Film and laminate

Abstract

A film and an application thereof, the film comprising a surface A and a surface B which are two virtual surfaces perpendicular to the thickness direction and which are respectively formed of a composition A and a composition B, wherein: the contained amount of at least one component A contained in the composition A becomes lower from the surface A to the surface B; the contained amount of at least one component B contained in the composition B becomes lower from the surface B to the surface A; and the dielectric loss tangent of the film is 0.010 or less.

Description

Films and Laminates

[0001] The present disclosure relates to films and laminates.

[0002] In recent years, the frequencies used in communication devices have tended to become very high. To suppress transmission loss in the high-frequency band, it is necessary to lower the relative permittivity and dielectric loss tangent of insulating materials used in circuit boards.

[0003] For example, Japanese Patent Application Laid-Open No. 2019-199612 describes a resin composition containing a styrene-based polymer, an inorganic filler, and a curing agent, wherein the styrene-based polymer is an acid-modified styrene-based polymer having a carboxyl group, the inorganic filler is silica and / or aluminum hydroxide, the particle size of the inorganic filler is 1 μm or less, the content of the inorganic filler is 20 to 80 parts by mass per 100 parts by mass of the styrene-based polymer, and the resin composition, in the form of a film having a thickness of 25 μm, satisfies specific formulas (A) and (B).

[0004] According to an embodiment of the present invention, there is provided a film having a low dielectric loss tangent and excellent suitability for laser processing. Also, according to another embodiment of the present invention, there is provided a laminate using the film.

[0005] The present disclosure includes the following aspects. <1> A film having two imaginary surfaces perpendicular to the thickness direction, namely, surface A made of composition A and surface B made of composition B, wherein the content of at least one component A contained in composition A decreases from surface A to surface B, and the content of at least one component B contained in composition B decreases from surface B to surface A, and the film has a dielectric loss tangent of 0.010 or less. <2> The film according to <1>, comprising, in the thickness direction, a layer A made of composition A and including surface A, a layer B made of composition B and including surface B, and a mixed layer located between layers A and B and containing components contained in compositions A and B. <3> The film according to <2>, wherein the average thickness of the mixed layer is 1.0% or more of the thickness of the film. <4> The film according to <2> or <3>, wherein the average thickness of at least one of layers A and B is 0.1 μm or more. <5> A value L obtained by subtracting the weight retention rate of layer A at 900°C from the weight retention rate of layer A at 440°C Ａ is the value L obtained by subtracting the weight retention rate of layer B at 900°C from the weight retention rate at 440°C. Ｂ The film according to any one of <2> to <4>, wherein the modulus of elasticity of Layer A at 160°C is greater than 1.2. <6> The film according to any one of <2> to <5>, wherein the ratio of the modulus of elasticity of Layer A at 160°C to the modulus of elasticity of Layer B at 160°C is 1.2 or more. <7> The film according to any one of <2> to <6>, wherein the modulus of elasticity of Layer B at 160°C is 100 MPa or less. <8> The film according to any one of <2> to <7>, wherein Layer B contains a thermoplastic resin containing a structural unit derived from a monomer having an aromatic hydrocarbon group. <9> The film according to any one of <2> to <8>, wherein Layer B contains a liquid crystal polymer. <10> The film according to any one of <2> to <9>, wherein Layer B contains an aromatic polyesteramide. <11> The film according to any one of <2> to <10>, wherein Layer B contains crosslinked resin particles. <12> The film according to any one of <2> to <11>, wherein Layer A contains a liquid crystal polymer. <13> The film according to any one of <2> to <12>, wherein Layer A contains an aromatic polyester amide. <14> A laminate comprising the film according to any one of <1> to <13> and a metal layer or metal wiring disposed on at least one surface of the film.

[0006] According to an embodiment of the present invention, there is provided a film having a low dielectric loss tangent and excellent suitability for laser processing. Also, according to another embodiment of the present invention, there is provided a laminate using the film.

[0007] The contents of the present disclosure will be described in detail below. The following description of the constituent elements may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In the present disclosure, 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 the present disclosure, the upper or lower limit described in 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 the present disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, in the notation of groups (atomic groups) in the present disclosure, notations that do not specify whether they are substituted or unsubstituted include both unsubstituted and substituted groups. For example, the term "alkyl group" includes not only alkyl groups without substituents (unsubstituted alkyl groups) but also alkyl groups with substituents (substituted alkyl groups). In the present disclosure, "(meth)acrylic" is a term used as a concept encompassing both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept encompassing both acryloyl and methacryloyl. Furthermore, the term "process" in the present disclosure 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 the present disclosure, "mass %" and "wt %" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Furthermore, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. Furthermore, unless otherwise specified, the weight average molecular weight (Mw) and number average molecular weight (Mn) in the present disclosure are molecular weights calculated using a gel permeation chromatography (GPC) analyzer equipped with a column of TSKgel Super HM-H (trade name of Tosoh Corporation), using a solvent of PFP (pentafluorophenol) / chloroform = 1 / 2 (mass ratio) and a differential refractometer, and converted using polystyrene as a standard substance.

[0008] [Film] The film according to the present disclosure has two imaginary surfaces perpendicular to the thickness direction, namely, surface A made of composition A and surface B made of composition B, in which the content of at least one component A contained in composition A decreases from surface A to surface B, and the content of at least one component B contained in composition B decreases from surface B to surface A, and the film has a dielectric loss tangent of 0.010 or less.

[0009] The present inventors have discovered that films having two or more layers, such as those described in JP 2019-199612 A, have problems with laser processing suitability. As a result of extensive research, the present inventors have discovered that by adopting the above-mentioned configuration, a film with excellent step followability can be provided. Note that "laser processing suitability" in this disclosure refers to a property that can reduce excessive cutting by a laser when performing laser cutting, particularly through-hole processing. Having excellent properties can be said to provide excellent processability for the cut portion to be formed into the desired shape during laser processing.

[0010] In the film according to the present disclosure, the content of at least one component A contained in composition A decreases from side A to side B, and the content of at least one component B contained in composition B decreases from side B to side A. This suggests that the compositional change within the film is gradual, resulting in excellent suitability for laser processing.

[0011] <Overall Structure> The film according to the present disclosure has two imaginary surfaces perpendicular to the thickness direction: surface A consisting of composition A and surface B consisting of composition B. The "two imaginary surfaces perpendicular to the thickness direction" may refer to the surfaces (two main surfaces) of the film, or may be a cross section obtained by cutting the film in a direction perpendicular to the thickness direction. The composition of the components contained in surface A and surface B can be confirmed by ATR-IR (attenuated total reflection infrared spectroscopy) or TOF-SIMS (time-of-flight secondary ion mass spectrometry).

[0012] In the film according to the present disclosure, the content of at least one component A contained in composition A decreases from side A to side B, and the content of at least one component B contained in composition B decreases from side B to side A. Note that the direction from side A to side B and the direction from side B to side A are both thickness directions.

[0013] Examples of embodiments in which the content of at least one component A contained in composition A decreases from side A to side B include an embodiment in which the content of component A decreases continuously and an embodiment in which the content of component A decreases stepwise. Similarly, examples of embodiments in which the content of at least one component B contained in composition B decreases from side B to side A include an embodiment in which the content of component B decreases continuously and an embodiment in which the content of component B decreases stepwise.

[0014] The following method can be used to confirm whether the content of at least one component A contained in composition A decreases from side A toward side B. The same method can also be used to confirm whether the content of at least one component B contained in composition B decreases from side B toward side A.

[0015] The composition is measured at an arbitrary thickness from one main surface of the film. The measured compositions at each thickness are compared to determine whether at least one component has decreased. The position and number of thicknesses at which the composition is measured are appropriately determined depending on the thickness of the film.

[0016] <Dielectric Loss Tangent> From the viewpoint of reducing transmission loss, the film according to the present disclosure has a dielectric loss tangent of 0.010 or less, preferably 0.005 or less, and more preferably greater than 0 and 0.002 or less.

[0017] In the present disclosure, the dielectric loss tangent is measured by the following method. The dielectric loss tangent is measured at a frequency of 10 GHz by the resonance perturbation method. A 10 GHz cavity resonator (Kanto Electronics Application Development Co., Ltd. CP531) is connected to a network analyzer (Agilent Technology Corporation "E8363B"), and a measurement sample (width: 2.0 mm x length: 80 mm) is inserted into the cavity resonator. The dielectric loss tangent of the measurement sample is measured from the change in resonance frequency before and after insertion for 96 hours in an environment of 25°C temperature and 60% RH.

[0018] A preferred embodiment of the film according to the present disclosure is a film comprising, in the thickness direction, a layer A made of composition A and including side A, a layer B made of composition B and including side B, and a mixed layer located between layer A and layer B and containing components contained in composition A and composition B.

[0019] The layer structure of the film and the thickness of each layer can be detected or determined by the following methods.

[0020] First, a cross-sectional sample of the film is cut out using a microtome, and the layer structure and thickness of each layer are determined using an optical microscope. If determination using an optical microscope is difficult, morphological observation using a scanning electron microscope (SEM) or component analysis using time-of-flight secondary ion mass spectrometry (TOF-SIMS) or the like may be used for determination.

[0021] <Layer A> Layer A is made of composition A and includes surface A. Layer A is a uniform layer having the composition A.

[0022] The components contained in composition A constituting layer A are not particularly limited as long as they can make the dielectric dissipation factor of the film 0.010 or less. Layer A preferably contains a polymer having a dielectric dissipation factor of 0.010 or less. While the term "composition" usually refers to the inclusion of multiple components, in the present disclosure, composition A may contain only one type of component, or two or more types of components.

[0023] The type of polymer having a dielectric loss tangent of 0.010 or less is not particularly limited, and known polymers can be used.

[0024] Examples of the polymer contained in Layer A include thermoplastic resins such as liquid crystal polymers, fluororesins, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyether ether ketone, polyolefin, polyamide, polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether and modified products thereof, and polyetherimide; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimides, and cyanate resins.

[0025] Among these, from the viewpoint of reducing the dielectric loss tangent of the film, Layer A preferably contains at least one polymer selected from the group consisting of a liquid crystal polymer, a fluororesin, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, and polyphenylene ether, and more preferably contains at least one polymer selected from the group consisting of a liquid crystal polymer and a fluororesin. From the viewpoint of film formability and mechanical strength, it is particularly preferable to contain a liquid crystal polymer, and from the viewpoint of dielectric loss tangent, it is particularly preferable to contain a fluororesin.

[0026] - Liquid Crystal Polymer - 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.

[0027] 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.

[0028] 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.

[0029] Furthermore, 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.

[0030] The liquid crystal polymer is preferably a wholly aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0031] 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.

[0032] For example, 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 an alkoxycarbonyl group or an aryloxycarbonyl 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 a haloformyl group. Aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids can be replaced with aromatic hydroxycarboxylic acid anhydrides and aromatic dicarboxylic acid anhydrides by converting the carboxy group to an acyloxycarbonyl group. Examples of polymerizable derivatives of compounds having a hydroxy group, such as aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines, include those obtained by acylation of the hydroxy group to an acyloxy group (acylated products). For example, aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines can be replaced with acylated products by acylation of the hydroxy group to an acyloxy group. Examples of polymerizable derivatives of compounds having an amino group, such as aromatic hydroxyamines and aromatic diamines, include those obtained by acylation of the amino group to an acylamino group (acylated products). For example, aromatic hydroxyamines and aromatic diamines can be substituted with their acylated products by acylation of the amino groups to convert them into acylamino groups.

[0033] The liquid crystal polymer preferably has crystallinity (for example, aromatic polyester amide, which will be described later). When the liquid crystal polymer has crystallinity, the dielectric loss tangent is further reduced.

[0034] The melting point of the liquid crystal polymer is preferably 250°C or higher, more preferably 250°C to 350°C, and even more preferably 260°C to 330°C.

[0035] 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.

[0036] 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 contained in the resin layer is preferably a wholly aromatic polyesteramide.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Ar １ When Ar is a p-phenylene group, unit 1 is, for example, a constitutional unit derived from p-hydroxybenzoic acid. １ When Ar is a 2,6-naphthylene group, unit 1 is, for example, a structural unit derived from 6-hydroxy-2-naphthoic acid. １is a 4,4'-biphenylylene group, unit 1 is, for example, a constitutional unit derived from 4'-hydroxy-4-biphenylcarboxylic acid.

[0043] 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.

[0044] 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.

[0045] In formula 3, Ar ３ is preferably a p-phenylene group or a 4,4'-biphenylylene group, and more preferably a p-phenylene group.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] The aromatic polyesteramide is preferably produced by melt-polymerizing raw material monomers corresponding to the structural units that constitute the aromatic polyesteramide.

[0051] Layer A may contain only one type of aromatic polyester amide, or may contain two or more types of aromatic polyester amide.

[0052] The content of the aromatic polyester amide is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, based on the total amount of Layer A. The upper limit of the content of the aromatic polyester amide is not particularly limited, and may be 100% by mass.

[0053] Liquid crystal polymers are preferably produced by melt-polymerizing raw material monomers corresponding to the structural units that constitute them. Melt polymerization may be carried out in the presence of a catalyst. Examples of this catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, and nitrogen-containing heterocyclic compounds such as 4-(dimethylamino)pyridine and 1-methylimidazole, with nitrogen-containing heterocyclic compounds being preferred. The melt polymerization may be further subjected to solid-state polymerization, if necessary.

[0054] The liquid crystal polymer has a flow initiation temperature of preferably 250° C. or higher, more preferably 250° C. or higher and 350° C. or lower, and even more preferably 260° C. or higher and 330° C. or lower. When the flow initiation temperature of the liquid crystal polymer is within the above range, the polymer has excellent solubility, heat resistance, strength, and rigidity, and the viscosity of the solution is appropriate.

[0055] The flow initiation temperature is also called the flow temperature or the flow temperature, and is measured using a capillary rheometer at a pressure of 9.8 MPa (100 kg / cm ２ When a liquid crystal polymer is melted and extruded through a nozzle having an inner diameter of 1 mm and a length of 10 mm while heating at a rate of 4°C / min under a load of 1000 kJ / cm2, the temperature rises to 4,800 Pa s (48,000 poise), and this temperature is used as a measure of the molecular weight of the liquid crystal polymer (see "Liquid Crystal Polymer - Synthesis, Molding, and Application" edited by Naoyuki Koide, CMC Co., Ltd., June 5, 1987, p. 95).

[0056] -Fluororesin- In the present disclosure, the type of fluororesin is not particularly limited, and known fluororesins can be used.

[0057] Fluorine resins include homopolymers and copolymers containing structural units derived from fluorinated α-olefin monomers, i.e., α-olefin monomers containing at least one fluorine atom, and copolymers containing structural units derived from fluorinated α-olefin monomers and structural units derived from non-fluorinated ethylenically unsaturated monomers reactive with the fluorinated α-olefin monomers.

[0058] Fluorinated α-olefin monomers include CF ２ =CF ２ , CHF=CF ２ , C.H. ２ =CF ２ , CHCl=CHF, CClF=CF ２ , CCl ２ =CF ２ , CClF=CClF, CHF=CCl ２ , C.H. ２ = CClF, CCl ２ = CClF, CF ３ CF = CF ２ , C.F. ３ CF = CHF, CF ３ CH=CF ２ , C.F. ３ CH=CH ２ , CHF ２ CH=CHF, CF ３ CF = CF ２ , and perfluoro(C2-C8 alkyl) vinyl ethers (e.g., perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and perfluorooctyl vinyl ether). Among these, the fluorinated α-olefin monomers include tetrafluoroethylene (CF ２ =CF ２ ), chlorotrifluoroethylene (CClF=CF ２ ), (perfluorobutyl)ethylene, vinylidene fluoride (CH ２ =CF ２ ), and hexafluoropropylene (CF ２ =CFCF ３) is preferably at least one monomer selected from the group consisting of: ethylene, propylene, butene, and ethylenically unsaturated aromatic monomers (for example, styrene and α-methylstyrene). The fluorinated α-olefin monomer may be used alone or in combination of two or more types. The non-fluorinated ethylenically unsaturated monomer may be used alone or in combination of two or more types.

[0059] Examples of fluororesins include polychlorotrifluoroethylene (PCTFE), poly(chlorotrifluoroethylene-propylene), poly(ethylene-tetrafluoroethylene) (ETFE), poly(ethylene-chlorotrifluoroethylene) (ECTFE), poly(hexafluoropropylene), poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene-ethylene-propylene), poly(tetrafluoroethylene-hexafluoropropylene) (FEP), poly(tetrafluoroethylene-propylene) (FEPM), poly(tetrafluoroethylene-perfluoropropylene vinyl ether), poly(tetrafluoroethylene-perfluoroalkyl vinyl ether) (PFA) (e.g., poly(tetrafluoroethylene-perfluoropropyl vinyl ether)), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-chlorotrifluoroethylene), perfluoropolyether, perfluorosulfonic acid, and perfluoropolyoxetane.

[0060] The fluororesin may have a structural unit derived from fluorinated ethylene or fluorinated propylene. The fluororesin may be used alone or in combination of two or more types.

[0061] The fluororesin is preferably FEP, PFA, ETFE, or PTFE. FEP is available from DuPont under the trade name TEFLON FEP, or from Daikin Industries, Ltd. under the trade name NEOFLON FEP. PFA is available from Daikin Industries, Ltd. under the trade name NEOFLON PFA, from DuPont under the trade name TEFLON PFA, or from Solvay Solexis under the trade name HYFLON PFA.

[0062] The fluororesin more preferably contains PTFE. The PTFE may be a PTFE homopolymer, a partially modified PTFE homopolymer, or a combination containing one or both of these. The partially modified PTFE homopolymer preferably contains less than 1 mass% of structural units derived from comonomers other than tetrafluoroethylene, based on the total mass of the polymer.

[0063] The fluororesin may be a crosslinkable fluoropolymer having a crosslinkable group. The crosslinkable fluoropolymer can be crosslinked by a conventionally known crosslinking method. One of the representative crosslinkable fluoropolymers is a fluoropolymer having (meth)acryloyloxy. For example, the crosslinkable fluoropolymer is a fluoropolymer having the formula: H ２ C=CR'COO-(CH ２ ) ｎ -R-(CH ２ ) ｎ -OOCR'=CH ２ In this formula, R is an oligomer chain containing constitutional units derived from fluorinated α-olefin monomers, and R′ is H or —CH ３ and n is 1 to 4. R may be a fluorine-containing oligomer chain containing a structural unit derived from tetrafluoroethylene.

[0064] A crosslinked fluoropolymer network can be formed by exposing a fluoropolymer having (meth)acryloyloxy groups to a free radical source to initiate a radical crosslinking reaction via the (meth)acryloyloxy groups on the fluororesin. The free radical source is not particularly limited, but suitable examples include a photoradical polymerization initiator or an organic peroxide. Suitable photoradical polymerization initiators and organic peroxides are well known in the art. Crosslinkable fluoropolymers are commercially available, for example, Viton B manufactured by DuPont.

[0065] Polymer of a Compound Having a Cyclic Aliphatic Hydrocarbon Group and a Group Having an Ethylenically Unsaturated Bond Examples of polymers of compounds having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond include thermoplastic resins having structural units derived from cyclic olefin monomers such as norbornene or polycyclic norbornene monomers. Polymers of compounds having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be ring-opening polymers of the above-mentioned cyclic olefins or hydrogenated ring-opening copolymers using two or more cyclic olefins, or may be addition polymers of cyclic olefins and aromatic compounds having an ethylenically unsaturated bond such as linear olefins or vinyl groups. Furthermore, a polar group may be introduced into the polymer of a compound having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond. Polymers of compounds having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be used alone or in combination of two or more.

[0066] The ring structure of the cycloaliphatic hydrocarbon group may be a monocycle, a fused ring in which two or more rings are fused, or a bridged ring. Examples of the ring structure of the cycloaliphatic hydrocarbon group include a cyclopentane ring, a cyclohexane ring, a cyclooctane ring, an isoborone ring, a norbornane ring, and a dicyclopentane ring. The compound having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond is not particularly limited, and examples thereof include (meth)acrylate compounds having a cycloaliphatic hydrocarbon group, (meth)acrylamide compounds having a cycloaliphatic hydrocarbon group, and vinyl compounds having a cycloaliphatic hydrocarbon group. Among these, (meth)acrylate compounds having a cycloaliphatic hydrocarbon group are preferred. Furthermore, the compound having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be a monofunctional ethylenically unsaturated compound or a polyfunctional ethylenically unsaturated compound. The number of cycloaliphatic hydrocarbon groups in the compound having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be one or more, and may be two or more. The polymer of a compound having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be a polymer obtained by polymerizing at least one compound having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, and may be a polymer of a compound having two or more types of cycloaliphatic hydrocarbon groups and a group having an ethylenically unsaturated bond, or may be a copolymer with another ethylenically unsaturated compound that does not have a cycloaliphatic hydrocarbon group. Furthermore, the polymer of a compound having a cycloaliphatic hydrocarbon group and a group having an ethylenically unsaturated bond is preferably a cycloolefin polymer.

[0067] -Polyphenylene Ether- From the viewpoints of dielectric dissipation factor and heat resistance, the average number of phenolic hydroxyl groups at the molecular terminals of the polyphenylene ether per molecule (number of terminal hydroxyl groups) is preferably 1 to 5, and more preferably 1.5 to 3. The number of terminal hydroxyl groups of the polyphenylene ether can be determined, for example, from the specification value of the polyphenylene ether product. The number of terminal hydroxyl groups is expressed, for example, as the average number of phenolic hydroxyl groups per molecule of all polyphenylene ethers present in 1 mole of the polyphenylene ether. One type of polyphenylene ether may be used alone, or two or more types may be used in combination.

[0068] Examples of polyphenylene ethers include polyphenylene ethers composed of 2,6-dimethylphenol and at least one of a bifunctional phenol and a trifunctional phenol, and poly(2,6-dimethyl-1,4-phenylene oxide). More specifically, the polyphenylene ether is preferably a compound having a structure represented by the formula (PPE).

[0069]

[0070] In formula (PPE), X represents an alkylene group having 1 to 3 carbon atoms or a single bond, m represents an integer of 0 to 20, n represents an integer of 0 to 20, and the sum of m and n represents an integer of 1 to 30. Examples of the alkylene group in X include a dimethylmethylene group.

[0071] When the polyphenylene ether is heat-cured after film formation, the weight-average molecular weight (Mw) is preferably 500 to 5,000, more preferably 500 to 3,000, from the viewpoints of heat resistance and film formability. When the polyphenylene ether is not heat-cured, the weight-average molecular weight (Mw) is not particularly limited, but is preferably 3,000 to 100,000, more preferably 5,000 to 50,000.

[0072] - Aromatic polyether ketone - The aromatic polyether ketone is not particularly limited, and known aromatic polyether ketones can be used. The aromatic polyether ketone is preferably polyether ether ketone. Polyether ether ketone is a type of aromatic polyether ketone, and is a polymer in which bonds are arranged in the following order: ether bond, ether bond, and carbonyl bond. The bonds are preferably connected by a divalent aromatic group. The aromatic polyether ketone may be used alone or in combination of two or more types.

[0073] Examples of aromatic polyether ketones include polyether ether ketone (PEEK) having a chemical structure represented by the following formula (P1), polyether ketone (PEK) having a chemical structure represented by the following formula (P2), polyether ketone ketone (PEKK) having a chemical structure represented by the following formula (P3), polyether ether ketone ketone (PEEKK) having a chemical structure represented by the following formula (P4), and polyether ketone ether ketone ketone (PEKEKK) having a chemical structure represented by the following formula (P5).

[0074]

[0075] In terms of mechanical properties, n in each of the formulae (P1) to (P5) is preferably 10 or greater, and more preferably 20 or greater. On the other hand, in terms of ease of production of the aromatic polyether ketone, n is preferably 5,000 or less, and more preferably 1,000 or less. That is, n is preferably 10 to 5,000, and more preferably 20 to 1,000.

[0076] As described above, Layer A preferably contains at least one polymer having a dielectric dissipation factor of 0.010 or less. When Layer A contains a polymer having a dielectric dissipation factor of 0.010 or less, the content of the polymer having a dielectric dissipation factor of 0.010 or less is preferably 10% by mass to 90% by mass, more preferably 15% by mass to 85% by mass, even more preferably 15% by mass to 80% by mass, and particularly preferably 15% by mass to 50% by mass, relative to the total mass of Layer A, from the viewpoints of the dielectric dissipation factor of the film and adhesion to the metal layer.

[0077] Filler: From the viewpoint of the thermal expansion coefficient and adhesion to the metal layer, the layer A may contain at least one filler.

[0078] The filler may be particulate or fibrous. The filler may be inorganic or organic. From the viewpoint of the dielectric loss tangent and step conformability of the film, the filler is preferably an organic filler.

[0079] Known organic fillers can be used as the organic filler, and examples of the organic filler material include polyethylene, polystyrene, urea-formalin filler, polyester, cellulose, acrylic resin, fluororesin, hardened epoxy resin, crosslinked benzoguanamine resin, crosslinked acrylic resin, liquid crystal polymer, and materials containing two or more of these.

[0080] The organic filler may be fibrous, such as nanofibers, or hollow resin particles. Among these, from the viewpoint of the dielectric loss tangent and step conformability of the film, the organic filler is preferably fluororesin particles, polyester-based resin particles, polyethylene particles, liquid crystal polymer particles, or nanofibers of cellulose-based resins, more preferably polytetrafluoroethylene particles, polyethylene particles, or liquid crystal polymer particles, and particularly preferably liquid crystal polymer particles. Here, the liquid crystal polymer particles refer to, but are not limited to, powdered liquid crystals obtained by polymerizing a liquid crystal polymer and pulverizing it with a pulverizer or the like. The liquid crystal polymer particles are preferably smaller than the thickness of each layer.

[0081] The average particle size of the organic filler is preferably 5 nm to 20 μm, more preferably 100 nm to 10 μm, from the viewpoints of the dielectric loss tangent of the film, suitability for laser processing, and ability to conform to unevenness.

[0082] As the inorganic filler, known inorganic fillers can be used. Examples of the material of the inorganic filler include BN and Al. ２ O ３ , AlN, TiO ２, SiO ２ , barium titanate, strontium titanate, aluminum hydroxide, calcium carbonate, and materials containing two or more of these.

[0083] Among these, from the viewpoints of the thermal expansion coefficient and adhesion to the metal layer, the inorganic filler is preferably metal oxide particles or fibers, more preferably silica particles, titania particles, or glass fibers, and particularly preferably silica particles or glass fibers.

[0084] The average particle size of the inorganic filler is preferably about 20% to about 40% of the thickness of Layer A, and may be selected to be, for example, 25%, 30%, or 35% of the thickness of Layer A. When the particles or fibers are flat, the average particle size indicates the length in the direction of the short side.

[0085] Furthermore, from the viewpoints of the thermal expansion coefficient and adhesion to the metal layer, the average particle size of the inorganic filler is preferably 5 nm to 20 μm, more preferably 10 nm to 10 μm, even more preferably 20 nm to 1 μm, and particularly preferably 25 nm to 500 nm.

[0086] Other Additives Layer A may contain additives other than the components described above. Known additives can be used as the other additives. Specific examples include curing agents, leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, and colorants.

[0087] <Layer B> Layer B is made of composition B and includes surface B. Layer B is a uniform layer having the composition B.

[0088] The components contained in composition B constituting layer B are not particularly limited as long as they can make the dielectric loss tangent of the film 0.010 or less. Layer B preferably contains at least one polymer.

[0089] Layer B preferably contains a thermoplastic resin from the viewpoints of the dielectric loss tangent, laser processing suitability, and step-conforming ability of the film. The thermoplastic resin may be a thermoplastic elastomer. The term "elastomer" refers to a polymer compound that exhibits elastic deformation. That is, an elastomer refers to a polymer compound that has the property of deforming in response to the application of an external force and recovering its original shape in a short time when the external force is removed.

[0090] Examples of thermoplastic resins include polyurethane resins, polyester resins, (meth)acrylic resins, polystyrene resins, fluororesins, polyimide resins, fluorinated polyimide resins, polyamide resins, polyamideimide resins, polyetherimide resins, cellulose acylate resins, polyurethane 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.

[0091] The thermoplastic elastomer is not particularly limited, and examples thereof include elastomers containing styrene-derived repeating units (polystyrene-based elastomers), polyester-based elastomers, polyolefin-based elastomers, polyurethane-based elastomers, polyamide-based elastomers, polyacrylic elastomers, silicone-based elastomers, and polyimide-based elastomers. The thermoplastic elastomer may be a hydrogenated product. Examples of polystyrene-based 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), as well as hydrogenated products thereof.

[0092] Among these, from the viewpoints of the dielectric loss tangent, laser processing suitability, and step-conforming ability of the film, Layer B preferably contains a thermoplastic resin containing a structural unit derived from a monomer having an aromatic hydrocarbon group, more preferably contains a polystyrene-based elastomer, and particularly preferably contains a hydrogenated styrene-ethylene-butylene-styrene block copolymer. Furthermore, from the viewpoints of the dielectric loss tangent, laser processing suitability, and step-conforming ability of the film, Layer B preferably contains a hydrogenated polystyrene-based elastomer.

[0093] The content of the thermoplastic resin is not particularly limited, but from the viewpoints of the dielectric loss tangent of the film, suitability for laser processing, and adhesion to the metal layer, it is preferably 50% by mass to 100% by mass, and more preferably 60% by mass to 90% by mass, relative to the total mass of Layer B.

[0094] From the viewpoint of the dielectric loss tangent of the film, Layer B preferably contains a polymer having a dielectric loss tangent of 0.010 or less. Preferred embodiments of the polymer having a dielectric loss tangent of 0.010 or less are the same as preferred embodiments of the polymer having a dielectric loss tangent of 0.010 or less that can be contained in Layer A.

[0095] Among these, Layer B preferably contains a liquid crystal polymer, and more preferably contains an aromatic polyester amide.

[0096] When Layer B contains a polymer having a dielectric dissipation factor of 0.010 or less, the content of the polymer having a dielectric dissipation factor of 0.010 or less is not particularly limited, but from the viewpoints of the dielectric dissipation factor of the film, suitability for laser processing, and adhesion to the metal layer, the content is preferably 10% by mass to 100% by mass, more preferably 10% by mass to 70% by mass, and particularly preferably 10% by mass to 60% by mass, relative to the total mass of Layer B.

[0097] From the viewpoints of the dielectric loss tangent of the film, suitability for laser processing, adhesion to the metal layer, and ability to conform to uneven surfaces, it is more preferable that Layer B contains a filler. Preferred embodiments of the filler used in Layer B are the same as the preferred embodiments of the filler that can be contained in Layer A, except as described below. Preferred examples of the filler used in Layer B include particles of the thermoplastic resin described above. Furthermore, from the viewpoints of the dielectric loss tangent of the film, suitability for laser processing, and ability to conform to uneven surfaces, it is preferable that at least one of the polymer and the filler contained in Layer B is a polymer having a dielectric loss tangent of 0.01 or less, and more preferably a liquid crystal polymer.

[0098] Furthermore, from the viewpoints of the dielectric loss tangent, laser processing suitability, and step-conforming ability of the film, Layer B preferably contains crosslinked resin particles as a filler. The crosslinked resin in the crosslinked resin particles is not particularly limited, and known crosslinked resins can be used. For example, it may be a crosslinked resin obtained by using a crosslinking agent during polymerization, or a crosslinked resin obtained by reacting a resin with a crosslinking agent. Among these, from the viewpoints of the dielectric loss tangent, laser processing suitability, and step-conforming ability of the film, the above-mentioned thermoplastic elastomer particles are preferred as the crosslinked resin particles, polystyrene-based elastomer particles are more preferred, and hydrogenated polystyrene-based elastomers are particularly preferred.

[0099] Layer B may contain only one type of filler or may contain two or more types of filler. From the viewpoints of laser processing suitability and adhesion to the metal layer, the content of the filler in Layer B is preferably 10% by mass to 90% by mass, and more preferably 20% by mass to 80% by mass, relative to the total mass of Layer B.

[0100] Layer B may contain other additives in addition to those described above. Preferred embodiments of the other additives used in Layer B are the same as the preferred embodiments of the other additives used in Layer A, except as described below.

[0101] Layer B is preferably a surface layer (outermost layer). When the film is used as a laminate (metal layer-attached laminate) having a layer structure of metal layer / film, for example, another metal layer or metal layer-attached laminate may be further disposed on the Layer B side. In this case, interfacial breakdown between Layer B and the other metal layer in the laminate is suppressed, and adhesion to the metal layer is improved.

[0102] - Relationship between Layer A and Layer B - (Average Thickness) The average thickness of at least one of Layer A and Layer B is preferably 0.1 μm or more.

[0103] The average thickness of Layer A is preferably greater than the average thickness of Layer B from the viewpoints of the dielectric loss tangent of the film and adhesion to metal. Ａ and the average thickness T of layer B Ｂ T, which is the ratio of Ａ / T Ｂ From the viewpoint of the dielectric loss tangent of the film and the adhesion to metal, the value of is preferably 0.8 to 10, more preferably 1 to 5, even more preferably more than 1 and not more than 3, and particularly preferably more than 1 and not more than 2.

[0104] The average thickness of Layer A is not particularly limited, but from the viewpoints of the dielectric loss tangent of the film and the adhesion to the metal layer, it is preferably 0.1 μm or more, more preferably 5 μm to 90 μm, even more preferably 10 μm to 70 μm, and particularly preferably 15 μm to 60 μm.

[0105] The average thickness of Layer B is not particularly limited, but from the viewpoints of the dielectric loss tangent of the film, suitability for laser processing, and ability to follow unevenness, it is preferably 0.1 μm or more, more preferably 1 μm to 90 μm, even more preferably 5 μm to 60 μm, and particularly preferably 10 μm to 40 μm.

[0106] The method for measuring the average thickness of each layer in the film according to the present disclosure is as follows: The film is cut with a microtome, and the cross section is observed under an optical microscope to evaluate the thickness of each layer. Cross-sectional samples are cut out from three or more locations, and the thickness is measured at three or more points on each cross section, and the average value of these measurements is taken as the average thickness.

[0107] (Weight Residual Rate) From the viewpoints of the dielectric loss tangent of the film, the suitability for laser processing, and the ability to follow unevenness, the film according to the present disclosure has a value L obtained by subtracting the weight residual rate of the layer A at 900°C from the weight residual rate at 440°C. Ａ is the value L obtained by subtracting the weight residual rate of layer B at 900°C from the weight residual rate at 440°C. Ｂ In the present disclosure, L Ａ From L Ｂ The value obtained by subtracting (L Ａ -L Ｂ ) is not particularly limited, but from the viewpoints of laser processing suitability and step followability, it is preferably less than 100%, more preferably 95% or less, even more preferably 10% to 90%, and particularly preferably 10% to 85%.

[0108] L Ａ From the viewpoints of the dielectric loss tangent of the film, suitability for laser processing, and ability to follow unevenness, L is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% to 100%. Ｂ is preferably 5% or more, more preferably 8% to 80%, and particularly preferably 10% to 60%, from the viewpoints of the dielectric loss tangent of the film, the suitability for laser processing, and the ability to follow unevenness.

[0109] In the present disclosure, the method for measuring the value obtained by subtracting the weight residual rate at 900°C from the weight residual rate at 440°C of Layer A or Layer B is as follows: Layer A or Layer B is cut from the film, 5 mg of which is placed on a platinum pan, and measurement is performed using a differential thermobalance (TG-DTA) (TG-8120, manufactured by Rigaku Corporation) at a heating rate of 10°C / min and a measurement temperature of 25°C to 900°C. The weight residual rate (%, L Ａ or L Ｂ ) = Weight remaining rate (%) at 440°C - Weight remaining rate (%) at 900°C

[0110] (Elastic Modulus) In the film according to the present disclosure, from the viewpoints of the dielectric loss tangent, laser processing suitability, and step-conforming ability of the film, the elastic modulus of Layer A at 160° C. is preferably greater than the elastic modulus of Layer B at 160° C. From the viewpoints of laser processing suitability and step-conforming ability, the ratio of the elastic modulus of Layer A at 160° C. to the elastic modulus of Layer B at 160° C. is preferably 1.2 or greater, more preferably 5 to 1,000, and even more preferably 100 to 500.

[0111] From the viewpoints of laser processing suitability and step conformability, the elastic modulus of Layer A at 160°C is preferably 100 MPa to 2,500 MPa, preferably 200 MPa to 2,000 MPa, more preferably 300 MPa to 1,500 MPa, and particularly preferably 500 MPa to 1,000 MPa. From the viewpoints of laser processing suitability and step conformability, the elastic modulus of Layer B at 160°C is preferably 100 MPa or less, more preferably 10 MPa or less, even more preferably 0.001 MPa to 10 MPa, and particularly preferably 0.5 MPa to 5 MPa.

[0112] In the present disclosure, the modulus of elasticity is measured by the following method. First, a cross section of a film is cut using a microtome or the like, and Layer A or Layer B is identified using an optical microscope. Next, the modulus of elasticity of the identified Layer A or Layer B is measured as the indentation modulus using a nanoindentation method. The indentation modulus is measured using a microhardness tester (product name "DUH-W201", manufactured by Shimadzu Corporation) at 160°C by applying a load with a Vickers indenter at a loading rate of 0.28 mN / s, holding a maximum load of 10 mN for 10 seconds, and then unloading at a loading rate of 0.28 mN / s.

[0113] <Mixed Layer> The mixed layer preferably contains components contained in Composition A and Composition B. The mixed layer preferably contains at least one of the components contained in Composition A and at least one of the components contained in Composition B. When a mixed layer containing components contained in Composition A and Composition B is present in the film, the composition changes more slowly in the thickness direction of the film, improving the suitability for laser processing.

[0114] The mixed layer may be a layer having a uniform composition or a layer having a non-uniform composition, as long as it contains the components contained in Composition A and Composition B.

[0115] The presence or absence of a mixed layer in a film can be confirmed by the following method.

[0116] The composition is measured at any thickness from one main surface of the film. Based on the measured composition at each thickness, it is determined whether or not a composition containing the components contained in Layer A and Layer B is present. The position and number of thicknesses at which the composition is measured are appropriately determined depending on the thickness of the film.

[0117] From the viewpoints of laser processing suitability and interlayer adhesion, the average thickness of the mixed layer is preferably 1.0% or more, more preferably 3.0% or more, of the thickness of the film. The upper limit of the average thickness of the mixed layer is not particularly limited, and is, for example, 95%.

[0118] <Layer C> The film according to the present disclosure preferably further includes Layer C, and more preferably includes Layer B, the mixed layer, Layer A, and Layer C in this order from the viewpoint of adhesion to the metal layer. Layer C is preferably an adhesive layer. Layer C is also preferably a surface layer (outermost layer). Layer C preferably contains a polymer from the viewpoint of the dielectric tangent of the film and laser processing suitability. Preferred aspects of the polymer used in Layer C are the same as the preferred aspects of the polymer used in Layer A having a dielectric tangent of 0.010 or less, except as described below. The polymer contained in Layer C may be the same as or different from the polymer contained in Layer A or Layer B, but from the viewpoint of adhesion between Layer A and Layer C, it is preferable that Layer C contains the same polymer as that contained in Layer A.

[0119] Furthermore, from the viewpoints of the dielectric loss tangent of the film and suitability for laser processing, Layer C preferably contains a polymer having an aromatic ring, and more preferably contains a polymer that is a resin having an aromatic ring and an ester bond and an amide bond. Furthermore, Layer C preferably contains an epoxy resin to bond the metal layer and Layer A. The epoxy resin is preferably a crosslinked product of a multifunctional epoxy compound. A multifunctional epoxy compound refers to a compound having two or more epoxy groups. The number of epoxy groups in the multifunctional epoxy compound is preferably 2 to 4.

[0120] Examples of the polyfunctional epoxy compound include a polyfunctional epoxy compound having a glycidyl ether group, a polyfunctional epoxy compound having a glycidyl ester group, and a polyfunctional epoxy compound having a glycidylamino group.

[0121] Examples of polyfunctional epoxy compounds having a glycidyl ether group include ethylene glycol diglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, trimethylolpropane polyglycidyl ether, polyglycerin polyglycidyl ether, glycerin polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerin polyglycidyl ether, sorbitol polyglycidyl ether, polybutadiene diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, and 1,4-butanediol diglycidyl ether.

[0122] Examples of polyfunctional epoxy compounds having a glycidyl ester group include phthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, and dimer acid diglycidyl ester.

[0123] Examples of compounds having a glycidylamino group include N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane and 4,4'-methylenebis(N,N-diglycidylaniline).

[0124] An example of a polyfunctional epoxy compound having a glycidyl ether group and a glycidylamino group is N,N-diglycidyl-4-glycidyloxyaniline.

[0125] Among these, from the viewpoints of curability and interaction with the metal surface, the epoxy resin is preferably a crosslinked product of a polyfunctional epoxy compound having a glycidylamino group, and more preferably a crosslinked product of at least one selected from the group consisting of N,N-diglycidyl-4-glycidyloxyaniline and N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane.

[0126] In particular, from the viewpoints of the dielectric loss tangent of the film, suitability for laser processing, and adhesion to the metal layer, it is preferable that Layer C contains an aromatic polyester amide and an epoxy resin.

[0127] Layer C may contain a filler. Preferred embodiments of the filler used in Layer C are the same as the preferred embodiments of the filler used in Layer B, except as described below.

[0128] The filler content in Layer C is not particularly limited and can be set as desired, but when metal layers are provided on both sides of the film, it is preferable that the filler content be less than that in Layer A from the viewpoint of adhesion to the metal layers.

[0129] Layer C may contain other additives in addition to those described above. Preferred embodiments of the other additives used in Layer C are the same as the preferred embodiments of the other additives used in Layer A, except as described below.

[0130] The average thickness of Layer C is preferably smaller than the average thickness of Layer A from the viewpoints of the dielectric loss tangent of the film and adhesion to metal. Ａ and the average thickness T of layer C Ｃ T, which is the ratio of Ａ / T Ｃ From the viewpoint of the dielectric loss tangent of the film and the adhesion to the metal layer, the value of is preferably greater than 1, more preferably 2 to 100, even more preferably 2.5 to 20, and particularly preferably 3 to 10. Ｂ and the average thickness T of layer C Ｃ T, which is the ratio of Ｂ / T Ｃ From the viewpoints of the dielectric loss tangent of the film and the adhesion to the metal layer, the value of is preferably greater than 1, more preferably 2 to 100, even more preferably 2.5 to 20, and particularly preferably 3 to 10. Furthermore, from the viewpoints of the dielectric loss tangent of the film and the adhesion to the metal layer, the average thickness of Layer C is preferably 0.1 μm to 20 μm, more preferably 0.5 μm to 15 μm, even more preferably 1 μm to 10 μm, and particularly preferably 2 μm to 8 μm.

[0131] The average thickness of the film according to the present disclosure is preferably 6 μm to 200 μm, more preferably 12 μm to 100 μm, and particularly preferably 20 μm to 80 μm, from the viewpoints of strength and electrical properties (characteristic impedance) when laminated with a metal layer.

[0132] The average thickness of the film is determined by measuring any five points using an adhesive film thickness meter, for example, an electronic micrometer (product name "KG3001A" manufactured by Anritsu Corporation), and averaging these values.

[0133] <Film Manufacturing Method> [Film Production] The film manufacturing method according to the present disclosure is not particularly limited, and known methods can be used. Suitable examples of the film manufacturing method according to the present disclosure include co-casting, sequential casting, multi-layer coating, sequential coating, and co-extrusion. Examples of combinations of these include a combination of co-extrusion and coating. Among these, the co-casting method or multi-layer coating method is particularly preferred for producing relatively thin films, and the co-extrusion method is particularly preferred for producing thick films. When producing by the co-casting method or multi-layer coating method, it is preferable to use a layer A-forming composition, a layer B-forming composition, a layer C-forming composition, etc., in which the components of each layer are dissolved or dispersed in a solvent. The method for forming a mixed layer will be described later.

[0134] 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-butylphosphate, and two or more of these may be used.

[0135] The solvent preferably contains an aprotic compound (particularly preferably an aprotic compound having no halogen atoms) because it is less corrosive and easier to handle. 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, the aprotic compound preferably contains an amide such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, or N-methylpyrrolidone, or an ester such as γ-butyrolactone, because they easily dissolve the liquid crystal polymer, and N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone are more preferred.

[0136] Furthermore, since the solvent easily dissolves the above-mentioned polymers such as liquid crystal polymers, it is preferable that the solvent contains a compound having a dipole moment of 3 to 5. 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 above-mentioned aprotic compound.

[0137] Furthermore, the solvent preferably contains a compound having a boiling point of 220°C or lower at 1 atmosphere, as this is easy to remove. 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.

[0138] Furthermore, when the film manufacturing method according to the present disclosure is produced by the co-casting method, multilayer coating method, co-extrusion method, or the like, a support may be used. Furthermore, when a metal layer (metal foil) or the like used in the laminate described below is used as the support, it may be used as is without peeling. Examples of the support include a metal drum, a metal band, a glass plate, a resin film, or a metal foil. Among these, a metal drum, a metal band, and a resin film are preferred. Examples of resin films include polyimide (PI) films, and examples of commercially available products include U-PIREX S and U-PIREX R manufactured by Ube Industries, Ltd., Kapton manufactured by Toray DuPont Co., Ltd., and IF30, IF70, and LV300 manufactured by SKC Kolon PI. Furthermore, a surface treatment layer may be formed on the surface of the support to facilitate peeling. Examples of the surface treatment layer include hard chrome plating, fluororesin, and the like. The average thickness of the support is not particularly limited, but is preferably 25 μm to 75 μm, more preferably 50 μm to 75 μm.

[0139] The method for removing at least a part of the solvent from the cast or coated film-like composition (cast film or coating film) is not particularly limited, and any known drying method can be used.

[0140] [Stretching] The film according to the present disclosure can be appropriately combined with stretching in order to control molecular orientation and adjust the linear expansion coefficient and mechanical properties. The stretching method is not particularly limited, and known methods can be used. The stretching may be performed in a solvent-containing state or in a dry film state. Stretching in a solvent-containing state may be performed by gripping the film and stretching it, or by utilizing autogenous shrinkage due to drying without stretching it. Stretching is particularly effective for improving the breaking elongation and breaking strength when the film brittleness has decreased due to the addition of an inorganic filler or the like.

[0141] The film manufacturing method according to the present disclosure may also include a step of polymerization by light or heat, as necessary. The light irradiation means and heat application means are not particularly limited, and known light irradiation means such as a metal halide lamp and known heat application means such as a heater can be used. The light irradiation conditions and heat application conditions are not particularly limited, and can be performed at a desired temperature and time in a known atmosphere.

[0142] [Heat Treatment] The film manufacturing method according to the present disclosure preferably includes a step of heat treating (annealing) the film. Specifically, the heat treatment temperature in the heat treatment step is preferably 260°C to 370°C, more preferably 280°C to 360°C, and even more preferably 300°C to 350°C, from the viewpoints of dielectric loss tangent and peel strength. The heat treatment time is preferably 15 minutes to 10 hours, and more preferably 30 minutes to 5 hours. Furthermore, the film manufacturing method according to the present disclosure may include other known steps as necessary.

[0143] [Formation of mixed layer] In the film of the present disclosure, the method for forming the mixed layer is not particularly limited, but examples thereof include a method of laminating and drying each layer in a state containing a solvent and having fluidity; a method of laminating and drying another layer in a state containing residual solvent; a method of laminating and drying a composition containing a solvent that swells or dissolves a layer that does not contain residual solvent; and a method of laminating each layer and then applying energy such as heat or sound waves to mix the layers.In particular, a method using a solvent is preferred.In addition, a method of adjusting the SP value, etc. of the material of each layer and a method of adding a common material to each layer to promote mixing are also effective.

[0144] The film according to the present disclosure can be used for various applications, and in particular, can be suitably used as a film for electronic components such as printed wiring boards, and can be more suitably used for flexible printed circuit boards. The film according to the present disclosure can also be suitably used as a film for bonding metals.

[0145] (Laminate) The laminate according to the present disclosure may be any laminate comprising a film according to the present disclosure laminated thereon, but is preferably a laminate comprising a film according to the present disclosure and a metal layer or metal wiring disposed on at least one surface of the film. The laminate according to the present disclosure preferably comprises a film according to the present disclosure and a metal layer disposed on the layer B side of the film, and more preferably the metal layer is a copper layer. The metal layer disposed on the layer B side is preferably a metal layer disposed on the surface of layer B. The laminate according to the present disclosure preferably comprises a film according to the present disclosure having layer B, layer A, and layer C in this order in the thickness direction, and a metal layer disposed on the layer B side of the film and a metal layer disposed on the layer C side of the film, and more preferably both metal layers are copper layers. The metal layer disposed on the layer C side is preferably a metal layer disposed on the surface of layer C, and more preferably the metal layer disposed on the layer B side is a metal layer disposed on the surface of layer B, and the metal layer disposed on the layer C side is a metal layer disposed on the surface of layer C. Furthermore, the metal layer disposed on the surface on the layer B side and the metal layer disposed on the surface on the layer C side may be metal layers of the same material, thickness, and shape, or metal layers of different materials, thicknesses, and shapes. From the viewpoint of adjusting the characteristic impedance, the metal layer disposed on the surface on the layer B side and the metal layer disposed on the surface on the layer C side may be metal layers of different materials and thicknesses, and a metal layer may be laminated on only one side of layer B or layer C. Furthermore, from the viewpoint of adjusting the characteristic impedance, a preferred embodiment is one in which a metal layer is laminated on one side of layer B or layer C and another film is laminated on the other side.

[0146] The method for attaching the film according to the present disclosure to the metal layer is not particularly limited, and any known lamination method can be used.

[0147] When the metal layer is the copper layer, the peel strength between the film and the copper layer is preferably 0.5 kN / m or more, more preferably 0.7 kN / m or more, even more preferably 0.7 kN / m to 2.0 kN / m, and particularly preferably 0.9 kN / m to 1.5 kN / m.

[0148] In the present disclosure, the peel strength between a film and a metal layer (e.g., a copper layer) is measured by the following method: A 1.0 cm wide peel test piece is prepared from a laminate of a film and a metal layer, the film is fixed to a flat plate with double-sided adhesive tape, and the strength (kN / m) is measured when the film is peeled from the metal layer at a rate of 50 mm / min by the 180° method in accordance with JIS C 5016 (1994).

[0149] The surface roughness Rz of the metal layer on the side in contact with the film is preferably less than 1 μm, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less, from the viewpoint of reducing transmission loss of high-frequency signals. Note that, since the smaller the surface roughness Rz of the metal layer, the better, no lower limit is particularly set, but it may be, for example, 0 or more.

[0150] In this disclosure, "surface roughness Rz" refers to the sum, expressed in micrometers, of the maximum peak height and the maximum valley depth observed on a roughness curve over a reference length. In this disclosure, the surface roughness Rz of a metal layer (e.g., a copper layer) is measured using the following method. A non-contact surface / layer cross-sectional shape measurement system, VertScan (manufactured by Ryoka Systems Co., Ltd.), is used to measure an area 465.48 μm long and 620.64 μm wide, to create a roughness curve and a mean line of the roughness curve for the surface of the object to be measured (the metal layer). A portion corresponding to the reference length is extracted from the roughness curve. The surface roughness Rz of the object to be measured is measured by calculating the sum of the maximum peak height (i.e., the height from the mean line to the peak) and the maximum valley depth (i.e., the height from the mean line to the valley bottom) observed on the extracted roughness curve.

[0151] The metal layer is preferably a copper layer, and the copper layer is preferably a rolled copper foil formed by a rolling method or an electrolytic copper foil formed by an electrolytic method.

[0152] The average thickness of the metal layer, preferably the copper layer, is not particularly limited, but is preferably 2 μm to 30 μm, more preferably 3 μm to 20 μm, and even more preferably 5 μm to 18 μm. The copper foil may be a carrier-attached copper foil formed releasably on a support (carrier). Any known carrier can be used. The average thickness of the carrier is not particularly limited, but is preferably 10 μm to 100 μm, and more preferably 18 μm to 50 μm.

[0153] Furthermore, from the viewpoint of further demonstrating the effects of the present disclosure, the metal layer preferably has a known surface treatment layer (e.g., a chemical treatment layer) on the surface that contacts the film to ensure adhesion with the resin. Furthermore, the interactable group is preferably a group corresponding to the functional group of the compound having a functional group contained in the film, such as an amino group and an epoxy group, or a hydroxy group and an epoxy group. Examples of the interactable group include the groups listed as functional groups in the compound having the functional group. Among these, from the viewpoints of adhesion and ease of processing, a group capable of covalent bonding is preferred, an amino group or a hydroxy group is more preferred, and an amino group is particularly preferred.

[0154] The metal layer in the laminate according to the present disclosure may be a metal layer having a circuit pattern. It is also preferable to process the metal layer in the laminate according to the present disclosure into a desired circuit pattern by, for example, etching, to form a flexible printed circuit board. The etching method is not particularly limited, and known etching methods can be used.

[0155] 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. In the examples, "%" and "parts" mean "% by mass" and "parts by mass," respectively, unless otherwise specified.

[0156] <Polymer or polymer particles> P1: Aromatic polyesteramide (liquid crystal polymer) prepared according to the following production method. P2: Product name "Tuftec M1913", manufactured by Asahi Kasei Chemicals Corporation, hydrogenated styrene-ethylene-butylene-styrene block copolymer. PP-1: Liquid crystal polymer particles prepared according to the following production method. PP-2: Product name "Tuftec M1913", manufactured by Asahi Kasei Chemicals Corporation, frozen and pulverized product of hydrogenated styrene-ethylene-butylene-styrene block copolymer (average particle size 5.0 μm (D50)).

[0157] -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 a powdered aromatic polyesteramide A1a. The flow initiation temperature of the aromatic polyesteramide A1a was 193°C. The aromatic polyesteramide A1a was a wholly aromatic polyesteramide. The aromatic polyesteramide A1a 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 effect solid-state polymerization, followed by cooling. The mixture was then pulverized in a grinder to obtain a powdered aromatic polyesteramide A1b. The flow initiation temperature of the aromatic polyesteramide A1b was 220°C. The aromatic polyesteramide A1b 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 effect 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. Furthermore, the melting point of the aromatic polyesteramide P1 was measured using a differential scanning calorimeter and found to be 311° C. The solubility of the aromatic polyesteramide P1 in N-methylpyrrolidone at 140° C. was 1% by mass or more.

[0158] - Preparation of Liquid Crystal Polymer Particles PP-1 - A reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer, and reflux condenser was charged with 1,034.99 g (5.5 mol) of 2-hydroxy-6-naphthoic acid, 89.18 g (0.41 mol) of 2,6-naphthalenedicarboxylic acid, 236.06 g (1.42 mol) of terephthalic acid, 341.39 g (1.83 mol) of 4,4-dihydroxybiphenyl, and potassium acetate and magnesium acetate as catalysts. After the gas inside the reactor was replaced with nitrogen gas, acetic anhydride (1.08 molar equivalents relative to the hydroxyl groups) was further added. Under a nitrogen gas stream, the temperature was raised from room temperature to 150°C over 15 minutes with stirring, and refluxed at 150°C for 2 hours. Next, the temperature was raised from 150°C to 310°C over 5 hours while distilling off the by-product acetic acid and unreacted acetic anhydride. The polymer was removed and cooled to room temperature. The obtained polymer was heated from room temperature to 295°C over 14 hours and solid-state polymerized at 295°C for 1 hour. After solid-state polymerization, the polymer was cooled to room temperature over 5 hours to obtain liquid crystal polymer particles PP-1. The liquid crystal polymer particles PP-1 had a median diameter (D50) of 7 μm, a dielectric dissipation factor of 0.0007, and a melting point of 334°C.

[0159] Example 1 Preparation of Layer C-Forming Composition 8 parts of aromatic polyesteramide P1 was added to 92 parts of N-methylpyrrolidone and stirred at 140°C for 4 hours under a nitrogen atmosphere to obtain an aromatic polyesteramide solution (solid content concentration: 8% by mass). 10.0 parts by mass of the aromatic polyesteramide solution was mixed with 0.04 parts of an aminophenol-type epoxy resin ("jER630" manufactured by Mitsubishi Chemical Corporation) to prepare a layer C-forming composition.

[0160] - Preparation of Layer A Forming Composition - Polymer P1 and polymer PP-1 were mixed in a mass ratio of 30:70, and N-methylpyrrolidone was added to adjust the solids concentration to 22 mass %, thereby obtaining Layer A Forming Composition A1.

[0161] - Preparation of Layer B Forming Composition - N-methylpyrrolidone was added to PP-2 to adjust the solid content concentration to 20 mass %, thereby obtaining Layer B forming composition B1.

[0162] - Preparation of single-sided copper-clad laminate - The obtained Layer C-forming composition, Layer A-forming composition A1, and Layer B-forming composition B1 were fed into a slot die coater equipped with a slide coater and applied to the treated surface of copper foil (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T4X-SV-18, thickness 18 μm, surface roughness of the attachment surface (treated surface) Rz 0.85 μm) in a three-layer configuration (Layer C / Layer A / Layer B) with the flow rate adjusted to give the film thicknesses listed in Table 1. At this time, Layer C was positioned on the copper foil side. The flow rate of each composition was adjusted so that the thickness of Layer C was 4 μm, and the thicknesses of Layer A and Layer B were the values ​​listed in Table 1. The coating was dried at 40°C for 4 hours with dry air containing 8% by volume of N-methylpyrrolidone vapor to remove the solvent from the coating and form a mixed layer. The coating was then heated from room temperature to 300°C at a rate of 1°C / min in a nitrogen atmosphere and held at that temperature for 2 hours, resulting in a heat treatment to obtain a film having a copper layer (single-sided copper-clad laminate).

[0163] Example 2 The same procedure as in Example 1 was carried out, except that the drying temperature was changed from 40°C to 70°C.

[0164] Example 3 A film having a copper layer (single-sided copper-clad laminate) was obtained in the same manner as in Example 1, except that the production process of the single-sided copper-clad laminate in Example 1 was changed to the process shown below.

[0165] - Preparation of single-sided copper-clad laminate - The obtained Layer C-forming composition, Layer A-forming composition A1, and Layer B-forming composition B1 were fed to a slot die coater equipped with a feed block, and interlayer mixing was promoted during the feeding. Then, the compositions were applied to the treated surface of copper foil (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T4X-SV-18, thickness 18 μm, surface roughness of the attachment surface (treated surface) Rz 0.85 μm) in a three-layer configuration (Layer C / Layer A / Layer B) with the flow rate adjusted to a film thickness shown in Table 1. At this time, Layer C was positioned on the copper foil side. The flow rate of each composition was adjusted so that Layer C had a thickness of 4 μm, and Layers A and B had thicknesses shown in Table 1. The coating was dried at 40°C for 4 hours to remove the solvent from the coating and form a mixed layer. The coating was then heated from room temperature to 300°C at a rate of 1°C / min in a nitrogen atmosphere and held at that temperature for 2 hours, resulting in a heat treatment to obtain a film with a copper layer (single-sided copper-clad laminate).

[0166] Comparative Example 1 A film having a copper layer (single-sided copper-clad laminate) was obtained in the same manner as in Example 1, except that the production process of the single-sided copper-clad laminate in Example 1 was changed to the process shown below.

[0167] - Preparation of single-sided copper-clad laminate - The obtained Layer C-forming composition was applied to the treated surface of a copper foil (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T4X-SV-18, thickness 18 μm, surface roughness of the attachment surface (treated surface) Rz 0.85 μm) and dried at 150°C for 1 hour. Next, the obtained Layer A-forming composition A1 was applied and dried at 40°C for 4 hours. Subsequently, the obtained Layer B-forming composition B1 was applied and dried at 40°C for 4 hours. The obtained three-layer (Layer C / Layer A / Layer B) laminate was further heated from room temperature to 300°C at a rate of 1°C / min in a nitrogen atmosphere and maintained at that temperature for 2 hours, thereby obtaining a film having a copper layer (single-sided copper-clad laminate).

[0168] Comparative Example 2 A film having a copper layer (single-sided copper-clad laminate) was obtained in the same manner as in Example 1, except that the production process of the single-sided copper-clad laminate in Example 1 was changed to the process shown below.

[0169] - Preparation of Layer A Forming Composition - Polymer P1 and polymer PP-1 were mixed in a mass ratio of 30:70, and N-methylpyrrolidone was added to adjust the solids concentration to 25 mass %, thereby obtaining Layer A Forming Composition A2.

[0170] —Preparation of Layer B Forming Composition— N-methylpyrrolidone was added to the polymer P2, and the solid content was adjusted to 20% by mass, to obtain a layer B forming composition B2.

[0171] - Preparation of single-sided copper-clad laminate - The obtained Layer C-forming composition, Layer A-forming composition A2, and Layer B-forming composition B2 were fed into a slot die coater equipped with a slide coater and applied to the treated surface of a copper foil (manufactured by Fukuda Metal Foil & Powder Co., Ltd., CF-T4X-SV-18, thickness 18 μm, surface roughness of the attachment surface (treated surface) Rz 0.85 μm) in a two-layer configuration (Layer A / Layer B) with the flow rate adjusted to a film thickness shown in Table 1. At this time, Layer A was positioned on the copper foil side. The coating was dried at 40°C for 4 hours to remove the solvent from the coating, and further heat-treated by increasing the temperature from room temperature to 300°C at a rate of 1°C / min in a nitrogen atmosphere and maintaining that temperature for 2 hours, to obtain a film having a copper layer (single-sided copper-clad laminate).

[0172] The dielectric loss tangent, the modulus of elasticity at 160°C of Layer A and Layer B, and the weight residual ratio L of Layer A and Layer B were measured. Ａ , L Ｂ The measurement results and evaluation results are shown in Table 1.

[0173] In Table 1, "40% position" means a position at 40% of the film thickness, measured from the surface on the Layer B side toward the thickness direction. The composition at this 40% position is expressed as the mass ratio of Composition A to Composition B. "60% position" means a position at 60% of the film thickness, measured from the surface on the Layer B side toward the thickness direction. The composition at this 60% position is expressed as the mass ratio of Composition A to Composition B. In Comparative Examples 1 and 2, a mixed layer was not present, and therefore "-" was entered in the mixed layer column.

[0174] [Dielectric loss tangent] The dielectric loss tangent was 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.) was connected to a network analyzer (E8363B manufactured by Agilent Technology Corporation), and the test piece was inserted into the cavity resonator. The dielectric loss tangent of the film was measured from the change in resonance frequency before and after insertion for 96 hours under an environment of 25°C and 60% RH.

[0175] [Elastic Modulus at 160°C] First, a cross section of the film was cut using a microtome or the like, and Layer A or Layer B was identified using an optical microscope. Next, the elastic modulus of the identified Layer A or Layer B was measured as the indentation elastic modulus using a nanoindentation method. The indentation elastic modulus was measured using a microhardness tester (product name "DUH-W201", manufactured by Shimadzu Corporation) at 160°C by applying a load with a Vickers indenter at a loading rate of 0.28 mN / sec, holding a maximum load of 10 mN for 10 seconds, and then unloading at a loading rate of 0.28 mN / sec.

[0176] [Weight Residual Rate] Layer A or Layer B was cut from the film, and 5 mg of the layer was placed on a platinum pan. The weight residual rate was measured using a differential thermobalance (TG-DTA) (TG-8120, manufactured by Rigaku Corporation) at a heating rate of 10°C / min and a measurement temperature of 25°C to 900°C. Ａ or L Ｂ ) was set to the following value: Weight residual rate (%, L Ａ or L Ｂ ) = Weight remaining rate (%) at 440°C - Weight remaining rate (%) at 900°C

[0177] [Laser processing suitability] (1) Sample preparation A copper foil (product name "CF-T9DA-SV-18", average thickness 18 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) was placed on the layer B side of the prepared single-sided copper-clad laminate so that the treated surface was in contact with the layer B side. Using a laminator (product name "Vacuum Laminator V-130", manufactured by Nikko Materials Co., Ltd.), lamination was performed for 60 minutes under conditions of 160°C and a lamination pressure of 4 MPa, to obtain a double-sided copper-clad laminate.

[0178] (2) Measurement Method Using a UV-YAG laser Model 5330 manufactured by ESI, through-hole vias were drilled from the single-sided copper-clad laminate side of the double-sided copper-clad laminate. The cross section of the via was observed with an optical microscope, and the length of the scraping in Layer A and Layer B (i.e., the maximum horizontal length of the depression formed on the horizontal cut surface of the cut portion) was measured. In Table 1, the unit is "μm." The shorter the length of the scraping in Layer A and Layer B, the more suitable it is for laser processing.

[0179] [Step Conformability (Wiring Conformability)] (1) Sample Preparation - Preparation of Substrate with Wiring Pattern - Copper foil (product name "CF-T9DA-SV-18", average thickness 18 μm, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) and a liquid crystal polymer film (product name "CTQ-50", average thickness 50 μm, manufactured by Kuraray Co., Ltd.) were prepared as a substrate. The copper foil, substrate, and copper foil were stacked in this order so that the treated surface of the copper foil was in contact with the substrate. Using a laminator (product name "Vacuum Laminator V-130", manufactured by Nikko Materials Co., Ltd.), a lamination process was performed for 1 minute under conditions of 140 ° C. and a lamination pressure of 0.4 MPa, to obtain a precursor of a double-sided copper-clad laminate. Next, using a thermocompression bonding machine (product name "MP-SNL", manufactured by Toyo Seiki Seisakusho, Ltd.), the obtained precursor of the double-sided copper-clad laminate was thermocompressed at 300°C and 4.5 MPa for 10 minutes to produce a double-sided copper-clad laminate. The copper foil on both sides of the double-sided copper-clad laminate was etched and patterned to produce a substrate with a wiring pattern including a ground line and three pairs of signal lines on both sides of the substrate. The length of the signal line was 50 mm, and the width was set so that the characteristic impedance was 50 Ω.

[0180] - Preparation of wiring board - The substrate with wiring pattern prepared above was placed on the layer B side of the prepared single-sided copper-clad laminate, and hot pressed at 160°C and 4 MPa for 1 hour to obtain a wiring board. The obtained wiring board had a wiring pattern (ground line and signal line) embedded therein, and the thickness of the wiring pattern was 18 μm.

[0181] (2) Measurement method The wiring board was cut in the thickness direction with a microtome, and the cross section was observed with an optical microscope. The length L of the gap occurring in the in-plane direction between the resin layer and the wiring pattern was measured. The average value for 10 locations was calculated. The evaluation criteria were as follows: A: L is less than 2 μm. B: L is 2 μm or more.

[0182]

[0183] As shown in Table 1, Examples 1 to 3 have two imaginary surfaces perpendicular to the thickness direction, namely, surface A made of composition A and surface B made of composition B, and the content of at least one component A contained in composition A decreases from surface A to surface B, and the content of at least one component B contained in composition B decreases from surface B to surface A, and the dielectric loss tangent is 0.010 or less, indicating excellent suitability for laser processing. On the other hand, in Comparative Examples 1 and 2, the compositions of Layer A and Layer B are constant, and the content of at least one component A contained in composition A does not decrease from surface A to surface B, and the content of at least one component B contained in composition B does not decrease from surface B to surface A, indicating poor suitability for laser processing.

[0184] The disclosure of Japanese Patent Application No. 2022-089034, filed on May 31, 2022, 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. The film has two imaginary surfaces perpendicular to the thickness direction, that is, surface A made of composition A and surface B made of composition B, the content of at least one component A contained in the composition A decreases from the side A to the side B, the content of at least one component B contained in the composition B decreases from the side B toward the side A, a value L A obtained by subtracting the weight residual rate of the layer A at 900° C. from the weight residual rate of the layer A at 440° C. is greater than a value L B obtained by subtracting the weight residual rate of the layer B at 900° C. from the weight residual rate of the layer B at 440° C.; A film having a dielectric loss tangent of 0.010 or less.

2. A layer A made of the composition A and including the A surface; A layer B made of the composition B and including the surface B; a mixed layer located between the layer A and the layer B and containing components contained in the composition A and the composition B; The film of claim 1 , comprising in the thickness direction

3. The film of claim 2 , wherein the average thickness of the mixed layer is 1.0% or more relative to the thickness of the film.

4. The film according to claim 2 , wherein at least one of the layer A and the layer B has an average thickness of 0.1 μm or more.

5. 3. The film according to claim 2, wherein the ratio of the modulus of elasticity of said layer A at 160°C to the modulus of elasticity of said layer B at 160°C is 1.2 or greater.

6. The film according to claim 2 , wherein the layer B has an elastic modulus of 100 MPa or less at 160° C.

7. The film according to claim 2 , wherein the layer B comprises a thermoplastic resin containing structural units derived from a monomer having an aromatic hydrocarbon group.

8. The film of claim 2 , wherein the Layer B comprises a liquid crystal polymer.

9. The film of claim 2 , wherein the Layer B comprises an aromatic polyesteramide.

10. The film of claim 2 wherein said Layer B comprises crosslinked resin particles.

11. The film of claim 2 , wherein the layer A comprises a liquid crystal polymer.

12. The film of claim 2 wherein the Layer A comprises an aromatic polyesteramide.

13. A laminate comprising the film according to any one of claims 1 to 12 and a metal layer or metal wiring disposed on at least one surface of the film.

14. The film has two imaginary surfaces perpendicular to the thickness direction, that is, surface A made of composition A and surface B made of composition B, the content of at least one component A contained in the composition A decreases from the side A to the side B, the content of at least one component B contained in the composition B decreases from the side B toward the side A, A layer A made of the composition A and including the A surface; A layer B made of the composition B and including the surface B; a mixed layer located between the layer A and the layer B and containing components contained in the composition A and the composition B; In the thickness direction, a ratio of the elastic modulus of the layer A at 160°C to the elastic modulus of the layer B at 160°C is 1.2 or more; A film having a dielectric loss tangent of 0.010 or less.