Antenna system, and manufacturing method and design method for same

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

Antenna system and manufacturing and design methods thereof Related Applications

[0001] This application claims priority to Japanese Patent Application No. 2022-005959, filed on January 18, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to antenna systems useful for communication at radio frequencies.

[0003] It has been known for some time that antennas made of conductive wires are installed on mobile objects such as automobiles, windowpanes of buildings, and electronic devices such as smartphones to transmit and receive information. In recent years, the amount of information transmitted has been steadily increasing, and in order to exchange large amounts of information, antennas that transmit and receive high-frequency radio waves (also simply referred to as "high frequency") in the GHz band with high frequencies are required. For example, Patent Document 1 (International Publication No. 2019 / 177144) describes a high-frequency antenna unit having a configuration in which a radiating element made of a conductive material and a waveguide member are spaced apart via a dielectric member.

[0004] Furthermore, Patent Document 2 (WO 2021 / 112031) describes an antenna system for use at frequencies of 1 GHz or higher, which is composed of a first glass layer that transmits high frequencies, a low dielectric layer that has a lower dielectric constant than the first glass layer and is adjacent to the first glass layer and transmits high frequencies incident from the first glass layer, and an antenna circuit board that includes a high-frequency insulating layer that is adjacent to the low dielectric layer and receives high frequencies incident from the low dielectric layer.

[0005] International Publication No. 2019 / 177144 International Publication No. 2021 / 112031

[0006] It is preferable that an antenna be as thin as possible when it is to be installed on the window glass of a moving object such as an automobile. The antenna unit described in Patent Document 1 is said to be compatible with high frequencies, but it is used for the window glass of a building, and the entire unit is quite thick.

[0007] Patent Document 2 describes a thin antenna system that can be applied to the window glass of a mobile body, but 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 mobile bodies or between a fixed body and a mobile body, the incident direction of high frequency waves usually changes. In addition, in the case of electronic devices such as smartphones, the incident direction of high frequency waves changes, just like in mobile bodies. In addition, in the case of buildings, the incident direction of high frequency waves can 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, has excellent transmission characteristics in the GHz band, and can suppress a decrease in signal strength due to changes in the incident angle of high frequencies.

[0009] The inventors of the present invention have investigated the effect of the high frequency incident angle on the glass layer in the antenna system having a glass layer and a low dielectric layer previously disclosed in Patent Document 2, and found that when the incident angle deviates from the normal direction, the frequency at which the transmittance is maximized shifts to the higher frequency side. As a result of investigating various conditions that can compensate for this incident angle dependency, they have found that by controlling the thickness of the low dielectric layer within a predetermined range, high signal strength can be ensured over a relatively wide range of incident angles, and have completed the present invention.

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

[0011] [Aspect 1] An antenna system for use at frequencies of 1 GHz or higher, comprising: a laminate made up of a plurality of high-frequency transmission layers in contact with each other at their interfaces, each of which transmits high-frequency waves; and an antenna circuit board including a high-frequency insulating layer, disposed adjacent to the outermost high-frequency transmission layer of the laminate, and configured to receive high-frequency waves transmitted through the laminate; wherein the relative dielectric constant of an n-th layer (n is an integer of 1 or more, where n=1 is the high-frequency transmission layer that transmits first when high-frequency waves enter the laminate, and the same applies hereinafter) of the plurality of high-frequency transmission layers is set to ε ｎλ is the wavelength of the high frequency wave incident on the laminate, L is the thickness of the nth layer when the intensity of the reflected wave from the laminate is minimized, which is calculated as the intensity of a composite wave of reflected waves from the front surface, rear surface and each bonding interface of the laminate. ｎｍｉｎ Then, the thickness L of the nth layer ｎ L ｎmin ±λ / (10√ε ｎ The antenna system of the first aspect, wherein the intensity of the reflected wave from the laminate is within a range of a square of the amplitude As that satisfies the following formula (1): ２ That is, the antenna system. where ε ｎ is the relative dielectric constant of the nth layer constituting the laminate, L ｎ is the thickness of the nth layer constituting the laminate, θ ｎ is the refraction angle of the high frequency wave incident on the nth layer of the laminate, λ is the wavelength in air of the high frequency wave incident on the laminate, ε ０ represents the relative permittivity in air, n is an integer of 1 or more, and A ０ = 0, Δx ０ = 0, L ０ = 0, θ ０ = the angle of incidence of the high frequency wave incident on the stack (first layer of the stack).

[0012] [Aspect 3] The antenna system of Aspect 1 or 2, wherein the intensity of the reflected wave from the laminate is determined when the angle of incidence of the high frequency wave on the laminate is 40° to 50°. [Aspect 4] The antenna system of Aspect 1 or 2, wherein the intensity of the reflected wave from the laminate is determined when the angle of incidence of the high frequency wave on the laminate is 45°. [Aspect 5] The antenna system of any one of Aspects 1 to 4, wherein 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 dielectric constant lower than that of the glass, and when the transmittance adjustment layer is the n-th layer, the thickness of the transmittance adjustment layer is ｎmin ±λ / (10√ε ｎ) range. [Aspect 6] The antenna system of any one of Aspects 1 to 5, which constitutes a window glass of a vehicle or a building. [Aspect 7] The antenna system of any one of Aspects 1 to 5, which receives radio waves while attached to a vehicle, a building or a civil engineering structure.

[0013] [Aspect 8] A method for manufacturing an antenna system for use at frequencies of 1 GHz or higher, comprising: a laminate including a plurality of high-frequency transmission layers in contact with each other at their interfaces, each of which transmits high-frequency waves; and an antenna circuit board including a high-frequency insulating layer, disposed adjacent to the outermost high-frequency transmission layer of the laminate, and receiving high-frequency waves transmitted through the laminate, the method comprising the steps of: setting the relative dielectric constant of an n-th layer (n is an integer of 1 or greater) of the plurality of high-frequency transmission layers to ε ｎ λ is the wavelength of the high frequency wave incident on the laminate, L is the thickness of the nth layer when the intensity of the reflected wave from the laminate is minimized, which is calculated as the intensity of a composite wave of reflected waves from the front surface, rear surface and each bonding interface of the laminate. ｎｍｉｎ Then, the thickness L of the nth layer ｎ L ｎmin ±λ / (10√ε ｎ ) a method for manufacturing an antenna system.

[0014] [Aspect 9] In the method for manufacturing an antenna system according to Aspect 8, the laminate includes a laminate precursor including at least one glass layer, and at least one transmittance adjustment layer made of a resin layer having a relative dielectric constant lower than that of the glass layer included in the laminate precursor, and when the transmittance adjustment layer is an n-th layer, the thickness of the transmittance adjustment layer is set to be equal to or less than the L ｎｍｉｎ ±λ / (10√ε ｎ The method for manufacturing an antenna system according to the eighth or ninth aspect, wherein the intensity of the reflected wave from the laminate is within a range of a square As of the amplitude As that satisfies the following formula (1): ２ A method for manufacturing an antenna system. where εｎ is the relative dielectric constant of the nth layer constituting the laminate, L ｎ is the thickness of the nth layer constituting the laminate, θ ｎ is the refraction angle of the high frequency wave incident on the nth layer of the laminate, λ is the wavelength in air of the high frequency wave incident on the laminate, ε ０ represents the relative permittivity in air, n is an integer of 1 or more, and A ０ = 0, Δx ０ = 0, L ０ = 0, θ ０ = the angle of incidence of the high frequency wave incident on the stack (first layer of the stack).

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

[0016] [Aspect 12] A method for designing the antenna system according to any one of aspects 1 to 7, comprising: ｎ L ｎmin ±λ / (10√ε ｎ and adjusting the thickness of each layer constituting the laminate so that the thickness falls within the range of .

[0017] [Aspect 13] An antenna circuit board used in the antenna system of any one of Aspects 1 to 7.

[0018] It should be noted that any combination of at least two elements disclosed in the claims and / or the specification and / or the drawings is included in the present invention, and in particular any combination of two or more of the claims set forth in the claims is included in the present invention.

[0019] According to the present invention, in an antenna system, a high-frequency antenna circuit board is provided, and a high-frequency transmission layer of a predetermined thickness is provided on this antenna circuit board, thereby suppressing high-frequency attenuation and improving the transmission characteristics of the antenna circuit board for high frequencies over a wide range of incident angles, making it possible to exchange large amounts of information.

[0020] The present 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 merely for illustration and explanation purposes and should not be used to define the scope of the present invention. The scope of the present invention is defined by the accompanying claims. In the accompanying drawings, the same part numbers in multiple drawings indicate the same parts. The drawings are not necessarily drawn to scale and are exaggerated to illustrate the principles of the present invention. This is a schematic cross-sectional view showing the configuration of an antenna system according to one embodiment of the present invention. This is a diagram for explaining the optical path (wavepath) when a high frequency wave is incident on a laminate of a glass layer and a transmittance adjustment layer that constitutes the antenna system. This is a diagram showing the incidence angle dependence of the transmission amount of a high frequency wave that passes through a glass layer. This is a diagram showing the change in the relationship between the frequency and transmission amount of a high frequency wave depending on the thickness of the transmittance adjustment layer. This is a graph showing the incidence angle dependence of the transmission amount (dB) of a high frequency wave for each case where the thickness of the transmittance adjustment layer is changed. This is a graph showing the thickness dependence of the reflection intensity of a high frequency wave for each case where the incidence angle of the high frequency wave is changed. This is a graph showing the sum of the graphs for each incidence angle in the graph of FIG. 6A. Fig. 1 is a graph showing the results of a simulation of the transmittance of high frequency waves passing through a laminate. Fig. 2 is a schematic cross-sectional view showing the configuration of an antenna system according to an embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing the configuration of an antenna system according to another embodiment. Fig. 4 is a schematic cross-sectional view showing the configuration of an antenna system according to another embodiment. Fig. 5 is a schematic cross-sectional view showing the configuration of an antenna system according to another embodiment. Fig. 6 is a schematic cross-sectional view for illustrating the configuration of a laminated circuit board provided in the antenna system.

[0021] The antenna system of the present invention is an antenna system for use at frequencies of 1 GHz or higher, and includes a laminate consisting of multiple high-frequency transmission layers and an antenna circuit board disposed adjacent to the outermost high-frequency transmission layer of the laminate and configured to receive high frequencies transmitted through the laminate. The laminate may include, as high-frequency transmission layers, at least one glass layer and at least one transmittance adjustment layer (hereinafter also referred to as a low-dielectric layer) having a lower dielectric constant than the glass layer. Here, "disposed adjacent to" may mean closely disposed on adjacent surfaces of an object, or may mean disposed by bonding on adjacent surfaces of the object, or may mean disposed adjacent to the object with a space between them.

[0022] The laminate is formed of a plurality of high-frequency transmission layers joined at their interfaces. High-frequency waves incident on the laminate are reflected from the front surface, back surface, and interfaces of each layer. In the present invention, the thickness of each layer is adjusted based on the condition that the intensity of the composite wave of these reflected waves (reflection intensity) becomes minimum. In a laminate consisting of a plurality of high-frequency transmission layers, the relative dielectric constant of the nth layer (n is an integer of 1 or more) is set to ε ｎ Then, the thickness L of the nth layer at which the amplitude of the composite wave of the reflected wave becomes minimum from the wavelength λ of the incident wave and the incident angle is ｎｍｉｎ In this case, the actual thickness of the nth layer, L ｎ Is L ｎ =L ｎｍｉｎ ±λ / (10√ε ｎ In the antenna system of the present invention, at least one layer constituting the radio frequency transmission layer has a thickness in the above-mentioned range, two or more layers may have a thickness in the above-mentioned range, or all layers constituting the radio frequency transmission layer may have a thickness in the above-mentioned range.

[0023] Here, if the amplitude of the composite wave of the reflected waves is As, the reflection intensity is A ｓ ２ In a preferred embodiment, the amplitude A ｓ satisfies the following formula (1). where ε ｎ is the relative dielectric constant of the nth layer constituting the laminate, L ｎ is the thickness of the nth layer constituting the laminate, θ ｎis the refraction angle of the high frequency wave incident on the nth layer of the laminate (the angle of incidence from the nth layer to the (n+1)th layer), λ is the wavelength in air of the high frequency wave incident on the laminate, ε ０ represents the relative permittivity in air, n is an integer of 1 or more, and A ０ = 0, Δx ０ = 0, L ０ = 0, θ ０ = incident angle of high frequency wave incident on the laminate (first layer of the laminate)

[0024] In addition, when the laminate is made up of, for example, N high frequency transmission layers (N is an integer of 2 or more), the reflected wave also includes reflection from the emission surface of the laminate, so the right side of the above formula (1) is integrated over N+1 terms. In this case, for example, in an antenna system, when the high frequency transmission layer and the antenna circuit board are close to each other with an air layer between them, the amplitude A of the reflected wave is Ｎ＋１ In the formula for calculating (ε N+1 ) 1 / 2 cosθ N+1 is (ε0) 1 / 2 Just set it to cosθ0.

[0025] In the above antenna system, the thickness L of the n-th layer at which the reflection intensity becomes minimum ｎｍｉｎ is the incident angle θ of the incident wave on the laminate ０ is preferably 40 to 70°, preferably 40 to 60°, more preferably 40 to 50°, for example, approximately 45° (45±2°). As a result of studies by the present inventors, it has been found that the transmittance of high frequency waves varies depending on the incident angle, and that by controlling the film thickness of the high frequency transmission layer within a predetermined range based on the layer thickness at which the reflection intensity of high frequency waves is minimized, and in this case, preferably by adjusting the thickness of the high frequency transmission layer based on the case where high frequency waves are incident at an angle inclined from the normal direction, it is possible to obtain sufficient transmittance for high frequency waves over a wide range of incident angles, from low to high.

[0026] In addition to the antenna systems 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 may be selected to satisfy the above relationship depending on the wavelength of the high frequency used. In the method for designing an antenna system, the thickness of each layer, or the material and thickness thereof, may be set to satisfy the above relationship depending on the wavelength of the high frequency used. In this case, if other layers have a predetermined thickness and material (relative dielectric constant), they may be adjusted to satisfy the above condition using a transmittance adjustment layer. For example, the antenna system may be formed by bonding an antenna circuit board to an existing laminate precursor (e.g., a single-layer glass plate or a laminated glass consisting of two layers of glass plates and an interlayer) via a transmittance adjustment layer. In this case, the material and thickness of the transmittance adjustment layer may be determined according to the structure and material of the existing laminate precursor. For example, using the above formula (1), the relationship between the amplitude As of the composite wave and the thickness of the transmittance adjustment layer as the nth layer may be graphed, and L ｎｍｉｎ The value of can be calculated.

[0027] The following describes the incidence angle dependency of high frequency waves (high frequency radio waves) received by an antenna system and a method for compensating for it, with reference to the drawings. Note that the following drawings are schematic diagrams for explanatory purposes, and the sizes of the components do not reflect the actual size ratios. In different drawings, common components are assigned the same reference numerals, and their explanations will be omitted.

[0028] 1 is a schematic cross-sectional view illustrating an antenna system 1 according to one embodiment of the present invention. The antenna system 1 includes 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 (the vertical direction in the drawing), 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 dielectric constant ε 2 lower than that of the glass layer 10. １ A lower relative permittivity ε ２ It has.

[0029] The antenna circuit board 30 includes a circuit layer 30a, a high-frequency insulating layer 30b, and a conductor layer 30c. The antenna circuit board 30 may be a multilayer circuit board having multiple circuit layers and multiple insulating layers, as described below. In the configuration of FIG. 1 , the conductor layer 30c may also have a circuit pattern, if necessary. In the configuration shown in FIG. 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] 2 is a diagram illustrating the incidence angle dependency of high frequency waves transmitted through a laminate 2 consisting of a glass layer 10 and a transmittance adjusting layer 20. An incident wave WI incident on the laminate from the outside (upper side of the figure) at an incidence 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 θ0 with the normal direction being 0 degrees. １ The high frequency wave is then refracted at a refraction angle θ 2 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 adjusting layer 20, and is emitted from the surface of the glass layer 10 as a second reflected wave WR2. ２ A portion of the incident high frequency wave is emitted from the transmittance adjustment layer 20 as a transmitted wave WT, and another portion 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 emitted from the surface of the glass layer 10 as a third reflected wave WR3.

[0031] 3 is a graph showing the incidence angle dependence of the transmission amount of high frequency waves transmitted through the glass layer 10 made of inorganic glass. １The graph was derived with a ρ = 6.5. For example, when focusing on an incident wave frequency of 28 GHz (period N = 1), it can be seen that as the angle of incidence increases from 0 degrees to 80 degrees, the frequency at which the transmittance is maximized shifts toward higher frequencies. In other words, when using a high-frequency wave with a frequency at which the transmittance is maximized when incident from the normal direction of the glass layer 10 (incident angle of 0 degrees), as indicated by the arrow in the figure, as the incident angle increases, the transmittance decreases, and the signal strength received by the antenna decreases. The graphs in Figure 3 and the following Figures 4 and 5 were derived using the multilayer board reflection / transmission coefficient (1D) simulator RT1D Ver. 1.2.0.

[0032] 4 is a graph showing how the amount of high frequency transmitted through a laminate including a glass layer 10 and a transmittance adjusting layer 20 changes depending on the thickness of the transmittance adjusting layer 20. The thickness of the glass layer 10 is 2 mm, and the relative dielectric constant ε １ = 6.5, relative dielectric constant ε of the transmittance adjusting layer 20 ２ The graph was derived with a .DELTA.=2.7 and an incident angle of 0°. Compared to the case where the thickness of the transmittance adjusting layer 20 is 0 mm, as shown by the solid line, the frequency at which the transmission amount is maximum (maximum transmittance) is shifted to the lower frequency side when the thickness of the transmittance adjusting layer 20 is 0.7 mm, as shown by the dotted line.

[0033] 3 and 4, the change in the frequency of the transmitted wave WT with the change in the incident angle θ of the high frequency wave can be calculated by the thickness L of the transmittance adjusting layer 20. ２ Based on this viewpoint, the present invention seeks a condition under which high transmittance can be obtained over a relatively wide range of incident angles.

[0034] FIG. 5 shows the relationship between the thickness L of the transmittance adjusting layer 20 and the thickness L of the glass layer 10 when a high frequency of 28 GHz is incident on a laminate of the glass layer 10 and the transmittance adjusting layer 20. ２ 1 is a graph showing the incidence angle dependency of high frequency transmittance (dB) with respect to the incidence angle θ ０ The thickness L of the transmittance adjusting layer 20 is 1.8 mm when the angle is 0°, 2.2 mm when the angle is 45°, and 2.4 mm when the angle is 60°. ２The graphs in Fig. 5 to Fig. 7 are derived for the following conditions: Incident wave WI: frequency f = 28 GHz, wavelength λ = 10.7 mm, wave speed c = 3.0 × 10 ８ m / s Glass layer 10: thickness L １ =3mm, relative dielectric constant ε １ = 6.5 (√ε １ =2.55) Transmittance adjustment layer 20: relative dielectric constant ε ２ = 2.7 (√ε ２ = 1.64) Relative permittivity ε in air ０ = 1.0

[0035] According to the above formula (1), the thickness L of the transmittance adjusting layer 20 can be calculated without using an expensive simulator. ２ Returning to FIG. 2, if the wavelength of the high frequency wave incident on the laminate 2 is λ, the amplitude A of the first reflected wave WR1 can be calculated as follows: １ , the amplitude A of the second reflected wave WR2 ２ , the amplitude A of the third reflected wave WR3 ３ can be calculated from the general formula (1) shown above as follows: A1=((ε0) 1 / 2 cosθ0-(ε1) 1 / 2 cosθ1) / ((ε0) 1 / 2 cosθ0+(ε １ ) 1 / 2 cosθ1) A2=(((ε1) 1 / 2 cosθ1-(ε ２ ) 1 / 2 cosθ2) / ((ε １ ) 1 / 2 cosθ1+(ε ２ ) 1 / 2 cosθ ２ ))・(1-A1 2 ) A3=(((ε ２ ) 1 / 2 cosθ ２ -(ε0) 1 / 2 cosθ ３ ) / ((ε ２ ) 1 / 2 cosθ ２ +(ε0) 1 / 2 cosθ ０ ))・(1-A1 2 )・(1-A2 2) Note that for the incident angle θ0, the refraction angles θ1 and θ ２ can be calculated as follows from Snell's law: θ １ =arcsin(sinθ ０ / √ε １ ) θ ２ =arcsin(sinθ ０ / √ε ２ )

[0036] Here, the phase shifts of the first reflected wave WR1, the second reflected wave WR2, and the third reflected wave WR3 from the incident wave are respectively Δx １ , Δx ２ , Δx ３ Then, they depend on the optical path difference, Δx １ = 0, Δx ２ = 2L1(ε0) 1 / 2 cosθ １ , Δx ３ = 2L1(ε0) 1 / 2 cosθ1+2L2((ε2) 1 / 2 -(ε1) 1 / 2 sinθ1(sinθ2) / cosθ2. At this time, the amplitude A of the composite wave of the reflected wave ｓ , the phase shift is Δx ｓ Then, A s sin(2π(x+Δx s )λ)=ΣA n sin((2π(x+Δx n )λ) (in this case, n=1,2,3) the intensity of the composite wave of the reflected wave is A s 2 can be derived.

[0037] FIG. 6A shows the reflection intensity (As ２ ) is a graph showing the thickness at which the intensity of the reflected wave is minimized (optimum thickness) and the thickness is periodically determined. ０ When the angle is 0°, the thickness L of the transmittance adjusting layer 20 in the first period ２ The optimum value for the incident angle is 1.8 mm, whereas it is 2.2 mm when the incident angle is 45° and 2.4 mm when the incident angle is 60°. The optimum values ​​obtained here match the simulation results in FIG.

[0038] 6B is a graph showing the sum of the reflection intensities at the respective incident angles shown in FIG. 6A. In this case, the minimum value of the graph is the thickness L of the transmittance adjusting layer 20. ２ appears near 2.2 mm, which roughly corresponds to the case where the incident angle is 45°.

[0039] Figure 7 is a graph showing the results of a simulation of the transmittance of high-frequency waves transmitted through the laminate 2 under the same conditions. The transmittance simulation below was performed using the multilayer board reflection / transmission coefficient (1D) simulator RT1D Ver. 1.2.0. This simulation software is available from the following website. It calculates transmittance by inputting the dielectric constant, 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 incident angle closely matches the simulation results in Figure 5 and the calculation results in Figure 6A. This multilayer board reflection / transmission coefficient (1D) simulator can also determine the transmittance maximum value after the second period, making it practically advantageous.

[0040] From the graphs explained above, it can be seen that when used in applications where high frequency waves are incident from directions other than the normal, such as in an in-vehicle antenna, it is preferable to adjust the thickness of the transmittance adjusting layer 20 based on the case where high frequency waves are incident obliquely. From the graph shown in Figure 5, it can be seen that if the optimum value of the thickness when θ0 = 45° is used as the standard, high transmittance (low reflectance) can be achieved over a relatively wide range of incident angles. Therefore, in general, the thickness Ln of the nth layer is set to L, which is the optimum value when the incident angle is 45°. ｎ４５ For example, L ｎ４５ ±λ / 10√ε n may be adjusted to the range.

[0041] When the antenna system 1 is incorporated into the window glass of a mobile object such as an automobile, the angle of incidence of high-frequency waves may not be constant. Furthermore, 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 in which the antenna system is installed. Therefore, in the present invention, the thickness of the high-frequency transmission layer is adjusted based on the thickness at which transmittance is maximized when high-frequency waves are incident at a predetermined inclination angle.

[0042] Here, looking at FIG. 5, the optimum value for the incident angle of 45°, L ２ The transmittance when the incident angle is 30° is the optimum value when the incident angle is 0°. ２ The transmittance is not much different from that when the incident angle is 1.8 mm, and even at an incident angle of 55°, the optimum value for the incident angle of 60° is obtained. ２ The transmittance is not much different from that when the transmittance adjusting layer 20 is not applied to the other angle ranges. ２ In other words, even if the transmittance is not strictly the optimum value, the thickness L of the transmittance adjusting layer 2 is ２ By adjusting L, it is possible to obtain the effect of compensating for the incidence angle dependency of the high frequency transmittance. ２ It will be appreciated that it is advantageous to adjust

[0043] In the above description, the thickness L of the transmittance adjusting layer 20 ２ However, if possible, the thickness L of the glass layer 1 may be adjusted. １ 5 to 7, the laminate 2 has been described as having a two-layer structure, but the number of high-frequency transmission layers constituting the laminate 2 is not limited to two, and may be three or more. In general terms, the thickness L of the nth high-frequency layer constituting the laminate is ｎ The optimum value at an incident angle of 45° is L ｎ４５ For example, L ｎ４５ ±λ / 10√ε n may be adjusted to the range.

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

[0045] The interlayer film 21 may be made of a different material from the transmittance adjustment layer 20, or may be made of the same material. For example, as shown in FIG. 10 , the interlayer films 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 may be provided with circuit boards 30 that are located at different distances from the first glass layer 10. In the example shown in FIG. 10 , the interlayer film of the laminated glass 3 is made of a laminate of a first interlayer 21a, a second interlayer 21b, a third interlayer 21c, and a fourth interlayer 21d, with the first interlayer 21a forming 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 forming the transmittance adjustment layer between the first glass layer 10 and the circuit board 30b.

[0046] As shown in Fig. 11 , the circuit board 30 of the antenna system 1 may be laminated on the back surface of the laminated glass 3 via a transmittance adjustment layer 20. In this case, the first glass layer 10 in the antenna system 1 that is bonded to the transmittance adjustment layer 20 serves as the back surface glass layer 12 of the laminated glass 3. In this case, the front surface glass layer 11 and the interlayer film 21 of the laminated glass 3 may also be considered to form part of the antenna system 1. Even in the configuration shown in Fig. 11 , it has been confirmed through simulations and calculations that providing the transmittance adjustment layer 20 on the back surface of the laminated glass 3 can suppress a decrease in transmittance that depends on the angle of incidence, and that adjusting the thickness of the transmittance adjustment layer 20 to a thickness that maximizes the transmittance based on an oblique angle of incidence can suppress a decrease in transmittance at low angles of incidence while also achieving high high-frequency transmittance even at angles of incidence of 40 degrees or more. In the embodiment of Figure 11, the front-side glass layer 11, the intermediate film 21, the first glass layer 10 (the back-side glass layer 12), and the transmittance adjustment layer 20 constitute the high-frequency transmission layer, and in this order they are the first to fourth layers of the high-frequency transmission layer.

[0047] 11 can also be produced by attaching a laminate 4 of a circuit board 30 and a transmittance adjustment layer 20 to ordinary laminated glass 3. Such an intermediate laminate 4 for an antenna system is also included in the present invention.

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

[0049] 10, a plurality of antenna circuit boards 30 may be arranged in one antenna system 1. In this case, the antenna system 1 may be a multi-band compatible antenna system 1 including a non-high frequency compatible antenna circuit board (not shown) that is intended for radio waves with frequencies of less than 1 GHz.

[0050] The antenna system 1 may be incorporated, for example, into the window glass of a building, or into the glass (windshield, side glass, rear glass, sunroof) of a moving body such as an automobile or train. For example, when visibility is required, such as in window glass or automobile glass, the antenna system circuit board 30 is preferably disposed in a location that does not obstruct visibility.

[0051] [Glass Layer] Thickness L of the first glass layer 10 １ can be set appropriately depending on the application of the object to which the first glass layer 10 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. When the first glass layer 10 is a window glass of a building, it may be relatively thick, but when it is to be a surface layer of the antenna system 1 as shown in FIG. 8, it may be thin from the viewpoint of weight reduction, and the thickness L １ 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] 11 , in the antenna system 1, the first glass layer 10 bonded to the transmittance adjusting layer 20 serves as the back glass 12 of the laminated glass 3. The thickness of the second glass layer can also be set appropriately depending on 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 frequency waves and then allow the high frequency waves to reach the antenna circuit board via the transmittance adjustment layer, but examples of the shape include planar glass, curved glass, etc.

[0054] The materials for the first and second glass layers are not particularly limited as long as they are materials commonly used for window glass, etc., and may be various translucent, transparent, or translucent organic glass members (e.g., acrylic members, polycarbonate members, etc.). However, from the viewpoints of weather resistance and transparency, inorganic glass members such as soda-lime glass, borate glass, borosilicate glass, aluminosilicate glass, and quartz glass are preferred. Glasses classified by alkali content include alkali-free glass and low-alkali glass. The content of alkali metal components (e.g., Na2O, KO, and Li2O) in the glass members is preferably 15 wt. % or less, more preferably 10 wt. % or less.

[0055] Any appropriate method can be adopted as a method for forming these glass layers depending on the shape and material of the glass. Typically, the glass member is produced by melting a mixture containing a main raw material such as silica or alumina, an antifoaming agent such as mirabilite or antimony oxide, and a reducing agent such as carbon at a temperature of 1400°C to 1600°C, forming it into a thin plate, and then cooling it. Examples of methods for forming the glass member into a thin plate include the slot downdraw method, the fusion method, and the float method. Glass formed into a predetermined shape such as a plate by these methods may be thinned or may have an uneven surface by anti-glare treatment, if necessary. Furthermore, to improve smoothness, the glass member may be chemically polished with a solvent such as hydrofluoric acid.

[0056] The first and second glass layers may be, for example, vehicle window panes (for example, window panes for vehicles such as cars, trains, airplanes, and ships) or architectural window panes.

[0057] Alternatively, a second glass layer may be combined with the first glass layer, with the antenna circuit board disposed therebetween. The second glass layer is generally a glass member disposed opposite the first glass layer in the thickness direction, and may be made of the same material as or a different material from the first glass layer.

[0058] The first and second glass layers may include a colored region, and an antenna circuit of the antenna circuit board may be disposed within the colored region. The colored region of the first and / or second glass layer may be partially provided (e.g., in an edge region) in particular when visibility is required, such as in window glass or vehicle glass.

[0059] [Transmittance Adjusting Layer] The transmittance adjusting (low dielectric layer) has a dielectric constant (relative permittivity) lower than that of the first glass layer, and serves to allow high frequency waves incident from the first glass layer to reach the antenna circuit board. The low dielectric layer has a smaller dielectric constant than the first glass layer when compared at the same frequency.

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

[0061] The dielectric properties (relative permittivity and dielectric loss tangent) are preferably measured using a microstrip line method, which can measure the permittivity in the thickness direction. In the case of isotropic materials, the dielectric properties in the planar direction, which can be measured using the Fabry-Perot method, can be used instead. In this case, measurements can be performed in accordance with JIS R 1660-2 at 28 GHz (25°C) using a Fabry-Perot resonator (Model No. DPS03) manufactured by Keycom Corporation. This measurement method allows for highly accurate measurements in both one direction in a plane and in the direction perpendicular to that (X-Y directions), and can even be used to measure materials with low tan δ.

[0062] In one embodiment, for example, at a frequency of 28 GHz, the relative dielectric constant 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 dielectric constant 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 aspect, 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 aspect, the dielectric constant and dissipation factor of the second glass layer can be similar to those of the first glass layer.

[0065] In the present 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 the low dielectric layer 20 may be a laminate of two or more thin layers.

[0066] In one embodiment, the thickness L of the low dielectric layer ２ Is, L ２ｍｉｎ ±λ / (10√ε ２ ) may be selected from a wide range of about 1 μm to 20.0 mm.

[0067] The low dielectric layer (transmittance adjustment 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, for example, from a thermoplastic resin or a thermosetting resin having a predetermined dielectric constant.

[0068] In one embodiment, the low dielectric layer is preferably an adhesive low dielectric layer having adhesive properties, since this allows for easy adhesion at the interface between the first glass layer and the low dielectric layer and at 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 to the antenna circuit board, and is preferably adhesive to both.

[0069] If the low-dielectric layer has thermal adhesive properties, the low-dielectric layer material may be melted to fuse the antenna circuit board and the first glass via the low-dielectric layer material. Alternatively, if a solution obtained by dissolving the low-dielectric layer material in a solvent has adhesive properties, the low-dielectric layer material solution may be applied to the bonding surfaces of the first glass and / or the antenna circuit board to bond the antenna circuit board and the first glass via the low-dielectric layer material. Note that fusion or bonding (hereinafter referred to as "fusion, etc.") is preferably performed under degassing and / or reduced pressure to prevent air from being mixed in. Degassing may be performed by physically pushing air out of the bonding interface. Fusion, etc. may be performed by preliminarily fusing or bonding the antenna circuit board and the low-dielectric material to form a laminate, and then fusing the laminate and the first glass under degassing and / or reduced pressure.

[0070] Examples of adhesive low-dielectric layers include polyvinyl acetal resins, olefin-vinyl carboxylate copolymer resins, ionomer resins, acrylic resins, urethane resins, vinyl chloride resins, fatty acid polyamides, polyester resins, silicone elastomers, epoxy resins, and polycarbonates, which have good affinity for glass materials such as inorganic glass and resin glass (these materials are described below). When the adhesive low-dielectric layer can be bonded by thermocompression, it is possible to prevent circuit breakage and deformation during bonding, and even when the glass substrate is curved glass such as an automobile windshield, it can conform to the glass substrate and prevent foaming and peeling. Furthermore, when forming an antenna system using laminated glass in which a high-frequency antenna circuit board is embedded between the glass substrates, lamination can be performed under typical laminated glass manufacturing conditions, thereby eliminating additional steps.

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

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

[0073] The antenna circuit board 30 may be a circuit board (or a semiconductor device mounting board) on which a semiconductor device (e.g., an IC chip, not shown) is mounted. The antenna circuit board 30 can be connected to a transmitting / receiving device (not shown), for example, via a conductive band (not shown).

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

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

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

[0077] The antenna circuit board may be used for various known or conventional transmission lines, such as a coaxial line, a strip line, a microstrip line, a coplanar line, a parallel line, etc., or may be used for an antenna (e.g., a microwave or millimeter wave antenna).The circuit board may also be used for an antenna device in which an antenna and a transmission line are integrated.

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

[0079] The radio frequency antenna circuit board may be capable of supporting data transmission speeds of 10 gigabits per second or higher, for example, the radio frequency antenna circuit board may be a circuit board compatible with 5G and next generation networks.

[0080] The area of ​​the antenna circuit board is not limited, but may be, for example, 5 cm x 5 cm, 3 cm x 3 cm, or 25 cm ２ Less than 20 cm, preferably ２ Less than 10 cm, more preferably ２ The lower limit is not particularly limited as long as the antenna system operates, but may be as small as 1 cm. ２ It may be to some extent.

[0081] (High-frequency insulating layer) The antenna circuit board preferably includes 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 transmission loss of electrical signals in high-frequency circuits. Examples of the high-frequency insulating layer include insulating layers made of heat-resistant resins such as thermoplastic liquid crystal polymer (LCP), polyimide (PI) (particularly modified polyimide (MPI)), polyethylene naphthalate (PEN), and polyether ether ketone (PEEK). Among these, insulating layers made of polyimide are preferably used because they have excellent heat resistance and chemical resistance. Furthermore, thermoplastic liquid crystal polymers are preferably used because of their excellent dielectric properties.

[0082] For example, the insulating layer may be formed from a thermoplastic liquid crystal polymer film or a polyimide film, in which case a circuit layer or the like can be provided on the thermoplastic liquid crystal polymer film or the polyimide film to obtain an antenna circuit board. 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 set appropriately depending on the required antenna performance, etc., and can be selected from a wide range of, for example, 10 μm to 2.5 mm, and may be, for example, 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. When the antenna circuit board is a multilayer circuit board, the thickness of the insulating layer refers to the overall thickness of the insulating layers constituting the multilayer circuit board (or the total thickness of all the insulating layers).

[0084] The dielectric constant εp in both one direction and the direction perpendicular to the plane of the high-frequency insulating layer may be, for example, 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. The dielectric constant εf of the low dielectric layer and the dielectric constant 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 the direction perpendicular to the plane of the high-frequency insulating layer may be, for example, 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 above-mentioned method.

[0086] [Manufacturing Method of Antenna System] The manufacturing method of the antenna system can be similar to the method described in the examples of Patent Document 2, except that the thickness control range of the transmittance adjustment layer 20 is different. A circuit is formed by thermocompression bonding copper foil to both sides of an insulating film and 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 together. The antenna circuit board thus formed is then laminated with a separately prepared low-dielectric film and glass, and a laminate is formed using a vacuum laminator or a vacuum bag, etc., to obtain an antenna system with the desired structure. Specific examples of the manufacturing method will be described later.

[0087] [Materials for Transmittance Adjusting Layer] Materials that can be suitably used for the transmittance adjusting layer (low dielectric layer) 20 explained above will be described below.

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

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

[0090] Polyvinyl alcohol can be obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester compound, and a vinyl alcohol copolymer can be obtained by saponifying a copolymer of a vinyl ester compound and another monomer.

[0091] Examples of vinyl ester compounds include aliphatic vinyl carboxylates such as vinyl acetate, 1-propenyl acetate, 1-methylvinyl acetate, 1-butenyl acetate, 2-methyl-1-propenyl acetate, vinyl propionate, vinyl butanoate, vinyl pivalate, vinyl versatate, vinyl pentanoate, vinyl hexanoate, vinyl octanoate, vinyl decanoate, vinyl dodecanoate, vinyl hexadecanoate, 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] Examples of other monomers include 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, and octadecyl methacrylate; acrylamide; N-methylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, diacetone acrylamide, acrylamidopropanesulfonic acid and its salts, acrylamidopropyldimethylamine and its salts or its quaternary salts, N-methylolacrylamide, N-methylolpropanesulfonic acid and its salts ... methacrylamide derivatives such as methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidepropanesulfonic acid and salts thereof, methacrylamidepropyldimethylamine and salts or quaternary salts thereof, N-methylolmethacrylamide and derivatives thereof; 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, stearyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides 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 salts thereof, esters thereof, or anhydrides thereof; and vinylsilyl compounds such as vinyltrimethoxysilane. The other monomers can be used alone or in combination of two or more, and among these, ethylene is preferred as the other monomer.

[0093] The acid catalyst used in the acetalization reaction is not particularly limited, and either an organic acid or an inorganic acid can be used, such as acetic acid, paratoluenesulfonic acid, nitric acid, sulfuric acid, hydrochloric acid, etc. Among these, hydrochloric acid, sulfuric acid, and nitric acid are preferred from the viewpoints of acid strength and ease of removal during washing.

[0094] The aldehyde (or keto compound) used in the production of the polyvinyl acetal resin is preferably linear, branched, or cyclic, and more preferably linear or branched, having 1 to 10 carbon atoms, resulting in a corresponding linear or branched acetal side chain. The polyvinyl acetal resin used in the present invention may also be one obtained by acetalizing polyvinyl alcohol or a vinyl alcohol copolymer with a mixture of multiple aldehydes (or keto compounds). The polyvinyl alcohol or vinyl alcohol copolymer may be composed of either one alone, or may be a mixture of polyvinyl alcohol and a 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 having 2 to 6 carbon atoms are preferred, and n-butyraldehyde is particularly preferred from the viewpoint of facilitating the production of a polyvinyl acetal resin having suitable breaking energy. These aldehydes can be used alone or in combination of two or more. Furthermore, polyfunctional aldehydes or aldehydes having other functional groups may be used in combination in an amount of 20% by mass or less of the total aldehydes. When n-butylaldehyde is used, the content of n-butylaldehyde in the aldehydes 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 even 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 more, more preferably 300 or more, more preferably 400 or more, even more preferably 600 or more, particularly preferably 700 or more, and most preferably 750 or more. When using a polyvinyl acetal resin composition containing a large 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 more, more preferably 900 or more, more preferably 1000 or more, even more preferably 1200 or more, particularly preferably 1500 or more, and most preferably 1600 or more. 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, according to JIS K 6726 "Test Method for Polyvinyl Alcohol."

[0097] Generally, the viscosity-average degree of polymerization of a polyvinyl acetal resin is equal to that of the polyvinyl alcohol used as a raw material, and therefore the preferred viscosity-average degree of polymerization of the polyvinyl alcohol is equal to that of the polyvinyl acetal resin. When the low dielectric layer contains two or more different polyvinyl acetal resins, it is preferred that the viscosity-average degree of polymerization of at least one of the polyvinyl acetal resins is equal to or greater than the lower limit and equal to or less than 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 in 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 different polyvinyl acetal resins, it is preferable that the amount of acetyl groups in at least one polyvinyl acetal resin be 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 within 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 of the polyvinyl acetal resin with the plasticizer is less likely to decrease. When the low dielectric layer contains two or more different polyvinyl acetal resins, it is preferable that the degree of acetalization of at least one of the polyvinyl acetal resins is within the above range.

[0100] The hydroxyl group content of 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 in the polyvinyl acetal main chain. The hydroxyl group content can be adjusted within the above range by adjusting the amount of aldehyde used when acetalizing the polyvinyl alcohol resin. When the low dielectric layer contains two or more different polyvinyl acetal resins, it is preferable that the hydroxyl group content of at least one polyvinyl acetal resin be within the above range.

[0101] A polyvinyl acetal resin is usually composed of acetal group units, hydroxyl group units, and acetyl group units, and the amount of each of these units can be measured, for example, according to JIS K 6728 "Testing Methods for Polyvinyl Butyral" or by nuclear magnetic resonance (NMR). When a polyvinyl acetal resin contains units other than acetal group units, the amount of hydroxyl group units and the amount of acetyl group units are measured, and the amount of these units is subtracted from the amount of acetal group units in a resin containing no units other than acetal group units, thereby calculating the amount of remaining acetal group units.

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

[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 weight solution of toluene / ethanol = 1 / 1 (mass ratio), measured at 20 °C and 30 rpm using a Brookfield (B-type) 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 with a viscosity within the above range, it is easy to set the heating temperature or heating time within the desired range when bonding to a glass substrate by thermocompression, making it less likely that unmelted portions of the polyvinyl acetal resin will remain. Furthermore, misalignment of the antenna circuit board can be suppressed even when the antenna system is exposed to high temperatures. The viscosity of the polyvinyl acetal resin can be adjusted by using or combining a polyvinyl acetal resin produced using, as a raw material or as part of a raw material, a polyvinyl alcohol-based resin having a high or low viscosity average polymerization degree. When the polyvinyl acetal resin used to form the low dielectric layer is a mixture of multiple resins, the viscosity described above is the viscosity of such a mixture.

[0104] Furthermore, the polyvinyl acetal resin may be combined with a known or commonly used plasticizer, if necessary. Examples of the plasticizer include the following. These plasticizers may be used alone 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 a polyvinyl acetal resin.

[0105] As the plasticizer, for example, the following can be used: Esters of polyvalent aliphatic or aromatic acids. Examples of the ester include dialkyl adipates (e.g., dihexyl adipate, di-2-ethylbutyl adipate, dioctyl adipate, di-2-ethylhexyl adipate, hexylcyclohexyl adipate, a mixture of heptyl adipate and nonyl adipate, diisononyl adipate, and heptylnonyl adipate); esters of adipic acid and an alicyclic ester alcohol or an alcohol containing an ether compound (e.g., di(butoxyethyl) adipate and di(butoxyethoxyethyl) adipate); dialkyl sebacates (e.g., dibutyl sebacate); esters of sebacic acid and an alicyclic alcohol or an alcohol containing an ether compound; esters of phthalic acid (e.g., butyl benzyl phthalate and bis-2-butoxyethyl phthalate); and esters of alicyclic polycarboxylic acids and 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. Specific 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] In addition, polyesters or oligoesters composed of polyhydric alcohols and polycarboxylic acids, terminal esterified or etherified products thereof, polyesters or oligoesters composed of lactones or hydroxycarboxylic acids, or terminal esterified or etherified products thereof may also be used as plasticizers.

[0108] The content of the plasticizer 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, based on the total amount of the polyvinyl acetal resin and the plasticizer. Preferred polyvinyl acetal resins are commercially available, for example, from Kuraray Co., Ltd. under the name "Mobital (trademark)," and polyvinyl acetal resin films are commercially available, for example, from Kuraray Co., Ltd. under the name "Trosifol (trademark)."

[0109] Alternatively, when adhering a low-dielectric layer made of a polyvinyl acetal resin to an adherend, a plasticizer may be further applied to a film made of the polyvinyl acetal resin to enhance the adhesiveness of the polyvinyl acetal resin. The plasticizers described above can be used as such plasticizers, and because they can improve the adhesiveness 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, with triethylene glycol-bis-(2-ethylhexanoate), di(butoxyethyl) adipate, and di(butoxyethoxyethyl) adipate being more preferred, and di(butoxyethyl) adipate and di(butoxyethoxyethyl) adipate being particularly preferred.

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

[0111] The olefin-vinyl carboxylate copolymer resin may further contain a third monomer as a copolymerization component, as long as the dielectric constant can be controlled within a predetermined range. Examples of the third monomer include the 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 vinyl silyl compounds described in the section on polyvinyl acetal resins. These monomers can be used alone or in combination of two or more. When these other monomers are copolymerized, it is usually preferable to use these other monomers in a proportion of less than 10 mol % relative to the vinyl carboxylate compound.

[0112] In the olefin-vinyl carboxylate copolymer resin, from the viewpoint of strength, the ratio of vinyl carboxylate units to the total of olefin units and vinyl carboxylate units is, for example, 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 the vinyl carboxylate is not particularly limited, but may be, for example, about 5 mol%. A preferred olefin-vinyl carboxylate copolymer resin is, for example, ethylene vinyl acetate, which is commercially available from Tosoh Corporation under the trade name "Mersene (trademark)."

[0113] (Ionomer Resin) The ionomer resin is not particularly limited, but examples thereof include thermoplastic resins having structural units derived from olefins such as ethylene and structural units derived from α,β-unsaturated carboxylic acids, in which at least a portion of the α,β-unsaturated carboxylic acids is neutralized with metal ions. Examples of the 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 with metal ions, the content of α,β-unsaturated carboxylic acid structural units is preferably 2% by mass or more, more preferably 5% by mass or more, based on the mass of the ethylene-α,β-unsaturated carboxylic acid copolymer, and the content of α,β-unsaturated carboxylic acid structural units is preferably 30% by mass or less, more preferably 20% by mass or less.

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

[0116] As the ionomer resin, from the viewpoint of easy availability, ionomers of ethylene-acrylic acid copolymers and ionomers of ethylene-methacrylic acid copolymers are more preferred, 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. Ionomer resins can be used alone or in combination of two or more. A film made of a preferred ionomer resin is commercially available, for example, from Kuraray Co., Ltd. under the name "Sentryglass (trademark)."

[0117] (Acrylic Resin) The acrylic resin is preferably a polymer obtained from an acrylic acid ester monomer and / or a methacrylic acid ester monomer, and 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 alone or in combination of two or more.

[0118] In addition, 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; aromatic vinyl compounds such as styrene and α-methylstyrene; and the like can also be suitably used as the acrylic resin.

[0119] A preferred acrylic resin is a liquid injection type resin marketed by Shinko Glass Industry Co., Ltd. under the name "3S Resin."

[0120] The low dielectric layer may contain known or conventional additives as needed. Examples of the additives include solvents, plasticizers, ultraviolet absorbers, antioxidants, adhesion modifiers, brighteners or fluorescent brighteners, stabilizers, dyes, processing aids, organic or inorganic nanoparticles, calcined silica, and surfactants. The additives can be used alone or in combination. [Materials of the High-Frequency Insulation Layer]

[0121] From the viewpoint of excellent heat resistance, an insulating layer made 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 an imide group in its structural unit, and examples thereof include polyimide-based resins such as polyimide, polyamideimide, polybenzimidazole, polyimide ester, polyetherimide, and polysiloxaneimide.

[0122] Polyimides can be formed by imidizing (curing) polyamic acid precursors. Polyamic acids can be synthesized by reacting known diamines with tetracarboxylic acids (including their acid anhydrides) in the presence of a solvent. Examples of diamines that can be used include aromatic diamines, aliphatic diamines, and alicyclic diamines. From the perspective of heat resistance, aromatic diamines are preferred. 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. The tetracarboxylic acid may be an aromatic tetracarboxylic acid, an aliphatic tetracarboxylic acid, an alicyclic tetracarboxylic acid, or an anhydride thereof, with aromatic tetracarboxylic acid anhydrides being 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 anhydride. These diamines and tetracarboxylic acids may be used alone or in combination of two or more.

[0123] The polyimide film used in the polyimide insulating layer can be produced, for example, by applying a solution of polyamic acid (polyimide precursor) obtained by reacting a diamine with a tetracarboxylic acid to a support, drying the solution to obtain a polyamic acid film, and then heat-treating the film to harden (imidize). The polyamic acid solution can be applied by known coating methods such as spin coating, comma coating, screen printing, slit coating, roll coating, knife coating, dip coating, and die coating.

[0124] Various additives, fillers, etc. may be added to the polyimide film within the range that does not impair the effects of the present invention.

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

[0126] From the viewpoint of excellent dielectric properties, an insulating layer made 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 crystal polymer that can be melt-formed. This thermoplastic liquid crystal polymer is a polymer that can form an optically anisotropic molten phase, and its chemical structure is not particularly limited as long as it is a liquid crystal polymer that can be melt-formed. Examples of the thermoplastic liquid crystal polymer include thermoplastic liquid crystal polyester and thermoplastic liquid crystal polyester amide in which an amide bond is introduced therein.

[0127] The thermoplastic liquid crystal polymer may also be a polymer in which an isocyanate-derived bond such as an imide bond, a carbonate bond, a carbodiimide bond or an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide.

[0128] Specific examples of the thermoplastic liquid crystal polymer used in the present invention include known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyester amides derived from the compounds classified as (1) to (4) shown 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)

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

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

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

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

[0134]

[0135]

[0136] Among these copolymers, polymers containing at least p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid as repeating units are preferred, and particularly preferred are (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.

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

[0138] In the case of the polymer (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 dicarboxylic acid (E) selected from the group consisting of terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. The molar ratio of each repeating unit of the aromatic hydroxycarboxylic acid (C): the aromatic diol (D): the aromatic dicarboxylic acid (E) in the thermoplastic liquid crystal polymer may be about (30 to 80): (35 to 10): (35 to 10), more preferably about (C): (D): (E) = (35 to 75): (32.5 to 12.5): (32.5 to 12.5), and even more preferably about (C): (D): (E) = (40 to 70): (30 to 15): (30 to 15).

[0139] The molar ratio of repeating units derived from 6-hydroxy-2-naphthoic acid in 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 in 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] Alternatively, 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 this case, the molar ratio of the two aromatic diols (D1) / (D2) may be 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 the repeating structural units derived from the aromatic diol to the repeating structural units derived from the aromatic dicarboxylic acid, (D) / (E), is preferably 95 / 100 to 100 / 95. If the ratio is outside this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

[0142] The ability to form an optically anisotropic molten phase in the present invention can be confirmed, for example, by placing a sample on a hot stage, heating it in a nitrogen atmosphere, and observing the light transmitted through the sample.

[0143] The preferred thermoplastic liquid crystal polymer has a melting point (hereinafter referred to as Tm ０ The Tm ０ The Tm ０ The melting point of the thermoplastic liquid crystal polymer sample is determined by measuring the temperature at which the main endothermic peak appears using a differential scanning calorimeter (Shimadzu DSC). That is, the thermoplastic liquid crystal polymer sample is heated at a rate of 10°C / min until it is completely melted, then cooled to 50°C at a rate of 10°C / min, and heated again at a rate of 10°C / min. The position of the endothermic peak that appears after this is determined as the melting point of the thermoplastic liquid crystal polymer sample.

[0144] To the thermoplastic liquid crystal polymer, thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyether ether ketone, and fluororesin, various additives, fillers, and the like may be added within a range that does not impair the effects of the present invention.

[0145] The thermoplastic liquid crystal polymer film can be obtained, for example, by extrusion molding a melt-kneaded product of the thermoplastic liquid crystal polymer. Any method can be used as the extrusion molding method, but the well-known T-die method, inflation method, etc. are industrially advantageous. In particular, in the inflation method, stress is applied not only in the machine axis direction (hereinafter abbreviated as MD direction) of the thermoplastic liquid crystal polymer film, but also in the direction perpendicular to it (hereinafter abbreviated as TD direction), and it can be uniformly stretched in the MD direction and the TD direction, so that a thermoplastic liquid crystal polymer film with controlled molecular orientation, dielectric properties, etc. in the MD direction and the TD direction can be obtained.

[0146] If necessary, known or conventional heat treatment may be performed to adjust the melting point and / or thermal expansion coefficient of the thermoplastic liquid crystal polymer film. The heat treatment conditions can be appropriately set depending on the purpose. For example, the melting point (Tm) of the thermoplastic liquid crystal polymer film may be increased by heating for several hours at a temperature equal to or higher than the melting point (Tm) of the thermoplastic liquid crystal polymer (Tm) - 10°C (for example, about Tm - 10°C to Tm + 30°C, preferably about Tm °C to Tm + 20°C).

[0147] By providing a circuit layer and / or a conductor layer on the obtained thermoplastic liquid crystal polymer film by a known or conventional method, it is possible to prepare an antenna circuit board having a thermoplastic liquid crystal polymer insulating layer.

[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. That is, the position of the endothermic peak that appears when the temperature of a thermoplastic liquid crystal polymer film sample is raised 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 may have, for example, a thermal expansion coefficient of 0 to 25 ppm / ° C., and the thermal expansion coefficient may preferably be about 5 to 22 ppm / ° C. The thermal expansion coefficient can be determined as a value measured between 30° C. and 150° C. using a thermomechanical analyzer (TMA) by heating from 25° C. to 200° C. at a rate of 5° C. / min, then cooling to 30° C. at a rate of 20° C. / min, and heating again at a rate of 5° C. / min.

[0150] The following examples illustrate how the present invention may be practiced, but the present invention is not limited to these examples in any way.

[0151] [Dielectric Constant and Dielectric Loss Tangent] For films used in the low dielectric layer and high-frequency insulating layer, the dielectric constant and dielectric loss tangent in the thickness direction can be measured by the microstrip line method. Furthermore, the dielectric constant and dielectric loss tangent in the planar direction can be measured in accordance with JIS R 1660-2 at a frequency of 28 GHz (25°C) using a Fabry-Perot resonator (Model No. DPS03) manufactured by Keycom Corporation. The measurements are performed in both one direction in the plane and in the direction perpendicular to that direction (X-Y direction).

[0152] [Thickness of Antenna Circuit Board and Low Dielectric Layer] The thickness of the antenna circuit board can be measured by using a micrometer (Model 227-201-CLM-15QM, manufactured by Mitutoyo Corporation) on the antenna circuit board. The thickness of the low dielectric layer is measured using a film used as the low dielectric layer. The thickness of the low dielectric layer may be obtained by measuring the thickness of the entire antenna system, and the thickness of the antenna circuit board and glass in the antenna system, and subtracting the thickness of the antenna circuit board and glass from the thickness of the entire antenna system.

[0153] [Solution Viscosity of Polyvinyl Acetal Resin] The polyvinyl acetal resin constituting the polyvinyl acetal resin film is dissolved in a mixed solvent of toluene / ethanol = 1 / 1 (mass ratio) to prepare a solution to a concentration of 10 mass %. The viscosity of this solution is measured using a Brookfield (B-type) viscometer at 20 ° C. and a rotation speed of 30 rpm.

[0154] [Calculation of Optimal Layer Thickness-1] Using the multilayer board reflection / transmission coefficient (1D) simulator RT1D Ver. 1.2.0, the thickness L of the transmittance adjustment layer at which the transmittance becomes maximum was calculated for the cases of a frequency of 28 GHz, a glass thickness of 2 mm, and a frequency of 28 GHz, a glass thickness of 3 mm, and for the cases of ... high frequency incident angle of 0°, 30°, 45°, 60°, and 75° on the laminate of glass and transmittance adjustment layer, where the relative permittivity of the glass layer is 6.5 and the relative permittivity of the transmittance adjustment layer is 2.7. ２ The results are shown in Table 7.

[0155]

[0156] Here, the wavelength of the high frequency is 10.7 mm, so λ / 10√ε ２ Therefore, for example, based on the optimum value of 45°, when the glass layer is 2 mm, the thickness L of the transmittance adjusting layer is in the range of 0.6±0.65 mm or 4.2±0.65 mm, and when the glass layer is 3 mm, the thickness L is in the range of 2.1±0.65 mm or 5.7±0.65 mm. ２ Just adjust the following.

[0157] [Calculation of Optimal Layer Thickness-2] For the case of a frequency of 5.8 GHz and a glass thickness of 3 mm, and for the case of a frequency of 28 GHz and a glass thickness of 3 mm, the thickness L at which the intensity of the reflected wave becomes minimum was calculated using the following formula (1) for the cases of the high frequency incident angle to the laminate of glass and transmittance adjustment layer of 0°, 30°, 45°, 60°, and 75°, where the relative permittivity of the glass layer is 6.5 and the relative permittivity of the transmittance adjustment layer is 2.7. ２ Specifically, a graph showing the thickness dependency of reflection intensity similar to that shown in FIG. 6A was prepared under the conditions for the two-layer high-frequency transmission layer described above, and the optimum value was read. The calculation results are shown in Table 8.

[0158] where ε ｎ is the relative dielectric constant of the nth layer constituting the laminate, L ｎ is the thickness of the nth layer constituting the laminate, θ ｎ is the refraction angle of the high frequency wave incident on the nth layer of the laminate (the angle of incidence from the nth layer to the (n+1)th layer), λ is the wavelength in air of the high frequency wave incident on the laminate, ε ０ represents the relative permittivity in air, n is an integer of 1 or more, and A ０ = 0, Δx ０ = 0, L ０ = 0, θ ０ = incident angle of high frequency wave incident on the laminate (first layer of the laminate)

[0159] When the frequency of the high frequency is 28 GHz and the thickness of the glass layer is 3 mm, the thickness L of the transmittance adjusting layer obtained from the minimum value of the reflection intensity is ２ The optimum value of is a value close to the value obtained from the transmittance simulation shown in Table 7. In this case, in the case of a frequency of 5.8 GHz, the wavelength of the high frequency is 51.7 mm, so λ / 10√ε ２ is 3.15 mm, and the frequency is 28 GHz, as shown above, λ / 10√ε ２is 0.65 mm. Therefore, the thickness of the transmittance adjustment layer may be controlled within a range of ±3.15 mm when the radio frequency is 5.8 GHz, and ±0.65 mm when the radio frequency is 28 GHz, relative to the optimal layer thickness for an incident angle of 45° obtained from the table. The optimal value of the layer thickness of the radio frequency transmission layer (in this case, the transmittance adjustment layer) obtained in this manner can be applied, for example, to the manufacture of the antenna system described below.

[0160] (Preparation of Antenna Circuit Board) Copper foil (Fukuda Metal Foil and Powder Co., Ltd., electrolytic copper foil "H9A", thickness 12 μm) was superimposed on both sides of a thermoplastic liquid crystal polymer film (manufactured by Kuraray Co., Ltd., Vecstar (registered trademark), 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: 0.002, dielectric loss tangent in the Y direction: 0.002) and a vacuum heat press was used to set the heating plate to 290 ° C. and press the platen under a pressure of 4 MPa for 15 minutes to produce a copper foil / thermoplastic liquid crystal polymer film / copper foil copper clad laminate. A portion of the copper foil on one side of the obtained copper clad laminate was removed with an etching solution to form a circuit, and this operation was repeated to produce a 400 μm thick antenna circuit board (length 5 cm, width 5 cm).

[0161] (Preparation of Polyvinyl Acetal Resin Film) Polyvinyl butyral resin 1 (hydroxyl group content 19.8% by mass, acetalization degree 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, acetalization degree 70.4 mol%, acetyl group content 0.9% by mass, resin viscosity 1410 mPa·s) were blended in a mass ratio of 75:25, melt-kneaded, extruded into strands, and pelletized. The obtained pellets were melt-extruded using a single-screw extruder and a T-die, and a 12 mm-thick polyvinyl acetal resin film with a smooth surface was obtained using an elastic metal roll (relative dielectric constant in X direction: 2.5, relative dielectric constant in Y direction: 2.5, dielectric dissipation factor in X direction: 0.01, dielectric dissipation factor in Y direction: 0.01, plasticizer content: 0 mass%, resin viscosity: 245 mPa s).

[0162] (Preparation of Laminate) A single-sided embossed Teflon® sheet, the dried polyvinyl acetal resin film prepared above, measuring 5 cm long, 5 cm wide, and 12 mm thick, the antenna circuit board prepared above (5 cm long, 5 cm wide), a single-sided embossed Teflon® sheet, and an upper glass sheet measuring 5 cm long, 5 cm wide, and 3 mm thick are stacked and fixed in this order on a lower glass sheet measuring 20 cm long, 10 cm wide, and 3 mm thick. The polyvinyl acetal resin film, antenna circuit board, and upper glass sheet are aligned so that they overlap each other. The Teflon® sheet adjacent to the polyvinyl acetal resin film is positioned so that the embossed surface is in contact with the polyvinyl acetal resin film. The Teflon® sheet adjacent to the antenna circuit board is positioned so that the mirror surface is in contact with the antenna circuit board. The antenna circuit board is positioned so that the surface bearing the circuit is in contact with the polyvinyl acetal resin film. These were heated in a vacuum laminator at 140 ° C. for 15 minutes, and then the upper chamber was set to -10 kPa (a pressure difference with the lower chamber of approximately 90 kPa) and held for 15 minutes, after which the pressure was returned to normal pressure. The Teflon (registered trademark) sheets and upper and lower glass sheets were removed, and a laminate was produced in the following order: polyvinyl acetal resin film (transmittance adjusting layer) / circuit (circuit layer) / antenna circuit board inner layer (multilayer board with a thermoplastic liquid crystal polymer film as an insulating layer) / copper foil (conductor layer). The layer thickness of the polyvinyl acetal resin film can be adjusted to the desired thickness by laminating and pressing multiple layers together as needed.

[0163] (Fabrication of Antenna System) The above laminate (5 cm long, 5 cm wide) was placed on a lower glass sheet measuring 20 cm long, 10 cm wide, and 3 mm thick, with a relative permittivity in the X direction of 6.5, a relative permittivity in the Y direction of 6.5, and a dielectric loss tangent in the X direction of 0.01 and a dielectric loss tangent in the Y direction of 0.01, with the polyvinyl acetal resin film (transmittance adjustment layer) in contact with the lower glass sheet. A Teflon (registered trademark) sheet and an upper glass sheet measuring 5 cm long, 5 cm wide, and 3 mm thick were then placed on top of the laminate and secured in this order. The antenna circuit board was positioned 2 cm to 7 cm inward from the vertical edge of the lower glass sheet. The laminate and the upper glass sheet were aligned so that they overlapped each other. These are heated in a vacuum laminator at 140°C for 15 minutes, then the upper chamber is set to -10 kPa (a pressure difference with the lower chamber of approximately 90 kPa) and held for 15 minutes, after which the pressure is returned to normal pressure, the Teflon (registered trademark) sheet and upper glass are removed, and an antenna system is obtained in which the glass (f) / polyvinyl acetal resin film (transmittance adjustment layer) / circuit (circuit layer) / antenna circuit board inner layer (multilayer board with a thermoplastic liquid crystal polymer film as an insulating layer) / copper foil (conductor layer) are laminated in this order, with the antenna circuit board disposed on part of the glass. In the resulting 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 above example, 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, a low dielectric layer and a second glass layer may be further laminated under the antenna circuit board.

[0165] Instead of the transmittance adjusting layer used in the above example, the following transmittance adjusting layer can also be used. (A) Polyvinyl butyral resin 1 (hydroxyl group content 19.8% by mass, acetalization degree 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, acetalization degree 70.4 mol%, acetyl group content 0.9% by mass, resin viscosity 1410 mPa s) were blended in a mass ratio of 75:25, and the blend was formed in the same manner as above to give a polyvinyl acetal resin film (relative dielectric constant in X direction: 2.5, relative dielectric constant in Y direction: 2.5, dielectric loss tangent in X direction: 0.01, dielectric loss tangent in Y direction: 0.01, plasticizer content: 0% by mass, resin viscosity: 245 mPa s). (B) Ionomer resin film (manufactured by Kuraray Co., Ltd., SentryGlas (registered trademark) (B) Polyvinyl acetal film (manufactured by Kuraray Co., Ltd., V200KE, thickness 700 μm, relative permittivity in X direction: 2.7, relative permittivity in Y direction: 2.7, dielectric dissipation factor in X direction: 0.02, dielectric dissipation factor in Y direction: 0.02)

[0166] The following insulating layers may be used instead of the insulating layers used in the above examples: Polyimide film (Kapton 300H, manufactured by Toray DuPont Co., Ltd., thickness 75 μm, relative permittivity in the X direction: 3.3, relative permittivity in the Y direction: 3.3, dielectric dissipation factor in the X direction: 0.007, dielectric dissipation factor in the Y direction: 0.007); Polyimide film (Apical NPI, manufactured by Kaneka Corporation, thickness 50 μm, relative permittivity in the X direction: 3.4, relative permittivity in the Y direction: 3.4, dielectric dissipation factor in the X direction: 0.004, dielectric dissipation factor in the Y direction: 0.004).

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

[0168] In the above example, a laminator is used to laminate the layers, but the laminated materials may be placed in a vacuum bag, preheated, and then heated and pressurized. For example, as an example of specific conditions, the laminated materials may be placed in a vacuum bag, depressurized at room temperature for 15 minutes, heated to 100°C while still under reduced pressure, and held there for 30 minutes, then cooled, the depressurized state released, and temporarily pressure-bonded, and then 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, adhering it to glass, and then drying it with hot air.

[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 so-called connected cars, which are used for autonomous driving and continuous communication by onboard devices, or as an antenna system for small cell base stations by installing it on the windows or walls of buildings or various civil engineering structures (railway facilities, road facilities, energy facilities, dams and river facilities, water and sewerage facilities, and airport facilities). For example, the antenna system of the present invention can be used by forming 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 in electronic devices such as display devices. Examples of display devices include large-screen televisions, monitors, tablets, smartphones, laptop computers, desktop computers, personal digital assistants, and other display devices. The antenna system of the present invention can also be installed on the back glass of a smartphone or the like.

[0171] While the preferred embodiments of the present invention have been described above with reference to the drawings, those skilled in the art will readily recognize various changes and modifications within the scope of the present invention upon reading the specification. Accordingly, such changes and modifications are to be interpreted as falling within the scope of the invention as defined by the claims.

[0172] Antenna system 1 Laminate 2 Laminated glass 3 Laminate for antenna system 4 First glass layer 10, 11 Transmittance adjustment layer (low dielectric layer) 20 Interlayer 21, 21a to 21d Antenna circuit board 30, 31 Circuit layer 30a, 31a High frequency insulating layer 30b, 31b Conductor layer 30c, 31c Via 31d Base 40 Adhesive layer 50

Claims

1. 1. An antenna system for use at frequencies above 1 GHz, comprising: a laminate including a plurality of high frequency transparent layers that are in contact with each other at their interfaces and each of which transmits high frequency waves; an antenna circuit board including a high-frequency insulating layer, the antenna circuit board being disposed adjacent to the high-frequency transmission layer that is the outermost layer of the laminate, and receiving high frequencies that have transmitted through the laminate, The relative dielectric constant of the n-th layer (n is an integer of 1 or more, and n=1 is the high frequency transmission layer through which the high frequency wave first passes when it is incident on the laminate, and the same applies below) of the plurality of high frequency transmission layers is ε ｎ , The wavelength of the high frequency incident on the laminate is λ, The thickness of the nth layer when the intensity of the reflected wave from the laminate is minimized is determined as the intensity of the composite wave of the reflected waves from the front surface, rear surface and each bonding interface of the laminate. ｎｍｉｎ Then, The thickness L of the nth layer ｎ L ｎmin ±λ / (10√ε ｎ ) range, Antenna system.

2. 10. The antenna system of claim 1, The intensity of the reflected wave from the laminate is the square of the amplitude As that satisfies the following formula (1): ２ That is, the antenna system. [Equation 1] where: ε ｎ is the relative dielectric constant of the nth layer constituting the laminate, L ｎ is the thickness of the nth layer constituting the laminate, θ ｎ is the refraction angle of the high frequency wave incident on the nth layer constituting the stack λ is the wavelength in air of the high frequency incident on the laminate, ε ０ is the relative permittivity of air, n is an integer of 1 or more represents A ０ =0、 Δx ０ =0、 L ０ =0、 θ ０ = the angle of incidence of the high frequency wave incident on the stack (first layer of the stack).

3. 3. The antenna system according to claim 1, wherein the intensity of the reflected wave from said laminate is determined when the angle of incidence of the high frequency wave on said laminate is 40 to 60 degrees.

4. 3. The antenna system according to claim 1, wherein the intensity of the reflected wave from said laminate is determined when the angle of incidence of the high frequency wave on said laminate is 45 degrees.

5. 3. The antenna system according to claim 1, wherein 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 relative dielectric constant lower than that of the glass layer, and when the transmittance adjustment layer is an n-th layer, the thickness of the transmittance adjustment layer is ｎmin ±λ / (10√ε ｎ ) range of antenna system.

6. 3. An antenna system according to claim 1 or 2, which constitutes a display device or a window pane of a vehicle or building.

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

8. 1. A method of manufacturing an antenna system for use at frequencies above 1 GHz, comprising: a laminate including a plurality of high frequency transparent layers that are in contact with each other at their interfaces and each of which transmits high frequency waves; an antenna circuit board including a high-frequency insulating layer, the antenna circuit board being disposed adjacent to the high-frequency transmission layer that is the outermost layer of the laminate, and receiving high frequencies that have transmitted through the laminate, The relative dielectric constant of the n-th layer (n is an integer of 1 or more) of the plurality of high frequency transmission layers is defined as ε ｎ , The wavelength of the high frequency incident on the laminate is λ, The thickness of the nth layer when the intensity of the reflected wave from the laminate is minimized is determined as the intensity of the composite wave of the reflected waves from the front surface, rear surface and each bonding interface of the laminate. ｎｍｉｎ Then, The thickness L of the nth layer ｎ L ｎmin ±λ / (10√ε ｎ ) range, A method for manufacturing an antenna system.

9. 9. A method of manufacturing an antenna system according to claim 8, comprising the steps of: the laminate includes a laminate precursor including at least one glass layer, and at least one transmittance adjusting layer made of a resin layer having a relative dielectric constant lower than that of the glass layer included in the laminate precursor, When the transmittance adjusting layer is the nth layer, the thickness of the transmittance adjusting layer is set to the L ｎmin ±λ / (10√ε ｎ ) the antenna circuit board is bonded to the laminate precursor via the transmittance adjustment layer, A method for manufacturing an antenna system.

10. 10. The method for manufacturing an antenna system according to claim 8 or 9, The intensity of the reflected wave from the laminate is the square of the amplitude As that satisfies the following formula (1): ２ A method for manufacturing an antenna system. [Equation 2] where: ε ｎ is the relative dielectric constant of the nth layer constituting the laminate, L ｎ is the thickness of the nth layer constituting the laminate, θ ｎ is the refraction angle of the high frequency wave incident on the nth layer constituting the stack λ is the wavelength in air of the high frequency incident on the laminate, ε ０ is the relative permittivity of air, n is an integer of 1 or more represents A ０ =0、 Δx ０ =0、 L ０ =0、 θ ０ = the angle of incidence of the high frequency wave incident on the stack (first layer of the stack).

11. 10. The method for manufacturing an antenna system according to claim 8, wherein the intensity of the reflected wave from the laminate is determined when the angle of incidence of the high frequency wave on the laminate is 40 to 60 degrees.

12. A method for designing an antenna system according to claim 1 or 2, comprising: The thickness L of the nth layer ｎ L ｎmin ±λ / (10√ε ｎ ) range, A method for designing an antenna system, comprising a step of adjusting the thickness of each layer constituting the laminate.

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

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