JP6207064B2 - Method for manufacturing antenna substrate - Google Patents

Description

  The present invention relates to an antenna substrate.

  Currently, high-speed and large-capacity wireless communication is possible. In such high-speed and large-capacity wireless communication, a high-frequency signal is transmitted by an antenna that transmits and receives information. Therefore, the antenna is required to have excellent transmission characteristics, specifically, low transmission delay and transmission loss.

  By the way, as a medium for performing high-speed and large-capacity wireless communication, an information communication terminal such as a mobile phone is generally used, but even in an automobile or the like, high-speed and large-capacity wireless communication is being performed in the same manner as an information mobile terminal. .

  As the antenna of the information communication terminal, for example, a planar monopole antenna in which a conductor layer is formed on a flexible base material is used. As an in-vehicle antenna, for example, a film antenna that is used by forming a conductor layer on the surface of an electrically insulating transparent base material and attaching it to a windshield or the like is used.

  In these antennas, it is necessary to use a material having a small relative dielectric constant (εr) and dielectric loss tangent (tan δ) as an insulating material in order to obtain the above transmission characteristics. As such an insulating material having a small relative dielectric constant (εr) and dielectric loss tangent (tan δ), a fluororesin such as polytetrafluoroethylene (PTFE) is known (Japanese Patent Laid-Open No. 2001-7466 and Japanese Patent No. 4296250). See the official gazette). However, since fluororesins such as PTFE have extremely low surface energy and are non-adhesive, there is a possibility that sufficient adhesion between the substrate and the conductor layer cannot be ensured.

  Therefore, as a means for improving adhesion, a method of forming a primer layer made of polyimide or a mixture of polyimide and polyethersulfone between a metal substrate and a coating layer made of a fluoropolymer has been considered (for example, a special feature). No. 2000-326441). As another means, a method of roughening the surface of a metal substrate by etching or the like has been proposed (for example, JP-A-3-207473).

JP 2001-7466 A Japanese Patent No. 4296250 JP 2000-326441 A JP-A-3-207473

  However, in the method of forming the primer layer, the relative dielectric constant of the coating layer may increase depending on the type of resin material forming the primer layer. On the other hand, in the method of roughening the surface of the metal substrate, transmission delay is likely to occur due to the skin effect, and transmission loss may increase due to increase in resistance attenuation or leakage attenuation. Therefore, when the above-described means for improving adhesion is applied to an antenna, the transmission characteristics of the base material (dielectric layer) may be deteriorated, and the conductor layer (antenna element layer) functioning as an antenna and the dielectric layer are joined. May deteriorate.

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide an antenna substrate that is excellent in high-frequency signal transmission characteristics and can sufficiently secure the bonding property between the dielectric layer and the antenna element layer. And

  The present invention is a flexible antenna substrate comprising a dielectric layer mainly composed of a fluororesin, and an antenna element layer laminated on at least one surface of the dielectric layer. The ten-point average roughness (Rz) of at least one surface is 4 μm or less.

  The antenna substrate of the present invention is excellent in high-frequency signal transmission characteristics and sufficiently secures the bondability between the dielectric layer and the antenna element. Therefore, the antenna substrate of the present invention can be suitably used as an in-vehicle antenna or an antenna of an information communication terminal such as a mobile phone.

1 is a plan view schematically showing an antenna substrate according to a first embodiment of the present invention. It is typical sectional drawing which follows the X1-X1 line | wire of FIG. It is sectional drawing equivalent to FIG. 2 which shows the antenna board | substrate which concerns on 2nd Embodiment of this invention typically. It is a top view which shows typically the antenna board | substrate which concerns on 3rd Embodiment of this invention. It is typical sectional drawing which follows the X2-X2 line | wire of FIG. It is typical sectional drawing which follows the X3-X3 line | wire of FIG.

[Description of Embodiment of the Present Invention]
The present invention is a flexible antenna substrate comprising a dielectric layer mainly composed of a fluororesin, and an antenna element layer laminated on at least one surface of the dielectric layer. The ten-point average roughness (Rz) of at least one surface is 0.2 μm or more and 4 μm or less.

  In the antenna substrate, since the dielectric layer is mainly composed of a fluororesin, the dielectric constant (εr) and the dielectric loss tangent (tan δ) of the dielectric layer can be reduced. In addition, by setting the ten-point average roughness (Rz) of at least one surface of the antenna element layer to 0.2 μm or more and 4 μm or less, it is possible to suppress transmission delay due to the skin effect while ensuring sufficient connectivity. In addition, transmission loss due to an increase in resistance attenuation and leakage attenuation can be suppressed. Therefore, the antenna substrate is excellent in high-frequency signal transmission characteristics and can cope with high-speed and large-capacity wireless communication. As a result, the antenna substrate can be suitably used as an in-vehicle antenna or an antenna of an information communication terminal such as a mobile phone.

  In addition, since the antenna substrate generally includes a dielectric layer mainly composed of a highly transparent fluororesin, transparency can be increased. On the other hand, since the antenna element layer is generally formed of a material with low transparency such as metal, the antenna element layer can be visually recognized as a pattern because the antenna element layer with low transparency is shaded. It becomes. Therefore, the antenna substrate is excellent in design. In addition, even when the antenna substrate is installed on a vehicle windshield or the like when it is applied for in-vehicle use, for example, the transparency of the antenna substrate can be increased, so that deterioration of the visual field caused by the antenna substrate is suppressed. it can.

  Furthermore, the fluororesin is generally excellent in weather resistance and chemical resistance. Therefore, since the antenna substrate can ensure weather resistance and chemical resistance by the dielectric layer, it can be suitably used as an outdoor or vehicle-mounted antenna.

  The relative dielectric constant (εr) of the fluororesin is preferably 3 or less, and the dielectric loss tangent (tan δ) is preferably 0.004 or less. Thus, when the dielectric loss tangent (tan δ) and the relative dielectric constant (εr) are within the above ranges, the transmission loss can be sufficiently reduced and a sufficient transmission speed can be obtained.

  The bending elastic modulus after the exposure test specified in JIS K 7350-2: 2008 of the dielectric layer is preferably 20 GPa or more. Thus, since the bending strength after the exposure test is in the above range, the mechanical strength of the antenna substrate can be sufficiently ensured even after the exposure test. Therefore, the antenna substrate can sufficiently ensure weather resistance, and as a result, the antenna substrate can be suitably used as an antenna that is used in an environment that is easily exposed to light, such as an in-vehicle or outdoor antenna. .

  The light transmittance of the dielectric layer is preferably 70% or more. Thus, when the light transmittance of the dielectric layer is within the above range, the antenna element layer can be more clearly shaded. For this reason, for example, it is possible to exhibit better design than when the antenna board is applied as an in-vehicle antenna, and it is possible to suppress deterioration of the visibility when the antenna board is installed on a vehicle windshield or the like.

  The light transmittance after the exposure test specified in JIS K 7350-2: 2008 of the dielectric layer is preferably 70% or more. Thus, since the light transmittance after the exposure test is within the above range, the transparency of the antenna substrate can be sufficiently ensured even after the exposure test. Therefore, the antenna substrate can sufficiently ensure weather resistance, and as a result, the antenna substrate can be suitably used as an antenna that is used in an environment that is easily exposed to light, such as an in-vehicle or outdoor antenna. .

  The number of bendings in the bending resistance test specified in JIS C 5016: 1994 of the antenna substrate is preferably 400 times or more. Thus, when the number of times of bending in the bending resistance test is within the above range, the flexibility of the antenna substrate is unlikely to deteriorate with time. Therefore, peeling of the antenna element layer and disconnection due to the deterioration of flexibility of the antenna substrate can be suppressed.

  The number of times until the wire breakage in the fold resistance test specified in JIS C 5016: 1994 of the antenna substrate is preferably 400 times or more. Thus, when the number of times until disconnection in the bending resistance test is within the above range, the flexibility of the antenna substrate is unlikely to deteriorate with time. Therefore, peeling of the antenna element layer and disconnection due to the deterioration of flexibility of the antenna substrate can be suppressed.

  The antenna substrate may have a chemical bond between the fluororesin of the dielectric layer and the antenna element layer. Thus, by having a chemical bond between the fluororesin of the dielectric layer and the antenna element layer, the bondability between the dielectric layer and the antenna element layer is increased, and the bonding strength can be improved.

  The chemical bond is preferably formed by ionizing radiation irradiation. According to such ionizing radiation irradiation, the chemical bond can be appropriately formed, so that the bondability between the antenna element layer and the dielectric layer can be further improved.

  The chemical bond may be formed via a coupling agent present at the interface between the dielectric layer and the antenna element layer. By interposing the coupling agent in this way, the chemical bond can be realized easily and reliably, and as a result, the bondability between the dielectric layer and the antenna element layer can be improved easily and reliably.

  As the coupling agent, a silane coupling agent having a functional group containing an N atom or an S atom is preferable. Thus, since the coupling agent is a silane coupling agent having a functional group containing an N atom or an S atom, the bondability between the dielectric layer and the antenna element layer can be further improved. Although the reason for this is not clear, the hydrolyzable group of the silane coupling agent is fixed to the antenna element layer by a silane coupling reaction, while the N atom or S of the silane coupling agent such as an amino group or a sulfide group is present. It is presumed that the bondability is improved by a chemical bond between a functional group containing atoms and a carbon radical site generated when the fluororesin that is a main component of the dielectric layer is radicalized.

  The dielectric layer preferably has a chemical bond formed by ionizing radiation irradiation between the molecules of the fluororesin. As described above, since the dielectric layer has a chemical bond between the molecules of the fluororesin, the mechanical strength of the dielectric layer can be improved, and the mechanical strength of the antenna substrate can be further improved.

  Examples of the fluororesin of the dielectric layer include tetrafluoroethylene / hexapropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), and tetrafluoroethylene. -Perfluorodioxole copolymer (TFE / PDD) is preferred. Such a fluororesin is considered to be a compound that easily generates fluorine radicals by electron beam irradiation or heating. Therefore, the antenna substrate includes the dielectric layer mainly composed of the exemplified fluororesin, so that the chemical bond can be appropriately formed. Therefore, the bondability between the dielectric layer and the antenna element layer is further improved. In addition, since the illustrated fluororesin is a material having a low dielectric loss tangent (tan δ) and relative dielectric constant (εr), the dielectric layer has such a fluororesin as a main component so that transmission loss, transmission speed, etc. The antenna substrate having excellent transmission characteristics can be obtained more easily.

  The antenna substrate may further include a cover film that covers the antenna element layer and contains a fluororesin as a main component. By providing such a cover film, deterioration of the antenna element layer due to oxidation or the like can be suppressed. In particular, the weather resistance and the like of the antenna substrate can be further improved because the cover film is mainly composed of a fluororesin having excellent weather resistance and chemical resistance. Further, since the cover film is mainly composed of a fluororesin having a high light transmittance, it is possible to suppress a decrease in the transmittance of the antenna substrate due to the provision of the cover film. Therefore, for example, when the antenna substrate is applied as an in-vehicle antenna, it is possible to suppress deterioration in design and visual field.

  The antenna substrate may be used as a vehicle-mounted antenna. In this way, by using the antenna board for vehicle mounting, for example, when the antenna board is installed on a windshield of a vehicle, a sufficient field of view can be secured without impairing the design.

  The antenna substrate may further include a wiring electrically connected to the antenna element layer and an electronic component electrically connected to at least one of the wiring and the antenna element. As described above, the antenna substrate further includes wiring and electronic components, whereby the antenna substrate can function as an electric circuit. Therefore, the antenna substrate can be suitably used as an antenna circuit for information communication terminals such as mobile phones.

  Here, the “fluororesin” refers to one in which at least one hydrogen atom bonded to the carbon atom constituting the repeating unit of the polymer chain is substituted with a fluorine atom or an organic group having a fluorine atom. The “main component” is a component having the largest content, for example, a component having a content of 50% by mass or more. The “ten-point average roughness (Rz)” is a value measured according to JIS B 0601: 1994, the evaluation length (l) is 3.2 mm, and the cut-off value (λc) is 0.00. The value is 8 mm. “Relative permittivity (εr)” and “dielectric loss tangent (tan δ)” are values measured in accordance with JIS C 2138: 2007. “Light transmittance” and “light transmittance after exposure test” are values measured according to JIS K 7375: 2008. “Bending strength after exposure test” is a value measured under the test conditions defined in JIS K 7171: 2008. “Chemical bond” refers to a covalent bond or a hydrogen bond.

[Details of the embodiment of the present invention]
Hereinafter, antenna substrates according to first to third embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
First, an antenna substrate 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  The antenna substrate 1 of FIGS. 1 and 2 can be suitably used as a high frequency antenna. The antenna substrate 1 includes a dielectric layer 10, an antenna element layer 11, and a cover lay 12.

  The antenna substrate 1 has a flat plate shape as a whole and has flexibility. Here, the flexibility of the antenna substrate 1 can be evaluated by, for example, bending resistance, folding resistance, and the like described below.

  The folding resistance of the antenna substrate 1 can be evaluated as the number of times until the sample (antenna substrate 1) is bent at a rate of 170 times per minute with a tension of 4.9 N and the sample is disconnected. The number of times until the antenna substrate 1 is disconnected is preferably 400 times or more, and more preferably 500 times or more. The number of disconnections until the antenna substrate 1 is disconnected is the number of times measured in accordance with JIS C 5016 “Flexible Printed Wiring Board Test Method (8.7 Folding Resistance)”: 1994. Measurement of 10 samples Defined as the average of the results.

<Antenna element layer>
The antenna element layer 11 is a part that transmits and receives information. The antenna element layer 11 is laminated on one surface of the dielectric layer 10 and is patterned in a comb shape in plan view. Such an antenna element layer 11 is formed, for example, by etching a metal layer laminated on one surface of the dielectric layer 10. The metal layer can be formed of a conductive material, but a pattern having a desired shape can be easily and reliably formed by using a copper foil, an aluminum foil, or the like. Moreover, it is preferable that the antenna element layer 11 includes a rust prevention treatment layer.

  The impedance of the circuit including the antenna element layer 11 may be set as appropriate according to the specifications of the antenna substrate 1. The lower limit of the impedance is usually 10Ω, and preferably 30Ω. The upper limit of the impedance is usually 300Ω, and preferably 120Ω.

  The transmission loss in the 50Ω system at a frequency of 10 GHz of the antenna element layer 11 is preferably 0.230 dB / cm or less, and more preferably 0.228 dB / cm or less. Thereby, the antenna board | substrate 1 can be used suitably for transmission of a high frequency area | region.

  The transmission loss in the 50Ω system at a frequency of 100 GHz of the antenna element layer 11 is preferably 3.10 dB / cm or less, more preferably 3.05 dB / cm or less, and further preferably 3.00 dB / cm or less. Thereby, the antenna board | substrate 1 can be used suitably also for transmission of a higher high frequency area | region of 100 GHz or more.

  The upper limit of the ten-point average roughness (Rz) of at least one surface of the dielectric layer 10 in the antenna element layer 11 is 4 μm, preferably 3 μm, more preferably 2 μm. The lower limit of the ten-point average roughness (Rz) of the dielectric layer 10 is 0.2 μm, preferably 0.5 μm. By setting the surface roughness of the antenna element layer 11 in this way, the bonding strength is ensured by chemical bonding with the fluororesin of the dielectric layer 10 described later while suppressing deterioration of the bonding property, and the transmission effect is improved by the skin effect. Reduction can be suppressed.

  The lower limit of the average thickness of the antenna element layer 11 is preferably 1 μm, more preferably 5 μm, and even more preferably 10 μm. If the average thickness of the antenna element layer 11 is less than the lower limit, the antenna element layer 11 may be easily disconnected. The upper limit of the average thickness of the antenna element layer 11 is preferably 100 μm, more preferably 50 μm, and even more preferably 30 μm. If the average thickness of the antenna element layer 11 exceeds the upper limit, the antenna substrate 1 may not be able to ensure sufficient flexibility.

  In addition, it is preferable that the antenna element layer 11 has a substantially uniform thickness at an arbitrary position in the planar direction. Here, “substantially uniform” means that the error is within 40% with respect to the average thickness, and “average thickness” is defined as an average value of measured values at arbitrary 10 points. In the following, other elements are defined in the same manner when referred to as “average thickness”.

(Anti-rust treatment layer)
The antenna element layer 11 preferably includes a rust prevention treatment layer as described above. This rust prevention treatment layer suppresses a decrease in bonding strength due to oxidation of the surface of the antenna element layer 11. The rust prevention treatment layer preferably contains cobalt, chromium or copper, and more preferably contains cobalt or a cobalt alloy as a main component. The antirust treatment layer may be formed as a single layer or a plurality of layers. The antirust treatment layer may be formed as a plating layer. This plating layer is formed as a single metal plating layer or an alloy plating layer. The metal constituting the single metal plating layer is preferably cobalt. Examples of the alloy constituting the alloy plating layer include cobalt alloys such as cobalt-molybdenum, cobalt-nickel-tungsten, and cobalt-nickel-germanium.

  The lower limit of the average thickness of the rust preventive layer is preferably 0.5 nm, more preferably 1 nm, and even more preferably 1.5 nm. If the average thickness of the rust-proofing layer is less than the lower limit, oxidation of the antenna element layer 11 may not be sufficiently suppressed. On the other hand, the upper limit of the average thickness is preferably 50 nm, more preferably 40 nm, and even more preferably 35 nm. If the average thickness of the rust-proofing layer exceeds the upper limit, it may not be possible to obtain an antioxidant effect commensurate with the increase in thickness.

<Dielectric layer>
The dielectric layer 10 is a layer on which the antenna element layer 11 is laminated. This dielectric layer 10 has a fluororesin as a main component. The dielectric layer 10 may contain an optional component as required in addition to the fluororesin.

  The fluororesin of the dielectric layer 10 preferably forms a chemical bond with one surface of the antenna element layer 11. As this chemical bond, the antenna element layer 11 is directly formed between the fluororesin of the dielectric layer 10 and the coupling agent interposed between the antenna element layer 11 and the fluororesin of the dielectric layer 10 causes the antenna to Examples include a form formed between the element layer 11 and the fluororesin of the dielectric layer 10 and a form in which these two forms are combined. The dielectric layer 10 preferably has a chemical bond formed between the molecules of the fluororesin.

(Coupling agent)
The coupling agent is used to form a chemical bond between the antenna element layer 11 and the fluororesin of the dielectric layer 10. As this coupling agent, a silane coupling agent is preferable, and among them, a silane coupling agent having a functional group containing an N atom or an S atom (hereinafter also referred to as “reactive functional group”) is more preferable. Silane coupling agent having a reactive functional group, hydrolyzable group _{(-OCH 3, -OC 2 H 5} , -OCOCH 3 , etc.) silane on one surface of the antenna element layer 11 by is hydrolyzed cup Fixed by ring reaction. On the other hand, the silane coupling agent is presumed to be chemically bonded to the dielectric layer 10 at the reactive functional group as described later.

  Examples of the functional group containing an N atom include an amino group and a ureido group.

  Examples of the silane coupling agent having a functional group containing an N atom include aminoalkoxysilane, ureidoalkoxysilane, and derivatives thereof.

  Examples of the aminoalkoxysilane include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, and N-2- (aminoethyl) -3. -Aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane and the like.

  Examples of aminoethoxysilane derivatives include ketimines such as 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, and N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxy. Examples thereof include salts of silane coupling agents such as silane acetate.

  Examples of the ureidoalkoxysilane include 3-ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, and γ- (2-ureidoethyl) aminopropyltrimethoxysilane.

  Examples of the functional group containing an S atom include a mercapto group and a sulfide group.

  Examples of the silane coupling agent having a functional group containing an S atom include mercaptoalkoxysilane, sulfide alkoxysilane, and derivatives thereof.

  Examples of mercaptoalkoxysilanes include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyl (dimethoxy) methylsilane, mercaptoorganyl (alkoxysilane), and the like.

  Examples of the sulfide alkoxysilane include bis (3- (triethoxysilyl) propyl) tetrasulfide and bis (3- (triethoxysilyl) propyl) disulfide.

  As said silane coupling agent, what introduce | transduced the modification group may be used. As the modifying group, a phenyl group is preferable.

  Examples of the silane coupling agent include 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and bis ( 3- (Triethoxysilyl) propyl) tetrasulfide is preferred.

  As the coupling agent, another coupling agent can be used instead of or in addition to the silane coupling agent having a functional group containing an N atom or an S atom. The other coupling agent preferably contains a functional group reactive to the fluororesin of the dielectric layer 10 or a radical thereof, and a functional group that can be chemically bonded to the antenna element layer 11 or the antirust treatment layer. For example, a titanium-based coupling agent can be used.

  Examples of the titanium coupling agent include isopropyl triisostearoyl titanate, isopropyl tristearoyl titanate, isopropyl trioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri ( Dioctyl phosphate) titanate, isopropyl tricumyl phenyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, isopropyl tri (n-aminoethyl-aminoethyl) titanate, tetraisopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phos) Fight) Titanate, Tetra (2 2-diallyloxymethyl-1-butyl) bis (ditridecyl) phosphite titanate, dicumylphenyloxyacetate titanate, bis (dioctylpyrophosphate) oxyacetate titanate, diisostearoylethylene titanate, bis (dioctylpaurophosphate) ethylene titanate, Bis (dioctyl paurophosphate) diisopropyl titanate, tetramethyl orthotitanate, tetraethyl orthotitanate, tetrapropyl orthotitanate, tetraisopropyl tetraethyl orthotitanate, tetrabutyl orthotitanate, butyl polytitanate, tetraisobutyl orthotitanate, 2-ethylhexyl titanate, stearyl titanate , Cresyl titanate monomer, cresyl titanate Terpolymer, diisopropoxy-bis- (2,4-pentadionate) titanium (IV), diisopropyl-bis-triethanolamino titanate, octylene glycol titanate, titanium lactate, acetoacetic estiltitanate, diisopropoxybis 8acetylacetonato) titanium, di-n-butoxybis (triethanolaluminate) titanium, dihydroxybis (lactato) titanium, titanium-isopropoxyoctylene glycolate, tetra-n-butoxytitanium polymer, tri-n-butoxytitanium Monostearate polymer, butyl titanate dimer, titanium acetylacetonate, polytitanium titanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, Emissions lactate ethyl ester, titanium triethanolaminate, polyhydroxy titanium stearate.

  The upper limit of the relative dielectric constant (εr) of the dielectric layer 10 is preferably 3, more preferably 2.7, even more preferably 2.5, and particularly preferably 2.3. If the relative dielectric constant (εr) exceeds the above upper limit, the dielectric loss tangent (tan δ) increases, and there is a possibility that the transmission loss cannot be sufficiently reduced, and there is a possibility that a sufficient transmission speed cannot be obtained. The lower limit of the relative dielectric constant (εr) of the dielectric layer 10 is not particularly limited, but 1.2 is preferable. When the relative dielectric constant (εr) is less than the lower limit, it is difficult to ensure the dimensional stability of the dielectric layer 10. In particular, when the relative dielectric constant is reduced by foaming, the elastic modulus is too low, which may make it difficult to process and convey.

  The upper limit of the dielectric loss tangent (tan δ) of the dielectric layer 10 is preferably 0.004, more preferably 0.0035, and still more preferably 0.003. If this dielectric loss tangent (tan δ) exceeds the above upper limit, the transmission loss may not be sufficiently reduced, and a sufficient transmission rate may not be obtained. The dielectric loss tangent (tan δ) of the dielectric layer 10 is not particularly limited, and the dielectric loss tangent (tan δ) is preferably as small as possible.

  The lower limit of the flexural modulus after the exposure test of the dielectric layer 10 is preferably 20 GPa, more preferably 30 GPa, and even more preferably 40 GPa. If the bending strength of the dielectric layer 10 after the exposure test is less than the above lower limit, the strength as the antenna substrate 1 may not be sufficient, and sufficient weather resistance may not be ensured. The upper limit of the flexural modulus after the exposure test of the dielectric layer 10 is preferably 80 GPa, more preferably 70 GPa, and even more preferably 60 GPa. If the flexural modulus of the dielectric layer 10 after the exposure test exceeds the upper limit, the flexibility of the antenna substrate 1 cannot be sufficiently ensured. For example, when the antenna substrate 1 is applied for in-vehicle use, a windshield, etc. There is a possibility that it will be easy to peel off from the sticking part.

  As a minimum of the light transmittance of dielectric layer 10, 70% is preferred, 75% is more preferred, and 80% is still more preferred. If the light transmittance of the dielectric layer 10 is less than the above lower limit, the light transmittance as the antenna substrate 1 is lowered. For example, the design when the antenna substrate 1 is applied as an in-vehicle antenna is impaired, and the field of view is reduced. May get worse. There is no restriction | limiting in particular about the upper limit of the light transmittance of the said dielectric layer 10, It is preferable that it is closer to 100%, 95% is more preferable from viewpoints of material cost, manufacturability, etc., and 85% is further more preferable.

  The lower limit of the light transmittance after the exposure test of the dielectric layer 10 is preferably 70%, more preferably 75%, and still more preferably 80%. If the light transmittance after the exposure test of the dielectric layer 10 is less than the lower limit, sufficient weather resistance may not be ensured. For example, the appearance of the antenna substrate 1 when the antenna substrate 1 is applied as a vehicle-mounted antenna is sufficiently deteriorated. May not be able to be suppressed, and the appearance of the antenna substrate 1 may be deteriorated. There is no restriction | limiting in particular about the upper limit of the light transmittance of the said dielectric layer 10, It is preferable that it is closer to 100%, 95% is more preferable from viewpoints of material cost, manufacturability, etc., and 85% is further more preferable.

  As a minimum of average thickness of dielectric layer 10, 5 micrometers is preferred, 7 micrometers is more preferred, and 10 micrometers is still more preferred. If the average thickness of the dielectric layer 10 is less than the above lower limit, the dielectric loss tangent becomes large and there is a possibility that the transmission loss cannot be sufficiently reduced, and there is a possibility that a sufficient transmission speed cannot be obtained. Work may be difficult. The upper limit of the average thickness of the dielectric layer 10 is preferably 125 μm, more preferably 100 μm, and even more preferably 50 μm. If the average thickness of the dielectric layer 10 exceeds the upper limit, the thicknesses of the dielectric layer 10 and the antenna substrate 1 may become unnecessarily large, the material cost of the dielectric layer 10 may increase, and sufficient flexibility can be obtained. There is a risk of not being able to.

(Fluorine resin)
A fluororesin is one in which at least one hydrogen atom bonded to a carbon atom constituting a repeating unit of a polymer chain is substituted with a fluorine atom or an organic group having a fluorine atom (hereinafter also referred to as “fluorine atom-containing group”). Say. The fluorine atom-containing group is a group in which at least one hydrogen atom in a linear, branched or cyclic organic group is substituted with a fluorine atom. For example, a fluoroalkyl group, a fluoroalkoxy group, a fluoropolyether group, etc. Can be mentioned.

  The “fluoroalkyl group” means an alkyl group in which at least one hydrogen atom is substituted with a fluorine atom, and includes a “perfluoroalkyl group”. Specifically, a “fluoroalkyl group” is a group in which all hydrogen atoms of an alkyl group are substituted with fluorine atoms, and all hydrogen atoms other than one hydrogen atom at the end of the alkyl group are substituted with fluorine atoms. Group and the like.

  The “fluoroalkoxy group” means an alkoxy group in which at least one hydrogen atom is substituted with a fluorine atom, and includes a “perfluoroalkoxy group”. Specifically, a “fluoroalkoxy group” is a group in which all hydrogen atoms of an alkoxy group are substituted with fluorine atoms, and all hydrogen atoms other than one hydrogen atom at the end of the alkoxy group are substituted with fluorine atoms. Group and the like.

  The “fluoropolyether group” is a monovalent group having a plurality of alkylene oxide chains as repeating units and having an alkyl group or a hydrogen atom at the terminal, and the alkylene oxide chain and / or the terminal alkyl group or A monovalent group having a group in which at least one hydrogen atom in a hydrogen atom is substituted with a fluorine atom. “Fluoropolyether group” includes “perfluoropolyether group” having a plurality of perfluoroalkylene oxide chains as repeating units.

  Examples of fluororesins include tetrafluoroethylene / hexapropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or tetrafluoroethylene-perfluorodiode. A xol copolymer (TFE / PDD) is preferred.

(Optional component)
Examples of the optional components of the dielectric layer 10 include engineering plastics, flame retardants, flame retardant aids, pigments, antioxidants, reflection-imparting agents, masking agents, lubricants, processing stabilizers, plasticizers, and foaming agents.

  As said engineering plastic, it can select and use from a well-known thing according to the characteristic calculated | required by the dielectric layer 10, Typically, aromatic polyether ketone can be used.

  This aromatic polyetherketone has a structure in which the benzene rings are bonded to the para position and the benzene rings are connected to each other by a rigid ketone bond (-C = O) or a flexible ether bond (-O-). Resin. As the aromatic polyether ketone, for example, ether ether ketone (PEEK) having a structural unit in which an ether bond, a benzene ring, an ether bond, a benzene ring, a ketone bond and a benzene ring are arranged in this order, an ether bond, a benzene ring, Examples include polyether ketone (PEK) having a structural unit in which a ketone bond and a benzene ring are arranged in this order. Among them, PEEK is preferable as the aromatic polyether ketone. Since such an aromatic polyether ketone is excellent in wear resistance, heat resistance, insulation, workability, etc., the dielectric layer 10 containing the aromatic polyether ketone is bonded to the antenna element layer 11. Etc.

  A commercially available product can be used as the aromatic polyether ketone such as PEEK. As aromatic polyether ketones, those of various grades are commercially available, and a single grade of aromatic polyether ketone that is commercially available may be used alone, or multiple grades of aromatic polyether ketone. A ketone may be used in combination, or a modified aromatic polyether ketone may be used.

  The content of the engineering plastic is not particularly limited. As a minimum of content of engineering plastics, it is 10 normally by a total mass ratio with a fluororesin, 20 is preferable and 35 is more preferable. The upper limit of the content is usually 50 and preferably 45 or less. If the content of the engineering plastic is less than the above lower limit, the characteristics of the dielectric layer 10 may not be sufficiently improved. On the other hand, if the content of the engineering plastic exceeds the above upper limit, the advantageous characteristics of the fluororesin may not be sufficiently exhibited.

  Various known flame retardants can be used, and examples thereof include halogen flame retardants such as bromine flame retardants and chlorine flame retardants.

  Various known flame retardant aids can be used, and examples include antimony trioxide.

  Various known pigments can be used as the pigment, and examples thereof include titanium oxide.

  Various known antioxidants can be used as the antioxidant, and examples thereof include phenolic antioxidants.

  As the reflection imparting agent, various known ones can be used, and examples thereof include titanium oxide.

  The dielectric layer 10 is preferably irradiated with ionizing radiation. The ionizing radiation irradiation is preferably performed under heating. By irradiating the dielectric layer 10 with ionizing radiation, the fluororesin is radicalized.

  Thus, when the above-mentioned coupling agent is used because the fluororesin is radicalized, it is considered that this coupling agent and the radical of the fluororesin are chemically bonded. Specifically, it is presumed that the coupling agent is chemically bonded to the fluororesin by chemically bonding the reactive functional group of the coupling agent to the radical portion. As described above, the coupling agent is chemically bonded to the radical portion of the fluororesin, and the coupling agent is chemically bonded to the antenna element layer 11 as described above, whereby the fluororesin of the dielectric layer 10 and the antenna element layer 11 are A chemical bond with a coupling agent interposed between them is formed. As a result, the antenna substrate 1 can increase the bonding strength between the dielectric layer 10 and the antenna element layer 11.

  Here, it is presumed that the silane coupling agent is present between the antenna element layer 11 and the dielectric layer 10 in a cocoon order. Therefore, the coupling agent hardly affects the surface properties of the antenna element layer 11 and the surface of the antenna element layer 11 is not roughened. Therefore, the signal transmission performance is hardly deteriorated by the coupling agent. It is thought that it does not occur.

  On the other hand, when the above coupling agent is not used, when the fluororesin is radicalized by ionizing radiation irradiation or the like, the radical portion of the fluororesin forms a chemical bond with the antenna element layer 11. Therefore, by forming a chemical bond between the fluororesin and the surface of the antenna element layer 11, the chemical bond between the dielectric layer 10 and the antenna element layer 11 can be achieved even when the coupling agent is not used. It is possible to increase the bonding strength.

  In addition, when the fluororesin is radicalized, a chemical bond is formed between the molecules of the fluororesin molecule, and when the dielectric layer 10 includes an engineering plastic such as a PEEK resin, a chemical bond is formed between the fluororesin and the engineering plastic. A bond is formed. Bonds between molecules of fluororesin molecules by chemical bonds, bonds between fluororesins and engineering plastics are covalent bonds or hydrogen bonds, and these chemical bonds are stronger than intermolecular bonds (F—F bonds) of fluororesins. . Therefore, in the antenna substrate 1, chemical bonds are formed between the fluorine resin molecules, or chemical bonds are formed between the fluorine resin and the engineering plastic, thereby improving the mechanical strength of the dielectric layer 10. Is possible.

  Here, examples of the ionizing radiation include charged particle beams such as electron beams and high-energy ion beams, high-energy electromagnetic waves such as γ-rays and X-rays, and neutral beams. Among these, electron beams are preferable. This is because the electron beam generator is relatively inexpensive, a high output electron beam can be obtained, and the degree of radical generation, that is, the degree of chemical bond formation, can be easily controlled.

  As the irradiation dose of the ionizing radiation, an effect can be obtained in a wide range, and an arbitrary irradiation line may be selected. However, about 50 KGy to 800 KGy is preferable. When the irradiation dose of ionizing radiation is less than the above lower limit, radicalization becomes insufficient and the effect of improving the mechanical strength of the dielectric layer 10 and the effect of improving the bonding strength between the antenna element layer 11 and the dielectric layer 10 are sufficient. May not be obtained. On the other hand, when the irradiation dose of ionizing radiation exceeds the above upper limit, decomposition of the resin component (breaking of the polymer main chain) becomes excessive, and the mechanical strength of the dielectric layer 10 may be reduced. On the other hand, when the irradiation dose is 50 KGy to 800 kGy, radicalization can be sufficiently advanced and the resin component is hardly decomposed, and sufficient mechanical strength, bonding strength, and the like can be obtained.

  The ionizing radiation irradiation is preferably performed in a state of heating the dielectric layer 10 or the resin material immediately before forming the dielectric layer 10 in a low oxygen or oxygen-free atmosphere.

  By performing ionizing radiation irradiation in a low-oxygen or oxygen-free atmosphere, the bonding strength of the dielectric layer 10 to the antenna element layer 11 can be improved. Specifically, if the oxygen concentration is less than 1000 ppm, an effect of improving the bonding strength can be obtained. When the oxygen concentration is 500 ppm or less, a remarkable effect of improving the bonding strength is obtained, and when the oxygen concentration is 100 ppm or less, a more remarkable effect of improving the bonding strength is obtained. From the viewpoint of stability and ease of control of the oxygen concentration during ionizing radiation irradiation, the oxygen concentration is preferably 10 ppm or less.

  The heating temperature during irradiation with ionizing radiation is preferably equal to or higher than the melting point of the fluororesin that is the main component of the dielectric layer 10. The heating temperature is preferably 80 ° C. or higher than the melting point, more preferably 40 ° C. or lower than the melting point. For example, when the main component of the dielectric layer 10 is FEP, since the melting point of FEP is about 270 ° C., the heating temperature is preferably 270 ° C. to 350 ° C. By performing the heating temperature at a temperature higher than the melting point of the resin, radicalization of the fluororesin and formation of chemical bonds can be appropriately promoted. On the other hand, by setting the upper limit of the heating temperature to not more than 80 ° C. higher than the melting point of the fluororesin, thermal decomposition of the fluororesin (breaking of the polymer main chain) can be suppressed, and the mechanical strength and bonding of the dielectric layer 10 can be suppressed. A decrease in strength can be suppressed.

  In addition, when the dielectric layer 10 contains engineering plastic, the heating temperature at the time of ionizing radiation irradiation has preferable melting | fusing point or more of a fluororesin and engineering plastic. By setting the heating temperature in this way, a chemical bond can be formed between the fluororesin and the engineering plastic, and the mechanical strength and the like of the dielectric layer 10 can be further increased.

<Coverlay>
The cover lay 12 protects the antenna element layer 11 from external force and moisture. The cover lay 12 includes a cover film 13 and an adhesive layer 14.

(Cover film)
The cover film 13 is laminated on the dielectric layer 10 and the antenna element layer 11 via the adhesive layer 14. The cover film 13 is preferably highly transparent when the antenna substrate 1 is used as an in-vehicle antenna. As the transparency of the cover film 13, it is preferable to have the same light transmittance as that of the dielectric layer 10.

  The main component of the cover film 13 is preferably a fluororesin. Examples of such a fluororesin include those similar to those exemplified as the main component of the dielectric layer 10. Thus, the transparency of the cover film 13 is securable because the cover film 13 has a fluororesin as a main component.

  The average thickness of the cover film 13 is usually 10 μm or more and 30 μm or less. There exists a possibility that insulation may become inadequate that the average thickness of the cover film 13 is less than the said range. On the other hand, when the average thickness of the cover film 13 exceeds the above range, the flexibility of the antenna substrate 1 may be impaired.

(Adhesive layer)
The adhesive layer 14 fixes the cover film 13 to the dielectric layer 10. The material of the adhesive layer 14 is not particularly limited, but is preferably excellent in flexibility and heat resistance, and examples thereof include polyamide resin, epoxy resin, butyral resin, and acrylic resin. In particular, acrylic resin is more preferable in applications where transparency is required, such as when the antenna substrate 1 is used as an in-vehicle antenna.

  Although it does not specifically limit as average thickness of the contact bonding layer 14, 20 micrometers or more and 30 micrometers or less are preferable. If the average thickness of the adhesive layer 14 is less than the lower limit, the bonding strength may be insufficient. If the average thickness of the adhesive layer 14 exceeds the above upper limit, the flexibility of the antenna substrate 1 may not be sufficiently secured.

  As described above, since the antenna substrate 1 includes the cover lay 12, deterioration due to oxidation or the like of the antenna element layer 11 can be suppressed. Moreover, the fall of the light transmittance of the antenna board | substrate 1 can be suppressed because the cover film 13 has a fluororesin as a main component. Similarly, by using a highly transparent resin such as an acrylic resin as the adhesive layer 14, it is possible to suppress a decrease in light transmittance of the antenna substrate 1. Therefore, for example, when the antenna substrate 1 is applied as a vehicle-mounted antenna and is installed on a windshield of a vehicle or the like, deterioration in design of the antenna substrate 1 and deterioration in visual field can be suppressed.

[Antenna substrate manufacturing method]
The antenna substrate 1 includes, for example, (1) a rust prevention treatment layer forming step (2) a coating step,
(3) Drying step (4) Adhesion step,
(5) It can be obtained by a manufacturing method including a patterning step and (6) a coverlay lamination step.

<(1) Rust prevention treatment layer formation process>
The antirust treatment layer forming step is a step of forming an antirust treatment layer on all or a part of at least one surface of a conductor film such as a metal foil for forming the antenna element layer 11. This rust prevention treatment layer formation process is performed by applying a rust prevention solution containing metal ions to all or a part of at least one surface of the conductor film and then drying the rust prevention solution. As metal ions, cobalt ions, chromium ions and copper ions are preferable, and cobalt ions are more preferable. As a coating method of the rust preventive solution, various known methods can be adopted. Examples thereof include a method of immersing the conductor film in the rust preventive solution and a method of applying the rust preventive solution to the conductor film. The drying of the rust preventive solution may be either natural drying or forced drying. By drying the rust preventive solution in this manner, a metal oxide rust preventive treatment layer derived from metal ions in the rust preventive solution is formed on all or part of at least one surface of the conductor film.

  The antirust treatment layer forming step may be performed by a plating method such as a water-soluble electrolytic plating method. When the plating method is employed, the rust prevention treatment layer is preferably formed as a single metal plating layer or an alloy plating layer and includes cobalt.

<(2) Coating process>
In the coating step, a composition containing a silane coupling agent (hereinafter also referred to as “coupling agent-containing composition”) is applied to the conductor film (antenna element layer 11), and the above-described coupling is applied to the conductor film. This is done to chemically bond the agent.

  The method for coating the coupling agent-containing composition in the coating step is not particularly limited. For example, a method of immersing the conductor film in the coupling agent-containing composition, a method of applying the coupling agent-containing composition to the conductor film A method of immersing the conductor film in the coupling agent-containing composition is preferable.

  When the method of immersing the conductor film in the coupling agent-containing composition is employed, the temperature of the coupling agent-containing composition is usually 20 ° C. to 40 ° C., and the immersion time is 10 seconds to 30 seconds.

(Coupling agent-containing composition)
The coupling agent-containing composition contains a coupling agent such as the above silane coupling agent and a solvent, and may contain other optional components as long as the effects of the present invention are not impaired.

  As a minimum of content of a coupling agent in a coupling agent content composition, 0.1 mass% is preferred and 0.5 mass% is more preferred. If the content of the coupling agent is less than the lower limit, the bondability between the dielectric layer 10 and the antenna element layer 11 may not be sufficiently improved. On the other hand, as an upper limit of content of a coupling agent, 5 mass% is preferable, 3 mass% is more preferable, and 1.5 mass% is further more preferable. When the content of the coupling agent exceeds the above upper limit, the coupling agent tends to aggregate and it may be difficult to prepare the coupling agent-containing composition.

(solvent)
The solvent is not particularly limited as long as it can dissolve the coupling agent, and examples thereof include alcohols such as methanol and ethanol, toluene, hexane, and water. However, as the solvent, ethanol is preferable for the ethoxysilane-based aminosilane coupling agent and methanol is preferable for the methoxysilane-based aminosilane coupling agent from the viewpoint of storage stability.

(Optional component)
Optional components include antioxidants, viscosity modifiers, surfactants, and the like. Examples of the antioxidant include iron, sugar, reductone, sodium sulfite, ascorbic acid (vitamin C) and the like.

<(3) Drying process>
A drying process is performed in order to dry the said coupling agent containing composition. Although this drying process may be performed by either natural drying or forced drying, natural drying is preferred. Moreover, it is preferable to heat-process a conductor film after drying a coupling agent containing composition. By performing the heat treatment, the coupling agent can be more reliably fixed to all or a part of at least one surface of the conductor film. The heat treatment can be performed, for example, by heating at 100 to 130 ° C. for 1 to 10 minutes in a thermostatic bath.

<(4) Adhesion process>
The adhering step is a step of adhering the conductor film to at least the composition coated surface of the dielectric layer 10 containing a fluororesin as a main component. This bonding step is performed, for example, by applying pressure and heating in a state where the conductor film (antenna element layer 11) is placed on one surface of the dielectric layer 10. The bonding step can be performed using a known hot press machine. The bonding step is preferably performed by vacuum pressing under a low oxygen concentration, for example, in a nitrogen atmosphere. By performing the bonding step under a low oxygen concentration, oxidation of one surface (bonding surface) of the conductor film (antenna element layer 11) can be suppressed, and a decrease in adhesion can be suppressed.

  Here, by appropriately selecting the pressure heating conditions in the bonding step, the terminal or side chain of the fluororesin that is the main component of the dielectric layer 10 can be decomposed to radicalize part of the fluororesin. The heating temperature is preferably at least the crystal melting point of the fluororesin that is the main component of the dielectric layer 10, more preferably at a temperature 30 ° C higher than the crystal melting point, and more preferably at least 50 ° C higher than the crystal melting point. For example, when the main component of the dielectric layer 10 is FEP, since the crystal melting point of this FEP is about 270 ° C., the heating temperature is preferably 270 ° C. or higher, more preferably 300 ° C. or higher, and further preferably 320 ° C. or higher. By heating the dielectric layer 10 at such a heating temperature, radicals of fluororesin can be effectively generated. However, if the heating temperature is too high, the fluororesin itself may be deteriorated, so the upper limit of the heating temperature is preferably 600 ° C, more preferably 500 ° C.

  In this bonding step, other known radical generation methods such as ionizing radiation irradiation may be used in combination with the pressure heating. Examples of ionizing radiation irradiation include γ-ray irradiation treatment. By performing ionizing radiation irradiation under heating in this way, radicalization of the fluororesin can be generated more effectively while suppressing deterioration of the fluororesin. Therefore, by performing ionizing radiation irradiation under heating, radicalization of the fluororesin and formation of chemical bonds can be promoted, and the bondability between the dielectric layer 10 and the antenna element layer 11 can be further improved.

  Further, the ionizing radiation irradiation is not necessarily performed in the bonding process, and may be performed at the same time when the dielectric layer 10 is formed, or may be performed after the dielectric layer 10 is formed and before the bonding process is performed. You may perform after an adhesion process. Further, the irradiation with ionizing radiation is not necessarily performed under heating, and radicalization of the fluororesin may be performed only by irradiation with ionizing radiation.

<(5) Patterning step>
The patterning step is a step of forming the antenna element layer 11 having a predetermined pattern on the surface of the dielectric layer 10. This patterning step is performed after the conductor films are stacked, and can be performed by, for example, a known etching method.

  Note that the patterning step may be performed before the bonding step. This patterning step may be performed by, for example, a method of bonding the conductive film to the dielectric layer 10 after patterning the conductive film formed on the surface of the release film, or a method of laminating a punched conductive film.

<(6) Coverlay lamination process>
The cover lay stacking step is a step of stacking the cover lay 12 so as to cover the antenna element layer 11. In this cover lay laminating step, for example, the cover lay 12 in which the adhesive layer 14 is previously formed on the cover film 13 is placed so as to cover the antenna element layer 11, and then the dielectric layer 10 is pressed via the adhesive layer 14 by pressure heating. This is done by fixing the cover film 13 to the surface. Thereby, the cover film 13 is fixed to the dielectric layer 10 via the adhesive layer 14.

  The pressure heating conditions may be appropriately determined depending on the constituent material of the adhesive layer 14 used for the coverlay 12.

<Advantages>
The antenna substrate 1 can reduce the relative dielectric constant (εr) and the dielectric loss tangent (tan δ) of the dielectric layer 10 because the dielectric layer 10 contains a fluororesin as a main component. Further, by setting the ten-point average roughness (Rz) of at least one surface of the antenna element layer 11 to 0.2 μm or more and 4 μm or less, generation of transmission delay due to the skin effect is suppressed while sufficiently securing the bonding property. In addition, transmission loss due to increased resistance attenuation and leakage attenuation can be reduced. Therefore, the antenna substrate 1 is excellent in high-frequency signal transmission characteristics and can cope with high-speed and large-capacity wireless communication. As a result, the antenna substrate 1 can be suitably used as an antenna for a vehicle-mounted antenna or an information communication terminal such as a mobile phone.

  Moreover, since the antenna substrate 1 includes the dielectric layer 10 whose main component is a highly transparent fluororesin, the transparency can be increased. On the other hand, since the antenna element layer 11 is formed of a generally low-transparent material such as a metal, the antenna substrate 1 is shaded by the pattern of the antenna element layer 11 having a low transparency. It can be visually recognized as a pattern. Therefore, the antenna substrate 1 has excellent design properties. In addition, even when the antenna substrate 1 is installed on a vehicle windshield or the like when applied to a vehicle, for example, the transparency of the antenna substrate 1 can be increased. Deterioration can be suppressed.

  Furthermore, the fluororesin is generally excellent in weather resistance and chemical resistance. Therefore, since the antenna substrate 1 can ensure weather resistance and chemical resistance by the dielectric layer 10 and the cover film 13, it can be suitably used as an outdoor or vehicle-mounted antenna.

Second Embodiment
Next, an antenna substrate according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same elements as those of the antenna substrate 1 of FIGS. 1 and 2 are denoted by the same reference numerals, and redundant description below is omitted.

  The antenna substrate 2 in FIG. 3 is obtained by stacking a ground layer 21 and a coverlay 24 on the other surface of the dielectric layer 10 in the antenna substrate 1 in FIGS. 1 and 2.

(Ground layer)
The ground layer 21 functions as a ground electrode for the antenna element layer 11. The ground layer 21 is formed on the entire other surface of the dielectric layer 10.

  The ground layer 21 may be the same as the antenna element layer 11 in terms of thickness, ten-point average roughness (Rz) of at least one surface, and material. Moreover, it is preferable that the ground layer 21 is subjected to rust prevention treatment, silane coupling treatment or the like, similarly to the antenna element layer 11. The antirust treatment and the silane coupling treatment can be performed in the same manner as the antenna element layer 11 described above.

(Coverlay)
The cover lay 22 protects the ground layer 21 and is laminated on the ground layer 21. The cover lay 22 includes a cover film 23 and an adhesive layer 24. About the structure of these cover films 23 and the contact bonding layer 24, it is the same as that of the coverlay 12 mentioned above.

  In such an antenna substrate 2, the antenna element layer 11 is formed on one surface of the dielectric layer 10, and the ground layer 21 is formed on the other surface. Therefore, in the antenna substrate 2, it is not necessary to provide a ground in a circuit or the like different from the antenna substrate 2 and connect the antenna element layer 11 to this ground. Therefore, the configuration of the apparatus incorporating the antenna substrate 2 and the manufacturing process are simplified. This is advantageous in terms of manufacturing cost.

<Third Embodiment>
Next, an antenna substrate according to a third embodiment of the present invention will be described with reference to FIGS. 4 to 6, the same elements as those of the antenna substrate 1 of FIGS. 1 and 2 are denoted by the same reference numerals, and redundant description below is omitted.

  The antenna substrate 3 shown in FIGS. 4 to 6 includes a dielectric layer 10, an antenna element layer 30, a ground layer 31, a cover lay 32, an electronic component 33, and wirings 34.

(Antenna element layer)
The antenna element layer 30 is basically the same as the antenna element layer 11 of the antenna substrate 1 of FIGS. 1 and 2, but differs in that the antenna element layer 30 is formed in a bellows shape in plan view. The antenna element layer 30 is connected to the electronic component 33.

(Ground layer)
The ground layer 31 functions as a ground electrode for the antenna element layer 30. The ground layer 31 is adjacent to the antenna element layer 30 and is laminated on one surface side of the dielectric layer 10. The ground layer 31 is connected to the electronic component 33 via the wiring 34. The ground layer 31 can be formed simultaneously with the patterning of the antenna element layer 30.

  The antenna element layer 30 and the ground layer 31 have the same material and ten-point average roughness (Rz) of at least one surface as those of the antenna element layer 11 of the antenna substrate 1 shown in FIGS. Moreover, it is preferable that the antenna element layer 30 and the ground layer 31 have been subjected to rust prevention treatment and silane coupling treatment, similarly to the antenna element layer 11 of the antenna substrate 1 of FIGS. 1 and 2.

(Coverlay)
The cover lay 32 includes a cover film 35 and an adhesive layer 36. The cover lay 32 is basically the same as the cover lay 12 of the antenna substrate 1 of FIGS. 1 and 2, but is different from the cover lay in that it has a notch 37. The notch 37 is formed corresponding to a portion where the electronic component 33 is mounted. That is, the cover lay 32 is prevented from interfering with the electronic component 33 by the notch 37.

(Electronic parts)
The electronic component 33 plays a role such as impedance matching in the antenna substrate 3. The electronic component 33 is connected to the antenna element layer 30, the ground layer 31, and the wiring 34. There is no limitation in particular as the electronic component 33, For example, a rectifier circuit etc. are mentioned.

(wiring)
The wiring 34 is used when the antenna element layer 30, the ground layer 31, and the electronic component 33 are connected to each other, and the antenna substrate 3 is connected to an external device. The wiring 34 is formed as a wiring pattern having a plurality of wiring portions. The wiring 34 can be formed simultaneously when the antenna element layer 30 and the ground layer 31 are patterned.

  Since the antenna substrate 3 includes the wiring 34 and the electronic component 33, the antenna substrate 3 can function as an electric circuit. Therefore, the antenna substrate 3 can be suitably used as an antenna circuit for an information communication terminal such as a mobile phone.

<Other embodiments>
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configurations of the embodiments described later, but is defined by the scope of claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of claims. Is done.

  For example, the pattern shape of the antenna element layer in the antenna substrate may be determined according to the device to which the antenna substrate is applied, and may be other shapes, not limited to a comb shape or a bellows shape.

  The antenna substrate may be obtained by laminating the ground layer 31 in the antenna substrate 3 of FIGS. 4 to 6 on the other surface side of the dielectric layer 10 as in the antenna substrate 1 of FIG.

  The application of the antenna substrate is not limited to an in-vehicle antenna or an information communication terminal such as a mobile phone, and can be applied to all devices having a function of performing information communication.

  The antenna substrate of the present invention is excellent in high-frequency signal transmission characteristics and sufficiently secures the bondability between the dielectric layer and the antenna element. Therefore, the antenna substrate of the present invention can be suitably used as an in-vehicle antenna or an antenna of an information communication terminal such as a mobile phone.

1, 2, 3 Antenna substrate 10 Dielectric layer 11, 30 Antenna element layer 12, 22, 32 Cover lay 13, 23, 35 Cover film 14, 24, 36 Adhesive layer 21, 31 Ground layer 33 Electronic component 34 Wiring 37 Notch

Claims (13)

A method for manufacturing a flexible antenna substrate, comprising:
A dielectric layer mainly composed of fluororesin;
An antenna element layer laminated on at least one surface of the dielectric layer,
The ten-point average roughness (Rz) of the surface of the antenna element layer on which the dielectric layer is laminated is 0.2 μm or more and 4 μm or less,
There is a chemical bond between the fluororesin of the dielectric layer and the antenna element layer,
The chemical bond is formed by ionizing radiation irradiation,
A method for manufacturing an antenna substrate , wherein the chemical bond is formed via a coupling agent present at an interface between the dielectric layer and the antenna element layer. The method for manufacturing an antenna substrate according to claim 1, wherein the fluororesin has a relative dielectric constant (εr) of 3 or less and a dielectric loss tangent (tan δ) of 0.004 or less. The method for manufacturing an antenna substrate according to claim 1 or 2, wherein the dielectric layer has a flexural modulus of 20 GPa or more after an exposure test specified in JIS K 7350-2: 2008. 4. The method for manufacturing an antenna substrate according to claim 1, wherein the light transmittance of the dielectric layer is 70% or more. The method for manufacturing an antenna substrate according to any one of claims 1 to 4, wherein the dielectric layer has a light transmittance of 70% or more after an exposure test defined in JIS K 7350-2: 2008. The method for manufacturing an antenna substrate according to any one of claims 1 to 5, wherein the number of bendings in the bending resistance test specified in JIS C 5016: 1994 is 400 or more. The method for manufacturing an antenna substrate according to any one of claims 1 to 6, wherein the number of times until disconnection in the fold resistance test specified in JIS C 5016: 1994 is 400 times or more. The method for manufacturing an antenna substrate according to any one of claims 1 to 7, wherein the coupling agent is a silane coupling agent having a functional group containing an N atom or an S atom. The method for manufacturing an antenna substrate according to any one of claims 1 to 8, wherein the dielectric layer has a chemical bond formed by ionizing radiation irradiation between molecules of the fluororesin. The fluororesin of the dielectric layer is tetrafluoroethylene / hexaoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), or tetrafluoroethylene- The method for manufacturing an antenna substrate according to any one of claims 1 to 9, wherein the antenna substrate is a perfluorodioxole copolymer (TFE / PDD). The method for manufacturing an antenna substrate according to any one of claims 1 to 10, further comprising a cover film that covers the antenna element layer and contains a fluororesin as a main component. The method for manufacturing an antenna substrate according to any one of claims 1 to 11, wherein the antenna substrate is used as a vehicle-mounted antenna. The wiring according to claim 1, further comprising: a wiring electrically connected to the antenna element layer; and an electronic component electrically connected to at least one of the wiring and the antenna element layer. The manufacturing method of the antenna board | substrate as described in a term.

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