Laminate

Abstract

To provide a laminate having smaller transfer loss in a high frequency band.SOLUTION: A laminate has a metal layer and a resin layer in contact with at least one surface of the metal layer, wherein a dielectric loss tangent at a temperature of the resin layer of 23°C and a frequency of 28 GHz is less than 0.002, and a contour line RSm of an interface between the metal layer and the resin layer in a cross section in a thickness direction of the laminate is 1.2 μm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a laminate.

Background Art

[0002] In the fifth-generation (5G) mobile communication system, which is regarded as the next-generation communication technology, higher frequency bands than ever are used. Therefore, for the film base material for a circuit board for a 5G mobile communication system, low dielectric tangent and low water absorption are required from the viewpoint of reducing transmission loss in a high-frequency band, and development using various materials is underway.

[0003] For example, Patent Document 1 describes a high-frequency circuit board comprising a laminate in which a thermoplastic liquid crystal polymer film is laminated on a metal foil having irregularities on its surface and having a surface roughness (Rz) and a ratio (Rz / S) of the surface roughness (Rz) to the interval (S) between the irregularities on the surface within a specific range.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For a laminate having a metal layer and a resin layer as described above, further reduction of transmission loss in a high-frequency band when used for a high-frequency circuit board is required. When the present inventor produced a laminate having a metal layer and a resin layer with reference to the film described in Patent Document 1, it was found that there is room for further improvement in the transmission loss of the laminate in a high-frequency band.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a laminate having smaller transmission loss in a high-frequency band.

Means for Solving the Problem

[0007] As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[0008] 〔1〕A laminate having a metal layer and a resin layer in contact with at least one surface of the metal layer, wherein the dielectric tangent of the resin layer at a temperature of 23 ° C and a frequency of 28 GHz is less than 0.002, and in a cross section along the thickness direction, the average length RSm of the roughness curve elements of the interface between the metal layer and the resin layer is 1.2 μm or less. 〔2〕The laminate according to 〔1〕, wherein the resin layer contains a liquid crystal polymer. 〔3〕The laminate according to 〔2〕, wherein the liquid crystal polymer contains two or more repeating units derived from dicarboxylic acids. 〔4〕The laminate according to 〔2〕 or 〔3〕, wherein the liquid crystal polymer has at least one selected from the group consisting of a repeating unit derived from 6-hydroxy-2-naphthoic acid, a repeating unit derived from an aromatic diol, a repeating unit derived from terephthalic acid, and a repeating unit derived from 2,6-naphthalenedicarboxylic acid. 〔5〕The laminate according to any one of 〔1〕 to 〔4〕, wherein the resin layer contains a polyolefin. 〔6〕The laminate according to 〔5〕, wherein the content of the polyolefin is 0.1 to 40% by mass based on the total mass of the resin layer. 〔7〕The laminate according to 〔5〕 or 〔6〕, wherein a dispersed phase containing the polyolefin is formed in the resin layer, and the average dispersed diameter of the dispersed phase in an observation image obtained by observing the cross section of the resin layer is 0.01 to 10 μm. 〔8〕The laminate according to any one of 〔1〕 to 〔7〕, wherein the resin layer has, in this order from the metal layer side, an adhesion resin layer and a layer containing a liquid crystal polymer. 〔9〕The laminate according to 〔8〕, wherein the thickness of the adhesion resin layer is 1 μm or less. The laminate according to [8] or [9], wherein the elastic modulus of the above-mentioned adhesion resin layer is 0.8 GPa or more. The laminate according to any one of [8] to

[10] , wherein the content of the solvent contained in the above-mentioned adhesion resin layer is 0 to 200 mass ppm with respect to the total mass of the above-mentioned adhesion resin layer. The laminate according to any one of [1] to

[11] , wherein the above-mentioned metal layer is a copper layer.

Advantages of the Invention

[0009] According to the present invention, a laminate with smaller transmission loss in a high-frequency band can be provided.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. Regarding the notation of groups (atomic groups) in this specification, unless contrary to the spirit of the present invention, notations without indicating substitution and unsubstitution include groups having no substituents as well as groups having substituents. For example, the "alkyl group" includes not only an alkyl group having no substituents (unsubstituted alkyl group) but also an alkyl group having substituents (substituted alkyl group). Further, the "organic group" in this specification means a group containing at least one carbon atom.

[0011] In this specification, when the resin layer or film is in a long shape, the width direction means the short-side direction and the TD (transverse direction) of the resin layer or film, and the length direction means the long-side direction and the MD (machine direction) of the resin layer or film. In this specification, each component may be used alone as one kind of substance corresponding to each component, or two or more kinds may be used. Here, when two or more kinds of substances are used for each component, the content of that component means the total content of two or more kinds of substances unless otherwise specified. In this specification, "~" is used to mean including the numerical values described before and after it as the lower limit value and the upper limit value. In this specification, the dielectric tangent of the resin layer or the resin contained in the resin layer measured under the conditions of a temperature of 23°C and a frequency of 28 GHz is also referred to as the "standard dielectric tangent". In this specification, "film width" means the distance between both ends in the width direction of a resin layer or film that is in a long shape.

[0012] [Laminate] The laminate according to the present invention has a metal layer and a resin layer in contact with at least one surface of the metal layer, the standard dielectric tangent of the resin layer is less than 0.002, and in a cross-section along the thickness direction of the laminate, the average length RSm of the roughness curve elements at the interface between the metal layer and the resin layer (hereinafter, also referred to as "RSm of the interface") is 1.2 μm or less. By defining the standard dielectric tangent of the resin layer included in the laminate and the roughness of the interface between the metal layer and the resin layer as described above, a laminate with smaller transmission loss in the high-frequency band can be obtained. In particular, the transmission loss of the laminate having a metal layer and a resin layer consists of the conductor loss of the metal layer and the dielectric loss of the resin layer. Since an electrical signal in the high-frequency band flows on the surface layer of the metal layer, it is considered that the transmission loss of the laminate in the high-frequency band is more suppressed because the RSm of the interface is within the above range. Hereinafter, when the transmission loss in the high-frequency band in the laminate having a metal layer and a resin layer is smaller, it is also described as "the effect of the present invention is more excellent". Hereinafter, the configuration of the laminate according to the present invention will be described in detail.

[0013] The laminate has at least one metal layer and at least one resin layer, and the metal layer is arranged to be in contact with the surface of the resin layer. The number of the metal layer and the resin layer included in the laminate is not limited, and the number of each layer may be only one or two or more. The laminate may have only one metal layer on one side of one resin layer, or may have two metal layers on both sides of one resin layer. The laminate preferably has at least a layer structure laminated in the order of a metal layer, a resin layer, and a metal layer.

[0014] The RSm of the interface in the laminate according to the present invention is 1.2 μm or less. The RSm of the interface of the laminate is preferably 0.9 μm or less, more preferably 0.6 μm or less, in terms of more excellent effects of the present invention. The lower limit is not particularly limited, but is, for example, 0.1 μm or more, and preferably 0.3 μm or more in terms of ensuring adhesion. In addition, when the laminate according to the present invention has two metal layers and there are two interfaces between the metal layer and the resin layer, it means that the RSm of at least one interface is 1.2 μm or less. When the laminate has two metal layers, it is preferable that the RSm of both interfaces is 1.2 μm or less, and more preferably that the RSm of both interfaces is within the above preferable range.

[0015] The RSm of the interface of the laminate is determined in accordance with JIS B0601:2001. Specifically, a cross-section in the thickness direction (lamination direction) of the laminate is observed using a scanning electron microscope (SEM) (magnification: 50,000 times), and the interface between the metal layer and the resin layer in the obtained observation image is traced over a measurement length of 2000 nm by image processing to measure the cross-sectional curve of the interface between the metal layer and the resin layer. Further, from the obtained cross-sectional curve, a roughness curve is obtained by a roughness curve filter with a cut-off value of 700 nm (high wavelength side) and a cut-off value of 10 nm (low wavelength side). This measurement of the roughness curve is performed for 10 SEM observation images with different cross-sectional positions, and the RSm of the interface is obtained by arithmetically averaging the lengths of the roughness curve elements at the reference length (= cut-off value on the high wavelength side).

[0016] 〔Metal layer〕 Examples of materials constituting the metal layer include metals used for electrical connection. Such metals include, for example, copper, gold, silver, nickel, aluminum, and alloys containing any of these metals. Examples of alloys include copper-zinc alloys, copper-nickel alloys, and zinc-nickel alloys. As the metal layer, a copper layer is preferable in terms of excellent conductivity and workability. The copper layer is a layer made of copper or a copper alloy containing 95% by mass or more of copper. Examples of the copper layer include rolled copper foil manufactured by a rolling method and electrolytic copper foil manufactured by an electrolytic method. The metal layer may be subjected to chemical treatment such as pickling.

[0017] When using a metal foil such as copper foil in the production of the laminate, the RSm of at least one surface of the metal foil is preferably 1.2 μm or less, more preferably 0.9 μm or less, and still more preferably 0.6 μm or less. The lower limit is not particularly limited, but is preferably 0.1 μm or more, and more preferably 0.3 μm or more. By using a metal foil having an RSm of at least one surface (the surface in contact with the resin layer) within the above range, the production of the laminate of the present invention in which the RSm of the interface is defined becomes easy. Examples of the metal foil having an RSm of the surface within the above range include unroughened copper foil, etc., which are available on the market. The RSm of the surface of the metal foil can be measured according to the method for measuring the RSm of the interface in the above laminate from the obtained cross-section after subjecting the metal foil to an embedding treatment of embedding it in a resin for observation and then cutting the embedded metal foil along the thickness direction.

[0018] The thickness of the metal layer is not particularly limited and is appropriately selected according to the use of the circuit board. However, in terms of wiring conductivity and economy, 4 to 100 μm is preferable, and 10 to 35 μm is more preferable.

[0019] 〔Resin layer〕 <Dielectric properties> The resin layer of the laminate of the present invention is a resin layer having a standard dielectric loss tangent of less than 0.002. The standard dielectric loss tangent of the resin layer is preferably 0.0015 or less, more preferably 0.001 or less. The lower limit is not particularly limited and may be 0.0001 or more. The relative dielectric constant of the resin layer varies depending on its use, but is preferably 2.0 to 4.0, more preferably 2.5 to 3.5. The dielectric properties including the standard dielectric loss tangent of the resin layer can be measured by the cavity resonator perturbation method. The specific measurement method of the dielectric properties of the resin layer is described in the Examples section below.

[0020] <Configuration of the resin layer> The configuration of the resin layer is not particularly limited as long as the dielectric loss tangent of the resin layer is less than 0.002. The resin layer may have only a polymer layer containing a polymer with a low standard dielectric loss tangent (preferably less than 0.002), or may have two or more layers including the above polymer layer. Among them, in terms of better adhesion to the metal layer, the resin layer preferably has a polymer layer containing a polymer with a low standard dielectric loss tangent (more preferably a liquid crystal polymer) and an adhesion resin layer.

[0021] The adhesion resin layer is preferably disposed on the surface of the resin layer in contact with the metal layer. That is, when the resin layer has an adhesion resin layer, it is preferably arranged in the order of the adhesion resin layer and the polymer layer from the metal layer side. For example, when two metal layers are disposed on both sides of the resin layer, it is preferably laminated in the order of the metal layer, the adhesion resin layer, the polymer layer, the adhesion resin layer, and the metal layer.

[0022] Hereinafter, the resin layer having a polymer layer and an adhesion resin layer will be described in detail. As described above, the resin layer may have only the polymer layer. That is, the polymer layer described below may be included in the laminate as the resin layer alone.

[0023] <Polymer layer> The polymer layer is a layer containing a polymer with a low standard dielectric loss tangent. The standard dielectric tangent of the polymer contained in the polymer layer is preferably less than 0.002, more preferably 0.0015 or less, and still more preferably 0.001 or less. The lower limit is not particularly limited and may be, for example, 0.0001 or more. The type of the polymer contained in the polymer layer is not particularly limited, and examples thereof include liquid crystal polymers, fluororesins, polyimides, and modified polyimides. Among them, liquid crystal polymers or fluororesins are preferable, and liquid crystal polymers are more preferable. Hereinafter, taking the polymer layer containing a liquid crystal polymer as a representative example, the configuration of the polymer layer will be described in more detail.

[0024] (Liquid crystal polymer) The liquid crystal polymer contained in the resin layer and the polymer layer is not particularly limited, and examples thereof include melt-moldable liquid crystal polymers. As the liquid crystal polymer, a thermotropic liquid crystal polymer is preferable. A thermotropic liquid crystal polymer means a polymer that exhibits liquid crystallinity in a molten state when heated in a predetermined temperature range. The chemical composition of the thermotropic liquid crystal polymer is not particularly limited as long as it is a liquid crystal polymer that can be melt-molded, and examples thereof include thermoplastic liquid crystal polyesters and thermoplastic polyester amides in which an amide bond is introduced into a thermoplastic liquid crystal polyester. As the liquid crystal polymer, for example, the thermoplastic liquid crystal polymers described in International Publication No. 2015 / 064437 and Japanese Patent Application Laid-Open No. 2019-116586 can be used.

[0025] More specific liquid crystal polymers include thermoplastic liquid crystal polyesters or thermoplastic liquid crystal polyester amides having repeating units derived from at least one selected from the group consisting of aromatic hydroxycarboxylic acids, aromatic or aliphatic diols, aromatic or aliphatic dicarboxylic acids, aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids.

[0026] Examples of the aromatic hydroxycarboxylic acid include parahydroxybenzoic acid, metahydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-(4-hydroxyphenyl)benzoic acid. These compounds may have substituents such as a halogen atom, a lower alkyl group, and a phenyl group. Among them, parahydroxybenzoic acid or 6-hydroxy-2-naphthoic acid is preferable. As the aromatic or aliphatic diol, an aromatic diol is preferable. Examples of the aromatic diol include hydroquinone, 4,4'-dihydroxybiphenyl, 3,3'-dimethyl-1,1'-biphenyl-4,4'-diol, and acylates thereof, and hydroquinone or 4,4'-dihydroxybiphenyl is preferable. As the aromatic or aliphatic dicarboxylic acid, an aromatic dicarboxylic acid is preferable. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, and terephthalic acid is preferable. Examples of the aromatic diamine, aromatic hydroxyamine, and aromatic aminocarboxylic acid include p-phenylenediamine, 4-aminophenol, and 4-aminobenzoic acid.

[0027] The liquid crystal polymer preferably contains a repeating unit derived from a dicarboxylic acid (aromatic or aliphatic dicarboxylic acid) among the above repeating units, and more preferably contains two or more repeating units derived from a dicarboxylic acid in terms of more excellent low dielectric property. In this case, as the dicarboxylic acid, the above aromatic dicarboxylic acid is preferable, and terephthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid is more preferable.

[0028] Further, the liquid crystal polymer preferably has at least one selected from the group consisting of repeating units represented by the following formulas (1) to (3). -O-Ar1-CO- (1) -CO-Ar2-CO- (2) -X-Ar3-Y- (3) In formula (1), Ar1 represents a phenylene group, a naphthylene group, or a biphenylylene group. In formula (2), Ar2 represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4). In formula (3), Ar3 represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), and X and Y each independently represent an oxygen atom or an imino group. -Ar4-Z-Ar5- (4) In formula (4), Ar4 and Ar5 each independently represent a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group. The above phenylene group, the above naphthylene group, and the above biphenylylene group may have a substituent selected from the group consisting of a halogen atom, an alkyl group, and an aryl group.

[0029] Among them, the liquid crystal polymer preferably has at least one selected from the group consisting of a repeating unit derived from the aromatic hydroxycarboxylic acid represented by the above formula (1), a repeating unit derived from the aromatic diol represented by the above formula (3) in which both X and Y are oxygen atoms, and a repeating unit derived from the aromatic dicarboxylic acid represented by the above formula (2). Furthermore, it is more preferable that the liquid crystal polymer has at least a repeating unit derived from an aromatic hydroxycarboxylic acid, and it is still more preferable that it has at least one selected from the group consisting of a repeating unit derived from p-hydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid. It is particularly preferable that it has a repeating unit derived from p-hydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid.

[0030] Also, as another preferred embodiment, in terms of more excellent effects of the present invention, the liquid crystal polymer preferably has at least one selected from the group consisting of a repeating unit derived from 6-hydroxy-2-naphthoic acid, a repeating unit derived from an aromatic diol, a repeating unit derived from terephthalic acid, and a repeating unit derived from 2,6-naphthalenedicarboxylic acid, and more preferably has all of the repeating unit derived from 6-hydroxy-2-naphthoic acid, the repeating unit derived from an aromatic diol, the repeating unit derived from terephthalic acid, and the repeating unit derived from 2,6-naphthalenedicarboxylic acid.

[0031] When the liquid crystal polymer contains a repeating unit derived from an aromatic hydroxycarboxylic acid, its composition ratio is preferably 50 to 65 mol% based on all the repeating units of the liquid crystal polymer. Also, it is preferable that the liquid crystal polymer has only a repeating unit derived from an aromatic hydroxycarboxylic acid. When the liquid crystal polymer contains a repeating unit derived from an aromatic diol, its composition ratio is preferably 17.5 to 25 mol% based on all the repeating units of the liquid crystal polymer. When the liquid crystal polymer contains a repeating unit derived from an aromatic dicarboxylic acid, its composition ratio is preferably 11 to 23 mol% based on all the repeating units of the liquid crystal polymer. When the liquid crystal polymer contains a repeating unit derived from any of an aromatic diamine, an aromatic hydroxyamine, and an aromatic aminocarboxylic acid, its composition ratio is preferably 2 to 8 mol% based on all the repeating units of the liquid crystal polymer.

[0032] The synthesis method of the liquid crystal polymer is not particularly limited, and it can be synthesized by polymerizing the above compounds by known methods such as melt polymerization, solid-phase polymerization, solution polymerization, and slurry polymerization. As the liquid crystal polymer, commercially available products may be used. Examples of commercially available products of the liquid crystal polymer include "Rapelos" manufactured by Polyplastics Co., Ltd., "Vectra" manufactured by Celanese Corporation, "UENO LCP" manufactured by Ueno Pharmaceutical Co., Ltd., "Sumika Super LCP" manufactured by Sumitomo Chemical Co., Ltd., "Zyder" manufactured by ENEOS Corporation, and "Xyron" manufactured by Toray Industries, Inc. Note that the liquid crystal polymer may form a chemical bond with a crosslinking agent or a compatible component (reactive compatibilizer), etc., which are optional components, within the polymer layer. This also applies to components other than the liquid crystal polymer.

[0033] A resin layer with a standard dielectric tangent of less than 0.002 can be easily manufactured. Furthermore, in terms of the more excellent effects of the present invention, the standard dielectric tangent of the liquid crystal polymer is preferably less than 0.002, more preferably 0.0015 or less, and still more preferably 0.001 or less. The lower limit is not particularly limited and may be, for example, 0.0001 or more. Note that when the resin layer contains two or more types of liquid crystal polymers, the "dielectric tangent of the liquid crystal polymer" means the mass average value of the dielectric tangents of the two or more types of liquid crystal polymers.

[0034] The standard dielectric tangent of the liquid crystal polymer contained in the resin layer can be measured by the following method. First, immerse it in an organic solvent (e.g., pentafluorophenol) that is 1000 mass times the total mass of the resin layer, and then heat it at 120 °C for 12 hours to elute the organic solvent-soluble components containing the liquid crystal polymer into the organic solvent. Next, separate the eluate containing the liquid crystal polymer and the non-eluted components by filtration. Subsequently, add acetone as a poor solvent to the eluate to precipitate the liquid crystal polymer, and separate the precipitate by filtration. Fill the obtained precipitate into a PTFE (polytetrafluoroethylene) tube (outer diameter 2.5 mm, inner diameter 1.5 mm, length 10 mm), and use a cavity resonator (e.g., "CP-531" manufactured by Kanto Electronic Application Development Co., Ltd.) to measure the dielectric properties by the cavity resonator perturbation method under the conditions of a temperature of 23 °C and a frequency of 28 GHz. By correcting the influence of the voids in the PTFE tube with Bruggeman's equation and the porosity, the standard dielectric tangent of the liquid crystal polymer can be obtained. The above void fraction (volume fraction of voids in the tube) is calculated as follows. The volume of the space inside the tube is determined from the inner diameter and length of the above tube. Next, after measuring the weights of the tube before and after filling with the precipitate to obtain the mass of the filled precipitate, the volume of the filled precipitate is determined from the obtained mass and the specific gravity of the precipitate. By dividing the volume of the precipitate thus obtained by the volume of the space inside the tube obtained above and calculating the filling rate, the void fraction can be calculated. When using a commercially available product of liquid crystal polymer, the value of the dielectric tangent described as the catalog value of the commercially available product may be used.

[0035] As for the liquid crystal polymer, in terms of more excellent heat resistance, the melting point Tm is preferably 250 °C or higher, more preferably 280 °C or higher, and still more preferably 310 °C or higher. The upper limit value of the melting point Tm of the liquid crystal polymer is not particularly limited, but in terms of more excellent moldability, it is preferably 400 °C or lower, and more preferably 380 °C or lower. The melting point Tm of the liquid crystal polymer can be determined by measuring the temperature at which an endothermic peak appears using a differential scanning calorimeter (DSC-60A manufactured by Shimadzu Corporation). When using a commercially available product of liquid crystal polymer, the melting point Tm described as the catalog value of the commercially available product may be used.

[0036] The number average molecular weight (Mn) of the liquid crystal polymer is not particularly limited, but is preferably 10,000 to 600,000, and more preferably 30,000 to 150,000. The number average molecular weight of the liquid crystal polymer is a polystyrene conversion value measured by GPC, and can be measured by a method according to the method for measuring the number average molecular weight of the above resin layer.

[0037] The liquid crystal polymer may be used alone or in combination of two or more. The content of the liquid crystal polymer is preferably 40 to 99.9% by mass, more preferably 50 to 95% by mass, and still more preferably 60 to 90% by mass with respect to the total mass of the resin layer. Incidentally, the contents of the liquid crystal polymer and the components described later in the resin layer can be measured by known methods such as infrared spectroscopy and gas chromatography-mass spectrometry.

[0038] (Optional component) The polymer layer may contain optional components other than the above polymers. Examples of the optional components include polyolefins, other polymers, compatibilizing components, heat stabilizers, crosslinking agents, and lubricants.

[0039] - Polyolefin - The polymer layer may contain a polyolefin. In this specification, "polyolefin" is intended to mean a polymer (polyolefin resin) having repeating units derived from olefins. The polymer layer preferably contains a liquid crystal polymer and a polyolefin, and more preferably contains a liquid crystal polymer, a polyolefin, and a compatibilizing component. By using a polyolefin together with the liquid crystal polymer, a resin layer having a dispersed phase formed by the polyolefin can be produced. The method for producing the resin layer having the above dispersed phase will be described later.

[0040] The polyolefin may be linear or branched. Further, the polyolefin may have a cyclic structure such as a polycyclic olefin. Examples of the polyolefin include polyethylene, polypropylene (PP), polymethylpentene (TPX manufactured by Mitsui Chemicals, Inc., etc.), hydrogenated polybutadiene, cycloolefin polymer (COP, Zeonor manufactured by Zeon Corporation, etc.), and cycloolefin copolymer (COC, Apel manufactured by Mitsui Chemicals, Inc., etc.). The polyethylene may be either high-density polyethylene (HDPE) or low-density polyethylene (LDPE). Further, the polyethylene may be linear low-density polyethylene (LLDPE).

[0041] The polyolefin may be a copolymer of an olefin and a copolymerization component other than olefins such as acrylate, methacrylate, styrene, and / or vinyl acetate-based monomers. Examples of the polyolefin that is the copolymer include, for example, styrene-ethylene / butylene-styrene copolymer (SEBS). SEBS may be hydrogenated. However, in terms of more excellent effects of the present invention, the copolymerization ratio of the copolymerization component other than olefins is preferably small, and it is more preferably not containing the copolymerization component. For example, the content of the above copolymerization component is preferably 0 to 40% by mass, more preferably 0 to 5% by mass, based on the total mass of the polyolefin. Further, the polyolefin preferably substantially does not contain a reactive group described later, and the content of the repeating unit having a reactive group is preferably 0 to 3% by mass based on the total mass of the polyolefin.

[0042] As the polyolefin, polyethylene, COP, or COC is preferable, polyethylene is more preferable, and low-density polyethylene (LDPE) is even more preferable.

[0043] The polyolefin may be used alone or in combination of two or more. When the polymer layer contains a polyolefin, the content is preferably 0.1% by mass or more, more preferably 5% by mass or more, based on the total mass of the polymer layer (or resin layer), in terms of more excellent surface properties of the polymer layer. The upper limit is not particularly limited, but in terms of more excellent smoothness of the polymer layer, it is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 25% by mass or less, based on the total mass of the polymer layer (or resin layer). Also, when the content of the polyolefin is 50% by mass or less, it is easy to sufficiently increase the heat distortion temperature and improve the solder heat resistance.

[0044] -Compatibilizing component- Examples of the compatibilizing component include a polymer having a portion highly compatible or having an affinity for the liquid crystal polymer (non-reactive compatibilizer), and a polymer having a reactive group for the phenolic hydroxyl group or carboxyl group at the terminal of the liquid crystal polymer (reactive compatibilizer). The reactive group of the reactive compatibilizer is preferably an epoxy group or a maleic anhydride group. As the compatibilizing component, a copolymer having a portion highly compatible or having an affinity for the polyolefin is preferable. Further, when the film contains a polyolefin and a compatibilizing component, a reactive compatibilizer is preferable as the compatibilizing component in terms of being able to finely disperse the polyolefin. Note that the compatibilizing component (particularly the reactive compatibilizer) may form a chemical bond with a component such as a liquid crystal polymer in the polymer layer.

[0045] Examples of the reactive compatibilizer include an epoxy group-containing polyolefin copolymer, an epoxy group-containing vinyl copolymer, a maleic anhydride-containing polyolefin copolymer, a maleic anhydride-containing vinyl copolymer, an oxazoline group-containing polyolefin copolymer, an oxazoline group-containing vinyl copolymer, and a carboxyl group-containing olefin copolymer. Among them, an epoxy group-containing polyolefin copolymer or a maleic anhydride-grafted polyolefin copolymer is preferable.

[0046] Examples of the epoxy group-containing polyolefin copolymer include an ethylene / glycidyl methacrylate copolymer, an ethylene / glycidyl methacrylate / vinyl acetate copolymer, an ethylene / glycidyl methacrylate / methyl acrylate copolymer, a polystyrene graft copolymer to an ethylene / glycidyl methacrylate copolymer (EGMA-g-PS), a polymethyl methacrylate graft copolymer to an ethylene / glycidyl methacrylate copolymer (EGMA-g-PMMA), and an acrylonitrile / styrene graft copolymer to an ethylene / glycidyl methacrylate copolymer (EGMA-g-AS). Examples of commercially available epoxy group-containing polyolefin copolymers include, for example, Bondfast 2C and Bondfast E manufactured by Sumitomo Chemical Co., Ltd.; Lotadar manufactured by Arkema; and Modiper A4100 and Modiper A4400 manufactured by Nippon Oil Corporation.

[0047] Examples of epoxy group-containing vinyl copolymers include, for example, glycidyl methacrylate graft polystyrene (PS-g-GMA), glycidyl methacrylate graft polymethyl methacrylate (PMMA-g-GMA), and glycidyl methacrylate graft polyacrylonitrile (PAN-g-GMA).

[0048] Examples of maleic anhydride-containing polyolefin copolymers include, for example, maleic anhydride graft polypropylene (PP-g-MAH), maleic anhydride graft ethylene / propylene rubber (EPR-g-MAH), and maleic anhydride graft ethylene / propylene / diene rubber (EPDM-g-MAH). Examples of commercially available maleic anhydride-containing polyolefin copolymers include, for example, the Orevac G series manufactured by Arkema; and the FUSABOND E series manufactured by The Dow Chemical Company.

[0049] Examples of maleic anhydride-containing vinyl copolymers include, for example, maleic anhydride graft polystyrene (PS-g-MAH), maleic anhydride graft styrene / butadiene / styrene copolymer (SBS-g-MAH), maleic anhydride graft styrene / ethylene / butene / styrene copolymer (SEBS-g-MAH), and styrene / maleic anhydride copolymer and acrylate / maleic anhydride copolymer. Examples of commercially available maleic anhydride-containing vinyl copolymers include the Toughtech M series (SEBS-g-MAH) manufactured by Asahi Kasei Corporation.

[0050] Examples of compatible components also include oxazoline-based compatibilizers (e.g., bisoxazoline-styrene-maleic anhydride copolymer, bisoxazoline-maleic anhydride-modified polyethylene, and bisoxazoline-maleic anhydride-modified polypropylene), elastomer-based compatibilizers (e.g., aromatic resins, petroleum resins), ethylene glycidyl methacrylate copolymer, ethylene ethyl acrylate maleic anhydride copolymer, ethylene glycidyl methacrylate-acrylonitrile styrene, acid-modified polyethylene wax, COOH-modified polyethylene graft polymer, COOH-modified polypropylene graft polymer, polyethylene-polyamide graft copolymer, polypropylene-polyamide graft copolymer, methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene rubber, EVA-PVC-graft copolymer, vinyl acetate-ethylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, hydrogenated styrene-isopropylene-block copolymer, and amine-modified styrene-ethylene-butene-styrene copolymer.

[0051] Also, an ionomer resin may be used as a compatible component. Examples of such ionomer resins include ethylene-methacrylic acid copolymer ionomers, ethylene-acrylic acid copolymer ionomers, propylene-methacrylic acid copolymer ionomers, propylene-acrylic acid copolymer ionomers, butylene-acrylic acid copolymer ionomers, ethylene-vinyl sulfonic acid copolymer ionomers, styrene-methacrylic acid copolymer ionomers, sulfonated polystyrene ionomers, fluorine-based ionomers, telechelic polybutadiene acrylic acid ionomers, sulfonated ethylene-propylene-diene copolymer ionomers, hydrogenated polypentamer ionomers, polypentamer ionomers, poly(vinylpyridinium salt) ionomers, poly(vinyltrimethylammonium salt) ionomers, poly(vinylbenzylphosphonium salt) ionomers, styrene-butadiene acrylic acid copolymer ionomers, polyurethane ionomers, sulfonated styrene-2-acrylamido-2-methylpropanesulfate ionomers, acid-amine ionomers, aliphatic ionenes, and aromatic ionenes.

[0052] When the polymer layer contains a compatible component, its content is preferably 0.05 to 30% by mass, more preferably 0.1 to 20% by mass, and still more preferably 0.5 to 10% by mass based on the total mass of the polymer layer (or resin layer).

[0053] -Heat stabilizer- The polymer layer may contain a heat stabilizer for the purpose of suppressing thermal oxidative degradation during melt extrusion film formation and improving the flatness and smoothness of the surface of the polymer layer. Examples of heat stabilizers include phenolic stabilizers and amine stabilizers having a radical scavenging action; phosphite stabilizers and sulfur stabilizers having a peroxide decomposition action; and hybrid stabilizers having both a radical scavenging action and a peroxide decomposition action.

[0054] Examples of phenolic stabilizers include hindered phenolic stabilizers, semi-hindered phenol stabilizers, and res-hindered phenolic stabilizers. Examples of commercially available hindered phenol stabilizers include Adekastab AO-20, AO-50, AO-60, and AO-330 manufactured by ADEKA Corporation; and Irganox 259, 1035, and 1098 manufactured by BASF Corporation. Examples of commercially available semi-hindered phenol stabilizers include Adekastab AO-80 manufactured by ADEKA Corporation; and Irganox 245 manufactured by BASF Corporation. Examples of commercially available less-hindered phenol stabilizers include Nocrack 300 manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.; Adekastab AO-30 and AO-40 manufactured by ADEKA Corporation. Examples of commercially available phosphite stabilizers include Adekastab 2112, PEP-8, PEP-36, and HP-10 manufactured by ADEKA Corporation. Examples of commercially available hybrid stabilizers include Sumilizer GP manufactured by Sumitomo Chemical Co., Ltd.

[0055] As the heat stabilizer, a hindered phenol stabilizer, a semi-hindered phenol stabilizer, or a phosphite stabilizer is preferable, and a hindered phenol stabilizer is more preferable in terms of better heat stabilization effect. On the other hand, a semi-hindered phenol stabilizer or a phosphite stabilizer is more preferable in terms of electrical properties.

[0056] The heat stabilizer may be used alone or in combination of two or more. When the polymer layer contains a heat stabilizer, the content of the heat stabilizer is preferably 0.0001 to 10% by mass, more preferably 0.01 to 5% by mass, and still more preferably 0.1 to 2% by mass based on the total mass of the polymer layer (or resin layer).

[0057] - Additives - The polymer layer may contain additives other than the above components. Examples of the additives include plasticizers, lubricants, inorganic particles and organic particles, and UV absorbers.

[0058] Examples of the plasticizer include alkyl phthalyl alkyl glycolate compounds, bisphenol compounds (bisphenol A, bisphenol F), alkyl phthalyl alkyl glycolate compounds, phosphate ester compounds, carboxylic acid ester compounds, and polyhydric alcohols. The content of the plasticizer may be 0 to 5% by mass based on the total mass of the resin layer. Examples of the lubricant include fatty acid esters and metal soaps (for example, inorganic salts of stearic acid). The content of the lubricant may be 0 to 5% by mass based on the total mass of the polymer layer (or resin layer). The polymer layer may contain inorganic particles and / or organic particles as a reinforcing material, a matting agent, a dielectric constant, or a dielectric loss tangent improving agent. Examples of the inorganic particles include silica, titanium oxide, barium sulfate, talc, zirconia, alumina, silicon nitride, silicon carbide, calcium carbonate, silicate, glass beads, graphite, tungsten carbide, carbon black, clay, mica, carbon fiber, glass fiber, and metal powder. Examples of the organic particles include crosslinked acrylic and crosslinked styrene. The content of the inorganic particles and the organic particles may be 0 to 50% by mass based on the total mass of the polymer layer (or resin layer). Examples of the UV absorber include salicylate compounds, benzophenone compounds, benzotriazole compounds, substituted acrylonitrile compounds, and s-triazine compounds. The content of the UV absorber may be 0 to 5% by mass based on the total mass of the polymer layer (or resin layer).

[0059] In addition, the polymer layer may contain a polymer component other than a polymer having a low standard dielectric loss tangent as long as the effects of the present invention are not impaired. Examples of the polymer component include thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, and polyester ether ketone.

[0060] The thickness of the polymer layer is preferably 5 to 1000 μm, more preferably 10 to 500 μm, and still more preferably 20 to 300 μm. The thickness of the polymer layer is the arithmetic mean value of the measured values obtained by measuring the thickness of the polymer layer at 100 arbitrarily different points from an observation image obtained by observing a cross-section in the thickness direction of the laminate using a scanning electron microscope (SEM).

[0061] <Adhesive resin layer> It is preferable that the resin layer has an adhesive resin layer on the surface in contact with the metal layer in order to improve the adhesion to the metal layer. As the adhesive resin layer, a known adhesive layer used in the production of wiring boards such as copper-clad laminates can be used. For example, a layer composed of a cured product of an adhesive composition containing a known binder resin can be mentioned.

[0062] (Binder resin) The adhesive resin layer preferably contains a binder resin. Examples of the binder resin include (meth)acrylic resin, vinyl polycinnamate, polycarbonate, polyimide, polyamideimide, polyesterimide, polyetherimide, polyetherketone, polyetheretherketone, polyethersulfone, polysulfone, polyparylene, polyester, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, polyurethane, polyvinyl alcohol, cellulose acylate, fluorinated resin, liquid crystal polymer, syndiotactic polystyrene, silicone resin, epoxy silicone resin, phenol resin, alkyd resin, epoxy resin, maleic acid resin, melamine resin, urea resin, aromatic sulfonamide, benzoguanamine resin, silicone elastomer, aliphatic polyolefin (for example, polyethylene and polypropylene), and cyclic olefin copolymer. Among them, polyimide, liquid crystal polymer, polyimide, syndiotactic polystyrene, or cyclic olefin copolymer is preferable, and polyimide is more preferable.

[0063] The binder resin may be used alone or in combination of two or more. The content of the binder resin is preferably 60 to 99.9% by mass, more preferably 70 to 99.0% by mass, and still more preferably 80 to 97.0% by mass with respect to the total mass of the adhesion resin layer.

[0064] (Reactive compound) The adhesion resin layer may contain a reaction product of a compound having a reactive group. Hereinafter, the compound having a reactive group and its reaction product are also collectively referred to as a "reactive compound". The adhesion resin layer preferably contains a reactive compound. The reactive group of the reactive compound is preferably a group capable of reacting with a group present on the surface of the polymer layer (particularly, a group having an oxygen atom such as a carboxy group and a hydroxy group). Examples of the reactive group include an epoxy group, an oxetanyl group, an isocyanate group, an acid anhydride group, a carbodiimide group, an N-hydroxyester group, a glyoxal group, an imidoester group, a halogenated alkyl group, and a thiol group. At least one group selected from the group consisting of an epoxy group, an acid anhydride group, and a carbodiimide group is preferable, and an epoxy group is more preferable.

[0065] Specific examples of the reactive compound having an epoxy group include aromatic glycidylamine compounds (for example, N,N-diglycidyl-4-glycidyloxyaniline, 4,4'-methylenebis(N,N-diglycidylaniline), N,N-diglycidyl-o-toluidine, and N,N,N',N'-tetraglycidyl-m-xylenediamine, 4-t-butylphenyl glycidyl ether), aliphatic glycidylamine compounds (for example, 1,3-bis(diglycidylaminomethyl)cyclohexane, etc.), and aliphatic glycidyl ether compounds (for example, sorbitol polyglycidyl ether). Among them, aromatic glycidylamine compounds are preferable in terms of more excellent effects of the present invention.

[0066] Specific examples of the reactive compound having an acid anhydride group include tetracarboxylic dianhydrides (for example, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 2,3,3',4'-biphenyl tetracarboxylic dianhydride, oxydiphthalic dianhydride, diphenylsulfone-3,4,3',4'-tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)sulfide dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, p-phenylene bis(trimellitic monoester anhydride), p-biphenylene bis(trimellitic monoester anhydride), m-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, p-terphenyl-3,4,3',4'-tetracarboxylic dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 2,2-bis[(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride).

[0067] Specific examples of the reactive compound having a carbodiimide group include monocarboxylic diimide compounds (for example, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and N,N'-di-2,6-diisopropylphenylcarbodiimide), and polycarbodiimide compounds (for example, compounds produced by the methods described in U.S. Patent No. 2,941,956, Japanese Patent Publication No. 47-033279, J. Org. Chem., Vol. 28, p2069-2075 (1963), and Chemical Review 1981, Vol. 81, No. 4, p. 619-621, etc.). Commercially available products of the reactive compound having a carbodiimide group include Carbodilite (registered trademark) HMV-8CA, LA-1, and V-03 (all manufactured by Nisshinbo Chemical Inc.), Stabaxol (registered trademark) P, P100, and P400 (all manufactured by Rhein Chemie), and Stabilizer 9000 (trade name, manufactured by Raschig Chemie), etc.

[0068] The number of reactive groups possessed by the reactive compound is 1 or more, but from the viewpoint of more excellent adhesion of the metal layer, 3 or more is preferable. The number of reactive groups possessed by the reactive compound is preferably 6 or less, more preferably 5 or less, and still more preferably 4 or less in terms of more excellent effects of the present invention. The reactant of the compound having a reactive group is not particularly limited as long as it is a compound derived from the compound having a reactive group. For example, a reactant in which the reactive group of the compound having a reactive group reacts with a group containing an oxygen atom present on the surface of the polymer film can be mentioned.

[0069] The reactive compound may be used alone or in combination of two or more. The content of the reactive compound is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and still more preferably 3 to 20% by mass, based on the total mass of the adhesion resin layer, in terms of achieving a good balance between the effects of the present invention and excellent adhesion to the metal layer.

[0070] The adhesion resin layer may contain components other than the reactive compound and the binder resin (hereinafter also referred to as "additives"). Examples of the additives include inorganic fillers, curing catalysts, and flame retardants. The content of the additives is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and still more preferably 3 to 20% by mass, based on the total mass of the adhesion resin layer.

[0071] (Residual solvent) The adhesion resin layer may contain a solvent. In this specification, "solvent" is intended to mean an organic solvent and does not include water. "Organic solvent" means an organic compound that is liquid at 25°C and atmospheric pressure. Examples of the solvent contained in the adhesion resin layer include, for example, the organic solvents contained as solvents in the composition for forming the adhesion resin layer described later.

[0072] The content of the solvent in the adhesion resin layer is preferably 500 ppm by mass or less, more preferably 300 ppm by mass or less, still more preferably 200 ppm by mass or less, and particularly preferably 50 ppm by mass or less, based on the total mass of the adhesion resin layer, in terms of achieving more excellent effects of the present invention and more effectively suppressing the generation of bubbles due to residual solvents. The lower limit is not particularly limited and may be 0 ppm by mass or more, but is preferably 0.1 ppm by mass or more, and more preferably 5 ppm by mass or more, based on the total mass of the adhesion resin layer. The content of the solvent in the adhesion resin layer can be adjusted by changing the drying temperature, drying air velocity, and / or drying time. Note that the content of the solvent contained in the adhesion resin layer generally tends not to vary significantly even during storage of the laminate in an environment of 23°C and 1 atm, particularly for solvents such as ketone compounds.

[0073] (Physical properties of the adherent resin layer) - Thickness - The thickness of the adherent resin layer is preferably 1 μm or less, more preferably 0.8 μm or less, still more preferably 0.7 μm or less, and particularly preferably 0.6 μm or less in terms of more excellent effects of the present invention. The lower limit is not particularly limited, but is preferably 0.05 μm or more, more preferably 0.1 μm or more, and still more preferably 0.2 μm or more in terms of more excellent adhesion between the metal layer and the resin layer. In addition, the ratio of the thickness of the adherent resin layer to the thickness of the polymer layer is preferably 0.1 to 2%, and more preferably 0.2 to 1.6% in terms of excellent balance between the effects of the present invention and the adhesion to the metal layer. Note that the thickness of the adherent resin layer described above is the thickness per layer of the adherent resin layer. The thickness of the adherent resin layer can be measured according to the measurement method of the thickness of the polymer layer described above.

[0074] - Elastic modulus - The elastic modulus of the adherent resin layer is preferably 0.8 GPa or more, more preferably 1.0 GPa or more, still more preferably 1.1 GPa or more, and particularly preferably 1.2 GPa or more in terms of more excellent adhesion to the metal layer. The upper limit value of the elastic modulus of the adherent resin layer is not particularly limited, and is, for example, 5 GPa or less. The elastic modulus of the adherent resin layer is the indentation elastic modulus measured according to ISO14577, and the specific measurement method is described in the Examples section below. The elastic modulus of the adherent resin layer can be adjusted by changing the ratio of the binder resin to the reactive compound.

[0075] <Physical properties of the resin layer> (Thickness) The thickness of the resin layer is preferably 5 to 1000 μm, more preferably 10 to 500 μm, and still more preferably 20 to 300 μm. The thickness of the resin layer can be measured according to the measurement method of the thickness of the polymer layer described above.

[0076] (Dispersed phase) When the resin layer contains a polyolefin, it is preferable that the polyolefin forms a dispersed phase in the resin layer. The above-mentioned dispersed phase corresponds to the island part in the resin layer having a so-called sea-island structure inside. There is no limitation on the method of forming a sea-island structure in the resin layer and allowing the polyolefin to exist as the dispersed phase. For example, by adjusting the contents of the liquid crystal polymer and the polyolefin contained in the resin layer to be within the ranges of the above-mentioned preferred contents respectively, a dispersed phase of the polyolefin can be formed.

[0077] The average dispersed diameter of the above-mentioned dispersed phase is preferably 0.001 to 50.0 μm, more preferably 0.005 to 20.0 μm, and still more preferably 0.01 to 10.0 μm in terms of better smoothness.

[0078] The dispersed phase is also preferably flat, and it is preferable that the flat surface of the flat dispersed phase is substantially parallel to the surface of the resin layer. Also, in terms of reducing the anisotropy of the resin layer, the flat surface of the flat dispersed phase is preferably substantially circular when observed from a direction perpendicular to the surface of the resin layer. It is considered that when such a dispersed phase is dispersed in the resin layer, the dimensional changes generated in the resin layer can be absorbed, and better surface properties and smoothness can be realized. The average dispersed diameter and the shape of the above-mentioned dispersed phase are obtained from the observation images obtained by observing a cross-section in the thickness direction of the laminate using a scanning electron microscope (SEM). The detailed measurement method of the average dispersed diameter of the dispersed phase will be described in the Examples section below.

[0079] The laminate may have other layers other than the resin layer and the metal layer as required. Examples of the other layers include a rust-proof layer and a heat-resistant layer.

[0080] 〔Physical properties of the laminate〕 The peel strength between the resin layer and the metal layer in the laminate is preferably more than 0.5 kN / m, more preferably 0.55 kN / m or more, still more preferably 0.6 kN / m or more, and particularly preferably 0.65 kN / m or more. The greater the above-mentioned peel strength, the better the adhesion between the resin layer and the metal layer. The upper limit value of the peel strength of the laminate is not particularly limited and may be 1.0 or more. The method for measuring the peel strength of the laminate will be described in the Examples section below.

[0081] [Manufacturing method of laminate] The manufacturing method of the laminate is not particularly limited. For example, a step of producing a resin film using a composition containing components constituting the resin layer (hereinafter also referred to as "Step 1"), and laminating the resin film produced in Step 1 with a metal foil made of the metal constituting the metal layer, and then pressing the resin film and the metal foil under high-temperature conditions to produce a laminate having a resin layer and a metal layer (hereinafter also referred to as "Step 2").

[0082] [Step 1] The method for producing the resin film is not particularly limited. For example, it includes at least a step of producing a polymer film using a composition containing components constituting the polymer layer (hereinafter also referred to as "Step 1A"), and optionally, a step of attaching a composition for forming an adhesive resin layer on the polymer film produced in Step 1A to produce a polymer film with an adhesive resin layer (resin film) having a polymer film and an adhesive resin layer (hereinafter also referred to as "Step 1B").

[0083] [Step 1A] Step 1A for producing the polymer film is not particularly limited. For example, it includes a pelletizing step of kneading the components constituting the above polymer layer to obtain pellets, and a film-forming step of forming a resin film using the above pellets. Hereinafter, taking the case of producing a polymer film containing a liquid crystal polymer as an example, each step will be described.

[0084] [Pelletizing step] (1) Raw material form Polymers such as liquid crystal polymers used for film formation can be used as they are in pellet form, flake form, or powder form. However, for the purpose of stabilizing film formation or uniformly dispersing additives (meaning components other than liquid crystal polymers; the same applies hereinafter), it is preferable to use pellets obtained by kneading and pelletizing one or more raw materials (meaning at least one of polymers and additives; the same applies hereinafter) using an extruder.

[0085] (2) Drying or drying substitution by venting When pelletizing, it is preferable to pre-dry the liquid crystal polymer and additives. As drying methods, there are methods such as circulating heated air with a low dew point and dehumidifying by vacuum drying. In particular, in the case of resins that are easily oxidized, vacuum drying or drying using an inert gas is preferable.

[0086] (3) Raw material supply method The raw material supply method may be a method of pre-mixing the raw materials before kneading and pelletizing and then supplying them, a method of separately supplying the raw materials into the extruder at a constant ratio, or a method combining both.

[0087] (4) Atmosphere during extrusion When melt-extruding, it is preferable to prevent heat and oxidative degradation as much as possible within a range that does not interfere with uniform dispersion. It is also effective to reduce the oxygen concentration by using a vacuum pump to reduce the pressure or by flowing an inert gas. These methods may be implemented alone or in combination.

[0088] (5) Temperature The kneading temperature is preferably set below the thermal decomposition temperature of the liquid crystal polymer and additives, and as low as possible within a range where the load on the extruder and the reduction in uniform kneading property do not become problems.

[0089] (6) Pressure The kneading resin pressure during pelletization is preferably carried out at 0.05 to 30 MPa. In the case of a resin that is likely to generate coloration or gel due to shear, it is preferable to apply an internal pressure of about 1 to 10 MPa in the extruder to fill the resin raw material in the twin-screw extruder.

[0090] (7) Pelletizing method As a pelletizing method, it is common to extrude into a noodle shape, solidify it in water, and then cut it. However, after melting by an extruder, pelletization may be performed by an under-water cut method of directly extruding from a die into water while cutting, or a hot cut method of cutting while in a hot state.

[0091] (8) Pellet size The pellet size preferably has a cross-sectional area of 1 to 300 mm 2 and a length of 1 to 30 mm, more preferably a cross-sectional area of 2 to 100 mm 2 and a length of 1.5 to 10 mm.

[0092] (Drying) (1) Purpose of drying Before melt film formation, it is preferable to reduce the moisture and volatile components in the pellets, and it is effective to dry the pellets. When the pellets contain moisture or volatile components, it not only causes a decrease in appearance due to foam entrapment in the polymer film or a decrease in haze, but also a decrease in physical properties due to molecular chain scission of the liquid crystal polymer, or roll fouling due to the generation of monomers or oligomers may occur. Also, depending on the type of liquid crystal polymer used, in some cases, the formation of oxidation cross-linked products during melt film formation can be suppressed by removing dissolved oxygen by drying.

[0093] (2) Drying method · Heating method Regarding the drying method, it is common to use a dehumidifying hot air dryer in terms of drying efficiency and economy, but it is not particularly limited as long as the target moisture content can be obtained. Also, it is not a problem to select a more appropriate method according to the physical property characteristics of the liquid crystal polymer. Examples of heating methods include pressurized steam, heater heating, far-infrared irradiation, microwave heating, and heat medium circulation heating methods.

[0094] <Film forming process> The film forming process will be described below.

[0095] (1) Extrusion conditions · Raw material drying Even in the process of melting and plasticizing pellets by an extruder, it is preferable to reduce moisture and volatile components in the same manner as in the pelletizing process, and it is effective to dry the pellets.

[0096] · Raw material supply method When there are multiple types of raw materials (pellets) introduced from the supply port of the extruder, they may be premixed in advance (premix method), supplied separately into the extruder at a certain ratio, or a method combining both may be used. Also, in order to stabilize extrusion, it is generally done to reduce fluctuations in the temperature and bulk specific gravity of the raw materials introduced from the supply port. Also, from the viewpoint of plasticization efficiency, the raw material temperature is preferably high as long as it does not stick and block the supply port. In the case of an amorphous state, the range of {glass transition temperature (Tg) (°C) - 150°C} to {Tg (°C) - 1°C} is preferable, and in the case of a crystalline resin, the range of {melting point (Tm) (°C) - 150°C} to {Tm (°C) - 1°C} is preferable, and the raw materials are heated or kept warm. Also, from the viewpoint of plasticization efficiency, the bulk specific gravity of the raw materials is preferably 0.3 times or more of the molten state, and more preferably 0.4 times or more. When the bulk specific gravity of the raw materials is less than 0.3 times the specific gravity of the molten state, it is also preferable to perform processing such as compressing the raw materials to form pseudo-pellets.

[0097] · Atmosphere during extrusion During melt extrusion, the atmosphere should be such that it does not interfere with uniform dispersion and, to the extent possible, prevent heat and oxidative degradation. Injecting an inert gas (such as nitrogen), reducing the oxygen concentration in the extruder using a vacuum hopper, and providing a vent port in the extruder and performing vacuum pumping with a vacuum pump are also effective. These vacuum pumping and inert gas injection operations can be carried out independently or in combination.

[0098] · Rotational speed The rotational speed of the extruder is preferably 5 - 300 rpm, more preferably 10 - 200 rpm, and even more preferably 15 - 100 rpm. If the rotational speed is at or above the lower limit value, the residence time will be shortened, the decrease in molecular weight due to heat degradation can be suppressed, and discoloration can be suppressed. If the rotational speed is at or below the upper limit value, the breakage of molecular chains due to shear can be suppressed, and the decrease in molecular weight and the increase in crosslinked gel can be suppressed. It is preferable to select appropriate conditions for the rotational speed from both aspects of uniform dispersibility and heat degradation due to extended residence time.

[0099] · Temperature Barrel temperature (feeding section temperature T1 °C 、 compression section temperature T2 °C, metering section temperature T3 °C) is generally determined by the following method. When melting and plasticizing pellets by an extruder at a target temperature T °C, the metering section temperature T3 is set to T ± 20 °C considering the shear heat generation amount. At this time, T2 is set within the range of T3 ± 20 °C considering extrusion stability and resin thermal decomposability. T1 is generally set as {T2 (°C) - 5 °C} to {T2 (°C) - 150 °C}, and the optimum value is selected from the viewpoints of ensuring the friction between the resin and the barrel, which serves as the driving force (feed force) for feeding the resin, and preheating at the feeding section. In the case of a normal extruder, it is possible to set the temperature by subdividing each zone of T1 - T3, and by making a setting such that the temperature change between each zone is gentle, it becomes possible to achieve more stabilization. At this time, it is preferable that T is below the thermal degradation temperature of the resin. When the thermal degradation temperature is exceeded due to the shear heat generation of the extruder, it is also generally carried out to actively cool and remove the shear heat generation. Also, in order to achieve both improved dispersibility and thermal degradation, a condition of melting and mixing at a relatively high temperature in the first half of the extruder and then lowering the resin temperature in the second half is also effective.

[0100] · Pressure The resin pressure in the extruder is generally 1 to 50 MPa, preferably 2 to 30 MPa, and more preferably 3 to 20 MPa in terms of extrusion stability and melt uniformity. If the pressure in the extruder is 1 MPa or more, the filling rate of the melt in the extruder is sufficient, so that the occurrence of foreign matters due to the instability of the extrusion pressure and the generation of stagnant parts can be suppressed. Also, if the pressure in the extruder is 50 MPa or less, it is possible to suppress an excessive shear stress received inside the extruder, so that thermal decomposition due to an increase in the resin temperature can be suppressed.

[0101] · Residence time The residence time in the extruder (residence time during film formation) can be calculated from the volume of the extruder part and the discharge capacity of the polymer, similar to the pelletization process. The residence time is preferably 10 seconds to 60 minutes, more preferably 15 seconds to 45 minutes, and even more preferably 30 seconds to 30 minutes. If the residence time is 10 seconds or more, melt plasticization and dispersion of additives will be sufficient. If the residence time is 30 minutes or less, it is preferable in terms of suppressing resin deterioration and discoloration of the resin.

[0102] (Filtration) · Type, installation purpose, structure In order to prevent damage to the gear pump caused by foreign matters contained in the raw material and to extend the life of a filter with a fine pore diameter installed downstream of the extruder, it is generally used to provide filtration equipment at the outlet of the extruder. It is preferable to perform so-called breaker plate type filtration using a mesh-shaped filter medium in combination with a reinforcing plate having high strength and high aperture ratio.

[0103] · Mesh size, filtration area The mesh size is preferably 40 to 800 meshes, more preferably 60 to 700 meshes, and even more preferably 100 to 600 meshes. If the mesh size is 40 meshes or more, the passage of foreign matter through the mesh can be sufficiently suppressed. Also, if it is 800 meshes or less, the increase speed of the filtration pressure can be suppressed, and the mesh replacement frequency can be reduced. Further, in terms of filtration accuracy and strength retention, filter meshes are often used by overlapping multiple types with different mesh sizes. Also, since it is possible to increase the filtration opening area and maintain the strength of the mesh, a breaker plate may be used to reinforce the filter mesh. The opening ratio of the breaker plate to be used is often 30 to 80% in terms of filtration efficiency and strength. Also, the screen changer often uses one with the same diameter as the barrel diameter of the extruder, but in order to increase the filtration area, a tapered pipe may be used to use a filter mesh with a larger diameter, or the flow path may be branched to use a plurality of breaker plates. The filtration area is preferably selected based on the flow rate of 0.05 to 5 g / cm per second 2 , more preferably 0.1 to 3 g / cm 2 , and even more preferably 0.2 to 2 g / cm 2 . The filter clogs and the filtration pressure rises by capturing foreign matter. In that case, it is necessary to stop the extruder and replace the filter, but a type that can replace the filter while continuing the extrusion can also be used. Also, as a countermeasure against the increase in filtration pressure due to foreign matter capture, a filter having a function of reducing the filtration pressure by washing and removing the foreign matter captured by the filter in the reverse direction of the polymer flow path can also be used.

[0104] (Die) · Type, structure, material Foreign substances are removed by filtration, and the molten resin whose temperature is made uniform by a mixer is continuously sent to a die. The die is not particularly limited as long as it is designed to have little residence of the molten resin, and any of the commonly used T-dies, fishtail dies, and hanger coat dies can be used. Among these, the hanger coat die is preferable in terms of thickness uniformity and little residence.

[0105] ·Multi-layer film formation For the production of polymer films, a single-layer film-forming apparatus with low equipment costs is used. In addition, a multi-layer film-forming apparatus may be used to produce a polymer film having functional layers such as an adhesion resin layer, a surface protection layer, an adhesive layer, an easy-adhesion layer, and / or an antistatic layer. Specifically, methods of multi-layer formation using a feed block for multi-layers and methods using a multi-manifold die can be mentioned. It is preferable to thinly laminate the functional layer on the surface layer, but the layer ratio is not particularly limited.

[0106] (Cast) The film-forming process preferably includes a step of supplying the raw material resin in a molten state from a supply means and a step of landing the molten raw material resin on a casting roll to form it into a film shape. This may be cooled and solidified and wound up as a polymer film as it is, or it may be continuously sandwiched and formed into a film shape by passing between a pair of sandwiching surfaces. At that time, there is no particular limitation on the means for supplying the raw material resin in a molten state (melt). For example, as a specific supply means for the melt, an embodiment using an extruder that melts a raw material resin containing a liquid crystal polymer and extrudes it in a film shape may be used, an embodiment using an extruder and a die may be used, or an embodiment in which the raw material resin is once solidified into a film shape and then melted by a heating means to form a melt and supplied to the film-forming process may be used. When the molten resin extruded in a sheet shape from the die is sandwiched by an apparatus having a pair of sandwiching surfaces, not only can the surface form of the sandwiching surface be transferred to the surface of the polymer film, but the orientation can be controlled by applying elongation deformation to the composition containing the liquid crystal polymer.

[0107] ·Film-forming method, type Among the methods for forming a molten raw material resin into a film, it is preferable to pass it between two rolls (for example, a touch roll and a chill roll) because a high nip pressure can be applied and the surface shape of the polymer film is excellent. In this specification, when there are a plurality of casting rolls for transporting the melt, the casting roll closest to the supply means (for example, a die) of the liquid crystal polymer at the most upstream is referred to as a chill roll. In addition, a method of sandwiching between metal belts or a method combining a roll and a metal belt can also be used. In some cases, in order to improve the adhesion to the roll or the metal belt, film-forming methods such as an electrostatic printing method, an air knife method, an air chamber method, and a vacuum nozzle method can be combined and used on the casting drum. When obtaining a polymer film having a multilayer structure, it is preferable to obtain it by sandwiching the raw material resin containing the molten polymer extruded in multiple layers from a die. However, a polymer film having a single-layer structure can also be introduced into the sandwiching portion in the manner of melt lamination to obtain a polymer film having a multilayer structure. Further, by changing the peripheral speed difference or the orientation axis direction of the sandwiching portion at this time, a polymer film having a different inclined structure in the thickness direction can be obtained, and by performing this process several times, it is also possible to obtain a polymer film having three or more layers. Furthermore, deformation may be given, for example, by periodically vibrating the touch roll in the TD direction during sandwiching.

[0108] · Melt polymer temperature The discharge temperature (the resin temperature at the outlet of the supply means) is preferably (Tm - 10) °C to (Tm + 40) °C of the liquid crystal polymer in terms of improving the moldability and suppressing the deterioration of the liquid crystal polymer. As a guide for the melt viscosity, 50 to 3500 Pa·s is preferable. It is preferable that the cooling of the molten polymer between the air gaps is as small as possible, and it is preferable to make devices such as increasing the film-forming speed and shortening the air gap to reduce the temperature drop due to cooling.

[0109] · Touch roll temperature The temperature of the touch roll is preferably set below the Tg of the liquid crystal polymer. If the temperature of the touch roll is below the Tg of the liquid crystal polymer, adhesion of the molten polymer to the roll can be suppressed, resulting in a better appearance of the polymer film. For the same reason, the chill roll temperature is preferably set below the Tg of the liquid crystal polymer.

[0110] ·Film forming procedure In the film forming process, from the viewpoints of the film forming process and quality stabilization, it is preferable to form a film according to the following procedure. The molten polymer discharged from the die is landed on a cast roll and formed into a film shape, and then cooled and solidified and wound up as a polymer film. When applying nip pressure to the molten polymer, the molten polymer is passed between a first nip surface and a second nip surface set at a predetermined temperature, cooled and solidified, and wound up as a polymer film.

[0111] <Stretching process, heat relaxation treatment, heat setting treatment> Furthermore, after forming an unstretched polymer film by the above method, stretching, and / or heat relaxation treatment or heat setting treatment may be performed continuously or discontinuously. For example, each step can be carried out in the combinations of (a) to (g) below. Also, the order of longitudinal stretching and transverse stretching may be reversed, each step of longitudinal stretching and transverse stretching may be carried out in multiple stages, and each step of longitudinal stretching and transverse stretching may be combined with diagonal stretching or simultaneous biaxial stretching. (a) Transverse stretching (b) Transverse stretching → Heat relaxation treatment (c) Longitudinal stretching (d) Longitudinal stretching → Heat relaxation treatment (e) Longitudinal (transverse) stretching → Transverse (longitudinal) stretching (f) Longitudinal (transverse) stretching → Transverse (longitudinal) stretching → Heat relaxation treatment (g) Transverse stretching → Heat relaxation treatment → Longitudinal stretching → Heat relaxation treatment Hereinafter, the unstretched polymer film and the stretched polymer film are collectively referred to simply as "film".

[0112] ·Longitudinal stretching The longitudinal stretching can be achieved by heating between two pairs of rolls and making the peripheral speed on the outlet side faster than that on the inlet side. In terms of suppressing curling, it is preferable that the front and back surfaces of the film to be stretched have the same temperature. However, when controlling the optical properties in the thickness direction, stretching can also be performed at different temperatures for the front and back surfaces. Here, the stretching temperature is defined as the lower temperature of the film surface. The longitudinal stretching process may be carried out in one stage or multiple stages. The preheating of the unstretched film is often carried out by passing it through a temperature-controlled heating roll, but in some cases, the unstretched film can also be heated using a heater. Also, in order to prevent the film to be stretched from sticking to the roll, a ceramic roll with improved adhesiveness or the like can be used.

[0113] · Transverse stretching As the transverse stretching process, normal transverse stretching can be adopted. That is, normal transverse stretching refers to a stretching method in which both ends in the width direction of the film to be stretched are gripped by clips, and the clips are widened while heating in an oven using a tenter. Regarding the transverse stretching process, for example, the methods described in JP Utility Model Publication No. 62-035817, JP Patent Application Laid-Open No. 2001-138394, JP Patent Application Laid-Open No. 10-249934, JP Patent Application Laid-Open No. 6-270246, JP Utility Model Publication No. 4-030922, and JP Patent Application Laid-Open No. 62-152721 can be used, and these methods are incorporated herein.

[0114] The stretching ratio (transverse stretching ratio) in the width direction of the film in the transverse stretching process is preferably 1.2 to 6 times, more preferably 1.5 to 5 times, and even more preferably 2 to 4 times. Also, when longitudinal stretching is performed, the transverse stretching ratio is preferably larger than the longitudinal stretching ratio. In the transverse stretching process, the stretching temperature can be controlled by blowing air at a desired temperature into the tenter. The film temperature can be the same or different on the front and back surfaces for the same reason as in the longitudinal stretching. The stretching temperature used here is defined as the temperature on the lower side of the film surface. The transverse stretching process can be carried out in one stage or multiple stages. Also, when performing transverse stretching in multiple stages, it can be carried out continuously, or an intermittent stretching can be carried out by providing a zone without width expansion in between. Such transverse stretching can apply, in addition to the normal transverse stretching where the clips are widened in the width direction in the tenter, the following stretching methods where the clips are gripped and widened in the same manner.

[0115] · Diagonal stretching In the diagonal stretching process, similar to the normal transverse stretching, the clips are widened in the transverse direction, but by changing the conveyance speeds of the left and right clips, stretching in the diagonal direction can be achieved. As the diagonal stretching process, for example, the methods described in JP-A-2002-022944, JP-A-2002-086554, JP-A-2004-325561, JP-A-2008-023775, and JP-A-2008-110573 can be used.

[0116] · Simultaneous biaxial stretching Simultaneous biaxial stretching is a process where, similar to the normal transverse stretching, the clips are widened in the transverse direction and at the same time, stretching or contraction is performed in the longitudinal direction. As the simultaneous biaxial stretching, for example, the methods described in JP-U-55-093520, JP-A-63-247021, JP-A-6-210726, JP-A-6-278204, JP-A-2000-334832, JP-A-2004-106434, JP-A-2004-195712, JP-A-2006-142595, JP-A-2007-210306, JP-A-2005-022087, JP-T-2006-517608, and JP-A-2007-210306 can be used.

[0117] · Heat treatment for improving bowing (shaft misalignment) In the above-described transverse stretching process, since the ends of the film are gripped by clips, the deformation of the film due to the thermal shrinkage stress generated during the heat treatment is large at the central part of the film and small at the ends, and as a result, a distribution occurs in the properties in the width direction. If a straight line is drawn along the transverse direction on the surface of the film before the heat treatment process, the straight line on the surface of the film that has passed through the heat treatment process will be in the shape of an arc with the center part concave toward the downstream. This phenomenon is called the bowing phenomenon and is the cause of disturbing the isotropy and the uniformity in the width direction of the film. As an improvement method, preheating before the transverse stretching or heat setting after the stretching can reduce the variation in the orientation angle due to bowing. Either preheating or heat setting may be used, but it is more preferable to perform both. These preheating and heat setting are preferably carried out while gripping with clips, that is, preferably carried out continuously with the stretching.

[0118] The preheating temperature is preferably about 1 to 50 °C higher than the stretching temperature, more preferably 2 to 40 °C higher, and still more preferably 3 to 30 °C higher. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and still more preferably 10 seconds to 2 minutes. During the preheating, it is preferable to keep the width of the tenter substantially constant. Here, "substantially" refers to ±10% of the width of the unstretched film.

[0119] The heat setting temperature is preferably 1 to 50 °C lower than the stretching temperature, more preferably 2 to 40 °C lower, and still more preferably 3 to 30 °C lower. A temperature below the stretching temperature and below the Tg of the liquid crystal polymer is particularly preferable. The heat setting time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and still more preferably 10 seconds to 2 minutes. During the heat setting, it is preferable to keep the width of the tenter substantially constant. Here, "substantially" refers to 0% (the same width as the tenter width after stretching) to -30% (shrinking the width by 30% from the tenter width after stretching) of the tenter width after the stretching end. As other known methods, the methods described in JP-A-1-165423, JP-A-3-216326, JP-A-2002-018948, and JP-A-2002-137286 can be mentioned.

[0120] · Heat relaxation treatment After the stretching step, a heat relaxation treatment may be performed to heat the film to shrink the film. By performing the heat relaxation treatment, the heat shrinkage rate of the polymer film during use of the laminate can be reduced. The heat relaxation treatment is preferably carried out at at least one timing after film formation, after longitudinal stretching, and after transverse stretching. The heat relaxation treatment may be continuously performed online after stretching, or may be performed offline after winding up after stretching. Examples of the temperature of the heat relaxation treatment include a temperature equal to or higher than the glass transition temperature Tg and equal to or lower than the melting point Tm of the liquid crystal polymer. When there is a concern about oxidative degradation of the polymer film, the heat relaxation treatment may be performed in an inert gas such as nitrogen gas, argon gas, or helium gas.

[0121] <Preheating treatment> In Step 1A, in terms of better heat dimensional stability, more specifically, in terms of being able to suppress shrinkage of the film when heated in a later step, after the film is transversely stretched, it is preferable to perform a preheating treatment in which the film is heated while fixing the film width.

[0122] In the preheating treatment, the heat treatment is performed while fixing the film width by a fixing method such as gripping both end portions in the width direction of the film with clips. The film width after the preheating treatment is preferably 85 to 105%, more preferably 95 to 102% of the film width before the preheating treatment. The heating temperature in the preheating treatment is preferably {Tm - 200} °C or higher, more preferably {Tm - 100} °C or higher, and even more preferably {Tm - 50} °C or higher, where the melting point of the liquid crystal polymer is Tm (°C). The upper limit of the heating temperature in the preheating treatment is preferably Tm °C or lower, more preferably {Tm - 2} °C or lower, and even more preferably {Tm - 5} °C or lower. Alternatively, the heating temperature in the preheating treatment is preferably 240 °C or higher, more preferably 255 °C or higher, and even more preferably 270 °C or higher. The upper limit is preferably 315 °C or lower, more preferably 310 °C or lower. Examples of the heating means used for the preliminary heat treatment include a hot air dryer and an infrared heater. Since a film having a desired melting peak area can be produced in a short time, an infrared heater is preferred. In addition, as the heating means, pressurized steam, microwave heating, or a heat medium circulation heating method may be used. The treatment time of the preliminary heat treatment can be appropriately adjusted according to the type of liquid crystal polymer, the heating means, and the heating temperature. When using an infrared heater, 1 to 120 seconds is preferred, and 3 to 90 seconds is more preferred. When using a hot air dryer, 0.5 to 30 minutes is preferred, and 1 to 10 minutes is more preferred.

[0123] <Surface treatment> Since the adhesion between the polymer film and a metal layer such as a copper foil and a copper plating layer or other layers can be further improved, it is preferable to perform a surface treatment on the polymer film. Examples of the surface treatment include glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, and acid or alkali treatment. The glow discharge treatment mentioned here may be a low-temperature plasma occurring under a low-pressure gas of 10 -3 ~20 Torr, and plasma treatment under atmospheric pressure is also preferred. The glow discharge treatment is performed using a plasma-exciting gas. The plasma-exciting gas is a gas that is plasma-excited under the above conditions, and examples thereof include argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, fluorocarbons such as tetrafluoromethane, and mixtures thereof.

[0124] For improving the mechanical properties, thermal dimensional stability, or winding shape of the wound polymer film, it is also useful to perform an aging treatment on the polymer film at a temperature below the Tg of the liquid crystal polymer. In addition, after the film formation step, the polymer film may further be subjected to a step of narrowly pressing the polymer film with a heating roll and / or a stretching step to further improve the smoothness of the polymer film.

[0125] In the above manufacturing method, the case where the polymer film is a single layer has been described. However, the polymer film may have a laminated structure in which a plurality of layers are laminated.

[0126] <Process 1B> When producing a laminate having a resin layer composed of a polymer layer and an adhesion resin layer as the resin layer, it is preferable to perform Process 1B of applying a composition for forming an adhesion resin layer onto the polymer film produced in Process 1A to produce a polymer film with an adhesion resin layer having the polymer film and the adhesion resin layer.

[0127] As Process 1B, for example, there is a process of applying a composition for forming an adhesion resin layer onto at least one surface of the polymer film produced in Process 1A, and drying and / or curing the coating film as necessary to form an adhesion resin layer on the polymer film.

[0128] Examples of the composition for forming an adhesion resin layer include a composition containing components constituting the adhesion resin layer such as the above binder resin, reactive compound, and additive, and a solvent. Since the components constituting the adhesion resin layer are as described above, their descriptions are omitted.

[0129] Examples of the solvent (organic solvent) include ester compounds (e.g., ethyl acetate, n-butyl acetate, and isobutyl acetate), ether compounds (e.g., ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether), ketone compounds (e.g., methyl ethyl ketone, cyclohexanone, cyclopentanone, 2-heptanone, and 3-heptanone), hydrocarbon compounds (hexane, cyclohexane, and methylcyclohexane), and aromatic hydrocarbon compounds (e.g., toluene and xylene).

[0130] The solvent may be used alone or in combination of two or more. The content of the solvent is preferably 0.0005 to 0.02% by mass, more preferably 0.001 to 0.01% by mass, based on the total mass of the composition for forming the adhesion resin layer. The content of the solid content of the composition for forming the adhesion resin layer is preferably 99.98 to 99.9995% by mass, more preferably 99.99 to 99.999% by mass, based on the total mass of the composition for forming the adhesion resin layer. In this specification, the "solid content" of the composition means the components excluding the solvent and water. That is, the solid content of the composition for forming the adhesion resin layer is intended to be the components constituting the adhesion resin layer such as the above binder resin, reactive compound, and additive.

[0131] The method for attaching the composition for forming the adhesion resin layer on the polymer film is not particularly limited. Examples thereof include a bar coating method, a spray coating method, a squeegee coating method, a flow coating method, a spin coating method, a dip coating method, a die coating method, an inkjet method, and a curtain coating method. When drying the composition for forming the adhesion resin layer attached on the polymer film, the drying conditions are not particularly limited. However, the drying temperature is preferably 25 to 200 °C, and the drying time is preferably 1 second to 120 minutes.

[0132] [Step 2] In Step 2, the resin film produced in Step 1 and a metal foil made of the metal constituting the metal layer are laminated, and the resin film and the metal foil are pressure-bonded under high-temperature conditions to produce a laminate having a resin layer and a metal layer. The method and conditions for thermocompression bonding the resin film and the metal foil in Step 2 are not particularly limited and are appropriately selected from known methods and conditions. As the temperature condition for thermocompression bonding, 100 to 300 °C is preferable. As the pressure condition for thermocompression bonding, 0.1 to 20 MPa is preferable. The treatment time for the pressure bonding treatment is preferably 0.001 to 1.5 hours.

[0133] Note that the method for manufacturing the laminate of the present invention is not limited to the method having the above Step 1A, Step 1B, and Step 2. For example, on at least one surface of a surface where the RSm of the metal foil is 1.2 μm or less, the composition for forming an adhesive resin layer used in Step 1B is applied, and if necessary, the coating film is dried and / or cured to form an adhesive resin layer. Then, the metal foil with the adhesive resin layer and the polymer film produced according to the method described in Step 1A are laminated such that the adhesive resin layer is in contact with the polymer film. Next, by thermocompression bonding the metal foil, the adhesive resin layer, and the polymer film according to the method described in Step 2, a laminate having a resin layer and a metal layer can be produced.

[0134] 〔Uses of the laminate〕 Examples of the uses of the laminate include wiring substrates such as laminated circuit boards, flexible laminates, and flexible printed wiring boards (FPC). The laminate is particularly preferably used as a substrate for high-speed communication.

Examples

[0135] The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, treatment details, and treatment procedures shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the present invention is not limited to the embodiments shown in the following examples. Unless otherwise specified, "parts" and "%" are based on mass.

[0136] [Raw materials] <Resin composition for forming a polymer layer> (Liquid crystal polymer) LCP1: A polymer synthesized based on Example 1 of JP-A-2019-116586 (melting point Tm: 320 °C, standard dielectric loss tangent: 0.0012). LCP1 is composed of a repeating unit derived from 6-hydroxy-2-naphthoic acid, a repeating unit derived from 4,4'-dihydroxybiphenyl, a repeating unit derived from terephthalic acid, and a repeating unit derived from 2,6-naphthalenedicarboxylic acid. The standard dielectric loss tangent of LCP1 was measured by the cavity resonator perturbation method using a cavity resonator (CP-531 manufactured by Kanto Electronic Application Development Co., Ltd.) according to the above method.

[0137] (Polyolefin component) PE1: "Novatech (registered trademark) LD" manufactured by Japan Polyethylene Corporation (low density polyethylene) (Compatibilizing component) Compatibilizing component 1: "Bondfast (registered trademark) E" manufactured by Sumitomo Chemical Co., Ltd. (copolymer of ethylene and glycidyl methacrylate (E-GMA copolymer))

[0138] <Metal foil> In each of the examples and comparative examples, as the metal foil, an unroughened copper foil (copper foils 1 to 4) with a thickness of 18 μm and surface RSm values of 0.5 μm, 1.0 μm, 1.8 μm, and 2.2 μm on the unroughened surface were used.

[0139] [Example 1] A laminate having a metal layer and a resin layer was produced by the method shown below.

[0140] [Production of polymer film (Step 1A)] [Supply step] A resin composition for forming a polymer layer consisting only of liquid crystal polymer LCP1 was pelletized using an extruder. The pelletized resin composition was dried for 12 hours using a dehumidifying hot air dryer with a heating temperature of 80°C and a dew point temperature of -45°C. As a result, the water content of the resin composition pellets was made 200 ppm or less. The pellets thus dried are also referred to as raw material A.

[0141] [Film forming step] Raw material A was supplied into the cylinder from the same supply port of a twin-screw extruder with a screw diameter of 50 mm, heated and kneaded, and the molten raw material A was discharged from a die with a die width of 750 mm onto a rotating cast roll in the form of a film and cooled and solidified, and stretched as desired to obtain a polymer film with a thickness of 150 μm. In addition, the temperature of heating and kneading, the discharge speed when discharging raw material A, the clearance of the die lip, and the peripheral speed of the cast roll were adjusted within the following ranges, respectively. · Temperature of heating and kneading: 270 - 350°C · Clearance: 0.01 to 5 mm · Discharge speed: 0.1 to 1000 mm / sec · Peripheral speed of the casting roll: 0.1 to 100 m / min

[0142] <Cross-stretching process> The polymer film produced in the film-forming process was stretched in the TD direction using a tenter. The stretching ratio at this time was 3.2 times.

[0143] <Preliminary heat treatment> The following heat treatment was performed on the obtained polymer film using a hot air dryer. Both ends in the width direction of the polymer film were gripped with jigs, and the polymer film was fixed so as not to shrink in the width direction. The polymer film fixed with the jigs was put into a hot air dryer and heated for 10 seconds under the condition of a film surface temperature of 300 °C, and then the polymer film was taken out from the hot air dryer. In the preliminary heat treatment, a film surface temperature measurement film was installed near the polymer film to be heat-treated, and the film surface temperature of the polymer film was measured using a thermocouple attached with a tape made of a polyimide material on the surface of the film surface temperature measurement film.

[0144] 〔Formation of the adhesion resin layer (Process 1B)〕 Corona treatment was performed on both surfaces of the polymer film subjected to the preliminary heat treatment using a corona treatment apparatus. Next, 17.7 g of a polyimide resin solution (「PIAD-200」manufactured by Arakawa Chemical Industries, Ltd., solid content 30% by mass, solvents: cyclohexanone, methylcyclohexane, and ethylene glycol dimethyl ether), 0.27 g of 4-t-butylphenyl glycidyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), and 1.97 g of cyclohexanone were mixed and stirred to prepare a composition for forming an adhesion resin layer (coating solution 1) with a solid content concentration of 28% by mass. The obtained coating liquid 1 was applied to one surface of the surface-treated polymer film using a bar coater to form a coating film. By drying the coating film under the conditions of 85 °C for 1 hour, an adhesion resin layer with a thickness of 1 μm was provided. Further, in the same manner, a coating film was formed on the surface opposite to the side provided with the adhesion resin layer using the coating liquid 1, and the coating film was dried to provide an adhesion resin layer. Thus, a polymer film (resin film 1) having adhesion resin layers on both sides was produced.

[0145] [Manufacture of laminate (Process 2)] The resin film 1 produced in the above process and the two copper foils 1 were laminated such that the adhesion resin layer of the resin film 1 and the non-roughened treatment surface of the copper foil 1 were in contact with each other. Next, by using a hot press machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.) and crimping under the conditions of 200 °C and 0.4 MPa for 1 hour, a laminate 1 in which a metal layer, an adhesion resin layer, a polymer layer, an adhesion resin layer, and a metal layer were laminated in this order was produced. When the RSm at the interface between the metal layer and the adhesion resin layer in the produced laminate 1 was measured by the above method, it was 0.5 μm in all cases.

[0146] [Example 2] In the supply process, except that a resin composition for forming a polymer layer in which a polyolefin component (12% by mass) and a compatible component 1 (3% by mass) were mixed in addition to the liquid crystal polymer LCP1 was used, the laminate 2 of Example 2 was produced according to the method described in Example 1.

[0147] [Example 3] In the supply process, except that a resin composition for forming a polymer layer in which a polyolefin component (8% by mass) and a compatible component 1 (2% by mass) were mixed in addition to the liquid crystal polymer LCP1 was used, the laminate 3 of Example 3 was produced according to the method described in Example 1.

[0148] [Example 4] In the supply process, except that a resin composition for forming a polymer layer in which a polyolefin component (16% by mass) and a compatible component 1 (4% by mass) were mixed in addition to the liquid crystal polymer LCP1 was used, the laminate 4 of Example 4 was produced according to the method described in Example 1.

[0149] [Example 5] In Step 1B, except that the drying time of the coating film was lengthened, the laminate 5 of Example 5 was produced according to the method described in Example 2.

[0150] [Example 6] In Step 1B, except that the drying time of the coating film was shortened, the laminate 6 of Example 6 was produced according to the method described in Example 2.

[0151] [Example 7] In Step 1B, except that the drying time of the coating film was made even shorter than that of Example 6, the laminate 7 of Example 7 was produced according to the method described in Example 2.

[0152] [Example 8] In Step 2, except that copper foil 2 with an RSm of 1.0 μm on the non-roughened surface was used instead of copper foil 1, the laminate 8 of Example 8 was produced according to the method described in Example 2. When the RSm of the interface between the metal layer and the polymer layer in the produced laminate 8 was measured by the above method, all were 1.0 μm.

[0153] [Comparative Example 1] In Step 2, except that copper foil 3 with an RSm of 1.8 μm on the non-roughened surface was used instead of copper foil 1, the laminate C1 of Comparative Example 1 was produced according to the method described in Example 2. When the RSm of the interface between the metal layer and the polymer layer in the produced laminate C1 was measured by the above method, all were 1.8 μm.

[0154] [Comparative Example 2] In the supply process, a laminate C2 of Comparative Example 2 was produced according to the method described in Example 1, except that in addition to the liquid crystal polymer LCP1, a resin composition for forming a polymer layer in which a polyolefin component (37.5% by mass) and a compatible component 1 (12.5% by mass) were mixed was used.

[0155] [Comparative Example 3] A laminate C3 of Comparative Example 3 was produced according to the method described in Example 1, except that a commercially available polymer film ("CT-Q" manufactured by Kuraray Co., Ltd., thickness 50 μm) was used instead of the polymer film produced by Step 1A.

[0156] [Comparative Example 4] A commercially available polymer film ("CT-Q" manufactured by Kuraray Co., Ltd., thickness 50 μm) and two copper foils 4 having an RSm of 2.2 μm on the non-roughened surface were laminated so that the non-roughened surfaces of the polymer film and the copper foil 4 were in contact with each other. Then, a laminate C4 of Comparative Example 4 in which a metal layer, a polymer layer, and a metal layer were laminated in this order was produced by pressure bonding at 200 °C and 0.4 MPa for 1 hour using a hot press machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.). When the RSm at the interface between the metal layer and the polymer layer in the produced laminate C4 was measured by the above method, it was 2.2 μm in all cases.

[0157] [Measurement of Resin Layer] The following measurements were performed on the resin films (corresponding to the resin layers in the laminates) produced by the manufacturing methods of the above examples.

[0158] [Solvent Content of Adhesive Resin Layer] The content of the solvent remaining in the adhesive resin layer formed on the surface of the resin film was determined by quantifying the outgas volatilized from the adhesive resin layer using a gas chromatograph mass spectrometer [manufactured by Shimadzu Corporation, model: QP2010Ultra] connected to a thermal desorber [manufactured by Nippon Analytical Industry Co., Ltd., model: JTD5053]. Table 1 described later shows the content of the solvent with respect to the total mass of the adhesive resin layer (unit: mass ppm).

[0159] <Elastic modulus of the adherent resin layer> After laminating a fluororesin sheet on the surface of the resin film produced in each example, it was heated at 200 °C and 4 MPa for 1 hour using a hot press machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to obtain a cured film (resin layer). After peeling off the fluororesin sheet, the indentation elastic modulus of the cured film was measured by the nanoindentation method. The measurement was performed using a Berkovich indenter, and the indentation depth at the maximum load was set to 1 / 10 of the thickness of the cured film. Using a film hardness meter: Fisherscope HM500 (manufactured by Fisher Instruments Co., Ltd.), under the conditions of a loading time of 10 seconds and an unloading time of 10 seconds, 10 measurements were made for each, and the arithmetic mean value of the 10 measurements was taken as the elastic modulus after curing. The higher the elastic modulus of the adherent resin layer, the more the distortion of the wiring board generated when manufacturing a wiring board using the laminate is suppressed. In addition, when the elastic modulus was measured for sample A consisting only of the resin layer, which was produced from each laminate according to the method described in the evaluation of crackability described later, the measured value of the indentation elastic modulus of sample A and the measured value of the indentation elastic modulus of the above cured film were the same in each example.

[0160] <Dielectric tangent of the resin layer> The center part of the resin film produced in each example was sampled, and using a split cylinder type resonator (CR-728 manufactured by Kanto Electron Application Development Co., Ltd.) and a network analyzer (Keysight N5230A), the dielectric tangent in the frequency band of 28 GHz was measured in an environment of a temperature of 23 °C and a humidity of 50% RH.

[0161] <Polyolefin dispersed phase> The cross-section in the thickness direction of the resin film was observed using a scanning electron microscope (SEM: Scanning Electron Microscope) by the following method. The presence or absence of the formation of the polyolefin dispersed phase in the polymer layer was confirmed from the obtained observation image, and when the dispersed phase was formed, the average dispersion diameter of the dispersed phase was determined. At 10 different positions of different parts of the sample, a cross-section parallel to the width direction of the resin film and perpendicular to the film surface, and a cross-section perpendicular to the width direction and perpendicular to the film surface were observed, and a total of 20 observation images were obtained. The observation was performed at an appropriate magnification of 100 to 100,000 times, and photography was performed so that the dispersion state of the particles (dispersed phase formed by polyolefin) in the width of the total thickness of the film could be confirmed. For 200 particles randomly selected from each of the 20 images, the outer periphery of each particle was traced, and the equivalent circle diameter of the particles was measured from these traced images using an image analysis device to obtain the particle size. The average value of the particle sizes measured from each photographed image was defined as the average dispersion diameter of the dispersed phase.

[0162] [Evaluation of the laminate] The following evaluation tests were performed on the laminates produced by the manufacturing methods of the above examples.

[0163] [Transmission characteristics] Samples for evaluating the transmission characteristics having a transmission line with a microstrip line structure were produced from each laminate by the method shown below. Each laminate was cut into a size of 15 cm × 15 cm to produce a base material for the transmission characteristic evaluation sample, and a microstrip line transmission line was formed on the produced base material. The microstrip line transmission line was formed by laminating a mask layer on one metal layer of each laminate, exposing the mask layer so that the pattern of the microstrip line transmission line could be formed, removing the unnecessary portions of the mask to form a mask pattern, and immersing the surface of the metal layer on which the mask pattern was laminated in a 40% aqueous solution of iron(III) chloride (manufactured by Fujifilm Wako Pure Chemical Corporation, Grade 1) to dissolve the metal layer by etching treatment. The size of the microstrip line transmission line was 10 cm in length and 105 μm in width. In this way, a microstrip line transmission line was obtained in which a signal line of the metal layer was formed on one surface and the surface of the other metal layer was grounded.

[0164] For the sample prepared by the above method, using a split cylinder resonator ("CR-728" manufactured by Kanto Electronic Application Development Co., Ltd.) and a network analyzer (Keysight N5230A), the transmission loss (S21 parameter, unit: dB / cm) in the frequency band of 28 GHz was measured in an environment of 23°C and 50% RH.

[0165] <Adhesion> Each laminate was cut into strips of 1 cm × 5 cm to prepare samples for adhesion evaluation. The peel strength (unit: kN / m) of the obtained samples was measured according to the method for measuring the peel strength of flexible printed wiring boards described in JIS C 5016-1994. The adhesion measurement test was carried out using a tensile testing machine (Digital Force Gauge ZP-200N manufactured by IMADA Co., Ltd.) to peel the copper foil at a peel rate of 50 mm per minute in a direction forming a 90° angle with respect to the copper foil removal surface. The adhesion between the metal layer and the resin layer was evaluated based on the value measured by the tensile testing machine.

[0166] <Crackability> The laminate was immersed in an aqueous solution of 40% iron(III) chloride (manufactured by Wako Pure Chemical Industries, Ltd., grade 1), and the metal layer was dissolved by etching treatment to prepare sample A (size 100 mm × 100 mm) consisting only of the resin layer. Then, according to the method described in JIS K 7161-1:2014, using a tensilon testing machine [manufactured by Toyo Seiki Seisakusho Co., Ltd., Strograph VE50], the stress when both ends of the obtained sample A were stretched along the longitudinal direction was measured in an environment of 23°C, and the tensile elastic modulus (unit: GPa) was measured. Based on the obtained tensile elastic modulus, the crackability (ease of cracking) of the resin layer was evaluated. The lower the tensile elastic modulus measured by the above method, the easier the resin layer is to crack, and the higher the tensile elastic modulus measured by the above method, the more difficult the resin layer is to crack.

[0167] [Results] Table 1 below shows the composition of each layer constituting the laminate manufactured in each example and each comparative example, and the evaluation results of each laminate. The "Resin Composition" column in Table 1 shows the type and composition of the resin composition for forming the polymer layer used in each example. The "Coating Solution" column in Table 1 shows the type and composition of the resin composition for forming the adhesion resin layer used in each example. In the "Thickness" column and "Solvent Content" column of the "Adhesion Resin Layer" in Table 1, "-" means that there is no adhesion resin layer. The "Average Dispersion Diameter of Dispersed Phase" column in Table 1 shows the average dispersion diameter (unit: μm) of the polyolefin dispersed phase in each resin film measured by the above method.

[0168] [Table 1]

[0169] From the results shown in the above table, it was confirmed that the problems of the present invention can be solved by the laminate of the present invention.

Claims

1. A laminate having a metal layer and a resin layer in contact with at least one surface of the metal layer, wherein the dielectric tangent of the resin layer at a temperature of 23 ° C and a frequency of 28 GHz is less than 0.002, in a cross section along the thickness direction, the average length RSm of the roughness curve elements of the interface between the metal layer and the resin layer is 1.2 μm or less, the resin layer has, in this order from the metal layer side, an adhesion resin layer and a polymer layer containing a liquid crystal polymer, the thickness of the polymer layer is 5 to 1000 μm, and the thickness of the adhesion resin layer is 1 μm or less.

2. The laminate according to claim 1, wherein the ratio of the thickness of the adhesion resin layer to the thickness of the polymer layer is 0.1 to 2%.

3. The laminate according to claim 2, wherein the liquid crystal polymer contains two or more repeating units derived from dicarboxylic acids.

4. The laminate according to claim 2 or 3, wherein the liquid crystal polymer has at least one selected from the group consisting of a repeating unit derived from 6-hydroxy-2-naphthoic acid, a repeating unit derived from an aromatic diol, a repeating unit derived from terephthalic acid, and a repeating unit derived from 2,6-naphthalenedicarboxylic acid.

5. The laminate according to any one of claims 1 to 4, wherein the polymer layer contains a polyolefin.

6. The laminate according to claim 5, wherein the content of the polyolefin is 0.1 to 40% by mass based on the total mass of the polymer layer.

7. In the polymer layer, a dispersed phase containing the polyolefin is formed, and in an observation image obtained by observing a cross section along the thickness direction of the polymer layer, the average dispersed diameter of the dispersed phase is 0.01 to 10 μm.

8. The laminate according to any one of claims 1 to 7, wherein the elastic modulus of the adhesion resin layer is 0.8 GPa or more.

9. The laminate according to any one of claims 1 to 8, wherein the content of the solvent contained in the adhesion resin layer is 0 to 200 mass ppm with respect to the total mass of the adhesion resin layer.

10. The laminate according to any one of claims 1 to 9, wherein the metal layer is a copper layer.

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