Film, laminate, bandpass filter, and communication terminal

Abstract

This film contains an inorganic filler and a resin and has a thickness d satisfying formula (A), a dielectric constant of 10 or more, and a dielectric loss tangent of 0.020 or less. The present invention also pertains to uses for the film. Formula (A) is "λ / (2 × √ε) - λ / 50 ≤ d ≤ λ / (2 × √ε) + λ / 50".

Description

Film, laminate, bandpass filter, and communication terminal

[0001] The present disclosure relates to a film, a laminate, a bandpass filter, and a communication terminal.

[0002] 2. Description of the Related Art Communication devices such as mobile phones are equipped with bandpass filters that transmit only specific frequencies and block other frequencies in order to suppress radio wave interference with other devices and radio wave interference from other devices.

[0003] For example, Japanese Patent Application Laid-Open No. 2008-280464 describes a microwave filter that includes a high dielectric constant resin substrate, a conductor layer of a predetermined pattern fixed to the surface of the high dielectric constant resin substrate, and a ground conductor layer provided at a predetermined distance from the conductor pattern with the high dielectric constant resin substrate in between. JP 2011-1400 A describes a high dielectric constant resin composition characterized by having a dielectric constant of 10 or more and a dielectric dissipation factor of less than 0.01 at room temperature at a measurement frequency of 1 GHz, wherein the high dielectric constant resin composition is obtained by blending a thermosetting polyphenylene ether having a number average molecular weight of 500 to 3000, the end of which is styrene-modified, and a styrene-based elastomer in a blending ratio of the thermosetting polyphenylene ether to the styrene-based elastomer of 60:40 to 80:20 by mass, with 250 to 900 parts by mass of a high dielectric constant inorganic insulating filler having an average particle size D50 of 0.7 μm or more and a maximum particle size of 10 μm or less, per 100 parts by mass of the mixed resin (A).

[0004] As communication frequencies become higher, radio wave propagation loss increases, weakening the radio waves that can be received. Therefore, when passing specific frequencies through a bandpass filter, it is necessary to suppress loss in the passband.

[0005] An object of an embodiment of the present disclosure is to provide a film and a laminate capable of suppressing loss in a transmission band when a specific frequency is transmitted through a bandpass filter. Another object of an embodiment of the present disclosure is to provide a bandpass filter and a communication terminal using the film or laminate.

[0006] Specific means for solving the problems are as follows. <1> A film comprising an inorganic filler and a resin, having a thickness d satisfying the following formula (A), having a relative dielectric constant of 10 or more, and a dielectric loss tangent of 0.020 or less: λ / (2×√ε)-λ / 50≦d≦λ / (2×√ε)+λ / 50 ...formula (A) In formula (A), d represents the thickness in mm, λ represents the transmission center wavelength in 100c / f in mm, c represents the electromagnetic wave propagation velocity in m / s, f represents the transmission center frequency in GHz, and ε represents the relative dielectric constant. <2> The film according to <1>, wherein the inorganic filler has a relative dielectric constant of 6 to 20,000. <3> The film according to <1> or <2>, wherein the inorganic filler includes at least one selected from the group consisting of barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, zirconium titanate, zinc titanate, titanium dioxide, magnesium oxide, alumina, tantalum pentoxide, and niobium pentoxide. <4> The film according to any one of <1> to <3>, wherein the inorganic filler has an average particle size of 0.01 μm to 10 μm. <5> The film according to any one of <1> to <4>, wherein the content of the inorganic filler is 1 vol% to 90 vol% based on the total amount of the film. <6> The film according to any one of <1> to <5>, wherein the resin includes at least one selected from the group consisting of a thermoplastic resin, a thermoplastic elastomer, a semi-cured product of a thermosetting resin, a cured product of a thermosetting resin, a semi-cured product of a thermosetting elastomer, and a cured product of a thermosetting elastomer. <7> The film according to any one of <1> to <6>, having a thickness of 0.1 mm to 8 mm. <8> A laminate comprising: a resin substrate having a dielectric loss tangent of 0.020 or less; and a metamaterial layer, disposed on at least one surface of the resin substrate, the metamaterial layer including a conductor pattern constituted of at least one material selected from the group consisting of conductive materials and materials that change from non-conductors to conductors. <9> The laminate according to <8>, in which the resin substrate has a relative dielectric constant of 10 or more. <10> The laminate according to <8> or <9>, in which the resin substrate includes an inorganic filler and a resin.<11> The laminate according to <10>, wherein the inorganic filler has a relative dielectric constant of 6 to 20,000. <12> The laminate according to <10> or <11>, wherein the inorganic filler includes at least one selected from the group consisting of barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, zirconium titanate, zinc titanate, titanium dioxide, magnesium oxide, alumina, tantalum pentoxide, and niobium pentoxide. <13> The laminate according to any one of <10> to <12>, wherein the inorganic filler has an average particle size of 0.01 μm to 10 μm. <14> The laminate according to any one of <10> to <13>, wherein the content of the inorganic filler is 1 vol% to 90 vol% relative to the total amount of the resin substrate. <15> The laminate according to any one of <10> to <14>, wherein the resin comprises at least one selected from the group consisting of a thermoplastic resin, a thermoplastic elastomer, a semi-cured product of a thermosetting resin, a cured product of a thermosetting resin, a semi-cured product of a thermosetting elastomer, and a cured product of a thermosetting elastomer. <16> The laminate according to any one of <8> to <15>, wherein the conductor pattern has an area resistivity of 1 Ω / □ or less. <17> A bandpass filter comprising the film according to any one of <1> to <7> or the laminate according to any one of <8> to <16>. <18> The bandpass filter according to <17>, wherein the center frequency of the transmission band is 6 GHz to 24 GHz. <19> The bandpass filter according to <17> or <18>, wherein the insertion loss at the center frequency of the transmission band ±5 GHz is 5 dB or more. <20> The bandpass filter according to any one of <17> to <19>, which is attached to the outside of an antenna. <21> A communication terminal having a communication circuit, an antenna, and the bandpass filter according to any one of <17> to <20>, which is arranged on the outside of the antenna.

[0007] According to an embodiment of the present disclosure, there are provided a film and a laminate capable of suppressing loss in a transmission band when a specific frequency is transmitted through a bandpass filter. Also, according to an embodiment of the present disclosure, there are provided a bandpass filter and a communication terminal using the film or the laminate.

[0008] FIG. 1 is a diagram showing one embodiment of a conductor pattern of a metamaterial layer in the present disclosure.

[0009] The contents of the present disclosure are described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment. In this specification, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the upper and lower limits. In the numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, in the description of groups (atomic groups) in this specification, a notation that does not specify whether they are substituted or unsubstituted encompasses both unsubstituted and substituted groups. For example, the term "alkyl group" encompasses not only alkyl groups without substituents (unsubstituted alkyl groups) but also alkyl groups with substituents (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used to conceptually encompass both acrylic and methacrylic, and "(meth)acryloyl" is a term used to conceptually encompass both acryloyl and methacryloyl. Furthermore, the term "process" in this specification includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, in this disclosure, a combination of two or more preferred aspects is a more preferred aspect. Furthermore, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in this disclosure are molecular weights determined by a gel permeation chromatography (GPC) analyzer using a TSKgel Super HM-H (trade name of Tosoh Corporation) column, a PFP (pentafluorophenol) / chloroform solvent (mass ratio) = 1 / 2, a differential refractometer, and conversion using polystyrene as a standard substance. The average particle size (e.g., D50) of the inorganic filler in the present disclosure is measured using a laser diffraction / scattering particle size distribution analyzer, such as the LA-950V2 manufactured by HORIBA.

[0010] [Film] The film of the present disclosure contains an inorganic filler and a resin, and has a thickness d that satisfies the following formula (A), a relative dielectric constant of 10 or more, and a dielectric loss tangent of 0.020 or less: λ / (2×√ε)-λ / 50≦d≦λ / (2×√ε)+λ / 50 ... formula (A) In formula (A), d represents thickness in mm, λ represents the transmission center wavelength in 100c / f in mm, c represents the electromagnetic wave propagation velocity in m / s, f represents the transmission center frequency in GHz, and ε represents the relative dielectric constant.

[0011] The film of the present disclosure has a thickness d that satisfies the above formula (A), and therefore can suppress loss in the transmission band when transmitting a specific frequency through a bandpass filter. By designing the thickness d to satisfy the above formula (A), the electromagnetic waves reflected from the front surface and the electromagnetic waves reflected from the back surface interfere with each other, thereby increasing the transmittance of the electromagnetic wave corresponding to the center wavelength λ. If the thickness d is ±λ / 50 or less, the transmittance of the center wavelength λ remains almost unchanged.

[0012] On the other hand, Japanese Patent Application Laid-Open Nos. 2008-280464 and 2011-1400 do not mention the relationship between the thickness and the transmission center wavelength and the relative dielectric constant.

[0013] (Inorganic Filler) Examples of inorganic fillers contained in the film include barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, zirconium titanate, zinc titanate, titanium dioxide, magnesium oxide, alumina, tantalum pentoxide, and niobium pentoxide.

[0014] The inorganic filler preferably contains at least one selected from the group consisting of barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, zirconium titanate, zinc titanate, titanium dioxide, magnesium oxide, alumina, tantalum pentoxide, and niobium pentoxide. Among these, the inorganic filler is more preferably barium titanate or titanium oxide.

[0015] The inorganic filler preferably has a relative dielectric constant of 6 to 20,000 at 25° C. and a frequency of 10 GHz, and more preferably 20 to 20,000.

[0016] From the viewpoint of achieving both an orientation state and dielectric properties, the average particle size of the inorganic filler is preferably 0.01 μm to 10 μm, more preferably 0.02 μm to 2 μm, and particularly preferably 0.03 μm to 5 μm.

[0017] The average particle size is measured using a laser diffraction / scattering particle size distribution analyzer, such as the LA-950V2 manufactured by HORIBA.

[0018] The shape of the inorganic filler is not particularly limited, and may be amorphous or spherical. From the viewpoint of increasing the content in the film and improving the relative dielectric constant of the film, the shape of the inorganic filler is preferably spherical.

[0019] The inorganic filler contained in the film may be of one type only, or may be of two or more types. From the viewpoint of achieving both dielectric properties and mechanical properties, the content of the inorganic filler is preferably 1 to 90% by volume, more preferably 20 to 90% by volume, even more preferably 30 to 85% by volume, and particularly preferably 40 to 80% by volume, relative to the total amount of the film.

[0020] The inorganic filler may be surface-treated with an inorganic or organic substance, for example, by (1) coating, (2) topochemical modification, (3) mechanochemical modification, (4) encapsulation, or (5) irradiation.

[0021] (Resin) Examples of resins contained in the film include thermoplastic resins, thermoplastic elastomers; semi-cured or cured thermosetting resins; and semi-cured or cured thermosetting elastomers.

[0022] The resin preferably includes at least one selected from the group consisting of a thermoplastic resin, a thermoplastic elastomer, a semi-cured product of a thermosetting resin, a cured product of a thermosetting resin, a semi-cured product of a thermosetting elastomer, and a cured product of a thermosetting elastomer.

[0023] Examples of thermoplastic resins include polyester resins (including liquid crystal polymers), cyanate resins, coumarone resins, polyurethane resins, (meth)acrylic resins, polystyrene resins, fluororesins, polyimide resins, fluorinated polyimide resins, polyamide resins, polyamideimide resins, polyetherimide resins, cellulose acylate resins, polyether ether ketone resins, polycarbonate resins, polyolefin resins (e.g., polyethylene resins, polypropylene resins, resins made of cyclic olefin copolymers, alicyclic polyolefin resins), polyarylate resins, polyethersulfone resins, polysulfone resins, fluorene ring-modified polycarbonate resins, alicyclic ring-modified polycarbonate resins, and fluorene ring-modified polyester resins.

[0024] Examples of thermoplastic elastomers include elastomers containing structural units derived from styrene (polystyrene elastomers), polyester elastomers, polyolefin elastomers, polyurethane elastomers, polyamide elastomers, polyacrylic elastomers, silicone elastomers, and polyimide elastomers. The thermoplastic elastomer may be a hydrogenated product.

[0025] Examples of polystyrene elastomers include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), polystyrene-poly(ethylene-propylene) diblock copolymers (SEP), polystyrene-poly(ethylene-propylene)-polystyrene triblock copolymers (SEPS), styrene-ethylene-butylene-styrene block copolymers (SEBS), and polystyrene-poly(ethylene / ethylene-propylene)-polystyrene triblock copolymers (SEEPS), styrene-isobutylene-styrene block copolymers (SIBS), and hydrogenated products thereof.

[0026] Examples of thermosetting resins include epoxy resins which are monomers, oligomers, or polymers having two or more epoxy groups in one molecule, and the molecular weight and molecular structure are not particularly limited.

[0027] stilbene-type epoxy resins; novolac-type epoxy resins such as phenol novolac-type epoxy resins and cresol novolac-type epoxy resins; polyfunctional epoxy resins such as triphenolmethane-type epoxy resins and alkyl-modified triphenolmethane-type epoxy resins; aralkyl-type epoxy resins such as phenol aralkyl-type epoxy resins having a phenylene skeleton and phenol aralkyl-type epoxy resins having a biphenylene skeleton; naphthol-type epoxy resins such as dihydroxynaphthalene-type epoxy resins and epoxy resins obtained by glycidyl etherifying a dihydroxynaphthalene dimer; triazine-nucleus-containing epoxy resins such as triglycidyl isocyanurate and monoallyl diglycidyl isocyanurate; and bridged cyclic hydrocarbon compound-modified phenol-type epoxy resins such as dicyclopentadiene-modified phenol-type epoxy resins.

[0028] From the viewpoint of improving the balance between moisture resistance reliability and moldability, the epoxy resin is preferably at least one selected from the group consisting of bisphenol-type epoxy resins, novolac-type epoxy resins, biphenyl-type epoxy resins, phenol aralkyl-type epoxy resins, and triphenolmethane-type epoxy resins, and more preferably at least one selected from the group consisting of biphenyl-type epoxy resins and phenol aralkyl-type epoxy resins.

[0029] The semi-cured product of the thermosetting resin and the cured product of the thermosetting resin are preferably semi-cured and cured products of the thermosetting resin, respectively.

[0030] Examples of curing agents for curing epoxy resins include linear aliphatic diamines having 2 to 20 carbon atoms, such as ethylenediamine, trimethylenediamine, tetramethylenediamine, and hexamethylenediamine; metaphenylenediamine, paraphenylenediamine, paraxylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylether, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodicyclohexane, bis(4-aminophenyl)phenylmethane, 1,5-diaminonaphthalene, metaxylenediamine, paraxylenediamine, 1,1-bis(4-aminophenyl)cyclohexane, and dicyanodiamide; resol-type phenolic resins, such as aniline-modified resol resins and dimethyl ether resol resins; phenol novolac resins, cresol novolac resins, tert-butylphenol novolac resins, and novolac resins. phenol aralkyl resins such as phenylene skeleton-containing phenol aralkyl resins and biphenylene skeleton-containing phenol aralkyl resins; phenol resins having a condensed polycyclic structure such as a naphthalene skeleton or an anthracene skeleton; polyoxystyrenes such as polyparaoxystyrene; acid anhydrides including alicyclic acid anhydrides such as hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydride (MTHPA), and aromatic acid anhydrides such as trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), and benzophenonetetracarboxylic acid (BTDA); polymercaptan compounds such as polysulfide, thioester, and thioether; isocyanate compounds such as isocyanate prepolymers and blocked isocyanates; and organic acids such as carboxylic acid-containing polyester resins.

[0031] The curing agent may be used alone or in combination of two or more kinds.

[0032] The amount of curing agent added is not particularly limited, but is, for example, preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 10% by mass, and even more preferably 1% by mass to 5% by mass, relative to the total content of the resin and curing agent.

[0033] Examples of the thermosetting elastomer include silicone rubber, fluororubber, and urethane rubber. Examples of the silicone rubber include vinyl group-containing organopolysiloxane.

[0034] The semi-cured product of the thermosetting elastomer and the cured product of the thermosetting elastomer are preferably semi-cured and cured products of the above-mentioned thermosetting elastomer, respectively.

[0035] In particular, the resin preferably contains a liquid crystal polymer.

[0036] The type of liquid crystal polymer is not particularly limited, and known liquid crystal polymers can be used. The liquid crystal polymer may be a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state, or a lyotropic liquid crystal polymer that exhibits liquid crystallinity in a solution state. In the case of a thermotropic liquid crystal, it is preferable that the polymer melts at a temperature of 450°C or less.

[0037] Examples of liquid crystal polymers include liquid crystal polyester, liquid crystal polyester amide in which an amide bond is introduced into liquid crystal polyester, liquid crystal polyester ether in which an ether bond is introduced into liquid crystal polyester, and liquid crystal polyester carbonate in which a carbonate bond is introduced into liquid crystal polyester.

[0038] From the viewpoint of liquid crystallinity, the liquid crystal polymer is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or an aromatic polyester amide.

[0039] The liquid crystal polymer may be a polymer in which an isocyanate-derived bond such as an imide bond, a carbodiimide bond, or an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide.

[0040] The liquid crystal polymer is preferably a wholly aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0041] Examples of liquid crystal polymers include the following: 1) A liquid crystal polymer obtained by polycondensation of (i) an aromatic hydroxycarboxylic acid, (ii) an aromatic dicarboxylic acid, and (iii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine; 2) A liquid crystal polymer obtained by polycondensation of multiple aromatic hydroxycarboxylic acids; 3) A liquid crystal polymer obtained by polycondensation of (i) an aromatic dicarboxylic acid and (ii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine; 4) A liquid crystal polymer obtained by polycondensation of (i) a polyester such as polyethylene terephthalate and (ii) an aromatic hydroxycarboxylic acid. Here, the aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, aromatic hydroxyamine, and aromatic diamine may each independently be replaced with a derivative capable of polycondensation.

[0042] The melting point of the liquid crystal polymer is preferably higher than 260°C, more preferably higher than 260°C and not higher than 350°C, and even more preferably higher than 260°C and not higher than 330°C.

[0043] In the present disclosure, the melting point is measured using a differential scanning calorimeter. For example, it is measured using a product called "DSC-60A Plus" (manufactured by Shimadzu Corporation). The temperature rise rate in the measurement is 10°C / min.

[0044] The weight average molecular weight of the liquid crystal polymer is preferably 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000.

[0045] From the viewpoint of further reducing the dielectric loss tangent, the liquid crystal polymer preferably contains an aromatic polyesteramide. The aromatic polyesteramide is a resin having at least one aromatic ring and having an ester bond and an amide bond. In particular, from the viewpoint of heat resistance, the aromatic polyesteramide is preferably a wholly aromatic polyesteramide.

[0046] The aromatic polyesteramide is preferably a crystalline polymer. The first phase preferably contains a crystalline aromatic polyesteramide. The crystalline aromatic polyesteramide further reduces the dielectric loss tangent. A crystalline polymer refers to one that has a clear endothermic peak rather than a stepwise change in endothermic amount in differential scanning calorimetry (DSC). Specifically, for example, this means that the half-width of the endothermic peak when measured at a heating rate of 10°C / min is within 10°C. Polymers with a half-width exceeding 10°C and polymers in which no clear endothermic peak is observed are considered amorphous polymers and are distinguished from crystalline polymers.

[0047] The aromatic polyester amide preferably contains a structural unit represented by the following formula 1, a structural unit represented by the following formula 2, and a structural unit represented by the following formula 3: １ -CO-...Formula 1 -CO-Ar ２ -CO-...Formula 2 -NH-Ar ３ -O-...Formula 3 In Formulas 1 to 3, Ar １ , Ar ２ , and Ar ３ each independently represents a phenylene group, a naphthylene group, or a biphenylylene group. Hereinafter, the structural unit represented by formula 1 may also be referred to as "unit 1", etc.

[0048] Unit 1 can be introduced, for example, by using an aromatic hydroxycarboxylic acid as a raw material. Unit 2 can be introduced, for example, by using an aromatic dicarboxylic acid as a raw material. Unit 3 can be introduced, for example, by using an aromatic hydroxylamine as a raw material.

[0049] Here, the aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, and aromatic hydroxylamine may each independently be replaced with a derivative capable of undergoing polycondensation.

[0050] For example, by converting the carboxy group to an alkoxycarbonyl group or an aryloxycarbonyl group, aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid esters and aromatic dicarboxylic acid esters. By converting the carboxy group to a haloformyl group, aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid halides and aromatic dicarboxylic acid halides. By converting the carboxy group to an acyloxycarbonyl group, aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid anhydrides and aromatic dicarboxylic acid anhydrides. Examples of polycondensable derivatives of compounds having hydroxy groups, such as aromatic hydroxycarboxylic acids and aromatic hydroxyamines, include those obtained by acylation of the hydroxy group to an acyloxy group (acylated products). For example, by acylation of the hydroxy group to an acyloxy group, aromatic hydroxycarboxylic acids and aromatic hydroxylamines can be replaced with acylated products, respectively. Examples of polycondensable derivatives of aromatic hydroxylamines include those obtained by acylation of the amino group to an acylamino group (acylated products). For example, aromatic hydroxyamines can be replaced with acylated products by acylation of the amino group to convert them into acylamino groups.

[0051] In formula 1, Ar １ is preferably a p-phenylene group, a 2,6-naphthylene group, or a 4,4'-biphenylylene group, and more preferably a 2,6-naphthylene group.

[0052] Ar １ When Ar is a p-phenylene group, unit 1 is, for example, a constitutional unit derived from p-hydroxybenzoic acid. １When Ar is a 2,6-naphthylene group, unit 1 is, for example, a structural unit derived from 6-hydroxy-2-naphthoic acid. １ is a 4,4'-biphenylylene group, unit 1 is, for example, a constitutional unit derived from 4'-hydroxy-4-biphenylcarboxylic acid.

[0053] In formula 2, Ar ２ is preferably a p-phenylene group, an m-phenylene group, or a 2,6-naphthylene group, and more preferably an m-phenylene group.

[0054] Ar ２ When Ar is a p-phenylene group, unit 2 is, for example, a structural unit derived from terephthalic acid. ２ When Ar is an m-phenylene group, unit 2 is, for example, a structural unit derived from isophthalic acid. ２ is a 2,6-naphthylene group, unit 2 is, for example, a structural unit derived from 2,6-naphthalenedicarboxylic acid.

[0055] In formula 3, Ar ３ is preferably a p-phenylene group or a 4,4'-biphenylylene group, and more preferably a p-phenylene group.

[0056] Ar ３ When Ar is a p-phenylene group, unit 3 is, for example, a constitutional unit derived from p-aminophenol. ３ is a 4,4'-biphenylylene group, unit 3 is, for example, a constitutional unit derived from 4-amino-4'-hydroxybiphenyl.

[0057] With respect to the total content of units 1, 2, and 3, the content of units 1 is preferably 30 mol% or more, the content of units 2 is preferably 35 mol% or less, and the content of units 3 is preferably 35 mol% or less. With respect to the total content of units 1, 2, and 3, the content of units 1 is more preferably 30 mol% to 80 mol%, even more preferably 30 mol% to 60 mol%, and particularly preferably 30 mol% to 40 mol%. With respect to the total content of units 1, 2, and 3, the content of units 2 is preferably 10 mol% to 35 mol%, even more preferably 20 mol% to 35 mol%, and particularly preferably 30 mol% to 35 mol%. With respect to the total content of units 1, 2, and 3, the content of units 3 is preferably 10 mol% to 35 mol%, even more preferably 20 mol% to 35 mol%, and particularly preferably 30 mol% to 35 mol%. The total content of each structural unit is the sum of the amounts (moles) of each structural unit, which is calculated by dividing the mass of each structural unit constituting the aromatic polyesteramide by the formula weight of the structural unit.

[0058] The ratio of the content of units 2 to the content of units 3, expressed as [content of units 2] / [content of units 3] (mol / mol), is preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and even more preferably 0.98 / 1 to 1 / 0.98.

[0059] The aromatic polyesteramide may independently have two or more types of units 1 to 3. The aromatic polyesteramide may also have other structural units in addition to units 1 to 3. The content of other structural units is preferably 10 mol % or less, more preferably 5 mol % or less, based on the total content of all structural units.

[0060] The aromatic polyesteramide is preferably produced by melt-polymerizing raw material monomers corresponding to the structural units that constitute the aromatic polyesteramide.

[0061] The weight average molecular weight of the aromatic polyesteramide is preferably 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000.

[0062] The resin content of the film may be one type or two or more types. From the viewpoint of achieving both dielectric properties and mechanical properties, the resin content is preferably 10 to 80% by volume, more preferably 15 to 70% by volume, and even more preferably 20 to 60% by volume.

[0063] The film may contain additives other than the inorganic filler and resin, such as a polymerization initiator, a dispersant, a surfactant, a crosslinking agent, and an antioxidant.

[0064] (Physical Properties) -Dielectric Loss Tangent- The dielectric loss tangent of the film is 0.020 or less, preferably 0.00050 to 0.020, and more preferably 0.00010 to 0.010.

[0065] —Dielectric Constant— The dielectric constant of the film is 10 or more, preferably 10 to 1,000, and more preferably 30 to 100.

[0066] In the present disclosure, the dielectric constant and the dielectric loss tangent are measured by the following method. The dielectric constant and the dielectric loss tangent are measured at a frequency of 10 GHz by a resonance perturbation method. A 10 GHz cavity resonator (CP531 manufactured by Kanto Electronics Application Development Co., Ltd.) is connected to a network analyzer (E8363B manufactured by Agilent Technology Corporation), a film is inserted into the cavity resonator, and the change in the resonance frequency before and after insertion for 96 hours is measured in an environment of a temperature of 25°C and a humidity of 60% RH.

[0067] - Thickness - The thickness d satisfies the following formula (A): A film having a relative dielectric constant of 10 or more and a dielectric loss tangent of 0.020 or less, λ / (2×√ε)-λ / 50≦d≦λ / (2×√ε)+λ / 50 ... formula (A).

[0068] [λ] λ represents the transmission center wavelength, expressed as 100c / f, in mm. c represents the electromagnetic wave propagation velocity, in m / s. f represents the transmission center frequency, in GHz.

[0069] The transmission central wavelength refers to the central wavelength of radio waves transmitted through the film. The electromagnetic wave propagation speed is approximately 3 m / s, and when the transmission central frequency is 10 GHz, the transmission central wavelength is approximately 30 mm. The transmission central wavelength is measured using the following method. A receiving horn antenna was connected to Port 1 of a network analyzer (Agilent Technology's "E8363B"), and a transmitting horn antenna was connected to Port 2. The receiving horn antenna and the transmitting horn antenna were arranged facing each other. A sample holder was prepared by attaching a steel sheet to a radio wave absorber with openings. Both ends of the measurement sample were inserted into the openings of the two sample holders. The measurement sample held by the sample holder was placed between the receiving horn antenna and the transmitting horn antenna so that the radio waves could pass through the measurement sample. Radio waves were transmitted and received, and the S parameter S21 was measured. The amount of radio wave attenuation (insertion loss) when the measurement sample is installed is measured using the amount of transmission when the measurement sample is not installed as a reference. The insertion loss is plotted against frequency, and the center value of frequencies f1 and f2 where the loss amount corresponds to 50% (approximately 3 dB) is taken as the transmission center frequency.

[0070] The transmission center frequency is set, for example, in the range of 6 GHz to 24 GHz.

[0071] [d] The thickness of the film satisfies the above formula (A) and is, for example, 0.1 mm to 8 mm.

[0072] The thickness of the film is measured at any five points using an adhesive film thickness meter, for example, an electronic micrometer (product name "KG3001A", manufactured by Anritsu Corporation), and the average value is used as the thickness.

[0073] <Film Manufacturing Method> The film manufacturing method is not particularly limited, and known methods can be used.

[0074] Suitable film-forming methods include, for example, co-casting, multi-layer coating, and co-extrusion, and the film can also be produced using a dispenser or the like.

[0075] When a multilayer structure is produced by a co-casting method or a multi-layer coating method, it is preferable to carry out the co-casting method or the multi-layer coating method using a solution in which the components of each layer are dissolved or dispersed in a solvent.

[0076] The method for producing the film preferably includes a step of preparing a solution by dispersing the solution in a bead mill, and a step of forming a film using the solution.

[0077] Dispersion treatment using a bead mill reduces particle agglomerates and achieves uniformity. The diameter of the beads used in the bead mill is preferably larger than the average particle size of the particles used to prepare the solution. The diameter of the beads is, for example, 0.1 mm to 5 mm.

[0078] Examples of the solvent include halogenated hydrocarbons such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-chlorobutane, chlorobenzene, and o-dichlorobenzene; halogenated phenols such as p-chlorophenol, pentachlorophenol, and pentafluorophenol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and cyclohexanone; esters such as ethyl acetate and γ-butyrolactone; and ethylene carbonate. nitriles such as acetonitrile and succinonitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and urea compounds such as tetramethylurea; nitro compounds such as nitromethane and nitrobenzene; sulfur compounds such as dimethyl sulfoxide and sulfolane; and phosphorus compounds such as hexamethylphosphoramide and tri-n-butylphosphoric acid, and two or more of these may be used.

[0079] As the solvent, a solvent mainly composed of an aprotic compound, particularly an aprotic compound having no halogen atoms, is preferred because it is less corrosive and easier to handle, and the proportion of the aprotic compound in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. Furthermore, as the aprotic compound, an amide such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or an ester such as γ-butyrolactone is preferably used because it easily dissolves the liquid crystal polymer, and N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone are more preferred.

[0080] Furthermore, as the solvent, a solvent containing as a main component a compound having a dipole moment of 3 to 5 is preferred because it easily dissolves the liquid crystal polymer, and the proportion of the compound having a dipole moment of 3 to 5 in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. It is preferable to use a compound having a dipole moment of 3 to 5 as the aprotic compound.

[0081] Furthermore, as the solvent, a solvent containing as a main component a compound having a boiling point of 220°C or lower at 1 atmosphere is preferred because it is easy to remove, and the proportion of the compound having a boiling point of 220°C or lower at 1 atmosphere in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. It is preferable to use a compound having a boiling point of 220°C or lower at 1 atmosphere as the aprotic compound.

[0082] In the film manufacturing method, when the film is manufactured by the above-mentioned co-casting method, multi-layer coating method, co-extrusion method, or the like, a support may be used.

[0083] Examples of the support include a metal drum, a metal band, a glass plate, a resin film, and a metal foil, and among these, the support is preferably a metal drum, a metal band, or a resin film.

[0084] The support may have a surface treatment layer formed on its surface to facilitate peeling. The surface treatment layer may be made of hard chrome plating, fluororesin, or the like. The average thickness of the support is not particularly limited, but is preferably 25 μm to 75 μm, and more preferably 50 μm to 75 μm.

[0085] The method for removing at least a part of the solvent from the cast or coated film-like composition (coating film) is not particularly limited, and any known drying method can be used.

[0086] [Laminate] The laminate of the present disclosure includes a resin substrate having a dielectric loss tangent of 0.020 or less, and a metamaterial layer on at least one surface of the resin substrate, the metamaterial layer including a conductor pattern composed of at least one material selected from the group consisting of conductive materials and materials that change from non-conductors to conductors. The metamaterial layer can propagate (transmit) light of a specific wavelength by including a specific conductor pattern. The laminate is also called a laminate plate.

[0087] <Resin Substrate> The preferred embodiments of the resin substrate in the laminate are the same as the preferred embodiments of the film described above.

[0088] The resin substrate preferably contains an inorganic filler and a resin. Preferred embodiments of the inorganic filler and resin that may be contained in the resin substrate are the same as the preferred embodiments of the inorganic filler and resin that are contained in the film.

[0089] The resin substrate may contain additives other than the inorganic filler and resin, such as a polymerization initiator, a dispersant, a surfactant, a crosslinking agent, and an antioxidant.

[0090] (Physical Properties) -Dielectric Loss Tangent- The dielectric loss tangent of the resin substrate is 0.020 or less, preferably 0.00050 to 0.020, and more preferably 0.00010 to 0.010.

[0091] - Dielectric Constant - The dielectric constant of the resin substrate is preferably 10 or more, more preferably 10 to 1,000, and even more preferably 30 to 100. A dielectric constant of 10 or more improves the electromagnetic wave shielding effect and enhances the function as a filter. Furthermore, in a metamaterial layer including a specific conductor pattern, a dielectric constant of 10 or more allows the pattern structure to be made smaller, thereby enabling the metamaterial to be miniaturized and integrated.

[0092] <Metamaterial Layer> The metamaterial layer is disposed on at least one surface of the resin substrate. The metamaterial layer includes a conductor pattern made of at least one material selected from the group consisting of conductive materials and materials that change from non-conductors to conductors. The metamaterial layer may be disposed on both the at least one surface and the other surface of the resin substrate.

[0093] A conductive material is a material that has electrical conductivity. ８ It means the property of being less than Ω cm.

[0094] The conductive material preferably contains a metal, more preferably at least one selected from the group consisting of gold, silver, platinum, copper, and aluminum. Among these, from the viewpoint of sheet resistivity, the conductive material is particularly preferably at least one of gold and copper, and most preferably copper.

[0095] Examples of materials that change from non-conductors to conductors include materials that change from non-conductors to conductors when heated, irradiated with light, or applied with a voltage.

[0096] The material that changes from a non-conductor to a conductor is preferably at least one selected from the group consisting of a phase change material, a semiconductor, a conductive oxide, and a carbon material.

[0097] In the present disclosure, a phase change material refers to a material that undergoes a phase change between an amorphous phase and a crystalline phase due to Joule heating caused by an electric pulse.

[0098] Examples of phase-change materials include vanadium oxide, antimony tellurium (SbTe) alloy, germanium tellurium (GeTe) alloy, germanium antimony tellurium (GeSbTe) alloy, indium antimony tellurium (InSbTe) alloy, silver indium antimony tellurium (AgInSbTe) alloy, etc. Among these, vanadium oxide or GeSbTe alloy is preferred from the viewpoints of easily controlling the temperature and voltage at which the material changes from a non-conductor to a conductor, the smoothness of the pattern, and adhesion to the substrate.

[0099] Examples of semiconductors include p-type π-conjugated polymers, condensed polycyclic compounds, triarylamine compounds, hetero five-membered ring compounds, phthalocyanine compounds, and porphyrin compounds.

[0100] Examples of conductive oxides include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and indium gallium zinc oxide (IGZO).

[0101] Examples of the carbon material include carbon nanotubes and graphene.

[0102] The conductive pattern may include a plurality of structures, and may include two or more types of structures that differ in shape, size, etc.

[0103] The shape of the structure is not particularly limited, and it is preferable that the shape be such that when terahertz-band electromagnetic waves are incident on a metamaterial, the interaction between the incident electromagnetic waves and the electric field and magnetic field, etc., generates charge imbalances and currents within the structure or between adjacent structures, thereby inducing a dielectric or magnetic response change.

[0104] The shape of the structure is not particularly limited, and examples thereof include, in the in-plane direction of the resin substrate, a C-shape, a U-shape, a double ring shape, a V-shape, an L-shape, a lattice shape, a spiral shape, a square shape, a circle shape, a cross shape, etc. The structure is made of a conductive material or a material that changes from a non-conductor to a conductor.

[0105] From the viewpoint of reducing polarization dependency, the structure preferably has a shape that is symmetrical with respect to an arbitrary X direction and a Y direction perpendicular to the X direction in the in-plane direction of the resin substrate, and examples thereof include a cross shape, a Jerusalem cross shape, a circle shape, a square shape, and the like.

[0106] The size of the structure is not particularly limited, and the maximum length of the structure is preferably equal to or less than the wavelength of the incident electromagnetic wave, more preferably 0.5 mm to 20 mm, and even more preferably 1 mm to 10 mm.

[0107] In the present disclosure, the maximum length of a structure means the longest length when a straight line is drawn from one end of the structure to the other end in the in-plane direction of the substrate.

[0108] From the viewpoint of smoothness of the conductor pattern, the width of the structure is preferably 3 μm to 400 μm. For example, when the structure is C-shaped, the width of the structure refers to the length in the direction perpendicular to the longitudinal direction of the C shape.

[0109] Furthermore, it is preferable that the shortest distance between the structures be changed appropriately depending on the shape, size, etc. of the structures, and can be set to, for example, 20 μm to 1000 μm.

[0110] Furthermore, when the structure is a split-ring resonator, the gap is preferably 1 μm to 15 μm from the viewpoint of smoothness of the conductor pattern.

[0111] A split-ring resonator refers to a structure having a C- or U-shape.

[0112] The positions of the structures on the surface of the resin substrate are not particularly limited, and it is preferable that the structures be arranged so as to resonate with electromagnetic waves in the terahertz band. Furthermore, the structures may be arranged on the surface of the substrate so as to form a periodic structure in which the amount of phase shift of electromagnetic waves in the terahertz band continuously increases or decreases from the center of the surface of the resin substrate toward the outer region. One embodiment of the periodic structure is a structure in which structures of different diameters are arranged concentrically. The range of change in diameter of the concentrically arranged structures can be 10 μm to 200 μm.

[0113] When the structure has a cross shape, it may have a shape in which the cross shape shown in Fig. 1 is repeated as a unit, for example. In Fig. 1, the pattern size S1 is preferably 1 to 100 mm from the viewpoints of wavelength selectivity and transmission loss, the cross length L1 is preferably 1 to 50 mm from the viewpoints of wavelength selectivity and transmission loss, and the cross width W1 is preferably 0.1 to 20 mm from the viewpoints of wavelength selectivity and transmission loss.

[0114] From the viewpoint of electromagnetic wave transparency, the conductor pattern preferably has an area resistivity of 1 Ω / □ or less, more preferably 0.8 Ω / □ or less, and even more preferably 0.01 Ω / □ to 0.6 Ω / □. When the area resistivity is 1 Ω / □ or less, the component lost as heat is reduced, making it possible to produce a bandpass filter with reduced insertion loss.

[0115] In the present disclosure, the sheet resistivity is measured using a resistance meter, such as the non-contact eddy current resistance meter EC-80P manufactured by Napson Corporation or a device equivalent thereto.

[0116] From the viewpoints of electromagnetic wave transparency, cost reduction, etc., the thickness of the conductor pattern is preferably less than 5 μm, more preferably 0.01 μm to 4 μm, even more preferably 0.05 μm to 3 μm, and particularly preferably 0.1 μm to 1 μm. Furthermore, in the present disclosure, the thickness of the conductor pattern is determined by measuring the cross section of the metamaterial layer in the thickness direction using a scanning electron microscope (SEM) and averaging the values ​​at any five points.

[0117] The method for forming the conductive pattern is not particularly limited, and for example, a pattern can be formed by forming a sputtered film on the surface of a substrate by sputtering, then forming a resist pattern on the surface of the sputtered film, etching away the sputtered film that is not covered by the resist pattern, and then removing the resist pattern. The method for forming the pattern is not limited to the above method, and a vapor deposition film may be formed by vapor deposition instead of sputtering.

[0118] [Bandpass Filter] The bandpass filter of the present disclosure preferably includes the film or the laminate, and has high-frequency bandpass characteristics that transmit only specific frequencies and block other frequencies in the frequency range of 1 GHz to 100 GHz.

[0119] The center frequency of the passband is preferably 6 GHz to 24 GHz.

[0120] The insertion loss at the center frequency of the passband is preferably 0.5 dB or less, more preferably 0.1 dB or less. The lower limit of the insertion loss is, for example, 0 dB. The insertion loss at the center frequency of the passband ±5 GHz is preferably 5 dB or more, more preferably 8 dB or more. The upper limit of the insertion loss is, for example, 20 dB.

[0121] The bandpass filter of the present disclosure is preferably attached to the outside of the antenna. While conventional bandpass filters are installed within the antenna circuit, the bandpass filter of the present disclosure can be installed independently of the antenna circuit, eliminating the complexity of installing a bandpass filter within the antenna circuit.

[0122] [Communication Terminal] A communication terminal according to the present disclosure includes a communication circuit, an antenna, and the bandpass filter arranged outside the antenna.

[0123] A bandpass filter is attached to the outside of the antenna, allowing only specific frequencies from the received radio waves to pass through and blocking other frequencies, allowing signals to be transmitted to the antenna.

[0124] The present disclosure will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific examples shown below.

[0125] Details of each material used in producing the film are as follows:

[0126] <Inorganic fillers> F1: Pulverized barium titanate particles (average particle size 2 μm, relative dielectric constant 1,000, dielectric dissipation factor 0.015) F2: Pulverized barium titanate particles (average particle size 0.18 μm, relative dielectric constant 200, dielectric dissipation factor 0.30) F3: Pulverized titanium dioxide particles (average particle size 7 μm, relative dielectric constant 85, dielectric dissipation factor 0.013) F4: Pulverized strontium titanate particles (average particle size 1 μm, relative dielectric constant 300, dielectric dissipation factor 0.0050)

[0127] <Resins> P1: Aromatic polyesteramide prepared according to the following production method P2: (meth)acrylic resin (product name "ACRYPET VRL20A", manufactured by Mitsubishi Chemical Corporation, Tg = 109°C)

[0128] -Synthesis of aromatic polyesteramide P1- A reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer, and reflux condenser was charged with 940.9 g (5.0 mol) of 6-hydroxy-2-naphthoic acid, 415.3 g (2.5 mol) of isophthalic acid, 377.9 g (2.5 mol) of acetaminophen, and 867.8 g (8.4 mol) of acetic anhydride. The gas inside the reactor was replaced with nitrogen gas, and then the mixture was heated from room temperature (23°C, the same applies hereinafter) to 140°C over 60 minutes while stirring under a nitrogen gas stream, and refluxed at 140°C for 3 hours. Next, while distilling off by-product acetic acid and unreacted acetic anhydride, the mixture was heated from 150°C to 300°C over 5 hours and held at 300°C for 30 minutes. The contents were then removed from the reactor and cooled to room temperature. The resulting solid was pulverized in a grinder to obtain powdered aromatic polyesteramide P1a. The flow initiation temperature of the aromatic polyesteramide P1a was 193°C. The aromatic polyesteramide P1a was a wholly aromatic polyesteramide. The aromatic polyesteramide P1a was heated from room temperature to 160°C over 2 hours and 20 minutes under a nitrogen atmosphere, then heated from 160°C to 180°C over 3 hours and 20 minutes, and held at 180°C for 5 hours to undergo solid-state polymerization, followed by cooling. The mixture was then pulverized in a grinder to obtain a powdered aromatic polyesteramide P1b. The flow initiation temperature of the aromatic polyesteramide P1b was 220°C. The aromatic polyesteramide P1b was heated from room temperature to 180°C over 1 hour and 25 minutes under a nitrogen atmosphere, then heated from 180°C to 255°C over 6 hours and 40 minutes, and held at 255°C for 5 hours to undergo solid-state polymerization, followed by cooling to obtain a powdered aromatic polyesteramide P1. The flow initiation temperature of the aromatic polyesteramide P1 was 302°C. The melting point of the aromatic polyesteramide P1 was measured using a differential scanning calorimeter and found to be 311° C. The dielectric dissipation factor of the aromatic polyesteramide P1 was 0.0030.

[0129] <Copper foil> M1: Product name "CF-T49A-DS-18", manufactured by Fukuda Metal Foil and Powder Industry Co., Ltd., average thickness 18 μm

[0130] [Preparation of Single-Sided Copper-Clad Laminates] -Examples 1 to 6, 101 to 105, Comparative Examples 1 to 3, and 101- The inorganic fillers and resins shown in Tables 1 and 2 were mixed in the contents (volume %) shown in Tables 1 and 2, and dispersed using a bead mill to obtain solutions (dispersions).

[0131] The resulting solution was sent to a slot die and applied to copper foil M1 by adjusting the flow rate so that the average thickness after drying would be as shown in Tables 1 and 2. The solvent was removed from the coating by hot air drying. Further heat treatment was performed by increasing the temperature from 50°C to 300°C at a rate of 1°C / min in a nitrogen atmosphere and holding at 300°C for 2 hours to produce a single-sided copper-clad laminate.

[0132] Comparative Example 102: Resin P2 was vacuum dried at 100°C and fed into a single-screw extruder in which the raw material hopper and extruder were replaced with nitrogen. The resin was melted at a cylinder set temperature of 230°C to 270°C, passed through a coat hanger-type T-die, and cooled with a 120°C chrome-plated casting roll and a 90°C cooling chrome-plated casting roll to produce a film. The copper foil M1 and the film were laminated for 1 minute using a laminator (product name "Vacuum Laminator V-130", manufactured by Nikko Materials Co., Ltd.) at 140°C and a lamination pressure of 0.4 MPa to obtain a precursor for a single-sided copper-clad laminate. Furthermore, a thermocompression bonding machine (product name "MP-SNL", manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used to thermocompress the obtained precursor for a single-sided copper-clad laminate at 320°C and 4 MPa to produce a single-sided copper-clad laminate.

[0133] [Preparation of Double-Sided Copper-Clad Laminate] Example 106: The inorganic filler and resin listed in Table 2 were mixed in the content (volume %) listed in Table 2 and dispersed using a bead mill to obtain a solution (dispersion). The obtained solution was sent to a slot die and applied to copper foil M1 by adjusting the flow rate so that the average thickness after drying would be the thickness listed in Table 2. The solvent was removed from the coating by hot air drying. A single-sided copper-clad laminate was produced by further heating the mixture from 50°C to 300°C at a rate of 1°C / min in a nitrogen atmosphere and holding it at 300°C for 2 hours. The obtained single-sided copper-clad laminate and copper foil M1 were laminated for 1 minute using a laminator (product name "Vacuum Laminator V-130", manufactured by Nikko Materials Co., Ltd.) at 140°C and a lamination pressure of 0.4 MPa to obtain a precursor of a double-sided copper-clad laminate. Furthermore, the obtained double-sided copper-clad laminate precursor was subjected to thermocompression bonding under conditions of 320°C and 4 MPa using a thermocompression bonding machine (product name "MP-SNL", manufactured by Toyo Seiki Seisakusho, Ltd.), to produce a double-sided copper-clad laminate.

[0134] [Formation of Conductive Pattern] The copper foil of the obtained single-sided copper-clad laminates of Examples 101 to 105 and Comparative Example 102, and the double-sided copper-clad laminate of Example 106 was etched by a known method to form a pattern having a repeating unit of the cross shape shown in Fig. 1. The formed conductive pattern was a metamaterial that selectively transmits around 10 GHz.

[0135] [Fabrication of a communication terminal having a bandpass filter] The single-sided copper-clad laminate and double-sided copper-clad laminate fabricated above were laminated together and attached to a patch antenna of a smartphone via an adhesive to fabricate a communication terminal having a bandpass filter.

[0136] <<Evaluation>> The following measurements and evaluations were carried out, and the results are shown in Tables 1 and 2.

[0137] [Dielectric Constant, Dielectric Loss Tangent] The copper foil of single-sided copper-clad laminates and double-sided copper-clad laminates was removed with an aqueous solution of ferric chloride, washed with pure water, and dried to obtain films. The dielectric constant and dielectric loss tangent were measured using a resonance perturbation method at a frequency of 10 GHz. A 10 GHz cavity resonator (Kanto Electronics Application Development Co., Ltd., CP531) was connected to a network analyzer (Agilent Technology, Inc., E8363B). The film was inserted into the cavity and measured from the change in resonance frequency before and after insertion for 96 hours under a temperature of 25°C and a humidity of 60% RH. The dielectric constant and dielectric loss tangent of the film were measured.

[0138] [Insertion Loss] A receiving horn antenna was connected to Port 1 of a network analyzer (Agilent Technology "E8363B"), and a transmitting horn antenna was connected to Port 2. The receiving horn antenna and the transmitting horn antenna were arranged facing each other. A sample holder was fabricated by attaching a steel sheet to a radio wave absorber with openings. Both ends of the measurement sample were inserted into the openings of the two sample holders. The measurement sample held by the sample holder was placed between the receiving horn antenna and the transmitting horn antenna so that radio waves could pass through the measurement sample. Radio waves were transmitted and received, and the S-parameter S21 was measured. The amount of radio wave attenuation (insertion loss) when the measurement sample was installed was measured using the amount of transmission when the measurement sample was not installed as a reference.

[0139] In Table 1, the left side of formula (A) means "λ / (2×√ε) - λ / 50", and the right side of formula (A) means "λ / (2×√ε) + λ / 50". λ represents the transmission center wavelength, and ε represents the relative dielectric constant. In Tables 1 and 2, the transmission center frequency means the center frequency in the transmission band.

[0140]

[0141]

[0142] As shown in Table 1, in Examples 1 to 6, inorganic filler and resin were contained, the thickness d satisfied formula (A), the relative dielectric constant was 10 or more, and the dielectric loss tangent was 0.020 or less, and therefore the insertion loss at a transmission center frequency of 10 GHz was suppressed. On the other hand, in Comparative Example 1, no inorganic filler was contained, and therefore frequencies other than the transmission center frequency of 10 GHz were also transmitted. In Comparative Example 2, the thickness d did not satisfy formula (A), and therefore frequencies other than the transmission center frequency of 10 GHz were also transmitted. In Comparative Example 3, the dielectric loss tangent was greater than 0.020, and therefore frequencies other than the transmission center frequency of 10 GHz were also transmitted.

[0143] As shown in Table 2, Examples 101 to 106 included a resin substrate with a dielectric loss tangent of 0.020 or less and a metamaterial layer including a conductor pattern disposed on at least one surface of the resin substrate, and therefore were able to suppress insertion loss at a transmission center frequency of 10 GHz. On the other hand, Comparative Example 101 did not include a conductor pattern, and therefore transmitted frequencies other than the transmission center frequency of 10 GHz. Comparative Example 102 had a dielectric loss tangent of more than 0.020, and therefore was unable to suppress insertion loss at a transmission center frequency of 10 GHz.

[0144] In Example 102, the sheet resistivity of the conductor pattern was 1 Ω / □ or less, and compared to Example 101, the insertion loss at a transmission center frequency of 10 GHz was further suppressed.

[0145] The disclosure of Japanese Patent Application No. 2023-150290, filed on September 15, 2023, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. A film containing an inorganic filler and a resin, the thickness d of which satisfies the following formula (A), the relative dielectric constant is 10 or more, and the dielectric loss tangent is 0.020 or less: λ / (2×√ε)-λ / 50≦d≦λ / (2×√ε)+λ / 50 ... formula (A) In formula (A), d represents thickness in mm, λ represents the transmission center wavelength in mm, c represents the electromagnetic wave propagation velocity in m / s, f represents the transmission center frequency in GHz, and ε represents the relative dielectric constant.

2. The film according to claim 1, wherein the inorganic filler has a relative dielectric constant of 6 to 20,000.

3. The film according to claim 1 or 2, wherein the inorganic filler comprises at least one selected from the group consisting of barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, zirconium titanate, zinc titanate, titanium dioxide, magnesium oxide, alumina, tantalum pentoxide, and niobium pentoxide.

4. The film according to claim 1 or 2, wherein the inorganic filler has an average particle size of 0.01 μm to 10 μm.

5. The film according to claim 1 or 2, wherein the content of the inorganic filler is 1 volume % to 90 volume % based on the total amount of the film.

6. The film according to claim 1 or 2, wherein the resin comprises at least one selected from the group consisting of a thermoplastic resin, a thermoplastic elastomer, a semi-cured product of a thermosetting resin, a cured product of a thermosetting resin, a semi-cured product of a thermosetting elastomer, and a cured product of a thermosetting elastomer.

7. The film according to claim 1 or 2, having a thickness of 0.1 mm to 8 mm.

8. A laminate comprising: a resin substrate having a dielectric loss tangent of 0.020 or less; and a metamaterial layer disposed on at least one surface of the resin substrate, the metamaterial layer including a conductor pattern composed of at least one material selected from the group consisting of conductive materials and materials that change from nonconductors to conductors.

9. The laminate according to claim 8, wherein the resin substrate has a relative dielectric constant of 10 or more.

10. The laminate according to claim 8, wherein the resin substrate comprises an inorganic filler and a resin.

11. The laminate according to claim 10, wherein the inorganic filler has a relative dielectric constant of 6 to 20,000.

12. The laminate according to claim 10 or 11, wherein the inorganic filler comprises at least one selected from the group consisting of barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, zirconium titanate, zinc titanate, titanium dioxide, magnesium oxide, alumina, tantalum pentoxide, and niobium pentoxide.

13. The laminate according to claim 10 or 11, wherein the inorganic filler has an average particle size of 0.01 μm to 10 μm.

14. The laminate according to claim 10 or 11, wherein the content of the inorganic filler is 1 volume % to 90 volume % based on the total amount of the resin substrate.

15. The laminate according to claim 10 or 11, wherein the resin comprises at least one selected from the group consisting of a thermoplastic resin, a thermoplastic elastomer, a semi-cured thermosetting resin, a cured thermosetting resin, a semi-cured thermosetting elastomer, and a cured thermosetting elastomer.

16. The laminate according to claim 8 or 9, wherein the conductor pattern has an area resistivity of 1 Ω / □ or less.

17. A bandpass filter comprising the film of claim 1 or the laminate of claim 8.

18. The bandpass filter according to claim 17, wherein the center frequency of the transmission band is from 6 GHz to 24 GHz.

19. The bandpass filter according to claim 17, wherein the insertion loss at the center frequency of the passband ±5 GHz is 5 dB or more.

20. The bandpass filter according to claim 17, which is attached to the outside of an antenna.

21. A communications terminal comprising a communications circuit, an antenna, and the bandpass filter of claim 17 disposed outside said antenna.

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