Liquid Crystal Polymer Film, Flexible Copper-Clad Laminate, and Method for Manufacturing Liquid Crystal Polymer Film

Abstract

The present invention provides a liquid crystal polymer film containing a liquid crystal polymer, having a melting point of 315° C. or higher and a number average molecular weight of 13,000 or higher and 150,000 or lower, a flexible copper-clad laminate, and a method for manufacturing the liquid crystal polymer film.

Description

Technical Field

[0001] The invention relates to a liquid crystal polymer film, a flexible copper-clad laminate and a method for manufacturing the liquid crystal polymer film. Background Art

[0002] Liquid crystal polymer (LCP) polymer films have low dielectric constants, high heat resistance, low hygroscopicity, and excellent high-frequency characteristics. Therefore, they are suitable for use as substrate films for circuit boards. In recent years, in particular, polymer films containing liquid crystal polymers have been developed for use as substrate films for circuit boards used in fifth-generation (5G) mobile communication systems.

[0003] However, because liquid crystal polymers (LCPs) have a rod-shaped molecular structure even in the molten state, they are easily oriented. When the LCPs are melted and extruded from a T-die for processing, the LCPs are subjected to shear stress in the die slit, causing the rod-shaped LC molecules to align along the machine direction (MD).

[0004] Therefore, a polymer film containing a liquid crystal polymer produced by melt extrusion becomes a film in which the liquid crystal polymer is uniaxially oriented in the MD direction and has strong anisotropy. As a result, a polymer film containing a liquid crystal polymer may have the disadvantage of being easily cleaved in the MD direction.

[0005] Therefore, research is underway to improve the drawback of polymer films containing liquid crystal polymers, namely, the tendency to crack.

[0006] For example, Patent Document 1 proposes a polymer film containing a thermoplastic liquid crystal polymer and an amorphous polymer.

[0007] Furthermore, Patent Document 2 proposes a polymer film including a liquid crystal polyester resin having a specific molecular weight distribution.

[0008] Furthermore, Patent Document 3 proposes a liquid crystal resin molded article characterized in that the mesogen group includes a liquid crystal polyarylate resin or a liquid crystal polyester amide resin in the main chain and has a specific surface area of 0.29 m 2 / g or above.

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-290512

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2020-33544

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 1-279922 Summary of the Invention

[0012] Technical issues to be solved by the invention

[0013] When the polymer film of Patent Document 1 improves tear resistance, the dielectric constant may be increased. In order to use the polymer film containing liquid crystal polymer as, for example, a substrate film for a circuit board, it is preferable that the dielectric constant be low. Therefore, when the polymer film of Patent Document 1 is used as, for example, a substrate film for a circuit board, the tear resistance may not be sufficiently improved.

[0014] The polymer film of Patent Document 2 is produced by applying a solution obtained by dissolving a liquid crystal polyester resin in a solvent to a support and then removing the solvent. To improve the tear resistance of the polymer film, it is preferable to increase the molecular weight of the liquid crystal polyester resin. However, increasing the molecular weight of the crystalline polyester resin sometimes reduces its solubility in solvents. Therefore, during the production process of the polymer film of Patent Document 2, the molecular weight of the liquid crystal polyester resin may not be sufficiently increased. As a result, the polymer film of Patent Document 2 may not have sufficiently improved tear resistance.

[0015] The liquid crystal resin molded product of Patent Document 3 is formed into fibers to obtain fibers with improved tear resistance. However, if the liquid crystal resin molded product of Patent Document 3 is formed into a film, the film forming properties may be reduced.

[0016] As described above, conventional polymer films composed of liquid crystal polymers are not excellent in both tear resistance and film forming properties.

[0017] The present invention has been accomplished in view of the above.

[0018] The problem to be solved by the embodiments of the present invention is to provide a liquid crystal polymer film, a flexible copper-clad laminate, and a method for producing a liquid crystal polymer film that have high tear resistance and excellent film forming properties.

[0019] Means for solving technical problems

[0020] The above-mentioned problems are solved by the following steps.

[0021] <1> A liquid crystal polymer film comprising a liquid crystal polymer,

[0022] The liquid crystal polymer film has a melting point of 315° C. or higher and a number average molecular weight of 13,000 or higher and 150,000 or lower.

[0023] <2> according to <1> The liquid crystal polymer film has a number average molecular weight of 18,000 or more and 150,000 or less.

[0024] <3> according to <1> or <2> The liquid crystal polymer film, wherein when the temperature is set to 5°C higher than the melting point and the shear rate is set to 1000sec -1When the melt viscosity of the liquid crystal polymer film is 80 Pa·s or more and 400 Pa·s or less.

[0025] <4> according to <1> to <3> The liquid crystal polymer film according to any one of the preceding claims, wherein the heat of crystal fusion obtained by differential scanning calorimetry is 2 J / g or less.

[0026] <5> according to <1> to <4> The liquid crystal polymer film according to any one of the preceding claims, which is used in a flexible printed circuit board.

[0027] <6> A flexible copper-clad laminate comprising <1> to <5> The liquid crystal polymer film according to any one of the preceding claims, and a copper foil disposed on at least one surface of the liquid crystal polymer film.

[0028] <7> A method for manufacturing a liquid crystal polymer film, comprising: <1> to <5> The method for producing a liquid crystal polymer film according to any one of the preceding claims comprises a film forming step of extruding the melt-kneaded liquid crystal polymer through a T-die to form a film.

[0029] <8> according to <1> to <5> The liquid crystal polymer film according to any one of the preceding claims, wherein

[0030] In a cross section cut along the thickness direction of the liquid crystal polymer film, when the elastic modulus at position A located at half the distance of the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is set as elastic modulus A, and the elastic modulus at position B located at 1 / 8 the distance of the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is set as elastic modulus B, the ratio B / A of the elastic modulus B to the elastic modulus A is less than 0.99, and the elastic modulus A is greater than 4.0 GPa.

[0031] <9> according to <8> The liquid crystal polymer film, wherein the elastic modulus A is greater than 4.6 GPa.

[0032] <10> according to <1> to <5> The liquid crystal polymer film according to any one of the preceding claims, wherein

[0033] After exposing a cross section cut along the thickness direction of the liquid crystal polymer film and immersing it in monomethylamine, when 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

[0034] The area ratio of the void region in the observed image of the cross section is 20% or less.

[0035] <11> according to <10> In the liquid crystal polymer film, the average length of the void region is 3 to 5 μm.

[0036] <12> according to <10> or <11> The liquid crystal polymer film, wherein

[0037] The thickness is 15 μm or greater and satisfies the following requirement A. Requirement A: In the cross section, when a region within 5 μm from one surface of the liquid crystal polymer film is defined as a first surface region, a region within 5 μm from the other surface of the liquid crystal polymer film is defined as a second surface region, and a region within 2.5 μm from a center line equidistant from both surfaces of the liquid crystal polymer film is defined as a central region, the area ratio of the void region in the central region is greater than the area ratio of the void region in the first surface region and greater than the area ratio of the void region in the second surface region.

[0038] <13> according to <1> to <5> The liquid crystal polymer film according to any one of the preceding claims, wherein

[0039] In a cross section taken along the thickness direction of the liquid crystal polymer film, when the hardness at a position A located at half the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is defined as hardness A, and the hardness at a position B located at 1 / 10 the thickness of the liquid crystal polymer film from the one surface toward the other surface of the liquid crystal polymer film is defined as hardness B, the relationship of the following formula (1A) is satisfied:

[0040] In the cross-section, when the position at 1 / 10 of the thickness of the liquid crystal polymer film is set as position T1, the position at 4 / 10 of the thickness of the liquid crystal polymer film is set as position T2, the position at 6 / 10 of the thickness of the liquid crystal polymer film is set as position T3, the area from the one surface to the position T1 is set as the S area, the area from the position T2 to the position T3 is set as the C area, the area ratio of the void area in the S area is set as the void area ratio X, and the area ratio of the void area in the C area is set as the void area ratio Y, the relationship of the following formula (2A) is satisfied.

[0041] Formula (1A) (Hardness A + Hardness B) / 2 ≥ 0.10 GPa

[0042] Formula (2A) Void area ratio Y - Void area ratio X ≥ 0.10%

[0043] <14> according to <13> The liquid crystal polymer film, wherein

[0044] The hardness A and the hardness B satisfy the relationship of the following formula (1B).

[0045] Formula (1B) (Hardness A - Hardness B) ≥ 0.02 GPa

[0046] <15> according to <1> to <5> or <8> to <14> The liquid crystal polymer film according to any one of the preceding claims has a single-layer structure.

[0047] <16> according to <1> to <5> or <8> to <15> The liquid crystal polymer film according to any one of the preceding claims, wherein the dielectric loss tangent of the liquid crystal polymer film at a temperature of 23° C. and a frequency of 28 GHz is 0.0022 or less.

[0048] <17> according to <1> to <5> or <8> to <16> The liquid crystal polymer film according to any one of the preceding claims, wherein the liquid crystal polymer has at least one member selected from the group consisting of repeating units derived from p-hydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid.

[0049] <18> according to <1> to <5> or <8> to <17> The liquid crystal polymer film according to any one of the preceding claims, wherein the liquid crystal polymer has at least one selected from the group consisting of repeating units derived from 6-hydroxy-2-naphthoic acid, repeating units derived from aromatic diol compounds, repeating units derived from terephthalic acid, and repeating units derived from 2,6-naphthalenedicarboxylic acid.

[0050] <19> according to <1> to <5> or <8> to <18> The liquid crystal polymer film according to any one of the preceding claims, further comprising a polyolefin,

[0051] The content of the polyolefin is 40% by mass or less based on the total mass of the liquid crystal polymer film.

[0052] Effects of the Invention

[0053] According to an embodiment of the present invention, a liquid crystal polymer film having high tear resistance and excellent film forming properties, a flexible copper-clad laminate, and a method for producing a liquid crystal polymer film are provided. DETAILED DESCRIPTION

[0054] Hereinafter, the liquid crystal polymer film, the flexible copper-clad laminate, and the method for producing the liquid crystal polymer film of the present invention will be described in detail.

[0055] The present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

[0056] In the present invention, the numerical range represented by "to" refers to a range that includes the numerical values recorded before and after "to" as the lower limit and the upper limit. In the numerical range described in stages in the present invention, the upper limit or lower limit described in a certain numerical range can be replaced by the upper limit or lower limit of the numerical range described in another stage. Furthermore, in the numerical range described in the present invention, the upper limit or lower limit described in a certain numerical range can be replaced by the value shown in the Examples.

[0057] In the present invention, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition unless otherwise specified.

[0058] In the notation of groups (atomic groups) in the present invention, the notation not indicating substitution or unsubstituted includes both groups having no substitution and groups having substitution. For example, the term "alkyl" includes not only alkyl groups having no substitution (unsubstituted alkyl groups) but also alkyl groups having substitution (substituted alkyl groups).

[0059] In the present invention, "(meth)acrylic acid" means both or either one of acrylic acid and methacrylic acid.

[0060] In the present invention, when the LCP film is long, the first direction refers to the width direction (short side direction, TD direction) of the LCP film, and the second direction refers to the longitudinal direction (MD direction) of the LCP film.

[0061] In the present invention, a combination of two or more preferred aspects is a more preferred aspect.

[0062] <Liquid Crystal Polymer Film>

[0063] The liquid crystal polymer film according to the present invention includes a liquid crystal polymer and has a melting point of 315° C. or higher and a number average molecular weight of 13,000 or higher and 150,000 or lower.

[0064] The liquid crystal polymer film according to the present invention has high tear resistance and excellent film forming properties due to the above-mentioned structure. The reason for this is presumably as follows.

[0065] In polymer films containing liquid crystal polymers, polymer films with high melting points (e.g., polymer films with a melting point of 315°C or higher) sometimes have low tear resistance or poor film-forming properties. To improve the tear resistance of polymer films with high melting points, it is necessary to increase the molecular weight of the polymer. However, increasing the molecular weight of the polymer sometimes results in a decrease in film-forming properties. Here, a decrease in film-forming properties refers to, for example, the generation of film ruptures or holes in the polymer film during extrusion when the polymer film is produced by melt extrusion.

[0066] On the other hand, the liquid crystal polymer film of the present invention comprises a liquid crystal polymer and has a melting point of 315°C or higher. Furthermore, the number average molecular weight of the liquid crystal polymer film of the present invention is 13,000 or higher and 150,000 or lower. By setting the number average molecular weight of the liquid crystal polymer film of the present invention to 13,000 or higher, the tear resistance of the polymer film can be improved. Furthermore, by setting the number average molecular weight of the liquid crystal polymer film of the present invention to 150,000 or lower, the polymer film has excellent film-forming properties.

[0067] From the above, it is inferred that the liquid crystal polymer film according to the present invention has high tear resistance and excellent film forming properties.

[0068] (Liquid Crystal Polymer)

[0069] Liquid crystal polymers include thermotropic liquid crystal polymers that exhibit liquid crystallinity in a molten state and lyotropic liquid crystal polymers that exhibit liquid crystallinity in a solution state.

[0070] The liquid crystal polymer may be in any form as long as it is melt-molded, but is preferably a thermotropic liquid crystal polymer.

[0071] The chemical composition of the thermotropic liquid crystal polymer is not particularly limited as long as it is a melt-moldable liquid crystal polymer. Examples of the thermotropic liquid crystal polymer include thermoplastic liquid crystal polyesters and thermoplastic polyester amides having amide bonds introduced into thermoplastic liquid crystal polyesters.

[0072] As the liquid crystal polymer, the thermoplastic liquid crystal polymer described in International Publication No. 2015 / 064437 can be used.

[0073] More specific examples of liquid crystal polymers include thermoplastic liquid crystal polyesters or thermoplastic liquid crystal polyester amides having repeating units derived from at least one selected from aromatic hydroxycarboxylic acids, aromatic or aliphatic diols, aromatic or aliphatic dicarboxylic acids, aromatic diamines, aromatic hydroxylamines, and aromatic aminocarboxylic acids.

[0074] Examples of aromatic hydroxycarboxylic acids include p-hydroxybenzoic acid, m-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and 4-(4-hydroxyphenyl)benzoic acid. These compounds may have substituents such as halogen atoms, lower alkyl groups, and phenyl groups. Among them, p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid are preferred.

[0075] The aromatic or aliphatic diol is preferably an aromatic diol. Examples of the aromatic diol include hydroquinone, 4,4'-dihydroxybiphenyl, 3,3'-dimethyl-1,1'-biphenyl-4,4'-diol, and acylates thereof. Preferably, it is hydroquinone or 4,4'-dihydroxybiphenyl.

[0076] As the aromatic or aliphatic dicarboxylic acid, an aromatic dicarboxylic acid is preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, with terephthalic acid being preferred.

[0077] Examples of the aromatic diamine, aromatic hydroxyamine, and aromatic aminocarboxylic acid include p-phenylenediamine, 4-aminophenol, and 4-aminobenzoic acid.

[0078] Furthermore, the liquid crystal polymer preferably has at least one type of repeating units selected from the group consisting of repeating units represented by the following formulae (1) to (3).

[0079] -O-Ar1-CO- (1)

[0080] -CO-Ar2-CO- (2)

[0081] -X-Ar3-Y- (3)

[0082] In formula (1), Ar1 represents a phenylene group, a naphthylene group or a biphenylene group.

[0083] In formula (2), Ar2 represents a phenylene group, a naphthylene group, a biphenylene group, or a group represented by the following formula (4).

[0084] In formula (3), Ar3 represents a phenylene group, a naphthylene group, a biphenylene group or a group represented by the following formula (4), and X and Y each independently represent an oxygen atom or an imino group.

[0085] -Ar4-Z-Ar5- (4)

[0086] 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.

[0087] The phenylene group, the naphthylene group, and the biphenylene group may have a substituent selected from a halogen atom, an alkyl group, and an aryl group.

[0088] Among them, the liquid crystal polymer preferably has at least one repeating unit selected from the group consisting of a repeating unit derived from an aromatic hydroxycarboxylic acid represented by the above formula (1), a repeating unit derived from an aromatic diol represented by the above formula (3) in which both X and Y are oxygen atoms, and a repeating unit derived from an aromatic dicarboxylic acid represented by the above formula (2).

[0089] Furthermore, the liquid crystal polymer more preferably has at least a repeating unit derived from an aromatic hydroxycarboxylic acid, further preferably has at least one selected from a repeating unit derived from p-hydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid, and particularly preferably has a repeating unit derived from p-hydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid.

[0090] Furthermore, as another preferred embodiment, from the viewpoint of achieving a more excellent effect of the present invention, the liquid crystal polymer more preferably has at least one repeating unit selected from the group consisting of repeating units derived from 6-hydroxy-2-naphthoic acid, repeating units derived from aromatic diols, repeating units derived from terephthalic acid, and repeating units derived from 2,6-naphthalenedicarboxylic acid, and further preferably has all of the repeating units derived from 6-hydroxy-2-naphthoic acid, repeating units derived from aromatic diols, repeating units derived from terephthalic acid, and repeating units derived from 2,6-naphthalenedicarboxylic acid.

[0091] When the liquid crystal polymer contains repeating units derived from an aromatic hydroxycarboxylic acid, the composition ratio thereof is preferably 50 to 65 mol% based on all repeating units in the liquid crystal polymer. Furthermore, the liquid crystal polymer preferably contains only repeating units derived from an aromatic hydroxycarboxylic acid.

[0092] When the liquid crystal polymer contains repeating units derived from an aromatic diol, the composition ratio thereof is preferably 17.5 to 25 mol % based on all the repeating units in the liquid crystal polymer.

[0093] When the liquid crystal polymer contains repeating units derived from an aromatic dicarboxylic acid, the composition ratio thereof is preferably 11 to 23 mol % based on all the repeating units in the liquid crystal polymer.

[0094] When the liquid crystal polymer contains repeating units derived from any one of aromatic diamine, aromatic hydroxyamine, and aromatic aminocarboxylic acid, the composition ratio thereof is preferably 2 to 8 mol % based on all the repeating units in the liquid crystal polymer.

[0095] When the liquid crystal polymer is a polymer containing structural units derived from p-hydroxybenzoic acid and structural units derived from 6-hydroxy-2-naphthoic acid, the molar ratio ((A) / (B)) of the structural units (A) derived from p-hydroxybenzoic acid to the structural units (B) derived from 6-hydroxy-2-naphthoic acid is preferably 10 / 90 to 90 / 10, more preferably 50 / 50 to 85 / 15, and even more preferably 60 / 40 to 80 / 20.

[0096] Commercially available liquid crystal polymers can be used, for example, "Laperos (product name)" manufactured by Polyplastics Co., Ltd., "Vectra" manufactured by Celanese Corporation, "UENO LCP" manufactured by UENO FINE CHEMICALS INDUSTRY. LTD., "Sumika SuperLCP" manufactured by Sumitomo Chemical Co., Ltd., "Zider" manufactured by ENEOS Corporation, and "Ciberus" manufactured by Toray Industries, Inc.

[0097] Furthermore, the liquid crystal polymer can form chemical bonds with an arbitrary component, ie, a cross-linking agent or a compatible component (reactive compatibilizer), in the liquid crystal polymer film. This also applies to components other than the liquid crystal polymer.

[0098] From the perspective of easily producing a liquid crystal polymer film having a low standard dielectric loss tangent (preferably 0.0025 or less), the standard dielectric loss tangent of the liquid crystal polymer is preferably 0.0022 or less, more preferably 0.0015 or less, and even more preferably 0.0010 or less. The lower limit is not particularly limited and may be, for example, 0.0001 or greater.

[0099] In addition, when the liquid crystal polymer film contains two or more liquid crystal polymers, the “dielectric loss tangent of the liquid crystal polymer” refers to the mass average value of the dielectric loss tangents of the two or more liquid crystal polymers.

[0100] The standard dielectric loss tangent of the liquid crystal polymer contained in the liquid crystal polymer film can be measured by the following method.

[0101] First, the liquid crystal polymer film is immersed in an organic solvent (e.g., pentafluorophenol) at a mass ratio of 1000 times the total mass of the film. The film is then heated at 120°C for 12 hours to elute the organic solvent-soluble components containing the liquid crystal polymer. The eluate containing the liquid crystal polymer is then filtered to separate the non-eluted components. Acetone is then added to the eluate as a poor solvent to precipitate the liquid crystal polymer, and the precipitate is separated by filtration.

[0102] The obtained precipitate is filled into a PTFE (polytetrafluoroethylene) hose (outer diameter 2.5 mm, inner diameter 1.5 mm, length 10 mm), and the dielectric properties are measured by the cavity resonator perturbation method using a cavity resonator (for example, "CP-531" manufactured by KANTO Electronic Application and Development Inc.) at a temperature of 23°C and a frequency of 28 GHz. The influence of the voids in the PTFE hose is corrected by the Bruggeman equation and the porosity, and the standard dielectric loss tangent of the liquid crystal polymer can be obtained.

[0103] The porosity (volume fraction of the voids within the hose) is calculated as follows. The volume of the space within the hose is calculated from the hose's inner diameter and length. Next, the mass of the filled precipitate is calculated using the hose's weight before and after filling with the precipitate. The volume of the filled precipitate is then calculated from the calculated mass and the specific gravity of the precipitate. The filling rate, and thus the porosity, can be calculated by dividing the volume of the precipitate thus calculated by the volume of the space within the hose calculated above.

[0104] When a commercially available liquid crystal polymer is used, the dielectric loss tangent value listed in the catalog of the commercially available product may be used.

[0105] From the viewpoint of achieving better heat resistance, the liquid crystal polymer preferably has a melting point Tm of 250° C. or higher, more preferably 280° C. or higher, and even more preferably 310° C. or higher.

[0106] 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, from the viewpoint of achieving better moldability.

[0107] The melting point Tm of the liquid crystal polymer can be determined by measuring the temperature at which the endothermic peak appears using a differential scanning calorimeter (DSC-60A manufactured by Shimadzu Corporation). When a commercially available liquid crystal polymer is used, the melting point Tm value listed in the commercial product catalog may also be used.

[0108] The number average molecular weight (Mn) of the liquid crystal polymer is not particularly limited, but is preferably 10,000 to 600,000, and more preferably 30,000 to 150,000.

[0109] The number average molecular weight of the liquid crystal polymer is a value converted to standard polystyrene based on gel permeation chromatography (GPC: Gel Permeation Chromatography).

[0110] GPC measurement can be performed using the following apparatus and conditions.

[0111] The measuring apparatus used was an "HLC (registered trademark)-8320GPC" manufactured by TOSOH CORPORATION, and two TSKgel (registered trademark) SuperHM-H columns (6.0 mm ID × 15 cm, manufactured by TOSOH CORPORATION) were used. The solvent (eluent) for dissolving the liquid crystal polymer is not particularly limited, and an example thereof includes a mixed solution of pentafluorophenol / chloroform = 1 / 2 (mass ratio). The measurement conditions included a sample concentration of 0.03 mass %, a flow rate of 0.6 ml / min, a sample injection volume of 20 μL, and a measurement temperature of 40°C. Detection was performed using an RI (differential refractometer) detector.

[0112] The calibration curve was prepared using eight samples of "TSK standard, polystyrene" manufactured by TOSOH CORPORATION: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0113] The liquid crystal polymer film may contain one type of liquid crystal polymer alone, or may contain two or more types of liquid crystal polymers.

[0114] The content of the liquid crystal polymer is preferably 40% to 100% by mass, more preferably 60% to 99% by mass, and particularly preferably 80% to 97% by mass relative to the total mass of the liquid crystal polymer film. The contents of the liquid crystal polymer and the components described below in the liquid crystal polymer film can be measured by known methods such as infrared spectroscopy and gas chromatography-mass spectrometry.

[0115] (Other ingredients)

[0116] The liquid crystal polymer film may contain other components in addition to the liquid crystal polymer. Examples of such other components include inorganic fillers, other polymers in addition to the liquid crystal polymer, crosslinking components, compatible components, plasticizers, stabilizers, lubricants, and colorants.

[0117] -Inorganic fillers-

[0118] The inorganic filler is not particularly limited, and examples thereof include talc, mica, aluminum oxide, titanium oxide, silicon oxide, silicon nitride, and carbon black.

[0119] The shape of the inorganic filler is not particularly limited, and examples thereof include spherical, flat, rod-like, needle-like, and irregular shapes. The average particle size (volume average particle size) of the inorganic filler is not particularly limited, but is preferably 0.050 μm to 10 μm.

[0120] The content of the inorganic filler is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, relative to the total mass of the liquid crystal polymer film. The upper limit of the content of the inorganic filler is preferably 20% by mass or less, more preferably 15% by mass or less, relative to the total mass of the liquid crystal polymer film.

[0121] -Polymers other than liquid crystal polymers-

[0122] Examples of polymers other than liquid crystal polymers include thermoplastic resins and elastomers. Furthermore, an elastomer refers to a polymer compound that exhibits elastic deformation. Specifically, it is a polymer compound that deforms in response to an applied external force and quickly returns to its original shape when the force is removed.

[0123] Examples of thermoplastic resins include polyurethane resins, polyester resins, (meth)acrylic resins, polystyrene resins, fluororesins, polyimide resins, fluorinated polyimide resins, polyamide resins, polyamideimide resins, polyetherimide resins, cellulose acylate resins, polyurethane resins, polyetheretherketone resins, polycarbonate resins, polyolefin resins (e.g., polyethylene resins, polypropylene resins, resins including cyclic olefin copolymers, alicyclic polyolefin resins), polyarylate resins, polyethersulfone resins, polysulfone resins, fluorene ring-modified polycarbonate resins, alicyclic-modified polycarbonate resins, fluorene ring-modified polyester resins, and the like.

[0124] (Polyolefin)

[0125] The polyolefin may be the above-mentioned thermoplastic polyolefin resin or the polyolefin-based elastomer described later, but is not limited thereto.

[0126] In this specification, "polyolefin" refers to a polymer having repeating units derived from olefins.

[0127] The liquid crystal polymer film preferably comprises a liquid crystal polymer and a polyolefin, and more preferably comprises a liquid crystal polymer, a polyolefin, and a compatible component.

[0128] The polyolefin may be linear or branched, and may have a cyclic structure, such as a polycycloolefin.

[0129] Examples of the polyolefin include polyethylene, polypropylene (PP), polymethylpentene (TPX manufactured by Mitsui Chemicals, Inc., etc.), hydrogenated polybutadiene, cycloolefin polymers (COP, Zeonor manufactured by Zeon Corporation, etc.), and cycloolefin copolymers (COC, Apel manufactured by Mitsui Chemicals, Inc., etc.).

[0130] The polyethylene may be any of high-density polyethylene (HDPE) and low-density polyethylene (LDPE). Furthermore, the polyethylene may be linear low-density polyethylene (LLDPE).

[0131] The polyolefin may be a copolymer of an olefin and a copolymerization component other than the olefin, such as an acrylate, methacrylate, styrene, and / or vinyl acetate-based monomer.

[0132] Examples of the polyolefin of the copolymer include styrene-ethylene / butylene-styrene copolymer (SEBS). SEBS may be hydrogenated.

[0133] However, from the viewpoint of achieving a more excellent effect of the present invention, it is preferred that the copolymerization ratio of the copolymer components other than the olefin be small, and more preferably no copolymer components be included. For example, the content of the copolymer components is preferably 0 to 40% by mass, more preferably 0 to 5% by mass, relative to the total mass of the polyolefin.

[0134] Furthermore, the polyolefin preferably contains substantially no reactive group described below, and the content of the repeating unit having a reactive group is preferably 0 to 3% by mass relative to the total mass of the polyolefin.

[0135] The polyolefin is preferably polyethylene, COP or COC, more preferably polyethylene, and still more preferably low-density polyethylene (LDPE).

[0136] The polyolefins may be used alone or in combination of two or more.

[0137] When the liquid crystal polymer film contains a polyolefin, its content is preferably 0.1% by mass or more, and more preferably 5% by mass or more, relative to the total mass of the liquid crystal polymer film, from the perspective of further improving the surface properties of the liquid crystal polymer film. While there is no particular upper limit, from the perspective of further improving the smoothness of the liquid crystal polymer film, it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less, relative to the total mass of the liquid crystal polymer film. Furthermore, when the polyolefin content is 50% by mass or less, it is easy to sufficiently increase the heat deformation temperature and improve solder heat resistance.

[0138] (elastomer)

[0139] The elastomer is not particularly limited, and examples thereof include elastomers containing repeating units derived from styrene (polystyrene-based elastomers), polyester-based elastomers, polyolefin-based elastomers, polyurethane-based elastomers, polyamide-based elastomers, polyacrylic-based elastomers, silicone-based elastomers, and polyimide-based elastomers. Furthermore, the elastomer may be a hydrogenated product.

[0140] Examples of the polystyrene elastomer include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), polystyrene-poly(ethylene-propylene) diblock copolymer (SEP), polystyrene-poly(ethylene-propylene)-polystyrene triblock copolymer (SEPS), polystyrene-poly(ethylene-butylene)-polystyrene triblock copolymer (SEBS), and polystyrene-poly(ethylene / ethylene-propylene)-polystyrene triblock copolymer (SEEPS).

[0141] The content of polymers other than the liquid crystal polymer is not particularly limited, but is preferably 0.5% by mass to 40% by mass, more preferably 1% by mass to 20% by mass, based on the total mass of the liquid crystal polymer film.

[0142] - Cross-linking component -

[0143] Examples of cross-linking components include epoxy-containing ethylene copolymers (e.g., ethylene-glycidyl methacrylate copolymers, ethylene-vinyl acetate-glycidyl methacrylate copolymers, ethylene-methacrylate-glycidyl methacrylate copolymers, poly(ethylene-glycidyl methacrylate)-graft-poly(acrylonitrile-styrene)), bisphenol-type epoxy compounds, carbodiimide compounds, and other compounds having reactive groups.

[0144] The content of the cross-linking component is preferably 0% by mass to 50% by mass relative to the total mass of the liquid crystal polymer film.

[0145] -Compatible ingredients-

[0146] Examples of the compatible component include oxazoline compatibilizers (e.g., bisoxazoline-styrene-maleic anhydride copolymers, bisoxazoline-maleic anhydride-modified polyethylene, bisoxazoline-maleic anhydride-modified polypropylene), elastic compatibilizers (e.g., styrene-ethylene-butadiene copolymers, styrene-ethylene-butadiene-styrene copolymers, hydrogenated styrene-isopropylene-styrene copolymers, aromatic resins, petroleum resins), reactive compatibilizers (e.g., ethylene glycidyl methacrylate copolymers, ethylene maleic anhydride ethyl acrylate copolymers, ethylene glycidyl methacrylate- Acrylonitrile styrene, acid-modified polyethylene wax, COOH-modified polyethylene graft polymer, COOH-modified polypropylene graft polymer) and copolymer compatibilizers (for example, polyethylene-polyamide graft copolymer, polypropylene-polyamide graft copolymer, methyl methacrylate-butadiene-styrene resin, acrylonitrile-butadiene rubber, ethylene vinyl acetate-polyvinyl chloride (EVA-PVC)-graft copolymer, vinyl acetate-ethylene copolymer resin, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, hydrogenated styrene-isopropyl-block copolymer).

[0147] In addition, as compatible components, ionomer resins such as ethylene-methacrylic acid copolymer ionomer, ethylene-acrylic acid copolymer ionomer, propylene-methacrylic acid copolymer ionomer, propylene-acrylic acid copolymer ionomer, butylene-acrylic acid copolymer ionomer, ethylene-vinylsulfonic acid copolymer ionomer, styrene-methacrylic acid copolymer ionomer, sulfonated polystyrene ionomer, fluorine-based ionomer, telechelic polybutadiene acrylic acid ionomer, sulfonated ethylene-propylene-diene copolymer ionomer, hydrogenated polypentamer ionomer, polypentamer ionomer, poly(vinylpyridinium salt) ionomer, poly(vinyltrimethylammonium salt) ionomer, poly(vinylbenzylphosphonium salt) ionomer, styrene-butadiene acrylic acid copolymer ionomer, polyurethane ionomer, sulfonated styrene-2-acrylamide-2-methylpropane sulfate ionomer, acid-amine ionomer, aliphatic ionene, and aromatic ionene can be used.

[0148] The content of the compatible component is preferably 0% by mass to 50% by mass relative to the total mass of the liquid crystal polymer film.

[0149] -Plasticizers, stabilizers, lubricants, organic particles-

[0150] Examples of the plasticizer include alkylphthalylalkyl glycolates, phosphates, carboxylates, and polyols. The content of the plasticizer is preferably 0% by mass to 20% by mass relative to the total mass of the liquid crystal polymer film.

[0151] Examples of the stabilizer include phosphite stabilizers (e.g., tris(4-methoxy-3,5-diphenyl)phosphite, tris(nonylphenyl)phosphite, and tris(2,4-di-tert-butylphenyl)phosphite), phenol stabilizers (e.g., 2,6-di-tert-butyl-4-methylphenol, 2,2-methylenebis(4-ethyl-6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 4,4-thiobis-(6-tert-butyl-3-methylphenol), 1,1,-bis(4-hydroxyphenyl)cyclohexane, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, epoxy compounds, and thioether compounds. The content of the stabilizer is preferably 0% by mass to 10% by mass relative to the total mass of the liquid crystal polymer film.

[0152] Examples of the lubricant include fatty acid esters and metal soaps (eg, inorganic stearic acid salts). The content of the lubricant is preferably 0% by mass to 5% by mass relative to the total mass of the liquid crystal polymer film.

[0153] Examples of the organic fine particles include cross-linked acrylic acid, cross-linked styrene, etc. The content of the organic fine particles is preferably 0% by mass to 50% by mass relative to the total mass of the liquid crystal polymer film.

[0154] (Melting Point)

[0155] The melting point of the liquid crystal polymer film of the present invention is 315° C. or higher.

[0156] By setting the melting point of the liquid crystal polymer film to 315° C. or higher, a liquid crystal polymer film that can withstand processing involving heating such as soldering can be obtained.

[0157] From the viewpoint of obtaining a liquid crystal polymer film that can withstand processing involving heating such as welding, the lower limit of the melting point of the liquid crystal polymer film is preferably 320°C or higher, more preferably 322°C or higher, and even more preferably 324°C or higher.

[0158] If the melting point of a liquid crystal polymer film is too high (for example, a melting point of 360°C or higher), high-temperature processing may be required during its manufacture. Therefore, separate manufacturing equipment capable of high-temperature processing is required, which may increase manufacturing costs. To reduce the manufacturing costs of the liquid crystal polymer film, the upper limit of the melting point of the liquid crystal polymer film may be 360°C or lower.

[0159] The melting point of the liquid crystal polymer film is a value measured using a differential scanning calorimeter under the following conditions: The melting point of the liquid crystal polymer film can be measured using, for example, DSC-50 (manufactured by SHIMADZU CORPORATION).

[0160] <Condition>

[0161] Measuring indoor atmosphere: Nitrogen

[0162] Heating rate: 20℃ / min

[0163] Measurement start temperature: 25°C

[0164] ·Measurement sample mass: 8mg

[0165] (number average molecular weight)

[0166] The number average molecular weight of the liquid crystal polymer film of the present invention is 13,000 or more and 150,000 or less.

[0167] By setting the number average molecular weight of the liquid crystal polymer film within the above range, a liquid crystal polymer film having high tear resistance and excellent film-forming properties can be obtained.

[0168] From the viewpoint of obtaining a liquid crystal polymer film having high tear resistance and excellent film-forming properties, the number average molecular weight of the liquid crystal polymer film is preferably 18,000 or more and 150,000 or less, more preferably 18,500 or more and 130,000 or less, further preferably 19,000 or more and 100,000 or less, even more preferably 19,000 or more and 35,000 or less, particularly preferably 19,000 or more and 30,000 or less, and most preferably 20,000 or more and 25,000 or less.

[0169] The number average molecular weight of the liquid crystal polymer film is measured using a gel permeation chromatography (GPC) analyzer. The measurement conditions are, for example, as shown below.

[0170] <Condition>

[0171] Column: TSKgel SuperHM-H (product name manufactured by TOSOH CORPORATION)

[0172] Solvent: PFP (pentafluorophenol) / chloroform = 1 / 2 (mass ratio)

[0173] Standard material: polystyrene

[0174] (Melt viscosity)

[0175] Regarding the liquid crystal polymer film of the present invention, when the temperature is set to 5° C. higher than the melting point and the shear rate is set to 1000 sec -1 The melt viscosity at this time is preferably 80 Pa·s or more and 400 Pa·s or less.

[0176] When the melt viscosity of the liquid crystal polymer film satisfies the above conditions, a liquid crystal polymer film having high tear resistance and excellent film-forming properties can be obtained more easily.

[0177] The reason for this is presumed to be as follows.

[0178] For example, in the production of liquid crystal polymer films using a melt extrusion method, when the melt viscosity satisfies the above-mentioned conditions, a liquid crystal polymer film with a large molecular weight can be easily and uniformly extruded during extrusion film formation. Therefore, when the melt viscosity satisfies the above-mentioned conditions, a liquid crystal polymer film with a large molecular weight can be easily obtained while suppressing the formation of film cracks or holes.

[0179] From the above, it is inferred that when the melt viscosity satisfies the above conditions, a liquid crystal polymer film having high tear resistance and excellent film-forming properties can be more easily obtained.

[0180] In order to obtain a liquid crystal polymer film having high tear resistance and excellent film forming properties, the liquid crystal polymer film was subjected to a shearing process at a temperature 5°C higher than the melting point of the liquid crystal polymer film and a shear rate of 1000 sec.-1 The melt viscosity at this time is more preferably 90 Pa·s or more and 350 Pa·s or less, and further preferably 100 Pa·s or more and 300 Pa·s or less.

[0181] The melt viscosity was determined by setting the cylinder temperature of the capillary rheometer to 5°C higher than the melting point of the sample and the shear rate to 1000 sec -1 , the value of apparent melt viscosity is measured according to ISO 11443 (1995).

[0182] The melt viscosity can be measured, for example, using a capillary rheometer (manufactured by Toyo Seiki Seisaku-sho, Ltd., trade name Capillograph 1D, barrel inner diameter 9.55 mm) using an orifice having an inner diameter of 1 mm and a length of 10 mm.

[0183] The melting point of the sample was measured under the same conditions as those for the above-described measurement of the melting point of the liquid crystal polymer film.

[0184] (Crystallization melting heat)

[0185] The liquid crystal polymer film of the present invention preferably has a crystal fusion heat value obtained by differential scanning calorimetry (hereinafter, also simply referred to as “crystal fusion heat value”) of 2 J / g or less.

[0186] By setting the crystal melting heat of the liquid crystal polymer film within the above range, it becomes easier to obtain a liquid crystal polymer film having excellent film-forming properties.

[0187] The reason for this is presumed to be as follows.

[0188] Setting the crystallization heat of fusion of the liquid crystal polymer film to 2 J / g or less facilitates a low-crystallization state when the liquid crystal polymer film is melted. This means, for example, that when the liquid crystal polymer film is produced by melt extrusion, the liquid crystal polymer film tends to be extruded uniformly during film formation. Therefore, by satisfying the above-mentioned crystallization heat of fusion, a liquid crystal polymer film with reduced cracking and void formation is easily obtained.

[0189] From the above, it is presumed that when the heat of crystal fusion satisfies the above conditions, a liquid crystal polymer film having excellent film-forming properties can be obtained more easily.

[0190] In addition, from the viewpoint of obtaining a liquid crystal polymer film with excellent film-forming properties, the crystal melting heat of the liquid crystal polymer film is preferably from 0.05 J / g to 1.5 J / g, more preferably from 0.1 J / g to 1.0 J / g, and even more preferably from 0.3 J / g to 0.8 J / g.

[0191] The crystal melting heat of the liquid crystal polymer film is a value measured using a differential scanning calorimeter, for example, DSC-50 (manufactured by Shimadzu Corporation). The measurement conditions are the same as those for the above-mentioned measurement of the melting point of the liquid crystal polymer film.

[0192] The melting point of the liquid crystal polymer film was measured under the conditions described above for measuring the melting point of the liquid crystal polymer. The heat of crystal fusion was calculated from the endothermic peak within the temperature range of -30°C to +30°C.

[0193] The thickness of the liquid crystal polymer film is preferably 5 μm to 1100 μm, more preferably 5 μm to 1000 μm, further preferably 5 μm to 250 μm, and particularly preferably 5 μm to 150 μm.

[0194] The thickness of the liquid crystal polymer film is measured as described in Examples below.

[0195] 〔Elastic modulus characteristics〕

[0196] In the liquid crystal polymer film involved in the present invention, in a cross-section cut along the thickness direction of the liquid crystal polymer film, when the elastic modulus at position A located at half the distance of the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is set as elastic modulus A, and the elastic modulus at position B located at 1 / 8 of the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is set as elastic modulus B, it is preferred that the ratio B / A of the elastic modulus B to the elastic modulus A (hereinafter also referred to as "specific elastic modulus ratio") is less than 0.99, and the elastic modulus A is greater than 4.0 GPa.

[0197] When the liquid crystal polymer film containing a liquid crystal polymer has a predetermined specific elastic modulus ratio and elastic modulus A, the liquid crystal polymer film and the metal foil in the laminate with the metal foil have excellent adhesion, and when a laminate is further laminated on the wiring formed by the metal foil, the performance of suppressing wiring positional shift is also improved. Although the mechanism is not yet clear, the present inventors speculate as follows. Specifically, it is speculated that if the elastic modulus A in the center portion of the liquid crystal polymer film in the thickness direction is greater than a predetermined value, the relative displacement of the metal-containing layers arranged on both surfaces of the liquid crystal polymer film in the in-plane direction can be suppressed, and even when other laminates are further laminated on the wiring, the positional shift of the wiring in the in-plane direction can be easily prevented. Furthermore, it is speculated that if the specific elastic modulus ratio is less than a predetermined value, while the elastic modulus of the liquid crystal polymer film as a whole is maintained, the elastic modulus at position B near the surface layer is relatively reduced, resulting in improved adhesion with the metal-containing layer laminated to the liquid crystal polymer film. This is thought to provide a LCP film having excellent adhesion to the metal foil in a laminate with metal foil and excellent performance in suppressing wiring positional deviation when a laminate is further laminated on wiring formed of the metal foil.

[0198] In addition, in this specification, with respect to a laminate produced by laminating a metal foil to a liquid crystal polymer film, when the adhesion between the liquid crystal polymer film and the metal foil is better and / or when a laminate is further laminated on the wiring formed by the metal foil, the performance of suppressing the position deviation of the wiring is better, it is also described as "the effect of adhesion and / or wiring position deviation is better".

[0199] From the viewpoint of achieving better adhesion and / or preventing wiring misalignment, the elastic modulus A of the liquid crystal polymer film at position A is preferably 4.3 GPa or more, more preferably 4.6 GPa or more. The upper limit is not particularly limited, but is, for example, 5.0 GPa or less.

[0200] Furthermore, from the perspective of achieving better adhesion and / or preventing wiring misalignment, the ratio of elastic modulus B to elastic modulus A (B / A), i.e., the specific elastic modulus ratio, is preferably 0.99 or less, more preferably 0.98 or less, and even more preferably 0.96 or less. While the lower limit is not particularly limited, from the perspective of suppressing misalignment during lamination, it is preferably 0.80 or more, and more preferably 0.85 or more.

[0201] From the viewpoint of achieving better adhesion and / or the effect of wiring position shift, the elastic modulus B at position B of the liquid crystal polymer film is preferably 3.7 to 4.95 GPa, more preferably 3.9 to 4.8 GPa.

[0202] The elastic modulus at the cross section of the liquid crystal polymer film is an indentation elastic modulus measured using a nanoindenter in accordance with ISO 14577. The specific measurement method is described in the examples below.

[0203] The elastic modulus (elastic modulus A and B) of the liquid crystal polymer film can be adjusted, for example, by heating and / or cooling the liquid crystal polymer film above the melting point Tm of the liquid crystal polymer during the film forming process, and changing these conditions (heating temperature, cooling rate, etc.) to control the orientation and crystallization structure of the liquid crystal polymer film in the thickness direction.

[0204] The specific elastic modulus ratio of the liquid crystal polymer film can be adjusted, for example, by performing the specific heat treatment described later during the film forming process of the liquid crystal polymer film, or performing heating and cooling on the manufactured liquid crystal polymer film in the same manner as the specific heat treatment described later, so as to control the orientation and crystallization structure in the thickness direction of the liquid crystal polymer film.

[0205] [Void Characteristics]

[0206] Regarding the liquid crystal polymer film of the present invention, after exposing a cross section cut along the thickness direction of the liquid crystal polymer film and immersing it in monomethylamine, when the void area is extracted from the observation image of the cross section obtained using an electron microscope, it is preferred that the average value of the width of the void area is 0.01 to 0.1 μm, and the area ratio of the void area in the observation image of the above-mentioned cross section (void area ratio) is less than 20%.

[0207] It is considered that, when a liquid crystal polymer film containing a liquid crystal polymer satisfies the above-mentioned requirement regarding the presence of voids in a cross section including the thickness direction, in a metal-clad laminate produced by stacking a liquid crystal polymer film and a metal foil, the peel strength of the metal foil is improved by suppressing the cohesive failure within the liquid crystal polymer film when the metal foil is peeled off from the liquid crystal polymer film.

[0208] While the mechanism for improving the peel strength of metal foil is not yet clear, the present inventors speculate as follows. Specifically, they believe that when the voids in the cross section in the thickness direction meet the aforementioned requirements, the space occupied by the substantial portion (domain region) composed of the liquid crystal polymer and the like in the liquid crystal polymer film is large, while the space occupied by the voids is small. Furthermore, the distance between the domain regions in the thickness direction is narrow, thereby increasing the adhesive force or cohesive force between the domain regions. As a result, in a metal-clad laminate produced by laminating metal foils, cohesive failure within the liquid crystal polymer film when the metal foil is peeled from the liquid crystal polymer film is suppressed, thereby improving the peel strength of the metal foil.

[0209] Hereinafter, in this specification, a laminate produced by laminating a liquid crystal polymer film and a metal foil together will also be described as “having better peel strength”.

[0210] In this specification, "void regions" refer to areas containing voids observed in an image of a cross section of a liquid crystal polymer film cut along its thickness, obtained using an electron microscope using a specified method. The area and size of the void regions are determined based on data obtained by imaging the cross section of the liquid crystal polymer film, exposed by cutting along its thickness, using a scanning electron microscope (SEM) and processing the image using image processing software (ImageJ). Specific measurement methods are described in the Examples below.

[0211] The liquid crystal polymer film of the present invention preferably has a void area ratio of 20% or less. From the perspective of achieving superior peel strength, the void area ratio of the liquid crystal polymer film is more preferably 15% or less, and even more preferably 10% or less. The lower limit is not particularly limited, but is, for example, 0.1% or more.

[0212] Furthermore, in the liquid crystal polymer film of the present invention, the average width of the void regions is preferably 0.01 to 0.1 μm, and more preferably 0.02 to 0.05 μm from the viewpoint of achieving a more excellent peel strength effect.

[0213] From the viewpoint of achieving better adhesion between domain layers, the average length of the void regions of the liquid crystal polymer film is preferably 0.5 to 10 μm, more preferably 1.0 to 8.0 μm, and even more preferably 3 to 5 μm.

[0214] For example, the area ratio of void regions and the average width and average length of void regions in a cross section in the thickness direction of the LCP film can be adjusted by performing an annealing treatment described later during the LCP film formation process.

[0215] From the viewpoint of achieving more excellent peel strength, the liquid crystal polymer film preferably has a thickness of 15 μm or more and satisfies the following requirement A.

[0216] Requirement A: In a cross section in the thickness direction, when the area within 5 μm from one surface of the liquid crystal polymer film is set as the first surface layer area, the area within 5 μm from the other surface of the liquid crystal polymer film is set as the second surface layer area, and the area within 2.5 μm from a center line equidistant from the two surfaces of the liquid crystal polymer film is set as the central layer area, the area ratio of the void area in the central layer area is greater than the area ratio of the void area in the first surface layer area, and greater than the area ratio of the void area in the second surface layer area.

[0217] From the perspective of achieving even better peel strength, the ratio of the void area ratio in the central layer region to the void area ratio in the first and second surface layer regions (hereinafter collectively referred to as the "surface layer regions") is preferably 120% or greater, more preferably 150% or greater. The upper limit is, for example, 300% or less, preferably 200% or less.

[0218] The void area ratio in the surface layer region varies depending on the void area ratio in the entire thickness direction, and is, for example, 0.1 to 30%, preferably 0.1 to 20%.

[0219] The void area ratio in the central layer region varies depending on the void area ratio in the entire thickness direction, and is, for example, 0.1 to 30%, preferably 5 to 20%.

[0220] In the liquid crystal polymer film, the area ratio of the void regions in the surface layer region and the central layer region can be adjusted by, for example, performing a specific heat treatment described later during the film formation step of the liquid crystal polymer film.

[0221] The liquid crystal polymer film of the present invention preferably satisfies the relationship of the following formula (1A), where the hardness at position A located halfway from one surface of the liquid crystal polymer film toward the other surface is defined as hardness A, and the hardness at position B located 1 / 10 of the thickness of the liquid crystal polymer film from the one surface of the liquid crystal polymer film toward the other surface is defined as hardness B. Furthermore, in the cross section, where the position located 1 / 10 of the thickness of the liquid crystal polymer film from the one surface of the liquid crystal polymer film toward the other surface is defined as position T1, the position located 4 / 10 of the thickness of the liquid crystal polymer film is defined as position T2, the position located 6 / 10 of the thickness of the liquid crystal polymer film is defined as position T3, the region from the one surface to position T1 is defined as region S, the region from position T2 to position T3 is defined as region C, the area ratio of the void region in the region S is defined as void area ratio X, and the area ratio of the void region in the region C is defined as void area ratio Y, preferably satisfies the relationship of the following formula (2A).

[0222] Formula (1A) (Hardness A + Hardness B) / 2 ≥ 0.10 GPa

[0223] Formula (2A) Void area ratio Y - Void area ratio X ≥ 0.10%

[0224] When the liquid crystal polymer film of the present invention satisfies formula (1A) and formula (2A), the dielectric loss tangent is low and the difference in linear expansion coefficient with the copper foil is likely to be small. The detailed reason for this is not clear, but it is roughly estimated as follows.

[0225] Liquid crystal polymer films with high hardness tend to exhibit low normalized dielectric loss tangent. Formula (1A) represents the relationship between the hardness of the central portion and the hardness of the surface layer of a liquid crystal polymer film. Liquid crystal polymer films that satisfy Formula (1A) can be said to have high overall hardness and are therefore presumed to exhibit low normalized dielectric loss tangent.

[0226] When a liquid crystal polymer film is used in the manufacture of a circuit board, it is used in the form of a laminate comprising the liquid crystal polymer film and copper foil. In this case, reducing the difference in the linear expansion coefficient between the liquid crystal polymer film and the copper foil is advantageous in suppressing warping of the laminate when the laminate is heated when the liquid crystal polymer film has high hardness, and in improving the adhesion between the liquid crystal polymer film and the copper foil.

[0227] The present inventors have found that the difference in linear expansion coefficient with copper foil can be reduced by using a liquid crystal polymer film that satisfies both the formula (1A) and the formula (2A).

[0228] The above formula (2A) represents the relationship between the void area ratio in the surface layer of a liquid crystal polymer film and the void area ratio in the center of the liquid crystal polymer film's thickness. The reason for this is unclear, but it is believed that when the void area ratio satisfies the relationship of formula (2A), the elongation in the thickness direction of the liquid crystal polymer film is controlled and the expansion in the in-plane direction is suppressed. As a result, even when using a liquid crystal polymer film with a high hardness such as that satisfying formula (1A), formula (2A) is satisfied, which is speculated to be the reason for the unexpectedly small difference in linear expansion coefficient with copper foil.

[0229] 〔hardness〕

[0230] Regarding the liquid crystal polymer film of the present invention, in a cross section cut along the thickness direction of the liquid crystal polymer film, when the hardness at position A located at half the distance of the thickness of the liquid crystal polymer film from one surface of the liquid crystal polymer film toward the other surface is set as hardness A, and the hardness at position B located at 1 / 10 of the thickness of the liquid crystal polymer film from one surface of the liquid crystal polymer film toward the other surface is set as hardness B, it is preferred to satisfy the relationship of the following formula (1A).

[0231] Formula (1A) (Hardness A + Hardness B) / 2 ≥ 0.10 GPa

[0232] From the perspective of providing a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient with copper foil, the lower limit of "(hardness A + hardness B) / 2" in formula (1A) is preferably greater than 0.12 GPa, more preferably greater than 0.14 GPa, and even more preferably greater than 0.16 GPa.

[0233] From the perspective of providing a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient with copper foil, the upper limit of "(hardness A + hardness B) / 2" in formula (1A) is preferably 0.30 GPa or less, more preferably 0.25 GPa or less, and even more preferably 0.20 GPa or less.

[0234] From the viewpoint of obtaining a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient from copper foil, the hardness A and the hardness B more preferably satisfy the relationship of formula (1B).

[0235] Formula (1B) (Hardness A - Hardness B) ≥ -0.02 GPa

[0236] From the perspective of making a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient with copper foil, the lower limit of "(hardness A-hardness B)" in formula (1B) is preferably -0.01 GPa or more, more preferably 0.00 GPa or more.

[0237] From the perspective of providing a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient with copper foil, the upper limit of "(hardness A - hardness B)" in formula (1B) is preferably 0.06 GPa or less, more preferably 0.04 GPa or less, and even more preferably 0.02 GPa or less.

[0238] From the viewpoint of making a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient from copper foil, the hardness A is preferably 0.10 to 0.25 GPa, more preferably 0.12 to 0.20 GPa.

[0239] From the viewpoint of making a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient from copper foil, the hardness B is preferably 0.12 to 0.30 GPa, more preferably 0.14 to 0.25 GPa.

[0240] The hardness in the cross section of the liquid crystal polymer film is an indentation hardness measured using a nanoindenter in accordance with ISO 14577. The specific measurement method is described in the examples below.

[0241] The value of "(hardness A+hardness B) / 2" in the liquid crystal polymer film can be adjusted by, for example, performing a specific heat treatment described later in the film forming process of the liquid crystal polymer film and controlling the amount of heat (temperature×time) in the annealing treatment described later.

[0242] Furthermore, the value of "(hardness A-hardness B)" in the liquid crystal polymer film can be adjusted, for example, by implementing the specific heat treatment described later in the film forming process of the liquid crystal polymer film and controlling the heat involved in the thickness direction of the liquid crystal polymer film in the annealing treatment described later.

[0243] [Void area ratio]

[0244] Regarding the liquid crystal polymer film of the present invention, in a cross-section cut along the thickness direction of the liquid crystal polymer film, when a position located at 1 / 10 of the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is set as position T1, a position located at 4 / 10 of the thickness of the liquid crystal polymer film is set as position T2, a position located at 6 / 10 of the thickness of the liquid crystal polymer film is set as position T3, an area from one surface to the above-mentioned position T1 is set as area S, an area from position T2 to position T3 is set as area C, an area ratio of voids in area S is set as area ratio X, and an area ratio of voids in area C is set as area ratio Y, it is preferred that the relationship of the following formula (2A) is satisfied.

[0245] Formula (2A) Void area ratio Y - Void area ratio X ≥ 0.10%

[0246] From the perspective of providing a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient with copper foil, the lower limit of "void area ratio Y - void area ratio X" in formula (2A) is preferably greater than 0.20%, and more preferably greater than 0.30%.

[0247] From the perspective of providing a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient with copper foil, the upper limit of "void area ratio Y-void area ratio X" in formula (2A) is preferably less than 0.70%, more preferably less than 0.60%, and further preferably less than 0.50%.

[0248] From the viewpoint of making a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient from copper foil, the void area ratio X is preferably 8 to 20%, more preferably 10 to 18%.

[0249] From the viewpoint of making a liquid crystal polymer film with a lower dielectric loss tangent and a smaller difference in linear expansion coefficient from copper foil, the void area ratio Y is preferably 10 to 22%, more preferably 12 to 20%.

[0250] The void area ratio in each region of a cross-section of a liquid crystal polymer film is the ratio (%) of the void area in each region to the area of each region of the cross-section of the liquid crystal polymer film. The void area ratio is calculated based on data obtained by immersing a liquid crystal polymer film cut so that the cross-section in the thickness direction is exposed, photographing the cross-section of the liquid crystal polymer film using a scanning electron microscope (SEM), and processing the captured image using image processing software (ImageJ). The specific measurement method is described in the Examples below.

[0251] Furthermore, the void area ratio (void area ratio X and Y) in the liquid crystal polymer film and the value of "void area ratio Y-void area ratio X" can be adjusted, for example, by performing a specific heat treatment described later in the film forming process of the liquid crystal polymer film, controlling the amount of heat (temperature × time) in the annealing treatment described later, and controlling the amount of heat applied to the liquid crystal polymer film in the thickness direction in the annealing treatment described later.

[0252] (Layer Structure)

[0253] The liquid crystal polymer film may have a single-layer structure or a laminated structure of a plurality of layers. In addition, the liquid crystal polymer film having a "single-layer structure" means that the liquid crystal polymer film is composed of the same material throughout its entire thickness.

[0254] (Dielectric properties)

[0255] The standard dielectric loss tangent of the liquid crystal polymer film is not particularly limited, and is, for example, 0.0025 or less, preferably 0.0024 or less, more preferably 0.0022 or less, further preferably 0.0020 or less, particularly preferably 0.0015 or less, and most preferably 0.0010 or less. The lower limit is not particularly limited and may be 0.0001 or greater.

[0256] The relative dielectric constant of the liquid crystal polymer film varies depending on its application, but is preferably 2.0 to 4.0, and more preferably 2.5 to 3.5.

[0257] The dielectric properties of the liquid crystal polymer film, including the standard dielectric loss tangent and relative dielectric constant, can be measured by the cavity resonator perturbation method. The specific method for measuring the dielectric properties of the liquid crystal polymer film is described in the Examples section below.

[0258] <Method for Manufacturing Liquid Crystal Polymer Film>

[0259] The method for producing the liquid crystal polymer film of the present invention is not particularly limited. For example, it preferably includes a pelletizing step of kneading the aforementioned components to obtain pellets, and a film-forming step of using the pellets obtained in the pelletizing step to obtain a liquid crystal polymer film. Hereinafter, the liquid crystal polymer film of the present invention may be simply referred to as a "film." Each step is described below.

[0260] 〔Granulation process〕

[0261] (Granulation)

[0262] The outline of the granulation sequence is as follows.

[0263] First, a liquid crystal polymer and an additive are melt-kneaded in a kneader, and then the melt-kneaded liquid crystal polymer and additive are cut and cooled to solidify to obtain pellets.

[0264] The details of granulation will be described below.

[0265] (1) Raw material form

[0266] The liquid crystal polymer used for film formation can also be used directly in the form of particles, flakes or powders, but for the purpose of stabilizing the film formation and uniformly dispersing the additives (indicating components other than the liquid crystal polymer. The same applies hereinafter). It is preferred to use an extruder to granulate one or more raw materials (indicating at least one of the liquid crystal polymer and the additive. The same applies hereinafter.) for use.

[0267] (2) Heating treatment of liquid crystal polymer

[0268] The liquid crystal polymer used for film formation may be subjected to a heat treatment, if necessary, for the purpose of adjusting the molecular weight of the liquid crystal polymer.

[0269] The heat treatment of the liquid crystal polymer is a treatment in which the liquid crystal polymer is stirred while being heated.

[0270] In the heat treatment of the liquid crystal polymer, the temperature of the liquid crystal polymer is preferably 240° C. or higher and 360° C. or lower.

[0271] In the heat treatment of the liquid crystal polymer, the method of stirring the liquid crystal polymer is not particularly limited as long as the liquid crystal polymer is heated uniformly.

[0272] The heat treatment of the liquid crystal polymer is preferably performed until the number average molecular weight of the liquid crystal polymer becomes 13000 to 150000. The number average molecular weight of the liquid crystal polymer can be measured in the same manner as the number average molecular weight of the liquid crystal polymer film.

[0273] The heat treatment time of the liquid crystal polymer is preferably 220 minutes or more and 1220 minutes or less.

[0274] (3) Drying or using ventilation holes instead of drying

[0275] The liquid crystal polymer and additives are preferably dried before pelletization. Examples of drying methods include circulating heated air with a low dew point and dehumidification by vacuum drying. Dehumidification by vacuum drying is particularly preferred when drying easily oxidizable resins. Furthermore, when circulating heated gas with a low dew point is used to dry easily oxidizable liquid crystal polymers, it is preferred to use a heated inert gas as the heating gas.

[0276] Furthermore, it is also possible to use a vent type extruder instead of drying. The vent type extruder has a single shaft and a double shaft type, and either type can be used. From the viewpoint of operating efficiency, the vent type extruder is preferably a double shaft type. When using a vent type extruder to extrude liquid crystal polymers and additives, the pressure in the extruder is preferably set to less than 1 atmosphere, more preferably to 0 atmosphere to 0.8 atmospheres, and even more preferably to 0 atmosphere to 0.6 atmospheres. In order to set the pressure in the extruder to the above range, it can be achieved by exhausting air from the vent or hopper provided in the kneading section of the extruder using a vacuum pump.

[0277] (4) Raw material supply method

[0278] The raw material supply method may be a method of preliminarily mixing the raw materials before kneading and supplying them to the extruder, a method of separately supplying the raw materials to the extruder so as to have a predetermined ratio, or a method combining both.

[0279] (5) Type of extruder

[0280] As the extruder, any known single-screw extruder, non-intermeshing counter-rotating twin-screw extruder, intermeshing counter-rotating twin-screw extruder, or intermeshing co-rotating twin-screw extruder can be used as long as a sufficient melt-kneading effect can be obtained.

[0281] (6) Atmosphere during extrusion

[0282] During melt extrusion, it is preferred to prevent thermal degradation and oxidative degradation as much as possible within a range that does not hinder uniform dispersion. Therefore, it is preferred to reduce the oxygen concentration in the extruder. As methods for reducing the oxygen concentration in the extruder, a method of reducing pressure using a vacuum pump or a method of inhaling an inert gas can be cited. These methods can be implemented alone or in combination.

[0283] (7) Speed

[0284] The screw speed of the extruder is preferably 10 rpm (revolutions per minutes: revolutions per minute, the same below.) to 1000 rpm, more preferably 20 rpm to 700 rpm, and particularly preferably 30 rpm to 500 rpm. Since the residence time of the raw material can be shortened by setting the rotation speed to be above the lower limit, the decrease in molecular weight due to thermal degradation or the significant coloration of the resin caused by thermal degradation can be suppressed. Furthermore, if the rotation speed is set to be below the upper limit, the severing of the molecular chain caused by the shearing of the raw material can be suppressed, thereby suppressing the decrease in molecular weight or the increase in the production of cross-linked gel. From the two aspects of uniform dispersibility and thermal degradation caused by the extension of the residence time, the screw speed is preferably selected under appropriate conditions.

[0285] (8) Temperature

[0286] The kneading temperature is preferably set below the thermal decomposition temperature of the resin and additives, and is preferably kept as low as possible within a range that does not pose a problem for the extruder load or uniform kneading performance. However, if the temperature is set too low, the melt viscosity increases. Conversely, the shear stress during kneading increases, sometimes causing molecular chain scission, so it is necessary to select an appropriate range. Furthermore, to achieve both improved dispersibility and reduced thermal degradation, it is also effective to perform melt mixing at a higher temperature in the first half of the extruder and then lower the resin temperature in the second half.

[0287] (9) Pressure

[0288] The mixing resin pressure during pelletization is preferably carried out at 0.05MPa to 30MPa. In the case of a resin that is easily colored or gelled due to shearing, it is preferred to apply an internal pressure of about 1MPa to 10MPa to the extruder so that the resin raw material is filled into the twin-screw extruder. As a result, since mixing can be carried out more effectively under low shear, uniform dispersion is promoted while suppressing thermal decomposition. The adjustment of the mixing resin pressure can be carried out by adjusting Q / N (the discharge amount per screw rotation) or by setting a pressure regulating valve at the outlet of the twin-screw mixing extruder.

[0289] (10) Shear and screw types

[0290] To evenly disperse the various raw materials, it's preferable to shear them. However, excessive shearing can sometimes lead to molecular chain severing or gel formation. Therefore, it's preferable to appropriately select the number and spacing of the rotor segments and kneading discs in the screw. Generally speaking, due to the larger gaps between the rotor segments, the shear rate tends to be lower than with kneading discs.

[0291] The shear rate (shear rate during granulation) is preferably 60 sec -1 ~1000 seconds -1, more preferably 100 sec -1 ~800 seconds -1 , especially preferably 200 sec -1 ~500 seconds -1 If the shear rate is above the lower limit, poor melting of raw materials and poor dispersion of additives can be suppressed. If the shear rate is below the upper limit, molecular chain scission can be suppressed, and a decrease in molecular weight and an increase in the generation of cross-linked gels can be suppressed.

[0292] (11) Residence time

[0293] The kneader residence time can be calculated based on the volume of the resin retention section in the kneader and the raw material discharge capacity. The raw material extrusion residence time during pelletization is preferably 10 seconds to 30 minutes, more preferably 15 seconds to 10 minutes, and particularly preferably 30 seconds to 3 minutes. As long as sufficient melting conditions are ensured, resin degradation and discoloration can be suppressed, so a shorter residence time is preferred.

[0294] (12) Pelletization method

[0295] Granulation refers to the process of forming the resin into pellets.

[0296] The usual method for granulation is to extrude the resin into a noodle shape, solidify it in water, and then cut it. However, the resin can also be melted by an extruder and then pelletized by an underwater cutting method in which the resin is directly extruded through a die in water while being cut, or by a thermal cutting method in which the resin is cut in a hot state.

[0297] (13) Particle size

[0298] The particle size is preferably 1 mm in cross section. 2 ~300mm 2 , length is 1mm to 30mm, and the cross-sectional area is particularly preferably 2mm 2 ~100mm 2 , length is 1.5mm~10mm.

[0299] (14) Other granulation

[0300] Pellets are generally formed by melt kneading using an extruder. Alternatively, a method of preparing a uniform dispersion solution using a common solvent for the liquid crystal polymer and additives and then solidifying the liquid crystal polymer and additives by removing the solvent may be used.

[0301] Examples of the solvent include methanol, ethanol, acetone, methyl ethyl ketone, diethyl ether, ethyl acetate, butyl acetate, and dichloromethane.

[0302] From the viewpoint of efficiency and dispersibility, the raw material concentration of the uniform dispersion solution is preferably 1 to 50 mass %, more preferably 3 to 35 mass %, and particularly preferably 5 to 30 mass % relative to the entire uniform dispersion solution.

[0303] Solidification can be achieved by drying the solvent after dissolution (drying method), or by placing the dissolved substance into a poor solvent to precipitate the substance (precipitation method).

[0304] (dry)

[0305] (1) Purpose of drying

[0306] Before melt film formation, it is preferable to reduce the moisture and volatile components in the particles, and drying the particles is effective. The presence of moisture and volatile components in the particles can sometimes lead to bubbles incorporating into the film being formed, or a decrease in haze, resulting in a poor appearance. Furthermore, this can sometimes cause degradation of physical properties due to severing of the liquid crystal polymer's molecular chains, or roller contamination due to the formation of monomers or oligomers. Furthermore, depending on the type of liquid crystal polymer used, drying can sometimes be used to remove dissolved oxygen, thereby suppressing the formation of oxidative crosslinks during melt film formation.

[0307] (2) Drying method and heating method

[0308] Regarding the drying method, a dehumidified hot air dryer is generally used from the viewpoint of drying efficiency and economy, but there is no particular limitation as long as the target moisture content can be achieved. Furthermore, a more appropriate drying method can be selected based on the physical properties of the liquid crystal polymer.

[0309] Examples of the heating method include pressurized steam, heating with a heater, far-infrared irradiation, microwave heating, and heating medium circulation heating.

[0310] From the viewpoint of more efficient energy use and uniform drying by reducing temperature variations, it is preferred that the drying equipment be a heat-insulating structure.

[0311] The particles may be stirred to improve drying efficiency. The drying method is not limited to one method, and multiple methods may be combined.

[0312] (3) Device form

[0313] There are two types of drying methods: continuous and batch drying. Among the drying methods using vacuum, batch drying is preferred. On the other hand, among the drying methods in a steady state, continuous drying is preferred.

[0314] (4) Atmosphere and air volume

[0315] When drying the granules, it is preferable to blow gas.

[0316] When drying the pellets, examples of the gas to be blown include air and inert gas.

[0317] The dew point of air or inert gas is preferably 0°C to -60°C, more preferably -10°C to -55°C, and particularly preferably -20°C to -50°C. A low dew point is preferred from the perspective of reducing volatile components in the pellets, but this is disadvantageous from an economical perspective. Therefore, an appropriate range may be selected.

[0318] When the raw material is easily oxidized, it is also effective to use an inert gas to reduce the oxygen partial pressure.

[0319] When drying the pellets, the air volume required per ton of liquid crystal polymer is preferably 20 m 3 / hour~2000m 3 / hour, more preferably 50m 3 / hour~1000m 3 / hour, particularly preferably 100m 3 / hour~500m 3 / hour. If the drying air volume is above the lower limit, the drying efficiency is improved. If the drying air volume is below the upper limit, it is economically preferred.

[0320] Alternatively, the particles may be dried under reduced pressure.

[0321] (5) Temperature and time

[0322] As for the drying temperature, when the raw material is in an amorphous state, it is preferably {glass transition temperature (Tg) (℃) -1℃} to {Tg (℃) -100℃} (that is, a temperature 1℃ to 100℃ lower than Tg), more preferably {Tg (℃) -5℃} to {Tg (℃) -60℃}, and particularly preferably {Tg (℃) -10} to {Tg (℃) -40℃}.

[0323] If the drying temperature is below the upper limit, agglomeration (a phenomenon in which particles adhere to each other and become difficult to separate) caused by softening of the resin can be suppressed, thereby improving conveyability. On the other hand, if the drying temperature is above the lower limit, drying efficiency can be improved and the moisture content can be adjusted to a desired value.

[0324] Furthermore, when the raw material is a crystalline resin, if the melting point (Tm) is below 30°C, the resin can be dried without melting. Setting the drying temperature too high may cause coloration or changes in molecular weight (usually decreasing, but increasing depending on the situation). Furthermore, excessively low drying temperatures also reduce drying efficiency, so appropriate conditions must be selected. As an indicator, a temperature range of Tm (°C) - 150°C to Tm (°C) - 50°C is preferred.

[0325] The drying time is preferably more than 15 minutes, more preferably more than 1 hour, and especially preferably more than 2 hours. In addition, even if the drying exceeds 50 hours, the effect of further reducing the water content is also small. Due to concerns about the thermal deterioration of the resin, there is no need to set the drying time too long.

[0326] (6) Moisture content

[0327] The water content of the granules is preferably 1.0% by mass or less, more preferably 0.1% by mass or less, and particularly preferably 0.01% by mass or less, relative to the entire granules.

[0328] (7) Transportation method

[0329] In order to prevent moisture from being reabsorbed into the dried pellets, the pellets are preferably conveyed under a dry air or dry nitrogen atmosphere. Furthermore, heated dry air is generally used for stable extrusion.

[0330] [Film-making process]

[0331] The film forming step is not particularly limited, but is preferably a step of extruding the melt-kneaded liquid crystal polymer (ie, pellets) through a die to form a film.

[0332] Hereinafter, the production apparatus used in the film forming step and the film forming procedure will be described.

[0333] (Manufacturing equipment)

[0334] Hereinafter, an example of each device constituting the manufacturing apparatus will be described.

[0335] (Extruder, Screw, and Barrel (hereinafter, the barrel is also referred to as "barrel"))

[0336] (1) Extruder

[0337] A known melt extruder can be used as the extruder, and examples of the extruder include single-screw extruders such as full-screw, mudock, and dalmage screw extruders, and co-rotating or counter-rotating twin-screw extruders.

[0338] (2) Type of extruder

[0339] Examples of the extruder include a single-screw extruder and a twin-screw (or multi-screw) extruder.

[0340] Twin-screw (or multi-screw) extruders are generally classified into intermeshing type and non-intermeshing type, but are not particularly limited. Furthermore, the screw rotation direction of a twin-screw (or multi-screw) extruder can be classified into co-rotating or counter-rotating, but is not particularly limited.

[0341] (3) Type and structure of screw

[0342] Here, an example of a screw for a uniaxial extruder is shown. Examples of the screw include a full-flight screw and a double-flight screw. Furthermore, in order to improve the kneading properties within the extruder, the screw may have mixing elements such as a mudock, a dalmage, or a barrier.

[0343] Diameter and groove depth

[0344] The screw diameter varies depending on the target extrusion volume per unit time, and is preferably 10 mm to 300 mm, more preferably 20 mm to 250 mm, and particularly preferably 30 mm to 150 mm. The groove depth of the supply portion of the screw is preferably 0.05 to 0.20 times the screw diameter, more preferably 0.07 to 0.18 times, and particularly preferably 0.08 to 0.17 times. The pitch is not particularly limited, but is preferably set to the same value as the screw diameter. Furthermore, the thread groove width is preferably 0.05 to 0.25 times relative to the screw pitch. The gap between the thread and the barrel is preferably 0.001 to 0.005 times relative to the screw diameter, and is more preferably 0.0015 to 0.004 times from the perspective of friction between the barrels and reducing the retention portion.

[0345] Compression rate

[0346] The screw compression ratio of the extruder is preferably 1.6 to 4.5. The screw compression ratio is expressed as the volume ratio of the supply section to the measuring section, that is, (volume per unit length of the supply section) ÷ (volume per unit length of the measuring section). The screw compression ratio is calculated using the outer diameter of the screw shaft of the supply section, the outer diameter of the screw shaft of the measuring section, the groove diameter of the supply section, and the groove diameter of the measuring section. If the screw compression ratio is 1.6 or more, sufficient melt kneading properties can be obtained, and the generation of undissolved parts can be suppressed. If the screw compression ratio is 4.5 or less, excessive application of shear stress can be suppressed. Specifically, it is possible to suppress the decrease in mechanical strength of the film caused by molecular chain severance, the overheating coloration phenomenon caused by shear heat, and the decrease in foreign matter level caused by the generation of gel. Therefore, the appropriate screw compression ratio is preferably 1.6 to 4.5, more preferably 1.7 to 4.2, and particularly preferably 1.8 to 4.0.

[0347] L / D

[0348] L / D refers to the ratio of the cylinder length to the cylinder inner diameter. If L / D is 20 or more, melting and mixing are insufficient, and the generation of undissolved foreign matter in the film after manufacture can be suppressed, similar to the case where the compression ratio is appropriate. In addition, if L / D is 70 or less, the residence time of the liquid crystal polymer in the extruder is shortened, thereby suppressing the degradation of the resin. In addition, if L / D is 70 or less, the decrease in the mechanical strength of the film caused by the decrease in molecular weight due to the severance of the molecular chain can be suppressed. Therefore, L / D is preferably in the range of 20 to 70, more preferably 22 to 65, and particularly preferably 24 to 50.

[0349] Screw ratio

[0350] The length of the extruder's feed section is preferably set to 20% to 60% of the effective screw length (the total length of the feed section, compression section, and measuring section), and more preferably 30% to 50%. The length of the extruder's compression section is preferably set to 5% to 50% of the effective screw length, preferably 5% to 40% for crystalline resins and 10% to 50% for amorphous resins. The length of the measuring section is preferably 20% to 60% of the effective screw length, and more preferably 30% to 50%. The measuring section is typically divided into multiple sections, and mixing elements are placed between them to improve kneading performance.

[0351] Q / N

[0352] The discharge volume per screw rotation (Q / N) is preferably the theoretical maximum discharge volume (Q / N). MAX 50% to 99% of the total discharge volume, more preferably 60% to 95%, and particularly preferably 70% to 90%. 3 / min], N represents the screw speed [rpm]. If the discharge volume per screw rotation (Q / N) is the theoretical maximum discharge volume (Q / N) MAX If the extruder is more than 50% of the original extruder, the residence time in the extruder can be shortened and the thermal degradation inside the extruder can be suppressed. In addition, the discharge volume (Q / N) per screw rotation is the theoretical maximum discharge volume (Q / N). MAX When the back pressure is 99% or less, the kneading property is improved because the back pressure is sufficient, and not only the melting uniformity is improved but also the stability of the extrusion pressure becomes good.

[0353] (4) Extrusion conditions

[0354] ·dry

[0355] In the melt-plasticizing step of pellets using an extruder, it is also preferred to reduce the amount of water and volatile components, similarly to the pelletizing step, and it is effective to dry the pellets.

[0356] Raw material supply method

[0357] When multiple raw materials (pellets) are fed into the extruder's feed port, they can be pre-mixed (pre-mixing method), fed separately so that they are in a predetermined ratio within the extruder, or a combination of the two methods can be used. Furthermore, to stabilize extrusion, the temperature of the raw materials fed into the feed port and the control to reduce fluctuations in the bulk specific gravity can be performed. Furthermore, from the perspective of plasticization efficiency, the raw material temperature is preferably high as long as it is within a range that does not cause agglomeration at the feed port due to adhesion. In the case of an amorphous state, the preferred range is {glass transition temperature (Tg) (°C) -150°C} to {Tg (°C) -1°C}, and in the case of a crystalline resin, the preferred range is {melting point (Tm) (°C) -150°C} to {Tm (°C) -1°C}. Furthermore, from the perspective of plasticization efficiency, the bulk specific gravity of the raw material is preferably at least 0.3 times that of the molten state, and particularly preferably at least 0.4 times. When the bulk specific gravity of the raw material is less than 0.3 times that of the molten state, processing such as compressing the raw material to simulate pelletization is performed.

[0358] ·Atmosphere during extrusion

[0359] The atmosphere during melt extrusion is similar to that in the pelletizing step. Within a range that does not hinder uniform dispersion, it is also effective to inject an inert gas (such as nitrogen), use a vacuum hopper to reduce the oxygen concentration in the extruder, or provide a vent hole in the extruder to reduce pressure using a vacuum pump. These decompression and inert gas injection can be implemented independently or in combination.

[0360] Speed

[0361] The screw speed of the extruder is preferably 5 rpm to 300 rpm, preferably 10 rpm to 200 rpm, and particularly preferably 15 rpm to 100 rpm. If the screw speed is above the lower limit, the residence time of the resin in the extruder becomes shorter, thereby suppressing the decrease in molecular weight caused by thermal degradation of the resin and suppressing discoloration of the resin. If the speed is below the upper limit, the severing of molecular chains caused by shearing can be suppressed, and the decrease in molecular weight or the increase in cross-linked gel can be suppressed. From the viewpoint of uniform dispersibility and suppressing thermal degradation caused by the extension of the residence time, the screw speed is preferably selected under appropriate conditions.

[0362] ·temperature

[0363] The barrel temperature (supply section temperature T1°C, compression section temperature T2°C, and measurement section temperature T3°C) is usually determined by the following method. When the pellets are melted and plasticized at the target temperature T°C through the extruder, the measurement section temperature T3 is set to T±20°C in consideration of the shear heat generation. At this time, T2 is set in consideration of the extrusion stability and the thermal decomposition of the resin within the range of T3±20°C. T1 is usually set to {T2(°C)-5°C}~{T2(°C)-150°C}, and the optimal value is selected from the perspective of ensuring the friction between the resin and the barrel, which is the driving force (feed force) for conveying the resin, and preheating in the feed section. In the case of a normal extruder, the temperatures of each region T1 to T3 can be subdivided to set the temperature. By setting the temperature change between each region to be smooth, the extrusion can be further stabilized. At this time, T is preferably set below the thermal degradation temperature of the resin. When the thermal degradation temperature is exceeded by the shear heat generated by the extruder, the shear heat is usually actively cooled to remove the shear heat. Furthermore, in order to achieve both improved dispersibility and reduced thermal degradation, it is also effective to perform melt mixing at a relatively high temperature in the first half of the extruder and to lower the resin temperature in the second half.

[0364] Screw temperature regulation

[0365] The temperature of the screw is also controlled to stabilize extrusion. Examples of temperature control methods include flowing a medium such as water through the interior of the screw and heating the screw by installing a heater inside the screw.

[0366] ·pressure

[0367] The resin pressure in the extruder is generally 1MPa to 50MPa, and is preferably 2MPa to 30MPa, particularly preferably 3MPa to 20MPa, from the viewpoint of extrusion stability and melt uniformity. If the resin pressure in the extruder is more than 1MPa, then since the melt (resin in a molten state) filling rate in the extruder is insufficient, it is possible to suppress the generation of foreign matter caused by the instability of the extrusion pressure and the generation of a stagnant portion. Furthermore, if the resin pressure in the extruder is less than 50MPa, then since it is possible to suppress the excessive shear stress received inside the extruder, it is possible to suppress the thermal decomposition caused by the rise in resin temperature.

[0368] ·Dwell time

[0369] The residence time in the extruder (residence time during film formation) can be calculated from the extruder volume and the polymer discharge capacity, similar to the pelletizing step. The residence time is preferably 10 seconds to 30 minutes, more preferably 15 seconds to 15 minutes, and even more preferably 30 seconds to 10 minutes. A residence time of 10 seconds or longer improves melt plasticization and dispersion of additives.

[0370] A residence time of 30 minutes or less is preferred from the viewpoint of suppressing degradation of the resin and discoloration of the resin.

[0371] (Filter (filter changing device))

[0372] Type, purpose and structure

[0373] To prevent damage to the gear pump caused by foreign matter contained in the raw materials and to extend the life of the fine-pore filter installed downstream of the extruder, a filter is typically installed at the extruder outlet. A so-called breaker plate filter, combining a mesh filter medium with a strong, high-opening-ratio reinforcing plate, is preferred.

[0374] Mesh size and filtration area

[0375] The mesh size is preferably 40 to 800 mesh, more preferably 60 to 700 mesh, and particularly preferably 100 to 600 mesh. If the mesh size is 40 mesh or more, it is possible to fully inhibit foreign matter from passing through the mesh. Furthermore, if it is 800 mesh or less, it is possible to inhibit the increase in the rate of increase in filtration pressure and reduce the frequency of mesh replacement. The filtration area is preferably 0.05 g / cm2 at a flow rate per second. 2 ~5g / cm 2 The standard is selected, and 0.1 g / cm 2 ~3g / cm 2 , especially preferably 0.2 g / cm 2 ~2g / cm 2 .

[0376] (Microfiltration)

[0377] Type, purpose and structure

[0378] In order to filter foreign matter with higher precision, it is preferred to install a precision filter device with high filtration accuracy before extrusion from the mold. The higher the filtration accuracy of the filter material, the better. However, from the perspective of the pressure resistance of the filter material and the suppression of the increase in filtration pressure caused by clogging of the filter material, the filtration accuracy is preferably 3μm to 30μm, more preferably 3μm to 20μm, and particularly preferably 3μm to 10μm. The microporous filtration device is usually installed in one place, but multiple locations can also be installed in series or parallel to perform multi-stage filtration. From the perspective of being able to adopt a large filtration area and high pressure resistance, it is preferred to install a filtration device assembled with a blade-type disc filter.

[0379] The filtration area varies depending on the melt viscosity of the resin being filtered, but is preferably 5 g·cm -2 ·h -1 ~100g·cm -2 ·h-1 , more preferably 10 g·cm -2 ·h -1 ~75g·cm -2 ·h -1 , especially preferably 15 g·cm -2 ·h -1 ~50g·cm -2 ·h -1 .

[0380] From the viewpoint of being usable under high temperature and high pressure, the filter material is preferably a steel material. Among steel materials, stainless steel or steel is more preferably used. From the viewpoint of corrosion, stainless steel is particularly preferably used.

[0381] The thickness of the filter material is preferably 200 μm to 3 mm, more preferably 300 μm to 2 mm, and particularly preferably 400 μm to 1.5 mm.

[0382] The porosity of the filter material is preferably 50% or higher, particularly preferably 70% or higher. A porosity of 50% or higher allows for low pressure loss and minimal clogging, enabling extended operation. The porosity of the filter material is preferably 90% or lower. A porosity of 90% or lower prevents crushing of the filter material when filtration pressure increases, thereby suppressing increases in filtration pressure.

[0383] (Connecting pipes, etc.)

[0384] Like the extruder's barrel and screw, the piping connecting the various parts of the film-forming apparatus (such as adapters, switching valves, and mixing devices) requires excellent corrosion and heat resistance. Suitable materials for these piping include chrome-molybdenum steel, nickel-chrome-molybdenum steel, or stainless steel. Furthermore, to enhance corrosion resistance, the polymer flow path (the inner surface of the piping) is preferably plated with HCr, Ni, or other materials.

[0385] Furthermore, in order to prevent accumulation inside the pipe, the surface roughness inside the pipe is preferably Ra=200 nm or less, more preferably Ra=150 nm or less.

[0386] The pipe diameter is preferably 5 kg·cm -2 ·h -1 ~200Kg·cm -2 ·h -1 , more preferably 10Kg·cm -2 ·h -1 ~150Kg·cm -2 ·h -1 , especially preferably 15Kg·cm -2 ·h -1 ~100Kg·cm -2 ·h -1.

[0387] In order to stabilize the extrusion pressure of liquid crystal polymers with high temperature dependence of melt viscosity, it is preferable to minimize temperature fluctuations in the piping section. Generally speaking, belt heaters with low equipment costs are commonly used when heating the piping, but cast aluminum heaters with small temperature fluctuations or methods based on heat medium circulation are more preferred. In addition, from the perspective of reducing temperature unevenness, the piping is also preferably divided into multiple areas to control each area separately, similar to the barrel. In addition, for temperature control, PID control (Proportional-Integral-Differential Controller) is usually performed, but it is more preferable to combine it with a method of variably controlling the heater output using an AC power regulator.

[0388] Furthermore, installing a mixing device within the flow path of the extruder is also effective for homogenizing the film. A spiral or stator-type static mixer is effective as the mixing device. Since the film is divided and homogenized into 2n by using n-stage static mixers, a larger n promotes homogenization. For homogenization of the film, 5 to 20 stages are preferred, and 7 to 15 stages are more preferred. After homogenization by the static mixer, the film is preferably extruded from the die immediately to form a film.

[0389] (Gear Pump)

[0390] In order to improve the thickness accuracy of the film, it is preferable to reduce the fluctuation of the discharge amount. A gear pump is preferably installed between the extruder and the die.

[0391] Type and size

[0392] Gear pumps are preferably a conventional two-gear type, which uses meshing rotation of two gears to achieve quantitative measurement, or a three-gear type, which uses meshing rotation of three gears to achieve quantitative measurement. The gear pump is typically sized to achieve a capacity that allows a rotational speed of 5 to 50 rpm under extrusion conditions. The rotational speed is preferably 7 to 45 rpm, and particularly preferably 8 to 40 rpm.

[0393] By selecting the size of the gear pump so that the rotation speed falls within the above range, it is possible to suppress a rise in the resin temperature due to shear heat generation, and to suppress degradation of the resin due to stagnation inside the gear pump.

[0394] Furthermore, since gear pumps are constantly subject to wear due to meshing of the gears, materials with excellent wear resistance are required, and preferably, materials with the same wear resistance as those used for the screw and barrel are used.

[0395] · Measures for detention units

[0396] The gear pump requires a gear pump design (especially a clearance) that is tailored to the melt viscosity of the liquid crystal polymer. Furthermore, since the stagnation of the gear pump may cause degradation of the liquid crystal polymer, a structure with as little stagnation as possible is preferred.

[0397] Operating conditions

[0398] If the difference between the primary pressure (input pressure) and the secondary pressure (output pressure) of the gear pump is too large, the load of the gear pump becomes larger, and shear heating becomes larger. Therefore, the pressure difference during operation is preferably within 20MPa (difference between the primary pressure (input pressure) and the secondary pressure (output pressure)), more preferably within 15MPa, and particularly preferably within 10MPa. In addition, in order to homogenize the film thickness and to make the primary pressure of the gear pump constant, it is also effective to control the screw rotation of the extruder or to use a pressure control valve.

[0399] (Mold)

[0400] Type, structure and raw materials

[0401] Foreign matter is removed by filtration, and the molten resin, which is then homogenized by a mixer, is continuously conveyed into the mold. As long as the mold is designed to minimize molten resin retention, any of the commonly used T-type molds, fishtail molds, and coat hanger molds can be used. Of these, T-type molds are preferred because they easily produce liquid crystal polymer films with high tear resistance and excellent film-forming properties.

[0402] The gap at the T-die outlet portion (lip gap) is preferably 1 to 20 times the film thickness, more preferably 1.5 to 15 times, and particularly preferably 2.0 to 10 times.

[0403] When the die lip gap is at least 1 times the film thickness, the increase in the internal pressure of the die can be suppressed, making it easier to control the film thickness, and a sheet with good surface morphology can be obtained during film production. Furthermore, when the die lip gap is 20 times or less the film thickness, the draw ratio can be prevented from becoming excessively large, resulting in improved sheet thickness accuracy.

[0404] The film thickness is generally adjusted by adjusting the gap of the die at the front end of the die. From the viewpoint of thickness accuracy, a flexible die lip is preferably used, but a throttle rod may be used for adjustment depending on the situation.

[0405] The gap adjustment of the die can be changed using the adjustment bolts at the die outlet. The adjustment bolts are preferably arranged at intervals of 15mm to 50mm, more preferably at intervals of less than 35mm, and preferably at intervals of less than 25mm. If the intervals are less than 50mm, the uneven thickness between the adjustment bolts can be suppressed. If the intervals are greater than 15mm, the rigidity of the adjustment bolts becomes sufficient, thereby suppressing the internal pressure fluctuations of the die and suppressing the fluctuations in the film thickness. Furthermore, from the perspective of wall retention, it is preferred that the inner wall surface of the die is smooth, for example, the surface smoothness can be improved by polishing. Depending on the circumstances, after the inner wall surface is plated, the smoothness is improved by polishing or the releasability from the polymer is improved by vapor deposition.

[0406] Furthermore, the flow rate of the polymer flowing out of the die is preferably uniform across the width of the die. Therefore, the manifold shape of the die is preferably modified according to the shear rate dependency of the melt viscosity of the liquid crystal polymer used.

[0407] Furthermore, the temperature of the polymer flowing out of the die is preferably uniform in the width direction. Therefore, it is preferred to homogenize the die by setting the temperature of the die end portion where the die heat generation is large to a higher value, or by suppressing the heat generation of the die end portion.

[0408] Furthermore, the die lip is preferably smooth because insufficient die machining accuracy or foreign matter adhering to the die exit can cause die lines, significantly degrading film quality. The die lip's arithmetic mean surface roughness Ra is preferably 0.05 μm or less, more preferably 0.03 μm or less, and particularly preferably 0.02 μm or less. Furthermore, the radius of curvature R of the die lip edge is preferably 100 μm or less, more preferably 70 μm or less, and particularly preferably 50 μm or less. Furthermore, a die lip processed by thermal spraying ceramics to a sharp edge with a radius of curvature R of 20 μm or less can also be used.

[0409] For reducing thickness fluctuations in long-term continuous production processes, automatic thickness adjustment molds that measure the thickness of the downstream film, calculate the thickness deviation, and feed the results back to the mold for thickness adjustment are also effective.

[0410] The gap between the mold and the point where the polymer roller lands is called the air gap. To stabilize film production by improving thickness accuracy and reducing shrinkage (increasing end thickness by reducing film width), a short air gap is preferred. By setting the angle of the mold tip to an acute angle or reducing the mold thickness, interference between the roller and the mold can be prevented, and the air gap can be shortened. On the other hand, setting the angle of the mold tip to an acute angle or reducing the mold thickness can sometimes reduce mold rigidity, causing the central portion of the mold to open due to resin pressure, which can in turn reduce thickness accuracy. Therefore, it is preferable to select conditions that balance mold rigidity and minimize the air gap.

[0411] Multilayer film

[0412] When manufacturing a film, a single-layer film-making device with low equipment cost can usually be used. Among them, when the functional layer is provided on the outer layer of the liquid crystal polymer film, a multilayer film-making device capable of manufacturing a film having two or more structures can be used. As a method for manufacturing a film using a multilayer film-making device, specifically, a method for multilayering using a multilayer feed block (Feedblock) and a method using a multi-manifold mold can be cited. Generally speaking, it is preferred that the functional layer is thinly laminated on the surface layer, but there is no particular limitation on the lamination ratio.

[0413] The residence time from the pellets entering the extruder from the supply port and flowing out from the supply mechanism (e.g., die) (the residence time from passing through the extruder to being discharged from the die) is preferably 1 to 30 minutes, more preferably 2 to 20 minutes, and particularly preferably 3 to 10 minutes. From the perspective of thermal degradation of the polymer, it is preferred to select equipment with a short residence time. Among them, in order to reduce the volume inside the extruder, for example, if the capacity of the filter is set too small, the filter life is sometimes shortened and the frequency of replacement is increased. In addition, setting the pipe diameter too small sometimes increases pressure loss. For this reason, it is preferred to select equipment of appropriate size.

[0414] Furthermore, by setting the residence time to within 30 minutes, it becomes easy to adjust the maximum circle-equivalent diameter of the bright portion to the above range.

[0415] (casting)

[0416] The film forming step preferably includes a step of supplying a molten liquid crystal polymer from a supply mechanism and a step of causing the molten liquid crystal polymer to land on a casting roll to form a film. The film may be directly wound as a film after being cooled and solidified, or may be formed into a film by continuously passing the film between a pair of pressing surfaces.

[0417] In this case, there is no particular limitation on the mechanism for supplying the molten liquid crystal polymer (melt). For example, the specific mechanism for supplying the melt may be a method using an extruder that extrudes the molten liquid crystal polymer into a film, a method using an extruder and a die, or a method in which the liquid crystal polymer is solidified once into a film, then melted by a heating mechanism to form a melt, and then supplied to the film-forming step.

[0418] When a molten resin extruded into a sheet through a die is clamped by a device having a pair of clamping surfaces, not only can the surface shape of the clamping surfaces be transferred to the film, but also the orientation can be controlled by imparting elongation deformation to the composition containing the liquid crystal polymer.

[0419] Film production methods and types

[0420] In the method of forming a liquid crystal polymer in a molten state into a film, a high clamping pressure can also be applied. From the viewpoint of excellent film surface morphology, it is preferably passed between two rollers (for example, a support roller and a cooling roller). In addition, in the present specification, when there are multiple casting rollers for conveying the melt, the casting roller closest to the most upstream liquid crystal polymer supply mechanism (for example, a mold) is referred to as a cooling roller. In addition, a method of clamping metal belts with each other and a method of combining rollers and metal belts can also be used. Moreover, depending on the circumstances, in order to improve the adhesion between the roller and the metal belt, a film-making method such as an electrostatic application method, an air knife method, an air chamber method and a vacuum nozzle method can also be used in combination on the casting drum.

[0421] Roller types and materials

[0422] From the viewpoint of surface roughness and uniformity of the nip pressure during nip pressing, and from the viewpoint of uniformity of the roll temperature, the casting roll is preferably a metal roll.

[0423] The metal rollers used for rigidity are typically made of carbon steel or stainless steel, but chromium-molybdenum steel, nickel-chromium-molybdenum steel, and, depending on the situation, cast iron can also be used. Furthermore, to modify surface properties such as film release, they are sometimes plated with chromium or nickel, or subjected to ceramic thermal spraying. When using a metal belt, to provide the necessary clamping pressure, the belt thickness is preferably at least 0.5 mm, more preferably at least 1 mm, and even more preferably at least 2 mm.

[0424] The nip length suitable for applying the nip pressure by the pair of rollers is preferably greater than 0 mm and within 5 m, more preferably greater than 0 mm and within 3 mm.

[0425] Roller diameter

[0426] Casting rolls with larger diameters are preferably used, specifically, preferably with a diameter of 200 mm to 1500 mm. Large diameter rolls are preferred because they reduce roll deflection, allowing for uniform, high clamping pressure during the clamping process. Furthermore, in the production method of the present invention, the diameters of the two rolls used for the clamping process may be the same or different.

[0427] Roller hardness

[0428] To achieve the above-mentioned inter-roll pressure, the Shore hardness of the roll is preferably 45 HS or higher, more preferably 50 HS or higher, and particularly preferably 60 HS to 90 HS. The Shore hardness can be determined using the JIS Z 2246 method by taking the average of the values measured at five points in the roll width direction and five points in the roll circumferential direction.

[0429] Surface roughness, cylindricality, roundness and diameter deviation

[0430] The arithmetic mean surface roughness Ra of the surfaces of the casting roll and the support roll is preferably 100 nm or less, more preferably 50 nm or less, and particularly preferably 25 nm or less.

[0431] The roundness is preferably 5 μm or less, more preferably 3 μm or less, and particularly preferably 2 μm or less. The cylindricality is preferably 5 μm or less, more preferably 3 μm or less, and particularly preferably 2 μm or less. The diameter deviation is preferably 7 μm or less, more preferably 4 μm, and particularly preferably 3 μm or less. Cylindricity, roundness, and diameter deviation can be determined using the method of JIS B 0621.

[0432] Roller surface properties

[0433] The surfaces of the casting roll and the support roll are preferably mirror-finished, and rolls obtained by mirror-finishing hard chrome-plated surfaces are usually used.

[0434] From the perspective of the smoothness of the film after film formation, the roller surface is preferably smooth. On the other hand, from the perspective of imparting lubricity to the film, a mirror bag surface roller can be used to form unevenness on the film surface. Alternatively, in order to form fine unevenness on the film surface, a sandblasted roller or a concave roller can be used. Among them, from the perspective of film smoothness, the unevenness of the roller is preferably Ra = 10μm or less. In addition, it is also possible to use a roller surface with a roughness of 1mm per 1mm. 2 A roller with 50 to 1000 fine grooves or prism shapes with a depth of 0.1 to 10 μm engraved in it.

[0435] Roller temperature

[0436] The roller should preferably be able to quickly remove heat from the molten polymer and maintain a constant roller surface temperature. Therefore, a medium of constant temperature is preferably passed through the roller interior. Water, heat transfer oil, or gas is preferably used as the medium. Furthermore, a known method can be used to maintain a constant roller surface temperature.

[0437] Molten polymer temperature

[0438] From the perspective of improving the moldability of the liquid crystal polymer and suppressing degradation, the discharge temperature (resin temperature at the outlet of the supply mechanism) is preferably (Tm of the liquid crystal polymer - 10)°C to (Tm of the liquid crystal polymer + 40)°C. As an indicator of melt viscosity, it is preferably 50 Pa·s to 3500 Pa·s.

[0439] The molten polymer in the air gap is preferably cooled as little as possible, and the temperature drop due to cooling is preferably reduced by taking measures such as increasing the film formation speed and shortening the air gap.

[0440] Roller temperature

[0441] The temperature of the support roller is preferably set below the Tg of the liquid crystal polymer. This prevents the molten polymer from sticking to the roller, improving the film's appearance. For similar reasons, the cooling roller temperature is also preferably set below the Tg of the liquid crystal polymer.

[0442] ·Difference between film forming speed and peripheral speed

[0443] To maintain the melt's heat in the air gap, the film-forming speed is preferably 3 m / min or higher, more preferably 5 m / min or higher, and particularly preferably 7 m / min or higher. Increasing the film-forming speed inhibits cooling of the melt in the air gap and allows for more uniform nip compression and shear deformation while maintaining a high melt temperature. The film-forming speed is defined as the second, slower nip surface speed, which is the velocity of the molten polymer passing between the two nip rollers.

[0444] The movement speed of the first pressing surface is preferably set to be faster than the movement speed of the second pressing surface. Furthermore, the ratio of the movement speeds of the first and second pressing surfaces of the pressing device is preferably adjusted to 0.60 to 0.99, and shear stress is imparted to the molten resin as it passes through the pressing device to produce the film of the present invention. The two pressing surfaces can be driven in conjunction or independently, but independent drive is preferred from the perspective of uniformity of film properties.

[0445] (Film production sequence)

[0446] Film making sequence

[0447] In the film forming process, from the viewpoint of stabilizing the quality, it is preferable to form the film in the following order.

[0448] The molten polymer discharged from the die lands on a casting roll to form a film, and then is cooled and solidified to be wound as a film.

[0449] When the molten polymer is nipped and pressed, the molten polymer passes between a first nip and a second nip surface set at a predetermined temperature, and is cooled and solidified to be wound as a film.

[0450] Conveying tension

[0451] The film conveying tension can be appropriately adjusted by the film thickness. The conveying tension per 1m width of the film is preferably 10N / m to 500N / m, more preferably 20N / m to 300N / m, and particularly preferably 30N / m to 200N / m. Under normal circumstances, if the film becomes thicker, the conveying tension needs to be increased. For example, in the case of a film with a thickness of 100μm, it is preferably 30 to 150N / m, more preferably 40 to 120N / m, and particularly preferably 50 to 100N / m. If the film conveying tension is above the lower limit, the bending of the film during film conveyance can be suppressed, thereby suppressing the slippage between the guide roller and the film and causing scratches on the film. If the film conveying tension is below the upper limit, the introduction of vertical wrinkles into the film can be suppressed, and the film can be suppressed from being forcibly stretched and broken.

[0452] Film tension control can be achieved using any of a reciprocating oscillation method, a servo motor torque control method, a powder clutch / brake method, and a friction roller control method. However, from the perspective of control accuracy, a reciprocating oscillation method is preferred. The transport tension does not need to be set to the same value throughout the film forming process; it is also useful to adjust it to an appropriate value for each tension cut area.

[0453] The conveying roller preferably has a smooth surface that does not cause roller deflection caused by conveying tension, has low mechanical loss, has sufficient friction with the film, and is not prone to scratches during the film conveying process. If a conveying roller with low mechanical loss is used, high tension is not required to convey the film, and scratches introduced into the film can be suppressed. In addition, to reduce friction with the film, the conveying roller preferably has a large wrap angle of the film. The wrap angle is preferably 90° or more, more preferably 100° or more, and particularly preferably 120° or more. If a sufficient wrap angle cannot be selected, it is preferable to use a rubber roller, or a roller with texture, grooves, or grooves on the roller surface to ensure friction.

[0454] Winding tension

[0455] Similar to the film transport tension, the winding tension is preferably adjusted appropriately according to the film thickness. The winding tension per 1m of film width is preferably 10N / m to 500N / m, more preferably 20N / m to 300N / m, and particularly preferably 30N / m to 200N / m. Generally, as the film becomes thicker, the tension needs to be increased. For example, in the case of a 100μm film, the winding tension is preferably 30N / m to 150N / m, more preferably 40N / m to 120N / m, and particularly preferably 50N / m to 100N / m.

[0456] If the winding tension is above the lower limit, the bending of the film during film transport can be suppressed, thereby preventing the film from slipping and scratching during winding. If the winding tension is below the upper limit, vertical wrinkles can be suppressed in the film, and the film can be tightly wound, thereby improving the appearance of the winding. Moreover, since the uneven parts of the film can be suppressed from extending due to creep, the film can be suppressed from fluctuating. The winding tension is preferably detected by tension control midway through the line, similar to the transport tension, and is controlled to a constant winding tension while winding. Depending on the position of the film production line, when the film temperature varies, the length of the film sometimes varies slightly due to thermal expansion. Therefore, it is preferred to adjust the extension ratio between the nip rollers (niproll) so that no tension exceeding the specified value is applied to the film midway through the line. In addition, the winding tension can also be wound at a constant tension through tension control, but it is more preferred to add a taper (in the winding operation, the winding tension changes as the winding diameter increases) according to the diameter of the winding to achieve an appropriate winding tension. Generally speaking, the tension is gradually reduced as the winding diameter increases, but it is sometimes preferable to increase the tension as the winding diameter increases depending on the situation. In addition, regarding the winding direction, there is no problem even if either the first clamping surface or the second clamping surface is set to the winding core side. However, if curl occurs on the film, winding in the opposite direction of the curl may have a curl correction effect, which is preferable.

[0457] To control film meandering during winding, it is also useful to provide EPC (Edge Position Control), perform oscillation winding to prevent the generation of winding irregularities, or use rollers that remove accompanying air during high-speed winding.

[0458] Winding core

[0459] The winding core used for winding the film does not need to be a special winding core as long as it has the strength and rigidity required for winding the film. Generally, a paper tube with an inner diameter of 3 to 6 inches or a plastic winding core with an inner diameter of 3 to 14 inches is used.

[0460] Slit

[0461] In order to obtain a film having a predetermined width, the film is preferably cut at both ends. Common methods such as shear blades, Goebel knives, razor blades, and rotary blades can be used for the cutting process. A cutting method that generates no dust and minimizes burrs on the cut portion is preferably used, and cutting with a Goebel blade is preferred.

[0462] Knurling

[0463] It is also preferred to perform thickening processing (knurling) on one or both ends of the film.

[0464] The height of the concavo-convex based on the thickening process is preferably 1 μm to 50 μm, more preferably 2 μm to 30 μm, and particularly preferably 3 μm to 20 μm. During the thickening process, both sides can be set to convex, or only one side can be set to convex. The width of the thickening process is preferably 1 mm to 50 mm, and particularly preferably 3 mm to 30 mm. The thickening process can use either cold working or hot working, as long as an appropriate method is selected according to the droop of the concavo-convex formed in the film or the state of dust during the thickening process. In addition, it is also useful to be able to identify the film forming direction or film surface of the film by knurling.

[0465] Masking film

[0466] In order to prevent the film from being scratched or to improve the handleability, it is also preferable to provide a laminate film (masking film) on one or both sides. The thickness of the laminate film is preferably 5 μm to 100 μm, more preferably 10 μm to 70 μm, and particularly preferably 25 μm to 50 μm.

[0467] The masking film preferably consists of two layers: a base layer and an adhesive layer. The base layer can be made of LDPE (low-density polyethylene), LLDPE (linear low-density polyethylene), HDPE (high-density polyethylene), PP (polypropylene), or polyester. The adhesive layer can be made of EVA (ethylene vinyl acetate), acrylic rubber, styrene-based elastomer, or natural rubber.

[0468] Eliminate static electricity

[0469] When the film is charged, dust in the atmosphere is attracted to the film and becomes foreign matter adhering to the film. Therefore, it is preferable that the film is not charged during film formation, transportation, and winding.

[0470] The charging voltage is preferably 3 kV or less, more preferably 0.5 kV, and particularly preferably 0.05 kV or less.

[0471] Methods for preventing static electricity in the film include kneading or coating the film with an antistatic agent, controlling the temperature and humidity of the atmosphere, dissipating static electricity on the film by connecting it to the ground, and neutralizing the static electricity with an ionizer using a charge of the opposite sign to the static electricity. Furthermore, to enhance the effectiveness of preventing dust from adhering to the film due to static electricity elimination, the film-forming environment is preferably at or below Class 10,000, more preferably at or below Class 1000, and particularly preferably at or below Class 100, as defined in U.S. Federal Standards, Fed. Std. 209D.

[0472] Dust removal

[0473] Foreign matter attached to the surface of the membrane can be removed using the following methods: a method of pressing with a scraper or brush, a method of spraying pressurized air that has been neutralized with a pressure of about tens of KPa to reduce the attraction effect caused by static electricity, a method based on suction, and a method combining spraying and suction.

[0474] (Stretching and relaxing treatment)

[0475] After the film is produced by the above method, it may be subjected to stretching and relaxation. For example, the following steps (a) to (g) may be combined to perform the respective steps. Furthermore, the order of longitudinal stretching and transverse stretching may be reversed, longitudinal stretching and transverse stretching may be performed in multiple stages, diagonal stretching may be performed, or simultaneous biaxial stretching may be performed.

[0476] (a) Transverse stretching

[0477] (b) Horizontal stretching → relaxation

[0478] (c) Longitudinal stretching

[0479] (d) Longitudinal stretching → relaxation

[0480] (e) Longitudinal (transverse) stretching → transverse (longitudinal) stretching

[0481] (f) Longitudinal (transverse) stretching → transverse (longitudinal) stretching → relaxation

[0482] (g) Transverse stretching → Relaxation → Longitudinal stretching → Relaxation

[0483] Longitudinal stretch

[0484] Longitudinal stretching can be achieved by heating the space between two pairs of rollers while making the circumferential speed of the outlet side faster than the circumferential speed of the inlet side. From the viewpoint of suppressing the film from curling, the film temperature on the front and back sides is preferably the same temperature, but when the optical properties are controlled in the thickness direction, stretching can be performed even if the temperature of the front and back sides is different. In addition, the stretching temperature is defined as the temperature on the lower side of the film surface. The longitudinal stretching process can be implemented in one stage or in multiple stages. The preheating of the film is usually carried out by passing a temperature-controlled heating roller, but a heater can also be used to heat the film depending on the situation. In addition, in order to prevent the film from sticking to the roller, a ceramic roller with improved adhesion can also be used.

[0485] ·Horizontal stretch

[0486] As the transverse stretching, conventional transverse stretching can be adopted. That is, conventional transverse stretching refers to a transverse stretching method in which the ends of the film are gripped with clips and the width of the clips is expanded while heating in an oven using a tenter. For example, the methods described in Japanese Utility Model Publication No. 62-035817, Japanese Patent Publication No. 2001-138394, Japanese Patent Publication No. 10-249934, Japanese Utility Model Publication No. 6-270246, Japanese Utility Model Publication No. 4-30922, and Japanese Patent Publication No. 62-152721 can be used.

[0487] The stretching temperature in the transverse stretching can be controlled by feeding air of the desired temperature into the tenter. For the same reason as in the longitudinal stretching process, the film temperature may be the same on the front and back sides or different on the front and back sides. The stretching temperature used here is defined as the temperature on the lower side of the film surface. The transverse stretching process may be implemented in one stage or in multiple stages. Furthermore, when transverse stretching is performed in multiple stages, it may be performed continuously or intermittently with an area where the width is not expanded being provided between them. In addition to the conventional transverse stretching in which the width is expanded in the width direction by clamps in the tenter, this transverse stretching method can also be applied in the same manner as these, in which the width is expanded by clamps.

[0488] Oblique stretching

[0489] As with conventional transverse stretching, the clips expand the width in the transverse direction, but by varying the conveying speed of the left and right clips, stretching in an oblique direction is possible. For example, the methods described in Japanese Patent Application Laid-Open Nos. 2002-22944, 2002-086554, 2004-325561, 2008-23775, and 2008-110573 can be used.

[0490] Simultaneous biaxial stretching

[0491] Simultaneous biaxial stretching is similar to conventional transverse stretching, in which the clip is expanded in width in the transverse direction, but is simultaneously stretched or contracted in the longitudinal direction. For example, the methods described in Japanese Utility Model Publication No. 55-093520, Japanese Patent Publication No. 63-247021, Japanese Patent Publication No. 6-210726, Japanese Patent Publication No. 6-278204, Japanese Patent Publication No. 2000-334832, Japanese Patent Publication No. 2004-106434, Japanese Patent Publication No. 2004-195712, Japanese Patent Publication No. 2006-142595, Japanese Patent Publication No. 2007-210306, Japanese Patent Publication No. 2005-022087, Japanese Patent Publication No. 2006-517608, and Japanese Patent Publication No. 2007-210306 can be used.

[0492] Improvement of bending (axis misalignment)

[0493] During the transverse stretching process, the ends of the film are held by clips. Consequently, the deformation of the film caused by the thermal shrinkage stress generated during the heat treatment increases in size at the center of the film and decreases at the ends. As a result, the resulting film can be distributed with characteristics in the width direction. Before the heat treatment process, when a straight line is drawn laterally on the surface of the film, the straight line on the surface of the film after the heat treatment process becomes bowed with the center portion concave toward the downstream. This phenomenon is known as bowing phenomenon, which interferes with the anisotropy and uniformity of the film in the width direction.

[0494] As an improvement, the deviation in the orientation angle associated with bending can be reduced by preheating before transverse stretching and heat setting after stretching. Either preheating or heat setting can be performed, but both are more preferred. These preheating and heat setting are preferably performed by clamping, that is, they are preferably performed continuously with stretching.

[0495] Preheating is preferably performed at a temperature about 1 to 50° C. higher than the stretching temperature, more preferably 2 to 40° C. higher, and particularly preferably 3 to 30° C. higher. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and particularly preferably 10 seconds to 2 minutes.

[0496] During preheating, the width of the tenter is preferably kept substantially constant, where "substantially" means ±10% of the width of the unstretched film.

[0497] Heat setting is preferably performed at a temperature 1 to 50° C. lower than the stretching temperature, more preferably 2 to 40° C. lower, and even more preferably 3 to 30° C. lower. It is particularly preferably below the stretching temperature and below the Tg of the liquid crystal polymer.

[0498] The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and particularly preferably 10 seconds to 2 minutes. During heat fixing, the width of the tenter is preferably kept roughly constant. Wherein, "roughly" means 0% (the same width as the width of the tenter after stretching) to -30% (30% reduction in width than the width of the tenter after stretching = reduced width) of the tenter after stretching. When the width is expanded to more than the stretched width, it becomes easy to produce residual strain in the film. As other well-known methods, the methods described in Japanese Patent Application Publication No. 1-165423, Japanese Patent Application Publication No. 3-216326, Japanese Patent Application Publication No. 2002-018948 and Japanese Patent Application Publication No. 2002-137286 can be cited.

[0499] Thermal relaxation treatment

[0500] After the stretching, thermal shrinkage can be reduced by performing a heat relaxation treatment under the following conditions. The heat relaxation treatment is preferably performed at at least one of the following points: after film formation, after longitudinal stretching, and after transverse stretching. The heat relaxation treatment can be performed continuously after stretching or after winding after stretching.

[0501] (Surface Treatment)

[0502] The film can be subjected to surface treatment to improve the adhesion between the copper foil or copper plating layer used in the copper clad laminate. For example, glow discharge treatment, ultraviolet irradiation treatment, corona treatment, flame treatment and acid or alkali treatment can be used. The glow discharge treatment mentioned here can be -3 Low-temperature plasma generated under a low-pressure gas of Torr to 20 Torr is preferably used as a plasma treatment under atmospheric pressure.

[0503] (aging)

[0504] In order to improve the mechanical properties, thermal dimensional stability, and winding posture of the wound film, it is also useful to subject the film to an aging treatment at a temperature below the Tg of the liquid crystal polymer.

[0505] (Storage Conditions)

[0506] In order to prevent wrinkles or unevenness caused by residual strain relaxation in the wound film, it is preferable to store the film in an environment with a temperature below the Tg of the liquid crystal polymer. In addition, the temperature fluctuation is preferably small, and the temperature fluctuation per hour is preferably 30°C or less, more preferably 20°C or less, and particularly preferably 10°C or less. Similarly, in order to prevent changes in the moisture absorption rate of the film and condensation, the humidity is preferably 10% to 90%, more preferably 20% to 80%, and particularly preferably 30% to 70%. In order to prevent changes in the moisture absorption rate of the film and condensation, the temperature fluctuation per hour is preferably 30% or less, more preferably 20% or less, and particularly preferably 10% or less. When storing in a location where temperature and humidity changes are required, it is also effective to use a packaging material with moisture-proof or heat-insulating properties.

[0507] In the above description, the film is a single layer, but may have a laminated structure in which a plurality of layers are laminated.

[0508] The method for producing a liquid crystal polymer film according to the present invention may include at least one of a specific heat treatment and an annealing treatment.

[0509] (Specific heat treatment)

[0510] In the method for producing a liquid crystal polymer film of the present invention, it is preferred to perform a heat treatment step of reheating the molten resin extruded into a sheet using a heater before solidification, followed by immediately cooling the molten resin extruded into a sheet using a cooler. Hereinafter, the series of heat treatments including reheating and cooling performed before solidification of the molten resin extruded into a sheet will also be referred to as "specific heat treatment."

[0511] It is considered that by performing a specific heat treatment before solidifying the molten resin extruded into a sheet, the void area ratio in the thickness direction of the molten resin extruded into a sheet changes.

[0512] Although the detailed mechanism of the change in the void area ratio in the thickness direction is not yet clear, the present inventors speculate that it is based on the following: the film surface is heated by reheating treatment, and the film surface is immediately cooled after heating so that the film forming properties are not hindered, and the crystal structure of the surface layer of the film changes through melting and rapid cooling.

[0513] The conditions of the specific heat treatment can be appropriately adjusted according to the material constituting the liquid crystal polymer film, the target void area ratio, and the like.

[0514] From the perspective of achieving a clearer hardness distribution in the thickness direction, when the melting point of the liquid crystal polymer is Tm (°C), the reheating temperature is preferably {Tm-10}°C or higher, and more preferably a temperature exceeding Tm. Furthermore, from the perspective of suppressing thickness unevenness caused by film softening, the reheating temperature is preferably {Tm+20}°C or lower, and more preferably {Tm+15}°C or lower.

[0515] The reheating treatment time varies depending on the heating mechanism and heating temperature, but is preferably 0.2 to 15 seconds, more preferably 1 to 5 seconds.

[0516] Examples of heating mechanisms (heaters) used for reheating include well-known heating mechanisms such as hot air dryers and infrared heaters. Infrared heaters are preferred because they can quickly raise the film surface temperature. The heating mechanisms are preferably evenly distributed along the TD direction of the extruded sheet-shaped molten resin. This arrangement of heating mechanisms can suppress temperature differences in the TD direction of the extruded sheet-shaped molten resin during reheating.

[0517] Regarding the cooling process during the specific heat treatment, it is preferably performed quickly after reheating to prevent the formation of structures and uneven thickness in the film surface. The cooling process is preferably performed at a rate such that the surface temperature of the molten resin extruded into a sheet reaches -10°C / second or higher (more preferably -20°C / second or higher, and even more preferably -30°C / second or higher). The upper limit is not particularly limited, but is, for example, -80°C / second or lower.

[0518] From the same viewpoint as above, the cooling treatment is preferably carried out until the surface temperature of the molten resin extruded into a sheet is lower than the crystallization temperature. The crystallization temperature can be measured as the recrystallization peak temperature when the molten resin extruded into a sheet is heated to a temperature above the melting point using a differential scanning calorimeter (DSC) and then cooled at 10°C / min.

[0519] The specific cooling treatment time varies depending on the cooling mechanism and the temperature of the film surface heated by reheating, but is preferably 0.3 to 15 seconds, more preferably 2 to 10 seconds.

[0520] As the cooling mechanism (cooler) used for the cooling process, known cooling devices can be used, but a blower that blows air (preferably cold air) toward the molten resin extruded into a sheet is preferably used. The cooling mechanism is preferably evenly arranged around the circumference of the molten resin extruded into a sheet. This arrangement of the heating mechanism can suppress temperature differences in the TD direction of the molten resin extruded into a sheet during cooling.

[0521] (Annealing treatment)

[0522] In the production method of the present invention, it is preferred that an annealing treatment be performed after the specific heat treatment until the liquid crystal polymer film is heated to a temperature close to the melting temperature. The annealing treatment is preferably performed after the specific heat treatment.

[0523] Although the reason is unclear, performing an annealing treatment after a cooling treatment (preferably after a further relaxation treatment) during a specific heat treatment promotes crystallization in the surface region, resulting in a reduction in the void region within the liquid crystal polymer film. This significantly reduces the width of the void region in the thickness direction, and the proportion of the domain region increases relatively. By performing a cooling treatment and an annealing treatment during a specific heat treatment and adjusting these conditions as needed, a liquid crystal polymer film having these specific void characteristics can be produced.

[0524] The melting point of the liquid crystal polymer is defined as Tm (°C). The heating temperature during the annealing treatment is preferably between {Tm-50}°C and {Tm+30}°C, preferably exceeding {Tm+10}°C and not exceeding {Tm+25}°C. The heating time during the annealing treatment is preferably between 10 seconds and 24 hours, more preferably between 4 and 12 hours. In particular, when the heating temperature is below Tm, the heating time is more preferably between 4 and 12 hours, and even more preferably between 8 and 12 hours, from the perspective of facilitating the production of a liquid crystal polymer film having the aforementioned specific void characteristics.

[0525] Examples of the heating mechanism in the annealing treatment include a hot air drying furnace, a hot press (for example, a surface press or a heating roll), and the like, with a hot press being preferred.

[0526] Annealing can be performed on a composite body made by laminating a liquid crystal polymer film on an adherend (e.g., a metal foil such as copper foil or aluminum foil). The use of an adherend can suppress deformation of the liquid crystal polymer film during heating. When the composite body is annealed, the adherend is peeled off from the annealed composite body to obtain the liquid crystal polymer film.

[0527] After the annealing treatment, a thermal relaxation treatment may be further performed. The thermal relaxation step in this case is performed based on the thermal relaxation step performed before the annealing treatment.

[0528] [Applications of Liquid Crystal Polymer Films]

[0529] The liquid crystal polymer film of the present invention can be used as a single film, a copper-clad laminate laminated with copper foil, a printed wiring board, a flexible printed wiring board (FPC), and the like, and can be used as a material included in a communication substrate. That is, the communication substrate of the present invention comprises the liquid crystal polymer film of the present invention.

[0530] The liquid crystal polymer film of the present invention is preferably used in flexible printed circuit boards. Since the liquid crystal polymer film of the present invention has a low relative dielectric constant and dielectric loss tangent, it can suppress transmission loss in high-frequency bands, making it useful. Furthermore, the liquid crystal polymer film of the present invention can suppress cohesion and delamination caused by processing, making it suitable for the manufacture of flexible printed circuit boards.

[0531] <Laminate>

[0532] The laminated body of the present invention comprises the above-mentioned liquid crystal polymer film and at least one metal-containing layer.

[0533] Hereinafter, the structure of the laminated body according to the present invention will be described in detail.

[0534] The laminate has at least one metal-containing layer and at least one liquid crystal polymer film. The number of metal-containing layers and liquid crystal polymer films in the laminate is not limited, and the number of each layer may be only one or may be two or more.

[0535] The laminate may be a single-sided laminate having only one metal-containing layer on one side of a liquid crystal polymer film, or a double-sided laminate having two metal-containing layers on both sides of a liquid crystal polymer film.

[0536] Among them, the laminate preferably has a layer structure in which at least a metal-containing layer, a liquid crystal polymer film, and a metal-containing layer are laminated in this order.

[0537] Furthermore, the laminate may have a multilayer structure in which three or more metal-containing layers and two or more liquid crystal polymer films are stacked in different layers. In other words, the laminate may have a multilayer structure in which three or more metal layers or metal wirings are arranged via an insulating layer containing a liquid crystal polymer film.

[0538] A laminate having such a multilayer structure can be suitably used for a multilayer circuit board with high functionality (for example, a two-layer circuit board, a three-layer circuit board, a four-layer circuit board, etc.).

[0539] The laminate may be a single-layer circuit substrate comprising two metal layers or metal wirings and an insulating layer comprising a liquid crystal polymer film. Furthermore, the laminate may be an intermediate for producing a laminate having the above-described multilayer structure, comprising one or two metal layers or metal wirings and an insulating layer comprising a liquid crystal polymer film.

[0540] (including metal layer)

[0541] The metal-containing layer is not particularly limited as long as it is formed on the surface of the liquid crystal polymer film and contains metal. Examples thereof include a metal layer covering the entire surface of the liquid crystal polymer film and metal wiring formed on the surface of the liquid crystal polymer film.

[0542] Examples of materials constituting the metal-containing layer include metals used for electrical connection. Examples of such metals include copper, gold, silver, nickel, aluminum, and alloys containing any of these metals. Examples of alloys include copper-zinc alloys, copper-nickel alloys, and zinc-nickel alloys.

[0543] As a material constituting the metal-containing layer, copper is preferably used from the viewpoint of excellent electrical conductivity and processability.

[0544] The metal-containing layer is preferably a copper layer or copper wiring composed of copper or a copper alloy containing 95% by mass or more of copper. Examples of the copper layer include rolled copper foil produced by a rolling method and electrolytic copper foil produced by an electrolytic method. The metal-containing layer may be subjected to a chemical treatment such as acid cleaning.

[0545] As will be described later, the metal-containing layer is produced using, for example, a metal foil, and a wiring pattern is formed by a known processing method as needed.

[0546] When a metal foil such as copper foil is used to produce a laminate, the surface roughness (arithmetic mean height) Ra of the metal foil surface (at least one surface) is preferably 2.0 μm or less, more preferably 1.0 μm or less, and even more preferably 0.5 μm or less, from the perspective of reducing transmission loss when used as a flexible circuit board. The lower limit is not particularly limited, but is, for example, 0.1 μm or more, preferably 0.3 μm or more.

[0547] Examples of metal foils having a surface roughness Ra within the above range include non-roughened copper foils, which are commercially available.

[0548] The surface roughness Ra of the metal foil and the metal-containing layer is determined using a surface roughness measuring instrument (for example, URFTESTSJ-201 manufactured by Mitutoyo Corporation) according to JIS B 0601. The specific measurement method is described in the Examples below.

[0549] The thickness of the metal-containing layer is not particularly limited and can be appropriately selected depending on the application of the circuit board. From the viewpoint of wiring conductivity and economic efficiency, it is preferably 1 to 100 μm, more preferably 5 to 30 μm, and even more preferably 10 to 20 μm.

[0550] The laminate may include a liquid crystal polymer film and other layers other than the metal-containing layer as needed. Examples of the other layers include an adhesive layer, a rust-proof layer, and a heat-resistant layer.

[0551] (Adhesive layer)

[0552] From the viewpoint of achieving more excellent peel strength, the laminate preferably includes an adhesive layer.

[0553] When the laminate has an adhesive layer, the adhesive layer is preferably disposed between the liquid crystal polymer film and the metal-containing layer. For example, when two metal-containing layers are disposed on both sides of the liquid crystal polymer film, the metal-containing layer, the adhesive layer, the liquid crystal polymer film, the adhesive layer, and the metal-containing layer are preferably laminated in this order.

[0554] 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 comprising a cured product of an adhesive composition containing a known binder resin and at least one of the reactive compounds described below can be used.

[0555] The adhesive composition used for forming the adhesive layer is not particularly limited, and examples thereof include a composition containing a binder resin and / or a reactive compound, and further containing the additives described below as optional components.

[0556] (Binder resin)

[0557] Examples of the binder resin include (meth) acrylic resins, polyvinyl cinnamate, polycarbonate, polyimide, polyamide-imide, polyesterimide, polyetherimide, polyetherketone, polyetheretherketone, polyethersulfone, polysulfone, parylene, polyester, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, polyurethane, polyvinyl alcohol, cellulose acylate, fluorinated resins, liquid crystal polymers, syndiotactic polystyrene, silicone resins, epoxy silicone resins, phenolic resins, alkyd resins, epoxy resins, maleic acid resins, melamine resins, urea-formaldehyde resins, aromatic sulfonamides, benzoguanamine resins, silicone elastomers, aliphatic polyolefins (e.g., polyethylene and polypropylene), and cyclic olefin copolymers. Among these, polyimide, liquid crystal polymer, polyimide, syndiotactic polystyrene, or cyclic olefin copolymers are preferred, and polyimide is more preferred.

[0558] The binder resin may be used alone or in combination of two or more.

[0559] The content of the binder resin is preferably 60 to 99.9% by mass, more preferably 70 to 99.0% by mass, and even more preferably 80 to 97.0% by mass, relative to the total mass of the adhesive layer.

[0560] (Reactive Compound)

[0561] The adhesive layer may contain a reactant of a compound having a reactive group, and preferably further contains a reactive compound in addition to the above-mentioned binder resin. In this specification, the compound having a reactive group and its reactant are also collectively referred to as "reactive compound".

[0562] The reactive group of the reactive compound is preferably a group that can react with a group that may be present on the surface of the liquid crystal polymer film (particularly, a group having an oxygen atom such as a carboxyl group or a hydroxyl group).

[0563] As the reactive group, for example, an epoxy group, an oxetane group, an isocyanate group, an acid anhydride group, a carbodiimide group, an N-hydroxy ester group, a glyoxal group, an ester imide group, a halogenated alkyl group and a thiol group can be mentioned. Preferably, at least one group selected from the group consisting of an epoxy group, an acid anhydride group and a carbodiimide group is used, and more preferably, an epoxy group is used.

[0564] Specific examples of the reactive compound having an epoxy group include aromatic glycidylamine compounds (e.g., 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-tert-butylphenyl glycidyl ether), aliphatic glycidylamine compounds (e.g., 1,3-bis(diglycidylaminomethyl)cyclohexane, etc.), and aliphatic glycidyl ether compounds (e.g., sorbitol polyglycidyl ether).

[0565] Specific examples of the reactive compound having an acid anhydride group include tetracarboxylic dianhydrides (e.g., 3,3',4,4'-benzophenonetetracarboxylic 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'-benzophenonetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl) dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic 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-hexafluoroisopropyl)diphthalic dianhydride).

[0566] Specific examples of the reactive compound having a carbodiimide group include monocarbodiimide compounds (for example, dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, tert-butylisopropylcarbodiimide, diphenylcarbodiimide, di-tert-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, pp. 2069-2075 (1963) and Chemical Review 1981, Vol. 81, No. 4, pp. 619-621).

[0567] Examples of commercially available reactive compounds having a carbodiimide group include Carbodilite (registered trademark) HMV-8CA, LA-1, and V-03 (all manufactured by Nisshinbo Chemical Inc.), stavaxol (registered trademark) P, P100, and P400 (all manufactured by Lanxess AG), and Stabilizer 9000 (product name, manufactured by Raschig Chemie).

[0568] The number of reactive groups possessed by the reactive compound is more than 1, and from the viewpoint that the adhesion of the liquid crystal polymer film to the metal-containing layer is more excellent, preferably more than 2. That is, the reactive compound is preferably a cross-linking agent with more than 2 reactive groups. The number of reactive groups possessed by the cross-linking agent is more preferably more than 3. The upper limit of the number of reactive groups possessed by the reactive compound or the cross-linking agent is not particularly limited, for example, less than 6, preferably less than 5. As the reactive group possessed by the cross-linking agent, the above-mentioned preferred reactive groups can be enumerated.

[0569] 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 of a reactive group of the compound having a reactive group and a group containing an oxygen atom present on the surface of the liquid crystal polymer film can be mentioned.

[0570] The reactive compound may be used alone or in combination of two or more.

[0571] The content of the reactive compound is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and even more preferably 3 to 20% by mass, relative to the total mass of the adhesive layer.

[0572] The adhesive layer may further contain a binder resin and components other than the reactive compound (hereinafter also referred to as “additives”).

[0573] Examples of the additives include inorganic fillers, curing catalysts, and flame retardants.

[0574] The content of the additive is preferably 0.1 to 40% by mass, more preferably 1 to 30% by mass, and even more preferably 3 to 20% by mass, relative to the total mass of the adhesive layer.

[0575] (thickness)

[0576] When the laminate has an adhesive layer, the thickness of the adhesive layer is preferably 0.05 μm or greater, more preferably 0.1 μm or greater, and even more preferably 0.2 μm or greater, from the perspective of achieving superior peel strength of the metal-containing layer. The upper limit is not particularly limited, but is preferably 1 μm or less, more preferably 0.8 μm or less, and even more preferably 0.6 μm or less.

[0577] Furthermore, from the viewpoint of further improving the peel strength of the metal-containing layer, the ratio of the thickness of the adhesive layer to the thickness of the liquid crystal polymer film is preferably 0.1 to 2%, and more preferably 0.2 to 1.6%.

[0578] The thickness of the adhesive layer is equivalent to the thickness of one adhesive layer.

[0579] The thickness of the adhesive layer can be measured according to the above-mentioned method for measuring the thickness of the liquid crystal polymer film.

[0580] <Method for Manufacturing Laminated Body>

[0581] There is no particular limitation on the method for manufacturing the laminate. For example, a method including the following steps can be cited, which is a step of manufacturing the laminate by laminating the liquid crystal polymer film and metal foil of the present invention and then pressing the liquid crystal polymer film and the metal foil together under high temperature conditions (hereinafter also referred to as "step B").

[0582] (Process B)

[0583] In step B, the liquid crystal polymer film of the present invention and a metal foil containing a metal constituting the metal-containing layer are laminated and pressure-bonded to the metal foil under high temperature conditions to produce a laminate having the liquid crystal polymer film and the metal-containing layer.

[0584] The liquid crystal polymer film and metal foil used in step B are as described above. The method and conditions for thermocompression bonding the liquid crystal polymer film and metal foil in step B are not particularly limited and can be appropriately selected from known methods and conditions.

[0585] The thermocompression bonding in step B can be performed using a known mechanism such as a heating roller. Examples of the heating roller include a metal roller and a heat-resistant rubber roller.

[0586] The temperature conditions for thermocompression bonding are preferably {Tm-80} to {Tm+30}° C., more preferably {Tm-40} to Tm° C. The pressure conditions for thermocompression bonding are preferably 0.1 to 20 MPa. The processing time for compression bonding is preferably 0.001 to 1.5 hours.

[0587] The metal-containing layer of the laminate can be a patterned metal wiring. The method for producing the metal wiring is not particularly limited. For example, a method can be used in which, after performing step B of laminating a liquid crystal polymer film and a metal foil by thermocompression bonding, the resulting metal layer is subjected to etching, etc., thereby forming the metal wiring. Furthermore, patterned metal wiring can be formed directly on the surface of the liquid crystal polymer film by known methods such as sputtering, ion plating, and vapor phase methods such as vacuum evaporation, as well as wet plating.

[0588] <Adhesive Layer Formation Step>

[0589] In the case of manufacturing a laminate having a liquid crystal polymer film, an adhesive layer and a metal-containing layer in sequence, a process of forming an adhesive layer in at least one of the liquid crystal polymer films using an adhesive composition is performed, and then step B is performed using the obtained liquid crystal polymer film with an adhesive layer and a metal foil to obtain a laminate having the above-mentioned adhesive layer.

[0590] The adhesive layer forming step includes, for example, coating an adhesive composition on at least one surface of a liquid crystal polymer film and, if necessary, drying and / or curing the coated film to form an adhesive layer on the liquid crystal polymer film.

[0591] The adhesive composition includes, for example, a composition comprising the above-mentioned binder resin, reactive compounds, additives and other components constituting the adhesive layer, and a solvent. Components constituting the adhesive layer are as described above, and therefore, description thereof is omitted.

[0592] 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).

[0593] The solvent may be used alone or in combination of two or more.

[0594] The content of the solvent is, for example, preferably 0.0005 to 0.02 mass %, more preferably 0.001 to 0.01 mass %, relative to the total mass of the adhesive composition.

[0595] 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.

[0596] In this specification, the "solid content" of the composition refers to the components excluding the solvent (organic solvent) and water. In other words, the solid content of the adhesive composition refers to the components constituting the adhesive layer, such as the binder resin, reactive compound, and additives.

[0597] The method for attaching the adhesive composition to the liquid crystal polymer film is not particularly limited, and examples thereof include bar coating, spray coating, knife coating, flow coating, spin coating, dip coating, die coating, inkjet coating, and curtain coating.

[0598] When the adhesive composition attached to the liquid crystal polymer film is dried, the drying conditions are not particularly limited. However, the drying temperature is preferably 25 to 200° C., and the drying time is preferably 1 second to 120 minutes.

[0599] In the method for manufacturing a laminate, the laminate of the present invention can be produced by performing the above-mentioned step B of laminating a liquid crystal polymer film and a metal-containing layer (adhesive layer) and thermally pressing the liquid crystal polymer film and the metal foil after performing the step of forming an adhesive layer using an adhesive composition.

[0600] In addition, the method of producing the laminated body of the present invention having the liquid crystal polymer film and the metal-containing layer is not limited to the above-mentioned method.

[0601] For example, it is possible to form an adhesive layer by coating the adhesive composition on at least one surface of a metal foil, drying and / or curing the coated film as needed, and then stacking the metal foil with the adhesive layer and the liquid crystal polymer film in such a way that the adhesive layer is in contact with the liquid crystal polymer film. Subsequently, the metal foil, the adhesive layer and the liquid crystal polymer film are heat-pressed according to the method described in step B to produce a laminate having a liquid crystal polymer film, an adhesive layer and a metal-containing layer stacked in sequence.

[0602] Furthermore, a laminate can be produced by forming a metal-containing layer on the surface of a liquid crystal polymer film by a known method such as vapor deposition, electroless plating, or electrolytic plating.

[0603] The laminated body produced by the above-mentioned production method can be used for production of the above-mentioned multilayer circuit board.

[0604] For example, a circuit substrate with a multilayer structure can be manufactured as follows: a metal layer of a stack (first stack) manufactured by the above-mentioned manufacturing method is subjected to a patterning process as needed to form metal wiring, and then the first stack having metal wiring and the second stack formed by laminating a metal layer to one surface of an insulating layer including a liquid crystal polymer film are stacked in such a manner that the surface on the metal wiring side of the first stack is in contact with the surface on the insulating layer side of the second stack, and the obtained stack is hot-pressed according to the above-mentioned step B.

[0605] <Flexible Copper Clad Laminate>

[0606] An example of the laminate of the present invention is a flexible copper-clad laminate.

[0607] The flexible copper-clad laminate of the present invention includes the liquid crystal polymer film and a copper foil disposed on at least one surface of the liquid crystal polymer film.

[0608] The flexible copper-clad laminate of the present invention can be produced by forming an adhesive layer on one or both sides of a liquid crystal polymer film and laminating the liquid crystal polymer film to a copper foil via the adhesive layer.

[0609] The copper foil may be any of a rolled copper foil formed by a rolling method and an electrolytic copper foil formed by an electrolysis method, but is preferably a rolled copper foil from the viewpoint of bending resistance.

[0610] The thickness of the copper foil is not particularly limited, but is preferably 3 μm to 15 μm, more preferably 5 μm to 10 μm. The copper foil may be a copper foil with a carrier that is releasably formed on a support (carrier). As the carrier, a known carrier can be used. The thickness of the carrier is not particularly limited, but is preferably 10 μm to 100 μm, more preferably 18 μm to 50 μm.

[0611] <Flexible Printed Circuit Board>

[0612] The flexible printed circuit board of the present invention is formed by processing the copper foil of the flexible copper-clad laminate. Specifically, the flexible printed circuit board of the present invention is preferably produced by etching the copper foil of the flexible copper-clad laminate to form a desired circuit pattern.

[0613] Example

[0614] Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following Examples unless it exceeds the scope of the present invention.

[0615] <Example 1>

[0616] (Pelletization process)

[0617] As the liquid crystal polymer, a thermotropic liquid crystal polyester manufactured by Polyplastics Co., Ltd. (product name: "Laperos C-950", melting point: 320° C., refer to the following formula (I)) was used.

[0618] The liquid crystal polymer was placed in a reaction vessel equipped with a thermometer (thermocouple), a dehydration tube, a nitrogen inlet tube, and a stirring device (stirring blades). The reaction vessel was placed in an oil bath and a nitrogen atmosphere was created. While stirring the contents of the reaction vessel, the temperature within the reaction vessel was raised to 280°C using the oil bath. After heating the liquid crystal polymer in the reaction vessel for 480 minutes, the liquid crystal polymer was removed from the reaction vessel and cooled to obtain a heat-treated liquid crystal polymer.

[0619] To 90 parts by mass of the heat-treated liquid crystal polymer was added 10 parts by mass of an ethylene-glycidyl methacrylate copolymer (product name: Bond First BF-2C, manufactured by Sumitomo Chemical Co., Ltd.), and the mixture was kneaded and pelletized using a twin-screw extruder. The twin-screw extruder barrel temperature during kneading and pelletization was set to 330°C and the shear rate (hereinafter also referred to as "shear rate (pelletization)") was set to 300 seconds. -1 .

[0620] The kneaded pellets were dried for 12 hours by passing air at 80° C. and a dew point of −45° C. through a dehumidified hot air dryer to adjust the water content in the kneaded pellets to 50 ppm by mass or less.

[0621] [Chemical Formula 1]

[0622]

[0623] (In formula (I), m and n represent the molar ratio of the structural units, m:n=77:23.)

[0624] [Film-making process]

[0625] 100 parts by mass of dried kneaded pellets, 0.1 parts by mass of a solid lubricant (stearic acid), and 0.1 parts by mass of a solid heat stabilizer (Irganox 1010 (manufactured by BASF)) were fed into the barrel from the same supply port of a twin-screw extruder with a screw diameter of 50 mm. The mixture was heated and kneaded at 340°C to 350°C to obtain a kneaded product. The molten kneaded product was then extruded from a T-die with a die width of 750 mm and a slit spacing of 300 μm into a film-like state. The time from the kneaded product passing through the twin-screw extruder until the film-like kneaded product was extruded from the T-die (hereinafter also referred to as the "residence time (film formation time)") was set to 8 minutes.

[0626] The thickness unevenness in the width direction of the film was improved by finely adjusting the gap of the die lip portion. In this manner, a liquid crystal polymer film of Example 1 having a thickness of 100 μm was obtained.

[0627] The thickness of the liquid crystal polymer film was measured using a contact thickness meter (manufactured by Mitutoyo Corporation). The arithmetic mean of the thickness of the liquid crystal polymer film at 100 different points was calculated and used as the thickness of the liquid crystal polymer film.

[0628] <Example 2>

[0629] A liquid crystal polymer film of Example 2 was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 840 minutes.

[0630] <Example 3>

[0631] A liquid crystal polymer film of Example 3 was obtained in the same manner as in Example 1 except that the extruder barrel temperature in the kneading and pelletizing step was changed to 350°C.

[0632] <Example 4>

[0633] A liquid crystal polymer film of Example 4 was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 240 minutes.

[0634] <Example 5>

[0635] A liquid crystal polymer film of Example 5 was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 1200 minutes.

[0636] <Example 6>

[0637] A liquid crystal polymer film of Example 6 was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 600 minutes.

[0638] <Example 7>

[0639] A liquid crystal polymer film of Example 7 was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 550 minutes.

[0640] <Example 8>

[0641] A liquid crystal polymer film was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 1320 minutes.

[0642] <Example 9>

[0643] A liquid crystal polymer film was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 3000 minutes.

[0644] <Comparative Example 1>

[0645] A liquid crystal polymer film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the heating treatment of the liquid crystal polymer was omitted.

[0646] <Comparative Example 2>

[0647] A liquid crystal polymer film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 60 minutes.

[0648] <Comparative Example 3>

[0649] A liquid crystal polymer film was obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 3240 minutes.

[0650] <Evaluation>

[0651] (Tear strength evaluation)

[0652] Five test pieces were cut out from the LCP film obtained in each example, each having a length of 75 mm in the TD direction and 63 mm in the MD direction of the LCP film. The tear strength of the obtained test pieces was measured according to JIS 7128-2:1998.

[0653] Furthermore, the test piece was divided along a direction corresponding to the MD direction of the liquid crystal polymer film.

[0654] (Film Formability Evaluation)

[0655] In the film forming step of each example, the state of the film-shaped kneaded product discharged from the T-die was visually observed and evaluated based on the following evaluation criteria.

[0656] -Evaluation Criteria-

[0657] A: No film breakage or holes occurred when the kneaded product was discharged from the T-die, and no visually observable unevenness existed on the surface of the obtained liquid crystal polymer film.

[0658] B: When the kneaded product was discharged from the T-die, no film breakage or holes occurred, but visually observable irregularities were generated on the surface of the obtained liquid crystal polymer film.

[0659] C: Film breakage and holes occurred when the kneaded product was discharged from the T-die, and the obtained liquid crystal polymer film was not practical.

[0660] Table 1 shows the melting point, number average molecular weight, melt viscosity, crystal fusion heat, and various evaluation results of the liquid crystal polymer film obtained in each example.

[0661] In addition, the melting point, number average molecular weight, melt viscosity and heat of crystal fusion of the liquid crystal polymer film were measured according to the above-described method.

[0662] [Table 1]

[0663]

[0664] From the above results, it is understood that the liquid crystal polymer film of this example has high tear resistance and excellent film forming properties.

[0665] <Example 101>

[0666] ·Method for manufacturing liquid crystal polymer film

[0667] A liquid crystal polymer film was obtained in the same manner as in Example 1 except that the pelletizing step and the film forming step were performed in the following order.

[0668] (Pelletization process)

[0669] Kneaded pellets were obtained in the same manner as in Example 1 except that the heat treatment time of the liquid crystal polymer was changed to 2400 minutes.

[0670] (Film-making process)

[0671] 100 parts by mass of dried kneaded pellets, 0.1 parts by mass of a solid lubricant (stearic acid), and 0.1 parts by mass of a solid heat stabilizer (Irganox 1010 (manufactured by BASF)) were supplied into the barrel from the same supply port of a twin-screw extruder having a screw diameter of 50 mm. After heating and kneading at 340°C to 350°C to obtain a kneaded product, a film-like kneaded product in a molten state was discharged from a T-die having a die width of 750 mm and a slit spacing of 300 μm. After the kneaded product passed through the twin-screw extruder, the time from when the film-like kneaded product was discharged from the T-die (hereinafter also referred to as “residence time (film making time)”) was set to 8 minutes. The uneven thickness of the film in the width direction was improved by finely adjusting the gap of the die lip.

[0672] The film-shaped kneaded material discharged from the T-die was subjected to a specific heat treatment in which the film-shaped kneaded material was heated and then immediately cooled.

[0673] More specifically, as a specific heat treatment, an infrared heater placed directly below the T-die was used to heat the film-like kneaded product for 2 seconds until the surface temperature reached 330° C. Immediately thereafter, a cold air nozzle placed directly below the infrared heater was used to cool the film-like kneaded product for 2 seconds until the surface temperature decreased at a cooling rate of -50° C. / second.

[0674] Next, the film-shaped kneaded product subjected to the specific heat treatment is wound into a film.

[0675] Next, the wound film was introduced into a hot air drying furnace set at 350° C. and heated for 1 hour to perform an annealing treatment.

[0676] The annealed film was conveyed while being guided by rollers and then pinched by nip rollers to obtain a liquid crystal polymer film having a thickness of 50 μm.

[0677] Production of metal-clad laminate (step B)

[0678] By laminating the liquid crystal polymer film produced in the above process and two sheets of the copper foil 1 described below, and introducing the laminate into a continuous hot press between a heat-resistant rubber roller and a heated metal roller for pressure bonding, a copper-clad laminate was produced in which the copper foil 1, the liquid crystal polymer film, and the copper foil 1 were laminated in this order.

[0679] A resin-coated metal roller (manufactured by Yuri Roll Machine Co., Ltd., product name: Super Tempex, resin thickness: 1.7 cm) was used as the heat-resistant rubber roller. Furthermore, the heat-resistant rubber roller and the heated metal roller had a diameter of 40 cm.

[0680] The surface temperature of the heated metal roller and the heat-resistant rubber roller was set to 260° C. The pressure applied to the liquid crystal polymer film and the copper foil 1 between the heat-resistant rubber roller and the heated metal roller was set to 120 kg / cm in terms of surface pressure. 2 .

[0681] (metal foil)

[0682] The following metal foils were used in the production of the metal-clad laminate.

[0683] Copper foil 1: rolled copper foil, thickness 12 μm, surface roughness Ra 0.9 μm.

[0684] 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 using a surface roughness meter (manufactured by Mitutoyo Corporation, product name: SURFTEST SJ-201) in accordance with JIS B0601 and averaging the measured values.

[0685] <Example 102>

[0686] ·Method for manufacturing liquid crystal polymer film

[0687] A liquid crystal polymer film and a copper-clad laminate were obtained in the same manner as in Example 101 except that no specific heat treatment was performed.

[0688] <Example 103>

[0689] ·Method for manufacturing liquid crystal polymer film

[0690] A liquid crystal polymer film and a copper-clad laminate were obtained in the same manner as in Example 101 except that the annealing treatment was not performed.

[0691] <Example 104>

[0692] ·Method for manufacturing liquid crystal polymer film

[0693] A liquid crystal polymer film and a copper-clad laminate were obtained in the same manner as in Example 101 except that the specific heat treatment and annealing treatment were not performed.

[0694] Table 2 shows the melting point, number average molecular weight, melt viscosity, crystal fusion heat, and various evaluation results of the liquid crystal polymer film obtained in each example.

[0695] In addition, the melting point, number average molecular weight, melt viscosity and heat of crystal fusion of the liquid crystal polymer film were measured according to the above-described method.

[0696] <Elastic modulus>

[0697] The elastic modulus of the liquid crystal polymer film produced in each example was measured by the following method.

[0698] The liquid crystal polymer films produced in each example were cut along the thickness direction to create cross-sections. On these cross-sections, the elastic modulus A at position A, located halfway between one surface and the other, and the elastic modulus B at position B, located 1 / 8 of the thickness of the liquid crystal polymer film, were measured using nanoindentation.

[0699] The elastic modulus was measured using a nanoindenter (TI-950, manufactured by Hysitron) and a Berkovich indenter. Ten measurements were taken at each location under the following conditions: a load of 500 μN, a loading time of 10 seconds, a retention time of 5 seconds, and an unloading time of 10 seconds. The arithmetic mean of the 10 points was used as the elastic modulus (unit: GPa).

[0700] Table 2 described later shows the elastic modulus A at position A, the elastic modulus B at position B, and the ratio of the elastic modulus B to the elastic modulus A (ratio B / A).

[0701] <Dielectric Properties>

[0702] The center portion of the liquid crystal polymer film manufactured in each example was sampled, and the dielectric loss tangent and relative dielectric constant in the 28 GHz frequency band were measured using a split cylindrical resonator ("CR-728" manufactured by KANTO Electronic Application and Development Inc.) and a network analyzer (Keysight N5230A) at a temperature of 23°C and a humidity of 50% RH.

[0703] <Void Region of Liquid Crystal Polymer Film>

[0704] The void area of the liquid crystal polymer film produced in each example was measured by the following method.

[0705] The liquid crystal polymer film produced in each example was cut along its thickness using a diamond knife on a microtome at room temperature (25°C). The exposed cross-section of the liquid crystal polymer film was immersed in monomethylamine at room temperature (25°C) for 4 hours. Distilled water was dripped onto the cross-section for cleaning, and water droplets were removed using an air soot blower. The cross-section of the liquid crystal polymer film was then photographed using a scanning electron microscope (SEM) (Hitachi High-Tech Fielding Corporation, "S-4800") at an accelerating voltage of 2 kV and a magnification of 3000x.

[0706] The captured image was binarized using the Threshold function of the image processing software "ImageJ," separating the image into dark and bright areas to generate image processing data. The image processing software automatically determined the threshold for binarization based on the contrast of the captured image, ranging from 88 to 105 on a 256-level scale. The captured image area was 15 μm in the thickness direction and 42 μm in the transport direction. The dark areas in the binarized image processing data correspond to the voids in the liquid crystal polymer film.

[0707] The area of dark areas in the binarized image data was automatically detected and measured. The area of each void region was calculated from the measured values, and the average area of the void regions was calculated. Next, the dark areas in the binarized image data were thinned using the line thinning function of the image processing software, and the length of each dark region was automatically detected and measured. For each void region, the average length was calculated from the automatically detected and measured data. The average width of the void regions was calculated by dividing the average area of the void regions by the average length of the void regions.

[0708] In addition, in the captured images of the above-mentioned cross-section, the following regions are distinguished, namely, the first surface region within 5 μm from one surface, the second surface region within 5 μm from the other surface, and the middle region within 2.5 μm from the center line equidistant from the two surfaces. Binarized data is obtained from the captured images of n=2, and the area ratio of the void region in each region (void area ratio) is calculated.

[0709] The void area ratio is the ratio (%) of the total void area in each region to the area of each region in the cross section of the LCP film. The void area ratio in the entire thickness direction of the LCP film cross section is calculated simultaneously with the void area ratio.

[0710] <Void Area Ratio X, Void Area Ratio Y>

[0711] The void area ratio of the liquid crystal polymer film produced in each example was measured by the following method.

[0712] The liquid crystal polymer film produced in each example was cut along its thickness using a diamond knife on a microtome at room temperature (25°C). The exposed cross-section of the liquid crystal polymer film was immersed in monomethylamine at room temperature (25°C) for 4 hours. Distilled water was dripped onto the cross-section for cleaning, and water droplets were removed using an air soot blower. The cross-section of the liquid crystal polymer film was then photographed using a scanning electron microscope (SEM) (Hitachi High-Tech Fielding Corporation, "S-4800") at an accelerating voltage of 2 kV and a magnification of 3000x.

[0713] The captured image was binarized using the Threshold function of the image processing software "ImageJ," separating the image into dark and bright areas to generate image processing data. The image processing software automatically determined the threshold for binarization based on the contrast of the captured image, ranging from 88 to 105 on a 256-level scale. The captured image area was 15 μm in the thickness direction and 42 μm in the transport direction. The dark areas in the binarized image processing data correspond to the voids in the liquid crystal polymer film.

[0714] The area of the dark portion is automatically detected and measured from the binarized image processing data, the area of each void region is determined from the obtained measurement values, and the average area of the void regions is determined.

[0715] A position located at 1 / 10 of the thickness of the liquid crystal polymer film from one surface to the other is designated as position T1, a position located at 4 / 10 of the thickness of the liquid crystal polymer film is designated as position T2, and a position located at 6 / 10 of the thickness of the liquid crystal polymer film is designated as position T3. The region from one surface to position T1 is designated as region S, and the region from position T2 to position T3 is designated as region C. Binarized data is obtained from captured images with n = 2, and the void area ratio X, which is the area ratio of voids in region S, and the void area ratio Y, which is the area ratio of voids in region C, are calculated. Each void area ratio refers to the ratio (%) of the area of voids in each region relative to the area of each region in the cross section of the liquid crystal polymer film.

[0716] Table 2 described later shows the value of "void area ratio Y-void area ratio X" (described as (YX) in the table).

[0717] <Hardness>

[0718] The hardness of the liquid crystal polymer film produced in each example was measured by the following method.

[0719] The liquid crystal polymer film produced in each example was embedded in epoxy resin, cut along the thickness direction of the embedded liquid crystal polymer film, and the exposed cross section was ground using a microtome to obtain a cut surface for measurement. The hardness A at position A, located halfway between one surface and the other, and the hardness B at position B, located 1 / 10 of the thickness of the liquid crystal polymer film, were measured on the obtained cut surface using nanoindentation.

[0720] The measurement was performed in accordance with ISO 14577. Specifically, it was performed using Belkovic indenter TI-950 (Nano Tribo Indenter) (manufactured by Bruker Japan KK). Six points were measured at each position under an indentation load of 500 μN, and the arithmetic mean of the six points was defined as the hardness (unit: GPa).

[0721] Table 2 described below shows the value of "(Hardness A+Hardness B) / 2" (described as (A+B) / 2 in the table) and the value of "Hardness A-Hardness B" (described as (AB) in the table).

[0722] <Linear Expansion Coefficient>

[0723] The linear expansion coefficient of the liquid crystal polymer film produced in each example was measured by the following method.

[0724] A sample with a width of 6 mm and a length of 6 mm was cut from the center of the liquid crystal polymer film produced in each example, and the sample was placed on the sample stage of a thermomechanical analyzer ("TMA-Q400" manufactured by TA Instruments Japan Inc.). Then, the linear expansion coefficient (CTE) in the in-plane direction of the liquid crystal polymer film was measured.

[0725] <Evaluation>

[0726] Table 3 shows the results of the following evaluations.

[0727] (Tear strength evaluation, film forming property evaluation)

[0728] The tear strength evaluation and film forming property evaluation were performed in the order described.

[0729] (Adhesion)

[0730] The copper-clad laminate produced in each example was cut into 1 cm × 5 cm strips 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 adhesion measurement test was carried out by using a tensile testing machine (manufactured by IMADA CO., LTD., Digital Force Gauge ZP-200N) and peeling off the copper foil at a peeling speed of 50 mm per minute in a direction at a 90° angle relative to the copper foil removal surface. The values measured by the tensile testing machine were used to evaluate the adhesion between the metal foil and the liquid crystal polymer film.

[0731] (Position Offset)

[0732] The double-sided copper-clad laminate produced in each example was cut into a size of 15 cm × 15 cm to produce a sample of the double-sided copper-clad laminate. A mask layer was laminated on the surface of one copper layer of the obtained sample, and the mask layer was pattern-exposed and then developed to form a mask pattern. Next, the surface of the sample only on the mask pattern side was immersed in a 40% iron (III) chloride aqueous solution (manufactured by FUJIFILM Wako Pure Chemical Corporation, first-class), and the copper layer not laminated with the mask pattern was etched. After that, the mask pattern was peeled off to form a copper wiring (microstrip line).

[0733] The dimensions of the copper wiring were 10 μm in length and 105 μm in width. In this manner, a first sample was obtained in which the copper wiring was formed on one surface and the copper layer was formed on the entire surface of the other surface.

[0734] A single-sided copper-clad laminate was produced in the same manner as in step B of each example, except that the liquid crystal polymer film and a single copper foil were laminated. The resulting single-sided copper-clad laminate was then cut into 15 cm x 15 cm pieces to produce a single-sided copper-clad laminate sample. The copper layer of the resulting sample was treated, including the same etching process as described above, to produce a second sample having copper wiring formed on one surface at the same position and size as the copper wiring of the first sample.

[0735] The first sample and the second sample were stacked so that the surface of the first sample on the copper wiring side was in contact with the surface of the second sample on which no copper wiring was formed, and the in-plane positions of the respective copper wirings were aligned.

[0736] The obtained multilayer laminate was introduced between a pair of heated metal rollers in a continuous hot press and thermocompression bonded. The surface temperature of the heated metal rollers was set to 260°C, and the pressure applied to the multilayer laminate was set to 40 kg / cm2 in terms of surface pressure.

[0737] The multilayer laminate produced by the above method was cut into a cross section that included the stacking direction and was perpendicular to the long side of each copper wiring. The resulting cut surface was observed using a scanning electron microscope (SEM). In the observed cross-sectional image, the position of the copper wiring of the first sample was compared with the position of the copper wiring of the second sample, and the difference in the position of the copper wiring of the first sample relative to the position of the copper wiring of the second sample in the in-plane direction (the short side of the copper wiring) was measured.

[0738] From the measured differences, the positional displacement of the metal-clad laminate produced in each example was evaluated based on the following evaluation criteria.

[0739] (Position deviation evaluation criteria)

[0740] A: The positional shift ratio of the copper wiring relative to the thickness of the liquid crystal polymer film is less than 1%.

[0741] B: The positional shift ratio of the copper wiring relative to the thickness of the liquid crystal polymer film is 1% or more and less than 3%.

[0742] C: The positional deviation ratio of the copper wiring relative to the thickness of the liquid crystal polymer film is 3% or more and less than 5%.

[0743] D: The positional deviation ratio of the copper wiring relative to the thickness of the liquid crystal polymer film is 5% or more.

[0744] In the "Peeled Surface" column of "Evaluation" in Table 3, "LCP Present" indicates that liquid crystal polymer adheres to the peeled surface of the peeled copper foil, and "Copper Foil Interface" indicates that liquid crystal polymer does not adhere to the peeled surface of the peeled copper foil.

[0745] [Table 2-1]

[0746]

[0747] [Table 2-2]

[0748]

[0749] [Table 3]

[0750]

[0751] From the above results, it is understood that the liquid crystal polymer film of this example has high tear resistance and excellent film forming properties.

[0752] Furthermore, it is found that Example 101, in which the ratio B / A of the elastic modulus B to the elastic modulus A is 0.99 or less and the elastic modulus A is 4.0 GPa or more, has excellent performance in suppressing wiring position deviation.

[0753] Furthermore, it was found that the metal foils of Examples 101 and 102, in which the average width of the void regions was 0.01 to 0.1 μm and the area ratio of the void regions was 20% or less, had excellent adhesion (excellent peel strength) to the liquid crystal polymer film.

[0754] Moreover, it can be seen that the example 101 that satisfies the formula (1A) (hardness A + hardness B) / 2≥0.10GPa and the formula (2A) void area ratio Y-void area ratio X≥0.10% has a low dielectric loss tangent and a small difference with the linear expansion coefficient of the copper foil.

[0755] The disclosure of Japanese Patent Application No. 2020-166406 filed on September 30, 2020 is incorporated herein by reference in its entirety.

[0756] All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each document, patent application, or technical standard was specifically and individually described as being incorporated by reference.

Claims

1. A liquid crystal polymer film comprising a liquid crystal polymer, The liquid crystal polymer film has a melting point of 315° C. or higher and a number average molecular weight of 13,000 or higher and 150,000 or lower. In a cross section cut along the thickness direction of the liquid crystal polymer film, when the elastic modulus at position A located at half the distance of the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is set as elastic modulus A, and the elastic modulus at position B located at 1 / 8 the distance of the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is set as elastic modulus B, the ratio B / A of the elastic modulus B to the elastic modulus A is less than 0.99, and the elastic modulus A is greater than 4.0 GPa. 2 . The liquid crystal polymer film according to claim 1 , wherein the number average molecular weight is 18,000 to 150,000.

3. The liquid crystal polymer film according to claim 1 or 2, wherein When the temperature is set to 5°C higher than the melting point and the shear rate is set to 1000 sec -1 When the melt viscosity of the liquid crystal polymer film is 80 Pa·s or more and 400 Pa·s or less. 4 . The liquid crystal polymer film according to claim 1 , wherein the liquid crystal polymer film has a crystalline fusion heat value of 2 J / g or less as measured by differential scanning calorimetry. The liquid crystal polymer film according to claim 1 or 2, which is used for a flexible printed circuit board.

6. The liquid crystal polymer film according to claim 1 or 2, wherein The elastic modulus A is greater than or equal to 4.6 GPa.

7. The liquid crystal polymer film according to claim 1 or 2, wherein After exposing a cross section cut along the thickness direction of the liquid crystal polymer film and immersing it in monomethylamine, when 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 μm to 0.1 μm, and The area ratio of the void region in the observed image of the cross section is 20% or less.

8. The liquid crystal polymer film according to claim 7, wherein The average length of the void region is 3 μm to 5 μm.

9. The liquid crystal polymer film according to claim 7, which has a thickness of 15 μm or more and satisfies the following requirement A: Requirement A: In the cross-section, when the area within 5 μm from one surface of the liquid crystal polymer film is set as the first surface area, the area within 5 μm from the other surface of the liquid crystal polymer film is set as the second surface area, and the area within 2.5 μm from the center line equidistant from the two surfaces of the liquid crystal polymer film is set as the central layer area, the area ratio of the void area in the central layer area is greater than the area ratio of the void area in the first surface area, and greater than the area ratio of the void area in the second surface area.

10. The liquid crystal polymer film according to claim 1 or 2, wherein In a cross section taken along the thickness direction of the liquid crystal polymer film, when the hardness at a position A located at half the thickness of the liquid crystal polymer film from one surface toward the other surface of the liquid crystal polymer film is defined as hardness A, and the hardness at a position B located at 1 / 10 the thickness of the liquid crystal polymer film from the one surface toward the other surface of the liquid crystal polymer film is defined as hardness B, the following relationship is satisfied: In the cross section, when a position located at 1 / 10 of the thickness of the liquid crystal polymer film from the one surface toward the other surface thereof is defined as position T1, a position located at 4 / 10 of the thickness of the liquid crystal polymer film is defined as position T2, a position located at 6 / 10 of the thickness of the liquid crystal polymer film is defined as position T3, a region from the one surface to the position T1 is defined as region S, a region from the position T2 to the position T3 is defined as region C, an area ratio of a void region in the region S is defined as void area ratio X, and an area ratio of a void region in the region C is defined as void area ratio Y, the following relationship is satisfied: Formula (1A) (Hardness A + Hardness B) / 2 ≥ 0.10 GPa Formula (2A) Void area ratio Y - void area ratio X ≥ 0.10%.

11. The liquid crystal polymer film according to claim 10, wherein The hardness A and the hardness B satisfy the relationship of the following formula (1B): Formula (1B) (Hardness A - Hardness B) ≥ -0.02 GPa. 12 . The liquid crystal polymer film according to claim 1 , which has a single-layer structure.

13. The liquid crystal polymer film according to claim 1 or 2, wherein The liquid crystal polymer film has a dielectric loss tangent of 0.0022 or less at a temperature of 23° C. and a frequency of 28 GHz.

14. The liquid crystal polymer film according to claim 1 or 2, wherein The liquid crystal polymer includes at least one selected from a repeating unit derived from p-hydroxybenzoic acid and a repeating unit derived from 6-hydroxy-2-naphthoic acid.

15. The liquid crystal polymer film according to claim 1 or 2, wherein The liquid crystal polymer includes at least one selected from 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-naphthalene dicarboxylic acid.

16. The liquid crystal polymer film according to claim 1 or 2, further comprising a polyolefin, The content of the polyolefin is 40% by mass or less relative to the total mass of the liquid crystal polymer film. 17 . A flexible copper-clad laminate comprising the liquid crystal polymer film according to claim 1 and a copper foil disposed on at least one surface of the liquid crystal polymer film. 18 . A method for producing a liquid crystal polymer film according to claim 1 , comprising a film-forming step of extruding a melt-kneaded liquid crystal polymer through a T-die to form a film.

Images