Polymer film, laminate

Abstract

To provide a polymer film excellent in adhesion between a polymer film and metal foil when bonding metal foils to prepare a laminate and excellent in the suppression performance of positional deviation in wiring formed of the metal foil even when further laminating the laminate on the wiring, and a laminate.SOLUTION: A polymer film includes a liquid crystal polymer. When in a cross section in the thickness direction of the polymer film, setting an elastic modulus at a position A in a distance having the half thickness of the polymer film from one surface of the polymer film toward the other surface to an elastic modulus A and setting an elastic modulus at a position B in a distance having the one eighth thickness of the polymer film from the one surface of the polymer film toward the other surface to an elastic modulus B, a ratio B / A of the elastic modulus B to the elastic modulus A is 0.99 or less, and the elastic modulus A is 4.0 GPa or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polymer film and 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 the 5G mobile communication system, low dielectric tangent and low water absorption are required from the viewpoint of reducing transmission loss in the high-frequency band, and development using various materials is underway.

[0003] For example, Patent Document 1 describes a liquid crystal polymer film made of a thermoplastic polymer capable of forming an optically anisotropic molten phase, a thermoplastic liquid crystal polymer film in which the change rate of the relative permittivity before and after heating the film satisfies a specific relationship, and a laminate including a film layer made of the thermoplastic liquid crystal polymer film and a metal layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When a laminate having the above-described polymer film and metal layer is used in the manufacture of a high-frequency circuit board, after a circuit made of metal wiring is formed on the surface of the film layer, another laminate is further laminated to manufacture a circuit board having a multilayer structure. The inventors have found that there is still room for further improvement in the adhesion between a polymer film and a metal foil when a laminate is produced by laminating the metal foil, and in the displacement of wiring formed from the metal foil when a laminate is further laminated on the wiring.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a polymer film that has excellent adhesion between a polymer film and a metal foil when a laminate is produced by laminating the metal foil, and also has excellent performance in suppressing displacement of wiring when a laminate is further laminated on the wiring formed from the metal foil. Another object of the present invention is to provide a laminate having the above polymer film and a metal-containing layer.

Means for Solving the Problems

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

[0008] 〔1〕 A polymer film containing a liquid crystal polymer, wherein in a cross section along the thickness direction of the polymer film, the elastic modulus at position A, which is at a distance of half the thickness of the polymer film from one surface of the polymer film toward the other surface, is defined as elastic modulus A, and the elastic modulus at position B, which is at a distance of 1 / 8 of the thickness of the polymer film from one surface of the polymer film toward the other surface, is defined as elastic modulus B, the ratio B / A of the elastic modulus B to the elastic modulus A is 0.99 or less, and the elastic modulus A is 4.0 GPa or more. 〔2〕 The polymer film according to 〔1〕, wherein the elastic modulus A is 4.6 GPa or more. 〔3〕 The polymer film according to 〔1〕 or 〔2〕, which has a single-layer structure. 〔4〕 The polymer film according to any one of 〔1〕 to 〔3〕, wherein the dielectric tangent of the polymer film at a temperature of 23°C and a frequency of 28 GHz is 0.0022 or less. 〔5〕The polymer film according to any one of 〔1〕~〔4〕, wherein the liquid crystal polymer contains at least one selected from the group consisting of repeating units derived from p-hydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid. 〔6〕A laminate having the polymer film according to any one of 〔1〕~〔5〕 and at least one metal-containing layer. 〔7〕The laminate according to 〔6〕, having at least two of the metal-containing layers, wherein the metal-containing layers, the polymer film, and the metal-containing layers are laminated in this order. 〔8〕The laminate according to 〔6〕 or 〔7〕, wherein the thickness of the metal-containing layer is 5 to 30 μm.

Advantages of the Invention

[0009] According to the present invention, when a laminate is produced by laminating a metal foil, a polymer film excellent in adhesion between the polymer film and the metal foil can be provided, and when a laminate is further laminated on a wiring formed from the metal foil, excellent performance in suppressing displacement of the wiring can also be provided.

Brief Description of the Drawings

[0010]

Figure 1

Embodiments for Carrying Out the Invention

[0011] 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. In the present specification, the “organic group” means a group containing at least one carbon atom.

[0012] In this specification, when the polymer film or laminate is in a long shape, the length direction means the longitudinal direction of the polymer film or laminate and the MD (machine direction), and the width direction means the direction perpendicular to the length direction in the plane of the polymer film or laminate (the short side direction and the TD (transverse direction)). In this specification, each component may be used alone as one kind of the 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 refers to 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 polymer film or the liquid crystal polymer contained in the polymer film 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".

[0013] [Polymer Film] The polymer film according to the present invention contains a liquid crystal polymer and has different predetermined elastic modulus characteristics at positions in the thickness direction.

[0014] [Elastic Modulus Characteristics] In the cross-section along the thickness direction of the polymer film according to the present invention, when the elastic modulus at position A, which is at a distance of half of the thickness of the polymer film from one surface of the polymer film to the other surface, is defined as elastic modulus A, and the elastic modulus at position B, which is at a distance of 1 / 8 of the thickness of the polymer film from one surface of the polymer film to the other surface, is defined as elastic modulus B, the ratio B / A of elastic modulus B to elastic modulus A (hereinafter, also referred to as the "specific elastic modulus ratio") is 0.99 or less, and elastic modulus A is 4.0 GPa or more. Although the detailed mechanism by which the polymer film containing a liquid crystal polymer has a predetermined specific elastic modulus ratio and elastic modulus A to solve the problems of the present invention has not been clarified, the inventors speculate as follows. That is, when the elastic modulus A at the center in the thickness direction of the polymer film is equal to or greater than a predetermined value, the relative displacement in the in-plane direction of the metal-containing layers disposed on both surfaces of the polymer film is suppressed, and it is speculated that the in-plane displacement of the wiring is prevented even when another laminate is laminated on the wiring. Further, when the specific elastic modulus ratio is equal to or less than a predetermined value, while maintaining the elastic modulus of the entire polymer film, the elastic modulus becomes relatively low at the position B near the surface layer, and as a result, it is speculated that the adhesion to the metal-containing layer laminated on the polymer film is improved. In this way, it is considered that a polymer film excellent in the adhesion between the polymer film and the metal foil in the laminate with the metal foil and excellent in the performance of suppressing the displacement of the wiring even when a laminate is further laminated on the wiring formed from the metal foil can be obtained.

[0015] In addition, in this specification, for a laminate produced by laminating a metal foil on a polymer film, when the adhesion between the polymer film and the metal foil is more excellent and / or the performance of suppressing the displacement of the wiring is more excellent when a laminate is further laminated on the wiring formed from the metal foil, it is also described that "the effect of the present invention is more excellent".

[0016] The elastic modulus A at the position A of the polymer film is preferably 4.3 GPa or more, more preferably 4.6 GPa or more, in terms of the more excellent effect of the present invention. The upper limit value is not particularly limited, for example, it is 5.0 GPa or less. Further, the specific elastic modulus ratio, which is the ratio B / A of the elastic modulus B to the elastic modulus A, is preferably 0.99 or less, more preferably 0.98 or less, still more preferably 0.96 or less, in terms of the more excellent effect of the present invention. The lower limit value is not particularly limited, but since the displacement tends to increase when another laminate is laminated if the specific elastic modulus ratio is too small, 0.80 or more is preferably, more preferably 0.85 or more. The elastic modulus B at position B of the polymer film is preferably 3.7 to 4.95 GPa, more preferably 3.9 to 4.8 GPa, in terms of more excellent effects of the present invention.

[0017] The elastic modulus in the cross-section of the polymer film is the indentation elastic modulus measured using a nanoindenter in accordance with ISO14577, and the specific measurement method will be described in the examples below. The elastic modulus (elastic moduli A and B) of the polymer film can be adjusted, for example, in the film-forming process by performing a heat treatment and / or a cooling treatment on the polymer film that exceeds the melting point Tm of the liquid crystal polymer and changing those conditions (heating temperature, cooling rate, etc.) to control the orientation and crystallization structure in the thickness direction of the polymer film. The specific elastic modulus ratio of the polymer film can be adjusted, for example, by performing a specific heat treatment described below in the film-forming process of the polymer film, or by performing heating and cooling similar to the specific heat treatment described below on the polymer film after production to control the orientation and crystallization structure in the thickness direction of the polymer film.

[0018] 〔Components〕 Hereinafter, the components contained in the polymer film will be described in detail.

[0019] <Liquid crystal polymer> The liquid crystal polymer contained in the polymer film of the present invention 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 an 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, and 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.

[0024] 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 it is more preferable to have 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.

[0025] 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.

[0026] 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 liquid crystal polymers include "Raplos" 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., "Zyex" 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), which is an optional component, in the polymer film. This also applies to components other than the liquid crystal polymer.

[0027] In terms of being able to easily manufacture a polymer film with a low standard dielectric loss tangent (preferably 0.0022 or less), the standard dielectric loss tangent of the liquid crystal polymer is preferably 0.002 or less, more preferably 0.0015 or less, and even 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 polymer film contains two or more types of liquid crystal polymers, the "dielectric loss tangent of the liquid crystal polymer" means the mass average value of the dielectric loss tangents of the two or more types of liquid crystal polymers.

[0028] The standard dielectric loss tangent of the liquid crystal polymer contained in the polymer film can be measured by the following method. First, immerse it in an organic solvent (e.g., pentafluorophenol) 1000 times the total mass of the polymer film, 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, and correct the influence of the voids in the PTFE tube with Bruggeman's formula and the porosity to obtain the standard dielectric loss tangent of the liquid crystal polymer. The 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 tube. Next, the weight of the tube before and after filling with the precipitate is measured to obtain the mass of the filled precipitate, and then 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 liquid crystal polymer, the value of the dielectric loss tangent described as the catalog value of the commercially available product may be used.

[0029] As the liquid crystal polymer, in terms of more excellent heat resistance, the melting point Tm (unit: °C) 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 (for example, "DSC-60A" manufactured by Shimadzu Corporation). When using a commercially available liquid crystal polymer, the melting point Tm described as the catalog value of the commercially available product may be used.

[0030] 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 conversion value of standard polystyrene by gel permeation chromatography (GPC). The GPC measurement can be carried out under the following apparatus and conditions. The measuring device used is the "HLC (registered trademark)-8320GPC" manufactured by Tosoh Corporation, and two columns of "TSKgel (registered trademark) SuperHM-H (6.0 mm ID × 15 cm, manufactured by Tosoh Corporation)" are used. The solvent (eluent) for dissolving the liquid crystal polymer is not particularly limited, and examples thereof include a mixed solution of pentafluorophenol / chloroform = 1 / 2 (mass ratio). As the measurement conditions, the sample concentration is 0.03% by mass, the flow rate is 0.6 ml / min, the sample injection volume is 20 μL, and the measurement temperature is 40°C. Detection is performed using an RI (differential refractive index) detector. The calibration curve is prepared from eight samples of "Standard Sample TSK standard, polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0031] The polymer film may contain a single type of liquid crystal polymer or two or more types of liquid crystal polymers. 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 based on the total mass of the polymer film. Note that the content of the liquid crystal polymer and the components described below in the polymer film can be measured by known methods such as infrared spectroscopy and gas chromatography-mass spectrometry.

[0032] <Optional component> The polymer film may contain optional components other than the above polymers. Examples of the optional components include polyolefins, compatibilizing components, heat stabilizers, and additives described below.

[0033] (Polyolefin) The polymer film may contain a polyolefin. In this specification, "polyolefin" is intended to mean a polymer (polyolefin resin) having repeating units derived from olefins. The polymer film preferably contains a liquid crystal polymer and a polyolefin, and more preferably contains a liquid crystal polymer, a polyolefin and a compatibilizing component.

[0034] 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 Nippon Zeon Co., Ltd., 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).

[0035] The polyolefin may also 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 which is the above copolymer include 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 more preferably does not contain a 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 does not substantially 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.

[0036] As the polyolefin, polyethylene, COP, or COC is preferable, polyethylene is more preferable, and low-density polyethylene (LDPE) is still more preferable.

[0037] The polyolefin may be used alone or in combination of two or more. When the polymer film contains a polyolefin, its content is preferably 0.1% by mass or more, more preferably 5% by mass or more, based on the total mass of the polymer film, in terms of the surface properties of the polymer film being more excellent. The upper limit is not particularly limited, but in terms of the smoothness of the polymer film being more excellent, it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less, based on the total mass of the polymer film. 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.

[0038] (Compatible component) Examples of the compatible component include a polymer having a portion with high compatibility or 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 end 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 compatible component, a copolymer having a portion with high compatibility or affinity for the polyolefin is preferable. Also, when the polymer film contains a polyolefin and a compatible component, as the compatible component, a reactive compatibilizer is preferable in terms of being able to finely disperse the polyolefin. Note that the compatible component (especially the reactive compatibilizer) may form a chemical bond with a component such as a liquid crystal polymer in the polymer film.

[0039] Examples of the reactive compatibilizer include, for example, 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.

[0040] Examples of the epoxy group-containing polyolefin copolymer include, for example, an ethylene / glycidyl methacrylate copolymer, an ethylene / glycidyl methacrylate / vinyl acetate copolymer, an ethylene / glycidyl methacrylate / methyl acrylate copolymer, a polystyrene graft copolymer onto an ethylene / glycidyl methacrylate copolymer (EGMA-g-PS), a polymethyl methacrylate graft copolymer onto an ethylene / glycidyl methacrylate copolymer (EGMA-g-PMMA), and an acrylonitrile / styrene graft copolymer onto an ethylene / glycidyl methacrylate copolymer (EGMA-g-AS). Examples of commercially available products of the epoxy group-containing polyolefin copolymer 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 NOF Corporation.

[0041] Examples of the epoxy group-containing vinyl copolymer 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).

[0042] Examples of the maleic anhydride-containing polyolefin copolymer include maleic anhydride grafted polypropylene (PP-g-MAH), maleic anhydride grafted ethylene / propylene rubber (EPR-g-MAH), and maleic anhydride grafted ethylene / propylene / diene rubber (EPDM-g-MAH). Examples of commercially available maleic anhydride-containing polyolefin copolymers include the Orevac G series manufactured by Arkema; and the FUSABOND E series manufactured by The Dow Chemical Company.

[0043] Examples of the maleic anhydride-containing vinyl copolymer include maleic anhydride grafted polystyrene (PS-g-MAH), maleic anhydride grafted styrene / butadiene / styrene copolymer (SBS-g-MAH), maleic anhydride grafted 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 Tough Tech M series (SEBS-g-MAH) manufactured by Asahi Kasei Corporation.

[0044] 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.

[0045] 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.

[0046] When the polymer film 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 film.

[0047] (Heat stabilizer) The polymer film 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 polymer film surface. Examples of heat stabilizers include phenolic stabilizers and amine stabilizers having a radical scavenging action; phosphite stabilizers and sulfur stabilizers having a peroxide decomposing action; and hybrid stabilizers having a radical scavenging action and a peroxide decomposing action.

[0048] 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.; and 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.

[0049] 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 a more excellent heat stabilization effect. On the other hand, in terms of electrical properties, a semi-hindered phenol stabilizer or a phosphite stabilizer is more preferable.

[0050] The heat stabilizer may be used alone or in combination of two or more. When the polymer film 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 film.

[0051] (Additive) The polymer film may contain additives other than the above components. Examples of the additives include plasticizers, lubricants, inorganic particles and organic particles, and UV absorbers.

[0052] Plasticizers 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 polymer film. Lubricants include fatty acid esters and metal soaps (e.g., 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 film. The polymer film may contain inorganic particles and / or organic particles as a reinforcing material, a matting agent, a dielectric constant, or a dielectric loss tangent improver. 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 film. UV absorbers 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 film.

[0053] In addition, the polymer film may contain a polymer component other than the liquid crystal polymer. Examples of the polymer component include thermoplastic polymers such as polyethylene terephthalate, modified polyethylene terephthalate, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, and polyester ether ketone.

[0054] <Physical Properties of Polymer Film> (Thickness) The thickness of the polymer film is preferably 5 to 1000 μm, more preferably 10 to 500 μm, and even more preferably 20 to 300 μm. Note that the thickness of the polymer film is the arithmetic mean value of the measured values obtained by measuring the thickness of the polymer film at 100 arbitrarily different points from the observation image obtained by observing a cross-section along the thickness direction of the laminate using a scanning electron microscope (SEM).

[0055] (Dielectric properties) The standard dielectric tangent of the polymer film is not particularly limited, and is, for example, 0.0025 or less, preferably 0.0022 or less, more preferably 0.0020 or less, even more preferably 0.0015 or less, and particularly preferably 0.001 or less. The lower limit is not particularly limited and may be 0.0001 or more. The relative permittivity of the polymer film varies depending on its use, but is preferably 2.0 to 4.0, and more preferably 2.5 to 3.5. The dielectric properties including the standard dielectric tangent and relative permittivity of the polymer film can be measured by the cavity resonator perturbation method. The specific measurement method of the dielectric properties of the polymer film will be described in the Examples section below.

[0056] The polymer film may have a single-layer structure or a laminated structure in which a plurality of layers are laminated. Note that the polymer film having a "single-layer structure" means that the polymer film is composed of the same material throughout its thickness.

[0057] [Manufacturing method of polymer film] The manufacturing method of the polymer film is not particularly limited as long as it can manufacture the polymer film having the elastic modulus characteristics of the present invention, but it is preferable to manufacture the polymer film by inflation molding. More specifically, there is a manufacturing method having a pelletizing step of kneading the components constituting the above-mentioned polymer film to obtain pellets, and a film-forming step of forming a polymer film by inflation molding using the molten resin formed from the above pellets, and a method of performing a specific heat treatment described later in the film-forming step can be mentioned. Hereinafter, the steps for producing a polymer film containing a liquid crystal polymer will be described in detail.

[0058] <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. For the purpose of stabilizing film formation or uniformly dispersing additives (meaning components other than liquid crystal polymers; the same applies hereinafter), one or more raw materials (meaning at least one of polymers and additives; the same applies hereinafter) can be kneaded using an extruder and pelletized, and the obtained pellets can be used.

[0059] (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.

[0060] (3) Raw Material Feeding Method The raw material feeding 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.

[0061] (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 can be implemented alone or in combination.

[0062] (5) Temperature The kneading temperature is preferably below the thermal decomposition temperature of the liquid crystal polymer and the additives, and it is preferably as low as possible within the range where the load of the extruder and the decrease in uniform kneading property do not cause problems.

[0063] (6) Pressure The kneading resin pressure during pelletization is preferably carried out at 0.05 - 30 MPa. In the case of resins that are likely to generate coloring or gels due to shear, it is preferable to apply an internal pressure of about 1 - 10 MPa in the extruder to fill the resin raw material in the twin-screw extruder.

[0064] (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 also be carried out by the underwater cutting method of directly extruding into water from a die while cutting, or the hot cutting method of cutting while in a hot state.

[0065] (8) Pellet size The pellet size preferably has a cross-sectional area of 1 - 300 mm 2 and a length of 1 - 30 mm, more preferably a cross-sectional area of 2 - 100 mm 2 and a length of 1.5 - 10 mm.

[0066] (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 the appearance to deteriorate due to air bubbles mixing into the polymer film or a decrease in haze, but may also cause a decrease in physical properties due to the cleavage of the molecular chains of the liquid crystal polymer, or roll fouling due to the generation of monomers or oligomers. Also, depending on the type of liquid crystal polymer used, in some cases, the generation of oxidation cross-linked products during melt film formation can be suppressed by removing dissolved oxygen by drying.

[0067] (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 the heating method include pressurized steam, heater heating, far-infrared irradiation, microwave heating, and a heat medium circulation heating method.

[0068] <Film forming process> Hereinafter, as the film forming process, a process of forming a polymer film by inflation molding using pellets containing a liquid crystal polymer will be described.

[0069] (Extrusion conditions) · Raw material drying Even in the melting and plasticizing process of 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.

[0070] · Raw material supply method When there are multiple types of raw materials (pellets) fed from the supply port of the extruder, they may be premixed in advance (premix method), separately fed into the extruder at a certain ratio, or a method combining both may be used. Also, in order to stabilize extrusion, it is generally practiced to reduce the fluctuations in the temperature and bulk specific gravity of the raw materials fed 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, and in the case of an amorphous state, it is preferably in the range of {glass transition temperature (Tg) (°C) - 150 °C} to {Tg (°C) - 1 °C}, and in the case of a crystalline resin, it is preferably in the range of {melting point (Tm) (°C) - 150 °C} to {Tm (°C) - 1 °C}, and heating or heat preservation of the raw materials is performed. Also, from the viewpoint of plasticization efficiency, the bulk specific gravity of the raw material 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 material 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 material to make it pseudo-pelletized.

[0071] · Atmosphere during extrusion The atmosphere during melt extrusion needs to prevent heat and oxidative degradation as much as possible within a range that does not interfere with uniform dispersion, similar to the pelletization process. Injecting an inert gas (such as nitrogen), using a vacuum hopper to lower the oxygen concentration in the extruder, and providing a vent port in the extruder to perform depressurization with a vacuum pump are also effective. These depressurization and injection of inert gas can be carried out independently or in combination.

[0072] · Rotational speed The rotational speed of the extruder is preferably 5 to 300 rpm, more preferably 10 to 200 rpm, and even more preferably 15 to 100 rpm. If the rotational speed is above the lower limit value, the residence time becomes short, the decrease in molecular weight due to thermal degradation can be suppressed, and discoloration can be suppressed. If the rotational speed is 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 thermal degradation due to extended residence time.

[0073] · Temperature Barrel temperature (supply 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 at the target temperature T °C using an extruder, the metering section temperature T3 is set to T ± 20 °C considering the shear heat generation. At this time, T2 is set within the range of T3 ± 20 °C considering the extrusion stability and the thermal decomposability of the resin. T1 is generally set to {T2 (°C) - 5 °C} to {T2 (°C) - 150 °C}, and the optimal value is selected in terms of ensuring the friction between the resin and the barrel, which serves as the driving force (feed force) for sending the resin, and achieving preheating at the feed section. In the case of a normal extruder, it is possible to set the temperature by subdividing each zone of T1 to 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 where melting and mixing are performed at a relatively high temperature in the front half of the extruder and the resin temperature is lowered in the latter half is effective.

[0074] · Pressure The resin pressure inside 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 inside the extruder is 1 MPa or more, the filling rate of the melt inside the extruder is sufficient, so it is possible to suppress the destabilization of the extrusion pressure and the generation of foreign substances due to the occurrence of a stagnant portion. Also, if the pressure inside the extruder is 50 MPa or less, it is possible to suppress the excessive shear stress received inside the extruder, so it is possible to suppress thermal decomposition due to the rise in the resin temperature.

[0075] · 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 from 10 seconds to 60 minutes, more preferably from 15 seconds to 45 minutes, and even more preferably from 30 seconds to 30 minutes. If the residence time is 10 seconds or more, sufficient melt plasticization and dispersion of the additive will be achieved. If the residence time is 30 minutes or less, it is preferable in terms of suppressing resin deterioration and resin discoloration.

[0076] (Filtration) · Type, installation purpose, structure In order to prevent damage to the gear pump caused by foreign matter contained in the raw material and to extend the life of the fine-pore filter 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.

[0077] · Mesh size, filtration area The mesh size is preferably 40 to 800 mesh, more preferably 60 to 700 mesh, and even more preferably 100 to 600 mesh. If the mesh size is 40 mesh or more, it is possible to sufficiently suppress foreign matter from passing through the mesh. Also, if it is 800 mesh or less, it is possible to suppress the improvement of the filtration pressure increase speed and reduce the mesh replacement frequency. Also, filter meshes are often used by overlapping multiple types with different mesh sizes in terms of filtration accuracy and strength retention. 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 aperture ratio of the breaker plate used is often 30 to 80% in terms of filtration efficiency and strength. Also, for the screen changer, one having the same diameter as the barrel diameter of the extruder is often used, but in order to increase the filtration area, a tapered pipe is used to use a larger-diameter filter mesh, or the flow path may be branched to use a plurality of breaker plates. The filtration area is 0.05 to 5 g / cm of the flow rate per second 2It is preferably selected based on this, 0.1 to 3 g / cm 2 is more preferable, 0.2 to 2 g / cm 2 is even more preferable. When the filter clogs and the filtration pressure rises by capturing foreign substances. In that case, it is necessary to stop the extruder and replace the filter, but a type that can replace the filter while continuing extrusion can also be used. Further, as a measure against the increase in filtration pressure due to foreign substance capture, a filter having a function of reducing the filtration pressure by washing and removing the foreign substances captured by the filter in the reverse direction of the polymer flow path can also be used.

[0078] (Inflation molding) Hereinafter, an example of an embodiment of a manufacturing method for manufacturing the polymer film of the present invention by inflation molding will be described while exemplifying a specific manufacturing apparatus. The manufacturing method of the polymer film of the present invention is not limited to the following embodiments, but it is preferable to manufacture the polymer film by the method according to this embodiment in terms of easy manufacturing of the polymer film having the above elastic modulus characteristics.

[0079] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a manufacturing apparatus used for manufacturing a polymer film by inflation molding. The film manufacturing apparatus 10 shown in FIG. 1 includes an annular die 12 having an annular slit, a cooling blower 14, a heater 16, and a cooler 18. In the film manufacturing apparatus 10, the annular die 12, the cooling blower 14, the heater 16, and the cooler 18 are arranged in this order from the vertically lower side. Further, the film manufacturing apparatus 10 is configured such that gas is supplied into the internal space of the molten cylindrical film F extruded from the annular die 12.

[0080] The annular die 12 is continuously supplied with a molten liquid crystal polymer from an extruder (not shown). The supplied molten liquid crystal polymer passes through the annular slit of the annular die 12 and is extruded vertically upward as a cylindrical film F. The extruded cylindrical film F expands due to the air supplied therein and its diameter increases, and is cooled by a cooling air flow ejected from a cooling blower 14 disposed concentrically with the annular die 12 above the annular die 12, and is solidified at the frost line FL. The heater 16 and the cooler 18 are used to perform a specific heat treatment described later.

[0081] The temperature of the melt discharged from the annular die 12 (the temperature at the outlet of the supply means) is preferably {Tm - 10} to {Tm + 40}°C, where Tm (°C) is the melting point of the liquid crystal polymer, from the viewpoints of improving the moldability and suppressing the deterioration of the liquid crystal polymer. As a guideline for the melt viscosity, 50 to 3500 Pa·s is preferable.

[0082] The draw ratio of the cylindrical film F in the film forming process by inflation molding according to the present embodiment is not particularly limited, but as the ratio (Br / Dr) of the draw ratio (blow ratio: Br) in the TD direction to the draw ratio (draw ratio: Dr) in the MD direction, 1.5 to 5 is preferable, and 2.0 to 4.5 is more preferable. Further, the draw ratio (Dr) in the MD direction is, for example, 1.0 to 5 times, preferably 1.1 to 3 times, and more preferably 1.2 to 2 times. Also, the draw ratio (Br) in the TD direction is, for example, 1.5 to 20 times, preferably 2 to 15 times, and more preferably 2.5 to 14 times.

[0083] (Specific heat treatment) In the manufacturing method of the present embodiment, in the process of expansion by inflation molding, before the cylindrical film F is solidified, a heat treatment step is performed in which the cylindrical film F is reheated using the heater 16 and then immediately cooled using the cooler 18. Hereinafter, a series of heat treatments including reheating and cooling performed in the process of expansion of the cylindrical film F is also referred to as "specific heat treatment". By performing a specific heat treatment on the expanding cylindrical film F before solidification (before reaching the frost line FL), in the cylindrical film F, an elastic modulus distribution in the thickness direction is likely to occur, where the elastic modulus is high at the central portion in the thickness direction and low at the surface layer portion near the surface. Although the detailed mechanism by which such an elastic modulus distribution is likely to occur is not clear, the inventors of the present invention speculate that by reheating the film surface to a temperature near the melting point while cooling the film surface immediately after heating so as not to inhibit the inflation moldability, the crystal structure of the surface layer portion of the film is changed by melting and rapid cooling.

[0084] The timing for performing the specific heat treatment is not particularly limited as long as it is before the cylindrical film solidifies, but it is preferably performed after the draw ratio of the cylindrical film F in the inflation process exceeds 50% with respect to the final draw ratio in the TD direction by inflation molding, more preferably after exceeding 80%, and even more preferably after exceeding 90%. The draw ratio in the TD direction can be confirmed by measuring the diameter or the circumferential length of the cylindrical film F. Also, by adjusting the vertical position of the heater 16, the timing for reheating the cylindrical film F can be adjusted. The same applies to the position of the cooler 18 and the timing for performing cooling.

[0085] The conditions for the specific heat treatment are appropriately adjusted according to the material constituting the polymer film and the target elastic modulus, etc. The reheating temperature is preferably {Tm - 10} °C or higher, more preferably higher than Tm, in terms of being able to make the elastic modulus distribution in the thickness direction clearer, where Tm (°C) is the melting point of the liquid crystal polymer. Also, in terms of suppressing the occurrence of thickness unevenness due to film softening, the reheating temperature is preferably {Tm + 20} °C or lower, more preferably {Tm + 15} °C or lower. The treatment time for reheating varies depending on the heating means and the heating temperature, but is preferably 0.2 to 15 seconds, more preferably 1 to 5 seconds. Examples of the heating means (heater 16) used for reheating include known heating means such as a hot air dryer and an infrared heater. Since the surface temperature of the film can be increased in a short time, an infrared heater is preferred. The heating means is preferably arranged evenly along the circumference of the cylindrical film F. By arranging the heating means in this way, the temperature difference in the circumferential direction of the cylindrical film F can be suppressed during reheating. can be suppressed. In the film forming apparatus 10 shown in FIG. 1, both surfaces of the cylindrical film F are heated by heaters 16 installed on both the outer peripheral side and the inner peripheral side of the cylindrical film F. The heating means may be installed on either the outer peripheral side or the inner peripheral side of the cylindrical film F, but it is preferably installed on both sides.

[0086] The cooling process in the specific heat treatment is preferably performed promptly after reheating in order to form the structure of the film surface layer and suppress thickness unevenness. The cooling process is preferably carried out so that the surface temperature of the cylindrical film F changes at a rate of -10°C / second or more (more preferably -20°C / second or more, still more preferably -30°C / second or more). The upper limit is not particularly limited, but for example, it is -80°C / second or less. From the same perspective as above, the cooling process is preferably carried out until the surface temperature of the cylindrical film F drops below the crystallization temperature. The crystallization temperature can be measured as the recrystallization peak temperature when the cylindrical film F is heated above the melting point using a differential scanning calorimeter (DSC) and then cooled at 10°C / min. The specific cooling time varies depending on the cooling means and the temperature of the film surface heated by reheating, but it is preferably 0.3 to 15 seconds, and more preferably 2 to 10 seconds. As the cooling means (cooler 18) used for the cooling process, a known cooling device can be used, but it is preferable to use a blower that blows air (preferably cold air) onto the cylindrical film F. The cooling means is preferably arranged evenly along the circumference of the cylindrical film F. By arranging the cooling means in this way, the temperature difference in the circumferential direction of the cylindrical film F can be suppressed during cooling. In the film forming apparatus 10 shown in FIG. 1, both surfaces of the cylindrical film F are cooled by coolers 18 installed on both the outer peripheral side and the inner peripheral side of the cylindrical film F. The cooling means may be installed on either the outer peripheral side or the inner peripheral side of the cylindrical film F, but it is preferably installed on both sides.

[0087] The solidified cylindrical film F is flattened by a pressure roll (such as a nip roll and a pinch roll, not shown) above the film forming apparatus 10. Subsequently, after trimming both end portions in the width direction of the flat film and separating it into two films, each film is wound by a winder (not shown) to obtain a polymer film.

[0088] (Relaxation treatment) In this embodiment, a relaxation step of relaxing the strain present inside the film may be performed by thermally shrinking the inflation-molded polymer film. In the relaxation step, under tension (for example, 2.0 to 3.0 kg / mm in the MD direction 2 to some extent), the polymer film is thermally shrunk in the TD direction. The shrinkage rate is, for example, 1% or more in the TD direction, and preferably 1.5% or more. The upper limit of the shrinkage rate is appropriately determined according to the film, but is often 4% or less in the TD direction. The relaxation treatment can be carried out, for example, by introducing the polymer film into a known heating device such as a hot air drying furnace. The set temperature of the relaxation treatment is preferably below the melting point Tm (°C) of the liquid crystal polymer, and more preferably below {Tm - 30}°C. The lower limit is not particularly limited, but is preferably {Tm - 120}°C or higher, and more preferably {Tm - 90}°C or higher. Alternatively, the set temperature of the relaxation treatment is preferably about 200 to 290°C, and more preferably about 230 to 270°C.

[0089] <Surface treatment> Since the adhesion between the polymer film and the metal-containing 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, or a plasma treatment under atmospheric pressure is also preferable. 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.

[0090] 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-forming step, the polymer film may be further 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.

[0091] [Laminate] The laminate of the present invention has the above polymer film and at least one metal-containing layer. Hereinafter, the configuration of the laminate according to the present invention will be described in detail.

[0092] The laminate has at least one metal-containing layer and at least one polymer film. The number of the metal-containing layer and the polymer film included in the laminate is not limited, and the number of each layer may be only one or two or more. The laminate may be a single-sided laminate having only one metal-containing layer on one side of one polymer film, or a double-sided laminate having two metal-containing layers on both sides of one polymer film. Among others, the laminate preferably has at least two metal-containing layers and has a layer structure in which a metal-containing layer, a polymer film, and a metal-containing layer are laminated in this order.

[0093] Further, the laminate may have a multilayer structure in which three or more metal-containing layers and two or more polymer films are laminated alternately. That is, the laminate may have a multilayer structure in which three or more metal layers or metal wirings are arranged via insulating layers made of polymer films. The laminate having such a multilayer structure can be applied as a highly functional multilayer circuit board (for example, a two-layer circuit board, a three-layer circuit board, a four-layer circuit board, etc.). The laminate may be a single-layer circuit board including two metal layers or metal wirings and an insulating layer made of one polymer film. Further, the laminate may be an intermediate for manufacturing the laminate having the above multilayer structure, including one or two metal layers or metal wirings and an insulating layer made of one polymer film.

[0094] [Metal-containing layer] The metal-containing layer is formed on the surface of the polymer film and is not particularly limited as long as it is a layer containing a metal. Examples thereof include a metal layer covering the entire surface of the polymer film and metal wirings formed on the surface of the polymer film. Examples of the material constituting the metal-containing 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 the alloy include copper-zinc alloy, copper-nickel alloy, and zinc-nickel alloy. Copper is preferable as the material constituting the metal-containing layer in terms of excellent conductivity and processability. As the metal-containing layer, a copper layer or copper wiring made of copper or a copper alloy containing 95% by mass or more of copper is preferable. Examples of the copper layer include rolled copper foil manufactured by a rolling method and electrolytic copper foil manufactured by an electrolysis method. The metal-containing layer may be subjected to chemical treatment such as pickling.

[0095] As described below, the metal-containing layer is formed, for example, using a metal foil, and a wiring pattern is formed by a known processing method as necessary. When a metal foil such as a copper foil is used in the production of the laminate, in terms of more excellent effects of the present invention, the surface roughness (arithmetic mean height) Ra of the surface of the metal foil (at least one surface) is preferably 3 μm or less, more preferably 1.5 μm or less. The lower limit is not particularly limited, and is, for example, 0.1 μm or more, preferably 0.3 μm or more. Examples of the metal foil having a surface roughness Ra in the above range include an unroughened copper foil, etc., which are available on the market. The Ra of the surfaces of the metal foil and the metal-containing layer is determined by a method conforming to JIS B 0601 using a surface roughness measuring instrument (for example, manufactured by Mitutoyo Corporation, product name: Surftest SJ-201). The specific measurement method is described in the examples below.

[0096] The thickness of the metal-containing layer is not particularly limited and is appropriately selected according to the use of the circuit board. However, from the viewpoints of conductivity and economy of the wiring, 1 to 100 μm is preferable, 5 to 30 μm is more preferable, and 10 to 20 μm is still more preferable.

[0097] The laminate may have other layers other than the polymer film and the metal-containing layer as necessary. Examples of the other layers include an adhesive layer, a rust preventive layer, and a heat resistant layer.

[0098] <Adhesive layer> The laminate preferably has an adhesive layer in terms of more excellent adhesion between the polymer film and the metal-containing layer. When the laminate has an adhesive layer, the adhesive layer is preferably disposed between the polymer film and the metal-containing layer. For example, when two metal-containing layers are disposed on both surfaces of the polymer film, it is preferable that they are laminated in the order of metal-containing layer, adhesive layer, polymer film, adhesive layer, and metal-containing layer.

[0099] As the subsequent 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 at least one of a known binder resin and a reactive compound described later can be mentioned. The adhesive composition used for forming the adhesive layer is not particularly limited. For example, a composition containing a binder resin and / or a reactive compound and further containing an additive described later as an optional component can be mentioned.

[0100] (Binder resin) Examples of the binder resin include (meth)acrylic resin, polyvinyl cinnamate, 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.

[0101] 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 based on the total mass of the adhesive layer.

[0102] (Reactive compound) The subsequent layer may contain a reactant of a compound having a reactive group, and preferably contains a reactive compound. In the present specification, the compound having a reactive group and its reactant are also collectively referred to as a "reactive compound". The reactive group of the reactive compound is preferably a group capable of reacting with a group that can be present on the surface of the polymer film (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.

[0103] 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).

[0104] 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-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride).

[0105] 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 Co., Ltd.), Stabaxol (registered trademark) P, P100, and P400 (all manufactured by Rhein Chemie), and Stabilizer 9000 (trade name, manufactured by Raschig Chemie), etc.

[0106] The number of reactive groups possessed by the reactive compound is 1 or more, but from the viewpoint of more excellent adhesion between the polymer film and the metal-containing layer, 3 or more is preferable. The upper limit is not particularly limited, for example, it is 6 or less, and 5 or less is preferable. The reaction product 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 reaction product 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.

[0107] 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 with respect to the total mass of the adhesive layer.

[0108] The subsequent layer may further contain components other than the binder resin and the reactive compound (hereinafter also referred to as "additives"). Examples of the additives include inorganic fillers, curing catalysts, flame retardants, and the like. The content of the additive is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and still more preferably 3 to 20% by mass with respect to the total mass of the adhesive layer.

[0109] (Thickness) When the laminate has an adhesive layer, the thickness of the adhesive layer 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 better adhesion between the polymer film and the metal-containing layer. The upper limit is not particularly limited, but preferably 1 μm or less, more preferably 0.8 μm or less, and still more preferably 0.6 μm or less. Also, the ratio of the thickness of the adhesive layer to the thickness of the polymer film is preferably 0.1 to 2%, more preferably 0.2 to 1.6% in terms of better adhesion between the polymer film and the metal-containing layer. Note that the thickness of the adhesive layer described above is the thickness per layer of the adhesive layer. The thickness of the adhesive layer can be measured according to the method for measuring the thickness of the polymer film described above.

[0110] [Manufacturing method of laminate] The manufacturing method of the laminate is not particularly limited. For example, a method having a step of manufacturing a laminate by laminating the polymer film of the present invention and a metal foil and then pressing the polymer film and the metal foil under high-temperature conditions (hereinafter also referred to as "Step B") can be mentioned.

[0111] <Step B> In Step B, the polymer film of the present invention and a metal foil made of the metal constituting the metal-containing layer are laminated, and the polymer film and the metal foil are pressed under high-temperature conditions to manufacture a laminate having a polymer film and a metal-containing layer. Regarding the polymer film and metal foil used in Process B, it is as described above. The method and conditions for thermocompression bonding the polymer film and the metal foil in Process B are not particularly limited and are appropriately selected from known methods and conditions. The thermocompression bonding in Process B can be carried out using known means such as a heating roll. Examples of the heating roll include a metal roll and a heat-resistant rubber roll. As the temperature condition for thermocompression bonding, {Tm - 80} to {Tm + 30} °C is preferable, and {Tm - 40} to Tm °C is more 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.

[0112] The metal-containing layer provided in the laminate may be a patterned metal wiring. The method for producing the metal wiring is not particularly limited. For example, after performing Process B of laminating a polymer film and a metal foil by thermocompression bonding, the above metal wiring can be formed by subjecting the formed metal layer to an etching treatment or the like. Also, a patterned metal wiring may be directly formed on the surface of the polymer film by known methods such as a sputtering method, an ion plating method, and a vapor deposition method, as well as a wet plating method.

[0113] <Adhesive layer forming step> When manufacturing a laminate having a polymer film, an adhesive layer, and a metal-containing layer in this order, a step of forming an adhesive layer on at least one side of the polymer film using an adhesive composition is performed. Then, Process B is performed using the obtained polymer film with an adhesive layer and the metal foil, whereby a laminate having the above adhesive layer is obtained.

[0114] Examples of the adhesive layer forming step include a step of applying an adhesive composition to at least one surface of the polymer film and, if necessary, drying and / or curing the coating film to form an adhesive layer on the polymer film.

[0115] The adhesive composition includes, for example, a composition containing components constituting an adhesive layer such as the above binder resin, reactive compound, and additive, and a solvent. Since the components constituting the adhesive layer are as described above, their descriptions are omitted.

[0116] 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).

[0117] 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 adhesive composition. The content of the solid content of the adhesive composition 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 adhesive composition. In this specification, the "solid content" of the composition means the components excluding the solvent (organic solvent) and water. That is, the solid content of the adhesive composition refers to the components constituting the adhesive layer such as the above binder resin, reactive compound, and additive.

[0118] The method for attaching the adhesive composition onto the polymer film is not particularly limited. For example, bar coating method, spray coating method, squeegee coating method, flow coating method, spin coating method, dip coating method, die coating method, inkjet method, and curtain coating method can be mentioned. When drying the adhesive composition attached onto the polymer film, the drying conditions are not particularly limited, but the drying temperature is preferably 25 to 200 °C, and the drying time is preferably 1 second to 120 minutes. In the method for manufacturing the laminate, after performing the step of forming the adhesive layer using the adhesive composition, the polymer film, the metal-containing layer, and (the adhesive layer) are laminated, and by performing the above step B of thermocompression bonding the polymer film and the metal foil, the laminate of the present invention can be produced.

[0119] Note that the method for manufacturing the laminate of the present invention having the polymer film and the metal-containing layer is not limited to the above method. For example, the above adhesive composition is applied onto at least one surface of the metal foil, and after drying and / or curing the coating film as necessary to form the adhesive layer, the metal foil with the adhesive layer and the polymer film are laminated such that the adhesive layer is in contact with the polymer film, and then, according to the method described in step B, the metal foil, the adhesive layer, and the polymer film are thermocompression bonded, whereby a laminate in which the polymer film, the adhesive layer, and the metal-containing layer are laminated in this order can be produced. Also, a metal-containing layer may be formed on the surface of the polymer film by known methods such as vapor deposition, electroless plating, and electroplating, to produce a laminate.

[0120] The laminate manufactured by the above manufacturing method can be used for manufacturing the above multilayer circuit board. For example, a patterning process is performed on the metal layer included in the laminate (first laminate) manufactured by the above manufacturing method as needed to form metal wiring. Next, the first laminate having the metal wiring and a second laminate in which a metal layer is bonded to one surface of an insulating layer made of a polymer film are laminated such that the surface of the first laminate on the metal wiring side and the surface of the second laminate on the insulating layer side are in contact with each other. By thermocompression bonding the obtained laminate according to the above step B, a circuit board having a multilayer structure can be manufactured. At this time, by using the polymer film of the present invention in the manufacture of the first laminate, displacement of the metal wiring in the in-plane direction (direction perpendicular to the lamination direction) can be suppressed when the first laminate and the second laminate are laminated.

[0121] 〔Use of laminate〕 Examples of the use of the laminate include wiring boards 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

[0122] The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, and processing 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 below. Unless otherwise specified, “%” is based on mass.

[0123] [Raw materials] <Liquid crystal polymer> A polymer film was manufactured using the following liquid crystal polymers. ·LCP1: “Vectra (registered trademark) A950” manufactured by Polyplastics Co., Ltd., a thermoplastic liquid crystal polyester resin, melting point Tm: 280°C. ·LCP2: “Vectra C950” manufactured by Polyplastics Co., Ltd., a thermoplastic liquid crystal polyester resin, melting point Tm: 320°C. Both the above LCP1 and LCP2 are type II liquid crystal polymers composed of repeating units derived from para-hydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid. Also, the temperature of crystallization during cooling when the above LCP1 and LCP2 were melted was 250 °C or higher and 290 °C or higher, respectively. The respective recrystallization peak temperatures measured by the above method using a differential scanning calorimeter (DSC) are shown in Table 1 described later.

[0124] <Metal foil> In the production of the metal-clad laminate, the following metal foils were used. · Copper foil 1: Rolled copper foil, thickness 12 μm, surface roughness Ra 0.9 μm. · Copper foil 2: Rolled copper foil, thickness 18 μm, surface roughness Ra 0.9 μm. The surface roughness Ra of the copper foil was calculated by measuring the arithmetic mean roughness Ra at 10 locations on the copper foil surface in accordance with JIS B0601 using a surface roughness measuring instrument (manufactured by Mitutoyo Corporation, product name: Surftest SJ-201) and averaging the measured values.

[0125] [Example 1] Using the manufacturing apparatus shown in FIG. 1, a polymer film was manufactured by the following method. The detailed conditions of the inflation molding will be described later.

[0126] [Film forming step by inflation molding (Step A)] After preliminarily heating and drying the pellets of the above LCP1 at a temperature of 150 °C for 6 hours, they were supplied into the cylinder (diameter 60 mm) of a single-screw extruder and heat-kneaded at 295 °C, and the melt of LCP1 was extruded from an annular die having the following structure at a die shear rate of 1000 s -1 to form a cylindrical film.

[0127] Subsequently, using a manufacturing apparatus (inflation molding apparatus) having the following configuration, while cooling the outer surface of the discharged molten cylindrical film, air was supplied to the internal space and it was expanded by internal pressure. At this time, the stretching ratio was controlled such that the ratio of the stretching ratio in the TD direction (circumferential direction) to the stretching ratio in the MD direction (longitudinal direction) of the expanded cylindrical film was 3. Also, for the cylindrical film stretched while moving upward, a specific heat treatment was performed in which the cylindrical film was heated at a position where the stretching ratio in the TD direction exceeded 90% of the final ratio, and then immediately cooled. More specifically, as the specific heat treatment, heating was performed for 2 seconds using an infrared heater disposed at the above position so that the surface temperature of the cylindrical film reached a temperature described later. Immediately thereafter, cooling was performed for 2 seconds using a cold air nozzle disposed directly above the infrared heater so that the surface temperature of the cylindrical film decreased at a cooling rate described later. Next, the cylindrical film subjected to the specific heat treatment was flattened by pinch rolls, and then both end portions in the width direction were trimmed and wound up in film form.

[0128] Next, while applying tension in the MD direction to the produced film, it was introduced into a hot air drying furnace set at 260°C and heated to perform a relaxation treatment for thermally shrinking in the TD direction. The thermal shrinkage rate of the film before and after the relaxation treatment was 2%. The relaxed film was conveyed while being guided by rollers, taken up by nip rollers, and the polymer film of the present invention was obtained. The thickness of the produced polymer film was 50 μm.

[0129] The manufacturing conditions of the polymer film of Example 1 and the configuration of the inflation molding apparatus are shown below. · Melting temperature of extruder: 295°C · Discharge temperature of raw material resin: 283°C · Discharge amount of raw material resin (molten): 13 kg / hr · Diameter of annular die: 50 mm · Slit width of annular die: 250 μm · Position of the cooling ring: 30 mm vertically above the annular die · Temperature of the gas blown out from the cooling ring: 150 °C · Wind speed of the gas blown out from the cooling ring: 5 m / sec · Position of the infrared heater: 350 mm vertically above the annular die · Film surface heating temperature: 290 °C · Position of the cooling device: 450 mm vertically above the annular die · Film surface cooling rate: -50 °C / sec · Expansion ratio in the TD direction: 4 times · Expansion ratio in the TD direction / Expansion ratio in the MD direction: 3 · Take-up speed of the polymer film: 9.9 m / min

[0130] 〔Manufacture of the metal-clad laminate (Process B)〕 The polymer film manufactured in the above process and the two copper foils 1 were laminated, and the laminate was introduced between a heat-resistant rubber roll and a heating metal roll provided in a continuous hot press machine and crimped to produce a copper-clad laminate in which the copper foil 1, the polymer film, and the copper foil 1 were laminated in this order. As the above heat-resistant rubber roll, a resin-coated metal roll (manufactured by Yurii Roll Machine Co., Ltd., trade name: Super Temperex, resin thickness: 1.7 cm) was used. Also, as the heat-resistant rubber roll and the heating metal roll, those with a diameter of 40 cm were used. The surface temperatures of the heating metal roll and the heat-resistant rubber roll were set to be 20 °C lower than the melting point of the polymer film (i.e., 260 °C). Further, between the heat-resistant rubber roll and the heating metal roll, the pressure applied to the polymer film and the copper foil 1 was set to 40 kg / cm in terms of surface pressure. 2

[0131] [Examples 2 to 4] The polymer films of Examples 2 to 4 were each manufactured according to the method described in Process A of Example 1, except that the heating temperature and / or the cooling rate in the specific heat treatment were changed to the conditions described in Table 1 below. ​Next, double-sided copper-clad laminates of Examples 2 to 4 were each produced according to the method described in Step B of Example 1, except that each of the produced polymer films was used.

[0132] [Example 5] The polymer films of Example 5 were each produced according to the method described in Step A of Example 1, except that the discharge amount of the raw material resin and the slit width of the annular die were changed so that the thickness of the produced polymer film became 25 μm. Next, a double-sided copper-clad laminate of Example 5 was produced according to the method described in Step B of Example 1, except that the produced polymer film was used.

[0133] [Example 6] The polymer films of Example 6 were produced according to the method described in Step A of Example 1, except that LCP2 was used instead of LCP1 as the raw material of the liquid crystal polymer, and the heating temperature in the specific heat treatment was changed to the conditions described in Table 1 below. Next, a double-sided copper-clad laminate of Example 6 was produced according to the method described in Step B of Example 1, except that the polymer film of this example produced was used and the surface temperature of the heating metal roll was set to 290°C.

[0134] [Example 7] The polymer films of Example 7 were produced according to the method described in Step A of Example 1, except that the cooling rate in the specific heat treatment was changed to the conditions described in Table 1 below. Next, a double-sided copper-clad laminate of Example 7 was produced according to the method described in Step B of Example 1, except that the polymer film of this example produced was used and two sheets of the above copper foil 2 were used instead of two sheets of copper foil 1.

[0135] [Example 8] After manufacturing a polymer film according to the method described in Step A of Example 1, the following adhesive composition was applied to both sides of the obtained polymer film, and the polymer film with a coating film was introduced into a continuous drying oven at 110 °C to dry and remove the solvent component in the coating film. The thickness of the adhesive layer after drying was 0.001 mm. Adhesive composition: A crosslinking agent solution containing 10% by mass of N,N-diglycidyl-4-glycidyloxyaniline (manufactured by Sigma-Aldrich) as a crosslinking agent, with the balance being a solvent (toluene). Next, except for using the polymer film with an adhesive layer manufactured by the above method, a double-sided copper-clad laminate of Example 8 was produced according to the method described in Step B of Example 1.

[0136] [Comparative Example 1] A polymer film of Comparative Example 1 was produced according to the method described in Step A of Example 1, except that a cylindrical film formed by inflation molding was not subjected to a specific heat treatment. Next, except for using the produced polymer film of Comparative Example 1, a double-sided copper-clad laminate of Comparative Example 1 was produced according to the method described in Step B of Example 1.

[0137] [Comparative Example 2] A polymer film of Comparative Example 2 was produced according to the method described in Step A of Example 1, except that the heating temperature in the specific heat treatment was changed to the conditions described in Table 1 below. Next, except for using the produced polymer film of Comparative Example 2, a double-sided copper-clad laminate of Comparative Example 2 was produced according to the method described in Step B of Example 1.

[0138] [Polymer Film Properties] <Elastic Modulus> The elastic modulus of the polymer film produced in each example was measured by the following method. The polymer films produced in each example were cut along the thickness direction to prepare a cut surface. At the obtained cut surface, the elastic modulus A at position A, which is at a distance of half the thickness of the polymer film from one surface toward the other surface, and the elastic modulus B at position B, which is at a distance of 1 / 8 of the thickness of the polymer film from one surface toward the other surface, were measured by the nanoindentation method. The elastic modulus was measured using a nanoindenter (“TI-950”, manufactured by HYSITRON) and a Berkovich indenter. At each position, 10 points were measured under the conditions of a load of 500 μN, a load time of 10 seconds, a holding time of 5 seconds, and an unloading time of 10 seconds. The arithmetic mean value of the 10 points was taken as each elastic modulus (unit: GPa). Table 1 described later shows the elastic modulus A at position A, the elastic modulus B at position B, and the ratio of the elastic modulus B to the elastic modulus A (ratio B / A).

[0139] <Dielectric properties> The center portion of the polymer film produced in each example was sampled, and the dielectric loss tangent and relative permittivity in the 28 GHz frequency band were measured using a split cylinder resonator (“CR-728” manufactured by Kanto Electronic Application Development Co., Ltd.) and a network analyzer (Keysight N5230A) in an environment of a temperature of 23°C and a humidity of 50% RH.

[0140] [Evaluation] For the copper-clad laminates produced in each example, the following evaluation tests were conducted.

[0141] <Adhesion> The copper-clad laminates produced in each example were cut into strips measuring 1 cm × 5 cm to prepare samples for adhesion evaluation. The peel strength (unit: N / cm) 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 (manufactured by IMADA Co., Ltd., digital force gauge ZP-200N) to peel the copper foil at a peeling speed 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 foil and the polymer film was evaluated based on the value measured by the tensile testing machine.

[0142] <Misalignment> The double-sided copper-clad laminates produced in each example were cut into a size of 15 cm × 15 cm to prepare samples of the double-sided copper-clad laminates. A mask layer was laminated on the surface of one copper layer of the obtained samples, pattern-exposed, and then developed to form a mask pattern. Next, only the surface on the mask pattern side of the sample was immersed in a 40% aqueous solution of iron(III) chloride (manufactured by Fujifilm Wako Pure Chemical Corporation, grade 1), and the copper layer without the mask pattern laminated thereon was subjected to an etching treatment. Then, the mask pattern was peeled off to form a copper wiring (microstrip line). The size of the copper wiring was 10 cm in length and 105 μm in width. In this way, a first sample was obtained in which copper wiring was formed on one surface and a copper layer was formed on the entire surface of the other surface. Except for laminating a polymer film and one copper foil, a single-sided copper-clad laminate was produced in the same manner as in step B of each example. Then, the produced single-sided copper-clad laminate was cut into a size of 15 cm × 15 cm to prepare a sample of the single-sided copper-clad laminate. A treatment including the same etching treatment as described above was performed on the copper layer of the obtained sample to prepare a second sample in which copper wiring having the same position and size as the copper wiring of the first sample was formed on one surface.

[0143] The first sample and the second sample were laminated such that the surface on the copper wiring side of the first sample was in contact with the surface on which the copper wiring of the second sample was not formed, and the in-plane positions of the respective copper wirings were aligned. The obtained multilayer laminate was introduced between a pair of heating metal rolls provided in a continuous hot press machine for thermocompression bonding. At this time, the surface temperature of the heating metal rolls was set to 260 °C, and the pressure applied to the multilayer laminate was set to 40 kg / cm in terms of surface pressure. 2

[0144] The multilayer laminate produced by the above method was cut so that a cross-section perpendicular to the longitudinal direction of each copper wiring and including the lamination direction was formed. The obtained cut surface was observed using a scanning electron microscope (SEM). In the observed cross-sectional image, the position of the copper wiring of the first sample was compared with the position of the copper wiring of the second sample, and the difference in the position of the copper wiring of the first sample with respect to the position of the copper wiring of the second sample in the in-plane direction (the short-side direction of the copper wiring) was measured. Based on the following evaluation criteria, the misalignment of the metal-clad laminate produced in each example was evaluated from the measured difference.

[0145] (Misalignment evaluation criteria) A: The ratio of the misalignment of the copper wiring to the thickness of the polymer film is less than 1%. B: The ratio of the misalignment of the copper wiring to the thickness of the polymer film is 1% or more and less than 3%. C: The ratio of the misalignment of the copper wiring to the thickness of the polymer film is 3% or more and less than 5%. D: The ratio of the misalignment of the copper wiring to the thickness of the polymer film is 5% or more.

[0146] [Results] Table 1 below shows the manufacturing conditions and characteristics of the polymer film, the manufacturing conditions of the metal-clad laminate, and the evaluation results for each example and each comparative example. The "resin" column in Table 1 shows the type and melting point (unit: °C) of the resin (liquid crystal polymer) used for manufacturing the polymer film in each example. The "manufacture of polymer film" column in Table 1 shows the method and conditions of the specific heat treatment in step A.

[0147] [Table 1]​

[0148]

Table 2

[0149] From the results shown in the above table, it was confirmed that the problems of the present invention can be solved by the polymer film of the present invention.

Explanation of Reference Numerals

[0150] 10 Film forming apparatus 12 Annular die 14 Cooling blower 16 Heater 18 Cooler

Claims

1. A polymer film containing a liquid crystal polymer, wherein the liquid crystal polymer is a thermoplastic liquid crystal polyester or a thermoplastic liquid crystal polyester amide having a repeating unit 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, in a cross-section along the thickness direction of the polymer film, when the elastic modulus at position A, which is at a distance of half the thickness of the polymer film from one surface of the polymer film toward the other surface, is defined as elastic modulus A, and the elastic modulus at position B, which is at a distance of 1 / 8 of the thickness of the polymer film from one surface of the polymer film toward the other surface, is defined as elastic modulus B, the ratio B / A of the elastic modulus B to the elastic modulus A is 0.99 or less, and the elastic modulus A is 4.0 GPa or more, Polymer film.

2. The polymer film according to Claim 1, wherein the liquid crystal polymer has a repeating unit derived from at least one selected from the group consisting of p-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4-(4-hydroxyphenyl)benzoic acid, hydroquinone, 4,4'-dihydroxybiphenyl, 3,3'-dimethyl-1,1'-biphenyl-4,4'-diol, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, p-phenylenediamine, 4-aminophenol, and 4-aminobenzoic acid.

3. The polymer film according to Claim 1 or 2, wherein the liquid crystal polymer has at least one selected from the group consisting of a repeating unit derived from an aromatic hydroxycarboxylic acid represented by the following formula (1), a repeating unit derived from an aromatic dicarboxylic acid represented by the following formula (2), and a repeating unit derived from an aromatic diol represented by the following formula (3). -O-Ar1-CO- (1) -CO-Ar2-CO- (2) -O-Ar3-O- (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). -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. Any of the phenylene group, the naphthylene group, and the biphenylylene group may have a substituent selected from the group consisting of a halogen atom, an alkyl group, and an aryl group.

4. The polymer film according to any one of claims 1 to 3, wherein the liquid crystal polymer contains 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.

5. The polymer film according to any one of claims 1 to 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.

6. The polymer film according to any one of claims 1 to 5, wherein the elastic modulus A is 4.6 GPa or more.

7. The polymer film according to any one of claims 1 to 6, which has a single-layer structure.

8. The polymer film according to any one of claims 1 to 7, wherein the dielectric tangent of the polymer film at a temperature of 23 °C and a frequency of 28 GHz is 0.0022 or less.

9. A laminate having the polymer film according to any one of claims 1 to 8 and at least one metal-containing layer.

10. The laminate according to claim 9, having at least two of the metal-containing layers, wherein the metal-containing layer, the polymer film, and the metal-containing layer are laminated in this order.

11. The laminate according to claim 9 or 10, wherein the thickness of the metal-containing layer is 5 to 30 μm.

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