetalization 70.4 mol%, acetyl group content 0.9% by mass, resin viscosity 1410 mPa·s) are blended in a mass ratio of 75:25, melt-kneaded, extruded into strands, and pelletized. The obtained pellets are melt-extruded using a single-screw extruder and a T-die to obtain a 12 mm thick polyvinyl acetal resin film with a smooth surface using a metal elastic roll (dielectric constant in the X direction: 2.5, dielectric constant in the Y direction: 2.5, dielectric loss tangent in the X direction: 0.01, dielectric loss tangent in the Y direction: 0.01, plasticizer content: 0% by mass, resin viscosity: 245 mPa·s).

[0162] (Fabrication of laminates) On a lower glass panel measuring 20 cm in height, 10 cm in width, and 3 mm in thickness, the following are stacked and fixed in this order: a Teflon® sheet with embossing on one side, the dried polyvinyl acetal resin film prepared above measuring 5 cm in height, 5 cm in width, and 12 mm in thickness, the antenna circuit board prepared above measuring 5 cm in height, 5 cm in width, and 12 mm in thickness, the Teflon® sheet with embossing on one side, and the upper glass panel measuring 5 cm in height, 5 cm in width, and 3 mm in thickness. Note that the polyvinyl acetal resin film, antenna circuit board, and upper glass panel are aligned so that they overlap each other. The Teflon® sheet adjacent to the polyvinyl acetal resin film is positioned so that its embossed surface is in contact with the polyvinyl acetal resin film. The Teflon® sheet adjacent to the antenna circuit board is positioned so that its mirror surface is in contact with the antenna circuit board. The antenna circuit board is positioned so that the side containing the circuit is in contact with the polyvinyl acetal resin film. These materials are heated under vacuum at 140°C for 15 minutes in a vacuum laminator. The upper chamber is then maintained at -10kPa (a pressure difference of approximately 90kPa with the lower chamber) for 15 minutes, then returned to atmospheric pressure. The Teflon® sheets and upper and lower glass plates are removed, and a laminate is fabricated in the following order: polyvinyl acetal resin film (transmittance adjustment layer) / circuit (circuit layer) / antenna circuit board inner layer (multilayer substrate with thermoplastic liquid crystal polymer film as an insulating layer) / copper foil (conductor layer). The thickness of the polyvinyl acetal resin film layer can be adjusted to the desired thickness by laminating and pressing multiple layers together as needed.

[0163] (Construction of an antenna system) On a lower glass panel measuring 20 cm in length, 10 cm in width, and 3 mm in thickness, with relative permittivity in both the X and Y directions of 6.5, dielectric loss tangent in both directions of 0.01, the above-mentioned laminate (5 cm in length, 5 cm in width) is placed so that the polyvinyl acetal resin film (transmittance adjustment layer) is in contact with the lower glass panel. A Teflon® sheet and an upper glass panel measuring 5 cm in length, 5 cm in width, and 3 mm in thickness are then placed and fixed in this order. The antenna circuit board is positioned in an area of ​​2 cm to 7 cm inward from the vertical edge of the lower glass panel. The laminate and the upper glass panel are aligned so that they overlap each other. These materials are heated under vacuum at 140°C for 15 minutes in a vacuum laminator. The upper chamber is then maintained at -10kPa (a pressure difference of approximately 90kPa with the lower chamber) for 15 minutes, and then returned to atmospheric pressure. The Teflon® sheet and upper glass are removed, and an antenna system is obtained in which glass (f) / polyvinyl acetal resin film (transmittance adjustment layer) / circuit (circuit layer) / antenna circuit board inner layer (multilayer substrate with thermoplastic liquid crystal polymer film as an insulating layer) / copper foil (conductor layer) are laminated in that order, with the antenna circuit board disposed on a portion of the glass. In the obtained antenna system, high-frequency waves incident on the glass can efficiently pass through the transmittance adjustment layer and reach the antenna circuit board.

[0164] In the example above, the antenna system has a laminated structure of glass (first glass layer) / polyvinyl acetal resin film (low dielectric layer) / antenna circuit board, but if necessary, an additional low dielectric layer and a second glass layer may be laminated beneath the antenna circuit board.

[0165] Instead of the transmittance adjustment layer used in the example above, a transmittance adjustment layer like the one shown below can also be used. (A) A polyvinyl acetal resin film (with dielectric constant in the X direction: 2.5, dielectric constant in the Y direction: 2.5, dielectric loss tangent in the X direction: 0.01, dielectric loss tangent in the Y direction: 0.01, plasticizer content: 0%, resin viscosity: 245mPa·s) is formed by blending polyvinyl butyral resin 1 (hydroxyl group content: 19.8% by mass, degree of acetalization: 70.8 mol%, acetyl group content: 1.0% by mass, resin viscosity: 152mPa·s) and polyvinyl butyral resin 2 (hydroxyl group content: 20.1% by mass, degree of acetalization: 70.4 mol%, acetyl group content: 0.9% by mass, resin viscosity: 1410mPa·s) in a mass ratio of 75:25 and forming the film in the same manner as described above. (B) Ionomer resin film (manufactured by Kuraray Co., Ltd., film made by heat pressing SentryGlas® SG5000 into a thin film, relative permittivity in the X direction: 2.2, relative permittivity in the Y direction: 2.2, dielectric loss tangent in the X direction: 0.002, dielectric loss tangent in the Y direction: 0.002) (C) Polyvinyl acetal film (manufactured by Kuraray Co., Ltd., V200KE, thickness 700 μm, relative permittivity in the X direction: 2.7, relative permittivity in the Y direction: 2.7, dielectric loss tangent in the X direction: 0.02, dielectric loss tangent in the Y direction: 0.02)

[0166] The insulating layer shown below can be used instead of the insulating layer used in the example above. Polyimide film (manufactured by Toray DuPont Co., Ltd., Kapton 300H, thickness 75 μm, relative permittivity in the X direction: 3.3, relative permittivity in the Y direction: 3.3, dielectric loss tangent in the X direction: 0.007, dielectric loss tangent in the Y direction: 0.007). Polyimide film (manufactured by Kaneka Corporation, Apical NPI, thickness 50 μm, relative permittivity in the X direction: 3.4, relative permittivity in the Y direction: 3.4, dielectric loss tangent in the X direction: 0.004, dielectric loss tangent in the Y direction: 0.004).

[0167] In the example above, the glass layer is formed from glass with a dielectric constant of 6.5, but organic glass such as acrylic glass or polycarbonate may also be used.

[0168] In the example above, a laminator is used to laminate each layer, but the laminated material may also be placed in a vacuum bag, preheated, and then subjected to heating and pressurizing treatment. For example, as a specific example of conditions, the laminated material may be placed in a vacuum bag, depressurized at room temperature for 15 minutes, then heated to 100°C while maintaining the depressurized state and held for 30 minutes, after which it may be cooled, the depressurization released, and the material temporarily bonded, before being placed in an autoclave and treated at 140°C and 12 MPa for 30 minutes.

[0169] Alternatively, the antenna system may be fabricated by applying triethylene glycol-di-(2-ethylhexanoate) or dibutoxyethyl adipate to the low-dielectric layer of the laminate for the antenna system, bonding it to glass, and then drying it with hot air. [Industrial applicability]

[0170] The antenna system of the present invention suppresses high-frequency attenuation, improving the transmission characteristics of the antenna circuit board for high frequencies and enabling the exchange of large amounts of information. Therefore, it can be usefully used as an antenna system for vehicles such as connected cars, which are used for autonomous driving and continuous communication by in-vehicle devices, or as an antenna system for small cell base stations by installing it on windows and walls of buildings, various civil engineering structures (railway facilities, road facilities, energy facilities, dams and river facilities, water and sewage facilities, airport facilities), etc. For example, the antenna system of the present invention can be used by forming it on the window glass of a vehicle or building, or by attaching it to a vehicle or building. The antenna system of the present invention can also be installed on electronic devices such as display devices. Examples of display devices include large-screen televisions, monitors, tablets, smartphones, laptop computers, desktop computers, personal digital assistants, or other display devices. The antenna system of the present invention can also be installed on the back glass of a smartphone, for example.

[0171] As described above with reference to the drawings, preferred embodiments of the present invention have been explained. However, those skilled in the art will readily anticipate various changes and modifications within the obvious scope by reviewing this specification. Therefore, such changes and modifications will be interpreted as falling within the scope of the invention as defined by the claims. [Explanation of symbols]

[0172] Antenna system 1 Laminate 2 Laminated glass 3 4 laminates for antenna systems First glass layer 10, 11 Transmittance adjustment layer (low dielectric layer) 20 Intermediate film 21, 21a~21d Antenna circuit boards 30, 31 Circuit layer 30a, 31a High-frequency insulating layers 30b, 31b Conductor layers 30c, 31c via 31d Base 40 Adhesive layer 50

Claims

1. An antenna system for use at frequencies of 1 GHz or higher, A laminate consisting of multiple high-frequency transparent layers that are in contact with each other at their interfaces and each transmits high frequencies, An antenna system comprising an antenna circuit board that includes a high-frequency insulating layer, is disposed adjacent to the outermost high-frequency transmitting layer of the laminate, and receives high frequencies transmitted through the laminate, The relative permittivity of the nth layer of the plurality of high-frequency transparent layers (where n is an integer of 1 or more, and the first high-frequency transparent layer through which high-frequency waves are transmitted when high-frequency waves are incident on the laminate is defined as n=1, and so on) is ε ｎ , The wavelength of the high-frequency signal incident on the laminate is λ, The thickness of the n layers is determined as the intensity of the composite wave of reflected waves from the surface, back surface and each bonding interface of the laminate, such that the intensity of the reflected wave from the laminate is calculated to be minimal. ｎｍｉｎ So, The thickness L of the n layers ｎ is L ｎmin ±λ / (10√ε) ｎ ) within the range In antenna systems, An antenna system in which the intensity of the reflected wave from the laminate is determined as the square of the amplitude As² satisfying the following equation (1), for the case where the angle of incidence of high frequency to the laminate is 40 to 50°. [Math 1] Here, εn is the relative permittivity of the nth layer constituting the laminate. Ln is the thickness of the nth layer that makes up the laminate. θn is the refraction angle of high-frequency light incident on the nth layer constituting the laminate. λ is the wavelength of the high-frequency radio waves incident on the laminate in air. ε₀ is the relative permittivity in air. n is an integer greater than or equal to 1. This represents, A 0 = 0, Δx 0 = 0, L 0 = 0, θ 0 = The angle of incidence of high-frequency radiation incident on the laminate (the first layer of the laminate).

2. An antenna system according to claim 1, wherein the intensity of the reflected wave from the laminate is determined when the angle of incidence of high frequency to the laminate is 45°.

3. In the antenna system according to claim 1 or 2, the high-frequency transmission layer constituting the laminate includes at least one glass layer and at least one transmittance adjustment layer made of a resin layer having a lower dielectric constant than the glass layer, and when the transmittance adjustment layer is the nth layer, the thickness of the transmittance adjustment layer is the L ｎmin ±λ / (10√ε) ｎ An antenna system that falls within the range of ).

4. An antenna system according to claim 1 or 2, comprising a display device or a windowpane of a vehicle or building.

5. An antenna system according to claim 1 or 2, for receiving radio waves while attached to a vehicle, building or civil engineering structure.

6. A method for manufacturing an antenna system for use at frequencies of 1 GHz or higher, A laminate consisting of multiple high-frequency transparent layers that are in contact with each other at their interfaces and each transmits high frequencies, When manufacturing an antenna system comprising an antenna circuit board that includes a high-frequency insulating layer, is disposed adjacent to the outermost high-frequency transmitting layer of the laminate, and receives high frequencies transmitted through the laminate, The relative permittivity of the nth layer (where n is an integer of 1 or more) of the plurality of high-frequency transparent layers is ε ｎ , The wavelength of the high-frequency signal incident on the laminate is λ, The thickness L of the n-th layer when the intensity of the reflected wave from the laminate becomes computationally minimal, which is obtained as the intensity of the combined wave of the reflected waves from the front surface, back surface, and each bonding interface of the laminate ｎｍｉｎ If it is assumed to be The thickness L of the n layers ｎ to L ｎmin ±λ / (10√ε) ｎ ) within the range In a method for manufacturing an antenna system, A method for manufacturing an antenna system, wherein the intensity of the reflected wave from the laminate is determined as the square of the amplitude As² satisfying the following equation (1), for the case where the incidence angle of high frequency on the laminate is 40 to 50°. [Math 2] Here, εn is the relative permittivity of the nth layer constituting the laminate. Ln is the thickness of the nth layer that makes up the laminate. θn is the refraction angle of high-frequency light incident on the nth layer constituting the laminate. λ is the wavelength of the high-frequency radio waves incident on the laminate in air. ε₀ is the relative permittivity in air. n is an integer greater than or equal to 1. This represents, A 0 = 0, Δx 0 = 0, L 0 = 0, θ 0 = The angle of incidence of high-frequency radiation incident on the laminate (the first layer of the laminate).

7. A method for manufacturing the antenna system according to claim 6, The laminate includes a laminate precursor comprising at least one glass layer and at least one transmittance adjusting layer comprising a resin layer having a lower dielectric constant than the glass layer comprising the laminate precursor. When the transmittance adjustment layer is the nth layer, the thickness of the transmittance adjustment layer is L ｎmin ±λ / (10√ε) ｎ Within the scope of ), the antenna circuit board is bonded to the laminated precursor via the transmittance adjustment layer. A method for manufacturing an antenna system.

8. A method for designing an antenna system according to claim 1 or 2, The thickness L of the n layers ｎ is L ｎmin ±λ / (10√ε) ｎ ) so that it falls within the range A method for designing an antenna system, comprising the step of adjusting the thickness of each layer constituting the laminate.

9. An antenna circuit board used in the antenna system according to claim 1 or 2.

Images