JP2022019196A - Method for producing extrusion-molded film and extrusion-molded film - Google Patents

Abstract

To provide a method for producing an extrusion-molded film excellent in electric characteristics and UV processability, and to provide an extrusion-molded film excellent in such characteristics.SOLUTION: The method for producing an extrusion-molded film according to the present invention provides an extrusion-molded film containing 10 mass% or less of an aromatic polymer by melt extrusion molding of a mixture of: a melt-kneaded product of particles of a first tetrafluoroethylene polymer having a melting temperature of 270-320°C and particles of the aromatic polymer having an average particle diameter of 1-10 μm; and particles of a second tetrafluoroethylene polymer having a melting temperature of 270-320°C.SELECTED DRAWING: None

Description

The present invention relates to a method for producing an extruded film and an extruded film.

Since the tetrafluoroethylene polymer has a low relative permittivity and dielectric loss tangent, it is used for an electric insulator layer of a printed wiring board that transmits a high frequency signal. In a printed wiring board, when a through hole is formed in a laminated body in which conductors are provided on both sides of an electrical insulator layer, and a plating layer is formed on the inner wall surface of the through hole to ensure continuity between the conductors. There are many. A UV-YAG laser is used to form the through holes.
Further, the tetrafluoroethylene polymer has a low absorption rate in the UV wavelength range. Therefore, in a printed wiring board having a layer of a tetrafluoroethylene polymer, high-power laser irradiation is required in order to form through holes. As a result, the layers and conductors are deformed by the heat generated during laser irradiation, and delamination and the like are likely to occur.

In Patent Document 1, a UV absorber is contained in the film to improve the processability of drilling with a UV-YAG laser, but the UV absorber deteriorates the electrical properties such as the electrical insulation property of the film.
In Patent Document 2, the tetrafluoroethylene polymer is treated at a high temperature to improve the processability of drilling with a UV-YAG laser, but a manufacturing apparatus suitable for the high temperature treatment is required.

Special Table 4-503081 Gazette International Publication No. 2019/0893939

The present inventors have diligently studied to obtain a film having both electrical characteristics and processability of drilling with a UV-YAG laser. As a result, the film obtained by melt-extruding a mixture of the predetermined tetrafluoroethylene polymer particles and the predetermined aromatic polymer particles in a melt-kneaded product and the predetermined tetrafluoroethylene polymer particles is obtained. It was found that both have excellent physical properties. In addition, the film was also excellent in adhesiveness to other materials.

The present invention has the following aspects.
<1> A melt-kneaded product of first tetrafluoroethylene polymer particles having a melting temperature of 270 to 320 ° C. and aromatic polymer particles having an average particle diameter of 1 to 10 μm, and a melting temperature of 270 to 320 ° C. A method for producing an extrusion-molded film, wherein a mixture with particles of a second tetrafluoroethylene polymer is melt-extruded to obtain an extrusion-molded film containing the aromatic polymer in an amount of 10% by mass or less.
<2> A tetrafluoroethylene-based polymer in which the first tetrafluoroethylene-based polymer and the second tetrafluoroethylene-based polymer each independently contain a unit based on perfluoro (alkyl vinyl ether) and have a polar functional group. Alternatively, the method for producing <1>, which is a tetrafluoroethylene-based polymer containing 2.0 to 5.0 mol% of units based on perfluoro (alkyl vinyl ether) with respect to all units and having no polar functional group.
<3> The method for producing <1> or <2>, wherein the first tetrafluoroethylene polymer and the second tetrafluoroethylene polymer are the same tetrafluoroethylene polymer.
<4> The production method according to any one of <1> to <3>, wherein the aromatic polymer is a non-thermoplastic polyimide.
<5> The production method according to any one of <1> to <4>, wherein the glass transition temperature of the aromatic polymer is in the range of the melting temperature of the first tetrafluoroethylene polymer + 20 ° C. or higher.
<6> The production method according to any one of <1> to <5>, wherein the melt flow rate of the second tetrafluoroethylene polymer is in the range of ± 7 g / 10 minutes of the melt flow rate of the melt-kneaded pellets.
<7><1> to <6>, wherein the content of the aromatic polymer in the melt-kneaded product is 5 to 30 parts by mass with respect to 100 parts by mass of the first tetrafluoroethylene-based polymer. Either manufacturing method.
<8> Production of any one of <1> to <7>, wherein in the mixture, the mixing ratio of the particles of the second tetrafluoroethylene-based polymer to the melt-kneaded product by mass is 5 to 20. Method.
<9> An extruded film containing a sea domain of a tetrafluoroethylene-based polymer having a melting temperature of 270 to 320 ° C. and an island domain of an aromatic polymer, and the content of the aromatic polymer in the extruded film. However, the average domain diameter of the island domain is 10% by mass or less, the average domain diameter of the island domain is 1 to 10 μm, and the transmittance of light having a wavelength of 355 nm in the extruded film having a thickness of 25 μm is 80% or less. Extruded film.
<10> The tetrafluoroethylene-based polymer contains a unit based on perfluoro (alkyl vinyl ether) and has a polar functional group, or a tetrafluoroethylene-based polymer having a polar functional group, or a unit based on perfluoro (alkyl vinyl ether) for all units. The extrusion-molded film of <9>, which is a tetrafluoroethylene-based polymer containing 0.0 to 5.0 mol% and having no polar functional group.
<11> The extruded film of <9> or <10>, wherein the aromatic polymer is a non-thermoplastic polyimide.
<12> The extruded film according to any one of <9> to <11>, wherein the content of the aromatic polymer is 0.1 to 5% by mass.
<13> The extruded film according to any one of <9> to <12>, wherein the difference between the maximum value and the minimum value of the transmittance is 7% or less in the plane of the extruded film having a thickness of 25 μm. ..
<14> The extruded film according to any one of <9> to <13>, wherein the thickness of the extruded film is more than twice the average domain diameter of the island domain.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing an extruded film, which is excellent in electrical characteristics and processability for drilling holes by a UV-YAG laser (hereinafter, also referred to as "UV processability"). Further, it is possible to provide an extruded film having such excellent characteristics.

The following terms have the following meanings.
The "average particle diameter (D50)" is a volume-based cumulative 50% diameter of an object (particle, filler) determined by a laser diffraction / scattering method. That is, the particle size distribution of the object is measured by the laser diffraction / scattering method, the cumulative curve is obtained with the total volume of the group of particles of the object as 100%, and the particles at the point where the cumulative volume is 50% on the cumulative curve. The diameter.
“D90” is the volume-based cumulative 90% diameter of the object, which is similarly measured.
The "melting temperature (melting point)" is the temperature corresponding to the maximum value of the melting peak of the polymer measured by the differential scanning calorimetry (DSC) method.
The "glass transition point (Tg)" is a value measured by analyzing a polymer, cured product or elastomer by a dynamic viscoelasticity measurement (DMA) method.
The "specific surface area of particles" is determined by using NOVA4200e (manufactured by Quantachrome Instruments) by the gas adsorption (constant volume method) BET multipoint method.
"Melting flow rate (MFR)" means the melt mass flow rate of a polymer as defined in JIS K 7210: 1999 (ISO 1133: 1997).
"Film thickness" is determined by using a contact type thickness gauge DG-525H (manufactured by Ono Sokki Co., Ltd.) and using a stylus AA-026 (Φ10 mm, SR7) to measure the film thickness in the width direction. It is an average value of the measured values measured at 10 points so that is equal.
The “ten-point average roughness (Rzjis) of the surface of the metal foil layer” is a value specified in Annex JA of JIS B 0601: 2013.
The "dielectric loss tangent" is a value measured by the SPDR method at a frequency of 10 GHz in an environment of 24 ° C. and 50% RH.
The "unit" in the polymer may be an atomic group formed directly from the monomer, or may be an atomic group in which a part of the structure is converted by treating the obtained polymer by a predetermined method. The unit based on the monomer A contained in the polymer is also simply referred to as "monomer A unit".

The method for producing an extruded film of the present invention (hereinafter, also referred to as "this method") is also referred to as a first tetrafluoroethylene-based polymer having a melting temperature of 270 to 320 ° C. (hereinafter, also referred to as "first F polymer"). ) Particles (hereinafter, also referred to as “first F particles”) and particles of an aromatic polymer having a D50 of 1 to 10 μm (hereinafter, also referred to as “AR polymer”) (hereinafter, also referred to as “AR particles”). A second tetrafluoroethylene polymer (hereinafter, also referred to as “second F polymer”) having a melting temperature of 270 to 320 ° C., which does not contain an AR polymer and is a melt-kneaded product (hereinafter referred to as “second F polymer”). It is a method of obtaining an extrusion-molded film containing 10% by mass or less of an AR polymer (hereinafter, also referred to as “this film”) by melt-extruding a mixture with “second F particles”).

According to this method, the present film having excellent electrical characteristics and UV processability can be obtained. The reason is not always clear, but it is thought to be as follows.
This film contains a small amount of AR polymer. Therefore, in this film, a sea-island structure is formed in which the domain containing two F polymers is the sea and the domain containing the AR polymer is an island.

In this method, a melt-kneaded product (melt-kneaded pellet) containing the first F polymer and the AR polymer is obtained, and the present film is produced from the melt-kneaded product and the second F particles. The melt-kneaded product can also be regarded as a masterbatch. It is considered that the AR polymer is less likely to aggregate and island domains of uniform size are formed in the film because the polymer is sufficiently sheared during the formation of the masterbatch. Further, it is considered that when the present film is formed, the AR polymer and the two F polymers are sufficiently mixed, the island domains are uniformly dispersed in the present film, and high UV absorption is exhibited.

In addition, the present inventors can effectively invade the island domain when the average domain diameter of the island domain is within a predetermined range, so that even when the content of the AR polymer in the film is low, the present invention can be used. It has been found that the absorption of light rays in the film is enhanced. The average domain diameter of the formed island domains is believed to depend on the D50 of the AR particles. In this method, this film is formed using AR particles having a predetermined D50 (1 to 10 μm). Therefore, in this film, it is considered that an island domain having an appropriate domain diameter is formed at least with an AR polymer content, and the film has high UV absorption.

In this method, it is preferable that the first F polymer and the second F polymer are the same F polymer. In this case, during melt extrusion molding, the first F polymer and the second F polymer are uniformly mixed, and a homogeneous sea domain is likely to be formed in the present film.
In this method, the glass transition temperature of the AR polymer is preferably in the range of the melting temperature of the first F polymer + 20 ° C. or higher, and more preferably in the range of the melting temperature + 30 ° C. or higher. The glass transition temperature of the AR polymer is preferably in the range of the melting temperature of the first F polymer + 60 ° C. or lower, and more preferably in the range of the melting temperature + 50 ° C. or lower. In this case, during the formation of the melt-kneaded product and the melt extrusion molding, the AR polymer is less likely to be in a molten state regardless of the type of the AR polymer, and an island domain having an appropriate domain diameter is likely to be formed in this film. ..

The MFR of the second F polymer is preferably in the range of ± 7 g / 10 min of the MFR of the melt-kneaded product, and more preferably in the range of ± 5 g / 10 min. In this case, since the MFR of the second F polymer and the MFR of the melt-kneaded product are close to each other, the AR polymer and the two F polymers are sufficiently mixed when forming the film, and the island domain is formed in the film. Can be uniformly dispersed and higher UV absorption can be exhibited.
The content of the AR polymer in the melt-kneaded product is preferably 5 to 30 parts by mass, more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the first F polymer. In this case, in this film, the electrical characteristics and the UV processability are easily balanced.
In the mixture, the mixing ratio of the second F particles to the melt-kneaded product by mass is preferably 5 to 20, and more preferably 5 to 10. In this case, in this film, the electrical characteristics and the UV processability are more easily balanced.

The first F polymer in the present invention is a polymer containing a unit (TFE unit) based on tetrafluoroethylene (TFE). The first F polymer in the present invention is thermally meltable. The melting temperature of the first F polymer is 270 to 320 ° C., preferably 275 to 315 ° C., more preferably 290 to 310 ° C. In this case, the moldability of the first F polymer and the mechanical strength of the film are easily balanced.
The glass transition point of the first F polymer is preferably 75 to 125 ° C, more preferably 80 to 100 ° C.
The MFR of the first F polymer is preferably 0.5 to 100 g / 10 minutes, more preferably 1 to 30 g / 10 minutes. In this case, this film tends to be excellent in surface smoothness, appearance, and mechanical strength.

Examples of the first F polymer include a polymer (PFA) containing a TFE unit and a unit (PAVE unit) based on perfluoro (alkyl vinyl ether) (PAVE), and a polymer (FEP) containing a unit based on hexafluoropropene (HFP). Therefore, it is preferably PFA. As the PAVE, CF ₂ = CFOCF ₃ , CF ₂ = CFOCF ₂ CF ₃ and CF ₂ = CFOCF ₂ CF ₂ CF ₃ (PPVE) are preferable, and PPVE is more preferable.

The first F polymer preferably has a polar functional group. The polar functional group may be contained in a unit in the first F polymer, or may be contained in the terminal group of the main chain of the first F polymer. In the latter aspect, a first F polymer having a polar functional group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and a first F having a polar functional group obtained by plasma treatment or ionization line treatment. Polymers can be mentioned. The polar functional group is preferably a hydroxyl group-containing group or a carbonyl group-containing group.

The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF ₂ CH ₂ OH or -C (CF ₃ ) ₂ OH.
The carbonyl group-containing group is a group containing a carbonyl group (> C (O)), a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC (O) NH ₂ ), and an acid anhydride residue. Group (-C (O) OC (O)-), imide residue (-C (O) NHC (O)-etc.) or carbonate group (-OC (O) O-) is preferred, and acid anhydride residue. Is more preferable.

The first F polymer is a polymer having a polar functional group (1) containing TFE units and PAVE units, or 2.0 to 5.0 mol of PAVE units with respect to all units including TFE units and PAVE units. %, The polymer (2) having no polar functional group is preferable.
Since these polymers form microspherulites in this film, adhesion to other components is likely to increase, and island domains having an appropriate domain diameter are also likely to be formed. As a result, the present film having excellent surface smoothness, adhesiveness, electrical properties and UV absorbability (UV processability) can be obtained.

The polymer (1) is preferably a polymer containing a TFE unit, a PAVE unit and a unit based on a monomer having a polar functional group, and 90 to 99 mol% of these units are used in this order with respect to all the units, 0. More preferably, it is a polymer containing 5.5 to 9.97 mol% and 0.01 to 3 mol%. Further, as the monomer having a polar functional group, itaconic anhydride, citraconic anhydride or 5-norbornen-2,3-dicarboxylic acid anhydride (hereinafter, also referred to as “NAH”) is preferable. Specific examples of the polymer (1) include the polymers described in International Publication No. 2018/16644.

The polymer (2) consists of only TFE units and PAVE units, and contains 95.0 to 98.0 mol% of TFE units and 2.0 to 5.0 mol% of PAVE units with respect to all the units. Is preferable. The content of PAVE units in the polymer (2) is preferably 2.1 mol% or more, more preferably 2.2 mol% or more, based on all the units.
The fact that the polymer (2) does not have polar functional groups means that the number of polar functional groups possessed by the polymer is less than 500 per 1 × 10 ⁶ carbon atoms constituting the polymer main chain. means. The number of the polar functional groups is preferably 100 or less, more preferably less than 50. The lower limit of the number of polar functional groups is usually 0.

The polymer (2) may be produced by using a polymerization initiator, a chain transfer agent, or the like that does not generate a polar functional group as the terminal group of the polymer chain, and the first F polymer having a polar functional group (polymerization initiation). A polymer (1) or the like having a polar functional group derived from the agent at the terminal group of the main chain of the polymer may be fluorinated to produce the polymer. Examples of the fluorination treatment method include a method using fluorine gas (see JP-A-2019-194314).

The first F particle in the present invention is a particle containing the first F polymer, and the content of the first F polymer in the first F particle is preferably 80% by mass or more, preferably 100% by mass. More preferred.
The first F particle may contain a polymer different from that of the first F polymer. Different polymers include aromatic polyesters, polyamideimides, polyimides, polyphenylene ethers, polyphenylene oxides, maleimides.
The first F particle may contain an inorganic substance. As the inorganic substance, oxides, nitrides, simple metals, alloys and carbons are preferable, and silicon oxide (silica) and metal oxides (beryllium oxide, cerium oxide, alumina, soda alumina, magnesium oxide, zinc oxide, titanium oxide, etc.) are preferable. , Boron nitride, and magnesium metasilicate (steatite) are more preferred, silica and boron nitride are even more preferred, and silica is particularly preferred. In this case, this film tends to be excellent in electrical characteristics, low line expandability and UV water absorption. The F particles containing an inorganic substance preferably have an F polymer as a core and have an inorganic substance on the surface of the core. Such F particles are obtained, for example, by coalescing (collision, agglomeration, etc.) of F polymer particles and inorganic particles.

The first F particles may be in the form of pellets or powders. The first F particles are preferably in the form of powder.
The D50 of the powdery first F particles is preferably 50 μm or less, more preferably 20 μm or less, still more preferably 8 μm or less. The D50 of the first F particle is preferably 0.1 μm or more, more preferably 0.3 μm or more, still more preferably 1 μm or more. The D90 of the first F particle is preferably less than 100 μm, more preferably 90 μm or less.
The specific surface area of the powdery first F particles is preferably 1 to 8 m ² / g, more preferably 1 to 5 m ² / g, and even more preferably 1 to 3 m ² / g.
When the powdery first F particles D50, D90 and the specific surface area are within the above ranges, it is easy to smoothly mix the powdery first F particles with the AR particles when forming the melt-kneaded product.

The AR polymer in the present invention includes aromatic elastomers such as liquid crystal polyester, polyphthalamide, aromatic polyetherketone, syndiotactic polystyrene, aromatic polyimide, aromatic maleimide, aromatic bismaleimide, polyphenylene ether, and styrene elastomer. Aromatic polyamic acid is preferable, and aromatic polyimide or aromatic polyamic acid is more preferable.
The aromatic polyimide may be thermoplastic or non-thermoplastic. The thermoplastic polyimide means a polyimide that has been imidized and does not undergo a further imidization reaction.
Among them, the non-thermoplastic polyimide is preferable as the AR polymer. If such a non-thermoplastic polyimide is used, an island domain having a target domain diameter is likely to be formed in this film. Therefore, this film can exhibit more excellent UV processability.

In the present specification, the term "non-thermoplastic polyimide" refers to a molded product (film or the like) formed by combining monomers, drying a solution obtained by solution polymerization (solution of a polyimide precursor), and further imidizing the solution. ) Is defined as a polyimide that retains its shape when heated at 450 ° C. for 1 minute. When the molded product is heated at 450 ° C. for 1 minute, the polyimide that is deformed or fused due to wrinkles or elongation is referred to as “thermoplastic polyimide”.

Specific examples of thermoplastic polyimides include "Neoprim (registered trademark)" series (manufactured by Mitsubishi Gas Chemical Company), "Spixeria (registered trademark)" series (manufactured by Somar), and "Q-PILON (registered trademark)" series ( PI Technology Research Institute), "WINGO" series (Wingo Technology), "Toamide (registered trademark)" series (T & K TOKA), "KPI-MX" series (Kawamura Sangyo), "Yupia (" Registered trademark) -AT "series (manufactured by Ube Kosan Co., Ltd.) can be mentioned.

The non-thermoplastic polyimide preferably contains a non-thermoplastic block moiety.
The non-thermoplastic block site is a polyimide precursor obtained by solution-polymerizing only the monomers constituting the block site, and the shape is retained when evaluated by the same method as the method in the above-mentioned definition of non-thermoplastic polyimide. It means a block portion formed from a combination of monomers that forms the polyimide to be formed.

On the other hand, the thermoplastic block site has a shape when evaluated from a polyimide precursor obtained by solution-polymerizing only the monomers constituting the block site by the same method as the method in the above-mentioned definition of non-thermoplastic polyimide. It means a block site formed from a combination of monomers that forms a non-retained polyimide.
When determining whether the block portion is thermoplastic or non-thermoplastic, if a combination of rigid monomers is selected, the molded product may be broken or shattered. In this case, the debris may be collected and heated, and the shape may be determined from the holding state.

The glass transition temperature of the non-thermoplastic polyimide is preferably 280 ° C. or higher, more preferably 290 ° C. or higher. The glass transition temperature is preferably 450 ° C. or lower, more preferably 400 ° C. or lower. In this case, this film can be molded by melt extrusion molding at a lower temperature.
The imide group density of the non-thermoplastic polyimide is preferably 0.20 to 0.35. When the imide group density is not more than the above upper limit, the water absorption rate of the non-thermoplastic polyimide becomes lower, and it is easier to suppress the change in the electrical characteristics (particularly the dielectric characteristics) of the present film. When the imide group density is equal to or higher than the above lower limit, the imide group functions as a polar group, and not only the adhesion of the film is further improved, but also the water absorption rate is likely to be significantly reduced.

The imide group density is a value obtained by dividing the molecular weight per unit (140.1) of the imide group portion by the molecular weight per unit of the polyimide in the polyimide obtained by imidizing the polyimide precursor. For example, a polyimide precursor consisting of two components, 1 mol of pyromellitic dianhydride (molecular weight: 218.1) and 1 mol of 3,4'-oxydianiline (molecular weight: 200.2), was imidized. The imide group density of polyimide (molecular weight per unit: 382.2) is 0.37, which is the value obtained by dividing 140.1 by 382.2.

Non-thermoplastic polyimides are 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, paraphenylenediamine, 4,4'-bis (4-aminophenoxy) biphenyl, 2,2'-dimethyl-. 4,4'-Diaminobiphenyl, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 4,4 '-Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-(1,3-phenylenediisopropyridene) bisaniline, 2,2'-n-propyl-4,4'-diaminobiphenyl and 4-amino Multiple aromatic diamines selected from the group consisting of phenyl-4'-aminobenzoate, pyromellitic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,3. 3', 4'-biphenyltetracarboxylic acid dianhydride, 2,3,2', 3'-biphenyltetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, 3,3', 4, 4'-Benzenephenone tetracarboxylic acid dianhydride, 1,4-phenylenebis (trimellitic acid monoester) dianhydride, p-phenylenebis (tritate anhydride), 1,4-phenylenebis (trimellitic acid monoester) ) A plurality of aromatics selected from the group consisting of dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic acid dianhydride, and 2,3,6,7-naphthalenetetracarboxylic acid dianhydride. It preferably contains a unit formed from the group acid benzene. In this case, the non-thermoplasticity of the non-thermoplastic polyimide is improved, and not only the adhesion of the present film is further improved, but also the water absorption rate tends to be significantly lowered.
The non-thermoplastic polyimide preferably contains 80 mol% or more of the above units with respect to all the units. The upper limit is 100 mol%.

In addition, non-thermoplastic polyimides include metaphenylenediamine, 1,5-diaminonaphthalene, benzidine, 3,3'-dimethoxybenzidine, paraxylylene diamine, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4. , 4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 1,4-bis (3-methyl-5-aminophenyl) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4- Bis (4-aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-bis (trifluoromethyl) benzidine, 3,3'-bis (trifluoromethyl) ) Other diamines such as benzidine and 2,2-bis (4-aminophenyl) hexafluoropropane may be used as the unit monomer component. These other diamines may be used alone or in combination of two or more.

In addition, non-thermoplastic polyimides include pyromellitic acid, 2,3,6,7-naphthalenetetracarboxylic acid, pyridine-2,3,5,6-tetracarboxylic acid, 4,4'-oxydiphthalic acid, 3,3. ', 4,4'-biphenyltetracarboxylic acid, 2,3', 3,4'-biphenyltetracarboxylic acid, 3,3', 4,4'-benzophenonetetracarboxylic acid, 5,5'-[1- Other tetracarboxylic acids such as methyl-1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (isobenzofuran-1,3-dione), 4,4'-(hexafluoroisopropylidene) diphthalic acid anhydride, etc. Alternatively, the derivative thereof may be used as a unit monomer component. These other tetracarboxylic acids or derivatives thereof may be used alone or in combination of two or more.

The synthesis of the polyimide precursor (polyamic acid) in producing a non-thermoplastic polyimide is preferably carried out in the presence of a solvent. Specific examples of the solvent include dimethyl sulfoxide, diethyl sulfoxide, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, N. -Vinyl-2-pyrrolidone, phenol, cresol, xylenol, halogenated phenol, catechol, hexamethylphospholamide can be mentioned.
The polyimide precursor is preferably prepared in a solution containing the polyimide precursor as a solid content of 5 to 40% by weight. In this case, the viscosity of the solution is preferably 100 to 1000 Pa · s. Further, a part of the polyimide precursor may be imidized in the solution.

Examples of the styrene elastomer include styrene-butadiene copolymer, hydrogenated-styrene-butadiene copolymer, hydrogenated-styrene-isoprene copolymer, styrene-butadiene-styrene block copolymer, and styrene-isoprene-styrene block copolymer. Examples thereof include a hydrogenated product of a styrene-butadiene-styrene block copolymer, a hydrogenated product of a styrene-isoprene-styrene block copolymer, and the like.
The D50 of the AR particles in the present invention is 1 to 10 μm, more preferably 2 to 7 μm. In this case, when forming the melt-kneaded product, it is easy to smoothly mix with the first F particles.
Examples of the aromatic polyetherketone include polyetherketone, polyetheretherketone, polyetherketoneketone, and polyetheretherketoneketone.

The definition and scope of the second F polymer in the present invention are the same as those of the first F polymer, including preferred embodiments. In addition, the definition and scope of the second F particle are the same as those of the first F particle, including preferred embodiments.
As described above, the second F polymer is preferably the same F polymer as the first F polymer.
The second F particle is preferably in the form of pellets.

The melt-kneaded product in this method is obtained by melt-kneading the first F particles and AR particles. The melt-kneaded product is obtained, for example, by charging the first F particles and AR particles into an extruder and kneading the mixture of the first F particles and AR particles in the extruder while melting the mixture by heating. .. The first F particles and AR particles may be mixed in advance with a blender and charged into the extruder.
The melt-kneaded product is preferably in the form of pellets. In such a case, an island domain having a target domain diameter is likely to be formed in this film. Therefore, this film can exhibit more excellent UV processability.

As the melt extrusion molding in this method, it is preferable to use the die coating method (melt extrusion molding by T-die). Specifically, the die coat method is performed as follows.
First, the melt-kneaded product of the first F particles and the AR particles and the second F particles are put into the extruder connected to the T die. Next, in the extruder, the mixture of the melt-kneaded product and the second F particles is kneaded while being melted by heating to obtain a melt-kneaded product.
Next, this melt-kneaded product is supplied into the T-die and discharged from the lip (discharge port) of the T-die. After that, the discharged melt-kneaded product is cooled and formed into a film by contacting with the first cooling roll arranged vertically below the T-die. Next, the melt-kneaded product formed into a film is conveyed while being in contact with other cooling rolls and transport rolls arranged further downstream, and finally is taken up by a take-up roll as the present film.

It is preferable that the melt-kneaded product of the first F particles and the AR particles and the second F particles are mixed in advance with a blender and charged into the extruder.
The temperature of the first cooling roll is preferably 150-250 ° C. In this case, since the melt-kneaded product can be rapidly cooled, small spherulites of the F polymer are likely to be formed in the present film, and therefore island domains having an appropriate domain diameter due to the AR polymer are also likely to be formed.
From the viewpoint of enhancing this quenching effect, an air knife that blows a slit-shaped air flow from the slit nozzle to the film-formed melt-kneaded material may be provided at a position immediately after the first cooling roll.
In this case, the temperature of the air blown from the air knife is preferably 150 to 200 ° C, more preferably 170 to 200 ° C. The flow velocity of the air blown from the air knife is preferably 10 to 20 m / sec.

Further, from the same viewpoint, a non-contact heating unit may be provided to maintain the temperature of the melt-kneaded product discharged from the T-die until it comes into contact with the first cooling roll. The non-contact heating unit may be composed of, for example, a pair of heaters arranged so as to face each other, and may be configured to allow a molten kneaded product to pass between them.
In this case, when the temperature of the melt-kneaded product in the T-die is defined as A [° C.] and the temperature of the non-contact heating unit is defined as B [° C.], the absolute value (| AB |) of the difference is 70. The temperature is preferably below ° C, more preferably 30 to 50 ° C. In this case, the temperature of the melt-kneaded product can be maintained sufficiently high up to the first cooling roll while preventing deterioration of the F polymer and the AR polymer.

The obtained film contains a sea domain of F polymer (first F polymer and second F polymer) and an island domain of AR polymer, and the content of AR polymer is 10% by mass or less, and the island domain. The average domain diameter of is 1 to 10 μm. When the present film is formed to have a thickness of 25 μm, the transmittance of light rays having a wavelength of 355 nm in this film having a thickness of 25 μm is 80% or less.
The definition and scope of the F polymer in this film is similar to that of the first F polymer in this method, including suitable embodiments. In addition, the definition and scope of the AR polymer in the present film are the same as those of the AR polymer in the present method, including suitable embodiments.
As described above, this film has high UV absorption because the content of the AR polymer contains at least an island domain having an appropriate domain diameter.

The content of the AR polymer in this film is preferably 0.1 to 5% by mass, more preferably 0.3 to 4% by mass. In this case, in this film, it is possible to impart sufficiently high UV absorption while preventing the properties (electrical properties, etc.) based on the F polymer from deteriorating.
The average domain diameter of the island domain is preferably 3 to 7 μm. In this case, since the light rays (UV) can be effectively penetrated by the film (island domain), the UV absorption of the film is further improved.

The transmittance of light having a wavelength of 355 nm (hereinafter, also referred to as “light transmittance”) in this film having a thickness of 25 μm is preferably 70% or less, more preferably 60% or less. The lower limit of the light transmittance is 0%. In this case, it can be determined that this film has sufficiently high UV absorption.
Further, in the plane of the extruded film having a thickness of 25 μm, the difference between the maximum value and the minimum value of the light transmittance is preferably 7% or less, more preferably 5% or less. In this case, it can be determined that this film has homogeneous properties. The lower limit of the difference between the maximum value and the minimum value of the light transmittance is usually 1% or more.

The thickness of the present film is preferably more than twice, more preferably more than four times, and even more preferably more than six times the average domain diameter of the island domain. The thickness of this film is preferably 15 times or less, more preferably 10 times or less, the average domain diameter of the island domain. In this case, the UV absorption of this film can be further enhanced.
The specific thickness of this film is preferably 5 to 150 μm, more preferably 10 to 100 μm, and even more preferably 20 to 50 μm.

The film may contain components other than the two F-polymers and AR polymers. In this method, other components may be mixed with the melt-kneaded product, the second F particles, or both the melt-kneaded product and the second F particles.
Other components include inorganic fillers, organic fillers, resins other than the above polymers, thixo-imparting agents, defoaming agents, silane coupling agents, dehydrating agents, plasticizers, weather resistant agents, antioxidants, heat stabilizers. , Lubricants, antistatic agents, whitening agents, colorants, conductive agents, mold release agents, surface treatment agents, viscosity modifiers, flame retardants and the like.

The inorganic filler is preferably a nitride filler or an inorganic oxide filler, and is preferably a boron nitride filler, a beryllia filler (a filler of an oxide of beryllium), a silicate filler (silica filler, a wollastonite filler, a talc filler), or a metal. Oxide (cerium oxide, aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, etc.) fillers are more preferable, and silica fillers are even more preferable.
At least a part of the surface of the inorganic filler is a silane coupling agent (3-aminopropyltriethoxysilane, vinyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3). -It is preferable that the surface is treated with (methacryloxypropyltriethoxysilane, 3-isocyandiapropyltriethoxysilane, etc.).

The D50 of the inorganic filler is preferably 20 μm or less, more preferably 10 μm or less. The D50 is preferably 0.01 μm or more, more preferably 0.1 μm or more.
The shape of the inorganic filler may be granular, needle-shaped (fibrous), or plate-shaped. Specific shapes of the inorganic filler include spherical, scaly, layered, leafy, apricot kernel, columnar, chicken crown, equiaxed, leafy, mica, block, flat plate, wedge, rosette, and mesh. The shape and the prismatic shape can be mentioned.
As the inorganic filler, one kind may be used alone, or two or more kinds may be used in combination.

Suitable specific examples of the inorganic filler include silica filler (“Admafine (registered trademark)” series manufactured by Admatex Co., Ltd.), zinc oxide surface-treated with an ester such as propylene glycol dicaprate (Sakai Chemical Industry Co., Ltd.). "FINEX (registered trademark)" series manufactured by Ishihara Sangyo Co., Ltd.), spherical molten silica ("SFP (registered trademark)" series manufactured by Denka Co., Ltd., etc.), coated with polyhydric alcohol and inorganic substances ("Typake" manufactured by Ishihara Sangyo Co., Ltd. (Registered trademark) "series, etc.), rutile-type titanium oxide surface-treated with alkylsilane ("JMT (registered trademark) "series manufactured by Teika Co., Ltd.), hollow silica filler ("E-SPHERES" manufactured by Pacific Cement Co., Ltd.) Series, "Sirinax" series manufactured by Nittetsu Mining Co., Ltd., "Ecocos Fire" series manufactured by Emerson & Cumming, etc.), Tarkufiller ("SG" series manufactured by Nippon Tarku Co., Ltd., etc.), Steatite Filler (Nippon Tarku) "BST" series manufactured by Denka Co., Ltd.), boron nitride filler ("UHP" series manufactured by Showa Denko Co., Ltd., "Denka Boron Nightride" series manufactured by Denka Co., Ltd. ("GP", "HGP" grade), etc.). ..

Other resins include epoxy resin, acrylic resin, phenol resin, polyolefin resin, modified polyphenylene ether resin, polyfunctional cyanic acid ester resin, polyfunctional maleimide-cyanic acid ester resin, polyfunctional maleimide resin, vinyl ester resin, urea. Examples thereof include resin, diallyl phthalate resin, melanin resin, guanamine resin, melamine-urea cocondensation resin, polycarbonate resin, polyarylate resin, polysulfone, and polyallylsulfone.

By heat-pressing the film and the metal foil, a metal-clad laminate having a polymer layer and a metal foil layer can be manufactured.
The metal-clad laminate may include layers other than the polymer layer and the metal foil layer. Examples of the other layer include a heat-resistant resin layer.
Specific examples of the layer structure of the metal-clad laminate include a metal foil layer / polymer layer / heat-resistant resin layer, a metal foil layer / polymer layer / heat-resistant resin layer / polymer layer / metal foil layer, and a metal foil layer / heat-resistant layer. Examples thereof include a sex resin layer / a polymer layer / a heat-resistant resin layer / a metal foil layer.
As the metal foil, copper foil is preferable. Examples of the copper foil include rolled copper foil and electrolytic copper foil. The copper foil may be formed with a rust preventive layer such as zinc chromate and a barrier layer such as nickel and cobalt. Further, the barrier layer may be formed by a plating treatment or a chemical conversion treatment.

From the viewpoint of improving the adhesion between the metal foil layer and the polymer layer, the surface of the metal foil layer may be treated with a silane coupling agent. Examples of the silane coupling agent include epoxysilane, aminosilane, vinylsilane, acryloxysilane, methacrylicoxysilane, ureidosilane, mercaptosilane, sulfidesilane and isocyanatesilane, and acryloxysilane, methacrylatesilane and epoxysilane are preferable. One type of silane coupling agent may be used, or two or more types may be used in combination.
The Rzjis on the surface of the metal foil layer on the polymer layer side is preferably 0.3 to 1.6. When Rzjis is 0.3 or more, delamination is unlikely to occur between the metal foil layer and the polymer layer during drilling with a UV-YAG laser. When Rzjis is 1.6 or less, an increase in transmission loss due to roughness can be suppressed.
The thickness of the metal foil layer is preferably 3 to 18 μm, more preferably 6 to 12 μm.

The dielectric loss tangent of the polymer layer is preferably 0.0005 to 0.0040, more preferably 0.0007 to 0.0030. The lower the dielectric loss tangent, the better the electrical properties of the polymer layer.
The thickness of the polymer layer is preferably 1 to 50 μm, more preferably 2 to 25 μm. When the thickness of the polymer layer is at least the above lower limit value, it is easy to obtain a printed wiring board having a small transmission loss. When the thickness of the polymer layer is not more than the above upper limit value, the UV processability is further improved. When the metal-clad laminate has a plurality of polymer layers, it is preferable that the thickness of each is within the above range.

Examples of the constituent material (heat-resistant resin material) of the heat-resistant resin layer include polyimide, liquid crystal polymer, polyether ether ketone, polyphenylene oxide, polyester, polyamide, and aramid fiber. Among them, as the heat-resistant resin material, at least one selected from the group consisting of polyimide, liquid crystal polymer, polyetheretherketone, polyphenylene oxide and aramid fiber is preferable, and polyimide or liquid crystal polymer is more preferable.
From the viewpoint of enhancing UV processability, the heat-resistant resin layer preferably contains less dissimilar materials, and is preferably composed of the non-thermoplastic polyimide alone.
When the metal-clad laminate has a heat-resistant resin layer, the ratio of the thickness of the polymer layer (total thickness in the case of a plurality of cases) to the thickness of the heat-resistant resin layer (total thickness in the case of a plurality of cases) is 0. 5 to 2 is preferable. In this case, the polymer layer can be easily drilled by the UV-YAG laser, and the transmission loss can be easily reduced.

The thickness of the metal-clad laminate is preferably 10 to 150 μm, more preferably 15 to 100 μm, still more preferably 20 to 50 μm. In this case, the metal-clad laminate can be used more stably as a printed wiring board, and a through hole can be easily formed by a UV-YAG laser.
The opening shape of the through hole is preferably a circular shape. In this case, the diameter can be set in the range of 0.05 to 0.10 mm.
The number of through holes may be one or two or more.
A plating layer may be formed on the inner wall surface of the through hole, if necessary. For example, when the printed wiring board has conductors on both sides in the thickness direction, if a plating layer is formed on the inner wall surface of the through hole, conduction between the conductors can be ensured.

Examples of the plating layer include a copper plating layer, a gold plating layer, a nickel plating layer, a chrome plating layer, a zinc plating layer, and a tin plating layer.
The transmission loss is a parameter representing the attenuation of the signal from the input unit to the output unit of the signal in the printed wiring board.
The transmission loss of the printed wiring board is preferably −0.07 dB / mm or more, and more preferably −0.06 dB / mm or more at 40 GHz.

The printed wiring board can be manufactured by a method of forming through holes in the metal-clad laminate by drilling holes by irradiating the metal-clad laminate with a UV-YAG laser.
The wavelength of the UV-YAG laser is preferably a third harmonic (wavelength 355 nm) or a fourth harmonic (266 nm).
A UV-YAG laser processing machine can be used for drilling. Trepanning can be used for drilling with a UV-YAG laser. Specifically, it is possible to form a through hole by partially hollowing out the metal-clad laminate by irradiating the laser with a narrowed diameter while orbiting along the peripheral edge of the portion where the through hole should be formed.

The laser output, the number of laser irradiation laps, and the laser oscillation frequency can be set according to the thickness of the metal-clad laminate.
When a laser beam having a wavelength of 355 nm is used, the output is preferably 0.1 to 3.0 W, more preferably 0.5 to 2.0 W. When a laser beam having a wavelength of 266 nm is used, the output is preferably 0.01 to 0.5 W, more preferably 0.05 to 0.3 W. In this case, the formation of through holes becomes easy, and the amount of resin scattered due to the heat of the laser can be reduced.
The number of laps of laser irradiation is preferably 5 to 50 times.
When a laser beam having a wavelength of 355 nm is used, the oscillation frequency is preferably 20 to 80 kHz. When a laser beam having a wavelength of 266 nm is used, the oscillation frequency is preferably 1 to 10 kHz.

The metal-clad laminate has a polymer layer made of this film having a predetermined sea-island structure, and the transmittance of light rays having a wavelength of 355 nm is controlled. For this reason, the polymer layer has an increased absorption rate of the UV-YAG laser without the use of additives, and as a result, the UV-YAG laser can easily penetrate a small diameter while suppressing deterioration of the electrical characteristics. Can form holes.
The printed wiring board manufactured in this way can be suitably used for high frequency applications.

Although the method for producing the extruded film and the extruded film of the present invention have been described above, the present invention is not limited to the configuration of the above-described embodiment.
For example, the method for producing an extruded film of the present invention may additionally have any other step in the configuration of the above embodiment, or may be replaced with any step that produces the same action.
In addition, the extruded film of the present invention may additionally have any other configuration in the configuration of the above embodiment, or may be replaced with any configuration that produces the same effect.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.
1. 1. Preparation of each component [F particle]
F particle 1: F polymer 1 containing 97.9 mol%, 0.1 mol%, 2.0 mol% of TFE unit, NAH unit and PPVE unit in this order and having a polar functional group (melting temperature: 300 ° C., Powdery particles (D50: 2.1 μm) consisting of MFR: 28 g / 10 min)
F particle 2: F polymer 2 containing 97.9 mol%, 0.1 mol%, 2.0 mol% of TFE unit, NAH unit and PPVE unit in this order and having a polar functional group (melting temperature: 300 ° C., Pellet-shaped particles consisting of MFR: 22 g / 10 min) F particles 3: F polymer 3 (melting temperature) containing 97.5 mol% and 2.5 mol% of TFE units and PPVE units in this order and having no polar functional group. Powdery particles (D50: 2.3 μm) consisting of 305 ° C., MFR: 28 g / 10 min)
F particle 4: Pellet composed of F polymer 4 (melting temperature 305 ° C., MFR: 22 g / 10 min) containing 97.5 mol% and 2.5 mol% of TFE units and PPVE units in this order and having no polar functional group. Particles in the form F particles 5: F polymer 5 containing 97.5 mol% and 2.5 mol% of TFE units and PPVE units in this order and having no polar functional group (melting temperature 305 ° C., MFR: 16 g / 10 min). Pellet-like particles consisting of

[AR particles]
AR particles 1: Particles of non-thermoplastic polyimide (Tg: 337 ° C.) (D50: 3 μm, “P84NT superfine” manufactured by Daicel Evonik).
AR particles 2: Non-thermoplastic polyimide (Tg: 355 ° C.) particles (D50: 13 μm, “UIP-SA” manufactured by Ube Industries, Ltd.)
[Copper foil]
Copper foil 1: Low-roughened copper foil (thickness: 12 μm, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., “CF-T49A-DS-HD2)

2. 2. Film production example [Example 1]
F particles 1 (90 parts by mass) and AR particles (10 parts by mass) were stirred with a blender to prepare a mixture. The mixture was melt-kneaded (screw rotation speed: 200 rpm, set resin temperature: 370 ° C.) using a twin-screw extruder (“KZW15TW-45MG” manufactured by Technobel Co., Ltd.) to produce pellet 1. The MFR of pellet 1 was 24 g / 10 min.
Pellets 1 (10 parts by mass) and F particles 2 (90 parts by mass) were stirred with a blender to prepare a mixture. The mixture was extruded at a die temperature of 340 ° C. using a single-screw extruder (a 30 mmφ single-screw extruder having a 700 mm wide coated hanger die) to obtain a film 1 having a width of 500 mm, a length of 100 m, and a thickness of 25 μm. The average domain diameter of the island domain in film 1 was 3 μm.
The average domain diameter is determined by determining the island domain by image processing from an SEM photograph of a cross section of a film observed using a scanning electron microscope (SEM).

[Examples 2 to 6]
Pellets 2 to 5 were obtained in the same manner as in pellet 1 except that the types and amounts of F particles and AR particles were changed as shown in Table 1.
Films 2 to 6 were obtained in the same manner as in Film 1, except that the types and amounts of pellets and F particles were changed as shown in Table 2.
[Example 7]
F particles 2 (99 parts by mass) and AR particles 1 (1 part by mass) were stirred with a blender to prepare a mixture. The mixture was extruded using a single-screw extruder (a 30 mmφ single-screw extruder having a 750 mm wide coated hanger die) at a die temperature of 340 ° C. to obtain a film 7 having a width of 500 mm, a length of 100 m, and a thickness of 25 μm. ..

The components of films 1 to 7, the difference in MFR between each pellet and F particles, the content of AR polymer in the film, and the average domain diameter of the island domain are also shown in Table 2. Since the island domain did not exist in the film 6 and the pellet was not used in the film 7, there is no difference in MFR between the pellet and the F particle.

3. 3. Production of Laminated Body A copper foil 1 was laminated on the surface of the film 1 and vacuum heat pressed to obtain a laminated body 1. The treatment conditions were temperature: 340 ° C., pressurizing pressure: 3.0 MPa, and pressurizing time: 20 minutes.
Laminated bodies 2 to 7 were obtained in the same manner as the laminated body 1 except that the film 1 was changed to films 2 to 6.

4. Evaluation 4-1. Evaluation of film 4-1-1. Evaluation of Light Transparency The transmittance of ultraviolet rays having a wavelength of 355 nm of the obtained film was measured using a spectrophotometer (“UV-3600” manufactured by Shimadzu Corporation). Further, the transmittance of the ultraviolet rays was measured at 3 points in the width direction of the film and every 5 m in the longitudinal direction at a total of 60 points, and the difference between the maximum value and the minimum value was obtained.

4-1-2. Evaluation of Electrical Characteristics The obtained film was measured for its dielectric loss tangent (measurement frequency: 10 GHz) by the SPDR (split post dielectric resonance) method.
[Evaluation criteria]
〇: The dielectric loss tangent is less than 0.0010.
Δ: The dielectric loss tangent is 0.0010 or more and 0.0040 or less.
X: The dielectric loss tangent is more than 0.0040.

4-2. Evaluation of laminated body 4-2-1. Evaluation of UV Processability (UV Laser Processability) A laser processing machine (esi5330) was used to irradiate the laminate with a UV-YAG laser having a wavelength of 355 nm so as to orbit around a circumference of 100 μm in diameter. .. As a result, a circular through hole was formed in the laminated body. The laser output was 1.5 W, the laser focal diameter was 25 μm, the number of orbits on the circumference was 16, and the oscillation frequency was 40 kHz.
Then, a fragment of the laminate including the through hole was cut out and hardened with a thermosetting epoxy resin. Then, polishing was performed until the cross section of the through hole was exposed. The peripheral cross sections of the 100 through holes were observed with a microscope, and the presence or absence of scraping and peeling at the layer interface was confirmed and evaluated according to the following criteria.
[Evaluation criteria]
〇: No shaving or peeling in all through holes Δ: 1 or more and 5 or less through holes have shaving and peeling ×: More than 5 through holes have shaving and peeling The evaluation results are summarized in Table 3.

Claims (14)

A melt-kneaded product of first tetrafluoroethylene polymer particles having a melting temperature of 270 to 320 ° C. and aromatic polymer particles having an average particle diameter of 1 to 10 μm, and a second melt kneaded product having a melting temperature of 270 to 320 ° C. A method for producing an extrusion-molded film, wherein a mixture with particles of a tetrafluoroethylene polymer is melt-extruded to obtain an extrusion-molded film containing the aromatic polymer in an amount of 10% by mass or less. The first tetrafluoroethylene polymer and the second tetrafluoroethylene polymer each independently contain a unit based on perfluoro (alkyl vinyl ether) and have a polar functional group, or all of them. The production method according to claim 1, which is a tetrafluoroethylene-based polymer containing 2.0 to 5.0 mol% of units based on perfluoro (alkyl vinyl ether) with respect to the units and having no polar functional group. The production method according to claim 1 or 2, wherein the first tetrafluoroethylene polymer and the second tetrafluoroethylene polymer are the same tetrafluoroethylene polymer. The production method according to any one of claims 1 to 3, wherein the aromatic polymer is a non-thermoplastic polyimide. The production method according to any one of claims 1 to 4, wherein the glass transition temperature of the aromatic polymer is in the range of the melting temperature of the first tetrafluoroethylene polymer + 20 ° C. or higher. The production method according to any one of claims 1 to 5, wherein the melt flow rate of the second tetrafluoroethylene polymer is in the range of ± 7 g / 10 minutes of the melt flow rate of the melt-kneaded product. The item according to any one of claims 1 to 6, wherein the content of the aromatic polymer in the melt-kneaded product is 5 to 30 parts by mass with respect to 100 parts by mass of the first tetrafluoroethylene-based polymer. The manufacturing method described. The production method according to any one of claims 1 to 7, wherein in the mixture, the mixing ratio of the particles of the second tetrafluoroethylene polymer to the melt-kneaded product by mass is 5 to 20. .. An extruded film containing a sea domain of a tetrafluoroethylene-based polymer having a melting temperature of 270 to 320 ° C. and an island domain of an aromatic polymer, wherein the content of the aromatic polymer in the extruded film is 10. The extruded film having an average domain diameter of 1 to 10 μm or less and having a thickness of 25 μm and having an average domain diameter of 1 to 10 μm and having a light transmittance of 80% or less at a wavelength of 355 nm in the extruded film having a mass% or less and a thickness of 25 μm. .. The tetrafluoroethylene-based polymer contains a unit based on perfluoro (alkyl vinyl ether) and has a polar functional group, or a tetrafluoroethylene-based polymer having a polar functional group, or 2.0 to 2.0 to all units based on perfluoro (alkyl vinyl ether). The extrusion-molded film according to claim 9, which is a tetrafluoroethylene-based polymer containing 5.0 mol% and having no polar functional group. The extruded film according to claim 9 or 10, wherein the aromatic polymer is a non-thermoplastic polyimide. The extruded film according to any one of claims 9 to 11, wherein the content of the aromatic polymer is 0.1 to 5% by mass. The extrusion-molded film according to any one of claims 9 to 12, wherein the difference between the maximum value and the minimum value of the transmittance is 7% or less in the plane of the extrusion-molded film having a thickness of 25 μm. The extruded film according to any one of claims 9 to 13, wherein the thickness of the extruded film is more than twice the average domain diameter of the island domain.