Liquid crystal polymer film, laminate

Abstract

To provide a liquid crystal polymer film excellent in peel strength of a laminate produced by sticking metal foils, and a laminate.SOLUTION: A liquid crystal polymer film includes a liquid crystal polymer where the average value of widths of void regions is 0.01-0.1 μm when extracting the void regions from an observed image of a cross section obtained using an electron microscope after exposing the cross section along a thickness direction of the liquid crystal polymer film, and immersing in monomethyl amine, and the area ratio of the void regions in the observed image of the cross section is 20% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a liquid crystal 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 thermoplastic liquid crystal polymer film having a toughness of 30 MPa or more and 100 MPa or less after thermocompression bonding the thermoplastic liquid crystal polymer film to a conductor layer, and a circuit board formed by laminating the thermoplastic liquid crystal polymer film and the conductor layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the present inventors further studied the liquid crystal polymer film described in Patent Document 1, they found that there is room for further improvement in the peel strength of a laminate produced by laminating the liquid crystal polymer film and a metal foil.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal polymer film having excellent peel strength of a laminate produced by laminating a metal foil. Another object of the present invention is to provide a laminate having the above-described liquid crystal polymer film and a metal-containing layer.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the present inventors have found that when the void region obtained by observing the cross section in the thickness direction of the liquid crystal polymer film satisfies a predetermined requirement, the peel strength of the laminate produced by laminating a metal foil is more excellent, and thus completed the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0008] 〔1〕 A liquid crystal polymer film containing a liquid crystal polymer, wherein when the cross section along the thickness direction of the liquid crystal polymer film is exposed, immersed in monomethylamine, and the void region is extracted from the observation image of the cross section obtained using an electron microscope, the average value of the width of the void region is 0.01 to 0.1 μm, and the area ratio of the void region in the observation image of the cross section is 20% or less. 〔2〕 The liquid crystal polymer film according to 〔1〕, wherein the average length of the void region is 3 to 5 μm. 〔3〕 The liquid crystal polymer film according to 〔1〕 or 〔2〕, having a thickness of 15 μm or more and satisfying requirement A described below. 〔4〕 The polymer film according to any one of 〔1〕 to 〔3〕, wherein the melting point of the liquid crystal polymer is 250°C or higher. 〔5〕 The film according to any one of 〔1〕 to 〔4〕, wherein the liquid crystal polymer 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. 〔6〕 The liquid crystal polymer film according to any one of 〔1〕 to 〔4〕, 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 compound, a repeating unit derived from terephthalic acid, and a repeating unit derived from 2,6-naphthalenedicarboxylic acid. 〔7〕 The liquid crystal polymer film according to any one of 〔1〕 to 〔6〕, further comprising a polyolefin, wherein the content of the polyolefin is 40% by mass or less based on the total mass of the liquid crystal polymer film. 〔8〕 A laminate having the polymer film according to any one of 〔1〕 to 〔7〕 and at least one metal-containing layer. 〔9〕 The laminate according to 〔8〕, 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. 〔10〕 The laminate according to 〔8〕 or 〔9〕, wherein the surface roughness Ra of the surface of the metal-containing layer facing the polymer film is 5 μm or less. 〔11〕 The laminate according to any one of 〔8〕 to 〔10〕, wherein the metal-containing layer is a copper layer. 〔12〕 The laminate according to any one of 〔8〕 to 〔11〕, further comprising an adhesive layer disposed between the metal-containing layer and the polymer film. 〔13〕 The laminate according to 〔12〕, wherein the adhesive layer is a layer formed using an adhesive composition containing a crosslinking agent having an epoxy group.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a liquid crystal polymer film excellent in peel strength of a laminate produced by laminating a metal foil, and a laminate having the same.

Brief Description of the Drawings

[0010]

Figure 1

Best Mode 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 this specification, the “organic group” means a group containing at least one carbon atom.

[0012] In this specification, when the liquid crystal polymer film or laminate is in a long shape, the length direction means the longitudinal direction of the liquid crystal 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 liquid crystal 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 substance corresponding to each component, or two or more kinds may be used. Here, when two or more kinds of substances are used for each component, the content of that component means the total content of two or more kinds of substances unless otherwise specified. In this specification, “~” is used in the sense of 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 liquid crystal polymer film or the liquid crystal polymer contained in the liquid crystal 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] [Liquid Crystal Polymer Film] The liquid crystal polymer film of the present invention (hereinafter, also simply referred to as “polymer film”) contains a liquid crystal polymer. Further, the liquid crystal polymer film of the present invention satisfies specific requirements described later in the void region in the cross section along the thickness direction.

[0014] 〔Void Characteristics〕 When the cross-section along the thickness direction of the liquid crystal polymer film of the present invention is exposed, immersed in monomethylamine, and the void region is extracted from the observation image of the cross-section obtained using an electron microscope, the average value of the width of the void region is 0.01 to 0.1 μm, and the area ratio (void region area ratio) of the void region in the observation image of the cross-section is 20% or less. Although the detailed mechanism by which the problem of the present invention is solved by the polymer film containing a liquid crystal polymer satisfying the above requirements for the voids present in the cross-section including the thickness direction has not been clarified, the present inventors speculate as follows. That is, when the voids in the cross-section in the thickness direction satisfy the above requirements, it is speculated that the space occupied by the substantial part (domain region) composed of the liquid crystal polymer or the like in the polymer film is large and the space occupied by the voids is small, and since the distance between the domain regions in the thickness direction is narrow, the adhesive force or cohesive force between the domain regions increases. As a result, in the metal-clad laminate produced by laminating the metal foil, it is considered that the cohesive failure in the polymer film is suppressed when peeling the metal foil from the polymer film, and the peel strength of the metal foil is improved. Hereinafter, in this specification, when the peel strength is more excellent in the laminate produced by bonding the polymer film and the metal foil, it is also described as "the effect of the present invention is more excellent".

[0015] In this specification, the "void region" is a region where voids are observed in an image obtained using an electron microscope by a predetermined method for a cross-section along the thickness direction of the polymer film. The area and size of the void region are determined based on data obtained by photographing the cross-section exposed by cutting the polymer film along the thickness direction using a scanning electron microscope (SEM: Scanning Electron Microscope) and performing image processing on the photographed image using image processing software (ImageJ). The specific measurement method is described in the examples below.

[0016] The void area ratio of the polymer film of the present invention is 20% or less. In terms of the more excellent effects of the present invention, the void area ratio of the polymer film is preferably 15% or less, more preferably 10% or less. The lower limit is not particularly limited and is, for example, 0.1% or more. Further, in the polymer film of the present invention, the average width of the void region is 0.01 to 0.1 μm. In terms of the more excellent effects of the present invention, the average width of the void region is preferably 0.02 to 0.05 μm. The average length of the void region of the polymer film is preferably 0.5 to 10 μm, more preferably 1.0 to 8.0 μm, and still more preferably 3 to 5 μm in terms of better adhesion between domain layers. The void area ratio in the cross-section in the thickness direction of the polymer film, as well as the average width and average length of the void region, can be adjusted, for example, by performing the annealing treatment described later in the film-forming process of the polymer film.

[0017] In terms of the more excellent effects of the present invention, the polymer film preferably has a thickness of 15 μm or more and satisfies the following requirement A. Requirement A: In the cross-section in the thickness direction, a region within 5 μm from one surface of the polymer film is defined as the first surface layer region, a region within 5 μm from the other surface of the polymer film is defined as the second surface layer region, and when a region within 2.5 μm from the center line equidistant from both surfaces of the polymer film is defined as the central layer region, the area ratio of the void region in the central layer region is larger than the area ratio of the void region in the first surface layer region and larger than the area ratio of the void region in the second surface layer region.

[0018] In terms of the more excellent effects of the present invention, the ratio of the area ratio of the void region in the central layer region to the area ratio of the void region in the first surface layer region and the second surface layer region (hereinafter, both are collectively referred to as the "surface layer region") is preferably 120% or more, more preferably 150% or more. The upper limit is, for example, 300% or less, preferably 200% or less. The void area ratio in the surface region varies depending on the void area ratio throughout the thickness direction, but is, for example, 0.1 to 30%, preferably 0.1 to 20%. The void area ratio in the central layer region varies depending on the void area ratio throughout the thickness direction, but is, for example, 0.1 to 30%, preferably 5 to 20%.

[0019] In the polymer film, the void area ratios in the surface region and the central layer region can be adjusted, for example, by performing a specific heat treatment described later in the film-forming process of the polymer film.

[0020] 〔Components〕 Hereinafter, the components contained in the polymer film will be described in detail.

[0021] <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 thermotropic liquid crystal polymer is not particularly limited in its chemical composition 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 Unexamined Patent Application Publication No. 2019-116586 can be used.

[0022] More specific examples of the liquid crystal polymer include thermoplastic liquid crystal polyesters or thermoplastic 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.

[0023] 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.

[0024] 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 phenylene group, the naphthylene group, and the biphenylylene group may each have a substituent selected from the group consisting of a halogen atom, an alkyl group, and an aryl group.

[0025] Among them, the liquid crystal polymer preferably has at least one selected from the group consisting of a repeating unit derived from the aromatic hydroxycarboxylic acid represented by the above formula (1), a repeating unit derived from the aromatic diol represented by the above formula (3) in which both X and Y are oxygen atoms, and a repeating unit derived from the aromatic dicarboxylic acid represented by the above formula (2). Furthermore, it is more preferable that the liquid crystal polymer has at least a repeating unit derived from an aromatic hydroxycarboxylic acid, and it is even 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. Particularly preferably, it has a repeating unit derived from p-hydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid.

[0026] In another preferred embodiment, in terms of more excellent effects of the present invention, the liquid crystal polymer more 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. Even more preferably, it has all 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.

[0027] When the liquid crystal polymer contains repeating units derived from aromatic hydroxycarboxylic acids, the composition ratio is preferably 50 to 65 mol% based on all the repeating units of the liquid crystal polymer. Further, it is also preferable that the liquid crystal polymer has only repeating units derived from aromatic hydroxycarboxylic acids. When the liquid crystal polymer contains repeating units derived from aromatic diols, the 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 repeating units derived from aromatic dicarboxylic acids, the 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 repeating units derived from any of aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids, the composition ratio is preferably 2 to 8 mol% based on all the repeating units of the liquid crystal polymer.

[0028] The method for synthesizing 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 "Rapelos" manufactured by Polyplastics Co., Ltd., "Vectra" manufactured by Celanese Corporation, "UENO LCP" manufactured by Ueno Pharmaceutical Co., Ltd., "Sumika Super LCP" manufactured by Sumitomo Chemical Co., Ltd., "Zyder" manufactured by ENEOS Corporation, and "Ciberas" manufactured by Toray Industries, Inc. Note that the liquid crystal polymer may form a chemical bond with a crosslinking agent or a compatibilizing component (reactive compatibilizer), which is an optional component, in the polymer film. This also applies to components other than the liquid crystal polymer.

[0029] In terms of easily manufacturing a polymer film having a low standard dielectric tangent (preferably 0.003 or less), the standard dielectric 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. When the polymer film contains two or more kinds of liquid crystal polymers, the "dielectric tangent of the liquid crystal polymer" means the mass average value of the dielectric tangents of two or more kinds of liquid crystal polymers.

[0030] The standard dielectric tangent of the liquid crystal polymer contained in the polymer film can be measured by the following method. First, after immersing in an organic solvent (for example, pentafluorophenol) 1000 times the total mass of the polymer film, it is heated at 120 ° C for 12 hours to elute the organic solvent-soluble component containing the liquid crystal polymer into the organic solvent. Next, the eluate containing the liquid crystal polymer and the non-eluted component are separated by filtration. Subsequently, acetone is added to the eluate as a poor solvent to precipitate the liquid crystal polymer, and the precipitate is separated by filtration. The obtained precipitate is filled into a PTFE (polytetrafluoroethylene) tube (outer diameter 2.5 mm, inner diameter 1.5 mm, length 10 mm), and using a cavity resonator (for example, "CP-531" manufactured by Kanto Electronic Application Development Co., Ltd.), under the conditions of a temperature of 23 ° C and a frequency of 28 GHz, the dielectric properties are measured by the cavity resonator perturbation method, and by correcting the influence of the voids in the PTFE tube with Bruggeman's equation and the porosity, the standard dielectric tangent of the liquid crystal polymer can be obtained. The above porosity (the volume ratio of the voids in the tube) is calculated as follows. From the inner diameter and length of the above tube, the volume of the space in the tube is obtained. Next, after measuring the weight of the tube before and after filling the precipitate to obtain the mass of the filled precipitate, the volume of the filled precipitate is obtained from the obtained mass and the specific gravity of the precipitate. By calculating the filling rate by dividing the volume of the precipitate thus obtained by the volume of the space in the tube obtained above, the porosity can be calculated. When using a commercially available product of the liquid crystal polymer, the numerical value of the dielectric tangent described as the catalog value of the commercially available product may be used.

[0031] As the liquid crystal polymer, in terms of more excellent heat resistance, the melting point Tm is preferably 250 ° C or higher, more preferably 280 ° C or higher, and still more preferably 310 ° C or higher. The upper limit of the melting point Tm of the liquid crystal polymer is not particularly limited, but is preferably 400 °C or lower, more preferably 380 °C or lower, in terms of better moldability. The melting point Tm of the liquid crystal polymer can be determined by measuring the temperature at which an endothermic peak appears using a differential scanning calorimeter (DSC-60A manufactured by Shimadzu Corporation). When using a commercially available product of the liquid crystal polymer, the melting point Tm described as the catalog value of the commercially available product may also be used.

[0032] The number average molecular weight (Mn) of the liquid crystal polymer is not particularly limited, but is preferably from 10,000 to 600,000, more preferably from 30,000 to 150,000. The number average molecular weight of the liquid crystal polymer is a converted value of standard polystyrene by gel permeation chromatography (GPC). The GPC measurement can be carried out under the following apparatus and conditions. As the measuring apparatus, "HLC (registered trademark)-8320GPC" manufactured by Tosoh Corporation is used, and as the columns, two "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 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 carried out using an RI (differential refractive index) detector. The calibration curve is prepared from eight samples of "standard sample TSK standard, polystyrene": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene" manufactured by Tosoh Corporation.

[0033] The polymer film may contain one type of liquid crystal polymer alone, or may contain 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 with respect to the total mass of the polymer film. In addition, the content of the liquid crystal polymer and the components described later in the polymer film can be measured by known methods such as infrared spectroscopy and gas chromatography-mass spectrometry.

[0034] <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 later.

[0035] (Polyolefin) The polymer film may contain polyolefin. In this specification, "polyolefin" is intended to mean a polymer (polyolefin resin) having a repeating unit derived from an olefin. 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.

[0036] The polyolefin may be linear or branched. Further, the polyolefin may have a cyclic structure such as a polycyclic olefin. Examples of the polyolefin include polyethylene, polypropylene (PP), polymethylpentene (TPX manufactured by Mitsui Chemicals, Inc., etc.), hydrogenated polybutadiene, cycloolefin polymer (COP, Zeonor manufactured by Zeon Corporation, etc.), and cycloolefin copolymer (COC, Apel manufactured by Mitsui Chemicals, Inc., etc.). The polyethylene may be either high-density polyethylene (HDPE) or low-density polyethylene (LDPE). Further, the polyethylene may be linear low-density polyethylene (LLDPE).

[0037] The polyolefin may be a copolymer of an olefin and a copolymerization component other than an olefin, such as an acrylate, a methacrylate, styrene, and / or a vinyl acetate-based monomer. Examples of the polyolefin which is the copolymer include a 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 an olefin is preferably small, and it is more preferably not containing a copolymerization component. For example, the content of the copolymerization component is preferably 0 to 40% by mass, more preferably 0 to 5% by mass, based on the total mass of the polyolefin. Further, the polyolefin preferably substantially does not contain a reactive group described later, and the content of the repeating unit having a reactive group is preferably 0 to 3% by mass based on the total mass of the polyolefin.

[0038] As the polyolefin, polyethylene, COP, or COC is preferable, polyethylene is more preferable, and low density polyethylene (LDPE) is still more preferable.

[0039] The polyolefin may be used alone or in combination of two or more. When the polymer film contains a polyolefin, the content is preferably 0.1% by mass or more, more preferably 5% by mass or more, based on the total mass of the polymer film, in terms of more excellent surface properties of the polymer film. The upper limit is not particularly limited, but in terms of more excellent smoothness of the polymer film, it is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 25% by mass or less, based on the total mass of the polymer film. Further, when the content of the polyolefin is 50% by mass or less, it is easy to sufficiently increase the heat distortion temperature and the soldering heat resistance can be improved.

[0040] (compatibilizing component) Examples of the compatibilizing component include a polymer having a portion highly compatible or having an affinity for the liquid crystal polymer (non-reactive compatibilizer), and a polymer having a reactive group for the phenolic hydroxyl group or carboxyl group at the terminal of the liquid crystal polymer (reactive compatibilizer). As the reactive group of the reactive compatibilizer, an epoxy group or a maleic anhydride group is preferable. As the compatibilizing component, a copolymer having a portion highly compatible or having an affinity for the polyolefin is preferable. Further, when the polymer film contains a polyolefin and a compatibilizing component, a reactive compatibilizer is preferable in terms of being able to finely disperse the polyolefin as the compatibilizing component. Note that the compatibilizing component (particularly the reactive compatibilizer) may form a chemical bond with a component such as a liquid crystal polymer in the polymer film.

[0041] Examples of the reactive compatibilizer include an epoxy group-containing polyolefin-based copolymer, an epoxy group-containing vinyl-based copolymer, a maleic anhydride-containing polyolefin-based copolymer, a maleic anhydride-containing vinyl copolymer, an oxazoline group-containing polyolefin-based copolymer, an oxazoline group-containing vinyl-based copolymer, and a carboxyl group-containing olefin-based copolymer. Among them, an epoxy group-containing polyolefin-based copolymer or a maleic anhydride-grafted polyolefin-based copolymer is preferable.

[0042] Examples of the epoxy group-containing polyolefin-based copolymer include an ethylene / glycidyl methacrylate copolymer, an ethylene / glycidyl methacrylate / vinyl acetate copolymer, an ethylene / glycidyl methacrylate / methyl acrylate copolymer, a polystyrene graft copolymer to an ethylene / glycidyl methacrylate copolymer (EGMA-g-PS), a polymethyl methacrylate graft copolymer to an ethylene / glycidyl methacrylate copolymer (EGMA-g-PMMA), and an acrylonitrile / styrene graft copolymer to an ethylene / glycidyl methacrylate copolymer (EGMA-g-AS). Examples of commercially available epoxy group-containing polyolefin copolymers include, for example, Bondfast 2C and Bondfast E manufactured by Sumitomo Chemical Co., Ltd.; Lotadar manufactured by Arkema; and Modiper A4100 and Modiper A4400 manufactured by NOF Corporation.

[0043] Examples of epoxy group-containing vinyl copolymers include, for example, glycidyl methacrylate graft polystyrene (PS-g-GMA), glycidyl methacrylate graft polymethyl methacrylate (PMMA-g-GMA), and glycidyl methacrylate graft polyacrylonitrile (PAN-g-GMA).

[0044] Examples of maleic anhydride-containing polyolefin copolymers include, for example, maleic anhydride graft polypropylene (PP-g-MAH), maleic anhydride graft ethylene / propylene rubber (EPR-g-MAH), and maleic anhydride graft ethylene / propylene / diene rubber (EPDM-g-MAH). Examples of commercially available maleic anhydride-containing polyolefin copolymers include, for example, the Orevac G series manufactured by Arkema; and the FUSABOND E series manufactured by The Dow Chemical Company.

[0045] Examples of maleic anhydride-containing vinyl copolymers include, for example, maleic anhydride graft polystyrene (PS-g-MAH), maleic anhydride graft styrene / butadiene / styrene copolymer (SBS-g-MAH), maleic anhydride graft styrene / ethylene / butene / styrene copolymer (SEBS-g-MAH), and styrene / maleic anhydride copolymer and acrylate / maleic anhydride copolymer. Examples of commercially available maleic anhydride-containing vinyl copolymers include the Tough Tech M series (SEBS-g-MAH) manufactured by Asahi Kasei Corporation.

[0046] Examples of compatible components include, among others, 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.

[0047] 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(vinyl pyridinium salt) ionomers, poly(vinyl trimethylammonium salt) ionomers, poly(vinyl benzyl phosphonium salt) ionomers, styrene-butadiene acrylic acid copolymer ionomers, polyurethane ionomers, sulfonated styrene-2-acrylamide-2-methylpropanesulfate ionomers, acid-amine ionomers, aliphatic ionenes, and aromatic ionenes.

[0048] 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.

[0049] (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 both a radical scavenging action and a peroxide decomposing action.

[0050] Examples of phenolic stabilizers include hindered phenolic stabilizers, semi-hindered fail 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 Shinko 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.

[0051] As the heat stabilizer, a hindered phenol stabilizer, a semi-hindered phenol stabilizer, or a phosphite stabilizer is preferable in terms of having a more excellent heat stabilization effect, and a hindered phenol stabilizer is more preferable. On the other hand, in terms of electrical properties, a semi-hindered phenol stabilizer or a phosphite stabilizer is more preferable.

[0052] 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.

[0053] (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.

[0054] Examples of the plasticizer include an alkyl phthalyl alkyl glycolate compound, a bisphenol compound (bisphenol A, bisphenol F), an alkyl phthalyl alkyl glycolate compound, a phosphate ester compound, a carboxylic acid ester compound, and a polyhydric alcohol. The content of the plasticizer may be 0 to 5% by mass based on the total mass of the polymer film. Examples of the lubricant include a fatty acid ester and a metal soap (for example, an inorganic salt 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. Examples of the UV absorber include a salicylate compound, a benzophenone compound, a benzotriazole compound, a substituted acrylonitrile compound, and an s-triazine compound. The content of the UV absorber may be 0 to 5% by mass based on the total mass of the polymer film.

[0055] 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.

[0056] <Physical properties of the polymer film> (Thickness) The thickness of the polymer film is preferably 5 to 1000 μm, more preferably 10 to 500 μm, and still 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).

[0057] (Dielectric properties) The standard dielectric tangent of the polymer film is not particularly limited, and is, for example, 0.0025 or less, preferably 0.0023 or less, more preferably 0.0020 or less, still more preferably 0.0015 or less, and particularly preferably 0.0010 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.

[0058] 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.

[0059] [Manufacturing method of polymer film] The manufacturing method of the polymer film is not particularly limited as long as it can manufacture a polymer film in which the void region in the cross section along the thickness direction satisfies the above requirements, 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 specific heat treatment and annealing treatment described later in the film-forming step can be mentioned. Hereinafter, the steps of producing a polymer film containing a liquid crystal polymer will be described in detail.

[0060] <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 pellets can be used.

[0061] (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.

[0062] (3) Raw Material Feeding Method The raw material feeding method may be a method of pre-mixing and supplying the raw materials before kneading and pelletizing, a method of separately supplying the raw materials into the extruder at a constant ratio, or a method combining both.

[0063] (4) Atmosphere during Extrusion When performing melt extrusion, it is preferable to prevent heat and oxidative degradation as much as possible within a range that does not hinder uniform dispersion. It is also effective to reduce the oxygen concentration by reducing the pressure using a vacuum pump or by flowing an inert gas. These methods may be carried out alone or in combination.

[0064] (5) Temperature The kneading temperature is preferably below the thermal decomposition temperature of the liquid crystal polymer and the additive, and is preferably as low as possible within a range where the load of the extruder and the reduction in uniform kneading property do not become problems.

[0065] (6) Pressure The kneading resin pressure during pelletization is preferably carried out at 0.05 to 30 MPa. In the case of a resin that is likely to generate coloring or gel due to shear, it is preferable to apply an internal pressure of about 1 to 10 MPa in the extruder to fill the resin raw material in the twin-screw extruder.

[0066] (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, pelletization may also be carried out by the underwater cutting method of directly extruding from the die into water while cutting after melting by an extruder, or by the hot cutting method of cutting while in a hot state.

[0067] (8) Pellet size The pellet size preferably has a cross-sectional area of 1 to 300 mm 2 and a length of 1 to 30 mm, more preferably a cross-sectional area of 2 to 100 mm 2 and a length of 1.5 to 10 mm.

[0068] (Drying) (1) Purpose of drying Before melt film formation, it is preferable to reduce the moisture and volatile components in the pellets, and drying the pellets is effective. When moisture or volatile components are contained in the pellets, it not only causes the appearance to deteriorate due to air bubbles being mixed into the polymer film or a decrease in haze, but also may cause a decrease in physical properties due to the molecular chain scission 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, it may be possible to suppress the formation of oxidation cross-linked products during melt film formation by removing dissolved oxygen by drying.

[0069] (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.

[0070] <Film formation process> Hereinafter, as the film formation process, the process of forming a polymer film by inflation molding using pellets containing a liquid crystal polymer will be described.

[0071] (Extrusion conditions) · Raw material drying Even in the melt plasticization process of the pellets by an extruder, it is preferable to reduce the moisture and volatile components in the same manner as in the pelletization process, and drying the pellets is effective.

[0072] · Raw material supply method When there are multiple types of raw materials (pellets) introduced from the supply port of the extruder, they may be premixed in advance (premix method), separately supplied 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 fluctuations in the temperature and bulk specific gravity of the raw materials introduced from the supply port. In terms 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, in terms 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 pseudo-pellets.

[0073] ·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 and performing decompression with a vacuum pump are also effective. These decompression and injection of inert gas can be carried out independently or in combination.

[0074] ·Rotation speed The rotation 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 rotation speed is above the lower limit value, the residence time becomes short, the decrease in molecular weight due to heat degradation can be suppressed, and discoloration can be suppressed. If the rotation 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 rotation speed from both aspects of uniform dispersibility and heat degradation due to extended residence time.

[0075] ·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 with 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 {T2 (°C) - 5 °C} to {T2 (°C) - 150 °C}, and the optimum value is selected in terms of ensuring the friction between the resin and the barrel, which becomes the driving force (feed force) for feeding the resin, and 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 practiced to actively cool and remove the shear heat generation. Also, in order to achieve both improved dispersibility and thermal degradation, a condition of melting and mixing at a relatively high temperature in the first half of the extruder and lowering the resin temperature in the second half is effective.

[0076] · Pressure The resin pressure in the extruder is generally 1 to 50 MPa, preferably 2 to 30 MPa, and more preferably 3 to 20 MPa in terms of extrusion stability and melt uniformity. If the pressure in the extruder is 1 MPa or more, the filling rate of the melt in the extruder is sufficient, so it is possible to suppress the destabilization of the extrusion pressure and the generation of foreign matters due to the occurrence of stagnant parts. Also, if the pressure in 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 the thermal decomposition due to the rise in the resin temperature.

[0077] · 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 additives can be achieved. If the residence time is 30 minutes or less, it is preferable in terms of suppressing resin deterioration and resin discoloration.

[0078] (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.

[0079] · 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 stacking 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 standard, 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 due to capturing foreign matters, it is necessary to stop the extruder and replace the filter, but a type that allows the filter to be replaced while continuing extrusion can also be used. Further, as a measure against the increase in filtration pressure due to capturing foreign matters, a filter having a function of reducing the filtration pressure by washing and removing the foreign matters captured by the filter in the reverse direction of the polymer flow path can also be used.

[0080] (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 in terms of ease of manufacturing the polymer film, it is preferable to manufacture the polymer film by the method according to this embodiment.

[0081] FIG. 1 is a 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.

[0082] 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 into it and its diameter increases, and is cooled by the cooling air flow ejected from a cooling blower 14 arranged 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.

[0083] 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 guide for the melt viscosity, 50 to 3500 Pa·s is preferable.

[0084] 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. Also, the draw ratio (Dr) in the MD direction is, for example, 1.0 to 5 times, preferably 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.

[0085] (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 are 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), it is considered that the void area ratio in the thickness direction of the cylindrical film F changes. Although the detailed mechanism of the change in the void area ratio in the thickness direction is not clear, the inventors of the present invention speculate that it is due to heating the film surface by reheating treatment while cooling the film surface immediately after heating so that the inflation film-forming property is not inhibited, and changing the crystal structure of the surface layer portion of the film by melting and rapid cooling.

[0086] The timing of performing the specific heat treatment is not particularly limited as long as it is before the cylindrical film solidifies. However, it is preferably performed after the draw ratio of the cylindrical film F in the expansion 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 of reheating the cylindrical film F can be adjusted. The same applies to the position of the cooler 18 and the timing of performing cooling.

[0087] The conditions of the specific heat treatment are appropriately adjusted according to the material constituting the polymer film, the target void area ratio, and the like. The temperature of reheating is preferably {Tm - 10} °C or higher, more preferably a temperature exceeding Tm, in terms of being able to make the hardness 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 temperature of reheating is preferably {Tm + 20} °C or lower, more preferably {Tm + 15} °C or lower. The treatment time of 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. As the heating means (heater 16) used for reheating, known heating means such as a hot air dryer and an infrared heater can be mentioned. Since the surface temperature of the film can be increased in a short time, an infrared heater is preferable. 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.

[0088] The cooling process in the specific heat treatment is preferably carried out 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 at a rate such that the surface temperature of the cylindrical film F is -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 viewpoint as above, the cooling process is preferably carried out until the surface temperature of the cylindrical film F falls 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.

[0089] 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, both end portions in the width direction of the flattened film are trimmed and separated into two films, and then each film is wound up by a winder (not shown) to obtain a polymer film.

[0090] (Relaxation treatment) In the present embodiment, a relaxation step of relaxing the strain existing inside the film by thermally shrinking the polymer film may be performed. In the thermal relaxation step, under tension (for example, about 2.0 to 3.0 kg / mm in the MD direction), 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. 2 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 above {Tm - 120}°C and more preferably above {Tm - 90}°C. Alternatively, the set temperature of the relaxation treatment is preferably about 200 to 290°C, and more preferably about 230 to 270°C.

[0091] (Annealing treatment) In the manufacturing method of the present embodiment, an annealing treatment of heating the polymer film to near its melting temperature is performed after a specific heat treatment. The annealing treatment is preferably performed after the specific heat treatment. Although the reason is not clear, after performing a cooling treatment during a specific heat treatment (preferably after further performing a relaxation treatment), by performing an annealing treatment, crystallization progresses in the surface layer region, the void region existing in the polymer film becomes smaller, the narrowing of the width of the void region occurs more remarkably in the thickness direction, and the ratio occupied by the domain region relatively increases. By performing a cooling treatment and an annealing treatment during a specific heat treatment and appropriately adjusting these conditions as necessary, a liquid crystal polymer film having specific void characteristics of the present invention can be manufactured.

[0092] Regarding the heating temperature in the annealing treatment, assuming the melting point of the liquid crystal polymer is Tm (°C), {Tm - 50} °C to {Tm + 30} °C is preferable, and more preferably exceeding {Tm + 10} °C and being {Tm + 25} °C or less. Regarding the heating time in the annealing treatment, 10 seconds to 24 hours is preferable, and 4 to 12 hours is more preferable. Particularly when the heating temperature is Tm or lower, in terms of easily manufacturing the polymer film of the present invention, the heating time is more preferably 4 to 12 hours, and even more preferably 8 to 12 hours. Examples of the heating means in the annealing treatment include a hot air drying furnace, a hot press (for example, a surface press or a heating roll), etc., and a hot press is preferable. As the annealing treatment, it may be performed on a composite body formed by laminating a polymer film on an adherend (for example, a metal foil such as a copper foil or an aluminum foil). By using the adherend, deformation etc. of the polymer film during heating can be suppressed. When performing an annealing treatment on the composite body, the adherend is peeled off from the annealed composite body to obtain the polymer film. After the above annealing treatment, a heat relaxation treatment may be further performed. In that case, the heat relaxation step is performed in accordance with the heat relaxation step performed before the above annealing treatment.

[0093] <Surface treatment> In order to further improve the peel strength of the metal-containing layer, it is preferable to perform a surface treatment on the polymer film. Examples of the surface treatment include, for example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, and acid or alkali treatment. The glow discharge treatment referred to here is 10 -3A low-temperature plasma occurring under a low-pressure gas of ~20 Torr may be used, and 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.

[0094] 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. Further, 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.

[0095] [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.

[0096] The laminate has at least one metal-containing layer and at least one polymer film. The number of metal-containing layers and polymer films 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 them, the laminate preferably has at least a layer structure in which a metal-containing layer, a polymer film, and a metal-containing layer are laminated in this order.

[0097] Further, the laminate may have a multilayer structure in which three or more metal-containing layers and two or more polymer films are alternately laminated. 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. A 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.

[0098] 〔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 metal. Examples 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.

[0099] As described later, the metal-containing layer is manufactured using, for example, 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 the 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 2.0 μm or less, more preferably 1.0 μm or less, and still more preferably 0.5 μm or less. The lower limit is not particularly limited, and for example, it is 0.1 μm or more, and preferably 0.3 μm or more. Examples of the metal foil having a surface roughness Ra within the above range include an unroughened copper foil, etc., and it can be obtained from 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 described later.

[0100] 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 the 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.

[0101] The laminate may have other layers other than the polymer film and the metal-containing layer, if necessary. Examples of the other layers include an adhesive layer, a rust preventive layer, and a heat resistant layer.

[0102] <Adhesive layer> The laminate preferably has an adhesive layer in terms of more excellent peel strength. 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 sides of the polymer film, it is preferably laminated in the order of the metal-containing layer, the adhesive layer, the polymer film, the adhesive layer, and the metal-containing layer.

[0103] As the adhesive 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 subsequent layer is not particularly limited, and examples thereof include a composition containing a binder resin and / or a reactive compound, and further containing an additive described later as an optional component.

[0104] (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 (e.g., 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.

[0105] 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.

[0106] (Reactive compound) The adhesive layer may contain a reaction product of a compound having a reactive group, and in addition to the above binder resin, it is preferable to further contain a reactive compound. In the present specification, a compound having a reactive group and its reaction product are also collectively referred to as "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.

[0107] 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).

[0108] 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’-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 2,3,3’,4’-biphenyltetracarboxylic 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).

[0109] Specific examples of the reactive compound having a carbodiimide group include monocarboxylic diimide compounds (for example, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide, di-β-naphthylcarbodiimide, and N,N'-di-2,6-diisopropylphenylcarbodiimide), and polycarbodiimide compounds (for example, compounds produced by the methods described in U.S. Patent No. 2,941,956, Japanese Patent Publication No. 47-033279, J. Org. Chem., Vol. 28, p2069-2075 (1963), and Chemical Review 1981, Vol. 81, No. 4, p. 619-621, etc.). Commercially available products of the reactive compound having a carbodiimide group include Carbodilite (registered trademark) HMV-8CA, LA-1, and V-03 (all manufactured by Nisshinbo Chemical Inc.), Stabaxol (registered trademark) P, P100, and P400 (all manufactured by Rhein Chemie), and Stabilizer 9000 (trade name, manufactured by Raschig Chemie), etc.

[0110] 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, 2 or more are preferable. That is, the reactive compound is preferably a crosslinking agent having 2 or more reactive groups. The number of reactive groups possessed by the crosslinking agent is more preferably 3 or more. The upper limit of the number of reactive groups possessed by the reactive compound or the crosslinking agent is not particularly limited, for example, it is 6 or less, and 5 or less is preferable. Examples of the reactive group possessed by the crosslinking agent include the above-described preferable reactive groups. The reactant of the compound having a reactive group is not particularly limited as long as it is a compound derived from the compound having a reactive group. For example, a reactant in which the reactive group of the compound having a reactive group reacts with a group containing an oxygen atom present on the surface of the polymer film can be mentioned.

[0111] 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.

[0112] The adhesive 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, and flame retardants. 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.

[0113] (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 more excellent peel strength of 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%, and more preferably 0.2 to 1.6% in terms of more excellent peel strength of the metal-containing layer. Note that the thickness of the adhesive layer described above is the thickness per one adhesive layer. The thickness of the adhesive layer can be measured according to the measurement method of the thickness of the polymer film described above.

[0114] [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.

[0115] <Step B> In Process B, a 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 pressure-bonded under high-temperature conditions to produce a laminate having the polymer film and the metal-containing layer. The polymer film and the metal foil used in Process B are 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 conditions for thermocompression bonding, {Tm - 80} to {Tm + 30} °C are preferable, and {Tm - 40} to Tm °C are more preferable. As the pressure conditions for thermocompression bonding, 0.1 to 20 MPa are preferable. The treatment time for the pressure-bonding treatment is preferably 0.001 to 1.5 hours.

[0116] 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 in which the polymer film and the metal foil are laminated by thermocompression bonding, the formed metal layer is subjected to an etching treatment or the like to form the above metal wiring. Further, 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, a vapor phase method such as a vacuum evaporation method, and a wet plating method.

[0117] <Adhesive layer formation process> When producing 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 of the polymer films using an adhesive composition is performed, and then Process B is performed using the obtained polymer film with the adhesive layer and the metal foil to obtain the laminate having the above adhesive layer.

[0118] As the subsequent layer forming step, for example, there is a step of applying an adhesive composition to at least one surface of a polymer film, and drying and / or curing the applied film as necessary to form an adhesive layer on the polymer film.

[0119] Examples of the adhesive composition include a composition containing components constituting the 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.

[0120] 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).

[0121] 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 means the components constituting the adhesive layer such as the above binder resin, reactive compound, and additive.

[0122] The method of attaching the adhesive composition onto the polymer film is not particularly limited, and examples thereof include a bar coating method, a spray coating method, a squeegee coating method, a flow coating method, a spin coating method, a dip coating method, a die coating method, an inkjet method, and a curtain coating method. When drying the 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 a laminate, after performing the step of forming an adhesive layer using the adhesive composition, the polymer film, the metal-containing layer, and (the adhesive layer) are laminated, and by performing the above-mentioned step B of thermocompression bonding the polymer film and the metal foil, the laminate of the present invention can be produced.

[0123] Note that the method for manufacturing the laminate of the present invention having a polymer film and a metal-containing layer is not limited to the above method. For example, the above adhesive composition is applied to at least one surface of the metal foil, and if necessary, the coating film is dried and / or cured to form an adhesive layer. Then, 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. Next, by thermocompression bonding the metal foil, the adhesive layer, and the polymer film according to the method described in step B, a laminate in which the polymer film, the adhesive layer, and the metal-containing layer are laminated in this order can be produced. Alternatively, 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.

[0124] The laminate manufactured by the above manufacturing method can be used for manufacturing the multilayer circuit board described above. For example, a patterning process is performed on the metal layer provided in the laminate (first laminate) manufactured by the above manufacturing method as necessary to form metal wiring. Then, the first laminate having the metal wiring and the second laminate in which a metal layer is bonded to one surface of an insulating layer made of a polymer film are laminated so 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.

[0125] 〔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

[0126] 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.

[0127] [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 of the above LCP1 and LCP2 are type II liquid crystal polymers composed of repeating units derived from p-hydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid. Moreover, the temperature at which the LCP1 and LCP2 crystallize upon melting was 250°C or higher and 290°C or higher, respectively. The recrystallization peak temperatures measured by the above method using a differential scanning calorimeter (DSC) are shown in Table 1 below.

[0128] <Metal foil> In the production of the metal foil 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.

[0129] [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.

[0130] [Film-forming step by inflation molding (Step A)] After preheating 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. 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.

[0131] Thereafter, using a manufacturing apparatus (inflation molding apparatus) having the following configuration, air was supplied to the internal space while cooling the outer surface of the discharged molten cylindrical film, and it was expanded by internal pressure. At this time, the stretching ratio was controlled so 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, a specific heat treatment was performed in which the cylindrical film that is stretched while moving upward was heated at a position where the draw ratio in the TD direction exceeds 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 that had been subjected to the specific heat treatment was flattened with pinch rolls, and then both end portions in the width direction were trimmed and wound up in film form.

[0132] Next, the produced film was introduced into a hot air drying oven set at 260 °C and heated while applying tension in the MD direction, thereby performing 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%.

[0133] Next, the anneal treatment was performed by introducing the relaxed film into a hot air drying oven set at 270 °C and heating for 10 hours. The film after the anneal treatment 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.

[0134] Each manufacturing condition 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 (melted): 13 kg / hr · Diameter of annular die: 50 mm · Slit width of annular die: 250 μm · Position of cooling ring: 30 mm vertically above the annular die · Temperature of gas blown out from 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 · Tensile direction expansion ratio: 4 times · Tensile direction expansion ratio / Machine direction expansion ratio: 3 · Take-up speed of the polymer film: 9.9 m / min

[0135] [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 Yurika 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 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 120 kg / cm in terms of surface pressure. 2

[0136] [Examples 2 and 3] The polymer films of Examples 2 and 3 were each manufactured according to the method described in Process A of Example 1, except that the annealing treatment was changed to the conditions described in Table 1 below. Next, the double-sided copper-clad laminates of Examples 2 and 3 were each produced according to the method described in Process B of Example 1, except that the manufactured polymer film was used.

[0137] [Example 4] ​The polymer film of Example 4 was produced according to the method described in Step A of Example 1, except that the annealing treatment was carried out by the method shown below. The annealing treatment in Example 4 was as follows. First, a composite was prepared by laminating a film relaxed on a substrate (copper foil). Next, using the obtained composite, hot pressing was carried out at 300 °C for 1 hour. The pressure applied to the composite was set to 40 kg / cm 2 in terms of surface pressure. Thereafter, the film was peeled off from the substrate after the annealing treatment to obtain an annealed film (the polymer film of Example 4). Next, the double-sided copper-clad laminate of Example 4 was produced according to the method described in Step B of Example 1, except that the produced polymer film was used.

[0138] [Example 5] The polymer film of Example 5 was produced according to the method described in Step A of Example 2, except that the annealing treatment was changed to the conditions described in Table 1 below. As Step B, the following adhesive composition was applied to both sides of the polymer film obtained in Step A, 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 dried adhesive layer 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 and the balance being a solvent (toluene). The double-sided copper-clad laminate of Example 5 was produced according to the method described in Step B of Example 1, except that the polymer film with an adhesive layer produced by the above method was used.

[0139] [Example 6] The polymer film of Example 6 was produced according to the method described in Step A of Example 3. Next, the double-sided copper-clad laminate of Example 6 was produced according to the method described in Step B of Example 5, except that the produced polymer film was used.

[0140] [Example 7] According to the method described in Step A of Example 4, the polymer film of Example 7 was produced. Subsequently, except for using the produced polymer film, the double-sided copper-clad laminate of Example 7 was produced according to the method described in Step B of Example 5.

[0141] [Example 8] According to the method described in Step A of Example 5, the polymer film of Example 8 was produced. Subsequently, except for using the produced polymer film and using two sheets of the above copper foil 2 instead of two sheets of copper foil 1, the double-sided copper-clad laminate of Example 8 was produced according to the method described in Step B of Example 1.

[0142] [Example 9] Except for using the above LCP2 instead of LCP1 as the raw material of the liquid crystal polymer and changing the heating temperature in the specific heat treatment to the conditions described in Table 1 below, the polymer film of Example 9 was produced in the same manner as the method described in Step A of Example 1. Subsequently, except for using the produced polymer film and setting the surface temperature of the heating metal roll to 290 °C, the double-sided copper-clad laminate of Example 9 was produced according to the method described in Step B of Example 1.

[0143] [Comparative Example 1] The polymer film of Comparative Example 1 was produced according to the method described in Step A of Example 1, except that the film formed by inflation molding was not annealed. Subsequently, except for using the produced polymer film, the double-sided copper-clad laminate of Comparative Example 1 was produced according to the method described in Step B of Example 1.

[0144] [Comparative Example 2] The polymer film of Comparative Example 2 was produced according to the method described in Step A of Example 1, except that the annealing treatment was changed to the conditions described in Table 1 below. Next, a double-sided copper-clad laminate of Comparative Example 2 was produced according to the method described in Step B of Example 1, except that the produced polymer film was used.

[0145] [Measurement and Evaluation] [Void Region of Polymer Film] The void region of the polymer film produced in each example was measured by the following method. The polymer film produced in each example was cut along the thickness direction at room temperature (25°C) using a diamond knife of a microtome. The polymer film with the exposed cross-section was immersed in monomethylamine at room temperature (25°C) for 4 hours, distilled water was dropped onto the cross-section for washing, and the water droplets were removed with an air duster. Then, the cross-section of the polymer film was photographed at an acceleration voltage of 2 kV and a magnification of 3000 times using a scanning electron microscope (SEM) ("S-4800 type" manufactured by Hitachi High-Technologies).

[0146] The photographed image was binarized using the Threshold function of the image processing software "ImageJ", the image was divided into a dark part and a bright part to obtain image processing data. The threshold value in the binarization was automatically determined by the image processing software between 88 and 105 of 256 gradations according to the contrast of the photographed image. The range of the photographed image was 15 μm in the thickness direction × 42 μm in the conveyance direction. The dark part in the binarized image processing data corresponds to the void region of the polymer film. From the binarized image processing data, the area of the dark part was automatically detected and measured, and the area of each void region was obtained from the obtained measurement values, and the average area of the void regions was obtained. Next, the dark part in the binarized image processing data was thinned using the thinning processing function of the above image processing software, and the length of each dark part was automatically detected and measured. For each void region, the average length of the voids was calculated from the data automatically detected and measured. The average value of the width of the void region was calculated by dividing the average area of the obtained void region by the average length of the obtained void region. Further, in the captured image of the cross-section, the first surface layer region with a distance of 5 μm or less from one surface, the second surface layer region with a distance of 5 μm or less from the other surface, and the middle layer region within 2.5 μm from the center line equidistant from both surfaces were each divided. Binary data was obtained from the captured images with n = 2, and the area ratio (void area ratio) of the void regions in each region was calculated. Each void area ratio means the ratio (%) of the total area of the voids in each region to the area of each region of the cross-section of the polymer film. Simultaneously with the above void area ratio, the area ratio of the void regions in the entire thickness direction of the cross-section of the polymer film was calculated.

[0147] 〔Dielectric Properties of Polymer Film〕 Using samples cut out so as to include the entire thickness direction of the polymer film manufactured in each example, the dielectric tangent in the 28 GHz band was measured in an environment of a temperature of 23°C and a humidity of 50% RH using a split cylinder resonator (CR-728 manufactured by Kanto Electronic Application Development Co., Ltd.) and a network analyzer (Keysight N5230A). As a result, the dielectric tangents of the polymer films manufactured in Examples 1 to 9 were all 0.0025 or less.

[0148] 〔Peel Test〕 The copper-clad laminate produced in each example was cut into strips of 1 cm × 5 cm to produce 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 peel test was carried out by using a tensile tester (Digital Force Gauge ZP-200N manufactured by IMADA Co., Ltd.) to peel the copper foil at a peel speed of 50 mm per minute in a direction forming a 90° angle with respect to the copper foil removal surface, and measuring the peel strength measured by the tensile tester. Further, the peeled surface of the peeled copper foil was observed to confirm the presence or absence of adhesion of the liquid crystal polymer. When the liquid crystal polymer adheres to the peeled surface of the copper foil, it means that cohesive failure has occurred in the polymer layer during peeling. When the liquid crystal polymer does not adhere to the peeled surface of the copper foil, it means that the bonding force between the domains in the polymer layer is strong and peeling has occurred at the interface between the copper foil and the polymer layer.

[0149] Table 1 below shows the production conditions of the polymer film, the production conditions of the metal foil laminate, the measurement results of the void region of the polymer film, 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 in the production of the polymer film in each example. The "Production of Polymer Film" column in Table 1 shows the methods and conditions of the specific heat treatment and annealing treatment in Step A. Also, in the "Peeled Surface" column of "Evaluation" in Table 1, "With LCP" indicates that the liquid crystal polymer adheres to the peeled surface of the peeled copper foil, and "Copper Foil Interface" indicates that the liquid crystal polymer does not adhere to the peeled surface of the peeled copper foil.

[0150] [Table 1]

[0151] [Table 2]

[0152] From the results shown in the above table, it was confirmed that the problems of the present invention can be solved by the liquid crystal polymer film of the present invention. [Explanation of Reference Numerals]

[0153] 10 Film-forming apparatus 12 Annular die 14 Cooling blower 16 Heater 18 Cooler

Claims

1. A liquid crystal 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, when a cross-section along the thickness direction of the liquid crystal polymer film is exposed, immersed in monomethylamine, and then a void region is extracted from an observation image of the cross-section obtained using an electron microscope, the average value of the width of the void region is 0.01 to 0.1 μm, and the area ratio of the void region in the observation image of the cross-section is 20% or less, A liquid crystal polymer film.

2. The liquid crystal 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 liquid crystal 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. The phenylene group, the naphthylene group, and the biphenylylene group may each have a substituent selected from the group consisting of a halogen atom, an alkyl group, and an aryl group.

4. The liquid crystal 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 p-hydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid.

5. The liquid crystal 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 liquid crystal polymer film according to any one of claims 1 to 5, wherein the average length of the void region is 3 to 5 μm.

7. The liquid crystal polymer film according to any one of claims 1 to 6, having a thickness of 15 μm or more and satisfying the following requirement A. Requirement A: In the cross section, a region within 5 μm from one surface of the liquid crystal polymer film is defined as the first surface layer region, a region within 5 μm from the other surface of the liquid crystal polymer film is defined as the second surface layer region, and when a region within 2.5 μm from a center line equidistant from both surfaces of the liquid crystal polymer film is defined as the central layer region, the area ratio of the void region in the central layer region is larger than the area ratio of the void region in the first surface layer region and larger than the area ratio of the void region in the second surface layer region.

8. The liquid crystal polymer film according to any one of claims 1 to 7, wherein the melting point of the liquid crystal polymer is 250 °C or higher.

9. Further comprising polyolefin, wherein the content of the polyolefin is 40% by mass or less based on the total mass of the liquid crystal polymer film. The liquid crystal polymer film according to any one of claims 1 to 8.

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

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

12. The laminate according to claim 10 or 11, wherein the surface roughness Ra of the surface of the metal-containing layer on the side facing the liquid crystal polymer film is 5 μm or less.

13. The laminate according to any one of claims 10 to 12, wherein the metal-containing layer is a copper layer.

14. The laminate according to any one of claims 10 to 13, further having an adhesive layer disposed between the metal-containing layer and the liquid crystal polymer film.

15. The laminate according to claim 14, wherein the adhesive layer is a layer formed using an adhesive composition containing a crosslinking agent having an epoxy group.

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