Syndiotactic polystyrene low transmission loss circuit board

Abstract

The objective of the present invention is to provide a laminate that has excellent peel strength and low transmission loss, and is suitable for use in an electronic circuit board.　The present invention relates to a laminate in which a resin layer (i), an adhesive layer (ii), and a metal layer (iii) are layered in the stated order, wherein the resin layer (i) contains a styrene-based polymer (A) having a syndiotactic structure, the coefficient of linear expansion of the resin layer (i) in the longitudinal direction (MD) and the transverse direction (TD) is 10-80 ppm / °C, the ratio of MD / TD satisfies the range of 0.6-1.4, the peel strength between the layers of the resin layer (i) and the adhesive layer (ii) is 0.3 kN / m or greater, and the absolute value of the transmission loss of the laminate at a frequency of 40 GHz is 5.0 dB / 100 mm or less.

Description

Syndiotactic polystyrene low transmission loss circuit board

[0001] The present invention relates to a laminate having extremely low transmission loss and suitable for use as an electronic circuit board. More specifically, the present invention relates to a laminate comprising a sheet or film made of a syndiotactic polystyrene polymer having excellent dielectric properties and dimensional stability, an adhesive layer having excellent adhesion to the syndiotactic polystyrene polymer, and a metal layer having a low surface roughness.

[0002] In recent years, there has been active development of materials and applications for high-speed information communications such as 5G, and to improve information transmission speeds, there is a demand for plastic materials with low dielectric constants and dielectric loss tangents in the high-frequency band above 10 GHz. There is a similar need for printed wiring boards using plastics with these excellent dielectric properties, and there is a demand for boards with even lower transmission loss.

[0003] Such circuit boards are often exposed to high-temperature environments during use and manufacturing, and therefore generally require high heat resistance and dimensional stability. Heat resistance here refers to the ability to withstand the heat treatment conditions (e.g., 260°C, 120 seconds) that occur during the soldering process that is part of the manufacturing process of circuit boards and electronic components.

[0004] Therefore, it is necessary to use a plastic with excellent heat resistance that can withstand the soldering process, and fluororesin (PTFE) is used for printed wiring boards that require low transmission loss (Patent Document 1).

[0005] Furthermore, flexible printed wiring boards with excellent dielectric properties are being investigated by forming a wiring pattern made of a metal layer on a film of syndiotactic polystyrene (SPS) by electroless plating or vapor deposition (Patent Document 2).

[0006] JP 2003-171480 A JP 2015-2334 A

[0007] However, the fluororesins described in Patent Document 1, such as PTFE, have poor adhesion to metal foils, making it difficult to laminate them with metal foils with low surface roughness. Therefore, copper foils with rough surfaces must be used, which increases the transmission loss of the PTFE substrate in the high-frequency range. In addition, special treatments such as ultraviolet irradiation are required to improve adhesion, which complicates the manufacturing process and reduces productivity, resulting in increased manufacturing costs for the substrate.

[0008] The SPS printed wiring board described in Patent Document 2 has excellent dielectric properties, but is not able to withstand the ambient temperature (260°C or higher) during the soldering process. In addition, because the metal layer is directly attached to the SPS substrate by plating or vapor deposition, stress is generated due to the difference in linear expansion coefficient between the metal layer and the substrate, which causes the wiring pattern of the metal layer to peel off at the interface with the substrate, making it impractical.

[0009] In view of the above circumstances, an object of the present invention is to provide a laminate that is excellent in peel strength and transmission loss between a resin layer and an adhesive layer.

[0010] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention is a laminate for an electronic circuit board as set forth in the following claims.

[0011] [1] A laminate comprising a resin layer (i), an adhesive layer (ii), and a metal layer (iii) laminated in this order, wherein the resin layer (i) contains a styrene-based polymer (A) having a syndiotactic structure, the resin layer (i) has a linear expansion coefficient in the machine direction (MD) and the transverse direction (TD) of 10 to 80 ppm / °C, with an MD / TD ratio in the range of 0.6 to 1.4, the interlaminar peel strength between the resin layer (i) and the adhesive layer (ii) being 0.3 kN / m or greater, and the absolute value of the transmission loss of the laminate at a frequency of 40 GHz being 5.0 dB / 100 mm or less. [2] The laminate according to [1], wherein the surface roughness Rz of the resin layer (i) is 0.1 μm or greater and 6.0 μm or less. [3] The laminate according to [1] or [2], wherein the surface roughness Rz of the resin layer (i) is 0.1 μm or greater and 3.0 μm or less. [4] The laminate according to any one of [1] to [3], wherein the adhesive layer (ii) contains a styrene-based elastomer and a curing agent. [5] The laminate according to any one of [1] to [4], wherein the metal layer (iii) has a surface roughness Rz of 0.1 μm or more and 7.0 μm or less. [6] The laminate according to any one of [1] to [5], wherein the resin layer (i) further contains a fibrous filler (C). [7] The laminate according to any one of [1] to [5], wherein the resin layer (i) further contains a non-fibrous filler (D). [8] The laminate according to any one of [1] to [5], wherein the resin layer (i) further contains a fibrous filler (C) and a non-fibrous filler (D). [9] The laminate according to any one of [1] to [5], wherein the resin layer (i) further contains a fibrous filler (C) and a non-fibrous filler (D), and the amount of the fibrous filler (C) is 1 to 50 parts by mass per 100 parts by mass of the styrene-based polymer (A) having a syndiotactic structure.

[10] The laminate according to any one of [1] to [9], wherein the laminate is used for an electronic circuit board.

[0012] The laminate of the present invention is excellent in peel strength and transmission loss between the resin layer and the adhesive layer. Furthermore, the laminate of some embodiments of the present invention is also excellent in solder heat resistance. The laminate of the present invention can be suitably used for electronic circuit boards.

[0013] <Resin Layer (i)> The resin layer (i) in the laminate of the present invention contains a styrene-based polymer (A) having a syndiotactic structure (hereinafter also referred to as "SPS," "syndiotactic polystyrene," or "component (A)"). The content of component (A) in the resin layer (i) is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, in order to improve the dielectric properties. The upper limit is not particularly limited, but is preferably less than 100% by mass, more preferably 99% by mass or less, and even more preferably 95% by mass or less, in order to improve the linear expansion coefficient and dimensional stability.

[0014] The resin layer (i) is preferably made from an unstretched sheet containing the component (A) or a film obtained by biaxially stretching the unstretched sheet. That is, the unstretched sheet or biaxially stretched film is preferably superimposed on the adhesive composition and the metal layer and subjected to a heat press treatment. Hereinafter, the unstretched sheet will be simply referred to as a "sheet" and the biaxially stretched film will be simply referred to as a "film," and these will be collectively referred to as "sheet, etc."

[0015] The resin layer (i) may contain a fibrous filler (C) in addition to the styrene-based polymer (A) having a syndiotactic structure. When the fibrous filler (C) is contained, the content thereof is preferably 1 to 50 parts by mass of the fibrous filler (C) per 100 parts by mass of the styrene-based polymer (A) having a syndiotactic structure. The resin layer (i) may contain a non-fibrous filler (D) in addition to the styrene-based polymer (A) having a syndiotactic structure. When the non-fibrous filler (D) is contained, the content thereof is preferably 1 to 60 parts by mass of the non-fibrous filler (D) per 100 parts by mass of the styrene-based polymer (A) having a syndiotactic structure. It is also preferable that the resin layer (i) contains, in addition to the styrene-based polymer (A) having a syndiotactic structure, a fibrous filler (C) and a non-fibrous filler (D), and that the resin layer (i) contains 1 to 50 parts by mass of the fibrous filler (C) per 100 parts by mass of the styrene-based polymer (A) having a syndiotactic structure.

[0016] <Styrenic polymer (A) having syndiotactic structure> In the present invention, the syndiotactic structure in the styrene-based polymer having a syndiotactic structure as the component (A) is a stereochemical structure in which phenyl groups as side chains are alternately positioned in opposite directions relative to a main chain formed from carbon-carbon bonds, and the tacticity is quantified by nuclear magnetic resonance spectroscopy (C-NMR) using a carbon isotope. Tacticity measured by C-NMR can be expressed by the proportion of multiple consecutive structural units present, for example, dyads when there are two, triads when there are three, and pentads when there are five. In the present invention, the styrene polymer having a syndiotactic structure generally refers to polystyrene, poly(alkylstyrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), poly(vinyl benzoate ester), hydrogenated polymers thereof, mixtures thereof, or copolymers containing these as the main component, having a syndiotacticity of preferably 75 mol % or more, more preferably 85 mol % or more in racemic dyads, or preferably 30 mol % or more, more preferably 50 mol % or more in racemic pentads.

[0017] Here, examples of poly(alkylstyrenes) include poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tert-butylstyrene), poly(phenylstyrene), poly(vinylnaphthalene), and poly(vinylstyrene), while examples of poly(halogenated styrenes) include poly(chlorostyrene), poly(bromostyrene), and poly(fluorostyrene). Examples of poly(halogenated alkylstyrenes) include poly(chloromethylstyrene), and examples of poly(alkoxystyrenes) include poly(methoxystyrene), poly(ethoxystyrene), and the like.

[0018] Among these, particularly preferred styrene-based polymers include polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tert-butylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluorostyrene), hydrogenated polystyrene, and copolymers containing these structural units.

[0019] The styrene-based polymer (A) having a syndiotactic structure may be a copolymer of styrene having a syndiotactic structure and another monomer. The content of styrene having a syndiotactic structure in component (A) is preferably 50% by mass or more. It is more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 100% by mass. A content of styrene having a syndiotactic structure of 50% by mass or more results in excellent dielectric properties, solder heat resistance, dimensional change rate, and linear expansion coefficient. In particular, it is preferable to keep the content of unsaturated nitrile group-containing monomers low, as this may result in a deterioration in the above-mentioned performance. Specifically, it is preferably 2% by mass or less, more preferably less than 2% by mass, even more preferably 1% by mass or less, and particularly preferably 0% by mass.

[0020] The styrene polymer (A) having a syndiotactic structure may be used alone or in a mixture of two or more styrene polymers. There are no particular restrictions on the composition ratio of the styrene copolymer, but the content of substituted styrene units is preferably in the range of 3 to 50 mol%. If this content is 3 mol% or more, modification is easy, and if it is 50 mol% or less, compatibility with other components can be maintained.

[0021] There is no particular restriction on the molecular weight of the styrene-based polymer (A) having a syndiotactic structure, but the weight-average molecular weight is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. Furthermore, there is no restriction on the width of the molecular weight distribution, and various types can be used. By setting the weight-average molecular weight to 10,000 or more, the thermal and mechanical properties of the resulting composition or molded article are not reduced and good ones can be obtained. There is no particular restriction on the upper limit, but it is preferably 500,000 or less, more preferably 400,000 or less.

[0022] The styrene polymer (A) having such a syndiotactic structure can be produced, for example, by polymerizing a styrene monomer (a monomer corresponding to the above-mentioned styrene polymer) in an inert hydrocarbon solvent or in the absence of a solvent using a condensation product of a titanium compound, water, and trialkylaluminum as a catalyst (JP-A-62-187708). Poly(halogenated alkylstyrene) can be obtained by the method described in JP-A-1-46912, and hydrogenated polymers thereof can be obtained by the method described in JP-A-1-178505.

[0023] The styrene polymer (A) having a syndiotactic structure preferably has a melt flow rate (MFR) measured at a temperature of 300°C and a load of 1.2 kg of 1 to 60 g / 10 min, more preferably 2 to 40 g / 10 min, even more preferably 3 to 30 g / 10 min, and most preferably 4 to 20 g / 10 min. By setting the melt flow rate within the above range, a sheet or the like that is a precursor of the resin layer (i) having good physical properties can be obtained, and the film thickness can be made uniform.

[0024] The melting point of the styrene polymer (A) having a syndiotactic structure is preferably 250° C. or higher, more preferably 260° C. or higher, and preferably 300° C. or lower, more preferably 290° C. or lower. The glass transition temperature of the styrene polymer (A) having a syndiotactic structure is preferably 80° C. or higher, more preferably 90° C. or higher, and preferably 120° C. or lower, more preferably 110° C. or lower. By setting the melting point and glass transition temperature within the above ranges, the resin layer (i) has a low linear expansion coefficient and good dimensional stability.

[0025] Representative commercially available examples of the styrene-based polymer (A) having a syndiotactic structure used in the present invention include XAREC (registered trademark) 142ZE, XAREC (registered trademark) 300ZC, XAREC (registered trademark) 130ZC, and XAREC (registered trademark) 90ZC manufactured by Idemitsu Kosan Co., Ltd. Among these resins, only one type may be used alone, or two or more types may be used in combination.

[0026] <Rubber-like elastomer (B)> The resin layer (i) preferably contains a rubber-like elastomer (B) (hereinafter also referred to as component (B)). The rubber-like elastomer (B) is preferably incorporated because it imparts appropriate flexibility and improves mechanical properties when winding a sheet or the like, thereby suppressing cracking of the sheet or the like. Examples of the rubber-like elastomer (B) component include a single polymer composed of polyolefin, polystyrene, or polyacrylate, or a composition composed of multiple copolymers containing these components. Specific examples of rubber-like elastomers include natural rubber, polybutadiene, polyisoprene, polyisobutylene, neoprene, polysulfide rubber, thiokol rubber, acrylic rubber, urethane rubber, silicone rubber, epichlorohydrin rubber, ethylene-propylene copolymer rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM), ethylene-α-olefin copolymer rubber, styrene-butadiene block copolymer (SBR), hydrogenated styrene-butadiene block copolymer (SEB, SEBC), styrene-butadiene-styrene block copolymer (SBS), hydrogenated styrene-butadiene-styrene block copolymer (SEBS), styrene-isoprene block copolymer (SIR), hydrogenated styrene-isoprene block copolymer (SEP), styrene-isoprene block copolymer (SIR), hydrogenated styrene-isoprene block copolymer (SEP), styrene-isoprene block copolymer (SBR), hydrogenated styrene-isoprene block copolymer (SEP), styrene-isoprene block copolymer (SBR), hydrogenated styrene-isoprene block copolymer (SEB), styrene-isoprene block copolymer (SBR), hydrogenated styrene-isoprene block copolymer (SEB), styrene-isoprene block copolymer (SBR), hydrogenated styrene-isoprene block copolymer (SEP ... Examples of the core-shell type particulate elastomer include styrene-isoprene block copolymer (SIS), hydrogenated styrene-isoprene-styrene block copolymer (SEPS), butadiene-acrylonitrile-styrene-core-shell rubber (ABS), methyl methacrylate-butadiene-styrene-core-shell rubber (MBS), methyl methacrylate-butyl acrylate-styrene-core-shell rubber (MAS), octyl acrylate-butadiene-styrene-core-shell rubber (MABS), alkyl acrylate-butadiene-acrylonitrile-styrene-core-shell rubber (AABS), butadiene-styrene-core-shell rubber (SBR), and siloxane-containing core-shell rubbers such as methyl methacrylate-butyl acrylate-siloxane, as well as modified rubbers thereof.

[0027] Among these, SEBS, SIR, SEP, SIS, SEPS, ethylene-α-olefin copolymer rubber, or modified rubbers thereof are particularly preferred. These rubbery elastomers can be used alone or in combination of two or more. From the viewpoint of the processing temperature when mixed with the styrene-based polymer (A) having a syndiotactic structure, a rubbery elastomer having high heat resistance is preferred, and mixing a rubbery elastomer in which the unsaturated bonds are selectively or completely hydrogenated suppresses the generation of gas during hot pressing.

[0028] The rubber-like elastomer (B) preferably has a melt flow rate (MFR) of 0.1 to 40 g / 10 min, more preferably 1.0 to 20 g / 10 min, and even more preferably 1.5 to 14 g / 10 min, measured at a temperature of 230° C. and a load of 2.16 kg. By setting the melt flow rate within the above range, compatibility with the styrene-based polymer (A) having a syndiotactic structure is improved, and the thickness of the sheet or the like can be made uniform.

[0029] When the rubber-like elastomer (B) is contained, its content is preferably 1 to 40 parts by mass relative to 100 parts by mass of the styrene copolymer (A) having a syndiotactic structure. It is more preferably 3 to 30 parts by mass, and even more preferably 5 to 25 parts by mass. By making the content of component (B) 1 part by mass or more, the flexibility of the sheet or the like is improved, and the winding property onto a roll is improved. In addition, the drilling processability in the subsequent process is improved. Furthermore, by making the content 40 parts by mass or less, the sheet or the like is prevented from becoming too soft, sticking to the roll is prevented, and the heat resistance required for high-frequency circuit boards can be maintained.

[0030] It is also preferable that the rubber-like elastomer (B) contains a styrene-based thermoplastic elastomer. When the rubber-like elastomer (B) is a styrene-based thermoplastic elastomer, the styrene content is preferably 5 to 60% by mass. It is more preferably 8 to 50% by mass, even more preferably 10 to 40% by mass, and particularly preferably 15 to 32% by mass. By setting the styrene content to 5% by mass or more, the compatibility between the (A) and (B) components is improved, resulting in good mechanical properties. Furthermore, by setting the styrene content to 60% by mass or less, the elastic modulus of the (B) component is not too high, thereby enhancing the stress relaxation effect, improving the flexibility of the sheet, and suppressing the polarity of the resin layer (i) and preventing an increase in the dielectric constant.

[0031] <Fiber Filler (C)> The resin layer (i) preferably contains a fibrous filler (C) (hereinafter also referred to as component (C)). The fibrous filler (C) is a fibrous filler that can improve the linear expansion coefficient and dimensional change suppression effect in the direction parallel to the extrusion direction (MD) of the precursor sheet of the resin layer (i). It is a preferred filler to be contained in the resin layer (i) of the present invention, which may retain some residual strain even when unstretched. Furthermore, the incorporation of component (C) can improve the solder heat resistance of the resin layer (i) and the laminate. The fibrous filler (C) can be inorganic or organic. In the case of inorganic fibers, wollastonite (or whiskers) or glass fibers can be used, with glass fibers being particularly preferred due to their dielectric properties. In order to achieve a balance between the target linear expansion coefficient and the dimensional stability, impact resistance, and mechanical properties, the content of the fibrous filler (C) is preferably 1 to 50 parts by mass, more preferably 3 to 40 parts by mass, and even more preferably 5 to 30 parts by mass, per 100 parts by mass of the styrene-based polymer (A) having a syndiotactic structure.

[0032] The fibrous filler (C) may be in any form, such as roving, surfacing mat, chopped strand mat, satin weave, lattice weave, plain weave, open plain weave, twill weave, or net, and may be of any type, such as alkali-rich glass (C glass) or alkali-free glass (E glass).

[0033] More preferably, glass containing a large amount of boric acid (D glass) or glass with an adjusted balance of silica and boric acid (NE glass) is used. ２ and B ２ O ３ Preferably, the material contains SiO ２ The preferred range of the content is 65.0 to 80.0 mass %, and in this case, B ２ O ３ The preferred range of the content is 15.0 to 30.0 mass %. ２ and B ２ O ３ Preferably, the material contains SiO ２ The preferred range of the content is 45.0 to 65.0 mass %, and in this case, B ２ O ３ The preferred range of the content is 10.0 to 25.0 mass %.

[0034] The cross-sectional shape of the fibrous filler (C) can be either circular or noncircular. Glass fibers with noncircular cross sections include those that are approximately elliptical, approximately oval, or approximately cocoon-shaped in a cross section perpendicular to the fiber length, and in such cases, the flatness is preferably 1.5 to 8. Here, the flatness is the ratio of the major axis to the minor axis, where the length of the long side of the rectangle with the smallest area circumscribing the cross section perpendicular to the longitudinal direction of the glass fiber is the major axis and the length of the short side of the rectangle is the minor axis. The thickness of the glass fiber is not particularly limited, but the minor axis is approximately 1 to 20 μm and the major axis is approximately 2 to 100 μm. For glass fibers with circular cross sections, the fiber diameter is preferably 1 to 50 μm, more preferably 2 to 20 μm, and even more preferably 3 to 15 μm.

[0035] The D50 average fiber length of the fibrous filler (C) is preferably 40 μm to 4000 μm, more preferably 40 μm to 3200 μm, even more preferably 45 μm to 2000 μm, and most preferably 50 μm to 500 μm. When the D50 average fiber length is 40 μm or more, the surface area of ​​the fibrous filler (C) is sufficiently large, improving the adhesion at the interface between the matrix resin components (A) and (C), resulting in good physical properties of the sheet, etc. Furthermore, by setting the length to 4000 μm or less, excessive rigidity of the sheet, etc., during film formation can be prevented, and cracks observed during winding can be suppressed. Furthermore, the generation of aggregates in the sheet, etc. can be suppressed.

[0036] The fibrous filler (C) may or may not be surface-treated. When the fibrous filler (C) is surface-treated, examples of the coupling agent used for the surface treatment include a silane coupling agent and a titanium coupling agent. Among these, surface treatment with a silane coupling agent is particularly preferred from the viewpoint of compatibility with component (A). Specific examples of the silane coupling agent include triethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(1,1-epoxycyclohexyl)ethyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxy ... Examples of suitable silanes include hydroxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltris(2-methoxyethoxy)silane, N-methyl-γ-aminopropyltrimethoxysilane, N-vinylbenzyl-γ-aminopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-4,5-dihydroimidazolepropyltriethoxysilane, hexamethyldisilazane, N,N-bis(trimethylsilyl)urea, and 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine. Among these, aminosilanes and epoxysilanes such as γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane are preferred.

[0037] Specific examples of titanium-based coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, tetra(1,1-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate, and bis(dioctyl pyrophosphate)oxyacetate. titanate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctyl phosphate)titanate, isopropyl tricumyl phenyl titanate, isopropyl tri(N-amidoethyl, aminoethyl)titanate, dicumyl phenyloxyacetate titanate, diisostearoyl ethylene titanate, etc. Among these, isopropyl tri(N-amidoethyl, aminoethyl)titanate is preferred.

[0038] The surface treatment method for the fibrous filler (C) using the coupling agent is not particularly limited. For example, it can be performed by a method appropriate for the shape of the fibrous filler (C), such as a sizing treatment in which an organic solvent solution or suspension of the coupling agent is applied to the fibrous filler (C) as a sizing agent, a dry mixing treatment using a Henschel mixer, super mixer, Loedige mixer, V-type blender, or the like, a spray method, an integral blend method, or a dry concentrate method. Among these, surface treatment by sizing treatment, dry mixing treatment, or a spray method is preferred. A film-forming substance for glass, for example, can be used in combination with the coupling agent. The film-forming substance is not particularly limited, and examples thereof include polyester-based, urethane-based, epoxy-based, acrylic-based, vinyl acetate-based, and polyether-based polymers.

[0039] A modified polymer may be used as a compatibilizer for the fibrous filler (C). The compatibilizer is added for the purpose of improving the interfacial strength between the syndiotactic polystyrene polymer (A) and the fibrous filler (C) and non-fibrous filler (D).

[0040] Specific examples of the compatibilizer include modified polyphenylene ether polymers such as styrene-maleic anhydride copolymer (SMA), styrene-glycidyl methacrylate copolymer, terminal carboxylic acid-modified polystyrene, terminal epoxy-modified polystyrene, terminal oxazoline-modified polystyrene, terminal amine-modified polystyrene, sulfonated polystyrene, styrene-based ionomers, styrene-methyl methacrylate-graft polymer, (styrene-glycidyl methacrylate)-methyl methacrylate-graft copolymer, acid-modified acrylic-styrene-graft polymer, (styrene-glycidyl methacrylate)-styrene-graft polymer, polybutylene terephthalate-polystyrene-graft polymer, polyphenylene ether, (styrene-maleic anhydride)-polyphenylene ether-graft polymer, maleic anhydride-modified polyphenylene ether, fumaric acid-modified polyphenylene ether, glycidyl methacrylate-modified polyphenylene ether, and amine-modified polyphenylene ether. Among these, unmodified or modified polyphenylene ether is preferred, and maleic anhydride-modified polyphenylene ether and fumaric acid-modified polyphenylene ether are more preferred.

[0041] <Non-fibrous filler (D)> The resin layer (i) preferably contains a non-fibrous filler (D) (hereinafter also referred to as component (D)). The non-fibrous filler (D) is a non-fibrous filler that is expected to suppress the linear expansion coefficient and dimensional change in the direction parallel to the extrusion direction (MD) and the direction perpendicular to the extrusion direction (TD) of the precursor sheet of the resin layer (i). As the non-fibrous filler (D), fillers of known shapes such as spherical, granular, and plate-like can be used. Either inorganic or organic fillers may be used, but inorganic spherical, granular, or plate-like fillers are preferred, such as talc, carbon black, graphite, titanium dioxide, silica, mica, calcium carbonate, calcium sulfate, barium carbonate, magnesium carbonate, magnesium sulfate, barium sulfate, oxysulfate, tin oxide, alumina, kaolin, silicon carbide, metal powder, glass powder, glass flakes, and glass beads.

[0042] Among these inorganic fillers, silica is particularly preferred from the viewpoints of productivity, cost, and the dielectric properties of the filler itself, and amorphous silica or fused silica is more preferred. Amorphous silica has lower hardness than crystalline silica, and can suppress wear of machines and screws.

[0043] Fused silica is made by melting the raw material in a flame and then rapidly solidifying the volatilized gas. The resulting spherical shape is formed by surface tension, resulting in few sharp edges and no tendency for the filler itself to crumble, making it easy to form a stable shape.

[0044] The silica is preferably granular or spherical, more preferably spherical. The granular or spherical shape of the silica makes it easy to mix when added to a molten resin. Furthermore, since it is stable regardless of the direction of force, the mechanical properties of the resin layer (i) are less likely to deteriorate, and the silica is less likely to break down and fall off during film formation, such as a sheet.

[0045] The D50 average particle size of the non-fibrous filler (D) is preferably 0.1 to 45 μm. It is more preferably 0.2 to 30 μm, even more preferably 0.3 to 20 μm, and even more preferably 0.5 to 10 μm. Having a D50 average particle size of 0.1 μm or more suppresses aggregation of the (D) components, prevents them from becoming foreign matter within the resin layer (i), and prevents a decrease in mechanical properties. Furthermore, having a D50 average particle size of 45 μm or less prevents the spacing between the (D) components from becoming too narrow, suppressing the propagation of cracks at the interface when stress is generated. Additionally, heat resistance during the soldering process can be maintained.

[0046] The content of the non-fibrous filler (D) is preferably 1 to 60 parts by mass relative to 100 parts by mass of the polystyrene-based polymer (A) having a syndiotactic structure. It is more preferably 3 to 50 parts by mass, and even more preferably 5 to 40 parts by mass. When it is 1 part by mass or more, the effects of the (D) component can be exhibited. Furthermore, by setting it to 60 parts by mass or less, the smoothness of the sheet or the like is improved, film thickness control is facilitated, and aggregation of the (D) components within the resin layer (i) can be suppressed, thereby suppressing deterioration of mechanical properties.

[0047] The above does not apply to hollow amorphous silica and fused silica. The use of hollow silica is expected to further reduce the dielectric constant. When hollow silica is used, the film thickness is preferably in the range of 0.5 to 2.0 μm, more preferably 0.5 to 1.5 μm, and even more preferably 0.5 to 1.2 μm. If the film thickness is too thin, the silica may crack during screw mixing in a twin-screw kneader, making it impossible to maintain its hollow shape. If the film thickness is too thick, the volume fraction of hollow spaces decreases, and the dielectric constant-lowering effect may not be achieved. The D50 average particle size of the hollow silica is preferably in the range of 3 to 45 μm. If the particle size is less than 3 μm, the dielectric constant-lowering effect cannot be expected, and if the particle size exceeds 45 μm, the mechanical properties of the sheet, etc., are reduced.

[0048] The non-fibrous filler (D) may be either surface-treated or unsurface-treated. The surface treatment agent is not limited as long as it is a known agent, but by subjecting it to hydrophobic treatment with a silane-based or titanate-based coupling agent, the dispersion state in the styrene polymer (A) having a syndiotactic structure can be improved and the generation of aggregates in the resin layer (i) can be suppressed.

[0049] There are no particular restrictions on the polymer used as the organic spherical, granular, or plate-like filler, but taking into account the processing temperature of the styrene-based resin (A) having a syndiotactic structure, if the resin is a crystalline resin, it is preferably one having a melting point of more than 280°C, more preferably more than 300°C. Also, if the resin is amorphous, it is preferably one having a glass transition temperature of more than 150°C, more preferably more than 180°C. By setting the melting point and glass transition temperature within the above ranges, the shape of the filler can be maintained during processing into a sheet, etc., and the effect of suppressing the linear expansion coefficient of the resin layer (i) can be exerted.

[0050] <Antioxidant (E)> From the viewpoint of processability, the resin layer (i) of the present invention may contain the following antioxidant (E) (hereinafter also referred to as component (E)). The antioxidant (E) in the present invention may be either a primary antioxidant that prevents oxidation by capturing generated radicals, or a secondary antioxidant that prevents oxidation by decomposing generated peroxides. Examples of primary antioxidants include phenolic antioxidants and amine-based antioxidants, while examples of secondary antioxidants include phosphorus-based antioxidants and sulfur-based antioxidants. The incorporation of these antioxidants alone or in combination can suppress the reduction in molecular weight of component (A) or (B) during the production of the SPS resin composition and can suppress the generation of gas from component (A) or (B) during the hot-pressing step in producing the resin layer (i).

[0051] Specific examples of the phenolic antioxidant include monophenolic antioxidants such as 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2-t-butyl-4-methoxyphenol, 3-t-butyl-4-methoxyphenol, 2,6-di-t-butyl-4-[4,6-bis(octylthio)-1,3,5-triazin-2-ylamino]phenol, and n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Further examples include bisphenol-based antioxidants such as 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine, N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide], and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane. Further examples include polymeric phenolic antioxidants such as 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-sec-triazine-2,4,6-(1H,3H,5H)trione, and d-α-tocophenol.

[0052] Specific examples of amine-based antioxidants include alkyl-substituted diphenylamines.

[0053] Specific examples of phosphorus-based antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylidene-bis(3-methyl-6-t-butylphenylditridecyl)phosphite, octadecyl phosphite, tris(nonylphenyl)phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10- Examples thereof include dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, tris(2,4-di-t-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,4-di-t-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,6-di-t-butyl-4-methylphenyl)phosphite, and 2,2'-methylenebis(4,6-di-t-butylphenyl)octyl phosphite.

[0054] Specific examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, pentaerythritol tetrakis(3-laurylthiopropionate), and 2-mercaptobenzimidazole.

[0055] The antioxidant is preferably a primary antioxidant from the viewpoint of improving the heat resistance of the resin layer (i) and suppressing thermal degradation during processing, and among these, phenolic antioxidants are particularly preferred. The antioxidant preferably has a thermal decomposition temperature of 250°C or higher. A higher thermal decomposition temperature increases the effect of improving the breakdown voltage at high temperatures. If the thermal decomposition temperature is too low, the antioxidant itself may thermally decompose during melt extrusion, which tends to cause problems such as contamination of the process and yellowing of the polymer, which is undesirable. From this viewpoint, the thermal decomposition temperature of the antioxidant is more preferably 280°C or higher, even more preferably 300°C or higher, and particularly preferably 320°C or higher. The antioxidant in the present invention is preferably one that is less susceptible to thermal decomposition, and a higher thermal decomposition temperature is preferable, but in reality, the upper limit is approximately 500°C or lower.

[0056] The melting point of the antioxidant is preferably 90°C or higher. If the melting point is too low, the antioxidant melts faster than the polymer during melt extrusion, which tends to cause the polymer to slip at the screw feed section of the extruder. This leads to problems such as unstable polymer supply and uneven thickness of the sheet or the like. From this perspective, the melting point of the antioxidant is more preferably 120°C or higher, even more preferably 150°C or higher, and particularly preferably 200°C or higher. On the other hand, if the melting point of the antioxidant is too high, the antioxidant tends to melt less easily during melt extrusion, which tends to result in poor dispersion within the polymer. This leads to problems such as the antioxidant only exerting its effect locally. From this perspective, the melting point of the antioxidant is preferably 300°C or lower, more preferably 250°C or lower, even more preferably 220°C or lower, and particularly preferably 170°C or lower.

[0057] As the antioxidant, commercially available products can be used as they are. Preferred examples of commercially available products include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (manufactured by Ciba Specialty Chemicals, Inc.: trade name IRGANOX 1010), N,N'-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyl]hydrazine (manufactured by Ciba Specialty Chemicals, Inc.: trade name IRGANOX 1024), and N,N'-hexane-1,6-diylbis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide] (manufactured by Ciba Specialty Chemicals, Inc.: trade name IRGANOX 1098).

[0058] The content of the antioxidant is preferably 0.1% by mass or more and 8% by mass or less, based on the mass of the polystyrene-based resin composition. By incorporating the antioxidant in a content within the above range, the heat resistance and heat degradation resistance of the sheet can be improved. If the content of the antioxidant is too low, the effect of adding the antioxidant is insufficient, and the effect of improving the breakdown voltage tends to be reduced. From this perspective, the content of the antioxidant is more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and particularly preferably 0.5% by mass or more. On the other hand, if the content is too high, the antioxidant tends to aggregate easily in the resin layer (i), which tends to increase defects caused by the antioxidant, and such defects deteriorate the mechanical properties of the resin layer (i). From this perspective, the content of the antioxidant is more preferably 6% by mass or less, even more preferably 4% by mass or less, and particularly preferably 2% by mass or less.

[0059] The antioxidants may be used alone or in combination of two or more. When two or more types are used in combination, two or more primary antioxidants may be used, two or more secondary antioxidants may be used, or one or more primary antioxidants may be used in combination with one or more secondary antioxidants. For example, by using two antioxidants, a primary antioxidant and a secondary antioxidant in combination, it is expected that both primary and secondary oxidations can be prevented. In the present invention, the use of a primary antioxidant alone or two or more primary antioxidants is preferred from the viewpoint of achieving a higher effect of suppressing thermal degradation during processing. In particular, the use of a phenolic antioxidant alone or two or more phenolic antioxidants is preferred.

[0060] The resin layer (i) of the present invention may contain flame retardants, mold release agents, lubricants, viscosity reducers, curing agents, etc. other than those mentioned above. The flame retardants are not particularly limited, but suitable flame retardants include halogen-based flame retardants containing bromine, organic or inorganic phosphates, phosphate esters, and phosphorus copolymers. The flame retardants used may be liquid or solid, but from the viewpoint of long-term stability, it is preferable to use one that is solid at room temperature.

[0061] <Polystyrene-based resin composition> The polystyrene-based resin composition is a composition containing the above-mentioned component (A) as a main component, and optionally containing a predetermined amount of the component (C) and the component (D), and further optionally containing the component (B) or the component (E). The sheet of the present invention can be produced using the polystyrene-based resin composition. The polystyrene-based resin composition is preferably prepared by blending the above-mentioned components in predetermined amounts, kneading, and pelletizing them.

[0062] <Sheet / Film> The sheet or film of the present invention is an unstretched sheet containing the component (A) or a film obtained by biaxially stretching the unstretched sheet. Preferably, it is an unstretched sheet containing the polystyrene-based resin composition or a film obtained by biaxially stretching the unstretched sheet.

[0063] An unstretched sheet is not only not completely stretched, but may also have some residual strain. Specifically, the stretching ratio is preferably 1.3 times or less in both the direction parallel to the extrusion direction of the sheet (machine direction, MD) and the direction perpendicular to the extrusion direction of the sheet (transverse direction, TD).

[0064] The roll temperature when producing a sheet or the like is preferably 30 to 100°C, more preferably 40 to 95°C, and even more preferably 60 to 90°C. By setting the roll temperature within the above range, the roll winding properties and the surface roughness Rz of the sheet can be made uniform and small. If the roll temperature is 30°C or lower, condensation may occur on the roll surface, and water droplets may adhere to the sheet and be transferred as surface unevenness. If the roll temperature exceeds 100°C, the molten resin may stick to the roll, making it difficult to stretch and wind the sheet.

[0065] The pressure of the touch roll when producing a sheet or the like is preferably a linear pressure of 50 to 2000 N / cm. By using this pressure, the sheet thickness can be made uniform, and the surface roughness Rz can be made uniform and small. If the pressure is below 50 N / cm, the sheet thickness may become uneven, and the surface roughness Rz may become non-uniform and large. If the pressure exceeds 2000 N / cm, the sheet thickness may become non-uniform, residual stress may remain, and the sheet may become less rewound.

[0066] When producing a sheet or the like, it is preferable to apply pressure so that the sheet has a thickness of 50 to 2000 μm. If the thickness is less than 50 μm, it is difficult to apply pressure uniformly, which may result in a decrease in mechanical properties and non-uniform surface roughness Rz. If the thickness exceeds 2000 μm, it is difficult to apply sufficient pressure, which may result in non-uniform sheet thickness and surface roughness Rz.

[0067] The material of the two rolls used in producing a sheet or the like is not particularly limited and may be rubber, a metal roll, a resin, or the like. However, from the viewpoint of reducing the surface roughness Rz and applying pressure evenly, a metal roll is preferred.

[0068] When performing biaxial stretching, the stretching ratio, stretching temperature, and stretching speed are not particularly limited as long as the object of the present invention can be achieved, but are preferably within the following ranges. Stretching improves the heat-resistant dimensional stability of the sheet and the resin layer (i). Stretching methods include uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching, but simultaneous biaxial stretching or sequential biaxial stretching is preferred. Simultaneous biaxial stretching is even more preferred. If sequential biaxial stretching is performed instead of simultaneous biaxial stretching, the decrease in the thermal expansion coefficient in the first stretching direction may be small and the heat-resistant dimensional stability may be reduced; this tendency will become more pronounced unless the stretching speed is slowed. If uniaxial stretching is performed instead of biaxial stretching, the linear expansion coefficient in the non-stretched direction may not be reduced, and the heat-resistant dimensional stability may be reduced.

[0069] The stretching ratio is within a range of 2.0 times or more in both the MD and TD directions where breakage does not occur, and is preferably 2.0 to 5.0 times, and more preferably 2.3 to 4.0 times. It is preferable that the stretching ratios in the MD and TD directions are similar. Specifically, when the stretching ratio in the MD direction is PMD and the stretching ratio in the TD direction is PTD, "PTD - PMD" is preferably -0.6 to +0.6, and more preferably -0.3 to +0.3. The stretching ratio in the MD direction is based on the MD length immediately before stretching. The stretching ratio in the TD direction is based on the TD length immediately before stretching.

[0070] By adjusting the stretching ratio within the above range, the difference in the linear expansion coefficient between the MD and TD directions is reduced, and the degree of decrease in the linear expansion coefficient can be controlled. For example, increasing the stretching ratio in a given direction increases the degree of decrease in the linear expansion coefficient in that direction.

[0071] When TgP (°C) is defined as the glass transition temperature of the SPS resin constituting the sheet, the stretching temperature is preferably TgP°C or higher and TgP + 30°C or lower, and from the viewpoint of further improving heat-resistant dimensional stability, tensile strength, and tensile elongation, more preferably TgP°C or higher and TgP + 25°C or lower. If the stretching temperature is too low, stress concentration is likely to occur, making the sheet more likely to break, while if the stretching temperature is too high, crystallization of the sheet will be insufficient, the degree of reduction in the thermal expansion coefficient will be small, and dimensional stability under heat will be reduced.

[0072] The stretching temperature is the temperature of the sheet or the like during stretching. When the SPS resin is composed of two or more polymers, the TgP of the SPS resin can be confirmed from an endothermic peak (relaxation of the amorphous portion) observed by differential scanning calorimetry (DSC).

[0073] By adjusting the stretching temperature within the above range, the degree of decrease in the linear expansion coefficient can be controlled. For example, when the stretching temperature is lowered, the degree of decrease in the linear expansion coefficient increases.

[0074] The stretching speed is 50 to 10,000% / min in both the MD and TD directions, preferably 100 to 5,000% / min, and more preferably 100 to 3,000% / min. The stretching speed is calculated by {(dimension after stretching / dimension before stretching)-1}×100(%) / stretching time.

[0075] By adjusting the stretching speed within the above range, the degree of decrease in the linear expansion coefficient can be controlled. For example, increasing the stretching speed increases the degree of decrease in the linear expansion coefficient.

[0076] Heat treatment is a treatment to fix the orientation of polymer molecules by holding a stretched film at a temperature equal to or higher than the stretching temperature. When TgP (°C) is the glass transition temperature of the polymer component constituting the film and TmP (°C) is the melting point, the heat treatment temperature is TgP+70°C or higher and TmP or lower, and from the viewpoint of heat-resistant dimensional stability and heat shrinkage, it is preferably TgP+75°C or higher and TmP-20°C or lower. The heat treatment temperature is the atmospheric temperature at which the film is held. When the polymer component is composed of two or more polymers, the TmP of the polymer component is the sum of the values ​​obtained by multiplying the melting points of each polymer by the content ratio of the polymer.

[0077] The absolute value of the heat shrinkage can be controlled by adjusting the heat treatment temperature within the above range. For example, increasing the heat treatment temperature reduces the absolute value of the heat shrinkage.

[0078] The heat treatment may be a tension-type heat treatment in which the heat treatment is performed while maintaining the tension used during the biaxial stretching treatment, a relaxation-type heat treatment in which the tension is relaxed simultaneously with the biaxial stretching treatment, or a combined heat treatment in which the tension is maintained while a heat treatment (first heat treatment) is performed, and then the tension is relaxed while a heat treatment (second heat treatment) is performed. Relaxation-type heat treatment is preferred. When performing the heat treatment by any of the above methods, the heat treatment temperature is set within the above range.

[0079] When heat treatment is performed using the relaxation method or combined method described above, from the viewpoints of reducing the absolute value of the thermal shrinkage rate, heat-resistant dimensional stability, and film flatness, the relaxation ratio is preferably 0.8 to 1.00 times in both the MD and TD directions, more preferably 0.85 to 1.00 times, and most preferably 0.90 to 0.98 times. It is preferable that the relaxation ratios in the MD and TD directions are similar. Specifically, when the relaxation ratio in the MD direction is QMD and the relaxation ratio in the TD direction is QTD, "QTD-QMD" is preferably -0.1 to +0.1, more preferably -0.05 to +0.05, and most preferably -0.02 to +0.02. The relaxation ratio in the MD direction is based on the MD length immediately after stretching. The relaxation ratio in the TD direction is based on the TD length immediately after stretching.

[0080] The absolute value of the heat shrinkage can be controlled by adjusting the relaxation ratio within the above range. For example, when the relaxation ratio in a given direction is reduced, the absolute value of the heat shrinkage in that direction decreases by a larger amount.

[0081] The surface roughness (Rz) of the resin layer (i) of the present invention is preferably 0.1 μm or more and 6.0 μm or less. Since this improves adhesion to the adhesive layer (ii), it is more preferably 0.15 μm or more, and even more preferably 0.2 μm or more. Furthermore, since this reduces local thickness unevenness with the adhesive layer (ii) and prevents wrinkles from forming in the metal layer (iii), it is more preferably 5.0 μm or less, even more preferably 3.0 μm or less, even more preferably 2.5 μm or less, and particularly preferably 2.0 μm or less.

[0082] In order to set the surface roughness (Rz) of the resin layer (i) of the present invention within the above range, the surface roughness (Rz) of the sheet or film is preferably 0.1 μm or more and 6.0 μm or less. More preferably, it is 0.15 μm or more and 5.0 μm or less, and even more preferably, it is 0.2 μm or more and 3.0 μm or less. In a preferred embodiment, the resin layer (i) is made from a sheet or the like, and therefore, the surface roughness (Rz) of the sheet or the like is thought to affect the surface roughness (Rz) of the resin layer (i).

[0083] The relative dielectric constant (ε ｃ ) is preferably 3 or less at a temperature of 23°C, a relative humidity of 50%, and a frequency of 10 GHz. It is more preferably 2.8 or less, and even more preferably 2.7 or less. When the relative dielectric constant is 3 or less, the signal transmission speed is fast and the dielectric loss can be reduced. There is no particular restriction on the lower limit, but industrially it may be 1.0 or more, or even 2.0 or more.

[0084] The dielectric loss tangent (tan δ) of the resin layer (i) of the present invention is preferably 0.002 or less at a temperature of 23°C, a relative humidity of 50%, and a frequency of 10 GHz. It is more preferably 0.0015 or less, and even more preferably 0.001 or less. When the dielectric loss tangent is 0.002 or less, the dielectric loss is suppressed, and the performance as a circuit board at high frequencies is improved. The lower limit is not particularly limited, but it may be 0.0001 or more, or even 0.0002 or more.

[0085] When the relative dielectric constant and dielectric loss tangent of the resin layer (i) are within the above ranges, when the laminate is used for an electronic circuit board, the transmission loss of an electric signal flowing through the dielectric part of the laminate is reduced, and excellent properties can be exhibited.

[0086] The linear expansion coefficient of the resin layer (i) in the machine direction (MD) and the transverse direction (TD) must be 10 to 80 ppm / °C, respectively. It is preferably 15 ppm / °C or higher, more preferably 20 ppm / °C or higher, and preferably 75 ppm / °C or lower, more preferably 70 ppm / °C or lower. The MD / TD ratio must be 0.6 to 1.4. It is preferably 0.65 or higher, more preferably 0.7 or higher, and preferably 1.35 or lower, more preferably 1.3 or lower. The linear expansion coefficient of the resin layer (i) can be measured by removing only the resin layer (i) from the laminate. The method for removing the resin layer (i) is not particularly limited. For example, the metal layer (iii) may be removed by etching, and the adhesive layer (ii) may be removed by dissolving in a solvent or scraping off. Furthermore, when the longitudinal direction (MD) and transverse direction (TD) of the resin layer (i) taken out from the laminate are unknown, the linear expansion coefficients in one direction 1 and in a direction 2 perpendicular thereto are measured, and both MD / TD when direction 1 is MD and direction 2 is TD, and MD / TD when direction 1 is TD and direction 2 is MD are calculated, and it is sufficient if both are within the above-mentioned ranges.

[0087] In order to set the linear expansion coefficient of the resin layer (i) within the above range, the linear expansion coefficients in the machine direction (MD) and the transverse direction (TD) of the heat-treated sheet or film are each preferably 10 to 80 ppm / ° C., more preferably 15 to 75 ppm / ° C., and even more preferably 20 to 70 ppm / ° C. The MD / TD ratio is preferably 0.6 to 1.4, more preferably 0.65 to 1.35, and even more preferably 0.7 to 1.3.

[0088] By setting the linear expansion coefficient within the above range, the bonding property between the adhesive layer (ii) and the metal layer (iii) is improved in the hot pressing step when manufacturing the laminate, and wrinkles occurring in the laminate or the metal layer can be suppressed. Furthermore, by setting the MD / TD ratio within the above range, warping of the laminate and wrinkles on the surface of the laminate or the metal layer can be suppressed.

[0089] The resin layer (i) and heat-treated sheet of the present invention preferably have a dimensional change rate in each of the machine direction (MD) and the transverse direction (TD) when heat-treated at 150°C for 30 minutes of less than 1.0%, more preferably 0.6% or less, even more preferably 0.4% or less, still more preferably 0.3% or less, and most preferably 0.2% or less.

[0090] By ensuring that the heat shrinkage rate is within the above range, the adhesion between the adhesive layer (ii) and the metal layer (iii) is improved during the hot pressing step in producing the laminate, and wrinkles occurring in the laminate or the metal layer (iii) can be suppressed.

[0091] The thickness of the resin layer (i) of the present invention is preferably 10 μm to 2000 μm, more preferably 15 μm to 1000 μm, even more preferably 20 μm to 500 μm, and most preferably 25 μm to 300 μm. A thickness of 10 μm or more makes the resin layer (i) less likely to crack. Furthermore, a thickness of 2000 μm or less suppresses the occurrence of partial shrinkage (sink marks) and prevents unevenness in the thickness of the film.

[0092] In order to set the thickness of the resin layer (i) within the above range, the thickness of the sheet or the like is preferably 10 μm to 2000 μm, more preferably 15 μm to 1000 μm, even more preferably 20 μm to 500 μm, and most preferably 25 μm to 300 μm.

[0093] <Adhesive Layer (ii)> The adhesive layer (ii) in the laminate of the present invention is preferably a cured product of an adhesive composition containing an acid-modified styrene-based elastomer (a) and a curing agent (b), and preferably further contains an oligophenylene ether (c) and an acid-modified polyolefin (d) as necessary. The content of the acid-modified styrene-based elastomer (a) is preferably 50 parts by mass or more per 100 parts by mass of the solids content of the adhesive composition, and the content of the curing agent (b) is preferably 1 to 20 parts by mass per 100 parts by mass of the acid-modified styrene-based elastomer (a).

[0094] <Acid-Modified Styrenic Elastomer (a)> The acid-modified styrenic elastomer (a) (hereinafter also referred to as component (a)) is one of the main components of the adhesive composition, and is a component that imparts electrical properties in addition to adhesive properties and flexibility to the cured product. This acid-modified styrenic elastomer (a) is preferably a copolymer primarily composed of a block or random structure of a conjugated diene compound and an aromatic vinyl compound, or a hydrogenated product thereof, modified with an unsaturated carboxylic acid. Examples of aromatic vinyl compounds include styrene, t-butylstyrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylstyrene, N,N-diethyl-p-aminoethylstyrene, vinyltoluene, and p-tert-butylstyrene. Examples of conjugated diene compounds include butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene.

[0095] The acid-modified styrene elastomer (a) can be modified, for example, by copolymerizing an unsaturated carboxylic acid during polymerization of the styrene elastomer. Alternatively, the modification can be performed by heating and kneading the styrene elastomer and the unsaturated carboxylic acid in the presence of an organic peroxide. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, itaconic anhydride, and fumaric anhydride. The amount of modification with the unsaturated carboxylic acid is preferably 0.1 to 10% by mass.

[0096] The acid value of the acid-modified styrene-based elastomer (a) is preferably 0.1 to 25 mgKOH / g, more preferably 0.5 to 23 mgKOH / g. When this acid value is 0.1 mgKOH / g or more, the adhesive composition cures sufficiently, and good adhesion, heat resistance, and resin flow properties are obtained. On the other hand, when the acid value is 25 mgKOH / g or less, excellent adhesive strength and electrical properties are obtained.

[0097] The weight-average molecular weight of the acid-modified styrene-based elastomer (a) is preferably 10,000 to 500,000, more preferably 30,000 to 300,000, and even more preferably 50,000 to 200,000. A weight-average molecular weight within the range of 10,000 to 500,000 can exhibit excellent adhesiveness and electrical properties. In this specification, the weight-average molecular weight refers to the molecular weight measured by gel permeation chromatography (hereinafter also referred to as "GPC") converted into polystyrene.

[0098] Specific examples of the acid-modified styrene-based elastomer (a) include styrene-butadiene block copolymers, styrene-ethylene propylene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylenebutylene-styrene block copolymers, and styrene-ethylenepropylene-styrene block copolymers modified with unsaturated carboxylic acids. These acid-modified styrene-based elastomers (a) may be used alone or in combination of two or more. Among these copolymers, styrene-ethylenebutylene-styrene block copolymers and styrene-ethylenepropylene-styrene block copolymers are preferred from the viewpoints of adhesiveness and electrical properties. Furthermore, the mass ratio of styrene / ethylenebutylene in the styrene-ethylenebutylene-styrene block copolymer and the mass ratio of styrene / ethylenepropylene in the styrene-ethylenepropylene-styrene block copolymer are preferably 10 / 90 to 50 / 50, and more preferably 20 / 80 to 40 / 60. When the mass ratios are within these ranges, adhesive compositions with excellent adhesive properties can be obtained.

[0099] The content of the acid-modified styrene-based elastomer (a) is preferably 50 parts by mass or more, and more preferably 60 parts by mass or more, per 100 parts by mass of the solid content of the adhesive composition. When the content of component (a) is 50 parts by mass or more, the flexibility of the adhesive layer (ii) is improved, and warping of the laminate can be suppressed. Furthermore, the content of the acid-modified styrene-based elastomer (a) is preferably 99 parts by mass or less, and more preferably 95 parts by mass or less, per 100 parts by mass of the solid content of the adhesive composition.

[0100] <Curing Agent (b)> The adhesive layer (ii) preferably contains a curing agent (b) (hereinafter also referred to as component (b)). The curing agent (b) reacts with the carboxyl group contained in the acid-modified styrene-based elastomer (a) to increase the crosslink density, improving the adhesion to the resin layer (i) and the solder heat resistance, and also functions as a stress relaxation layer between the resin layer (i) and the metal layer (iii), thereby improving the reliability of the adhesion.

[0101] The curing agent (b) is not particularly limited as long as it can react with a carboxy group, and examples thereof include epoxy resins, maleimide resins, oxazoline compounds, polyisocyanates, polycarbodiimide compounds, etc. Among these, epoxy resins, polyisocyanates, and polycarbodiimide compounds are preferred, and one type can be used alone or two or more types can be used in combination. When used in combination, the network becomes denser during crosslinking, improving solder heat resistance.

[0102] <Epoxy Resin> The epoxy resin used in the present invention is not particularly limited as long as it has an epoxy group in the molecule, but preferably has two or more epoxy groups in the molecule. Specific examples include, but are not limited to, aromatic epoxy resins such as biphenyl-type epoxy resins, naphthalene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, and novolac-type epoxy resins; alicyclic epoxy resins such as dicyclopentadiene-type epoxy resins; amino-group-containing epoxy resins such as tetraglycidyldiaminodiphenylmethane, triglycidyl paraaminophenol, tetraglycidyl bisaminomethylcyclohexanone, and N,N,N',N'-tetraglycidyl-m-xylenediamine; and aliphatic epoxy resins such as epoxy-modified polybutadiene. These can be used alone or in combination of two or more. Aromatic epoxy resins, alicyclic epoxy resins, and amino-group-containing epoxy resins are preferred because they improve solder heat resistance, and amino-group-containing epoxy resins are more preferred. As the aromatic epoxy resin, biphenyl type epoxy resin and novolac type epoxy resin are preferred, and novolac type epoxy resin is more preferred, and as the alicyclic epoxy resin, dicyclopentadiene type epoxy resin is preferred.

[0103] The epoxy equivalent of the epoxy resin used in the present invention is preferably 50 g / eq or more, more preferably 70 g / eq or more, and even more preferably 80 g / eq or more. It is also preferably 400 g / eq or less, more preferably 350 g / eq or less, and even more preferably 300 g / eq or less. By keeping it within the above range, excellent solder heat resistance can be achieved.

[0104] In the adhesive layer (ii) of the present invention, the content of the epoxy resin in the curing agent (b) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more, relative to 100 parts by mass of the acid-modified styrene-based elastomer. By setting the content at or above the lower limit, a sufficient curing effect can be obtained, and excellent adhesion and solder heat resistance can be exhibited. Furthermore, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. By setting the content at or below the upper limit, the low dielectric properties and insulating reliability of the adhesive composition can be improved. In other words, by setting the content within the above range, an adhesive composition having adhesion, solder heat resistance, and excellent low dielectric properties can be obtained.

[0105] <Polycarbodiimide> The polycarbodiimide used in the present invention is not particularly limited as long as it has a carbodiimide group in the molecule, and is preferably a polycarbodiimide having two or more carbodiimide groups in the molecule.

[0106] The polycarbodiimide may be any of an aromatic carbodiimide compound, an alicyclic carbodiimide compound, and an aliphatic carbodiimide compound, and these may be used alone or in combination of two or more. Examples of aromatic carbodiimide compounds include poly-m-phenylene carbodiimide, poly-p-phenylene carbodiimide, polytolylene carbodiimide, poly(diisopropylphenylene carbodiimide), poly(methyldiisopropylphenylene carbodiimide), and poly(4,4'-diphenylmethane carbodiimide). Examples of alicyclic carbodiimide compounds include poly-m-cyclohexyl carbodiimide, poly-p-cyclohexyl carbodiimide, poly(4,4'-dicyclohexylmethane carbodiimide), and poly(3,3'-dicyclohexylmethane carbodiimide). Examples of aliphatic carbodiimide compounds may be either linear or branched aliphatic carbodiimide compounds. Preferred are linear aliphatic carbodiimide compounds, specifically polymethylenecarbodiimide, polyethylenecarbodiimide, polypropylenecarbodiimide, polybutylenecarbodiimide, polypentamethylenecarbodiimide, polyhexamethylenecarbodiimide, etc. These can be used alone or in combination of two or more. Among them, aromatic carbodiimide compounds or alicyclic carbodiimide compounds are preferred.

[0107] <Polyisocyanate> The polyisocyanate used in the present invention is preferably a polyfunctional isocyanate compound having two or more isocyanate groups in one molecule. Compounds derived from polyfunctional isocyanate compounds can also be used.

[0108] The polyisocyanate may be any of an aromatic isocyanate compound, an alicyclic isocyanate compound, and an aliphatic isocyanate compound, which may be used alone or in combination of two or more. Among these, an aliphatic isocyanate compound is preferred, and an aliphatic diisocyanate compound is more preferred. Examples of aromatic isocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, 1,8-naphthalene diisocyanate, 3,3'-biphenyl diisocyanate, 4,4'-biphenyl diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-4,4'-diisocyanate, and 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, and these can be used alone or in combination of two or more. Among these, 3,3'-dimethyl-4,4'-biphenyl diisocyanate is preferred. Examples of the alicyclic isocyanate compound include isophorone diisocyanate, norbornene diisocyanate, 1,2-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, and dicyclohexylmethane-4,4'-diisocyanate, and these can be used alone or in combination of two or more. The aliphatic isocyanate compound can be either a linear or branched aliphatic isocyanate. Preferred are straight-chain aliphatic diisocyanate compounds, and specific examples include 1,3-propane diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,7-heptamethylene diisocyanate, 1,8-octamethylene diisocyanate, and 1,9-nonamethylene diisocyanate, which can be used alone or in combination of two or more. Of these, 1,6-hexamethylene diisocyanate is preferred.

[0109] The polyisocyanate may be an isocyanurate, adduct, biuret, uretdione, or allophanate of the isocyanate compound. The polyisocyanate may also be a blocked isocyanate in which the isocyanate group is blocked. These compounds may be used alone or in combination of two or more. Of these, the isocyanurate or biuret is preferred.

[0110] In the adhesive layer (ii) of the present invention, the content of polycarbodiimide and polyisocyanate in the curing agent (b) component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the curing agent (b) component. By setting the content at or above the lower limit, interaction with the substrate is exhibited, resulting in good adhesion. Furthermore, the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. By setting the content at or below the upper limit, excellent dielectric properties can be exhibited. In other words, by setting the content within the above range, an adhesive film having excellent low dielectric properties in addition to adhesion and solder heat resistance can be obtained.

[0111] <Oligophenylene ether (c)> The oligophenylene ether (c) (hereinafter also referred to as component (c)) used in the present invention is a compound having a repeating unit of a phenylene ether structure, and preferably a compound having a structural unit represented by the following general formula (1) and / or a structural unit represented by the following general formula (2) can be used.

[0112] In general formula (1), R １ , R ２ , R ３ , R ４are preferably each independently a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, or an optionally substituted alkoxy group. The "alkyl group" of the optionally substituted alkyl group is, for example, a linear or branched alkyl group having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms. More specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, etc., with a methyl group or an ethyl group being more preferred. The "alkenyl group" of the optionally substituted alkenyl group includes, for example, an ethenyl group, a 1-propenyl group, a 2-propenyl group, a 3-butenyl group, a pentenyl group, a hexenyl group, etc., with an ethenyl group or a 1-propenyl group being more preferred. Examples of the "alkynyl group" of the optionally substituted alkynyl group include an ethynyl group, a 1-propynyl group, a 2-propynyl (propargyl) group, a 3-butynyl group, a pentynyl group, and a hexynyl group, with an ethynyl group, a 1-propynyl group, or a 2-propynyl (propargyl) group being more preferred. Examples of the "aryl group" of the optionally substituted aryl group include a phenyl group and a naphthyl group, with a phenyl group being more preferred. Examples of the "aralkyl group" of the optionally substituted aralkyl group include a benzyl group, a phenethyl group, a 2-methylbenzyl group, a 4-methylbenzyl group, an α-methylbenzyl group, a 2-vinylphenethyl group, and a 4-vinylphenethyl group, with a benzyl group being more preferred. The "alkoxy group" of the optionally substituted alkoxy group is, for example, a linear or branched alkoxy group having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms. Examples include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, and a hexyloxy group, and a methoxy group or an ethoxy group is more preferred.When the above alkyl group, aryl group, alkenyl group, alkynyl group, aralkyl group, and alkoxy group are substituted, they may have one or more substituents. Examples of such substituents include halogen atoms (e.g., fluorine atom, chlorine atom, bromine atom), alkyl groups having 1 to 6 carbon atoms (e.g., methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group), aryl groups (e.g., phenyl group, naphthyl group), alkenyl groups (e.g., ethenyl group, 1-propenyl group, 2-propenyl group), alkynyl groups (e.g., ethynyl group, 1-propynyl group, 2-propynyl group), aralkyl groups (e.g., benzyl group, phenethyl group), and alkoxy groups (e.g., methoxy group, ethoxy group). Among these, R is particularly preferred. １ and R ４ is a methyl group, and R ２ and R ３ is preferably a hydrogen atom.

[0113] In general formula (2), R １１ , R １２ , R １３ , R １４ , R １５ , R １６ , R １７ , R １８ are preferably each independently a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, or an optionally substituted alkoxy group. The definitions of each substituent are as described above. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group, and a methyl group is preferred. Among these, R １３ , R １４ , R １７ and R １８ is a methyl group, and R １１ , R １２ , R １５ and R １６is preferably a hydrogen atom. Furthermore, -A- is preferably a linear, branched, or cyclic divalent hydrocarbon group having 20 or less carbon atoms, or an oxygen atom. The number of carbon atoms in A is more preferably 1 to 15, and even more preferably 2 to 10. Furthermore, examples of the divalent hydrocarbon group for A include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a cyclohexylene group, and a phenylene group, and of these, a phenylene group is preferred. An oxygen atom is particularly preferred.

[0114] The oligophenylene ether (c) may be a modified polyphenylene ether in which a part or all of it is functionalized with an ethylenically unsaturated group such as a methacrylic group or a vinylbenzyl group, an epoxy group, an amino group, a hydroxy group, a mercapto group, a carboxy group, or a silyl group. Furthermore, from the viewpoint of improving solder heat resistance, it is preferable that both ends have a hydroxy group, an epoxy group, or an ethylenically unsaturated group. Examples of the ethylenically unsaturated group include alkenyl groups such as ethenyl, allyl, methacrylic, propenyl, butenyl, hexenyl, and octenyl, cycloalkenyl groups such as cyclopentenyl and cyclohexenyl, and alkenylaryl groups such as vinylbenzyl and vinylnaphthyl. Furthermore, both ends may be the same functional group or different functional groups. From the viewpoint of precisely controlling the balance between a low dielectric loss tangent and a reduction in resin residue, it is preferable that both terminals are hydroxy groups, methacryl groups, or vinylbenzyl groups, and it is more preferable that both terminals are hydroxy groups, methacryl groups, or vinylbenzyl groups.

[0115] As the compound having a structural unit represented by general formula (1) or general formula (2), a compound represented by general formula (3) is particularly preferred. In general formula (3), n is preferably 2 or more, more preferably 3 or more, and is preferably 12 or less, more preferably 11 or less, and even more preferably 10 or less. m is preferably 2 or more, more preferably 3 or more, and is preferably 12 or less, more preferably 11 or less, and even more preferably 10 or less. -A- is the same as in general formula (2).

[0116] Furthermore, as the compound having a structural unit represented by general formula (1) or general formula (2), a compound represented by general formula (4) or general formula (5) is particularly preferred. In general formula (4), n is preferably 2 or more, more preferably 3 or more, and is preferably 12 or less, more preferably 11 or less, and even more preferably 10 or less. m is preferably 2 or more, more preferably 3 or more, and is preferably 12 or less, more preferably 11 or less, and even more preferably 10 or less. -A- is the same as in general formula (2). In general formula (5), n is preferably 2 or more, more preferably 3 or more, and is preferably 12 or less, more preferably 11 or less, and even more preferably 10 or less. m is preferably 2 or more, more preferably 3 or more, and is preferably 12 or less, more preferably 11 or less, and even more preferably 10 or less. -A- is the same as in general formula (2).

[0117] The number average molecular weight of the oligophenylene ether (c) is preferably 3,000 or less, more preferably 2,700 or less, and even more preferably 2,500 or less. The number average molecular weight of the oligophenylene ether is preferably 500 or more, and more preferably 700 or more. By setting the number average molecular weight of the oligophenylene ether to the lower limit or more, the flexibility of the resulting adhesive layer can be improved. On the other hand, by setting the number average molecular weight of the oligophenylene ether to the upper limit or less, the solubility in organic solvents can be improved.

[0118] The content of oligophenylene ether (c) is preferably 0.05 parts by mass or more per 100 parts by mass of component (a). More preferably, it is 1 part by mass or more, and even more preferably, it is 5 parts by mass or more. By making it equal to or greater than the lower limit, excellent solder heat resistance can be exhibited. Also, it is preferably 200 parts by mass or less. More preferably, it is 150 parts by mass or less, even more preferably, it is 100 parts by mass or less, and particularly preferably, it is 50 parts by mass or less. By making it equal to or less than the upper limit, excellent adhesion and solder heat resistance can be exhibited.

[0119] <Acid-Modified Polyolefin Resin (d)> The acid-modified polyolefin resin (d) (hereinafter also referred to as component (d)) used in the present invention can be used as a means for adjusting the elastic modulus (tackiness) of the adhesive layer (ii). By further adding the acid-modified polyolefin resin (d) to an adhesive composition comprising an acid-modified styrene-based elastomer (a), a curing agent (b), and an oligophenylene ether (c) to these, the elastic modulus of the adhesive layer (ii) can be adjusted, making it easier to laminate the adhesive layer (ii) on the resin layer (i) and / or the metal layer (iii), and reducing the tackiness.

[0120] The acid-modified polyolefin resin (d) used in the present invention is not limited, but is preferably one obtained by grafting at least one α,β-unsaturated carboxylic acid and its acid anhydride onto a polyolefin resin. Polyolefin resin refers to a polymer primarily composed of a hydrocarbon skeleton, such as a homopolymer of an olefin monomer, such as ethylene, propylene, butene, butadiene, or isoprene, or a copolymer with other monomers, or a hydrogenated or halogenated version of the resulting polymer. In other words, the acid-modified polyolefin resin (a) is preferably one obtained by grafting at least one α,β-unsaturated carboxylic acid and its acid anhydride onto at least one of polyethylene, polypropylene, and a propylene-α-olefin copolymer.

[0121] Propylene-α-olefin copolymers are copolymers of propylene as the main component with an α-olefin. As the α-olefin, for example, ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, etc. can be used alone or in combination. Among these α-olefins, ethylene and 1-butene are preferred. The ratio of the propylene component to the α-olefin component in the propylene-α-olefin copolymer is not limited, but the propylene component is preferably 50 mol% or more, and more preferably 70 mol% or more.

[0122] Examples of at least one α,β-unsaturated carboxylic acid and its acid anhydride include maleic acid, itaconic acid, citraconic acid, and their acid anhydrides. Among these, acid anhydrides are preferred, and maleic anhydride is more preferred. That is, specific examples of the acid-modified polyolefin resin (c) include maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, maleic anhydride-modified propylene-ethylene-butene copolymer, etc., and these maleic anhydride-modified polyolefins can be used alone or in combination of two or more.

[0123] From the viewpoint of solder heat resistance and adhesion to the resin layer (i) and the metal layer (iii), the acid value of the acid-modified polyolefin resin (d) is preferably 5 mgKOH / g or more, more preferably 6 mgKOH / g or more, even more preferably 7 mgKOH / g or more, and particularly preferably 10 mgKOH / g or more. By setting the acid value at or above the lower limit, the reactivity with the curing agent (b) is improved, and excellent adhesive strength can be exhibited. In addition, the crosslinking density is high, and excellent solder heat resistance is achieved. The upper limit is preferably 30 mgKOH / g or less, more preferably 28 mgKOH / g or less, and even more preferably 25 mgKOH / g or less. By setting the acid value at or below the upper limit, excellent adhesion can be achieved. In addition, the viscosity and stability of the solution are improved, and excellent pot life can be exhibited. Furthermore, production efficiency is improved.

[0124] The number average molecular weight (Mn) of the acid-modified polyolefin resin (d) is preferably in the range of 10,000 to 50,000. More preferably, it is in the range of 15,000 to 45,000, even more preferably in the range of 20,000 to 40,000, and particularly preferably in the range of 22,000 to 38,000. By setting it to be equal to or greater than the lower limit, the cohesive strength is improved and excellent adhesive properties can be exhibited. Furthermore, by setting it to be equal to or less than the upper limit, excellent flowability and operability can be achieved.

[0125] The acid-modified polyolefin resin (d) is preferably crystalline. The term "crystalline" as used herein refers to a resin that exhibits a clear melting peak during heating from -100°C to 250°C at a rate of 20°C / min using a differential scanning calorimeter (DSC).

[0126] The melting point (Tm) of the acid-modified polyolefin resin (d) is preferably in the range of 50°C to 120°C. More preferably, it is in the range of 60°C to 100°C, and most preferably, it is in the range of 70°C to 90°C. By setting it to be equal to or greater than the lower limit, the cohesive force derived from crystals becomes good, and excellent adhesive properties and solder heat resistance can be exhibited. Furthermore, by setting it to be equal to or less than the upper limit, excellent solution stability and fluidity are achieved, and operability during adhesion is improved.

[0127] The heat of fusion (ΔH) of the acid-modified polyolefin resin (d) is preferably in the range of 5 J / g to 60 J / g. It is more preferably in the range of 10 J / g to 50 J / g, and most preferably in the range of 20 J / g to 40 J / g. By making it equal to or greater than the lower limit, the cohesive force derived from crystals becomes good, and excellent adhesive properties and solder heat resistance can be exhibited. Furthermore, by making it equal to or less than the upper limit, excellent solution stability and fluidity are achieved, and operability during adhesion is improved.

[0128] The method for producing the acid-modified polyolefin resin (d) is not particularly limited, and examples thereof include a radical graft reaction (i.e., a reaction in which radical species are generated on a polymer that becomes a main chain, and an unsaturated carboxylic acid and an acid anhydride are graft-polymerized using the radical species as a polymerization initiation point).

[0129] The radical generator is not particularly limited, but is preferably an organic peroxide. Examples of the organic peroxide include, but are not particularly limited to, peroxides such as di-tert-butyl peroxyphthalate, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxy-2-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, and lauroyl peroxide; and azonitriles such as azobisisobutyronitrile and azobisisopropionitrile.

[0130] <Adhesive Composition> The adhesive composition used in the adhesive layer (ii) of the present invention is preferably a composition containing the above-mentioned components (a) and (b), and optionally the component (c) and / or the component (d). By containing these components, the adhesive composition exhibits excellent adhesion to both the resin layer (i) and the metal layer (iii), and can exhibit electrical properties (low dielectric properties) and solder heat resistance. In other words, after applying the adhesive composition to the resin layer (i) and / or the metal layer (iii) and curing, the adhesive layer (ii) can exhibit excellent low dielectric properties and solder heat resistance.

[0131] The adhesive composition of the present invention may further contain an organic solvent. The organic solvent used in the present invention is not particularly limited as long as it dissolves the acid-modified styrene-based elastomer (a), the curing agent (b), and the oligophenylene ether (c) or the acid-modified polyolefin resin (d). Specific examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; alcoholic solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone. ketone-based solvents, cellosolves such as methyl cellosolve and ethyl cellosolve, ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate and butyl formate, glycol ether-based solvents such as ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-iso-butyl ether, triethylene glycol mono-n-butyl ether and tetraethylene glycol mono-n-butyl ether, and the like, can be used alone or in combination of two or more thereof. Methylcyclohexane and toluene are particularly preferred from the viewpoint of working environment and drying properties.

[0132] The organic solvent is preferably in the range of 100 to 1,000 parts by mass, more preferably 200 to 900 parts by mass, and most preferably 300 to 800 parts by mass, per 100 parts by mass of the acid-modified styrene-based elastomer (a). By adjusting the amount to be equal to or greater than the lower limit, the liquid state and pot life are improved. Furthermore, by adjusting the amount to be equal to or less than the upper limit, it is advantageous in terms of production costs and transportation costs.

[0133] The adhesive layer (ii) according to the present invention has a relative dielectric constant (ε ｃ ) is preferably 3.0 or less, more preferably 2.6 or less, and even more preferably 2.3 or less. There is no particular lower limit, but in practice it is 2.0. In addition, the relative dielectric constant (ε ｃ ) is preferably 3.0 or less, more preferably 2.6 or less, and even more preferably 2.3 or less.

[0134] The adhesive layer (ii) according to the present invention preferably has a dielectric loss tangent (tan δ) of 0.02 or less at a frequency of 10 GHz. It is more preferably 0.01 or less, and even more preferably 0.008 or less. There is no particular lower limit, but in practice it is 0.0001. Furthermore, the dielectric loss tangent (tan δ) over the entire frequency range of 1 GHz to 60 GHz is preferably 0.02 or less, more preferably 0.01 or less, and even more preferably 0.008 or less.

[0135] In the present invention, the relative dielectric constant (ε ｃ The dielectric constant (ε ) and dielectric loss tangent (tanδ) can be measured as follows. That is, the adhesive composition is applied to a release substrate so that the thickness after drying is 25 μm, and dried at about 130° C. for about 5 minutes. Next, the adhesive composition is cured by heat treatment at about 180° C. for about 1 hour, and the cured adhesive composition layer (adhesive layer (ii)) is peeled from the release film. The dielectric constant (ε ) at a frequency of 10 GHz of the adhesive composition layer after peeling is measured. ｃ Specifically, the relative permittivity (ε ｃ ) and dielectric loss tangent (tan δ) can be calculated.

[0136] The dielectric constant and dielectric loss tangent of the adhesive layer (ii) may be measured by removing only the adhesive layer (ii) from the laminate. The method for removing the adhesive layer (ii) is not particularly limited. For example, the metal layer (iii) may be removed by etching, and the resin layer (i) may be dissolved and removed with a solvent or scraped off. The adhesive layer (ii) removed from the laminate may be subjected to a dynamic viscoelasticity test alone.

[0137] The storage modulus at room temperature of the adhesive composition layer (adhesive layer (ii)) cured under the above conditions was 0.5×10 ６ Pa or more, 1.5×10 ８ It is more preferable that the viscosity is 1×10 Pa or less, since it is easy to laminate the resin layer (i) and / or the metal layer (iii). ７ Pa or more, and more preferably 3×10 ７ Pa or more. More preferably, it is 1.2 × 10 ８ Pa or less, and more preferably 1×10 ８ The storage modulus is 0.5 × 10 ６ When the storage modulus is 1.5×10 Pa or more, the tackiness is not too strong, so that the resin layer (i) can be easily peeled off from the release paper, and the resin layer (i) and the metal layer (iii) can be easily bonded together. ８ If the adhesive layer (ii) is not too hard when the pressure is 0.05 Pa or less, the resin layer (i) and the metal layer (iii) are easily relaxed when they are bonded together, and warping of the laminate and wrinkles on the surface of the metal layer (iii), which is the outermost surface of the laminate, can be suppressed.

[0138] The adhesive composition of the present invention may further contain other components as needed, provided that the effects of the present invention are not impaired. Specific examples of such components include inorganic fillers, tackifiers, and silane coupling agents.

[0139] <Inorganic Filler> The adhesive composition of the present invention may contain an inorganic filler as needed, provided that the effects of the present invention are not impaired. By incorporating this component, the solder heat resistance of a laminate produced with the adhesive composition is improved. The inorganic filler is preferably a filler, and more preferably a silica filler (hereinafter simply referred to as silica). Adding silica is highly preferred because it improves solder heat resistance. Generally, hydrophobic silica and hydrophilic silica are known as silica. Examples of hydrophobic silica include silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc. Hydrophobic silica can impart moisture absorption resistance to the adhesive composition. Examples of hydrophilic silica include untreated silica having silanol groups or siloxanes on its surface.

[0140] The average particle size of the inorganic filler is preferably 0.01 to 10 μm, more preferably 0.02 to 5 μm, and even more preferably 0.1 to 1 μm. The average particle size (median size) can be measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer.

[0141] In the adhesive composition of the present invention, the content of the inorganic filler is preferably in the range of 2 to 50 parts by mass, more preferably in the range of 3 to 45 parts by mass, and even more preferably in the range of 5 to 40 parts by mass, per 100 parts by mass of the total of components (a) to (c). By ensuring that the content is within this range, the adhesive composition will have good adhesion, solder heat resistance, and electrical properties.

[0142] <Tackifier> The adhesive composition of the present invention may contain a tackifier as needed, as long as it does not impair the effects of the present invention. Examples of tackifiers include polyterpene resins, rosin-based resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins, and are used to improve adhesive strength. These may be used alone or in any combination of two or more. When a tackifier is added, it is preferably added in an amount of 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, and most preferably 10 to 100 parts by mass, per 100 parts by mass of the total of components (a) to (c). By adjusting the amount to be equal to or greater than the lower limit, the effects of the tackifier can be achieved. Furthermore, by adjusting the amount to be equal to or less than the upper limit, adhesion, solder heat resistance, electrical properties, etc. are not impaired.

[0143] <Silane Coupling Agent> The adhesive composition of the present invention may contain a silane coupling agent, if necessary, as long as it does not impair the effects of the present invention. The inclusion of a silane coupling agent is highly preferred because it improves adhesion to metals and solder heat resistance. Silane coupling agents are not particularly limited, but examples include those containing unsaturated groups, glycidyl groups, and amino groups. Among these, glycidyl group-containing silane coupling agents, such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, are more preferred from the perspective of solder heat resistance. When a silane coupling agent is included, its amount is preferably 0.5 to 20 parts by mass per 100 parts by mass of the total of components (a) to (c). By adding 0.5 parts by mass or more, excellent solder heat resistance is achieved. On the other hand, by adding 20 parts by mass or less, good solder heat resistance and adhesion are achieved.

[0144] <Adhesive Sheet> In the present invention, the adhesive sheet is a precursor for producing the adhesive layer (ii), and is obtained by applying an adhesive composition to a release substrate, drying it to partially harden it, and then laminating a release substrate on top of that. Specific configurations include a release substrate / adhesive layer / release substrate. Laminating the release substrate functions as a protective layer for the substrate or adhesive layer. Furthermore, by using a release substrate, the release substrate can be released from the adhesive sheet and the adhesive layer can be transferred to another substrate.

[0145] The adhesive sheet of the present invention can be obtained by applying the adhesive composition of the present invention to various laminates and drying them according to conventional methods. Furthermore, by attaching a release substrate to the adhesive layer after drying, the adhesive can be wound up without causing offset onto the substrate, resulting in excellent operability, and the adhesive layer is protected, resulting in excellent storage stability and ease of use. Furthermore, after application to a release substrate and drying, the adhesive layer itself can be transferred to another substrate by attaching another release substrate as needed.

[0146] The thickness of the adhesive sheet is preferably in the range of 5 to 200 μm, more preferably 8 to 150 μm, more preferably 10 to 100 μm, and most preferably 12 to 80 μm. If the thickness of the adhesive sheet is less than 5 μm, pinholes are likely to occur, and if the thickness is more than 200 μm, significant thickness unevenness may occur.

[0147] <Release Substrate> The release substrate is not particularly limited, but examples include paper such as fine paper, kraft paper, roll paper, and glassine paper, on both sides of which a coating layer of a filler such as clay, polyethylene, or polypropylene is provided, and each of these coating layers is further coated with a silicone-based, fluorine-based, or alkyd-based release agent. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer alone, and films such as polyethylene terephthalate coated with the above-mentioned release agent. Due to factors such as the release force between the release substrate and the adhesive layer and the adverse effect of silicone on electrical properties, it is preferable to use a polypropylene-sealed film on both sides of fine paper and then apply an alkyd-based release agent thereon, or a polyethylene terephthalate film on which an alkyd-based release agent is applied.

[0148] In the present invention, the method for coating the adhesive composition onto a substrate is not particularly limited, but examples include a comma coater and a reverse roll coater. Alternatively, if necessary, an adhesive layer can be applied directly or by transfer to rolled copper foil or polyimide film, which are components of printed wiring boards. The thickness of the adhesive layer after drying can be adjusted as needed, but is preferably in the range of 5 to 200 μm. If the adhesive film thickness is less than 5 μm, the adhesive strength is insufficient. If it exceeds 200 μm, drying is insufficient, resulting in a large amount of residual solvent, which can cause blisters during pressing in the production of printed wiring boards. The drying conditions are not particularly limited, but the residual solvent content after drying is preferably 1% by mass or less. If it exceeds 1% by mass, the residual solvent can foam during pressing of the printed wiring board, causing blisters.

[0149] <Metal layer (iii)> As the metal layer (iii), any conventionally known conductive material that can be used for a circuit board can be used. Examples of materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, nickel, and their alloys, plated products, and metals treated with other metals such as zinc or chromium compounds. Metal foil is preferred, and copper foil is more preferred. Copper foils are classified into electrolytic foils and rolled foils, and either type of copper foil can be used in the laminate for electronic circuit boards of the present invention.

[0150] The surface roughness (Rz) of the surface of the metal layer (iii) in contact with the adhesive layer (ii) is preferably in the range of 0.1 μm to 7.0 μm, more preferably 0.3 μm to 5.0 μm, even more preferably 0.5 μm to 3.0 μm, and most preferably 0.8 μm to 1.5 μm. By keeping the surface roughness within this range, both excellent adhesion and transmission loss can be achieved, and the laminate can be suitably used for electronic circuit boards.

[0151] The thickness of the metal layer (iii) is preferably 1 μm or more, preferably 3 μm or more, more preferably 10 μm or more. It is also preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less. By setting the thickness to 1 μm or more, sufficient electrical performance of the electronic circuit can be obtained, while by setting the thickness to 50 μm or less, processing efficiency during the production of the electronic circuit can be improved. The metal foil is usually provided in a roll form. The form of the metal foil used in producing the printed wiring board of the present invention is not particularly limited. When a ribbon-shaped metal foil is used, its length is not particularly limited. Its width is also not particularly limited, but is preferably about 250 to 500 cm.

[0152] <Laminate> The laminate of the present invention is a laminate in which a resin layer (i), an adhesive layer (ii), and a metal layer (iii) are laminated in this order. The peel strength between the resin layer (i) and the adhesive layer (ii) must be 0.3 kN / m or more. Since this improves the durability of the laminate, it is preferably 0.4 kN / m or more, and more preferably 0.5 kN / m or more. There is no particular upper limit, but for electronic circuit board applications, 2 kN / m or less is sufficient, and 1.5 kN / m or less is also acceptable.

[0153] The laminate of the present invention may comprise a resin layer (i), an adhesive layer (ii), and a metal layer (iii) laminated in this order. Another layer may be laminated between the resin layer (i) and the adhesive layer (ii), or another layer may be laminated between the adhesive layer (ii) and the metal layer (iii). Preferably, the laminate comprises the resin layer (i), the adhesive layer (ii), and the metal layer (iii) directly laminated to each other. Alternatively, the adhesive layer (ii) and the metal layer (iii) may be laminated on both sides of the resin layer (i) in this order (for example, a laminate of "metal layer (iii) / adhesive layer (ii) / resin layer (i) / adhesive layer (ii) / metal layer (iii)"). When the adhesive layer (ii) and the metal layer (iii) are laminated on both sides of the resin layer (i), the resin layer (i) is preferably the innermost layer. In the case of such a laminate on both sides, other layers may be laminated between the resin layer (i), the adhesive layer (ii) and / or the metal layer (iii), or the laminate may be one in which the resin layer (i), the adhesive layer (ii) and the metal layer (iii) are directly laminated.

[0154] This application claims the benefit of priority based on Japanese Patent Application No. 2023-184994, filed on October 27, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-184994, filed on October 27, 2023, are incorporated herein by reference.

[0155] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, parts and percentages are expressed by mass unless otherwise specified.

[0156] (1) Evaluation Method for Characteristics of Raw Materials The characteristics of the raw materials used in the examples were evaluated using the following 1 to 3. For other characteristics, the nominal values ​​listed in the catalog values ​​of the raw material manufacturers are listed.

[0157] 1. Acid Value The acid value (mg KOH / g) in the present invention is a value obtained by dissolving a resin sample in toluene and titrating it with a methanol solution of sodium methoxide using phenolphthalein as an indicator.

[0158] 2. Number Average Molecular Weight (Mn) The number average molecular weight in the present invention is a value measured by gel permeation chromatography (hereinafter referred to as GPC, standard substance: polystyrene resin, mobile phase: tetrahydrofuran, column: Shodex KF-802 + KF-804L + KF-806L, column temperature: 30°C, flow rate: 1.0 ml / min, detector: refractive index (RI) detector) manufactured by Shimadzu Corporation.

[0159] 3. Measurement of Melting Point (Tm), Heat of Fusion (ΔH), and Glass Transition Temperature (Tg) The melting point and heat of fusion in the present invention are values ​​measured using a differential scanning calorimeter (hereinafter referred to as DSC, manufactured by TA Instruments Japan, Q-2000) from the top temperature and area of ​​the melting peak when the sample is heated and melted at a rate of 20°C / min, cooled to form a resin, and then heated and melted again. The glass transition temperature was taken as the temperature at the start (rise) of the endothermic peak during the heating process.

[0160] (2) Raw materials used in examples and comparative examples [Adhesive layer (i)] <Styrene polymer (A) having a syndiotactic structure> A1: XAREC (registered trademark) 130ZC (manufactured by Idemitsu Kosan Co., Ltd., 100% syndiotactic polystyrene by mass, MFR = 15 g / 10 min, measurement temperature: 300°C, load: 1.2 kg, not modified with a compound having a polar group, melting point: 272°C, glass transition temperature: 97°C) A2: XAREC (registered trademark) 90ZC (manufactured by Idemitsu Kosan Co., Ltd., 100% syndiotactic polystyrene by mass, MFR = 9 g / 10 min, measurement temperature: 300°C, load: 1.2 kg, not modified with a compound having a polar group, melting point: 271°C, glass transition temperature: 96°C)

[0161] <Rubber-like elastic body (B)> B1: Tuftec (registered trademark) H1062 (manufactured by Asahi Kasei Corporation, styrene ratio = 18 mass%, MFR = 4.5 g / 10 min, measurement temperature: 230°C, load: 2.16 kg) B2: Tuftec (registered trademark) H1041 (manufactured by Asahi Kasei Corporation, styrene ratio = 30 mass%, MFR = 5.0 g / 10 min, measurement temperature: 230°C, load: 2.16 kg) B3: Tuftec (registered trademark) H1517 (manufactured by Asahi Kasei Corporation, styrene ratio = 43 mass%, MFR = 3.0 g / 10 min, measurement temperature: 230°C, load: 2.16 kg) B4: Tuftec (registered trademark) H1521 (manufactured by Asahi Kasei Corporation, styrene ratio = 18 mass%, MFR = 15.0 g / 10 min, measurement temperature: 230 ° C, load: 2.16 kg)

[0162] <Fibrous filler (C)> C1: HDT09100T (manufactured by Tochu Corporation, fiber diameter (diameter): 9 μm, D50 average fiber length: 100 μm, D-glass) C2: EPH80M-01N (manufactured by Nippon Electric Glass Co., Ltd., fiber diameter (diameter): 10 μm, D50 average fiber length: 80 μm, E-glass) C3: EFH30-01 (manufactured by Central Glass Fiber Co., Ltd., fiber diameter (diameter): 11 μm, D50 average fiber length: 30 μm, E-glass) C4: ECS301HP-3-H (manufactured by Chongqing International Composite Materials Co., Ltd., fiber diameter (diameter): 10 μm, D50 average fiber length: 3000 μm, E-glass) C5: ChopVantage HP-3610 (manufactured by Nippon Electric Glass Co., Ltd., fiber diameter (diameter): 10 μm, D50 average fiber length: 4500 μm, E-glass)

[0163] <Non-fibrous filler (D)> D1: Silica particles: FB-3SDC (manufactured by Denka Company, Ltd., D50 average particle size: 3.1 μm) D2: Silica particles: FB-7SDC (manufactured by Denka Company, Ltd., D50 average particle size: 5.4 μm) D3: Silica particles: SFP-130MC (manufactured by Denka Company, Ltd., D50 average particle size: 0.6 μm) D4: Hollow glass beads: iM-30k (manufactured by 3M Japan Co., Ltd., D50 average particle size: 17 μm) D5: Calcium carbonate: Whiten P-30 (Shiraishi Calcium Industry Co., Ltd., D50 average particle size: 4.8 μm) D6: Magnesia: RF-98 (manufactured by Ube Material Industries, Ltd., D50 average particle size: 50 μm)

[0164] <Antioxidants (E)> E1: ANOX20 (manufactured by BASF Japan Ltd., pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] E2: PEP-36 (manufactured by ADEKA Corporation, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane)

[0165] [Adhesive layer (ii)] <Acid-modified styrene-based elastomer (a)> a1: Tuftec (registered trademark) H1943 (manufactured by Asahi Kasei Corporation, styrene ratio = 20 mass%, MFR = 8.0 g / 10 min (measurement conditions: measurement temperature: 230°C, load: 2.16 kg), acid value = 10 mgKOH / g) a2: Tuftec (registered trademark) H1913 (manufactured by Asahi Kasei Corporation, styrene ratio = 30 mass%, MFR = 5.0 g / 10 min (measurement conditions: measurement temperature: 230°C, load: 2.16 kg), acid value = 10 mgKOH / g) a3: Tuftec (registered trademark) C5025 (manufactured by Asahi Kasei Corporation, styrene ratio = 12 mass%, MFR = 10.0 g / 10 min (measurement conditions: measurement temperature: 230 ° C, load: 2.16 kg), acid value = 4 mg KOH / g)

[0166] <Unmodified styrene-based elastomer (α)> α1: Tuftec (registered trademark) H1041 (manufactured by Asahi Kasei Corporation, styrene ratio = 30 mass%, MFR = 5.0 g / 10 min (measurement conditions: measurement temperature: 230°C, load: 2.16 kg), acid value = 0 mgKOH / g)

[0167] <Curing agent (b)> b1: cresol novolac type epoxy resin: JER-152 (manufactured by Mitsubishi Chemical Corporation, epoxy equivalent = 177 g / eq) b2: dicyclopentadiene type epoxy resin: HP-7200 (manufactured by DIC Corporation, epoxy equivalent = 259 g / eq) b3: polycarbodiimide resin: V-09GB (manufactured by Nisshinbo Chemical Inc., carbodiimide equivalent = 216 g / eq)

[0168] <Oligophenylene ether (c)> c1: Oligophenylene ether styrene-modified product: OPE-2St 1200 (manufactured by Mitsubishi Gas Chemical Company, Inc., a compound having a structure of general formula (4) in which Mn = 1000) c2: Oligophenylene ether styrene-modified product: OPE-2St 2200 (manufactured by Mitsubishi Gas Chemical Company, Inc., a compound having a structure of general formula (4) in which Mn = 2000) c3: Oligophenylene ether: PPO640 (manufactured by SABIC, a compound having a structure of general formula (3) in which Mn = 18000)

[0169] <Acid-Modified Polyolefin (d)> d1: Production Example 1 To a 1 L autoclave, 100 parts by mass of a propylene-butene copolymer (Mitsui Chemicals, Inc. "TAFMER (registered trademark) XM7080"), 150 parts by mass of toluene, 19 parts by mass of maleic anhydride, and 6 parts by mass of di-tert-butyl peroxide were added, and the mixture was heated to 140 ° C. and stirred for an additional 3 hours. Thereafter, the resulting reaction liquid was cooled and poured into a container containing a large amount of methyl ethyl ketone to precipitate a resin. Thereafter, the liquid containing the resin was centrifuged to separate and purify an acid-modified propylene-butene copolymer graft-polymerized with maleic anhydride, (poly)maleic anhydride, and low-molecular-weight substances. Thereafter, the mixture was dried under reduced pressure at 70 ° C. for 5 hours to obtain a maleic anhydride-modified propylene-butene copolymer (CO-1, acid value 19 mg KOH / g, number average molecular weight 25,000, Tm 80 ° C., ΔH 35 J / g).

[0170] d2: Production Example 2 A maleic anhydride-modified propylene-butene copolymer (CO-2, acid value 11 mgKOH / g, number average molecular weight 33,000, Tm 80°C, ΔH 25 J / g) was obtained in the same manner as in Production Example 1, except that the amount of maleic anhydride added was changed to 11 parts by mass.

[0171] d3: Production Example 3 A maleic anhydride-modified propylene-butene copolymer (CO-3, acid value 7 mgKOH / g, number average molecular weight 35,000, Tm 82°C, ΔH 25 J / g) was obtained in the same manner as in Production Example 1, except that the amount of maleic anhydride added was changed to 6 parts by mass.

[0172] [Metal layer (iii)] ・I: Low roughness copper foil manufactured by Fukuda Metal Foil and Powder Industries Co., Ltd., CF-T4X-SV18, thickness = 18 μm, Rz = 1.1 μm ・II: Low roughness copper foil manufactured by Fukuda Metal Foil and Powder Industries Co., Ltd., CF-T9DA-SV-18, thickness = 18 μm, Rz = 0.9 μm ・III: Copper foil Manufactured by Furukawa Electric Co., Ltd., DGTSEU2, thickness = 18 μm, Rz = 3.2 μm ・IV: Copper foil Manufactured by Furukawa Electric Co., Ltd., GTS-MP, thickness = 18 μm, Rz = 8.0 μm

[0173] <Method for producing polystyrene-based resin composition> A polystyrene-based resin composition (SPS resin composition) was produced to obtain a sheet or film that is a precursor of the resin layer (i) of the present invention. The composition was obtained by blending and kneading each component (A) including SPS with the above-mentioned components (B) to (E).

[0174] More specifically, (A) and (B) to (E) were compounded by feeding them into a 36 mmφ unidirectional twin-screw extruder (resin temperature: 300°C) from the main feeder or side feeder, respectively, and extruding them into four φ4 mm strands through a round die. The strands were then cooled and solidified in a water-cooled bath and cut to obtain cylindrical pellets of the SPS resin composition.

[0175] <Method for Producing Unstretched Film (Examples 1 to 30, Comparative Examples 1 to 10)> Pellets of the SPS resin composition obtained by the above-mentioned production method were placed in the hopper of a 20 mm diameter single-screw extruder (resin temperature: 300°C), remelted, and extruded into a sheet from a T-die. The extruded sheet was compressed and cooled between two rolls (temperature: 90°C), consisting of a metal touch roll and a take-up roll, and then wound up at a speed of 1 m / min onto an 80 mm diameter cardboard tube to obtain an unstretched SPS sheet with a thickness of 300 μm. The windability of the film was evaluated as follows: no sticking to the chill roll and no thickness unevenness on the sheet surface (◯); sticking to the roll or thickness unevenness on the sheet surface (△); no sticking to the roll but thickness unevenness or minor cracks on the sheet surface (△△); and film that could not be wound due to sticking to the roll or cracks on the sheet surface (×). Hereinafter, the direction parallel to the extrusion direction of the sheet is defined as MD, and the direction perpendicular to the extrusion direction is defined as TD.

[0176] Heat Treatment and Humidity Conditioning Process: Heat treatment of the resulting unstretched SPS sheet increases the crystallinity of component (A) contained in the SPS sheet and improves the solder heat resistance of the SPS sheet. The SPS sheet obtained by the above manufacturing method was sandwiched between a commercially available polyimide film (Ube Industries, Ltd., Upilex) and a silicone sheet (Chukoh Chemical Industries, Ltd., MSF-100, thickness: 100 μm) and compressed and heated using a hydraulic hand press (temperature: 200 °C, time: 30 min, pressure: 2.0 MPa). The resulting heat-treated SPS sheet (hereinafter referred to as the "heat-treated sheet") was subjected to humidity conditioning for 24 hours in an environment of 23 °C and 50% RH to eliminate the effects of humidity and obtain a sample with minimal variation due to external factors.

[0177] To confirm whether the crystallization of the heat-treated sheet and biaxially stretched film was complete, a differential scanning calorimeter (DSC7020, manufactured by Hitachi High-Tech Science Corporation) was used to perform evaluation in accordance with JIS K7121 (2012). More specifically, when 5 mg of the sheet molded product was packed into an aluminum pan and heated from room temperature at a rate of 20°C / min, it was confirmed that no exothermic peak was observed in the temperature range of 100 to 220°C, confirming that crystallization was complete due to the heat treatment during pressing.

[0178] Stretched Film Manufacturing Method (Examples 31-34, Comparative Examples 11-13) Components (A) to (E) were compounded into a 36 mm diameter, co-rotating twin-screw extruder (resin temperature: 300°C) by feeding them into the main or side feeder in the ratios (parts by weight) shown in the table. Strands were extruded through four 4 mm diameter circular dies. The strands were cooled and solidified in a water-cooled bath and cut into cylindrical pellets of SPS resin composition. The pellets were then remelted in the hopper of a 20 mm diameter single-screw extruder (resin temperature: 300°C), extruded through a T-die, cooled on a metal cooling roll (temperature: 30°C), and wound around an 80 mm diameter cardboard tube at a speed of 3 m / min to produce a 500 μm thick unstretched SPS sheet (hereinafter sometimes referred to as the precursor SPS sheet) that served as a precursor for the stretched film. Next, the unstretched sheet was subjected to the stretching and relaxation treatments shown in Production Examples A to G below to produce biaxially stretched films.

[0179] Production Example A (Example 31) An unstretched SPS sheet having a thickness of 500 μm was obtained and then subjected to simultaneous biaxial stretching (temperature: 110° C., stretching ratio: 3.3 × 3.4 (MD × TD), stretching speed: 500% / min), followed by relaxation heat treatment in a thermal drying oven (temperature: 230° C., relaxation ratio: 0.93 × 0.95 (MD × TD)) to obtain a biaxially stretched SPS film having a thickness of 50 μm.

[0180] Production Example B (Example 32) An unstretched SPS sheet having a thickness of 500 μm was obtained and then subjected to simultaneous biaxial stretching (temperature: 110° C., stretching ratio: 3.3 × 3.4 (MD × TD), stretching speed: 500% / min), followed by relaxation heat treatment in a thermal drying oven (temperature: 230° C., relaxation ratio: 0.93 × 0.95 (MD × TD)) to obtain a biaxially stretched SPS film having a thickness of 50 μm.

[0181] Production Example C (Example 33) An unstretched SPS sheet having a thickness of 500 μm was obtained and then subjected to simultaneous biaxial stretching (temperature: 110° C., stretch ratio: 3.3 × 3.4 (MD × TD), stretching rate: 500% / min), followed by relaxation heat treatment in a thermal drying oven (temperature: 230° C., relaxation ratio: 0.97 × 1.00 (MD × TD)) to obtain a biaxially stretched SPS film having a thickness of 50 μm.

[0182] Production Example D (Example 34) After obtaining an unstretched SPS sheet having a thickness of 500 μm, the sheet was subjected to sequential biaxial stretching (temperature: 90° C., stretching ratio: 3.3 × 3.3 (MD × TD), stretching speed: 100% / min), followed by relaxation heat treatment in a thermal drying oven (temperature: 230° C., relaxation ratio: 1.00 × 0.95 (MD × TD)) to obtain a biaxially stretched SPS film having a thickness of 50 μm.

[0183] Production Example E (Comparative Example 11) An unstretched SPS sheet having a thickness of 500 μm was obtained and then subjected to simultaneous biaxial stretching (temperature: 135° C., stretching ratio: 3.3 × 3.4 (MD × TD), stretching speed: 500% / min), followed by relaxation heat treatment in a thermal drying oven (temperature: 230° C., relaxation ratio: 0.93 × 0.95 (MD × TD)) to obtain a biaxially stretched SPS film having a thickness of 50 μm.

[0184] Production Example F (Comparative Example 12) An unstretched SPS sheet having a thickness of 500 μm was obtained and then uniaxially stretched (temperature: 110°C, stretch ratio: 4.0 × 1.0 (MD × TD), stretching speed: 500% / min), followed by relaxation heat treatment in a thermal drying oven (temperature: 230°C, relaxation ratio: 0.97 × 1.00 (MD × TD)) to obtain a biaxially stretched SPS film having a thickness of 50 μm.

[0185] Production Example G (Comparative Example 13) An unstretched SPS sheet having a thickness of 500 μm was obtained and then sequentially biaxially stretched (temperature: 110° C., stretch ratio: 3.3 × 3.3 (MD × TD), stretching speed: 500% / min), followed by relaxation heat treatment in a thermal drying oven (temperature: 230° C., relaxation ratio: 0.97 × 1.00 (MD × TD)) to obtain a biaxially stretched SPS film having a thickness of 50 μm.

[0186] <Method for producing adhesive composition> An adhesive composition for use in the adhesive layer (ii) of the present invention was produced. The various components described above, namely, the styrene-based elastomer (a) and the curing agent (b), or the oligophenylene ether (c) and the acid-modified olefin (d), were blended and mixed to obtain a composition. More specifically, the compounds (a) to (d) and a methyl ethyl ketone / toluene ratio of 80 / 20 (vol%) were adjusted to 488 parts by mass (20 mass% solids concentration), and the resulting mixture was coated with a varnish and dried to produce the composition.

[0187] <Method of manufacturing adhesive sheet and lamination> A varnish made from the adhesive composition was applied to a 50 μm-thick release PET film using an applicator to a thickness of 25 μm (Examples 1 to 30, Comparative Examples 1 to 10) or 7.5 μm (Examples 31 to 34, Comparative Examples 11 to 13), and then cured in a hot air circulation dryer at a temperature of 130°C for 5 minutes. The adhesive sheet thus obtained was used to laminate onto an SPS resin sheet or film, and after peeling off the release PET film, copper foil was used as the metal layer (iii) and laminated onto the adhesive sheet.

[0188] <Hot Press Conditions for Laminate> A laminate was produced using the adhesive sheet and heat-treated sheet obtained by the above-mentioned manufacturing method. Specifically, a metal layer (copper foil layer) / adhesive sheet / heat-treated sheet / adhesive sheet / metal layer (copper foil layer) were laminated in this order, sandwiched between commercially available polyimide films (Ube Industries, Ltd., Upilex), then further sandwiched between silicone sheets (Chukoh Chemical Industries, Ltd., MSF-100, thickness: 100 μm), and placed between 2 mm thick SUS plates. Compression heating (curing) was carried out using a hydraulic hand press (temperature: 180 ° C, time: 1 hour, under vacuum conditions, pressure: 2.0 MPa). The resulting laminate was subjected to humidity conditioning treatment for 24 hours in an environment of 23 ° C x 50% RH to remove the influence of humidity and obtain a sample with little variation due to external factors.

[0189] In the following paragraphs, the SPS resin sheet or film used for the resin layer (i) was subjected to physical property evaluations 1 to 5, the adhesive sheet was subjected to physical property evaluation 6, and the laminate was subjected to physical property evaluations 7 to 10. Because the physical properties of the SPS resin sheet or film and the resin layer (i) are the same, the resin layer (i) alone may be removed from the laminate and the physical properties of the resin layer (i) evaluated. Furthermore, because the physical properties of the cured adhesive sheet (adhesive composition) and the adhesive layer (ii) are the same, the adhesive layer (ii) alone may be removed from the laminate and the physical properties of the adhesive layer (ii) evaluated. Furthermore, the metal layer (iii) may be removed from the laminate and measured.

[0190] <Evaluation Method> [Evaluation of Heat-Treated Sheet / Stretched Film] 1. Dielectric Properties The heat-treated sheet or stretched film was cut to prepare strip-shaped test pieces of 3 mm in MD and 80 mm in TD. The dielectric properties (relative dielectric constant: Dk(ε)) of the test pieces at a frequency of 10 GHz were measured under a test environment of 23°C temperature and 50% relative humidity. ｃ The dielectric loss tangent (Df (tan δ) / dielectric loss tangent: Df (tan δ)) was measured five times in total, and the average value was calculated (in accordance with JIS C2565-1992). As the measuring equipment, a network analyzer MS46122B manufactured by Anritsu Corporation and a cavity resonator manufactured by AET Corporation were used.

[0191] 2. Coefficient of Linear Expansion (CTE) The heat-treated sheet or stretched film was cut to prepare rectangular test pieces measuring 3 mm in width and 25 mm in length in the MD direction (test piece with the longitudinal direction being the MD direction) and the TD direction (test piece with the longitudinal direction being the TD direction). The linear expansion coefficient of each test piece in the MD and TD directions was measured five times, and the average value was calculated (in accordance with JIS K7197-2012). The measurement was performed using a TMA7100 manufactured by Hitachi High-Tech Science Corporation under a load of 2 gf / mm. The measurement results were read in a temperature range of 23 ° C to 80 ° C, and a linear expansion coefficient of 10 ppm or more and 80 ppm or less was considered to be acceptable.

[0192] 3. Solder Heat Resistance Test The heat-treated sheet or stretched film was cut to prepare test pieces measuring 50 mm in MD and 50 mm in TD. The test pieces were then floated in a solder bath heated to 260°C for 120 seconds, and the appearance was visually observed. A test piece showing no deformation or swelling in appearance was rated as ⊚ (◎), a test piece showing no significant deformation or swelling in appearance was rated as pass (◯), a test piece showing partial wrinkles was rated as pass (△), and a test piece showing significant deformation or swelling in appearance was rated as fail (×).

[0193] 4. Surface Roughness (Rz) A sheet or stretched film before heat treatment was cut to prepare a test piece of 100 mm in MD x 100 mm in TD. Then, using a surface roughness measuring instrument (SJ-310) in an atmosphere of room temperature: 25°C x humidity: 50% RH, the ten-point average roughness Rz of the touch roll surface was measured five times in each of the MD and TD directions, and the average value of a total of 10 points was calculated.

[0194] 5. Dimensional Change Rate The heat-treated sheet or stretched film was cut to prepare a rectangular test piece measuring 180 mm in the MD direction and 130 mm in the TD direction. Straight lines were drawn on the surface of the test piece to form a rectangle measuring 120 mm x 70 mm (MD x TD), parallel to the MD and TD directions, and intersecting at the midpoint. The lengths of the straight lines in the MD and TD directions of the test piece were measured. The test piece was then placed in a hot air circulating oven set to a 150°C atmosphere, suspended with one corner supported, for 30 minutes, and then removed from the oven and allowed to cool for 24 hours in an environment of 23°C and 50% RH to remove the influence of moisture content. The straight line lengths in the MD and TD directions were then measured, and the change from the length measured before the 150°C / 30-minute test was determined. The heat shrinkage rate was calculated as the ratio of the change to the respective lengths before the test. A positive value for the heat shrinkage rate indicates shrinkage. If the absolute value of the thermal shrinkage rate was 0.4% or less, it was judged as pass (◯), and if it exceeded 0.4%, it was judged as fail (×).

[0195] [Evaluation of Adhesive Sheets] 6. Dynamic Viscoelasticity Test (Storage Modulus) The adhesive composition described below was applied to a Teflon (registered trademark) sheet using an applicator to a dry thickness of 15 to 25 μm, and then dried at 130°C for 5 minutes. The adhesive film (B-stage product) obtained in this manner was further dried at 180°C for 1 hour. The resulting adhesive sheet was peeled off from the Teflon (registered trademark) sheet, and a dynamic viscoelasticity test was performed on the adhesive sheet alone in an atmosphere of temperature: 25°C / relative humidity: 50% RH. The DVA-225 manufactured by IT Measurement & Control Co., Ltd. was used. Using a test piece with a width of 4 mm and a length of 15 mm, the temperature was raised from -50°C to 300°C at a heating rate of 4°C / min, and viscoelasticity was measured at a vibration frequency of 10 GHz. The storage modulus was calculated at room temperature from the obtained viscoelasticity curve. In the table, the storage modulus is shown as elastic modulus.

[0196] [Evaluation of Laminate (Resin Layer (i) / Adhesive Layer (ii) / Metal Layer (iii))] Measurements of the following "7. Sheet Lamination Properties" to "10. Transmission Loss" were carried out by preparing a five-layer laminate sample of metal layer (iii) / adhesive layer (ii) / resin layer (i) / adhesive layer (ii) / metal layer (iii).

[0197] 7. Sheet Lamination Properties: A laminate was produced by laminating an adhesive film (B-stage product) obtained in the same manner as described above in the following order: 18 μm thick rolled copper foil (I-IV) / adhesive sheet / heat-treated sheet / adhesive sheet / 18 μm thick rolled copper foil (I-IV) and laminating the layers together. The lamination was performed by pressing the roughened surface of the rolled copper foil in contact with the adhesive layer at 180°C for 60 minutes under a pressure of 2.0 MPa under vacuum conditions. The appearance of the resulting laminate was evaluated. A rating of "○" was given for an appearance without wrinkles or streaks, and a rating of "△" was given for an appearance with wrinkles or streaks.

[0198] 8. Peel Strength (Adhesion) A laminate sample was prepared in the same manner as above. The peel strength (peel strength) was measured by subjecting the laminate sample to a tensile test at a tensile speed of 50 mm / min in an atmosphere of temperature: 23°C / relative humidity: 50% RH, and measuring the peel strength at the interface between the resin layer (i) and the adhesive layer (ii). This test indicates the adhesive strength at room temperature.

[0199] 9. Solder Heat Resistance A laminate sample was prepared in the same manner as above, and a sample piece (cut from the laminate) measuring 50 mm in MD and 50 mm in TD was subjected to aging treatment for two days under an environment of 23°C temperature and 50% RH relative humidity. The laminate was then immersed in a solder bath heated to 260°C for 120 seconds, and visually inspected for the degree of deformation and appearance abnormalities such as swelling. A sample showing no deformation or appearance swelling was rated as ⊚ (◎), a sample showing no significant deformation or appearance swelling was rated as pass (◯), a sample showing partial wrinkles was rated as pass (△), and a sample showing significant deformation or appearance abnormalities such as swelling was rated as fail (×).

[0200] 10. Transmission Loss A laminate sample was prepared using the same method as above, and the transmission loss was evaluated using a vector network analyzer (manufactured by Anritsu Corporation). A microstrip line with an impedance of 50 Ω was prepared on one side of the metal layer (iii), and the other side served as a ground layer. Both ends of the microstrip line and the ground layer were then connected to a measuring instrument, and the transmission amount of the incident wave to the microstrip line was measured up to a frequency of 40 GHz under conditions of a temperature of 23°C and a humidity of 50% RH, thereby calculating the transmission loss. The transmission loss was calculated using the transmission amount at a frequency of 40 GHz using the formula: Transmission Loss (dB / 100 mm) = Transmission Amount (dB) / Line Length (100 mm), and the absolute value was taken as the transmission loss. This allowed the transmission loss of the "resin layer (i) / adhesive layer (ii) / metal layer (iii)" laminate to be measured.

[0201] (Examples 1 to 30, Examples 31 to 34) In addition to Examples 1 to 30, laminates prepared in Production Examples A to D were used as Examples 31 to 34. In Examples 1 to 30, an unstretched sheet was used as the resin layer (i), and by containing the predetermined amounts of the (A) component, or the (A) to (C) components, the (D) component, and the (E) components, the required physical properties were satisfied, resulting in an excellent overall balance of performance. In addition, the biaxially oriented films described in Examples 31 to 34 prepared in Production Examples A to D had some issues with the appearance of the laminate, but were able to at least satisfy the required physical properties and exhibited an excellent balance of performance, second only to the unstretched sheet. Furthermore, the adhesive layer (ii) described in Examples 1 to 30 contained the predetermined amounts of components (a) and (b) or (c) to (d), and laminates with the unstretched sheet or biaxially oriented film exhibited excellent peel strength and solder heat resistance. Furthermore, the laminates in which the resin layer (i) and the metal layer (iii) are bonded together using the adhesive layer (ii) described in Examples 1 to 34 have excellent dielectric properties, and since the surface roughness Rz of the resin layer (i) and the metal layer (iii) can be reduced, the path of the electrical signal at the interface between each layer can be shortened, and therefore, they exhibit excellent transmission loss. The results of the examples are shown in Tables 1 to 5.

[0202]

[0203]

[0204]

[0205]

[0206]

[0207] (Comparative Examples 1 to 10, Comparative Examples 11 to 13) In Comparative Examples 1 to 10, an unstretched sheet was used as the resin layer (i). However, due to the excessive or insufficient addition of the (A) component, or the (A) to (C) components, the (D) component, and the (E) component, the required physical properties of the resin sheet were not met. Furthermore, the laminates made of the stretched films in Comparative Examples 11 to 13 produced in Production Examples E to G did not satisfy the CTE ratio in the MD / TD direction (MD / TD ratio) of the film used as the resin layer (i) or the dimensional change rate during heat treatment, and therefore did not satisfy the required physical properties of the laminate. Furthermore, adhesive layers (ii) containing predetermined amounts of components (a) and (b) or (c) to (d), and laminates obtained by bonding the resin layer (i) and the metal layer (iii) using adhesive layers (ii), did not satisfy the required properties in terms of peel strength, solder heat resistance, and transmission loss. The results are shown in Tables 6 and 7. In Tables 6 and 7, "-" indicates that the adhesive sheet was not sufficiently cured or the adhesive sheet itself was too soft and therefore could not be evaluated.

[0208]

[0209]

[0210] As is clear from the above explanation, according to the present invention, the electronic circuit board laminate described in the examples has excellent dielectric properties, linear expansion coefficient, and solder heat resistance, as well as peel strength and transmission loss, and is therefore expected to be used in high-frequency circuit boards. Specifically, it is expected that the sheet molded body of the present invention can be used in electronic components and antenna components for communication devices that require 5G.

Claims

1. A laminate in which a resin layer (i), an adhesive layer (ii), and a metal layer (iii) are laminated in this order, wherein the resin layer (i) contains a styrene-based polymer (A) having a syndiotactic structure, the resin layer (i) has a linear expansion coefficient in the longitudinal direction (MD) and transverse direction (TD) of 10 to 80 ppm / °C and an MD / TD ratio satisfies the range of 0.6 to 1.4, the interlayer peel strength between the resin layer (i) and the adhesive layer (ii) is 0.3 kN / m or more, and the absolute value of the transmission loss of the laminate at a frequency of 40 GHz is 5.0 dB / 100 mm or less.

2. The laminate according to claim 1, wherein the surface roughness Rz of the resin layer (i) is 0.1 μm or more and 6.0 μm or less.

3. The laminate according to claim 1, wherein the surface roughness Rz of the resin layer (i) is 0.1 μm or more and 3.0 μm or less.

4. The laminate according to claim 1 or 2, wherein the adhesive layer (ii) contains a styrene-based elastomer and a curing agent.

5. The laminate according to claim 1 or 2, wherein the surface roughness Rz of the metal layer (iii) is 0.1 μm or more and 7.0 μm or less.

6. The laminate according to claim 1 or 2, wherein the resin layer (i) further contains a fibrous filler (C).

7. The laminate according to claim 1 or 2, wherein the resin layer (i) further contains a non-fibrous filler (D).

8. The laminate according to claim 1 or 2, wherein the resin layer (i) further contains a fibrous filler (C) and a non-fibrous filler (D).

9. The laminate according to claim 1 or 2, wherein the resin layer (i) further contains a fibrous filler (C) and a non-fibrous filler (D), and contains 1 to 50 parts by mass of the fibrous filler (C) per 100 parts by mass of the styrene-based polymer (A) having a syndiotactic structure.

10. The laminate according to claim 1 or 2, which is used as an electronic circuit board.

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