Polymer film and laminate

Abstract

A polymer film and a use therefor, said polymer film comprising a layer A and a layer B disposed on at least one surface of the layer A, wherein: the layer A has a surface roughness Rc of at most of 5 μm on the side having the layer B disposed thereon; the layer B comprises a material a having an elastic modulus at 260°C of less than 0.10 MPa and a material b having an elastic modulus at 260°C of at least 0.10 MPa, and has an elastic modulus at 25°C of at most 500 MPa and an elastic modulus at 160°C of at most 0.60 MPa; and the dissipation factor is at most 0.01.

Description

Polymer Films and Laminates

[0001] The present disclosure relates to polymer 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 has become necessary to lower the relative permittivity and dielectric loss tangent of insulating materials used in circuit boards. Copper-clad laminates are preferably used as components constituting circuit boards, and films are preferably used to manufacture copper-clad laminates.

[0003] For example, Japanese Patent Application Laid-Open No. 2022-184736 describes a wiring board in which wiring patterns are embedded and the regions located between the wiring patterns arranged in the in-plane direction on the same plane have an elastic modulus of 0.1 MPa or less at 140°C and a dielectric loss tangent of 0.006 or less.

[0004] Typically, copper-clad laminates are manufactured by laminating copper foil on the surface of a polymer film. Furthermore, wiring boards are manufactured by overlapping a copper-clad laminate and a wiring substrate so that the polymer film in the copper-clad laminate contacts the wiring substrate. When manufacturing a wiring board, from the viewpoint of adhesion, it is required that the polymer film conforms to and deforms to the steps formed on the surface of the wiring substrate. On the other hand, when a polymer film with excellent step conformability to the wiring substrate is used in a copper-clad laminate, delamination may occur during the reflow soldering process performed when mounting electronic components. Therefore, there has been a demand for both step conformability to the wiring substrate and excellent adhesion (i.e., excellent heat resistance) during reflow soldering.

[0005] An object of one embodiment of the present disclosure is to provide a polymer film and a laminate that are excellent in step conformability and heat resistance.

[0006] Means for solving the above problems include the following aspects: <1> A polymer film comprising a layer A and a layer B disposed on at least one surface of layer A, wherein layer A has a surface roughness Rc of 5 μm or less on the side where layer B is disposed, and layer B comprises a material a having an elastic modulus of less than 0.10 MPa at 260°C and a material b having an elastic modulus of 0.10 MPa or more at 260°C, wherein the elastic modulus at 25°C is 500 MPa or less and the elastic modulus at 160°C is 0.60 MPa or less, and the dielectric loss tangent is 0.01 or less. <2> The polymer film according to <1>, wherein material a is an elastomer containing a structural unit derived from styrene. <3> The polymer film according to <1> or <2>, wherein material a is at least one selected from the group consisting of a styrene-ethylene-butylene-styrene block copolymer, a styrene-isobutylene-styrene block copolymer, a styrene-ethylene-propylene-styrene copolymer, a styrene-isoprene-styrene block copolymer, and hydrogenated products thereof. <4> The polymer film according to any one of <1> to <3>, wherein material b is at least one selected from the group consisting of a liquid crystal polymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, and a fluororesin. <5> The polymer film according to any one of <1> to <4>, wherein Layer A contains particles having a melting point of 300°C or higher. <6> The polymer film according to <5>, wherein the average particle size of the particles is 4.0 μm or less. <7> The polymer film according to any one of <1> to <6>, wherein Layer A has an elastic modulus of more than 0.60 MPa at 160°C. <8> A laminate comprising the polymer film according to any one of <1> to <7> and a metal layer or metal wiring arranged on at least one surface of the polymer film. <9> The laminate according to <8>, comprising Layer B, Layer A, and a metal layer in this order. <10> The laminate according to <8>, further comprising a second metal layer, comprising the second metal layer, Layer A, Layer B, and a metal layer or metal wiring in this order.

[0007] According to one embodiment of the present disclosure, a polymer film and a laminate having excellent step conformability and heat resistance are provided.

[0008] The contents of the present disclosure are described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment. In this specification, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the upper and lower limits. In the numerical ranges described in stages in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, in the description of groups (atomic groups) in this specification, a notation that does not specify whether they are substituted or unsubstituted encompasses both unsubstituted and substituted groups. For example, the term "alkyl group" encompasses not only alkyl groups without substituents (unsubstituted alkyl groups) but also alkyl groups with substituents (substituted alkyl groups). In this specification, "(meth)acrylic" is a term used to conceptually encompass both acrylic and methacrylic, and "(meth)acryloyl" is a term used to conceptually encompass both acryloyl and methacryloyl. Furthermore, the term "process" in this specification includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, in this disclosure, a combination of two or more preferred aspects is a more preferred aspect. Furthermore, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in this disclosure are molecular weights measured using a gel permeation chromatography (GPC) analyzer equipped with a column of TSKgel Super HM-H (a trade name manufactured by Tosoh Corporation) using a solvent of PFP (pentafluorophenol) / chloroform = 1 / 2 (mass ratio), detected with a differential refractometer, and converted using polystyrene as a standard substance. The average particle size (e.g., D50) of particles in the present disclosure is measured using a laser diffraction / scattering particle size distribution analyzer, such as the LA-950V2 manufactured by HORIBA.

[0009] [Polymer Film] A polymer film according to the present disclosure includes a layer A and a layer B disposed on at least one surface of layer A, wherein layer A has a surface roughness Rc of 5 μm or less on the side where layer B is disposed, and layer B includes a material a having an elastic modulus of less than 0.10 MPa at 260° C. and a material b having an elastic modulus of 0.10 MPa or more at 260° C., and has an elastic modulus of 500 MPa or less at 25° C. and an elastic modulus of 0.60 MPa or less at 160° C., and a dielectric loss tangent of 0.01 or less.

[0010] As a result of extensive investigations, the present inventors have found that the above-described structure can provide a polymer film having excellent step-conforming ability and heat resistance. Although the detailed mechanism by which the above-described effects are obtained is unknown, it is speculated as follows.

[0011] When manufacturing a multilayer copper-clad laminate, copper foil and a polymer film are laminated together and then thermocompression bonded. During this process, heating causes some of the materials contained in the polymer film to become more fluid. If a pressure distribution occurs during thermocompression bonding, some of the more fluid materials move from high-pressure areas to low-pressure areas, resulting in a layer of separated fluid materials (a fluidized layer). In the reflow soldering process performed when mounting electronic components, the laminate is pretreated and heated at a high temperature (e.g., 260°C). During this process, the moisture becomes supersaturated and diffuses, resulting in the generation of bubble nuclei. Conventionally, bubble nuclei grow in the fluidized layer, causing foaming and resulting in delamination between the polymer film and the metal layer. In contrast, Layer B in the polymer film according to the present disclosure has an elastic modulus of 0.60 MPa or less at 160°C, resulting in excellent conformability to uneven surfaces. Furthermore, since the surface roughness Rc of Layer A on the side where Layer B is disposed in the polymer film according to the present disclosure is 5 μm or less, pressure distribution is unlikely to occur during thermocompression bonding, and migration of materials contained in the polymer film is suppressed. It is believed that this suppresses the growth of bubble nuclei during the reflow soldering process, thereby suppressing peeling between the polymer film and the metal layer. In other words, the polymer film has excellent heat resistance.

[0012] Patent Document 1, JP 2022-184736 A, does not mention that the surface roughness Rc of Layer A on the side where Layer B is disposed is 5 μm or less. In addition, the polymer film described in Patent Document 1, JP 2022-184736 A, has an elastic modulus at 25 ° C. of more than 500 MPa.

[0013] The polymer film according to the present disclosure will be described in detail below. The polymer film according to the present disclosure includes a layer A and a layer B disposed on at least one surface of the layer A. The layer A and the layer B may be in direct contact with each other, or another layer may be provided between the layer A and the layer B. From the viewpoint of step conformability and heat resistance, the layer A and the layer B are preferably in direct contact with each other.

[0014] <<Layer B>> Layer B includes a material a having an elastic modulus at 260°C of less than 0.10 MPa and a material b having an elastic modulus at 260°C of 0.10 MPa or more.

[0015] <Material a> Layer B contains material a having an elastic modulus of less than 0.10 MPa at 260° C. Material a may be a low molecular weight compound or a high molecular weight compound as long as it has an elastic modulus of less than 0.10 MPa at 260° C. Material a may be of only one type, or of two or more types.

[0016] From the viewpoint of the ability to conform to uneven surfaces, the elastic modulus of material a at 260°C is preferably 0.05 MPa or less. The lower limit of the elastic modulus of material a at 260°C is not particularly limited and may be, for example, 0.1 kPa. When the elastic modulus of material a at 260°C is less than 0.10 MPa, the ability to conform to uneven surfaces is excellent.

[0017] In the present disclosure, the modulus of elasticity of material a at 260°C is measured by the following method. A film cross-section sample is prepared by obliquely cutting with a microtome so that the cross-section thickness is 50 μm. Next, the 260°C modulus of elasticity of the portion of material a is measured as the indentation modulus using a nanoindentation method. The indentation modulus is measured using a microhardness tester (for example, product name "DUH-W201" manufactured by Shimadzu Corporation) 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.

[0018] Among these, from the viewpoint of conformability to unevenness, material a is preferably a thermoplastic resin, a thermoplastic elastomer, an uncured or semi-cured product of a thermosetting resin, or an uncured or semi-cured product of a thermosetting elastomer.

[0019] 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 modified polycarbonate resins, and fluorene ring-modified polyester resins.

[0020] Examples of thermoplastic elastomers include elastomers containing structural units derived from styrene (polystyrene-based elastomers), polyester-based elastomers, polyolefin-based elastomers, polyurethane-based elastomers, polyamide-based elastomers, polyacrylic-based elastomers, silicone-based elastomers, polyimide-based elastomers, etc. The thermoplastic elastomer may be a hydrogenated product.

[0021] Examples of polystyrene elastomers include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), polystyrene-poly(ethylene-propylene) diblock copolymers (SEP), polystyrene-poly(ethylene-propylene)-polystyrene triblock copolymers (SEPS), styrene-ethylene-butylene-styrene block copolymers (SEBS), and polystyrene-poly(ethylene / ethylene-propylene)-polystyrene triblock copolymers (SEEPS), styrene-isobutylene-styrene block copolymers (SIBS), and hydrogenated products thereof.

[0022] Among these, from the viewpoints of dielectric loss tangent and step-conforming ability, material a is preferably a thermoplastic elastomer, more preferably an elastomer containing a structural unit derived from styrene, and even more preferably at least one selected from the group consisting of a styrene-ethylene-butylene-styrene block copolymer, a styrene-isobutylene-styrene block copolymer, a styrene-ethylene-propylene-styrene copolymer, a styrene-isoprene-styrene block copolymer, and hydrogenated products thereof.

[0023] From the viewpoint of achieving both step-conforming ability and processability, the content of material a is preferably 40% by mass to 95% by mass, and more preferably 60% by mass to 90% by mass, relative to the total mass of layer B.

[0024] The weight-average molecular weight of material a is preferably 1,000 or more, more preferably 10,000 or more, and even more preferably 30,000 or more. The upper limit of the weight-average molecular weight is, for example, 1,000,000.

[0025] The material A is preferably used as a powder in the production of the polymer film. The method for converting the material A into a powder more preferably includes a swelling step of swelling the material A with a liquid medium and a pulverization step of pulverizing the swollen material A.

[0026] <Material b> Layer B contains material b having an elastic modulus of 0.10 MPa or more at 260° C. Material b may be a low molecular weight compound or a high molecular weight compound as long as it has an elastic modulus of 0.10 MPa or more at 260° C. Material b may be of only one type, or of two or more types.

[0027] From the viewpoint of step conformability, the elastic modulus of material b at 260° C. is preferably 1.0 MPa or more. The upper limit of the elastic modulus of material b at 260° C. is not particularly limited and is, for example, 1000 MPa. When the elastic modulus of material b at 260° C. is 0.10 MPa or more, the heat resistance is excellent.

[0028] In the present disclosure, the elastic modulus of material b at 260°C is measured by the following method. A film cross-section sample is prepared by obliquely cutting with a microtome so that the cross-section thickness is 50 μm. Next, the 260°C elastic modulus of the portion of material b is measured as the indentation elastic modulus using a nanoindentation method. The indentation elastic modulus is measured using a microhardness tester (for example, product name "DUH-W201" manufactured by Shimadzu Corporation) 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.

[0029] Examples of material b include thermosetting resins such as liquid crystal polymers, fluororesins, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, polyphenylene ether and modified products thereof, aromatic polyether ketone, phenolic resins, epoxy resins, polyimides, cyanate resins, bismaleimide resins, and triazine resins.

[0030] - Liquid Crystal Polymer - From the viewpoint of dielectric loss tangent, it is preferable that material b contains a liquid crystal polymer.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The liquid crystal polymer is preferably a wholly aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0036] 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.

[0037] The melting point of the liquid crystal polymer is preferably higher than 260°C, more preferably higher than 260°C and not higher than 350°C, and even more preferably higher than 260°C and not higher than 330°C.

[0038] In the present disclosure, the melting point is measured using a differential scanning calorimeter. For example, it is measured using a product called "DSC-60A Plus" (manufactured by Shimadzu Corporation). The temperature rise rate in the measurement is 10°C / min.

[0039] 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.

[0040] From the viewpoint of further reducing the dielectric loss tangent, the liquid crystal polymer preferably contains an aromatic polyesteramide. The aromatic polyesteramide is a resin having at least one aromatic ring and having an ester bond and an amide bond. In particular, from the viewpoint of heat resistance, the aromatic polyesteramide is preferably a wholly aromatic polyesteramide.

[0041] The aromatic polyesteramide is preferably a crystalline polymer. Material B preferably contains a crystalline aromatic polyesteramide. The crystalline aromatic polyesteramide further reduces the dielectric loss tangent. A crystalline polymer refers to a polymer that has a clear endothermic peak rather than a stepwise change in endothermic amount in differential scanning calorimetry (DSC). Specifically, for example, this means that the half-width of the endothermic peak is within 10°C when measured at a heating rate of 10°C / min. Polymers with a half-width exceeding 10°C and polymers in which no clear endothermic peak is observed are considered amorphous polymers and are distinguished from crystalline polymers.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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 constituent unit derived from 4'-hydroxy-4-biphenylcarboxylic acid.

[0048] 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.

[0049] 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.

[0050] In formula 3, Ar ３ is preferably a p-phenylene group or a 4,4'-biphenylylene group, and more preferably a p-phenylene group.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] The aromatic polyesteramide is preferably produced by melt-polymerizing raw material monomers corresponding to the structural units that constitute the aromatic polyesteramide.

[0056] The weight average molecular weight of the aromatic polyesteramide is preferably 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000.

[0057] -Fluororesin--Material b may be a fluororesin from the viewpoint of heat resistance and mechanical strength.

[0058] In the present disclosure, the type of fluororesin is not particularly limited, and known fluororesins can be used.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] - Polymer of a Compound Having a Cyclic Aliphatic Hydrocarbon Group and a Group Having an Ethylenically Unsaturated Bond - Material b may be a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond.

[0068] Examples of polymers of compounds having a cyclic aliphatic 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.

[0069] The polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be a ring-opening polymer of the above-mentioned cyclic olefin or a hydrogenated product of a ring-opening copolymer using two or more kinds of cyclic olefins, or may be an addition polymer of a cyclic olefin and an aromatic compound having an ethylenically unsaturated bond such as a chain olefin or a vinyl group. In addition, a polar group may be introduced into the polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond.

[0070] The polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond may be used alone or in combination of two or more kinds.

[0071] 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 isophorone 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.

[0072] -Polyphenylene Ether- Material b may be 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.

[0073] 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).

[0074]

[0075] 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.

[0076] When the polyphenylene ether is thermally cured after film formation, the weight average molecular weight (Mw) is preferably 500 to 5,000, and more preferably 500 to 3,000, from the viewpoints of heat resistance and film formability. When the polyphenylene ether is not thermally cured, the weight average molecular weight (Mw) is not particularly limited, but is preferably 3,000 to 100,000, and more preferably 5,000 to 50,000.

[0077] - Aromatic Polyether Ketone - Material b may be aromatic polyether ketone.

[0078] The aromatic polyether ketone is not particularly limited, and any known aromatic polyether ketone can be used.

[0079] The aromatic polyether ketone is preferably polyether ether ketone.

[0080] 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. Each bond is preferably connected by a divalent aromatic group. The aromatic polyether ketone may be used alone or in combination of two or more types.

[0081] 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).

[0082]

[0083] 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.

[0084] Among these, from the viewpoint of the dielectric loss tangent, material b is preferably at least one selected from the group consisting of a liquid crystal polymer, a polymer of a compound having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, and a fluororesin, and is more preferably an aromatic polyesteramide.

[0085] Furthermore, material b may be in a particulate form. When material b is in a particulate form, material b may be organic particles or inorganic particles. Note that when layer B contains particulate material b, it is preferable that layer B also contains material b that is not particulate.

[0086] Examples of resins constituting the organic particles include polyethylene, polystyrene, urea-formalin filler, polyester, cellulose, acrylic resin, fluororesin, cured epoxy resin, crosslinked benzoguanamine resin, crosslinked acrylic resin, and liquid crystal polymer. The resins constituting the organic particles may be one type or two or more types.

[0087] The organic particles may be fibrous, such as nanofibers, or hollow resin particles.

[0088] Among them, from the viewpoint of dielectric loss tangent and step-conforming ability, the organic particles are 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, a liquid crystal polymer polymer polymerized and pulverized with a pulverizer or the like to obtain a powdered liquid crystal. The preferred embodiments of the liquid crystal polymer constituting the liquid crystal polymer particles are the same as the preferred embodiments of the liquid crystal polymer described above.

[0089] The average particle size of the organic particles is preferably 5 nm to 20 μm, more preferably 100 nm to 10 μm, from the viewpoint of dielectric loss tangent and step-conforming ability.

[0090] Examples of compounds constituting inorganic particles include boron nitride (BN), Al ２ O ３ , AlN, TiO ２ , SiO ２ , barium titanate, strontium titanate, aluminum hydroxide, and calcium carbonate. The compound constituting the inorganic particles may be one type or two or more types.

[0091] Among these, as inorganic particles, from the viewpoint of dielectric loss tangent and step-following ability, metal oxide particles or fibers are preferred, silica particles, titania particles, or glass fibers are more preferred, and silica particles or glass fibers are particularly preferred.

[0092] From the viewpoint of dielectric loss tangent and step-conforming ability, the average particle size of the inorganic particles 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.

[0093] From the viewpoint of heat resistance, the content of material b is preferably 5% by mass to 60% by mass, and more preferably 10% by mass to 40% by mass, based on the total mass of layer B.

[0094] Layer B may contain other additives in addition to materials a and b. Known additives can be used as the other additives. Examples of the other additives include a curing agent, a leveling agent, an antifoaming agent, an antioxidant, an ultraviolet absorber, a flame retardant, and a colorant.

[0095] Layer B may also contain a foaming agent that disappears or decomposes upon heating to release a gas. The foaming agent may be an organic foaming agent or an inorganic foaming agent.

[0096] Examples of organic foaming agents include particles containing an acrylic resin as a main component, particles containing an ethyl cellulose resin as a main component, particles containing a butyral resin as a main component, nitrosamine compounds such as dinitrosopentamethylenetetramine (DPT), azo compounds such as azodicarbonamide (ADCA), and hydrazine compounds such as 4,4'-oxybisbenzenesulfonylhydrazide (OBSH) and hydrazodicarbonamide (HDCA).

[0097] Examples of inorganic foaming agents include bicarbonates such as sodium bicarbonate; carbonates; and combinations of bicarbonates and organic acid salts such as sodium citrate.

[0098] <Physical Properties> The elastic modulus of Layer B at 25° C. is 500 MPa or less, and preferably 300 MPa or less. When the elastic modulus of Layer B at 25° C. is 500 MPa or less, the peel strength to the metal layer or metal wiring is improved. The lower limit of the elastic modulus of Layer B at 25° C. is not particularly limited, but may be 10 MPa from the viewpoint of handleability.

[0099] The elastic modulus of Layer B at 160° C. is 0.60 MPa or less, and preferably 0.50 MPa or less. When the elastic modulus of Layer B at 160° C. is 0.60 MPa or less, the layer has excellent conformability to unevenness. The lower limit of the elastic modulus of Layer B at 160° C. is not particularly limited, but may be 0.1 kPa from the viewpoint of processability.

[0100] In the present disclosure, the modulus of elasticity of Layer B at 25°C and 160°C is measured by the following method. A cross-sectional film sample is prepared by obliquely cutting with a microtome so that the cross-sectional thickness is 50 μm. Next, the modulus of elasticity of Layer B is measured as the indentation modulus using a nanoindentation method. The indentation modulus is measured using a microhardness tester (e.g., product name "DUH-W201" manufactured by Shimadzu Corporation) 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. Measurements are made at 20 random positions on the cross-sectional sample at 25°C and 160°C, and the average value is taken as the modulus of elasticity.

[0101] From the viewpoint of conformability to unevenness, the average thickness of Layer B is preferably 5 μm to 50 μm, more preferably 10 μm to 40 μm, and even more preferably 15 μm to 30 μm.

[0102] <<Layer A>> The polymer film according to the present disclosure has Layer A on which Layer B is provided. Layer A preferably contains a polymer having a dielectric loss tangent of 0.01 or less, from the viewpoint of making the dielectric loss tangent of the polymer film 0.01 or less.

[0103] Layer A may contain only one type of polymer having a dielectric loss tangent of 0.01 or less, or may contain two or more types of polymers.

[0104] The dielectric loss tangent of a polymer having a dielectric loss tangent of 0.01 or less is preferably 0.005 or less, more preferably greater than 0 and 0.003 or less, from the viewpoint of the dielectric loss tangent of a polymer film.

[0105] Examples of polymers having a dielectric dissipation factor of 0.01 or less 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 polyether imide; elastomers such as copolymers of glycidyl methacrylate and polyethylene; and thermosetting resins such as phenolic resins, epoxy resins, polyimides, and cyanate resins.

[0106] From the viewpoint of the dielectric loss tangent of the polymer film, the polymer having a dielectric loss tangent of 0.01 or less is preferably a liquid crystal polymer. That is, Layer A preferably contains a liquid crystal polymer. Preferred embodiments of the liquid crystal polymer are the same as the preferred embodiments of the liquid crystal polymer that may be contained in Layer B.

[0107] The layer A may contain a filler in addition to the polymer having a dielectric loss tangent of 0.01 or less.

[0108] The filler may be particulate or fibrous, and may be inorganic or organic particles, specific examples of which are as described above.

[0109] In particular, it is preferable that Layer A contains particles having a melting point of 300° C. or higher.

[0110] When layer A contains particles having a melting point of 300° C. or higher, heat resistance is improved. From the viewpoint of heat resistance, the particles having a melting point of 300° C. or higher preferably have a melting point of 1000° C. or higher. The upper limit of the melting point is, for example, 3000° C.

[0111] Examples of inorganic particles having a melting point of 300° C. or higher include boron nitride (BN) and aluminum oxide (Al ２O ３ ), aluminum nitride (AlN), titanium dioxide (TiO ２ ), silicon dioxide (SiO ２ Examples of organic particles having a melting point of 300° C. or higher include liquid crystal polymer particles and PTFE particles.

[0112] The average particle size of the particles having a melting point of 300° C. or higher is preferably 4.0 μm or less, more preferably 2.0 μm or less, and even more preferably 1.0 μm or less, from the viewpoint of making the surface roughness Rc of the side of Layer A where Layer B is disposed 5 μm or less. The lower limit of the average particle size of the particles having a melting point of 300° C. or higher is not particularly limited, and may be, for example, 0.05 μm.

[0113] The average particle size of particles contained in Layer A and having a melting point of 300°C or higher is measured by the following method. First, the surface of the polymer film is cut with a microtome to prepare a film cross-section sample. The cross-section is observed under a scanning electron microscope (SEM) at 10,000x magnification in 100 fields of view. 100 particles are randomly selected. The lengths of the selected particles in the major axis direction are measured, and the average value is used.

[0114] Layer A may contain only one type of filler, or may contain two or more types of filler. When Layer A contains a filler, the content of the filler is preferably 30% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and particularly preferably 60% by mass to 80% by mass, relative to the total mass of Layer A, from the viewpoints of the dielectric loss tangent, heat resistance, and step-following ability of the laminate.

[0115] Layer A may contain other additives in addition to the above-mentioned components. Preferred embodiments of the other additives that may be contained in Layer A are the same as preferred embodiments of the other additives that may be contained in Layer B.

[0116] Layer A may also contain, as other additives, a resin other than a polymer having a dielectric dissipation factor of 0.01 or less. Examples of the resin other than a polymer having a dielectric dissipation factor of 0.01 or less include thermoplastic resins other than liquid crystal polyester, such as polypropylene, polyamide, polyester other than liquid crystal 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, polyimide resins, and cyanate resins.

[0117] The total content of other additives in Layer A is preferably 25 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the content of the polymer having a dielectric tangent of 0.01 or less.

[0118] <Physical Properties> The elastic modulus of Layer A at 160° C. is preferably greater than 0.60 MPa, and more preferably equal to or greater than 10 MPa. When the elastic modulus of Layer A at 160° C. is greater than 0.60 MPa, Layer A can support Layer B and has excellent conformability to unevenness. The upper limit of the elastic modulus of Layer A at 160° C. is not particularly limited, but may be 1000 MPa from the viewpoint of processability.

[0119] In the present disclosure, the modulus of elasticity of Layer A at 160°C is measured by the following method. A film cross-section sample is prepared by obliquely cutting with a microtome so that the cross-section thickness is 50 μm. Next, the modulus of elasticity of Layer A is measured as the indentation modulus using a nanoindentation method. The indentation modulus is measured using a microhardness tester (e.g., product name "DUH-W201" manufactured by Shimadzu Corporation) 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. Measurements are made at 160°C at 20 random positions on the cross-section sample, and the average value is taken as the modulus of elasticity.

[0120] The surface roughness Rc of Layer A on the side where Layer B is disposed is 5 μm or less, and preferably 3 μm or less. A surface roughness Rc of 5 μm or less provides excellent heat resistance. Furthermore, from the viewpoint of improving the adhesion between Layer A and Layer B, the surface roughness Rc is preferably 0.1 μm or more, and more preferably 1.0 μm or more.

[0121] When layer B is disposed on one surface of layer A, the surface roughness Rc of layer A on the side on which layer B is disposed is required to be 5 μm or less, and the surface roughness Rc of the side opposite to the side on which layer B is disposed is not particularly limited.

[0122] When layer B is disposed on both surfaces of layer A, layer A has a surface roughness Rc of 5 μm or less on both surfaces.

[0123] In the present disclosure, the surface roughness Rc is measured by the following method. A laminate of Layer A and Layer B is obliquely cut with a microtome to expose a cross section. The average height Rc of the interface of Layer A on the Layer B side is measured in accordance with JIS B0601 2001. The evaluation length is 500 μm.

[0124] An example of a method for making the surface roughness Rc of layer A 5 μm or less is to mix particles with small particle diameters into layer A. When preparing the layer A-forming composition used to form layer A, it is preferable to perform a dispersion treatment using a disperser (e.g., bead mill treatment). The bead mill treatment promotes the disintegration and pulverization of particle agglomerates, reducing the particle diameter and enabling the surface roughness Rc to be reduced.

[0125] The average thickness of Layer A is not particularly limited, but from the viewpoints of the dielectric loss tangent, heat resistance, and suppression of wiring distortion of the laminate, it is preferably 5 μm to 90 μm, more preferably 10 μm to 70 μm, and particularly preferably 15 μm to 50 μm.

[0126] From the viewpoint of adhesion to the metal layer, the polymer film according to the present disclosure preferably further has a layer C in addition to the layer A and the layer B, and more preferably has the layer B, the layer A, and the layer C in this order.

[0127] <Layer C> Layer C is preferably an adhesive layer, that is, Layer C is preferably a surface layer (outermost layer).

[0128] From the viewpoint of the dielectric loss tangent of the laminate, it is preferable that Layer C contains at least one polymer.

[0129] The preferred embodiments of the polymer used in Layer C are the same as the preferred embodiments of the polymer used in Layer A having a dielectric loss tangent of 0.01 or less.

[0130] The polymer contained in Layer C may be the same as or different from the polymer contained in Layer A or Layer B. However, from the viewpoint of adhesion between Layer A and Layer C, it is preferable that the polymer be the same as the polymer contained in Layer A.

[0131] Furthermore, the layer C preferably contains an epoxy resin to bond the metal layer and the layer A together.

[0132] The epoxy resin is preferably a crosslinked product of a polyfunctional epoxy compound. A polyfunctional epoxy compound is a compound having two or more epoxy groups. The number of epoxy groups in the polyfunctional epoxy compound is preferably 2 to 4.

[0133] In particular, from the viewpoints of the dielectric loss tangent of the laminate and the adhesiveness to the metal layer, it is preferable that Layer C contains an aromatic polyester amide and an epoxy resin.

[0134] Layer C may contain a filler. Preferred embodiments of the filler used in Layer C are the same as preferred embodiments of the filler used in Layer A.

[0135] 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.

[0136] 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 laminate and adhesion to metal.

[0137] Average thickness T of layer A Ａ and the average thickness T of layer C Ｃ T, which is the ratio ofＡ / T Ｃ From the viewpoint of the dielectric loss tangent of the laminate 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 viewpoint of the dielectric loss tangent of the laminate 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.

[0138] Furthermore, from the viewpoints of the dielectric loss tangent of the laminate 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.

[0139] The method for measuring the average thickness of each layer in the polymer film according to the present disclosure is as follows.

[0140] The polymer film is cut in a plane perpendicular to the plane of the polymer film, and the thickness is measured at five or more points on the cross section, and the average value of the measurements is taken as the average thickness.

[0141] <Physical Properties of Polymer Film> The polymer film according to the present disclosure has a dielectric loss tangent of 0.01 or less, preferably 0.005 or less, and more preferably greater than 0 and 0.003 or less.

[0142] 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 a resonance perturbation method. A 10 GHz cavity resonator (CP531 manufactured by Kanto Electronics Application Development Co., Ltd.) is connected to a network analyzer (E8363B manufactured by Agilent Technology Corporation), a polymer film is inserted into the cavity resonator, and the dielectric loss tangent 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.

[0143] The average thickness of the polymer film according to the present disclosure is not particularly limited, but from the viewpoint of the dielectric loss tangent and the ability to conform to unevenness, it is preferably 5 μm to 90 μm, more preferably 10 μm to 70 μm, and particularly preferably 15 μm to 50 μm.

[0144] The average thickness of the polymer 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.

[0145] <Method for Producing Polymer Film> (Film Formation) The method for producing the polymer film according to the present disclosure is not particularly limited, and known methods can be used.

[0146] Suitable film-forming methods include, for example, co-casting, multi-layer coating, co-extrusion, etc. Among these, the co-casting method is preferred.

[0147] When a multilayer structure is produced by a co-casting method or a multi-layer coating method, it is preferable to carry out the co-casting method or the multi-layer coating method using a 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.

[0148] Examples of the solvent include halogenated hydrocarbons such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-chlorobutane, chlorobenzene, and o-dichlorobenzene; halogenated phenols such as p-chlorophenol, pentachlorophenol, and pentafluorophenol; ethers such as diethyl ether, tetrahydrofuran, and 1,4-dioxane; ketones such as acetone and cyclohexanone; esters such as ethyl acetate and γ-butyrolactone; and ethylene carbonate. nitriles such as acetonitrile and succinonitrile; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and urea compounds such as tetramethylurea; nitro compounds such as nitromethane and nitrobenzene; sulfur compounds such as dimethyl sulfoxide and sulfolane; and phosphorus compounds such as hexamethylphosphoramide and tri-n-butylphosphoric acid, and two or more of these may be used.

[0149] As the solvent, a solvent mainly composed of an aprotic compound, particularly an aprotic compound having no halogen atoms, is preferred because it is less corrosive and easier to handle, and the proportion of the aprotic compound in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. Furthermore, as the aprotic compound, an amide such as N,N-dimethylformamide, N,N-dimethylacetamide, tetramethylurea, N-methylpyrrolidone, or an ester such as γ-butyrolactone is preferably used because it easily dissolves the liquid crystal polymer, and N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone are more preferred.

[0150] Furthermore, as the solvent, a solvent containing as a main component a compound having a dipole moment of 3 to 5 is preferred because it easily dissolves the liquid crystal polymer, and the proportion of the compound having a dipole moment of 3 to 5 in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. It is preferable to use a compound having a dipole moment of 3 to 5 as the aprotic compound.

[0151] Furthermore, as the solvent, a solvent containing as a main component a compound having a boiling point of 220°C or lower at 1 atmosphere is preferred because it is easy to remove, and the proportion of the compound having a boiling point of 220°C or lower at 1 atmosphere in the entire solvent is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, and particularly preferably 90% by mass to 100% by mass. It is preferable to use a compound having a boiling point of 220°C or lower at 1 atmosphere as the aprotic compound.

[0152] In addition, in the method for producing a polymer film according to the present disclosure, when the film is produced by the co-casting method, multi-layer coating method, co-extrusion method, or the like, a support may be used.

[0153] Examples of the support include a metal drum, a metal band, a glass plate, a resin film, and a metal foil, and among these, the support is preferably a metal drum, a metal band, or a resin film.

[0154] The support may have a surface treatment layer formed on its surface to facilitate peeling. The surface treatment layer may be formed of hard chrome plating, fluororesin, or the like. The average thickness of the support is not particularly limited, but is preferably 25 μm or more and 75 μm or less, and more preferably 50 μm or more and 75 μm or less.

[0155] The method for removing at least a part of the solvent from the cast or coated film-like composition (coating film) is not particularly limited, and any known drying method can be used.

[0156] (Stretching) The polymer film manufacturing method according to the present disclosure can be appropriately combined with stretching in order to control molecular orientation and adjust the thermal 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 laminate and stretching, or by utilizing autogenous shrinkage due to drying without stretching. Stretching is particularly effective for improving breaking elongation and breaking strength when the film brittleness has decreased due to the addition of an inorganic filler or the like.

[0157] <Applications> The polymer film according to the present disclosure can be used for various applications. In particular, it can be suitably used as a film for electronic components such as printed wiring boards, and more suitably used for flexible printed circuit boards. Furthermore, the polymer film according to the present disclosure can be suitably used as a liquid crystal polymer film for metal bonding.

[0158] [Laminate] A laminate according to the present disclosure includes a polymer film according to the present disclosure and a metal layer or metal wiring disposed on at least one surface of the polymer film according to the present disclosure.

[0159] The layer configuration of the laminate according to the present disclosure may be as follows: Aspect 1: Metal layer / polymer film (Layer A / Layer B) Aspect 2: Metal layer / polymer film (Layer C / Layer A / Layer B) Aspect 3: Metal layer (also referred to as second metal layer) / polymer film (Layer A / Layer B) / metal layer Aspect 4: Metal layer (also referred to as second metal layer) / polymer film (Layer C / Layer A / Layer B) / metal layer In Aspects 1 to 4 above, the metal layer may be replaced with a metal wiring.

[0160] The laminate according to the present disclosure preferably includes, in this order, Layer B, Layer A, and a metal layer. Specific examples include the above-mentioned Aspect 1 and Aspect 2.

[0161] The laminate according to the present disclosure preferably further includes a second metal layer, and includes the second metal layer, Layer A, Layer B, and a metal layer or metal wiring in this order. Specific examples include the above-mentioned Aspects 3 and 4.

[0162] The metal layer or metal wiring may be made of a conventionally known material, preferably silver or copper, and more preferably copper.

[0163] Metal layers or metal wirings may be disposed on both sides of the polymer film. In this case, the two metal layers or metal wirings may be made of the same material, thickness, and shape, or may be made of different materials, thicknesses, and shapes. From the viewpoint of adjusting the characteristic impedance, the two metal layers or metal wirings may be made of different materials and thicknesses.

[0164] In one embodiment, the metal layer is a rolled metal foil formed by a rolling method or an electrolytic metal foil formed by an electrolytic method.

[0165] The metal layer or metal wiring is disposed on Layer B of the polymer film, and the peel strength between Layer B and the metal layer or metal wiring is preferably 0.3 kN / m or more, more preferably 0.5 kN / m or more, and even more preferably 0.5 kN / m or more. The upper limit of the peel strength is not particularly limited, but may be 5 kN / m from the viewpoint of processability.

[0166] In the present disclosure, the peel strength between Layer B and the metal layer or metal wiring is measured by the following method: A 1.0 cm wide peel test piece is prepared from a laminate (metal-attached laminate) of a polymer film and a metal layer or metal wiring, and the peel test piece is fixed to a flat plate with double-sided adhesive tape. The peel strength (kN / m) is measured when peeled at a rate of 50 mm / min by the 90° method in accordance with JIS C 5016 (1994).

[0167] The average thickness of the metal layer is not particularly limited, but is preferably 2 μm to 20 μm, more preferably 3 μm to 18 μm, and even more preferably 5 μm to 12 μm.

[0168] When the metal layer is a copper foil, the copper foil may be a carrier-attached copper foil formed on a support (carrier) in a peelable manner. 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.

[0169] The metal layer may have a circuit pattern. It is also preferable to process the metal layer into a desired circuit pattern by etching, for example, to form a flexible printed circuit board. The etching method is not particularly limited, and known etching methods can be used.

[0170] The laminate according to the present disclosure can be produced by using a metal layer or metal wiring as the support in the method for producing a polymer film according to the present disclosure. The metal layer or metal wiring may be provided by thermocompression bonding or the like on the surface of the polymer film opposite to the side on which the support is provided.

[0171] The thermocompression temperature is preferably 140°C to 300°C, more preferably 160°C to 280°C, and even more preferably 210°C to 240°C.

[0172] From the viewpoint of heat resistance and conformability to unevenness, the pressure in the thermocompression bonding is preferably 1 MPa to 15 MPa, more preferably 2 MPa to 10 MPa, and even more preferably 3 MPa to 8 MPa.

[0173] From the viewpoint of heat resistance and conformability to unevenness, the time for the thermocompression bonding is preferably 10 to 300 minutes, more preferably 30 to 240 minutes, and even more preferably 45 to 180 minutes.

[0174] 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.

[0175] Details of the materials used in the preparation of the polymer film and laminate are as follows.

[0176] <<Layer B>> <Material a>> A1: Frozen and pulverized hydrogenated styrene-isobutylene-styrene block copolymer (product name "SIBSTAR103T-UL", manufactured by Kaneka Corporation) swollen with N-methylpyrrolidone, average particle size 5.0 μm (D50) A2: Polyethylene particles (product name "Flow Beads CL-2080", manufactured by Sumitomo Seika Chemicals Co., Ltd., median particle size 11 μm)

[0177] <Material b> P1: Aromatic polyesteramide prepared according to the following production method

[0178] -Synthesis of aromatic polyesteramide P1- A reactor equipped with a stirrer, torque meter, nitrogen gas inlet tube, thermometer, and reflux condenser was charged with 940.9 g (5.0 mol) of 6-hydroxy-2-naphthoic acid, 415.3 g (2.5 mol) of isophthalic acid, 377.9 g (2.5 mol) of acetaminophen, and 867.8 g (8.4 mol) of acetic anhydride. The gas inside the reactor was replaced with nitrogen gas, and then the mixture was heated from room temperature (23°C, the same applies hereinafter) to 140°C over 60 minutes while stirring under a nitrogen gas stream, and refluxed at 140°C for 3 hours. Next, while distilling off by-product acetic acid and unreacted acetic anhydride, the mixture was heated from 150°C to 300°C over 5 hours and held at 300°C for 30 minutes. The contents were then removed from the reactor and cooled to room temperature. The resulting solid was pulverized in a grinder to obtain powdered aromatic polyesteramide P1a. The flow initiation temperature of the aromatic polyesteramide P1a was 193°C. The aromatic polyesteramide P1a was a wholly aromatic polyesteramide. The aromatic polyesteramide P1a was heated from room temperature to 160°C over 2 hours and 20 minutes under a nitrogen atmosphere, then heated from 160°C to 180°C over 3 hours and 20 minutes, and held at 180°C for 5 hours to undergo solid-state polymerization, followed by cooling. The mixture was then pulverized in a grinder to obtain a powdered aromatic polyesteramide P1b. The flow initiation temperature of the aromatic polyesteramide P1b was 220°C. The aromatic polyesteramide P1b was heated from room temperature to 180°C over 1 hour and 25 minutes under a nitrogen atmosphere, then heated from 180°C to 255°C over 6 hours and 40 minutes, and held at 255°C for 5 hours to undergo solid-state polymerization, followed by cooling to obtain a powdered aromatic polyesteramide P1. The flow initiation temperature of the aromatic polyesteramide P1 was 302°C. The melting point of the aromatic polyesteramide P1 was measured using a differential scanning calorimeter and found to be 311° C. The dielectric dissipation factor of the aromatic polyesteramide P1 was 0.003.

[0179] <<Layer A>> <Polymer> Aromatic polyester amide P1 described above <Filler> F1: Liquid crystal polymer particles prepared according to the following production method (average particle size 7 μm, melting point 334° C.) F2: Crushed liquid crystal polymer particles F1 (average particle size 3 μm, melting point 334° C.) F3: Boron nitride particles (product name "SHP-7", manufactured by Mizushima Ferroalloy Co., Ltd., average particle size 2 μm, melting point 2900° C.) F4: Crushed liquid crystal polymer particles (product name "UENO LCP A-8100", manufactured by Ueno Pharmaceutical Co., Ltd., average particle size 5 μm, melting point 220° C.)

[0180] -Synthesis of Liquid Crystal Polymer Particles F1- 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, it was cooled to room temperature over 5 hours. The obtained liquid crystalline polyester was pulverized using a jet mill (Kurimoto Iron Works, Ltd., "KJ-200") to obtain liquid crystalline polymer particles F1. The liquid crystalline polymer particles F1 had a median diameter (D50) of 7 μm, a dielectric dissipation factor of 0.0007, and a melting point of 334°C.

[0181] <Copper Foil> M1A: Copper foil with product name "CF-T9DA-SV-18" manufactured by Fukuda Metal Foil & Powder Co., Ltd., having an average thickness of 18 μm, on the treated side of which a 3 μm-thick layer C was formed by the following method. - Formation of Layer C - 8 parts by mass of aromatic polyesteramide P1 was added to 92 parts by mass of N-methylpyrrolidone and stirred at 140°C for 4 hours under a nitrogen atmosphere to obtain a solution of aromatic polyesteramide P1 (solid content concentration 8% by mass). A solution was prepared by mixing 9.96 parts by mass of the aromatic polyesteramide P1 solution with 0.04 parts by mass of an aminophenol-type epoxy resin (product name "jER630" manufactured by Mitsubishi Chemical Corporation). The obtained solution was applied to the treated side of the copper foil using a bar coater and dried at 40°C for 4 hours to remove the solvent from the coating, yielding a copper foil with a 3 μm-thick layer C formed thereon. M1B: Product name "CF-T9DA-SV-18", manufactured by Fukuda Metal Foil & Powder Co., Ltd., average thickness 18 μm M2: Product name "MT18FL", manufactured by Mitsui Mining & Smelting Co., Ltd., average thickness 1.5 μm, with 18 μm carrier foil M3: Product name "CF-T49A-DS-18", manufactured by Fukuda Metal Foil & Powder Co., Ltd., average thickness 18 μm

[0182] Next, in order to prepare a polymer film, a solution for forming a layer A and a solution for forming a layer B were prepared.

[0183] - Preparation of Layer A Forming Solution - As shown in Table 1, a layer A forming solution was prepared by mixing method A or mixing method B. (1) Mixing Method A: The polymers and fillers shown in Table 1 were mixed in the amounts (mass%) shown in Table 1, N-methylpyrrolidone was added to adjust the solids concentration to 25 mass%, and the mixture was stirred with a magnetic stirrer for 10 hours to obtain a layer A forming solution. (2) Mixing Method B: The polymers and fillers shown in Table 1 were mixed in the amounts (mass%) shown in Table 1, N-methylpyrrolidone was added to adjust the solids concentration to 25 mass%. The mixture was treated with zirconia beads (D50 = 1 mm) using a bead mill (Ashizawa Finetech Co., Ltd., Labostar Mini MGF015) for 30 minutes to obtain a layer A forming solution.

[0184] —Preparation of Layer B Forming Solution— Materials a and b shown in Table 1 were mixed in the amounts (mass %) shown in Table 1, and N-methylpyrrolidone was added to adjust the solids concentration to 20 mass %, thereby obtaining a layer B forming solution.

[0185] [Preparation of Polymer Films Having a Copper Layer (Single-Sided Copper-Clad Laminate)] - Films 1 to 7, 9 to 12 - The obtained Layer A-forming solution and Layer B-forming solution were fed into a slot die coater equipped with a slide coater, and applied to the treated surface of the cylinders shown in Table 1 by adjusting the flow rate to achieve the film thickness shown in Table 1. The solvent was removed from the coating by drying at 40°C for 4 hours. The temperature was then raised from room temperature (25°C) to 300°C at a rate of 1°C / min under a nitrogen atmosphere. Heat treatment was performed by holding at 300°C for 2 hours, and a laminate (single-sided copper-clad laminate) in which copper foil, Layer A, and Layer B were laminated in this order was obtained.

[0186] -Film 8- (Preparation of Film A) The obtained layer A-forming solution was transferred to a slot die coater equipped with a slide coater, and the flow rate was adjusted to coat the treated surface of copper foil M1A with a film thickness of 20 μm. The solvent was removed from the coating by drying at 40°C for 4 hours. The temperature was then increased from room temperature (25°C) to 300°C at a rate of 1°C / min under a nitrogen atmosphere. A heat treatment was performed by holding at 300°C for 2 hours to obtain a laminate (Film A) in which Layer A was formed on the copper foil. (Preparation of Film B) The obtained layer B-forming solution was transferred to a slot die coater equipped with a slide coater, and the flow rate was adjusted to coat the support with a film thickness of 30 μm. The solvent was removed from the coating by drying at 40°C for 4 hours. The temperature was then increased from room temperature (25°C) to 300°C at a rate of 1°C / min under a nitrogen atmosphere. A heat treatment was performed by holding at 300°C for 2 hours to obtain a laminate (Film B) in which Layer B was formed on the support. A fluororesin film (product name "NITOFLON #900UL", manufactured by Nitto Denko Corporation, average thickness 50 μm) was used as the support. (Preparation of Film 8) The Layer A side of the obtained Film A and the Layer B side of Film B were overlapped, and a lamination process was carried out for 1 minute using a laminator (product name "Vacuum Laminator V-130", manufactured by Nikko Materials Co., Ltd.) at 140°C and a lamination pressure of 0.4 MPa, to obtain a laminate in which the copper foil, Layer A, Layer B, and support were laminated in this order. The support on the Layer B side was peeled off, and a laminate (single-sided copper-clad laminate) in which the copper foil, Layer A, and Layer B were laminated in this order was obtained.

[0187] [Preparation of Double-Sided Copper-Clad Laminates] Using the prepared Films 1 to 12, the Layer B side of each film was laminated with the copper foil listed in Table 2. This resulted in a laminate in which the copper foil, Layer A, Layer B, and copper foil were laminated in this order. Using a laminator (product name "Vacuum Laminator V-130", manufactured by Nikko Materials Co., Ltd.), lamination was performed for 1 minute at 140°C and a lamination pressure of 0.4 MPa to obtain a precursor of a double-sided copper-clad laminate. Subsequently, using a thermocompression bonder (product name "MP-SNL", manufactured by Toyo Seiki Seisakusho, Ltd.), the obtained precursor of a double-sided copper-clad laminate was thermocompressed at 230°C and 4 MPa for 60 minutes to produce a double-sided copper-clad laminate. For the laminate using Film 6, the carrier copper foil was peeled off.

[0188] [Preparation of 4-Layer Copper-Clad Laminate] For the laminate using Film 6, the carrier copper foil was peeled off in advance. Using the prepared Films 1 to 12, each film was overlapped with the other so that Layer B and the copper foil were in contact. Furthermore, the Layer B side of the outermost film was overlapped with the copper foil listed in Table 2. This resulted in a laminate stacked in the following order: "copper foil, Layer A, Layer B" / "copper foil, Layer A, Layer B" / "copper foil, Layer A, Layer B" / "copper foil, Layer A, Layer B" / copper foil. Using a laminator (product name "Vacuum Laminator V-130", manufactured by Nikko Materials Co., Ltd.), lamination was performed for 1 minute at 140°C and a lamination pressure of 0.4 MPa to obtain a precursor of a 4-layer 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 230 ° C. and 4 MPa for 60 minutes to produce a four-layer copper-clad laminate.

[0189] [Preparation of wiring board] -Preparation of substrate A 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 foil 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 for 10 minutes under conditions of 300 ° C and 4.5 MPa to produce a double-sided copper-clad laminate. The surfaces of the copper foil on both sides of the double-sided copper-clad laminate were roughened, and a dry film resist was attached. After exposure and development so that the wiring pattern remained, etching was performed, and the dry film was then removed to produce a substrate A with a wiring pattern having a line / space of 100 μm / 100 μm 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.

[0190] - Preparation of substrate B with wiring pattern - Copper foil (product name "MT18FL", average thickness 1.5 μm, with carrier copper foil (thickness 18 μm), manufactured by Mitsui Mining & Smelting 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 and the substrate 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 treatment was performed for 1 minute under conditions of 140°C and a lamination pressure of 0.4 MPa, to obtain a precursor of a single-sided copper foil laminate. Next, using a thermocompression bonding machine (product name "MP-SNL", manufactured by Toyo Seiki Seisakusho, Ltd.), the obtained precursor of the single-sided copper-clad laminate was thermocompressed for 10 minutes under conditions of 300 ° C and 4.5 MPa to produce a single-sided copper-clad laminate. The carrier copper foil on the side opposite the substrate of the single-sided copper-clad laminate was peeled off, and the surface of the exposed 1.5 μm copper foil was roughened and laminated with a dry film resist. After pattern exposure and development, the areas where the resist pattern was not located were plated. Furthermore, the dry film resist was peeled off, and the copper exposed by the peeling process was removed by flash etching to produce a substrate B with a wiring pattern having a line / space of 20 μm / 20 μm.

[0191] -Preparation of wiring board- The prepared substrate with wiring pattern was superimposed on the layer B side of the prepared single-sided copper-clad laminate, and a wiring board was obtained by hot pressing for 1 hour under conditions of 160°C and 4 MPa. The obtained wiring board had a wiring pattern (ground line and signal line) embedded therein, and when substrate A with wiring pattern was used, the thickness of the wiring pattern was 18 μm, and when substrate B with wiring pattern was used, the thickness of the wiring pattern was 12 μm.

[0192] The prepared polymer films and wiring substrates were subjected to the following measurements and evaluations, and the results are shown in Tables 1 and 2.

[0193] <<Measurement Method>> [Elastic Modulus of Layer A and Layer B at 160°C, Elastic Modulus of Layer B at 25°C] A cross section of a double-sided copper-clad laminate was exposed using a cryomicrotome. Next, Layer A and Layer B were identified, and the elastic modulus of Layer A and Layer B at 160°C and the elastic modulus of Layer B at 25°C were measured as indentation modulus using a nanoindentation method. The indentation modulus was measured using a microhardness tester (product name "DUH-W201" manufactured by Shimadzu Corporation) 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. Measurements were taken at 20 random positions on the cross-sectional sample at 160°C or 25°C, and the average value was used as the elastic modulus.

[0194] [Elastic modulus of material a at 260°C] A cross section of a double-sided copper-clad laminate was exposed using a cryomicrotome. Next, material a in layer B was identified, and the elastic modulus of material a at 260°C 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) 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.

[0195] [Elastic modulus of material b at 260°C] A cross section of a double-sided copper-clad laminate was exposed using a cryomicrotome. Next, material b in layer B was identified, and the elastic modulus of material b at 260°C 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) 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.

[0196] [Surface Roughness Rc] The surface roughness Rc of the side of Layer A where Layer B was disposed was measured by exposing a cross section of the double-sided copper-clad laminate using a cryomicrotome, extracting the interface of Layer A on the Layer B side using an optical microscope, and measuring the average height Rc in accordance with JIS B0601 2001. The evaluation length was 500 μm.

[0197] [Average particle size] A cross section of a double-sided copper-clad laminate was exposed using a cryomicrotome. The cross section was observed under a scanning electron microscope (SEM) at 10,000x magnification in 100 fields of view, and 100 particles were randomly selected. The lengths of the selected particles in the major axis direction were measured, and the average value was taken as the average particle size.

[0198] [Dielectric loss tangent] The copper foil of a double-sided copper-clad laminate was removed with an aqueous solution of ferric chloride, washed with pure water, and dried to obtain a polymer film. The dielectric loss tangent was measured using a resonance perturbation method at a frequency of 10 GHz. A 10 GHz cavity resonator (Kanto Electronics Application Development Co., Ltd., CP531) was connected to a network analyzer (Agilent Technology, Inc., E8363B). The polymer film was inserted into the cavity resonator, and the dielectric loss tangent of the polymer 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.

[0199] <<Evaluation Method>> [Step Conformability] The wiring board was cut in the thickness direction with a microtome, and the cross section was observed with an optical microscope. The length L1 of the gap occurring in the in-plane direction between layer B and the wiring pattern was measured. The average value for 10 locations was calculated. The evaluation criteria are as follows: A: No gap was observed. B: The average value of L1 was less than 1 μm. C: The average value of L1 was 1 μm or more.

[0200] [Peel Strength] The metal layer of the prepared double-sided copper-clad laminate was electrolytically plated to a thickness of 50 μm. The support side was fixed to a flat plate with double-sided adhesive tape, and the metal layer was peeled from the double-sided copper-clad laminate at a rate of 50 mm / min in an environment of 25°C and 50% relative humidity by the 90° method in accordance with JIS C 5016 (1994), to measure the peel strength (kN / m) between Layer B and the metal layer.

[0201] [Heat Resistance] The four-layer copper-clad laminate was cut into a size of 30 mm x 30 mm to prepare an evaluation sample. The evaluation sample was treated for 168 hours in a thermo-hygrostat chamber at a temperature of 85°C and a relative humidity of 85%. The evaluation sample was then placed in an oven set to 260°C and heated for 15 minutes. After heating, the evaluation sample was cut with a razor, and the cross section was observed under an optical microscope to visually evaluate the state of peeling. A: No distortion of the laminate was observed, and no peeling was observed between Layer B and the copper foil. B: Distortion of the laminate was observed, but no peeling was observed between Layer B and the copper foil. C: Peeling was observed between Layer B and the copper foil with a width of 0.1 mm or less. D: Peeling was observed between Layer B and the copper foil with a width of more than 0.1 mm.

[0202]

[0203]

[0204] As shown in Table 2, Examples 1 to 7 include a layer A and a layer B disposed on at least one surface of layer A, and layer A has a surface roughness Rc of 5 μm or less on the side where layer B is disposed. Layer B includes a material a having an elastic modulus of less than 0.10 MPa at 260° C. and a material b having an elastic modulus of 0.10 MPa or more at 260° C., and has an elastic modulus of 500 MPa or less at 25° C. and an elastic modulus of 0.60 MPa or less at 160° C., and a dielectric dissipation factor of 0.01 or less, and therefore has excellent step conformability and heat resistance.

[0205] On the other hand, in Comparative Example 1, the surface roughness Rc of Layer A on the side where Layer B was disposed was more than 5 μm, and it was found that the heat resistance was poor.

[0206] In Comparative Example 2, the elastic modulus of Layer B at 25° C. was more than 500 MPa, and it was found that the heat resistance was poor.

[0207] In Comparative Example 3, the layer B did not contain material a, and it was found that the step conformability was poor.

[0208] In Comparative Example 4, the layer B did not contain material b, and it was found that the heat resistance was poor.

[0209] In Comparative Example 5, the elastic modulus of Layer B at 160° C. was greater than 0.6 MPa, and it was found that the step-following ability was poor.

[0210] In Examples 2 and 3, layer A contained particles having a melting point of 300° C. or higher, and it was found that these had superior heat resistance compared to Example 7.

[0211] In Examples 2 and 3, the particles contained in Layer A and having a melting point of 300° C. or higher had an average particle size of 4.0 μm or less, and it was found that these examples had superior heat resistance compared to Example 1.

[0212] The disclosure of Japanese Patent Application No. 2023-108857, filed on June 30, 2023, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. A polymer film comprising a layer A and a layer B disposed on at least one surface of the layer A, wherein the layer A has a surface roughness Rc of 5 μm or less on the side on which the layer B is disposed, the layer B comprises a material a having an elastic modulus of less than 0.10 MPa at 260°C and a material b having an elastic modulus of 0.10 MPa or more at 260°C, the layer B having an elastic modulus of 500 MPa or less at 25°C and an elastic modulus of 0.60 MPa or less at 160°C, and a dielectric loss tangent of 0.01 or less.

2. The polymer film according to claim 1, wherein said material A is an elastomer containing structural units derived from styrene.

3. The polymer film according to claim 1, wherein the material a is at least one selected from the group consisting of styrene-ethylene-butylene-styrene block copolymers, styrene-isobutylene-styrene block copolymers, styrene-ethylene-propylene-styrene copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products thereof.

4. The polymer film according to claim 1, wherein said material b is at least one selected from the group consisting of liquid crystal polymers, polymers of compounds having a cyclic aliphatic hydrocarbon group and a group having an ethylenically unsaturated bond, and fluororesins.

5. The polymer film according to claim 1, wherein said layer A contains particles having a melting point of 300° C. or higher.

6. The polymer film according to claim 5, wherein the particles have an average particle size of 4.0 μm or less.

7. The polymer film according to claim 1, wherein the layer A has an elastic modulus of more than 0.60 MPa at 160°C.

8. A laminate comprising the polymer film according to any one of claims 1 to 7 and a metal layer or metal wiring disposed on at least one surface of the polymer film.

9. The laminate of claim 8, comprising, in that order, layer B, layer A, and metal layer.

10. The laminate of claim 8, further comprising a second metal layer, the second metal layer, the layer A, the layer B, and the metal layer or metal wiring, in that order.

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