Liquid crystal polymer film, substrate for high-speed communication

Abstract

A problem addressed by the present invention is to provide a liquid crystal polymer film having a lower dielectric loss tangent. Also, a problem addressed by the present invention is to provide a high-speed communication board having the liquid crystal polymer film. The polymer film of the present invention includes a liquid crystal polymer, and the area of a melting peak measured by differential scanning calorimetry is 0.2 J / g or more.

Description

[Technical Field]

[0001] This disclosure relates to liquid crystal polymer films and substrates for high-speed communication. [Background technology]

[0002] The fifth-generation (5G) mobile communication system, considered the next-generation communication technology, utilizes even higher frequencies and wider bandwidths than before. Therefore, substrate films with low dielectric constant and low dielectric loss tangent are required for circuit boards used in 5G mobile communication systems, and development is underway using various materials. One such substrate film is liquid crystal polymer film. Liquid crystal polymer (LCP) film has a lower dielectric constant and lower dielectric loss tangent than films such as polyimide film and glass epoxy film, which are widely used in fourth-generation (4G) mobile communication systems.

[0003] Because liquid crystal polymers have a rod-like molecular structure, they exhibit strong orientation. When liquid crystal polymers are melt-extruded, shear stress from die slitting and melt draw tend to cause the polymer to orient in the longitudinal direction (MD direction: Machine Direction). Therefore, liquid crystal polymer films produced by melt extrusion tend to be uniaxially oriented films. For example, Patent Document 1 describes a liquid crystal polymer film made of a thermoplastic polymer capable of forming an optically anisotropic molten phase, wherein the rate of change of the relative permittivity (εr2) after heating the film relative to the relative permittivity (εr1) before heating the film is within a predetermined range at frequencies from 1 to 100 GHz. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2013 / 065453 [Overview of the project] [Problems that the invention aims to solve]

[0005] As described above, with the increasing speed of processing, there is a growing need for further improvements in the dielectric properties (e.g., dielectric loss) of liquid crystal polymer films used in circuit boards. The inventors of the present invention manufactured a liquid crystal polymer film by referring to the film described in Patent Document 1, and discovered that there is room for further improvement in the dielectric loss tangent of the liquid crystal polymer film.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a liquid crystal polymer film with a lower dielectric loss tangent. Furthermore, the present invention aims to provide a high-speed communication substrate having a liquid crystal polymer film. [Means for solving the problem]

[0007] As a result of diligent research into the above problems, the inventors have found that the above problems can be solved by the following configuration.

[0008] [1] A liquid crystal polymer film containing a liquid crystal polymer, wherein the area of ​​the melting peak measured by differential scanning calorimetry is 0.2 J / g or more. [2] A liquid crystal polymer film as described in [1], wherein the ratio AT / AM obtained by method 1 described later is 1.0 to 1.5. [3] A liquid crystal polymer film according to [1] or [2], wherein the dielectric loss tangent under conditions of a temperature of 23°C, a humidity of 50%RH, and a frequency of 28GHz is 0.002 or less. [4] A liquid crystal polymer film according to any one of [1] to [3], wherein the dielectric loss tangent of the liquid crystal polymer under the conditions of a temperature of 23°C, a humidity of 50%RH, and a frequency of 28GHz is 0.002 or less. [5] The liquid crystal polymer film according to any one of [1] to [4], having a linear expansion coefficient in the film thickness direction of 50 to 450 ppm / °C. 〔6〕 The liquid crystal polymer film according to any one of [1] to [5], wherein the first linear expansion coefficient in the first direction in the plane of the liquid crystal polymer film and the second linear expansion coefficient in the second direction orthogonal to the first direction in the plane of the liquid crystal polymer film are both 10 to 30 ppm / °C, and the first linear expansion coefficient is the minimum value of the linear expansion coefficient in the plane of the liquid crystal polymer film. 〔7〕 The liquid crystal polymer film according to [6], wherein the ratio of the second linear expansion coefficient to the first linear expansion coefficient is 1.0 to 1.5. 〔8〕 The liquid crystal polymer film according to any one of [1] to [7], having a surface roughness Ra of less than 430 nm. 〔9〕 The liquid crystal polymer film according to any one of [1] to [8], wherein the melting point Tm of the liquid crystal polymer is 285°C or higher. 〔10〕 The film according to any one of [1] to [9], wherein the liquid crystal polymer has at least one selected from the group consisting of a repeating unit derived from p-hydroxybenzoic acid and a repeating unit derived from �-hydroxy-2-naphthoic acid. 〔11〕 The liquid crystal polymer film according to any one of [1] to [9], wherein the liquid crystal polymer has at least one selected from the group consisting of a repeating unit derived from �-hydroxy-2-naphthoic acid, a repeating unit derived from an aromatic diol compound, a repeating unit derived from terephthalic acid, and a repeating unit derived from 2,6-naphthalenedicarboxylic acid. 〔12〕 The liquid crystal polymer film according to any one of [1] to

[11] , further comprising a polyolefin. 〔13〕 The liquid crystal polymer film according to

[12] , wherein the content of the polyolefin is 0.1 to 40% by mass based on the total mass of the liquid crystal polymer film. 〔14〕 The liquid crystal polymer film according to

[12] or

[13] , wherein the polyolefin forms a dispersed phase in the liquid crystal polymer film, and the average dispersion diameter of the dispersed phase is 0.01 to 10 μm.

[15] A high-speed communication substrate having a liquid crystal polymer film as described in any of [1] to

[14] . [Effects of the Invention]

[0009] According to the present invention, a liquid crystal polymer film with a lower dielectric loss tangent can be provided. Furthermore, according to the present invention, a high-speed communication substrate having the above-mentioned liquid crystal polymer film can be provided. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below. The following description of the constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, regarding the notation of groups (atomic groups), unless contrary to the spirit of the present invention, notations that do not specify substituted or unsubstituted include both substituted and unsubstituted groups. For example, "alkyl group" includes not only unsubstituted alkyl groups but also substituted alkyl groups. Furthermore, in this specification, "organic group" means a group containing at least one carbon atom.

[0011] In this specification, when a liquid crystal polymer film is elongated, the width direction of the liquid crystal polymer film refers to the short side direction and the TD (transverse direction), and the length direction refers to the longitudinal direction and the MD (machine direction) of the liquid crystal polymer film. In this specification, each component may be made using one substance alone or two or more substances. When two or more substances are used in combination for each component, the content of that component refers to the total content of the two or more substances unless otherwise specified. In this specification, "~" is used to mean that the numbers before and after it are included as the lower and upper limits, respectively. In this specification, the dielectric loss tangent of the liquid crystal polymer film and the dielectric loss tangent of the liquid crystal polymer are both the dielectric loss tangent under conditions of a temperature of 23°C, a humidity of 50%RH, and a frequency of 28GHz. Hereinafter, in this specification, the dielectric loss tangent under conditions of a temperature of 23°C, a humidity of 50%RH, and a frequency of 28GHz will also be simply referred to as "dielectric loss tangent". In this specification, "film width" means the distance between the two ends in the width direction of a long liquid crystal polymer film.

[0012] The liquid crystal polymer film of the present invention is a liquid crystal polymer film comprising a liquid crystal polymer, wherein the area of ​​the melting peak measured by differential scanning calorimetry (DSC) is 0.05 to 30 J / g. Hereinafter, in the context of liquid crystal polymer films, having a lower dielectric loss tangent is also referred to as "the effects of the present invention being superior." Furthermore, in this specification, liquid crystal polymer film may sometimes be simply referred to as "film."

[0013] [component] First, the components of the liquid crystal polymer film of the present invention will be described.

[0014] [Liquid crystal polymer] The film of the present invention contains a liquid crystal polymer. The liquid crystal polymer is preferably a liquid crystal polymer that can be melt-molded.

[0015] A thermotropic liquid crystal polymer is preferred. A thermotropic liquid crystal polymer refers to a polymer that exhibits liquid crystal properties within a predetermined temperature range. Thermotropic liquid crystal polymers are not particularly limited in their chemical composition as long as they are liquid crystal polymers that can be melt-molded. Examples include thermoplastic liquid crystal polyesters and thermoplastic polyesteramides, in which amide bonds are introduced into thermoplastic liquid crystal polyesters. As the liquid crystal polymer, for example, thermoplastic liquid crystal polymers described in International Publication No. 2015 / 064437 and Japanese Patent Publication No. 2019-116586 can be used.

[0016] Preferred examples of liquid crystal polymers include thermoplastic liquid crystal polyesters or thermoplastic liquid crystal polyesteramides having repeating units derived from at least one selected from the group consisting of aromatic hydroxycarboxylic acids, aromatic or aliphatic diols, aromatic or aliphatic dicarboxylic acids, aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids.

[0017] Examples of aromatic hydroxycarboxylic acids include parahydroxybenzoic acid, metahydroxybenzoic 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 these, parahydroxybenzoic acid or 6-hydroxy-2-naphthoic acid are preferred. As the aromatic or aliphatic diol, aromatic diols are preferred. Examples of aromatic diols include hydroquinone, 4,4'-dihydroxybiphenyl, 3,3'-dimethyl-1,1'-biphenyl-4,4'-diol, and their acylated products, with hydroquinone or 4,4'-dihydroxybiphenyl being preferred. As for aromatic or aliphatic dicarboxylic acids, aromatic dicarboxylic acids are preferred. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, with terephthalic acid being preferred. Examples of aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids include p-phenylenediamine, 4-aminophenol, and 4-aminobenzoic acid.

[0018] The liquid crystal polymer preferably has at least one repeating unit selected from the group consisting of repeating units derived from aromatic hydroxycarboxylic acids, repeating units derived from aromatic diols, and repeating units derived from aromatic dicarboxylic acids. In particular, the liquid crystal polymer is more preferably having at least repeating units derived from aromatic hydroxycarboxylic acid, even more preferably having at least one selected from the group consisting of repeating units derived from parahydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid, and especially preferably having repeating units derived from parahydroxybenzoic acid and repeating units derived from 6-hydroxy-2-naphthoic acid.

[0019] In another preferred embodiment, the liquid crystal polymer more preferably has at least one 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 even more 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.

[0020] When the liquid crystal polymer contains repeating units derived from aromatic hydroxycarboxylic acids, the composition ratio of these units is preferably 50 to 65 mol% of the total repeating units of the liquid crystal polymer. It is also preferable for the liquid crystal polymer to contain only repeating units derived from aromatic hydroxycarboxylic acids. When the liquid crystal polymer contains repeating units derived from aromatic diols, the composition ratio is preferably 17.5 to 25 mol% relative to the total repeating units of the liquid crystal polymer. When the liquid crystal polymer contains repeating units derived from aromatic dicarboxylic acids, the composition ratio of these units is preferably 11 to 23 mol% relative to the total repeating units of the liquid crystal polymer. When the liquid crystal polymer contains repeating units derived from any of aromatic diamines, aromatic hydroxyamines, and aromatic aminocarboxylic acids, the composition ratio is preferably 2 to 8 mol% relative to the total repeating units of the liquid crystal polymer.

[0021] The method for synthesizing the liquid crystal polymer is not particularly limited, and the above compound can be synthesized by polymerizing it using known methods such as melt polymerization, solid-phase polymerization, solution polymerization, and slurry polymerization. Commercially available liquid crystal polymers may be used. Examples of commercially available liquid crystal polymers include "Laperos" from Polyplastics, Inc., "Vectra" from Celanese, Inc., "UENO LCP" from Ueno Pharmaceutical Co., Ltd., "Sumika Super LCP" from Sumitomo Chemical Co., Ltd., "Zyder" from ENEOS Corporation, and "Siberas" from Toray Industries, Inc. Furthermore, the liquid crystal polymer may form chemical bonds with optional components such as crosslinking agents or compatible components (reactive compatibilizers) within the film. This also applies to components other than the liquid crystal polymer.

[0022] For the effects of the present invention to be more pronounced, the dielectric loss tangent of the liquid crystal polymer is preferably 0.003 or less, more preferably 0.0025 or less, and even more preferably 0.002 or less. The lower limit is not particularly restricted and may be, for example, 0.0001 or greater. In this specification, when the film contains two or more liquid crystal polymers, "dielectric loss tangent of liquid crystal polymers" means the average mass value of the dielectric loss tangents of the two or more liquid crystal polymers.

[0023] The dielectric loss tangent of the liquid crystal polymer contained in the film can be measured by the following method. First, the film is immersed in an organic solvent (e.g., pentafluorophenol) at a concentration 1000 times its total mass, and then heated at 120°C for 12 hours to elute the organic solvent-soluble components, including the liquid crystal polymer, into the organic solvent. Next, the eluate containing the liquid crystal polymer is separated from the non-eluted components by filtration. Subsequently, acetone is added to the eluate as a poor solvent to precipitate the liquid crystal polymer, and the precipitate is separated by filtration. The obtained precipitate is packed into a PTFE (polytetrafluoroethylene) tube (outer diameter 2.5 mm, inner diameter 1.5 mm, length 10 mm), and the dielectric properties are measured using a cavity resonator (e.g., "CP-531" manufactured by Kanto Electronics Applied Development Co., Ltd.) under conditions of 23°C, 50% RH humidity, and 28 GHz frequency by the cavity resonator perturbation method. The dielectric loss tangent of the liquid crystal polymer is obtained by correcting for the effect of air voids in the PTFE tube using Bruggeman's equation and porosity. The above porosity (volume ratio of voids within the tube) is calculated as follows: The volume of space inside the tube is determined from the inner diameter and length of the tube. Next, the mass of the filled precipitate is determined by measuring the weight of the tube before and after filling with precipitate. Then, the volume of the filled precipitate is determined from the obtained mass and the specific gravity of the precipitate. The porosity can be calculated by dividing the volume of the precipitate obtained in this way by the volume of space inside the tube determined above to calculate the filling rate. When using commercially available liquid crystal polymers, the dielectric loss tangent value listed in the catalog of those products may be used.

[0024] As for the liquid crystal polymer, a melting point Tm of 270°C or higher is preferable, more preferably 285°C or higher, and even more preferably 300°C or higher, in terms of achieving superior effects of the present invention. There is no particular upper limit to the melting point Tm of the liquid crystal polymer, but it is preferably 400°C or lower, and more preferably 380°C or lower. The melting point Tm of a liquid crystal polymer can be determined by measuring the temperature at which an endothermic peak appears using a differential scanning calorimeter (Shimadzu Corporation's "DSC-60A"). When using commercially available liquid crystal polymers, the melting point Tm listed in the catalog of that product may be used.

[0025] Liquid crystal polymers may be used individually or in combination of two or more types. The liquid crystal polymer content is preferably 40 to 99.9% by mass, more preferably 60 to 99% by mass, and even more preferably 80 to 90% by mass, based on the total mass of the film.

[0026] [Optional ingredients] The film may contain additives other than liquid crystal polymers as optional components. Examples of additives include polyolefins, compatible components, heat stabilizers, crosslinking agents, and lubricants.

[0027] <Polyolefin> In this specification, polyolefin refers to a resin having repeating units based on an olefin (polyolefin resin). The film preferably further contains polyolefin in addition to the liquid crystal polymer, and more preferably further contains polyolefin and compatible components. By manufacturing a film containing a polyolefin together with a liquid crystal polymer, a film having a dispersed phase formed by the polyolefin can be produced. The method for manufacturing the film having the dispersed phase will be described later.

[0028] Polyolefins may be linear or branched. Furthermore, polyolefins may have a cyclic structure, such as polycycloolefins. Examples of polyolefins include polyethylene, polypropylene (PP), polymethylpentene (TPX, manufactured by Mitsui Chemicals, Inc.), hydrogenated polybutadiene, cycloolefin polymers (COP, Zeonor, manufactured by Nippon Zeon Corporation, etc.), and cycloolefin copolymers (COC, Apel, manufactured by Mitsui Chemicals, Inc., etc.). Polyethylene may be either high-density polyethylene (HDPE) or low-density polyethylene (LDPE). Alternatively, the polyethylene may be linear low-density polyethylene (LLDPE).

[0029] Polyolefins may also be copolymers of olefins with copolymer components other than olefins, such as acrylates, methacrylates, styrenes, and / or vinyl acetate monomers. Examples of polyolefin copolymers include styrene-ethylene / butylene-styrene copolymer (SEBS). SEBS may be hydrogenated. However, in order to obtain superior effects from the present invention, it is preferable that the copolymerization ratio of copolymerization components other than olefins be small, and more preferably that no copolymerization components are present. For example, the content of the above copolymerization components is preferably 0 to 40% by mass, and more preferably 0 to 5% by mass, relative to the total mass of the polyolefin. Furthermore, the polyolefin preferably contains substantially no reactive groups as described below, and the content of repeating units having reactive groups is preferably 0 to 3% by mass relative to the total mass of the polyolefin.

[0030] As for the polyolefin, polyethylene, COP, or COC are preferred in terms of superior effects of the present invention, polyethylene is more preferred, and low-density polyethylene (LDPE) is even more preferred.

[0031] Polyolefins may be used individually or in combination of two or more types. The polyolefin content is preferably 0.1% by mass or more, and more preferably 5% by mass or more, relative to the total mass of the film, in order to obtain superior surface properties of the film. The upper limit of the above content is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less, in terms of achieving better film smoothness. Furthermore, if the polyolefin content is 50% by mass or less, it is easier to sufficiently raise the heat distortion temperature and improve solder heat resistance.

[0032] <Compatible components> Examples of compatible components include polymers having a portion that is highly compatible or affinity for liquid crystal polymers (non-reactive compatibilizers), and polymers having a reactive group for the phenolic hydroxyl group or carboxyl group at the end of the liquid crystal polymer (reactive compatibilizers). The reactive group of the reactive compatibilizer is preferably an epoxy group or a maleic anhydride group. As the compatible component, copolymers having a portion that has high compatibility or affinity with polyolefins are preferred. Furthermore, when the film contains polyolefins and compatible components, reactive compatibilizers are preferred as compatible components because they can finely disperse the polyolefins. Furthermore, compatible components (especially reactive compatibilizers) may form chemical bonds with components such as liquid crystal polymers within the film.

[0033] Examples of reactive compatibilizers include epoxy group-containing polyolefin copolymers, epoxy group-containing vinyl copolymers, maleic anhydride-containing polyolefin copolymers, maleic anhydride-containing vinyl copolymers, oxazoline group-containing polyolefin copolymers, oxazoline group-containing vinyl copolymers, and carboxyl group-containing olefin copolymers. Among these, epoxy group-containing polyolefin copolymers or maleic anhydride-grafted polyolefin copolymers are preferred.

[0034] Examples of epoxy group-containing polyolefin copolymers include ethylene / glycidyl methacrylate copolymer, ethylene / glycidyl methacrylate / vinyl acetate copolymer, ethylene / glycidyl methacrylate / methyl acrylate copolymer, polystyrene graft copolymer onto ethylene / glycidyl methacrylate copolymer (EGMA-g-PS), polymethyl methacrylate graft copolymer onto ethylene / glycidyl methacrylate copolymer (EGMA-g-PMMA), and acrylonitrile / styrene graft copolymer onto ethylene / glycidyl methacrylate copolymer (EGMA-g-AS). Examples of commercially available epoxy group-containing polyolefin copolymers include Bondfast 2C and Bondfast E manufactured by Sumitomo Chemical Co., Ltd.; Lotadar manufactured by Arkema Ltd.; and Modiper A4100 and Modiper A4400 manufactured by NOF Corporation.

[0035] Examples of epoxy group-containing vinyl copolymers include glycidyl methacrylate-grafted polystyrene (PS-g-GMA), glycidyl methacrylate-grafted polymethyl methacrylate (PMMA-g-GMA), and glycidyl methacrylate-grafted polyacrylonitrile (PAN-g-GMA).

[0036] Examples of maleic anhydride-containing polyolefin copolymers include maleic anhydride-grafted polypropylene (PP-g-MAH), maleic anhydride-grafted ethylene / propylene rubber (EPR-g-MAH), and maleic anhydride-grafted ethylene / propylene / diene rubber (EPDM-g-MAH). Examples of commercially available maleic anhydride-containing polyolefin copolymers include the Orevac G series from Arkema and the FUSABOND E series from Dow Chemical.

[0037] Examples of maleic anhydride-containing vinyl copolymers include maleic anhydride-grafted polystyrene (PS-g-MAH), maleic anhydride-grafted styrene / butadiene / styrene copolymer (SBS-g-MAH), maleic anhydride-grafted styrene / ethylene / butene / styrene copolymer (SEBS-g-MAH), and styrene / maleic anhydride copolymers and acrylic acid ester / maleic anhydride copolymers. A commercially available example of a maleic anhydride-containing vinyl copolymer is Asahi Kasei's ToughTec M series (SEBS-g-MAH).

[0038] Other compatible components include oxazoline-based compatibilizers (e.g., bisoxazoline-styrene-maleic anhydride copolymer, bisoxazoline-maleic anhydride-modified polyethylene, and bisoxazoline-maleic anhydride-modified polypropylene), elastomer-based compatibilizers (e.g., aromatic resins, petroleum resins), ethylene glycidyl methacrylate copolymer, ethylene maleic anhydride ethyl acrylate copolymer, ethylene glycidyl methacrylate-acrylonitrile styrene, acid-modified polyethylene wax, COOH-modified polyethylene graft polymer, COOH-modified polypropylene graft polymer, polyethylene-polyamide graft copolymer, polypropylene-polyamide graft copolymer, methyl methacrylate-butadiene-styrene copolymer, acrylonitrile-butadiene rubber, EVA-PVC-graft copolymer, vinyl acetate-ethylene copolymer, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, hydrogenated styrene-isopropylene-block copolymer, and amine-modified styrene-ethylene-butene-styrene copolymer.

[0039] Additionally, ionomer resin may be used as a compatible component. Examples of such ionomer resins include ethylene-methacrylic acid copolymer ionomers, ethylene-acrylic acid copolymer ionomers, propylene-methacrylic acid copolymer ionomers, propylene-acrylic acid copolymer ionomers, butylene-acrylic acid copolymer ionomers, ethylene-vinyl sulfonic acid copolymer ionomers, styrene-methacrylic acid copolymer ionomers, sulfonated polystyrene ionomers, fluorinated ionomers, telechelic polybutadiene acrylic acid ionomers, and sulfonated ethylene- Examples include polypropylene-diene copolymer ions, hydrogenated polypentamer ions, polypentamer ions, poly(vinylpyridium salt) ions, poly(vinyltrimethylammonium salt) ions, poly(vinylbenzylphosphonium salt) ions, styrene-butadiene acrylic acid copolymer ions, polyurethane ions, sulfonated styrene-2-acrylamide-2-methylpropanesulfate ions, acid-amine ions, aliphatic ionsens, and aromatic ionsens.

[0040] If the film contains compatible components, the content is preferably 0.05 to 30% by mass, more preferably 0.1 to 20% by mass, and even more preferably 0.5 to 10% by mass, relative to the total mass of the film.

[0041] <Heat stabilizer> Examples of thermal stabilizers include phenolic and amine-based stabilizers with radical scavenging activity; phosphite and sulfur-based stabilizers with peroxide decomposition activity; and hybrid stabilizers that possess both radical scavenging and peroxide decomposition activity. The film preferably contains a heat stabilizer, and more preferably contains a heat stabilizer together with the liquid crystal polymer, polyolefin, and compatible components. The inclusion of a heat stabilizer in the film suppresses thermal oxidative degradation during melt extrusion film formation, improving the surface properties and smoothness of the film surface.

[0042] Examples of phenolic stabilizers include hindered phenolic stabilizers, semi-hindered phenolic stabilizers, and less-hindered phenolic stabilizers. Examples of commercially available hindered phenol stabilizers include ADEKA AO-20, AO-50, AO-60, and AO-330; and BASF Irganox 259, 1035, and 1098. Examples of commercially available semi-hindered phenolic stabilizers include ADEKA AO-80 (manufactured by ADEKA Corporation) and Irganox 245 (manufactured by BASF Corporation). Examples of commercially available less-hindered phenolic stabilizers include Nocrack 300 manufactured by Ouchi Shinko Chemical Industry Co., Ltd., and Adeka Stab AO-30 and AO-40 manufactured by ADEKA Corporation. Examples of commercially available phosphite stabilizers include ADEKA's ADEKA Stab 2112, PEP-8, PEP-36, and HP-10. A commercially available example of a hybrid stabilizer is Sumirizer GP manufactured by Sumitomo Chemical.

[0043] The heat stabilizer may be used alone or in combination of two or more types. If the film contains a heat stabilizer, its content is preferably 0.0001 to 10% by mass, more preferably 0.001 to 5% by mass, and even more preferably 0.01 to 2% by mass, relative to the total mass of the film.

[0044] <Crosslinking agent> The crosslinking agent is a low-molecular-weight compound having two or more reactive groups. A reactive group is a functional group that can react with the phenolic hydroxyl group or carboxyl group at the end of the liquid crystal polymer. Examples of reactive groups include epoxy groups, maleic anhydride groups, oxazoline groups, isocyanate groups, and carbodiimide groups. Examples of crosslinking agents include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, phenol novolac type epoxy compounds, cresol novolac type epoxy compounds, and diisocyanate compounds. The crosslinking agent may be used alone or in combination of two or more types. The crosslinking agent content is preferably 0 to 10% by mass, and more preferably 0 to 5% by mass, relative to the total mass of the film.

[0045] <Other additives> The film may contain other additives. Other additives include plasticizers, lubricants, inorganic and organic particles, and UV absorbers.

[0046] Examples of plasticizers include alkylphthalyl alkyl glycolate compounds, bisphenol compounds (bisphenol A, bisphenol F), alkylphthalyl alkyl glycolate compounds, phosphate ester compounds, carboxylic acid ester compounds, and polyhydric alcohols. The plasticizer content may be 0 to 5% by mass relative to the total mass of the film. Examples of lubricants include fatty acid esters and metal soaps (e.g., inorganic stearate). The lubricant content may be 0 to 5% by mass relative to the total mass of the film. The film may contain inorganic particles and / or organic particles as reinforcing materials, matting agents, dielectric constants, or dielectric loss tangent modifiers. Examples of inorganic particles include silica, titanium dioxide, barium sulfate, talc, zirconia, alumina, silicon nitride, silicon carbide, calcium carbonate, silicates, glass beads, graphite, tungsten carbide, carbon black, clay, mica, carbon fibers, glass fibers, and metal powders. Examples of organic particles include cross-linked acrylic and cross-linked styrene. The content of inorganic and organic particles may be 0 to 50% by mass relative to the total mass of the film. Examples of UV absorbers include salicylate compounds, benzophenone compounds, benzotriazole compounds, substituted acrylonitrile compounds, and s-triazine compounds. The UV absorber content may be 0 to 5% by mass relative to the total mass of the film.

[0047] [Physical properties of liquid crystal polymers] [Area of ​​melting peak] The liquid crystal polymer film of the present invention is characterized in that the area of ​​the melting peak measured by DSC (hereinafter also referred to as the "melting peak area") is 0.2 J / g or more. The film of the present invention exhibits a further reduction in dielectric loss tangent because its melting peak area is above the lower limit mentioned above. For superior effects of the present invention, the melting peak area of ​​the film is preferably 0.5 J / g or more, more preferably 1.5 J / g or more, and even more preferably 2.0 J / g or more. There is no particular upper limit to the melting peak area of ​​the film, but it is preferable to use 30 J / g or less.

[0048] The melting peak area of ​​the film can be determined by calculating the area of ​​the endothermic peak appearing on the curve (DSC curve) showing the change in the endothermic and exothermic energy of the film using a differential scanning calorimeter (Shimadzu Corporation "DSC-60A"). A detailed method for calculating the melting peak area is described in the Examples section below.

[0049] The method for producing the film of the present invention, which contains a liquid crystal polymer and has a melting peak area within the above range, is not particularly limited, but examples include a method described later in which the formed film is transversely stretched and then the transversely stretched film is heated under predetermined conditions.

[0050] [Structural anisotropy] The structural anisotropy of the film can be determined by calculating the ratio of peak intensities in the in-plane direction of the film (AT / AM) from the measurement results of the X-ray diffraction intensity of the film, according to the method described below. The AT / AM ratio is preferably 1.5 or less, more preferably less than 1.2, and even more preferably less than 1.1, as this results in a film with small differences in crystal structure in the in-plane direction (structural anisotropy) and uniform electrical properties and mechanical strength across the entire film surface. The lower limit of the AT / AM ratio may be 1.0.

[0051] Method 1: X-rays are incident on the surface of the film using an X-ray diffractometer, and the peak intensity (peak height) detected in the range of 2θ = 16 to 22° is measured. The film is rotated in the in-plane direction within the range of 0 to 360° with reference to any one direction within the film's plane, and the peak intensity is measured. From the obtained measurement results, the maximum value of the peak intensity AT and the rotation angle φ at which the peak intensity is maximized are determined. T Next, we find the rotation angle φ. T The rotation angle φ is 90° different from the given value. M The peak intensity AM is determined, and the ratio of peak intensity AT to peak intensity AM (AT / AM) is calculated.

[0052] In the measurement of peak intensity described above, the direction of film rotation is such that the rotation axis (β axis) is the direction normal to the film surface. In X-ray diffraction measurement, for example, the film is rotated at 5° intervals with respect to the reference direction, and the X-ray diffraction intensity is measured at each rotation angle φ. By taking these measurements over a range of 0 to 360° with respect to the reference direction, the maximum value AT of the peak intensity can be determined from the measurement results. When performing the above measurement, the irradiation and detection units of the X-ray diffractometer may be moved relative to the film. The peak intensity AM obtained by the above method is calculated using the rotation angle φ T Two rotation angles φ with a difference of 90° M This is the average value of the peak intensity at [location]. Furthermore, if there are multiple rotation angles φ at which the peak intensity is maximized by X-ray diffraction measurement, the largest value among the ratios of the multiple peak intensities calculated using the above method is adopted as the ratio AT / AM. The method for manufacturing a film with a ratio AT / AM within the above range and low structural anisotropy is not particularly limited, but one example is a method of controlling the film's target temperature in the post-heat treatment described later.

[0053] [Dielectric properties] The film of the present invention exhibits excellent dielectric loss tangent. Specifically, the dielectric loss tangent of the film is preferably 0.0025 or less, more preferably 0.002 or less, and even more preferably 0.0015 or less. The lower limit is not particularly limited and may be 0.0001 or more. Furthermore, the dielectric constant of the film varies depending on its application, but is preferably 2.0 to 4.0, and more preferably 2.5 to 3.5. The dielectric properties of a film, including its dielectric loss tangent and relative permittivity, can be measured by the cavity resonator perturbation method. Specific methods for measuring the dielectric properties of a film are described in the Examples section below.

[0054] [Coefficient of linear expansion] The coefficient of linear expansion (CTE) in the direction along the plane of the film is preferably -5 to 50 ppm / °C, more preferably 0 to 40 ppm / °C, and even more preferably 10 to 30 ppm / °C. In particular, when the CTE in the first direction of the film plane is defined as the first coefficient of thermal expansion (CTE1) and the CTE in the second direction perpendicular to the first direction of the film plane is defined as the second coefficient of thermal expansion (CTE2), it is preferable that both CTE1 and CTE2 are within the range of 0 to 40 ppm / °C, and more preferably that both CTE1 and CTE2 are within the range of 10 to 30 ppm / °C. The first direction is the direction in which the CTE (CTE1) in that direction is the minimum CTE in the plane of the film. That is, CTE1 is the minimum value of the CTE in the plane of the film. When CTE1 and CTE2 are within the above range, the orientation anisotropy of the liquid crystal polymer can be suppressed, resulting in less warping of the film itself when heated, and also resulting in better adhesion when laminated with copper foil, as the CTE is close to that of copper foil (18 ppm / °C).

[0055] From the same viewpoint as above, the ratio of CTE2 to CTE1 (CTE ratio) is preferably 1.0 to 2.0, more preferably 1.0 to 1.5, and even more preferably 1.0 to 1.2.

[0056] Furthermore, the CTE in the film thickness direction is preferably 50 to 600 ppm / °C, more preferably 50 to 450 ppm / °C, and even more preferably 50 to 300 ppm / °C. This is because having the CTE in the film thickness direction within the above range can further suppress the breakage of the electroless copper plating layer when forming through-holes in the film and applying electroless copper plating to the walls of the through-holes to form wiring patterns.

[0057] The method for manufacturing a film in which the in-plane CTE and the CTE in the film thickness direction are within the above range is not particularly limited, but examples include adjusting the longitudinal stretching and transverse stretching, as well as the heat treatment conditions, in the film manufacturing method described later. The measurement methods for CTE, CTE1, and CTE2 within the film plane, as well as CTE in the film thickness direction, are described in the Examples section below. Note that when measuring CTE in the film thickness direction, if the film thickness was less than 50 μm, measurements were performed by stacking 2 to 6 films depending on the film thickness.

[0058] [Thickness] The film thickness is preferably 5 to 1000 μm, more preferably 10 to 500 μm, and even more preferably 20 to 300 μm.

[0059] [Surface roughness] The surface roughness Ra of the film is preferably less than 430 nm, more preferably less than 400 nm, even more preferably less than 350 nm, and particularly preferably less than 300 nm. There is no particular limit to the lower limit of the film's surface roughness Ra; for example, it can be 10 nm or more. If the surface roughness Ra of the film is within the above range, it is thought that dimensional changes occurring in the film can be easily absorbed, resulting in superior surface properties and smoothness. The method for measuring the surface roughness Ra of the film is as shown in the Examples section below.

[0060] [Dispersed phase] When the film contains polyolefin, it is preferable that the polyolefin forms a dispersed phase within the film. The dispersed phase mentioned above corresponds to the island portion in a film that forms a so-called sea-island structure. There are no restrictions on the method of forming a sea-island structure in the film and having polyolefins present as a dispersed phase. For example, a dispersed polyolefin phase can be formed by adjusting the content of liquid crystal polymer and polyolefin in the film to the above-mentioned preferred content ranges.

[0061] The average dispersion diameter of the above-mentioned dispersed phase is preferably 0.001 to 50.0 μm, more preferably 0.005 to 20.0 μm, and even more preferably 0.01 to 10.0 μm, in terms of achieving superior film smoothness. The method for measuring the average variance diameter described above will be explained in the Examples section below.

[0062] The dispersed phase is preferably flattened, and it is preferable that the flat surface of the flattened dispersed phase is substantially parallel to the film. Furthermore, in terms of reducing the anisotropy of the film, it is preferable that the flat surface of the flattened dispersed phase is approximately circular when observed from a direction perpendicular to the film surface. It is believed that when such a dispersed phase is dispersed in the film, dimensional changes occurring in the film can be absorbed, resulting in superior surface properties and smoothness.

[0063] [Manufacturing method for liquid crystal polymer film] The method for manufacturing a liquid crystal polymer film is not particularly limited, but it is preferable to include, for example, a pelletizing step of kneading the above-mentioned components to obtain pellets, and a film-forming step of using the above-mentioned pellets to obtain a liquid crystal polymer film. Each step will be described below.

[0064] [Pelletization process] (1) Raw material form While liquid crystal polymers used in film formation can be used as is in pellet, flake, or powder form, it is preferable to use pellets obtained by kneading one or more raw materials (liquid crystal polymer and at least one of the additives; the same applies hereinafter) using an extruder and then pelletizing them, for the purpose of stabilizing the film formation or ensuring uniform dispersion of additives (meaning components other than liquid crystal polymers; the same applies hereinafter). Hereinafter, polymer raw materials and mixtures containing polymers used in the manufacture of liquid crystal polymer films will also be collectively referred to as resins.

[0065] (2) Drying alternative by drying or venting When pelletizing, it is preferable to dry the liquid crystal polymer and additives beforehand. Drying methods include circulating heated air with a low dew point and dehumidification by vacuum drying. In particular, for resins that are easily oxidized, vacuum drying or drying with an inert gas is preferable. Alternatively, drying can be substituted by using a vented extruder. Vented extruders come in single-screw and twin-screw types, and both can be used. Of these, the twin-screw type is more efficient and preferable. Venting allows pelletization to be performed at a pressure of less than 1 atmosphere (preferably 0 to 0.8 atmospheres, more preferably 0 to 0.6 atmospheres) inside the extruder. This reduced pressure can be achieved by exhausting the material using a vacuum pump from a vent or hopper located in the kneading section of the extruder.

[0066] (3) Raw material supply method The raw material supply method may be a method in which the raw materials are pre-mixed and supplied before being kneaded into pellets, a method in which the raw materials are supplied separately to the extruder in a certain proportion, or a method that combines both.

[0067] (4) Types of extruders Pelletization can be performed by melting and uniformly dispersing the liquid crystal polymer and / or additives in a kneader, cooling and solidifying, and then cutting. As long as a sufficient melting and kneading effect can be obtained, known single-screw extruders, non-meshing asymmetrical twin-screw extruders, meshing asymmetrical twin-screw extruders, and meshing coaxial twin-screw extruders can be used.

[0068] (5) Atmosphere during extrusion When melt extrusion, it is preferable to prevent thermal and oxidative degradation as much as possible without hindering uniform dispersion. Reducing the oxygen concentration by using a vacuum pump to create a reduced pressure or by introducing an inert gas is also effective. These methods may be carried out individually or in combination.

[0069] (6) Rotation speed The rotational speed of the extruder is preferably 10 to 1000 rpm, more preferably 20 to 700 rpm, and even more preferably 30 to 500 rpm. If the rotational speed is above the lower limit, the residence time can be shortened, thereby suppressing a decrease in molecular weight due to thermal degradation and the significant discoloration of the resin due to thermal degradation. Also, if the rotational speed is below the upper limit, the severance of molecular chains due to shear can be suppressed, thereby suppressing a decrease in molecular weight and an increase in the generation of cross-linked gels. It is preferable to select the appropriate rotational speed from the perspective of both uniform dispersion and thermal degradation due to extended residence time.

[0070] (7)Temperature The mixing temperature is preferably below the thermal decomposition temperature of the liquid crystal polymer and additives, and is even more preferably as low as possible, within a range where the load on the extruder and the reduction in uniform mixing performance do not become a problem. However, if the temperature is too low, the melt viscosity will increase, and conversely, the shear stress during mixing will increase, which may cause molecular chain severance, so it is necessary to select an appropriate range. In addition, to achieve both improved dispersibility and reduced thermal degradation, it is also effective to melt and mix at a relatively high temperature in the first half of the extruder process and then lower the resin temperature in the second half.

[0071] (8) Pressure The mixing pressure of the resin during pelletization is preferably 0.05 to 30 MPa. In the case of resins that are prone to discoloration or gel formation due to shearing, it is preferable to apply an internal pressure of about 1 to 10 MPa to the extruder to fill the twin-screw extruder with resin raw materials. As a result, mixing can be performed more efficiently with lower shear, promoting uniform dispersion while suppressing thermal decomposition. Such pressure adjustment can be performed by adjusting the Q / N (discharge volume per screw rotation) and / or by installing a pressure regulating valve at the outlet of the twin-screw compounding extruder.

[0072] (9) Shear, screw type While it is preferable to apply shear to uniformly disperse multiple types of raw materials, applying excessive shear may cause molecular chain severance or gel formation. Therefore, it is preferable to appropriately select the number of rotor segments, kneading discs, and clearances arranged in the screw. The shearing speed in the extruder (shearing speed during pelletization) is 60-1000 sec. -1 Preferably, 100-800 seconds -1 More preferably, 200-500 seconds -1is more preferable. If the shear rate is at least the lower limit value, generation of poor melting of the raw material and generation of poor dispersion of the additive can be suppressed. If the shear rate is at most the upper limit value, breakage of molecular chains can be suppressed, and decrease in molecular weight, increase in generation of crosslinked gels, etc. can be suppressed. Further, if the shear rate during pelletization is within the above range, it becomes easy to adjust the equivalent circle diameter of the above-described island-shaped region to the above range.

[0073] (10) Residence time The kneader residence time can be calculated from the volume of the resin residence part in the kneader and the discharge capacity of the polymer. The extrusion residence time in pelletization is preferably from 10 seconds to 30 minutes, more preferably from 15 seconds to 10 minutes, and still more preferably from 30 seconds to 3 minutes. If conditions are such that sufficient melting can be ensured, resin deterioration and discoloration of the resin can be suppressed, and thus a shorter residence time is preferable.

[0074] (11) Pelletizing method [[ID=]12] As the pelletizing method, a method in which what is extruded in a noodle shape is solidified in water and then cut is common, but pelletization may be performed by an under-water cut method in which, after melting by an extruder, it is directly extruded into water from a die while cutting, or a hot cut method in which cutting is performed while in a hot state.

[0075] (12) Pellet size The pellet size preferably has a cross-sectional area of 1 to 300 mm 2 and a size with a length of 1 to 30 mm, more preferably a cross-sectional area of 2 to 100 mm 2 and a size with a length of 1.5 to 10 mm.

[0076] <Drying> (1) Purpose of drying Before melt-forming the film, it is preferable to reduce the moisture and volatile components in the pellets, and drying the pellets is effective. If moisture or volatile components are present in the pellets, it can not only cause a decrease in appearance due to the inclusion of bubbles in the film or a decrease in haze, but it can also lead to a decrease in physical properties due to molecular chain severance of the liquid crystal polymer, or roll fouling due to the generation of monomers or oligomers. In addition, depending on the type of liquid crystal polymer used, the formation of oxidized crosslinks during melt-forming may be suppressed by removing dissolved oxygen through drying.

[0077] (2) Drying method / heating method Regarding drying methods, a dehumidifying hot air dryer is generally used due to its drying efficiency and cost-effectiveness, but there are no particular restrictions as long as the desired moisture content can be achieved. Furthermore, it is also acceptable to select a more appropriate method according to the physical properties of the liquid crystal polymer. Heating methods include pressurized steam, heater heating, far-infrared irradiation, microwave heating, and heat transfer medium circulation heating. To use energy more efficiently and to minimize temperature variations for uniform drying, it is preferable to have an insulated structure for the drying equipment. While stirring can improve drying efficiency, it may generate pellet powder, so use it appropriately depending on the situation. Furthermore, there's no need to limit yourself to just one drying method; you can combine multiple methods for greater efficiency.

[0078] (3) Apparatus There are two types of drying methods: continuous and batch. For vacuum drying, the batch method is preferable, while the continuous method has the advantage of superior uniformity under steady-state conditions. The appropriate method should be chosen depending on the application.

[0079] (4) Atmosphere, airflow For a dry atmosphere, for example, a method of blowing or reducing the pressure of low-dew-point air or low-dew-point inert gas can be used. The dew point of the air is preferably 0 to -60°C, more preferably -10 to -55°C, and even more preferably -20 to -50°C. While a low-dew-point atmosphere is desirable in that it reduces the volatile content in the pellets, it is disadvantageous in terms of economy, so an appropriate range should be selected. If the raw material is damaged by oxygen, it is also effective to lower the oxygen partial pressure using an inert gas. The required airflow per ton of liquid crystal polymer is 20 to 2000 m³. 3 / The duration is preferable, 50-1000m 3 / Time is more preferable, 100-500m 3 / Time is even more preferable. If the drying airflow is above the lower limit, drying efficiency improves. If the drying airflow is below the upper limit, it is economically preferable.

[0080] (5) Temperature / time As for the drying temperature, when the raw material is in an amorphous state, {glass transition temperature (Tg)(°C) + 80°C} to {Tg(°C) - 80°C} is preferred, {Tg(°C) + 40°C} to {Tg(°C) - 40°C} is more preferred, and {Tg(°C) + 20} to {Tg(°C) - 20°C} is even more preferred. If the drying temperature is below the upper limit, blocking due to resin softening can be suppressed, resulting in excellent transportability. On the other hand, if the drying temperature is above the lower limit, drying efficiency can be improved, and the moisture content can be set to the desired value. Furthermore, in the case of crystalline resins, drying is possible without melting if the temperature is below {melting point (Tm) (°C) - 30°C}. If the temperature is too high, discoloration and / or changes in molecular weight (generally decreasing, but in some cases increasing) may occur. Also, if the temperature is too low, the drying efficiency will be low, so it is necessary to select appropriate conditions. As a guideline, {Tm (°C) - 250°C} to {Tm (°C) - 50°C} is preferable. The drying time is preferably 15 minutes or more, more preferably 1 hour or more, and even more preferably 2 hours or more. However, drying for more than 50 hours does not further reduce the moisture content and raises concerns about thermal degradation of the resin, so it is not necessary to unnecessarily extend the drying time.

[0081] (6) Moisture content The moisture content of the pellets is preferably 1.0% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less.

[0082] (7) Transportation method To prevent re-adsorption of moisture to the dried pellets, it is preferable to transport the pellets using dry air or nitrogen. Furthermore, supplying high-temperature pellets at a constant temperature to the extruder is effective for stabilizing the extrusion process, and it is common practice to use heated dry air to maintain the heated state.

[0083] [Film forming process] <Manufacturing equipment> The following describes an example of each piece of equipment that makes up the manufacturing apparatus.

[0084] (Extruder, screw, barrel) (1) Extruder structure The raw material (pellets) is supplied into the cylinder via the extruder's feed port. Inside the cylinder, starting from the feed port, there is a supply section that quantitatively transports the supplied raw material, a compression section that melts, kneads, and compresses the raw material, and a metering section that weighs the melted, kneaded, and compressed raw material. Multiple divided heating and cooling devices are provided around the outer circumference of the cylinder, allowing each zone inside the cylinder to be controlled to a desired temperature. Cylinder heating is usually done using band heaters or sheathed wire aluminum cast heaters, but a heat transfer medium circulation heating method can also be used. Cooling is generally done by air cooling with a blower, but there is also a method of circulating water or oil through pipes wrapped around the outer circumference of the cylinder. Furthermore, it is preferable to cool the supply port to prevent the pellets from overheating and fusing together, and to prevent heat transfer in order to protect the screw drive equipment. The inner wall surface of the cylinder must be made of a material that has excellent heat resistance, wear resistance, and corrosion resistance, and that can ensure sufficient friction with the resin. Generally, nitrided steel with a nitrided inner surface is used, but chromium-molybdenum steel, nickel-chromium-molybdenum steel, or stainless steel that has been nitrided can also be used. In applications requiring particularly high wear resistance and / or corrosion resistance, it is effective to use bimetallic cylinders in which corrosion-resistant and wear-resistant alloys such as nickel, cobalt, chromium, or tungsten are lined on the inner wall surface of the cylinder by centrifugal casting, and to form a ceramic thermal spray coating. Furthermore, while cylinders typically have a smooth inner surface, they may have axial grooves (square grooves, semicircular grooves, helical grooves, etc.) on the inner wall to increase the extrusion rate. However, grooves in the cylinder can cause polymer buildup inside the extruder, so caution is required when using them in applications with strict foreign matter levels.

[0085] (2) Types of extruders Extruders are generally classified into single-screw and twin-screw types, with single-screw extruders being more widely used. Twin-screw (multi-screw) screws are broadly classified into meshing and non-meshing types, and their rotation directions are further divided into same-direction and opposite-direction. Meshing screws are more commonly used because they have a greater mixing effect than non-meshing screws. Also, opposite-direction rotating screws have a higher mixing effect than same-direction rotating screws, but same-direction rotating screws have a self-cleaning effect, making them effective in preventing stagnation within the extruder. Furthermore, the axial direction can be parallel or oblique, and there is also a conical type shape used when strong shear is required. Twin-screw extruders are widely used because, by properly positioning the vents, undried raw materials (pellets, powders, or flakes, etc.) and film edges produced during film formation can be used directly. However, in the case of single-screw extruders, it is also possible to remove volatile components by properly positioning the vents. When selecting an extruder for film formation, it is important to consider the required extrusion performance (extrusion stability, kneading ability, retention prevention, and thermal history) and the characteristics of the extruder itself. Extruders are generally used individually as single-screw or twin-screw (multi-screw) types, but it is also common to use them in combination, taking advantage of their respective characteristics. For example, a combination of a twin-screw extruder that can handle undried raw materials and a single-screw extruder with good metering capabilities is widely used in the production of PET (polyester) resin films.

[0086] (3) Types and structure of screws Here, we show examples of screws for single-screw extruders. The most commonly used screw shape is the full-flight screw, which has one helical flight with equal pitch. Double-flight screws, which stabilize extrusion by separating the solid and liquid phases of the resin during the melting process using two flights, are also frequently used. Furthermore, it is common to combine mixing elements such as madocks, dalmages, and barriers to improve mixing efficiency within the extruder. In addition, screws with polygonal cross-sections are used to enhance the mixing effect, or screws with distribution holes to reduce temperature variations within the extruder are also used. Similar to cylinders, the material used for screws must be excellent in heat resistance, wear resistance, and corrosion resistance, and must be able to ensure sufficient friction with the resin. Commonly used materials include nitrided steel, chromium-molybdenum steel, nickel-chromium-molybdenum steel, and stainless steel. Generally, screws are manufactured by grinding the above-mentioned steel materials and then performing nitriding treatment and / or plating treatment such as HCr. However, special surface treatments such as TiN, CrN, or Ti coating by PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition) may also be applied to the screw surface.

[0087] • Diameter, groove depth The preferred screw diameter varies depending on the target extrusion rate per unit time, but is preferably 10 to 300 mm, more preferably 20 to 250 mm, and even more preferably 30 to 150 mm. The groove depth of the screw feed section is preferably 0.05 to 0.20 times the screw diameter, more preferably 0.07 to 0.18 times, and even more preferably 0.08 to 0.17 times. The flight pitch is generally the same as the screw diameter, but shorter flight pitches are used to improve melt uniformity, or conversely, longer flight pitches are used to increase the extrusion rate. The flight groove width is preferably 0.05 to 0.25 times the screw flight pitch, and is generally about 0.1 in terms of friction between the screw and barrel and reduction of stagnation. The clearance between the flight and barrel is also usually 0.001 to 0.005 times the screw diameter, but is preferably 0.0015 to 0.004 times in terms of friction between barrels and reduction of stagnation.

[0088] • Compression ratio Furthermore, the screw compression ratio of the extruder is preferably 1.6 to 4.5. Here, the screw compression ratio is expressed as the volume ratio of the supply section to the metering section, i.e., (volume per unit length of the supply section) ÷ (volume per unit length of the metering section), and is calculated using the outer diameter of the screw shaft of the supply section, the outer diameter of the screw shaft of the metering section, the groove diameter of the supply section, and the groove diameter of the metering section. If the screw compression ratio is 1.6 or higher, sufficient melt-kneading properties can be obtained, the generation of undissolved portions can be suppressed, undissolved foreign matter is less likely to remain in the manufactured film, and the incorporation of air bubbles can be suppressed by the defoaming effect. Conversely, if the screw compression ratio is 4.5 or lower, excessive shear stress can be suppressed. Specifically, a decrease in the mechanical strength of the film due to molecular chain severance, an overheating discoloration phenomenon due to shear heat generation, and a decrease in the foreign matter level due to gel generation can be suppressed. Therefore, an appropriate screw compression ratio is preferably 1.6 to 4.5, more preferably 1.7 to 4.2, and even more preferably 1.8 to 4.0.

[0089] L / D L / D is the ratio of cylinder length to cylinder bore diameter. If L / D is 20 or higher, melting and mixing are sufficient, and the generation of undissolved foreign matter in the manufactured film can be suppressed, similar to when the compression ratio is appropriate. If L / D is 70 or lower, the residence time of the liquid crystal polymer in the extruder is shortened, which suppresses resin degradation. Furthermore, shortening the residence time suppresses the decrease in mechanical strength of the film caused by a decrease in molecular weight due to molecular chain severance. Therefore, an L / D range of 20 to 70 is preferred, 22 to 65 is more preferred, and 24 to 50 is even more preferred.

[0090] • Screw proportion The length of the extruder supply section is preferably 20-60% of the effective screw length (total length of the supply section, compression section, and metering section), and more preferably 30-50%. The length of the extruder compression section is preferably 5-50% of the effective screw length, more preferably 5-40% if the material to be mixed is a crystalline resin, and more preferably 10-50% if the material to be mixed is an amorphous resin. The length of the metering section is preferably 20-60% of the effective screw length, and more preferably 30-50%. It is also common practice to divide the metering section into multiple sections and place mixing elements between them to improve mixing efficiency.

[0091] Q / N The extruder discharge rate (Q / N) is equal to the theoretical maximum discharge rate (Q / N). MAX A value of 50-99% is preferred, 60-95% is more preferred, and 70-90% is even more preferred. Note that Q is the discharge volume [cm³]. 3 [ / min], N indicates the screw rotation speed [rpm], and (Q / N) indicates the discharge rate per screw rotation. Discharge rate (Q / N) = Theoretical maximum discharge rate (Q / N) MAX If the ratio is 50% or more, the residence time in the extruder can be shortened, and the progression of thermal degradation inside the extruder can be suppressed. Furthermore, if the ratio is 99% or less, the back pressure is sufficient, which improves kneading performance and melt uniformity, as well as providing good stability to the extrusion pressure. It is preferable to select the optimal screw dimension for such a process, taking into consideration the crystallinity, melt viscoelastic properties, and thermal stability of the resin, as well as the extrusion stability and uniformity of melt plasticization.

[0092] (4) Extrusion conditions ·Raw material drying In the extruder-based melt-plasticization process of pellets, it is preferable to reduce moisture and volatile components, similar to the pelletization process, and drying the pellets is effective.

[0093] ·Raw material supply method If there are multiple types of raw materials (pellets) fed into the extruder's feed port, they may be pre-mixed (premix method), supplied separately to the extruder in a fixed proportion, or a combination of both methods may be used. In addition, to stabilize the extrusion, it is common practice to minimize fluctuations in the temperature and bulk density of the raw materials fed into the feed port. Furthermore, in terms of plasticization efficiency, the raw material temperature is preferably high, as long as the raw material does not stick and block the feed port. If the raw material is in an amorphous state, it is more preferable to heat or maintain the temperature in the range of {glass transition temperature (Tg) (°C) - 150°C} to {Tg (°C) - 1°C}, and if the raw material is a crystalline resin, it is more preferable to heat or maintain the temperature in the range of {melting point (Tm) (°C) - 150°C} to {Tm (°C) - 1°C}. Furthermore, in terms of plasticization efficiency, the bulk density of the raw material is preferably 0.3 times or more than that of the molten state, and more preferably 0.4 times or more. If the bulk density of the raw material is less than 0.3 times the density of the molten material, it is preferable to perform processing such as compressing the raw material to form pseudo-pellets.

[0094] • Atmosphere during extrusion The atmosphere during melt extrusion, similar to the pelletizing process, must prevent heat and oxidative degradation as much as possible without hindering uniform dispersion. Effective methods include injecting an inert gas (such as nitrogen), lowering the oxygen concentration in the extruder using a vacuum hopper, and providing a vent in the extruder to reduce pressure using a vacuum pump. These pressure reduction and inert gas injection methods can be implemented independently or in combination.

[0095] • Rotation speed The rotational speed of the extruder is preferably 5 to 300 rpm, more preferably 10 to 200 rpm, and even more preferably 15 to 100 rpm. If the rotational speed is above the lower limit, the residence time is shortened, which suppresses the decrease in molecular weight due to thermal degradation and suppresses discoloration. If the rotational speed is below the upper limit, the cleavage of molecular chains due to shear can be suppressed, which suppresses the decrease in molecular weight and the increase in cross-linked gel. It is preferable to select the appropriate rotational speed from the perspective of both uniform dispersion and thermal degradation due to extended residence time.

[0096] ·temperature Barrel temperature (supply unit temperature T1℃) 、 The compression section temperature (T2°C) and the metering section temperature (T3°C) are generally determined by the following method. When pellets are melted and plasticized at a target temperature T°C using an extruder, the metering section temperature T3 is set to T±20°C, taking into account the shear heat generation. At this time, T2 is set within the range of T3±20°C, taking into account extrusion stability and the thermal decomposition properties of the resin. T1 is generally set to {T2(°C)-5°C} to {T2(°C)-150°C}, and the optimal value is selected in terms of ensuring friction between the resin and the barrel, which is the driving force (feed force) for sending the resin, and balancing this with preheating in the feed section. In the case of a normal extruder, it is possible to subdivide each zone from T1 to T3 and set the temperature, and by setting it so that the temperature change between each zone is gradual, it is possible to make it more stable. In this case, it is preferable that T be below the thermal degradation temperature of the resin, and if it exceeds the thermal degradation temperature due to the shear heat generation of the extruder, it is common practice to actively cool and remove the shear heat generation. Furthermore, to achieve both improved dispersibility and reduced thermal degradation, a condition in which the resin is melted and mixed at a relatively high temperature in the first half of the extruder, and then the resin temperature is lowered in the second half, is also effective.

[0097] • Screw temperature control To stabilize the extrusion process, the screw temperature is also controlled. Common methods of temperature control include circulating water or a medium inside the screw, and in some cases, a heater is built into the screw for heating. Temperature control is typically applied to the screw's feed section, but may also be applied to the compression or metering sections, with different temperatures being controlled in each zone.

[0098] ·pressure The resin pressure inside the extruder is typically 1 to 50 MPa, but 2 to 30 MPa is preferable in terms of extrusion stability and melt uniformity, and 3 to 20 MPa is more preferable. If the pressure inside the extruder is 1 MPa or higher, the melt filling rate inside the extruder is sufficient, so the instability of the extrusion pressure and the generation of foreign matter due to stagnation can be suppressed. Also, if the pressure inside the extruder is 50 MPa or lower, excessive shear stress inside the extruder can be suppressed, so thermal decomposition due to rise in resin temperature can be suppressed.

[0099] • Duration of stay The residence time in the extruder (residence time during film formation) can be calculated from the volume of the extruder section and the polymer discharge capacity, similar to the pelletization process. A residence time of 10 seconds to 60 minutes is preferable, 15 seconds to 45 minutes is more preferable, and 30 seconds to 30 minutes is even more preferable. A residence time of 10 seconds or more ensures sufficient melt plasticization and additive dispersion. A residence time of 30 minutes or less is preferable because it suppresses resin degradation and discoloration.

[0100] (filtration) ·Type, installation purpose, structure To prevent damage to the gear pump from foreign matter contained in the raw material, and to extend the lifespan of the fine-pore filter installed downstream of the extruder, it is common practice to install a filtration system at the extruder outlet. It is preferable to use a so-called breaker plate type filtration system, which uses a mesh filter material in combination with a strong reinforcing plate with a high opening ratio.

[0101] • Mesh size, filtration area The mesh size is preferably 40 to 800 mesh, more preferably 60 to 700 mesh, and even more preferably 100 to 600 mesh. If the mesh size is 40 mesh or larger, foreign matter can be sufficiently suppressed from passing through the mesh. If the mesh size is 800 mesh or smaller, the rate of increase in filtration pressure can be suppressed, and the frequency of mesh replacement can be reduced. In addition, in terms of filtration accuracy and strength, it is common to use multiple types of filter mesh with different mesh sizes layered together. Furthermore, it is also common to reinforce the filter mesh with a breaker plate, as this allows for a larger filtration opening area and maintains the strength of the mesh. In terms of filtration efficiency and strength, the opening ratio of the breaker plate used is generally 30 to 80%. Furthermore, while screen changers are often the same diameter as the extruder barrel, tapered piping is commonly used to increase the filtration area, allowing for larger diameter filter meshes or branching the flow path to use multiple breaker plates. The filtration area is based on a flow rate of 0.05 to 5 g / cm³ per second. 2 It is preferable to select based on the following guideline: 0.1-3 g / cm³ 2 More preferably, 0.2-2 g / cm³ 2 That is even more preferable. When foreign matter is captured, the filter becomes clogged and the filtration pressure increases. In this case, the extruder must be stopped and the filter replaced, but types that allow filter replacement while extrusion continues can also be used. Furthermore, as a countermeasure against the increase in filtration pressure due to foreign matter capture, some types can be used that have a function to reduce the filtration pressure by washing away the foreign matter captured in the filter by reversing the polymer flow path.

[0102] (precision filtration) ·Type, installation purpose, structure To achieve even higher precision filtration of foreign matter, it is preferable to install a high-precision filtration device before extrusion from the die. While a high filtration accuracy of the filter media is preferable, considering the pressure resistance of the filter media and the suppression of pressure rise due to clogging of the filter media, a filtration accuracy of 3 to 30 μm is preferable, 3 to 20 μm is more preferable, and 3 to 10 μm is even more preferable. Although a single precision filtration device is usually installed, multi-stage filtration may be performed by installing multiple devices in series and / or parallel. For the filter used, it is preferable to install a filtration device incorporating a leaf-type disc filter because it allows for a large filtration area and has high pressure resistance. The number of leaf-type disc filters loaded can be adjusted to ensure appropriate pressure resistance and filter life. The required filtration area varies depending on the melt viscosity of the resin being filtered, but is generally between 5 and 100 g / cm². -2 ·h -1 Preferably, 10-75 g·cm -2 ·h -1 More preferably, 15-50g·cm -2 ·h -1 This is even more preferable. Increasing the filtration area is advantageous in terms of increasing filtration pressure, but it also increases the residence time inside the filter, which can cause deterioration and the generation of foreign matter, so it is necessary to select appropriate conditions. Regarding the type of filter material, it is preferable to use a steel material because it is used under high temperature and high pressure, and among steel materials, it is more preferable to use stainless steel or steel, and it is even more preferable to use stainless steel because it is resistant to corrosion. In addition to woven wires, sintered filter media, such as those formed by sintering long metal fibers or metal powders, are also used. While filters made of wires of a single diameter are common, to improve filter life or filtration accuracy, filters may be constructed by laminating wires with different diameters in the thickness direction of the filter, or by using filter media with continuously changing wire diameters. Furthermore, while a thicker filter is preferable in terms of filtration accuracy, a thinner filter is preferable in terms of reducing filtration pressure. Therefore, within the range where both conditions can be met, the filter thickness is preferably 200 μm to 3 mm, more preferably 300 μm to 2 mm, and even more preferably 400 μm to 1.5 mm. The filter porosity is preferably 50% or higher, and more preferably 70% or higher. If it is 50% or higher, the pressure loss is low and clogging is reduced, allowing for long-term operation. The filter porosity is preferably 90% or lower. If it is 90% or lower, the crushing of the filter media when the filtration pressure rises can be suppressed, thus suppressing the rise in filtration pressure. The filtration accuracy, wire diameter, porosity, and thickness of the filter media are preferably selected appropriately based on the melt viscosity and filtration flow rate of the material to be filtered.

[0103] (Connection piping, etc.) The piping connecting the various parts of the film-forming apparatus (adapter piping, switching valves, and mixing equipment, etc.) must also have excellent corrosion resistance and heat resistance, similar to the extruder barrel and screw. Typically, chromium-molybdenum steel, nickel-chromium-molybdenum steel, or stainless steel are used. Furthermore, to improve corrosion resistance, the polymer flow channel surfaces are plated with HCr or Ni. Furthermore, in order to prevent stagnation inside the pipe, the surface roughness Ra inside the pipe is preferably 200 nm or less, and more preferably 150 nm or less. Furthermore, while a larger pipe diameter is preferable in terms of reducing pressure loss, it can also lead to stagnation due to a decrease in flow velocity in the pipe. Therefore, it is necessary to select an appropriate pipe diameter, typically between 5 and 200 kg·cm. -2 ·h -1 Preferably, 10-150 kg·cm -2 ·h -1 More preferably, 15-100 kg·cm -2 ·h -1 That is even more preferable.

[0104] To stabilize the extrusion pressure of liquid crystal polymers, which have a high temperature dependence of melt viscosity, it is preferable to minimize temperature fluctuations in the piping section. Generally, inexpensive band heaters are often used to heat the piping, but aluminum cast heaters or methods using heat transfer fluid circulation, which have small temperature fluctuations, are more preferable. Furthermore, dividing the piping into multiple sections, similar to the cylinder barrel, and controlling each zone individually is preferable in order to reduce temperature unevenness. PID control (Proportional-Integral-Differential Controller) is generally used for temperature control. It is also preferable to combine this with a method of variably controlling the heater output using an AC power regulator.

[0105] Furthermore, installing a mixing device within the extruder's flow path to homogenize the raw material temperature and composition is also effective in achieving film homogenization. Examples of mixing devices include spiral-type or stator-type static mixers and dynamic mixers. For homogenizing high-viscosity polymers, a spiral-type static mixer is effective. By using an n-stage static mixer, the polymer is divided and homogenized into 2n sections, and the larger n is, the more homogenization is promoted. On the other hand, there are issues such as pressure loss or the formation of stagnant areas, so selection must be made according to the required level of homogenization. For film homogenization, 5 to 20 stages are preferable, and 7 to 15 stages are more preferable. It is preferable to immediately extrude the polymer from the die to form a film after homogenization by the static mixer. Furthermore, a bleed valve is sometimes installed in the extruder's flow path to discharge deteriorated polymers from the extruder, preventing them from passing through the filter and die. However, because the switching section can become stagnant and cause foreign matter to be generated, the switching valve requires extremely high precision in its manufacturing.

[0106] (Gear pump) To improve thickness accuracy, it is preferable to reduce fluctuations in the discharge volume. By installing a gear pump between the extruder and the die and supplying a constant amount of resin from the gear pump, thickness accuracy can be improved. A gear pump consists of a pair of gears, a drive gear and a driven gear, housed in a meshed state. By driving the drive gear to mesh and rotate both gears, molten resin is drawn into the cavity through a suction port formed in the housing, and a constant amount of the resin is discharged through a discharge port also formed in the housing. Even if the resin pressure at the tip of the extruder fluctuates slightly, the gear pump absorbs the fluctuation, making the fluctuation of resin pressure downstream of the film-forming apparatus very small and improving thickness accuracy. By using a gear pump, it is possible to reduce the pressure fluctuation on the secondary side of the gear pump to less than 1 / 5 of the primary side, and the resin pressure fluctuation range can be reduced to within ±1%. Other advantages include the ability to filter the resin without increasing the pressure at the screw tip, thus preventing resin temperature rise, improving transport efficiency, and shortening the residence time in the extruder. Furthermore, it prevents fluctuations in the amount of resin supplied from the screw over time due to an increase in the filter's filtration pressure.

[0107] Type, Size Typically, a two-gear type is used, where quantification is performed by the meshing rotation of two gears. Furthermore, if pulsation caused by the gears is a problem, a three-gear type is commonly used to reduce the pulsation by allowing the gears to interfere with each other. The size of the gear pump used is generally selected to have a capacity that results in a rotational speed of 5-50 rpm under extrusion conditions, with 7-45 rpm being preferable and 8-40 rpm being more preferable. By selecting a gear pump size that allows the rotation speed to fall within the above range, it is possible to suppress the rise in resin temperature due to shear heat generation and to suppress resin degradation due to stagnation inside the gear pump. Furthermore, since gear pumps are constantly subjected to wear due to the meshing of gears, it is necessary to use materials with excellent wear resistance, and it is preferable to use wear-resistant materials similar to those used for the screw or barrel.

[0108] • Measures to address congestion Poor flow of polymer circulating in the gear pump bearings can lead to poor polymer sealing between the drive unit and bearings, potentially causing large fluctuations in metering and liquid extrusion pressure. Therefore, it is necessary to design the gear pump (especially the clearance) to match the melt viscosity of the liquid crystal polymer. In some cases, stagnant areas in the gear pump can cause degradation of the liquid crystal polymer, so a structure with as little stagnation as possible is preferable. Another method is to discharge the stagnant polymer from the bearing area outside the gear pump to prevent it from being mixed into the film. Furthermore, if the shear heat generated in the gear pump is large and the resin temperature rises, cooling the gear pump by air cooling and / or circulating a cooling medium is also effective.

[0109] Driving conditions If the difference between the primary pressure (inlet pressure) and secondary pressure (outlet pressure) of a gear pump is too large, the load on the gear pump increases, leading to increased shear heat generation. Therefore, the differential pressure during operation is preferably within 20 MPa, more preferably within 15 MPa, and even more preferably within 10 MPa. In addition, to ensure uniform film thickness, it is effective to control the screw rotation of the extruder or to use a pressure regulating valve to keep the primary pressure of the gear pump constant.

[0110] (Thailand) • Type, structure, material After removing impurities through filtration and further equalizing the temperature of the molten resin by a mixer, it is continuously fed to the die. Any of the commonly used T-dies, fishtail dies, and hanger coat dies can be used as long as they are designed to minimize molten resin retention. Among these, the hanger coat die is preferred due to its uniform thickness and minimal retention. The clearance at the T-die exit is preferably 1 to 20 times the film thickness, more preferably 1.5 to 15 times, and even more preferably 2.0 to 10 times. If the lip clearance is 1 time or more the film thickness, the increase in internal die pressure can be suppressed, making it easier to control the film thickness and resulting in a sheet with good planar shape. Also, if the lip clearance is 20 times or less the film thickness, the draft ratio can be prevented from becoming too large, resulting in good thickness accuracy of the sheet. Film thickness is typically adjusted by adjusting the clearance of the die tip, and using a flexible lip is preferable for thickness accuracy. In some cases, a chalk bar may also be used for thickness adjustment.

[0111] The clearance of the die can be adjusted using the adjustment bolts at the die exit. The adjustment bolts are preferably spaced 15 to 50 mm apart, more preferably 15 to 35 mm apart, and even more preferably 15 to 25 mm apart. If the spacing is 50 mm or less, the occurrence of thickness variations between the adjustment bolts can be suppressed. If the spacing is 15 mm or more, the rigidity of the adjustment bolts is sufficient, so fluctuations in the internal pressure of the die can be suppressed, and fluctuations in film thickness can be suppressed. Furthermore, the inner wall surface of the die is preferably smooth in terms of wall surface retention, and surface smoothness can be improved by polishing, for example. In some cases, the inner wall surface may be plated and then polished to improve smoothness, or vapor deposition may be performed to improve peelability from the polymer.

[0112] Furthermore, it is preferable that the flow velocity of the polymer exiting the die be uniform in the width direction of the die. Therefore, it is preferable to change the manifold shape of the die used depending on the dependence of the melt viscosity of the liquid crystal polymer used on the shear rate. Furthermore, it is preferable that the temperature of the polymer discharged from the die is uniform across the width direction. Therefore, it is preferable to achieve uniformity by raising the set temperature at the die ends where heat dissipation is large, or by taking measures such as suppressing heat dissipation at the die ends. Furthermore, die streaks can occur due to insufficient die processing accuracy or the adhesion of foreign matter to the die exit portion, leading to a significant deterioration in film quality. Therefore, the die lip portion is preferably smooth, and its surface roughness Ra is preferably 0.05 μm or less, more preferably 0.03 μm or less, and even more preferably 0.02 μm or less. In addition, the radius of curvature R of the die lip edge portion is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less. Furthermore, die lip edges processed to have a sharp edge of R=20 μm or less by thermal spraying ceramic can also be used.

[0113] To reduce thickness fluctuations in long-term continuous production, an automatic thickness adjustment die is also effective. This die measures the thickness of the downstream film, calculates the thickness deviation, and feeds the result back into adjusting the die's thickness. The gap between the die and the polymer roll landing point is called the air gap. A shorter air gap is preferable for improving thickness accuracy and stabilizing film formation by reducing neck-in (increased edge thickness due to reduced film width). It is possible to shorten the air gap by making the angle of the die tip acute or by reducing the die thickness, but on the other hand, the rigidity of the die decreases, and the pressure of the resin may cause the central part of the die to open up, which can actually reduce thickness accuracy. Therefore, it is preferable to select conditions that allow for both die rigidity and a shorter air gap.

[0114] ·Multilayer film formation For film manufacturing, inexpensive single-layer film manufacturing equipment is generally used. Alternatively, multilayer film manufacturing equipment may be used to provide functional layers such as surface protection layers, adhesive layers, easy-adhesion layers, and / or antistatic layers on the outer layer. Specifically, this can be achieved using a multilayer feed block or a multi-manifold die. Generally, it is preferable to thinly laminate the functional layer on the surface, but there are no particular restrictions on the layer ratio. The residence time (residence time from passing through the extruder to die discharge) of the pellets from the feed port into the extruder until they exit the feed means (e.g., die) is preferably 1 to 30 minutes, more preferably 2 to 20 minutes, and even more preferably 3 to 10 minutes. In terms of preventing thermal degradation of the polymer, it is preferable to select equipment with a short residence time. However, if the volume of the filtration filter is reduced too much in order to reduce the volume inside the extruder, for example, the filter life may be shortened and the frequency of replacement may increase. Also, reducing the pipe diameter too much may increase pressure loss. For these reasons, it is preferable to select equipment of an appropriate size. Furthermore, by limiting the residence time to within 30 minutes, it becomes easier to adjust the maximum circular equivalent diameter of the bright area to the range described above.

[0115] (cast) The film-forming process preferably includes the steps of supplying molten liquid crystal polymer from a supply means and landing the molten liquid crystal polymer on a cast roll to form a film. This can be cooled and solidified and then wound up as a film, or it can be passed between a pair of clamping surfaces and continuously clamped to form a film. In this case, there are no particular restrictions on the means of supplying the molten liquid crystal polymer (melt). For example, the specific means of supplying the melt may be an extruder that melts the liquid crystal polymer and extrudes it into a film, or an extruder and die may be used, or the liquid crystal polymer may be solidified once into a film, then melted by a heating means to form a melt, which is then supplied to the film-making process. When molten resin extruded from a die into a sheet is compressed by a device having a pair of compression surfaces, it is possible not only to transfer the surface morphology of the compression surfaces to the film, but also to control the orientation by applying stretch deformation to the composition containing the liquid crystal polymer.

[0116] ·Film forming method and type Among methods for forming a film from molten raw materials, it is preferable to pass the molten material between two rolls (e.g., a touch roll and a chill roll) because it allows for high clamping force and results in a superior film surface. In this specification, when there are multiple cast rolls for conveying the molten material, the cast roll closest to the upstream liquid crystal polymer supply means (e.g., a die) is referred to as the chill roll. Other methods that can be used include clamping with metal belts, or a combination of rolls and metal belts. In some cases, to improve adhesion with the rolls or metal belts, film formation methods such as electrostatic application, air knife method, air chamber method, and vacuum nozzle method can be combined and used on the cast drum. Furthermore, when obtaining a multilayer film, it is preferable to obtain it by pressing a molten polymer extruded in multiple layers from a die, but it is also possible to obtain a multilayer film by introducing a single-layer film into the pressing section in the manner of molten lamination. In addition, by changing the peripheral speed difference or orientation axis direction of the pressing section at this time, films with different gradient structures in the thickness direction can be obtained, and by repeating this process several times, it is possible to obtain a film with three or more layers. Furthermore, deformation may be applied during clamping by periodically vibrating the touch roll in the TD direction.

[0117] • Types and materials of rolls For cast rolls, a rigid metal roll is preferred in terms of surface roughness, uniformity of clamping force during clamping, and uniformity of roll temperature. "Rigidity" is not determined solely by the material of the clamping surface, but is determined by considering the ratio of the thickness of the rigid material used for the surface portion to the thickness of the structure supporting the surface portion. For example, if the surface portion is driven by a cylindrical support roll, this means that the ratio of the thickness of the outer cylinder of the rigid material to the diameter of the support roll is, for example, about 1 / 80 or more. The materials commonly used for rigid metal rolls are carbon steel and stainless steel. Other materials such as chromium-molybdenum steel, nickel-chromium-molybdenum steel, and cast iron can also be used. In addition, to modify surface properties such as film release properties, plating with chromium or nickel, or processing such as ceramic spraying may be performed. When using a metal belt, the belt thickness is preferably 0.5 mm or more, more preferably 1 mm or more, and even more preferably 2 mm or more, in order to apply the required clamping force. Furthermore, when using rubber rolls, or rolls that combine rubber rolls and metal sleeves, the hardness of the rolls is low and the length of the clamping section is long, so even if high linear pressure is applied between the rolls, the effective clamping force may not be high. For this reason, in order to apply the required clamping force, it is preferable to use rubber with extremely high hardness, specifically, the rubber hardness is preferably 80° or higher, and more preferably 90° or higher. However, with rubber rolls and metal rolls lined with rubber, the smoothness of the film may be reduced due to the large irregularities on the rubber surface. The roll nip length suitable for applying clamping force with a pair of rolls is preferably greater than 0 mm and within 5 m, and more preferably greater than 0 mm and within 3 mm.

[0118] • Roll diameter It is preferable to use a roll with a large diameter as the casting roll, specifically a diameter of 200 to 1500 mm. Using a roll with a large diameter is preferable because it reduces the deflection of the roll, allowing for the uniform application of high clamping force during clamping. Furthermore, in the manufacturing method of the present invention, the diameters of the two rolls used for clamping may be equal or different.

[0119] Roll hardness To apply the above-mentioned inter-roll pressure, the Shore hardness of the rolls is preferably 45HS or higher, more preferably 50HS or higher, and even more preferably 60 to 90HS. The Shore hardness can be determined from the average value of measurements taken at 5 points in the roll width direction and 5 points in the circumferential direction using the method of JIS Z 2246.

[0120] • Surface roughness, cylindricity, roundness, diameter runout The surface of the cast roll and / or touch roll preferably has an arithmetic mean surface roughness Ra of 100 nm or less, more preferably 50 nm or less, and even more preferably 25 nm or less. The roundness is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. The cylindricity is preferably 5 μm or less, more preferably 3 μm, and even more preferably 2 μm or less. The diameter runout is preferably 7 μm or less, more preferably 4 μm, and even more preferably 3 μm or less. Cylindricity, roundness, and diameter runout can be determined by the method of JIS B 0621.

[0121] • Roll surface properties Cast rolls and touch rolls preferably have a mirror-like surface, and generally, rolls with a hard chrome-plated surface that has been mirror-finished are used. It is also preferable to use rolls with nickel plating laminated on a hard chrome-plated base to prevent corrosion, or to use amorphous chrome plating to reduce adhesion to the roll. Furthermore, surface treatments such as titanium nitride (TiN), chromium nitride (CrN), DLC (Diamond-Like Carbon) treatment, and Al, Ni, W, Cr, Co, Zr, or Ti-based ceramic thermal spraying can be performed to improve wear resistance and film adhesion to the roll. While the roll surface is preferably smooth in terms of the film's smoothness after film formation, a mirror pocket surface roll can be used to create surface irregularities to impart slipperiness to the film, or a blast-treated or dimpled roll can be used to create fine irregularities on the film surface. However, in terms of film smoothness, the roll's surface roughness Ra is preferably 10 μm or less. Furthermore, fine grooves or prism shapes with a depth of 0.1 to 10 μm can be made on the roll surface at a depth of 1 mm. 2 It is also possible to use rolls with 50 to 1000 engraved designs per roll.

[0122] Roll temperature It is preferable that the roll quickly removes heat supplied from the molten polymer and maintains a constant roll surface temperature. Therefore, it is preferable to pass a medium at a constant temperature through the inside of the roll. As the medium, water or a heat transfer oil, or possibly a gas, is used, and it is preferable to select a medium flow rate and medium viscosity that allow for sufficient heat exchange. Furthermore, while known methods can be used to maintain a constant roll surface temperature, a roll with a spiral flow path along its circumference is preferred. Heat pipes can also be used to ensure uniform temperature of the roll.

[0123] • Melt polymer temperature The discharge temperature (resin temperature at the outlet of the supply means) is preferably (Tm-10 of the liquid crystal polymer)°C to (Tm+40 of the liquid crystal polymer)°C, in terms of improving the moldability of the liquid crystal polymer and suppressing its degradation. The melt viscosity is preferably 50 to 3500 Pa·s. It is preferable to minimize the cooling of the molten polymer between the air gaps, and it is preferable to reduce the temperature drop due to cooling by taking measures such as increasing the film formation rate and shortening the air gap.

[0124] • Touch roll temperature It is preferable to set the touch roll temperature to be below the Tg of the liquid crystal polymer. If the touch roll temperature is below the Tg of the liquid crystal polymer, adhesion of the molten polymer to the roll can be suppressed, resulting in a better film appearance. For the same reason, it is also preferable to set the chill roll temperature below the Tg of the liquid crystal polymer.

[0125] · Film forming speed, peripheral speed difference In terms of maintaining the melt's temperature in the air gap, the film formation rate is preferably 3 m / min or higher, more preferably 5 m / min or higher, and even more preferably 7 m / min or higher. A faster line speed suppresses the cooling of the melt in the air gap, allowing for more uniform clamping and shear deformation while the melt remains at a high temperature. The above film formation rate is defined as the second clamping surface speed, which is the slower speed at which the molten polymer passes between the two clamping rolls. It is preferable that the movement speed of the first clamping surface is faster than the movement speed of the second clamping surface. Furthermore, it is preferable to adjust the ratio of the movement speeds of the first and second clamping surfaces of the clamping device to 0.60 to 0.99, thereby applying shear stress as the molten resin passes through the clamping device, in order to manufacture the film of the present invention. The two clamping surfaces may be driven together or independently, but independent driving is preferable in terms of uniformity of film properties.

[0126] <Procedure for forming polymer films> • Film formation procedure In the film formation process, it is preferable to perform the film formation process using the following procedure, in terms of stabilizing the film quality. The molten polymer extruded from the die lands on a cast roll and is formed into a film. This film is then cooled and solidified, and then wound up. When compressing a molten polymer, the molten polymer is passed between a first and second compression surface set to a predetermined temperature, cooled and solidified, and then wound up as a film.

[0127] • Conveyor tension The film transport tension can be adjusted as appropriate depending on the film thickness. The transport tension per 1m width of film is preferably 10-500 N / m, more preferably 20-300 N / m, and even more preferably 30-200 N / m. Generally, the transport tension needs to be increased as the film thickness increases. For example, for a film with a thickness of 100 μm, the transport tension is preferably 30-150 N / m, more preferably 40-120 N / m, and even more preferably 50-100 N / m. If the film transport tension is above the lower limit, meandering of the film during transport can be suppressed, thereby preventing slippage between the guide roll and the film and preventing scratches on the film. If the film transport tension is below the upper limit, vertical wrinkles in the film can be suppressed, and the film can be prevented from being stretched too much and breaking. Film tension can be controlled using any of the following methods: a dancer system, a servo motor torque control system, a powder clutch / brake system, or a friction roll control system. However, the dancer system is preferred in terms of control accuracy. The transport tension does not need to be the same throughout the film-forming process; it is also useful to adjust it to an appropriate value for each tension-cut zone. The conveying rolls should preferably have no roll deflection deformation due to conveying tension, low mechanical loss, sufficient friction with the film, and a smooth surface that prevents scratches during film conveying. Using conveying rolls with low mechanical loss eliminates the need for high tension for film conveying, thus suppressing scratches on the film. Furthermore, it is preferable to have a large film gripping angle for the conveying rolls to ensure sufficient friction with the film. The gripping angle is preferably 90° or more, more preferably 100° or more, and even more preferably 120° or more. If a sufficient gripping angle cannot be obtained, it is preferable to use rubber rolls or rolls with a textured, dimpled, or grooved surface to ensure friction.

[0128] • Winding tension The winding tension, like the film transport tension, is preferably adjusted appropriately according to the film thickness. The tension per 1m width of film is preferably 10-500 N / m, more preferably 20-300 N / m, and even more preferably 30-200 N / m. Generally, the tension needs to be increased as the film thickness increases. For example, for a 100 μm film, the winding tension is preferably 30-150 N / m, more preferably 40-120 N / m, and even more preferably 50-100 N / m. If the winding tension is above the lower limit, meandering of the film during film transport can be suppressed, thus preventing the film from slipping and getting scratched during winding. If the winding tension is below the upper limit, vertical wrinkles in the film can be suppressed, preventing the film from becoming too tightly wound and resulting in a better winding appearance. Furthermore, the stretching of the film's knots due to creep can be suppressed, thus preventing the film from becoming wavy. The winding tension, like the transport tension, is preferably detected by tension control along the line and controlled to maintain a constant winding tension during winding. If there are differences in film temperature depending on the location on the film-making line, the film length may differ slightly due to thermal expansion. Therefore, it is preferable to adjust the draw ratio between the nip rolls to prevent the film from being subjected to tension exceeding the specified level along the line. In addition, while the winding tension can be controlled to maintain a constant tension, it is more preferable to taper the winding according to the winding diameter to achieve the appropriate winding tension. Generally, the tension is gradually decreased as the winding diameter increases, but in some cases, it may be preferable to increase the tension as the winding diameter increases. Also, the winding direction does not matter as long as either the first or second clamping surface is on the core side, but if the film has curled, winding in the opposite direction to the curl may be preferable as it has a curl correction effect. To control the meandering of the film during winding, it is useful to install an EPC (Edge Position Control), to perform oscillation winding to prevent the formation of winding knots, and to use a roll that removes enclosed air during high-speed winding.

[0129] • core The core used for winding does not need to be special, as long as it has the strength and rigidity necessary to wind the film. Generally, a paper core with an inner diameter of 3 to 6 inches or a plastic core with an inner diameter of 3 to 14 inches is used. Generally, plastic cores are often used because they generate less dust. Using a small-diameter core is cost-effective, but it can lead to poor winding shape due to bending caused by insufficient rigidity, or curling of the film due to creep deformation at the core. On the other hand, using a large-diameter core is advantageous for maintaining film quality, but it can be disadvantageous in terms of handling and cost. Therefore, it is preferable to select a core of the appropriate size as needed. In addition, a cushioning layer can be provided on the outer circumference of the core to prevent the step caused by the film thickness at the beginning of the winding from being transferred to the film.

[0130] ·slit It is preferable to slit both ends of the formed film to obtain a predetermined width. While common methods such as shear cutters, goebel blades, laser blades, and rotary blades can be used for slitting, it is preferable to use a cutting method that does not generate dust during cutting and produces minimal burrs at the cut end; cutting with a goebel blade is preferred. The cutter blade can be made of carbon steel or stainless steel, but generally, carbide or ceramic blades are preferred because they extend the blade life and suppress the generation of chips. The portion cut off by the slits can be crushed and reused as raw material. After slitting, it is acceptable to either crush it and immediately feed it into the extruder, or to extrude it first to form pellets. In addition, foreign matter may be removed by filtration during the re-pelletization process. The amount to be blended is preferably 0-60%, more preferably 5-50%, and even more preferably 10-40%. Since the trace composition of recycled raw material may differ from that of virgin raw material due to the melt viscosity of the molten polymer or thermal degradation, caution is required during use. Depending on the composition of the recycled raw material, it is also useful to adjust the blending amount appropriately to control the physical properties of the raw material within a certain range. Furthermore, the film used for thickness adjustment or switching can be reused in the same way as the slit edges.

[0131] • Knurling process It is also preferable to perform knurling on one or both ends of the film. The height of the unevenness created by the knurling is preferably 1 to 50 μm, more preferably 2 to 30 μm, and even more preferably 3 to 20 μm. The knurling may be performed so that both sides are convex, or only one side is convex. The width of the knurling is preferably 1 to 50 mm, and more preferably 3 to 30 mm. Both cold and hot knurling can be used for the knurling, and the appropriate method should be selected depending on the degree of deformation of the unevenness formed on the film and the amount of dust generated during the knurling process. Furthermore, it is also useful to make the film formation direction and the film surface identifiable by knurling.

[0132] Masking film To prevent scratches on the film or to improve handling, it is also preferable to apply a laminating film (masking film) to one or both sides. The thickness of the laminating film is preferably 5 to 100 μm, more preferably 10 to 70 μm, and even more preferably 25 to 50 μm. The masking film is preferably composed 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), and polyester. The adhesive layer can be made of EVA (ethylene vinyl acetate), acrylic rubber, styrene elastomer, and natural rubber. Both co-extrusion and film-based adhesive coatings are possible. The adhesive strength is preferably 0.2 to 2.0 N / 25 mm, more preferably 0.3 to 1.5 N / 25 mm, and even more preferably 0.4 to 1.0 N / 25 mm. The adhesive strength can be determined by a method in accordance with JIS Z 0237. Masking film is generally colorless, but sometimes different colors are used on the front and back to distinguish between them. Another effective method for distinguishing the front and back of a film is to apply masking film with different thicknesses, adhesive strengths, and surface gloss levels.

[0133] • Static electricity removal If the film is electrically charged, dust in the atmosphere will be attracted to the film and become foreign matter adhering to it. Therefore, it is preferable that the film is not electrically charged during film formation, transport, and winding. The operating voltage is preferably 3kV or less, more preferably 0.5kV or less, and even more preferably 0.05kV or less. Various known methods can be used to prevent static charge buildup on the film, including methods such as incorporating or coating the film with an antistatic agent, controlling the ambient temperature and humidity to suppress static electricity generation, grounding and dissipating static electricity accumulated on the film, and neutralizing the static charge with an ionizer using a charge of the opposite sign to the static charge. Among these, the method using an ionizer is common. Ionizers include soft X-ray irradiation type and corona discharge type, and either type can be used. Soft X-ray irradiation type is used when explosion protection is required, but corona discharge type is generally more commonly used. Corona discharge types include DC (direct current) type, AC (alternating current) type, and pulsed AC type, with pulsed AC type being widely used in terms of performance and cost. One type of static elimination device may be used, or multiple types may be used in combination, and there are no particular restrictions on the number of devices installed as long as it does not interfere with film formation. Furthermore, in order to improve the effect of preventing dust adhesion to the film by static electricity removal, the environment during film formation is preferably below the US Federal Standard Fed. Std. 209D Class 10000, more preferably below Class 1000, and even more preferably below Class 100.

[0134] ·Dust removal Foreign matter adhering to the film surface can be removed by pressing a scraper or brush against it, by spraying neutralized pressurized air at a pressure of several tens of kPa to weaken the electrostatic attraction effect, by suction, or by a combination of spraying and suction. Known dust removal methods can also be used, such as pressing an adhesive roll against the film to transfer and remove foreign matter, or by applying ultrasonic waves to the film to remove foreign matter by suction. Methods of spraying liquid onto the film or immersing it in liquid to wash away foreign matter can also be used. Furthermore, if film dust is generated at the cut or knurled sections, it is preferable to install a removal device such as a vacuum nozzle to prevent foreign matter from adhering to the film.

[0135] <Stretching process, heat relaxation treatment, heat fixation treatment> Furthermore, after forming an unstretched film using the above method, it may be stretched continuously or discontinuously, and / or subjected to a heat relaxation treatment or a heat fixation treatment. For example, each step can be carried out in the following combinations of (a) to (g). The order of longitudinal stretching and transverse stretching may also be reversed, each of the longitudinal stretching and transverse stretching steps may be carried out in multiple stages, and each of the longitudinal stretching and transverse stretching steps may be combined with oblique stretching or simultaneous biaxial stretching. (a) Lateral extension (b) Transverse stretching → heat relaxation treatment (c) Longitudinal extension (d) Longitudinal stretching → heat relaxation treatment (e) Vertical (horizontal) stretching → Horizontal (vertical) stretching (f) Longitudinal (horizontal) stretching → Horizontal (longitudinal) stretching → Heat relaxation treatment (g) Transverse stretching → heat relaxation treatment → longitudinal stretching → heat relaxation treatment

[0136] • Longitudinal extension Longitudinal stretching can be achieved by heating the space between two pairs of rolls while increasing the peripheral speed on the exit side to be faster than the peripheral speed on the inlet side. For the sake of preventing film curling, it is preferable that the film temperature be the same on both sides; however, if optical properties are to be controlled in the thickness direction, stretching can be performed even if the front and back sides are at different temperatures. Here, the stretching temperature is defined as the temperature on the lower side of the film surface. The longitudinal stretching process can be carried out in one stage or in multiple stages. Film preheating is generally performed by passing the film through a temperature-controlled heated roll, but in some cases, a heater can be used to heat the film. Furthermore, to prevent the film from sticking to the roll, ceramic rolls with improved tackiness can be used.

[0137] ·Horizontal stretching For the transverse stretching process, a conventional transverse stretching method can be employed. That is, a conventional transverse stretching method involves gripping both ends of the film in the width direction with clips and widening the clips while heating them in an oven using a tenter. For the transverse stretching process, 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 Patent Publication No. 6-270246, Japanese Utility Model Publication No. 4-030922, and Japanese Patent Publication No. 62-152721 can be used, and these methods are incorporated herein.

[0138] The stretching ratio in the width direction of the film during the transverse stretching process (transverse stretching ratio) is preferably 1.2 to 6 times, more preferably 1.5 to 5 times, and even more preferably 2 to 4 times. Furthermore, if longitudinal stretching is performed, the transverse stretching ratio is preferably greater than the stretching ratio of longitudinal stretching. The stretching temperature in the transverse stretching process can be controlled by blowing air at the desired temperature into the tenter. For the same reasons as in longitudinal stretching, the film temperature may be the same on the front and back surfaces or different on the back. The stretching temperature used here is defined as the temperature on the lower side of the film surface. The transverse stretching process may be carried out in one stage or in multiple stages. When performing transverse stretching in multiple stages, it may be done continuously or intermittently with zones in between where widening does not occur. In addition to the normal transverse stretching in which the clips are widened in the width direction within the tenter, the following stretching method, which similarly grips and widens the film with clips, can also be applied.

[0139] • Diagonal extension In the diagonal stretching process, the clip is widened in the lateral direction, similar to normal lateral stretching, but it can be stretched in the diagonal direction by changing the transport speed of the left and right clips. For example, the methods described in Japanese Patent Publication Nos. 2002-022944, 2002-086554, 2004-325561, 2008-023775, and 2008-110573 can be used for the diagonal stretching process.

[0140] ·Simultaneous biaxial stretching Simultaneous biaxial stretching, like ordinary transverse stretching, widens the clip in the transverse direction while simultaneously stretching or contracting it 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 for simultaneous biaxial stretching.

[0141] • Heat treatment for improving Boeing (axis misalignment) In the transverse stretching process described above, the edges of the film are held by clips. Therefore, the deformation of the film due to thermal shrinkage stress generated during heat treatment is greater in the center of the film and smaller at the edges, resulting in a distribution in the widthwise characteristics. If a straight line is drawn along the transverse direction on the surface of the film before the heat treatment process, the straight line on the surface of the film after the heat treatment process will be bow-shaped, with the center concave towards the downstream direction. This phenomenon is called bowing and is a cause of disruption to the isotropy and widthwise uniformity of the film. As an improvement method, preheating before lateral stretching or heat-setting after stretching can reduce the variation in orientation angle associated with boeing. Preheating and heat-setting may be done individually, but both are preferable. These preheating and heat-setting processes are preferably performed while gripping with clips, i.e., they are preferably performed in conjunction with stretching.

[0142] Preheating is preferably performed at a temperature 1 to 50°C higher than the stretching temperature, more preferably 2 to 40°C higher, and even more preferably 3 to 30°C higher. The preheating time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During preheating, it is preferable to keep the width of the tenter nearly constant. Here, "nearly" refers to within ±10% of the width of the unstretched film.

[0143] The temperature used for heat fixation is preferably 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. A temperature below the stretching temperature and below the Tg of the liquid crystal polymer is particularly preferred. The heat setting time is preferably 1 second to 10 minutes, more preferably 5 seconds to 4 minutes, and even more preferably 10 seconds to 2 minutes. During heat setting, it is preferable to keep the tenter width approximately constant. Here, "approximately" refers to a tenter width of 0% (same width as the tenter width after stretching) to -30% (30% reduction from the tenter width after stretching = reduction width). Other known methods include those described in Japanese Patent Publication No. 1-165423, Japanese Patent Publication No. 3-216326, Japanese Patent Publication No. 2002-018948, and Japanese Patent Publication No. 2002-137286.

[0144] • Heat relaxation treatment After the stretching process described above, a heat relaxation treatment may be performed to heat the film and cause it to shrink. Performing a heat relaxation treatment can reduce the thermal shrinkage rate of the film when it is used. It is preferable to perform the heat relaxation treatment at at least one timing after film formation, after longitudinal stretching, and after transverse stretching. The thermal relaxation treatment may be performed online immediately after stretching, or offline after winding. Examples of suitable temperatures for the thermal relaxation treatment include those above the glass transition temperature Tg of the liquid crystal polymer and below its melting point Tm. If oxidative degradation of the film is a concern, the thermal relaxation treatment may be performed in an inert gas such as nitrogen, argon, or helium.

[0145] <Post-heat treatment> In order to easily produce a film having the melting peak area described above, it is preferable to perform a post-heat treatment on an unstretched film or a longitudinally stretched film produced by the above method, by performing the transverse stretching described above, and then heating it while fixing the film width. Although the detailed mechanism by which a film with a melting peak area within the above range can be easily produced by heat treatment after transverse stretching is not yet clear, the inventors speculate as follows: That is, the longitudinal orientation structure of the liquid crystal polymer in the fabricated film is broken by transverse stretching, which reduces the degree of crystallinity, while many seed crystals are formed in the film. By performing post-heat treatment on such a film, the crystallization of the seed crystals is promoted, and a film with a higher degree of crystallinity compared to before transverse stretching is produced.

[0146] In the post-heat treatment, the film width is fixed by methods such as gripping both ends of the film in the width direction with clips while the heat treatment is performed. The film width after post-heat treatment is preferably 85-105% and more preferably 95-102% of the film width before post-heat treatment. The heating temperature in the post-heat treatment is preferably {Tm-200}°C or higher, more preferably {Tm-100}°C or higher, and even more preferably {Tm-50}°C or higher, with Tm (°C) being the melting point of the liquid crystal polymer. Alternatively, the heating temperature in the post-heat treatment is preferably 240°C or higher, more preferably 255°C or higher, and even more preferably 270°C or higher. The upper limit of the heating temperature in the post-heat treatment is preferably {Tm}°C or lower, more preferably {Tm-2}°C or lower, and even more preferably {Tm-5}°C or lower. Examples of heating methods used for post-heat treatment include hot air dryers and infrared heaters. Infrared heaters are preferred because they can produce films with the desired melting peak area in a short time. Pressurized steam, microwave heating, and heat transfer medium circulation heating methods may also be used as heating methods. The processing time for the post-heat treatment can be appropriately adjusted depending on the type of liquid crystal polymer, the desired melting peak area, the heating method, and the heating temperature. When using an infrared heater, 1 to 120 seconds is preferred, and 3 to 90 seconds is more preferred. When using a hot air dryer, 0.5 to 30 minutes is preferred, and 1 to 10 minutes is more preferred. Furthermore, the film surface temperature after post-heat treatment is preferably 300°C to less than 360°C, and more preferably 330°C to less than 350°C, as this allows for the production of a film with a smaller AT / AM ratio and less structural anisotropy.

[0147] (Surface treatment) The film can be surface-treated to improve adhesion with 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. Glow discharge treatment as used here refers to 10 -3 Low-temperature plasma generated under a low-pressure gas of ~20 Torr is also acceptable, and plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas refers to a gas that is plasma-excited under the conditions described above, and examples include argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, fluorocarbons such as tetrafluoromethane, and mixtures thereof. It is also preferable to provide an undercoat layer for adhesion with the copper foil or copper plating layer. This layer may be applied after the surface treatment described above, or it may be applied without the surface treatment. These surface treatment and undercoat steps can be incorporated at the end of the film formation process, performed independently, or performed within the copper foil or copper plating layer application process.

[0148] (aging) To improve the mechanical properties, thermal dimensional stability, or winding appearance of the wound film, it is also useful to age the film at a temperature below the Tg of the liquid crystal polymer.

[0149] (Storage conditions) To prevent wrinkles and bulges from forming due to the relaxation of residual strain in the wound film, it is preferable to store the film in a temperature environment below the Tg of the liquid crystal polymer. Furthermore, it is preferable that the temperature fluctuates little, with an hourly temperature fluctuation of 30°C or less being preferable, more preferably 20°C or less, and even more preferably 10°C or less. Similarly, to prevent changes in the film's moisture absorption rate and condensation, the humidity is preferably 10-90%RH, more preferably 20-80%RH, and even more preferably 30-70%RH, with an hourly humidity fluctuation of 30%RH or less being preferable, more preferably 20%RH or less, and even more preferably 10%RH or less. If storage is necessary in a location with temperature and humidity fluctuations, it is also effective to use packaging materials that have moisture-proof or heat-insulating properties.

[0150] In the above description, the film is a single layer, but it may also have a laminated structure in which multiple layers are stacked.

[0151] After the film-forming process, the film may be further processed by compressing it with a heated roll and / or stretching it to further improve its smoothness.

[0152] [Applications of liquid crystal polymer films] Applications of liquid crystal polymer films include, for example, film substrates, laminates formed by bonding with metal foil (flexible laminates), flexible printed circuit boards (FPCs), and laminated circuit boards. Materials used for the metal foil include copper, gold, silver, nickel, aluminum, and alloys containing any of these metals, which are used for electrical connections. In particular, the above-mentioned liquid crystal polymer film is preferably used for high-speed communication substrates having a liquid crystal polymer film. [Examples]

[0153] Examples and comparative examples of the present invention will be described below. Liquid crystal polymer films of Examples 1-7 and Comparative Example 1 were prepared using the manufacturing methods described below, and evaluated as described later. First, the manufacturing methods for each example and comparative example of the liquid crystal polymer film will be explained.

[0154] [material] The materials used to produce the film are listed below.

[0155] [Liquid crystal polymer] • LCP1: A polymer synthesized based on Example 1 of Japanese Patent Publication No. 2019-116586. Melting point: 320°C. It is a thermotropic liquid crystal polymer. • LCP2: Laperos C-950 manufactured by Polyplastics, Inc., melting point 320°C, corresponds to a thermotropic liquid crystal polymer. • LCP3: Laperos A-950 manufactured by Polyplastics, Inc., melting point 280°C, corresponds to a thermotropic liquid crystal polymer. LCP1 is composed of repeating units derived from 6-hydroxy-2-naphthoic acid, 4,4'-dihydroxybiphenyl, terephthalic acid, and 2,6-naphthalenedicarboxylic acid. LCP2 and LCP3 are both polymers represented by the following chemical formulas. However, the content ratio of each repeating unit constituting the two polymers differs.

[0156] [ka]

[0157] [Polyolefins] • Novatec LD (low-density polyethylene) manufactured by Nippon Polyethylene Co., Ltd. [Compatible components] • Ethylene / glycidyl methacrylate copolymer [Heat stabilizer] • ADEKA's "AO-80" (semi-hindered phenol-based stabilizer)

[0158] [Manufacturing] A liquid crystal polymer film was manufactured using the method described below.

[0159] [Supply process] The components listed in the table below (liquid crystal polymer, polyolefin, compatible components, and heat stabilizer) were mixed in the proportions shown in the table and kneaded into pellets using an extruder. The pellets obtained from the kneading process were dried for 12 hours in a dehumidifying hot air dryer at 80°C with a dew point of -45°C to reduce the moisture content to 200 ppm or less. The pellets dried in this way are also called raw material A.

[0160] [Film forming process] Raw material A was supplied into the cylinder from the same feed port of a twin-screw extruder with a screw diameter of 50 mm, heated and kneaded, and the molten raw material A was discharged in film form onto a rotating cast roll from a die with a die width of 750 mm, cooled and solidified, and stretched as desired to obtain a film with a thickness of 150 μm. The heating and kneading temperature, the discharge speed when dispensing raw material A, the die lip clearance, and the peripheral speed of the cast roll were each adjusted within the following ranges. • Heating and mixing temperature: 270~350℃ • Clearance: 0.01~5mm ·Discharge speed: 0.1~1000mm / sec Castroll peripheral speed: 0.1~100m / min

[0161] [Horizontal stretching process] The film produced in the film-forming process was stretched in the TD direction using a tenter. The stretching ratio at this time was 3.2 times.

[0162] [Post-heat treatment] The film, after undergoing the stretching process, was held at both ends in the width direction with a jig to prevent shrinkage in that direction. The film, in this fixed state, was then subjected to post-heat treatment using an infrared heater or a hot air dryer. In the post-heating treatment using infrared heaters, both sides of the film were heated for 30 seconds using one set of infrared heaters at a film surface temperature of 300°C. In the post-heat treatment using a hot air dryer, the film, fixed with a jig, was placed inside the hot air dryer and heated for 180 seconds at a film surface temperature of 300°C before being removed from the hot air dryer. In Example 6, as a post-heat treatment, an infrared heater was placed on the film being conveyed on a metal roller, and the film surface temperature was raised to 350°C by heating for 5 seconds. The output and position of the infrared heater were adjusted so that the film surface temperature was maintained for less than 1 second, and the film was heated. The film was then flipped over, and the same post-heat treatment was performed on the reverse side. In Example 7, the procedure was the same as in Example 6, except that the film surface temperature was raised to 330°C by heating for 5 seconds, and the time for maintaining that film surface temperature was less than 1 second.

[0163] In the heat treatment process, a film for measuring the film surface temperature was placed near the film to be heat-treated, and the film surface temperature was measured using a thermocouple attached to the surface of the film for measuring the film surface temperature with polyimide tape.

[0164] Table 1 below shows the formulations of raw material A used in the production of the films in Examples 1 to 7 and Comparative Example 1, as well as the characteristics of each production method. In the table, the "Dielectric Loss Tangent" column for "Liquid Crystal Polymer" shows the dielectric loss tangent of each liquid crystal polymer measured under conditions of 23°C, 50% RH humidity, and 28 GHz frequency. Details of the measurement method are as described above. The "Quantity [%]" column for "Liquid Crystal Polymer," "Polyolefin," "Compatible Components," and "Heat Stabilizer" indicates the content (mass %) of each component relative to the total mass of the film. In the "Heat Treatment Process" section of the "Manufacturing Method," "IR" means that the heat treatment process was carried out using an infrared heater, and "Hot Air" means that the heat treatment process was carried out using a hot air dryer.

[0165] [Table 1]

[0166] [Measurement and Evaluation] The following measurements and evaluations were performed on each film obtained using the method described above.

[0167] [Melting peak area] The center portion of the film was sampled, and the melting peak area of ​​the obtained sample was measured using a differential scanning calorimeter (Shimadzu Corporation "DSC-60A"). Specifically, the sample was heated from 25°C to 380°C at a heating rate of 10°C / min, and the endothermic and exothermic amounts of the sample were measured. A curve (DSC curve) showing the change in the measured endothermic and exothermic amounts was created. The area of ​​the endothermic peak (melting peak) enclosed by the baseline of the created DSC curve was calculated to determine the melting peak area (unit: J / g) of the sample. The endothermic peak and baseline in the DSC curve were identified based on JIS K 7121.

[0168] [X-ray diffraction measurement] The center portion of the film was sampled, and the X-ray diffraction intensity of the obtained sample was measured using an X-ray diffraction analyzer (Rigaku Corporation's "R-axis"). One direction within the plane of the sample was selected as the reference direction, and measurements were performed at 5° intervals using the X-ray diffraction analyzer in the range where the rotation angle φ of the film relative to the reference direction was 0 to 360°. From the obtained diffraction peak profiles, the peak intensity of the peaks detected in the range of 2θ = 16 to 22° was determined. From the obtained peak intensities, the maximum value AT of the peak intensity and the rotation angle φ at which the peak intensity AT was obtained were determined. T Furthermore, we determine the rotation angle φ T The rotation angle φ is 90° different from the given value. M , and rotation angle φ M The peak intensity AM was determined, and the ratio AT / AM was calculated from the peak intensity AT to the peak intensity AM.

[0169] [Dielectric loss tangent] The center part of the film was sampled, and the dielectric loss tangent in the frequency band of 28 GHz was measured at a temperature of 20°C and a humidity of 65% RH using a split cylinder type resonator (CR-728 manufactured by Kanto Electronic Application Development Co., Ltd.) and a network analyzer (Keysight N5230A).

[0170] [CTE (in-plane direction)] The CTE (linear expansion coefficient) in the in-plane direction of the film was measured using a thermomechanical analyzer (TMA: Thermal Mechanical Analysis, manufactured by Shimadzu Corporation) in accordance with JIS K 7197. More specifically, a sample with a width of 5 mm and a length of 14 mm was cut out from the center part of the film. At this time, 17 samples were prepared with the angle formed by the longitudinal direction of the sample varying by 10 degrees from 0 degrees to 170 degrees with respect to the TD direction of the film, and the CTE of each prepared sample was measured using the above device. From the obtained measurement results, the minimum value of CTE (CTE1) in the in-plane of the film and the CTE (CTE2) in the second direction orthogonal to the first direction where CTE becomes the minimum value were respectively obtained, and further, the ratio of CTE2 to CTE1 (CTE2 / CTE1) (CTE ratio) was obtained.

[0171] [[ID=?]] The CTE in the film thickness direction of the film was measured using a thermomechanical analyzer (TMA-Q400 manufactured by TA Instruments Japan). Specifically, a sample with a width of 6 mm and a length of 6 mm was cut out from the center part of the film, the sample was taken out and placed on the sample stage of the above thermomechanical analyzer, and then the change (expansion or contraction) in the film thickness direction of the sample was precisely measured in the compression mode to measure the CTE in the film thickness direction of the film. The temperature profile (heating rate, cooling rate) for the CTE measurement in the film thickness direction was the same as that in the above in-plane direction CTE measurement. The CTE in the film thickness direction of the films manufactured in Examples 1 to 7 was all within the range of 50 to 450 ppm / °C.

[0172] ​[Surface roughness Ra] The surface roughness (maximum height) Ra of the film was measured using a stylus-type roughness meter in accordance with JIS B 0601. Surface roughness Ra was measured at five randomly selected locations within a 10cm x 10cm area in the center of the film, and the arithmetic mean was calculated. The surface roughness Ra of the films produced in Examples 1 to 7 was in the range of 150 to 420 μm.

[0173] [Average dispersion diameter] The dispersed phase of polyolefin in the film was observed using a scanning electron microscope (SEM), and the mean dispersion diameter was determined by the following method. At 10 different locations on the sample, we observed two cross-sections: one parallel to the film's width direction and perpendicular to the film surface, and another perpendicular to the film's width direction and perpendicular to the film surface, obtaining a total of 20 observation images. The observations were performed at appropriate magnifications ranging from 100 to 100,000 times, and images were taken to confirm the dispersion state of the particles (the dispersed phase formed by polyolefins) across the entire width of the film's thickness. For each of the 20 images, 200 randomly selected particles had their outer circumference traced, and the equivalent circular diameter of the particles was measured from these traced images using an image analysis device to determine the particle size. The average value of the particle size measured from each captured image was defined as the average dispersion diameter of the dispersed phase. The average dispersion diameter of the polyolefin dispersed phase formed in the films produced in Examples 1 to 7 was in the range of 0.05 to 5 μm in all cases.

[0174] [Dielectric loss tangent] The dielectric loss tangent of the film measured using the above measurement method was evaluated according to the following criteria. A: Less than 0.0010 B: 0.0010 or greater, less than 0.0015 C: 0.0015 or higher, less than 0.0018 D: 0.0018 or more and 0.0020 or less E: over 0.0020

[0175] [CTE] The CTE of the film was evaluated based on the CTE1 and CTE2 values ​​obtained using the measurement method described above, according to the following criteria. A: Both CTE1 and CTE2 are at 10-30 ppm / ℃ B: Both CTE1 and CTE2 are between 0 and 40 ppm / °C (except when both CTE1 and CTE2 are between 10 and 30 ppm / °C). C: One of CTE1 and CTE2 is 0-40 ppm / °C, and the other is less than 0 ppm / °C or greater than 40 ppm / °C. D: Both CTE1 and CTE2 are below 0 ppm / °C or above 40 ppm / °C.

[0176] [result] Table 2 below shows the evaluation results for each film.

[0177] [Table 2]

[0178] The results shown in the table above confirm that the liquid crystal polymer film of the present invention can solve the problems of the present invention.

[0179] In terms of superior effects of the present invention, it was confirmed that liquid crystal polymers containing 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 are preferred (comparison of Examples 1 to 5, etc.). Furthermore, it was confirmed that liquid crystal polymers with a melting point Tm of 285°C or higher are preferable in terms of exhibiting superior effects of the present invention (comparison of Examples 1-5, etc.). Furthermore, it was confirmed that using an infrared heater to perform the heat treatment process on the film is preferable in terms of achieving superior effects of the present invention (comparison of Examples 1-4, etc.).

Claims

1. A stretched liquid crystal polymer film comprising a liquid crystal polymer, a polyolefin, and a polymer having a reactive group for the phenolic hydroxyl group or carboxyl group at the end of the liquid crystal polymer, The liquid crystal polymer is a thermoplastic polyester containing repeating units derived from 6-hydroxy-2-naphthoic acid. In the liquid crystal polymer film, the polyolefin forms a dispersed phase. The area of ​​the melting peak of the liquid crystal polymer, as measured by differential scanning calorimetry, is 0.2 J / g or more. The liquid crystal polymer content is 60 to 90% by mass relative to the total mass of the liquid crystal polymer film. The polyolefin content is 5 to 25% by mass relative to the total mass of the liquid crystal polymer film. A liquid crystal polymer film in which the polymer content is 0.5 to 10% by mass relative to the total mass of the liquid crystal polymer film.

2. The liquid crystal polymer film according to claim 1, wherein the ratio AT / AM obtained by the method 1 described below is 1.0 to 1.

5. Method 1: X-rays are incident on the surface of a liquid crystal polymer film using an X-ray diffractometer, and the peak intensity detected in the range of 2θ = 16 to 22° is measured. The liquid crystal polymer film is rotated in the in-plane direction within a range of 0 to 360°, using any one direction within the plane of the liquid crystal polymer film as a reference, and the peak intensity is measured. From the obtained measurement results, the maximum value of the peak intensity AT and the rotation angle φ at which the peak intensity is maximized are determined. Ｔ Next, we find the rotation angle φ. Ｔ The rotation angle φ is such that the difference from is 90°. Ｍ The peak intensity AM is determined, and the ratio of peak intensity AT to peak intensity AM, AT / AM, is calculated.

3. A liquid crystal polymer film according to claim 1 or 2, wherein the dielectric loss tangent under conditions of a temperature of 23°C, a humidity of 50% RH, and a frequency of 28 GHz is 0.002 or less.

4. The liquid crystal polymer film according to any one of claims 1 to 3, wherein the dielectric loss tangent of the liquid crystal polymer under conditions of a temperature of 23°C, a humidity of 50% RH, and a frequency of 28 GHz is 0.002 or less.

5. A liquid crystal polymer film according to any one of claims 1 to 4, wherein the coefficient of linear expansion in the film thickness direction is 50 to 450 ppm / °C.

6. The first linear expansion coefficient in the first direction within the plane of the liquid crystal polymer film, and the second linear expansion coefficient in the second direction perpendicular to the first direction within the plane of the liquid crystal polymer film, are both 10 to 30 ppm / °C. The liquid crystal polymer film according to any one of claims 1 to 5, wherein the first coefficient of linear expansion is the minimum value of the coefficient of linear expansion in the plane of the liquid crystal polymer film.

7. The liquid crystal polymer film according to claim 6, wherein the ratio of the second coefficient of linear expansion to the first coefficient of linear expansion is 1.0 to 1.

5.

8. A liquid crystal polymer film according to any one of claims 1 to 7, wherein the surface roughness Ra is less than 430 nm.

9. The liquid crystal polymer film according to any one of claims 1 to 8, wherein the melting point Tm of the liquid crystal polymer is 285°C or higher.

10. The liquid crystal polymer film according to any one of claims 1 to 9, wherein the liquid crystal polymer further comprises repeating units derived from parahydroxybenzoic acid.

11. The liquid crystal polymer film according to any one of claims 1 to 9, wherein the liquid crystal polymer further comprises repeating units derived from an aromatic diol compound, repeating units derived from terephthalic acid, and repeating units derived from 2,6-naphthalenedicarboxylic acid.

12. The liquid crystal polymer film according to any one of claims 1 to 11, wherein the average dispersion diameter of the dispersed phase is 0.01 to 10 μm.

13. A high-speed communication substrate having a liquid crystal polymer film according to any one of claims 1 to 12.

Images