Manufacturing method of long substrate

Abstract

To provide a manufacturing method for a lengthy substrate having a polymer layer including tetrafluoroethylene-system polymer, which does not cause stripes or the like, is excellent in surface nature and is excellent in adhesion to a substrate such as a polyimide film.SOLUTION: In the manufacturing method for a lengthy substrate, a liquid composition as coating liquid, which contains particles of a tetrafluoroethylene-system polymer whose average particle size is below 10 μm, whose shear viscosity at a temperature of 25°C and at a shear speed of 2.6 sec-1 is 1000-10000 mPa.s and whose shear viscosity at a temperature of 25°C and at a shear speed of 52.8 sec-1 is 200-1500 mPa.s is jetted from the nozzle head to a lip coater-type coating apparatus in which a nozzle head having a doctor edge is arranged on a surface of a backing roll on which a substrate runs in a longitudinal direction and which is configured to make the nozzle head jet the coating liquid by pressurization and make the doctor edge apply the coating liquid to the substrate, while running the substrate to coat the surface of the substrate with the liquid, so as to obtain a lengthy substrate having a coated layer formed of the liquid composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a long substrate having a polymer layer containing a tetrafluoroethylene-based polymer formed on the surface of the substrate. [Background technology]

[0002] Tetrafluoroethylene polymers such as polytetrafluoroethylene (PTFE) have excellent physical properties such as electrical properties, water and oil repellency, chemical resistance, and heat resistance, and laminates having layers thereof are used in various fields. For example, a three-layer laminate using a polyimide film as a base material and having a layer containing a tetrafluoroethylene-based polymer on each side thereof combines the molding characteristics and mechanical properties of polyimide with the electrical characteristics and heat resistance, such as a low dielectric constant and a low dielectric dissipation factor, of a tetrafluoroethylene-based polymer, and is useful as a material for use in high-end electrical and electronic fields, such as printed circuit boards and wire coatings that are compatible with high-frequency bands (see Patent Document 1). A dispersion containing particles of a tetrafluoroethylene-based polymer is known as a coating agent used to impart the above-mentioned physical properties to the surface of a substrate, and Patent Document 2 discloses that an aqueous dispersion of a fluorine-based resin is applied to one or both sides of a resin film and heated to form a laminate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 039735 [Patent Document 2] Japanese Patent Application Publication No. 09-157418 Summary of the Invention [Problem to be solved by the invention]

[0004] From the viewpoint of efficiently producing a laminate having a layer containing a tetrafluoroethylene-based polymer on at least one surface of a substrate, it is preferable to form a tetrafluoroethylene-based polymer layer by applying a dispersion containing tetrafluoroethylene-based polymer particles to the surface of a substrate such as a resin film using a continuous production process such as roll-to-roll. However, the present inventors have found that such a polymer layer is prone to cracks and streaks and its adhesion to the substrate is easily reduced.

[0005] As a result of extensive research, the present inventors have found that when a liquid composition having specific properties, which contains particles of a tetrafluoroethylene-based polymer, is applied to a substrate using a lip coater-type coating device, cracks and streaks do not occur in the polymer layer containing the tetrafluoroethylene-based polymer formed on the surface of the substrate, even in a continuous production process such as roll-to-roll, and a long substrate having a thick polymer layer which has excellent electrical properties such as a low dielectric loss tangent, a low coefficient of linear expansion, and excellent adhesion to the substrate can be produced with good productivity. An object of the present invention is to provide a method for producing a long substrate having a polymer layer containing a tetrafluoroethylene-based polymer, which has an excellent surface quality without streaks and has excellent adhesion to substrates such as polyimide films. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] A nozzle head having a doctor edge is arranged on the surface of a backing roll on which a substrate travels in the forward and backward directions, and a coating liquid is sprayed from the nozzle head by pressure, and the coating liquid is applied to the substrate by the doctor edge. While the substrate is traveling through a lip coater type coating device, the coating liquid contains particles of a tetrafluoroethylene-based polymer having an average particle diameter of 10 μm or less, and is applied at a temperature of 25 ° C and a shear rate of 2.6 sec -1 The shear viscosity is 1000-10000 mPa·s at a temperature of 25°C and a shear rate of 52.8 sec -1a liquid composition having a shear viscosity of 200 to 1500 mPa s at 20 ... [2] The temperature is 25°C and the shear rate is 2.6 seconds. -1 Shear viscosity at 25°C and a shear rate of 52.8 sec -1 The manufacturing method of [1], wherein the ratio of shear viscosity in [3] The method of producing [1] or [2], wherein the tetrafluoroethylene-based polymer is a heat-fusible tetrafluoroethylene-based polymer. [4] The method according to any one of [1] to [3], wherein the tetrafluoroethylene polymer is a tetrafluoroethylene polymer having an oxygen-containing polar group. [5] The manufacturing method according to any one of [1] to [4], wherein the liquid composition further contains at least one resin selected from polyimide, polyamideimide, polyetherimide, and maleimide. [6] The method according to any one of [1] to [5], wherein the liquid composition further contains at least one liquid dispersion medium selected from water, ketones, and amides. [7] The method according to any one of [1] to [7], wherein the liquid composition further contains at least one thickener polymer selected from an acrylic thickener, a cellulose thickener, or a polyvinyl alcohol thickener. [8] The method according to any one of [1] to [7], wherein the liquid composition further contains an inorganic filler. [9] The method according to any one of [1] to [8], wherein the liquid composition further contains a nonionic surfactant.

[10] The manufacturing method according to any one of [1] to [9], wherein the content of the tetrafluoroethylene polymer particles in the liquid composition is 20 to 50 mass %.

[11] The method according to any one of [1] to

[10] , wherein the substrate is a polyimide film, a liquid crystal polymer film, a polytetrafluoroethylene film, or a copper foil.

[12] The manufacturing method according to any one of [1] to

[11] , wherein the coating layer has a thickness of 20 μm to 250 μm.

[13] A method for producing a long substrate, comprising further drying and baking a long substrate having a coating layer made of the liquid composition obtained by the production method of any one of [1] to

[12] , to obtain a long substrate having a polymer layer containing the tetrafluoroethylene-based polymer on the surface of the substrate.

[0007]

[14] A nozzle head having a doctor edge is arranged on the surface of a backing roll on which a substrate travels in the forward and backward directions, and a coating liquid is sprayed from the nozzle head by pressure, and the coating liquid is applied to the substrate by the doctor edge. While the substrate is traveling through a lip coater type coating device, the coating liquid contains particles of a tetrafluoroethylene-based polymer having an average particle diameter of 10 μm or less, and is applied at a temperature of 25 ° C and a shear rate of 2.6 sec -1 The shear viscosity is 1000-10000 mPa·s at a temperature of 25°C and a shear rate of 52.8 sec -1 a liquid composition having a shear viscosity of 200 to 1500 mPa s at 2000 kJ / min is sprayed from the nozzle head to coat the surface of the substrate, thereby obtaining a long substrate having a coating layer formed from the liquid composition; the long substrate is further dried and baked to obtain a long substrate having a polymer layer containing the tetrafluoroethylene-based polymer on the surface of the substrate; the obtained long substrate having the polymer layer is wound up; and while the long substrate having the polymer layer is unwound and allowed to run on the lip coater-type coating device, the liquid composition is sprayed from the nozzle head as the coating liquid to coat the surface of the substrate opposite to the surface having the polymer layer; and further dried and baked to obtain a long substrate having polymer layers containing the tetrafluoroethylene-based polymer on both surfaces of the substrate.

[15] A nozzle head having a doctor edge is arranged on the surface of a backing roll on which a substrate travels in the forward and backward directions, and a coating liquid is sprayed from the nozzle head by pressure, and the coating liquid is applied to the substrate by the doctor edge. While the substrate is traveling through a lip coater type coating device, the coating liquid contains particles of a tetrafluoroethylene-based polymer having an average particle diameter of 10 μm or less, and is applied at a temperature of 25 ° C and a shear rate of 2.6 sec -1 The shear viscosity is 1000-10000 mPa·s at a temperature of 25°C and a shear rate of 52.8 sec -1 a liquid composition having a shear viscosity of 200 to 1500 mPa s at 2000 kJ / s is sprayed from the nozzle head to coat the surface of the substrate, thereby obtaining a long substrate having a coating layer formed from the liquid composition; the long substrate is further dried and baked to obtain a long substrate having a polymer layer containing the tetrafluoroethylene-based polymer on the surface of the substrate; while the long substrate having the polymer layer is traveling through another lip coater-type coating device, the liquid composition is sprayed from the nozzle head as the coating liquid to coat the surface of the substrate opposite to the surface having the polymer layer, and further dried and baked to obtain a long substrate having polymer layers containing the tetrafluoroethylene-based polymer on both surfaces of the substrate. [Effects of the Invention]

[0008] According to the present invention, a long substrate having a polymer layer containing a tetrafluoroethylene-based polymer, which is free from streaks and has an excellent surface property, and which has excellent adhesion to substrates such as polyimide films, can be produced with good productivity. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following terms have the following meanings: The "glass transition temperature (Tg) of a polymer" is a value measured by analyzing a polymer using dynamic mechanical analysis (DMA). The "melting temperature (melting point) of a polymer" is the temperature corresponding to the maximum value of the melting peak measured by differential scanning calorimetry (DSC). "D50" is the average particle size of particles, and is the cumulative 50% diameter based on the volume of an object determined by laser diffraction / scattering. In other words, the particle size distribution of an object is measured by laser diffraction / scattering, the total volume of the object group is set to 100%, and a cumulative curve is calculated. D50 is the particle size at the point on the cumulative curve where the cumulative volume is 50%. The "specific surface area" is a value calculated by measuring particles using the gas adsorption (constant volume method) BET multipoint method, and is determined using a NOVA4200e (manufactured by Quantachrome Instruments). The "shear viscosity" is a value measured for a liquid composition using a Brookfield viscometer at room temperature (25°C) and a specified rotation speed. The measurement is repeated three times, and the average value of the three measurements is used. The term "unit based on a monomer" refers to an atomic group based on the monomer formed by polymerization of the monomer. The unit may be a unit formed directly by the polymerization reaction, or may be a unit in which a part of the unit is converted into a different structure by treating the polymer. Hereinafter, a unit based on monomer a may also be simply referred to as a "monomer a unit."

[0010] The manufacturing method of the present invention (hereinafter also referred to as "this method") is a lip coater type coating device (hereinafter also simply referred to as "lip coater type coating device") that has a nozzle head having a doctor edge disposed on the surface of a backing roll on which a substrate travels in the forward and backward directions, and a coating liquid is sprayed from the nozzle head under pressure by a coating liquid supply means, and the coating liquid is applied to the substrate by the doctor edge. While the substrate is traveling through the lip coater type coating device, the coating liquid contains particles (hereinafter also referred to as "F particles") of a tetrafluoroethylene-based polymer (hereinafter also referred to as "F polymer") having an average particle size of 10 μm or less, and the coating liquid is applied to the substrate at a temperature of 25° C. and a shear rate of 2.6 sec. -1 The shear viscosity at 25°C and a shear rate of 52.8 sec (hereinafter also referred to as "shear viscosity 1") is 1000 to 10000 mPa·s. -1a liquid composition (hereinafter also referred to as "the composition") having a shear viscosity at 200 to 1500 mPa·s (hereinafter also referred to as "shear viscosity 2") is sprayed from the nozzle head to coat the surface of the substrate, thereby obtaining a long substrate having a coating layer formed from the liquid composition. This method allows for the efficient production of long substrates with thick polymer layers that are free of streaks in the polymer layer containing F polymer formed on the surface of the substrate, even in continuous production processes such as roll-to-roll. The polymer layer also has excellent electrical properties such as low dielectric loss tangent, a low coefficient of linear expansion, and excellent adhesion to the substrate. The reasons for this are not entirely clear, but are thought to be as follows.

[0011] When applied to a continuous production process, a method of applying a coating liquid to a substrate surface using a reverse roll coater, air knife coater, knife coater, or the like to produce a laminate having a coating layer and a substrate layer, or a method of forming a coating layer on a substrate by a dip coating method, is prone to problems such as unevenness and streaks on the coated surface and is also likely to increase the burden on the equipment. On the other hand, coating methods using lip coater-type coating devices are mechanically advantageous in that they tend to suppress dripping and air entrainment in the coating area, and are therefore generally less likely to result in streaks in the coating layer running along the substrate. However, F polymers have low surface tension and poor affinity with other materials in the coating solution. Furthermore, their particles have poor dispersion stability and are fibrillar themselves. Therefore, liquid compositions containing particularly fine F particles are difficult to apply to coating using lip coater-type coating devices, and even if they were applied, the above problems would not be solved. In this method, the particle size of the F particles that make up this composition and the liquid properties of this composition, particularly the shear viscosity in the low shear region and the shear viscosity in the high shear region, were controlled within specific ranges. This improved the dispersibility and fluidity of the F particles in this composition, balanced the dynamic viscoelasticity of the coating liquid, and enabled the formation of a thick coating layer using a lip coater. As a result, even in continuous production processes such as roll-to-roll, the polymer layer containing tetrafluoroethylene-based polymer formed on the surface of the substrate was free of cracks and streaks. It is believed that this enabled the productive production of long substrates with thick polymer layers that exhibit excellent electrical properties such as low dielectric loss tangent, a low coefficient of linear expansion, and excellent adhesion to the substrate.

[0012] This composition was heated at a temperature of 25°C and a shear rate of 2.6 sec -1 The shear viscosity (shear viscosity 1) is 1000 to 10000 mPa·s, and the temperature is 25°C and the shear rate is 52.8 sec -1 The shear viscosity at low shear stress (shear viscosity 2) is 200 to 1500 mPa·s. Shear viscosity 1 corresponds to the shear viscosity in the low shear stress region, and shear viscosity 2 corresponds to the shear viscosity in the high shear stress region. The shear viscosity 1 is preferably 1500 mPa·s or more, more preferably 2000 mPa·s or more. The shear viscosity 1 is preferably 6000 mPa·s or less, more preferably 4000 mPa·s or less, and even more preferably 3000 mPa·s or less. The shear viscosity 2 is preferably 300 mPa·s or more, more preferably 500 mPa·s or more, and is preferably 1200 mPa·s or less, more preferably 1000 mPa·s or less.

[0013] When the composition has shear viscosities 1 and 2 within the above ranges, the composition as a coating liquid is less likely to drip from the tip of the nozzle head of a lip coater-type coating device in this method, and streaks or relatively thick streak-like patterns in the flow direction of the coated surface (hereinafter also referred to as "streaks") are less likely to occur on the coated surface. When the composition is applied to a substrate from the nozzle head of a lip coater-type coating device, some streaks may occur due to the surface tension of the composition regardless of the viscosity of the composition. However, since a fairly large shear stress is applied to the composition at the tip of the nozzle head, with a composition having a shear viscosity 2 within the above range, the strength of the streaks on the coated surface is weakened by a leveling effect, and as a result, it is thought that the occurrence of streaks on the surface after coating with a lip coater is effectively suppressed.

[0014] Furthermore, from the viewpoints of improving discharge stability when applying the present composition from the tip of the nozzle head of a lip coater-type coating device and making the resulting coating layer less prone to flow and excellent in stability, the ratio of shear viscosity 2 to shear viscosity 1 is preferably 0.05 or more and less than 0.40, and more preferably 0.1 or more and 0.3 or less.

[0015] In this method, the F polymer constituting the present composition is a polymer containing units (hereinafter also referred to as "TFE units") based on tetrafluoroethylene (hereinafter also referred to as "TFE"). The F polymer may be either heat-meltable or non-heat-meltable. Here, a heat-meltable polymer refers to a polymer at which there exists a temperature at which the melt flow rate is 1 to 1000 g / 10 min under a load of 49 N. A non-heat-meltable polymer refers to a polymer at which there does not exist a temperature at which the melt flow rate is 1 to 1000 g / 10 min under a load of 49 N. The melting temperature of the heat-meltable F polymer is preferably 180°C or higher, more preferably 200°C or higher, and even more preferably 260°C or higher. The melting temperature of the F polymer is preferably 325°C or lower, more preferably 320°C or lower. The melting temperature of the F polymer is preferably 200 to 320°C. In this case, the composition is likely to have excellent liquid physical properties such as dispersion stability, and a dense polymer layer can be easily formed from the composition.

[0016] The glass transition point of the F polymer is preferably 50° C. or higher, more preferably 75° C. or higher. The glass transition point of the F polymer is preferably 150° C. or lower, more preferably 125° C. or lower. The fluorine content of the F polymer is preferably 70% by mass or more, more preferably 72 to 76% by mass. Even in the case of an F polymer with such a high fluorine content and extremely low surface tension, the present composition tends to have excellent liquid physical properties such as dispersion stability. The surface tension of the F polymer is preferably 16 to 26 mN / m. The surface tension of the F polymer can be measured by placing a droplet of a mixture for wetting tension testing (manufactured by Wako Pure Chemical Industries, Ltd.) specified in JIS K 6768 on a flat plate made of the F polymer.

[0017] F polymer can include polytetrafluoroethylene (PTFE), the polymer that comprises TFE unit and the unit based on ethylene, the polymer that comprises TFE unit and the unit based on propylene, the polymer that comprises TFE unit and the unit based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE unit) (PFA), the polymer that comprises TFE unit and the unit based on hexafluoropropylene (FEP), the polymer that comprises TFE unit and the unit based on fluoroalkylethylene, the polymer that comprises TFE unit and the unit based on chlorotrifluoroethylene, preferably PFA or FEP, more preferably PFA.These polymers can also comprise the unit based on other comonomers. PAVE is preferably CF2=CFOCF3, CF2=CFOCF2CF3 or CF2=CFOCF2CF2CF3 (hereinafter also referred to as "PPVE"), and PPVE is more preferred.

[0018] The F polymer preferably has an oxygen-containing polar group, more preferably a hydroxyl group-containing group or a carbonyl group-containing group, and even more preferably a carbonyl group-containing group. Such an F polymer provides the present composition with excellent physical properties such as adhesiveness and excellent liquid physical properties such as dispersion stability. The hydroxyl group-containing group is preferably a group containing an alcoholic hydroxyl group, more preferably -CF2CH2OH or -C(CF3)2OH. The carbonyl group-containing group is a group containing a carbonyl group (>C(O)), and is preferably a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH), an acid anhydride residue (-C(O)OC(O)-), an imide residue (-C(O)NHC(O)-, etc.) or a carbonate group (-OC(O)O-), more preferably an acid anhydride residue. When the F polymer has an oxygen-containing polar group, the number of oxygen-containing polar groups in the F polymer is 1×10 6 The number per unit is preferably 10 to 5000, more preferably 100 to 3000. The number of oxygen-containing polar groups in the F polymer can be quantified based on the polymer composition or the method described in WO 2020 / 145133.

[0019] The oxygen-containing polar group may be contained in a monomer unit in the F polymer or in a terminal group of the main chain of the F polymer, the former being preferred. Examples of the latter include an F polymer having an oxygen-containing polar group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc., and an F polymer obtained by subjecting an F polymer to plasma treatment or ionizing radiation treatment. The monomer having a carbonyl group-containing group is preferably itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and more preferably NAH.

[0020] The F polymer is preferably a polymer having a carbonyl group-containing group containing TFE units and PAVE units, more preferably a polymer containing TFE units, PAVE units, and units based on a monomer having a carbonyl group-containing group, in which the total units contain 90 to 99 mol%, 0.99 to 9.97 mol%, and 0.01 to 3 mol%, respectively, in that order. Specific examples of such F polymers include the polymers described in WO 2018 / 16644.

[0021] The F particles in this method are preferably non-hollow particles made of an F polymer. The D50 of the F particles is 10 μm or less, more preferably less than 8 μm. The D50 of the F particles is preferably 0.01 μm or more, more preferably 0.3 μm or more, and even more preferably 1 μm or more. In this case, the composition is likely to have better liquid properties such as dispersion stability and homogeneity. Furthermore, the composition is likely to produce a polymer layer having a low linear expansion coefficient, dielectric constant, and dielectric loss tangent, as well as excellent thermal conductivity and adhesion to a substrate. The specific surface area of ​​F particles is 1 to 25 m 2 / g is preferred, and 3 to 15m 2 / g is more preferred.

[0022] One type of F particles may be used, or two or more types may be used. The F particles are preferably particles of at least a heat-fusible F polymer, more preferably particles of a heat-fusible F polymer having an oxygen-containing polar group and a melting temperature of 180 to 320°C. In this case, aggregation of the F particles is also easily suppressed, and the liquid properties of the composition are likely to be improved.

[0023] When two types of F particles are used, the F particles are preferably a mixture of particles of a heat-fusible F polymer and particles of a non-heat-fusible F polymer. In this case, the aggregation-inhibiting effect of the heat-fusible F polymer particles and the retention effect of the non-heat-fusible F polymer due to fibrillation are balanced, which tends to improve the dispersibility of the composition. Furthermore, in the polymer layer obtained from this, the electrical properties of the non-heat-fusible F polymer are highly expressed, and a polymer layer with a particularly low dielectric loss tangent is easily obtained. The former particles are preferably particles of a heat-fusible F polymer having a melting temperature of 180 to 320° C., and more preferably particles of a heat-fusible F polymer having an oxygen-containing polar group and a melting temperature of 180 to 320° C. In the former particles, the preferred embodiments of the heat-fusible F polymer having an oxygen-containing polar group are the same as the preferred embodiments of the F polymer having an oxygen-containing polar group described above. As the latter particles, particles of non-thermofusible PTFE are preferred.

[0024] The F particles may contain a resin or an inorganic compound other than the F polymer, may form a core-shell structure with an F polymer as the core and a resin other than the F polymer or an inorganic compound as the shell, or may form a core-shell structure with an F polymer as the shell and a resin other than the F polymer or an inorganic compound as the core. Here, examples of resins other than F polymer include aromatic polyester, polyamideimide, polyimide, and maleimide, and examples of inorganic compounds include silica and boron nitride.

[0025] In this method, the composition may further contain at least one resin selected from polyimide, polyamideimide, polyetherimide, or maleimide (hereinafter also referred to as "the resin"). Preferably, the composition contains the resin. Note that the term "resin" in the context of the resin also encompasses precursors of the above-mentioned resins, such as polyimide precursors (polyamic acids or salts thereof). This resin improves the dispersion stability of the composition and also plays a role in controlling the shear viscosity 1 and shear viscosity 2 of the composition. Furthermore, when the composition is applied to the surface of a substrate such as a polyimide film to form a polymer layer containing F polymer, this resin imparts properties to the polymer layer, such as flexibility (e.g., flex resistance), UV absorption, and adhesiveness and adhesion to the substrate. The resin is preferably an aromatic resin, and is preferably an aromatic polyimide, a modified aromatic polyimide having a polar functional group such as a carboxylic acid group, an aromatic polyamideimide, a modified aromatic polyamideimide, an aromatic polyetherimide, or an aromatic maleimide. It is more preferable that the resin is water-soluble.

[0026] Examples of aromatic polyimides include polyamic acids obtained by polymerizing tetracarboxylic dianhydrides and diamines in a solvent, and polyamic acid salts obtained by reacting such polyamic acids with aqueous ammonia or organic amines. An aqueous solution of polyamic acid can be prepared by dissolving the polyamic acid salt in water. Examples of aromatic polyamideimides include polyamideimides obtained by reacting a diisocyanate and / or a diamine with a tribasic acid anhydride (or tribasic acid chloride) as an acid component. Examples of aromatic polyetherimides include amorphous polymers having imide bonds and ether bonds in the main chain, and a polycondensation product of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane and m-phenylenediamine is preferred.

[0027] Commercially available products of this resin include "HPC-1000" and "HPC-2100D" (both manufactured by Showa Denko Materials Co., Ltd.) and "Ultem 1000F3SP" (aromatic polyetherimide, manufactured by SABIC).

[0028] The number average molecular weight (Mn) of the resin is preferably 5,000 or more, more preferably 10,000 or more, and even more preferably 15,000 or more. Meanwhile, Mn is preferably 50,000 or less, more preferably 30,000 or less, and even more preferably 25,000 or less. When Mn is within this range, the water solubility and mechanical properties such as flex resistance of the polymer layer formed from the composition can be ensured. Note that Mn refers to the number average molecular weight calculated as standard polystyrene by gel permeation chromatography (GPC).

[0029] In this method, the composition may further contain at least one liquid dispersion medium selected from water, ketones, and amides, and preferably contains a liquid dispersion medium. These liquid dispersion mediums are compounds that do not react with the F polymer, are liquid at 25°C under atmospheric pressure, and preferably have a boiling point of 50 to 240°C. One type of liquid dispersion medium may be used, or two or more types may be used. When two or more types of liquid dispersion mediums are used, it is preferable that the two or more types of liquid dispersion mediums are mutually compatible. Examples of ketones include acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl isopentyl ketone, 2-heptanone, cyclopentanone, cyclohexanone, and cycloheptanone. Examples of amides include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropanamide, 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, N,N-diethylformamide, hexamethylphosphoric triamide, and 1,3-dimethyl-2-imidazolidinone. Of these liquid dispersion media, water and N-methyl-2-pyrrolidone are more preferred, and water is even more preferred from the viewpoint of ease of working environment and safety management.

[0030] In this method, the content of the liquid dispersion medium in the composition is preferably 20% by mass or more, more preferably 40% by mass or more, from the viewpoint of setting the shear viscosity 1 and shear viscosity 2 of the composition within the ranges specified in the present invention. The content of the liquid dispersion medium is preferably 80% by mass or less, more preferably 60% by mass or less.

[0031] In this method, the composition may further contain at least one thickener polymer selected from an acrylic thickener, a cellulose thickener, or a polyvinyl alcohol thickener. When such a thickener polymer is contained, the dispersion stability of the composition is improved, and the shear viscosity 1 and shear viscosity 2 are easily controlled within the ranges specified by this method. Furthermore, the rheological properties are improved, and the handling properties of the composition, such as film-forming properties, are easily improved. As a result, a thick polymer layer can be more easily formed from the composition. This tendency is particularly pronounced when the thickener polymer is a nonionic cellulose thickener.

[0032] Examples of acrylic thickeners include polymethyl methacrylate, polyacrylic acid, and salts of polyacrylic acid. Polyvinyl alcohol thickeners include polyvinyl alcohol, partially acetylated or partially acetalized polyvinyl alcohol. Examples of the cellulose-based thickener include methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxypropyl cellulose. The thickener polymers mentioned above are preferably water-soluble, more preferably nonionic cellulose-based thickeners, and even more preferably hydroxymethyl cellulose, hydroxyethyl cellulose or hydroxypropyl cellulose.

[0033] When the present composition further contains the thickener polymer, the amount thereof is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, relative to the total mass of the present composition, from the viewpoint of easily controlling the shear viscosity 1 and shear viscosity 2 of the present composition within the ranges specified in the present invention. The amount is preferably less than 1% by mass. The ratio of the mass of the above-mentioned thickener polymer to the mass of the F particles in the present composition is preferably 0.001 or more, more preferably 0.01 or more. The ratio is preferably less than 0.1.

[0034] The composition may further contain an inorganic filler, preferably an inorganic filler containing an oxide, a nitride, an elemental metal, an alloy, or carbon, more preferably an inorganic filler containing silicon oxide (silica), a metal oxide (beryllium oxide, cerium oxide, alumina, soda alumina, magnesium oxide, zinc oxide, titanium oxide, etc.), boron nitride, or magnesium metasilicate (steatite).

[0035] The shape of the inorganic filler may be any of granular, needle-like (fibrous), and plate-like. Specific shapes of the inorganic filler include spherical, scale-like, layer-like, flat, leaf-like, apricot-like, columnar, cockscomb-like, equiaxial, leaf-like, mica-like, block-like, flat, wedge-like, rosette-like, mesh-like, and prismatic. The inorganic filler may be hollow, and may contain hollow inorganic fillers and non-hollow inorganic fillers. The shape of the inorganic filler is preferably spherical or scale-like. The D50 of the inorganic filler is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 1 μm or less.The D50 of the inorganic filler is preferably 0.01 μm or more, and more preferably 0.1 μm or more. The surface of the inorganic filler may be surface-treated with a silane coupling agent.

[0036] When the composition further contains an inorganic filler, the mass ratio of the inorganic filler to the F particles is preferably in the range of 10:90 to 90:10, more preferably 30:70 to 70:30. In this case, the polymer layer formed from the composition can achieve both a low dielectric constant and improved processability at a high level. In addition, the shear viscosity 1 and shear viscosity 2 of the composition can be easily controlled within the ranges specified in the present invention.

[0037] The composition of the present invention may further contain a nonionic surfactant to improve dispersibility. Examples of the surfactant include acetylene-based surfactants, silicone-based surfactants, and fluorine-based surfactants. When a surfactant is contained, the content of the surfactant in the composition is preferably 1 to 15% by mass.

[0038] In this method, the composition may further contain another resin material. The other resin material may be thermosetting or thermoplastic, and is preferably an elastomer. When the composition further contains an elastomer, the heat resistance, adhesiveness, and dimensional stability of the polymer layer obtained from the composition can be improved. Examples of the elastomer include styrene-based elastomers such as polystyrene-polybutadiene block copolymer and polystyrene-polyisoprene block copolymer, 1,2-polybutadiene, 1,4-polybutadiene, maleic acid-modified polybutadiene, acrylic acid-modified polybutadiene, and epoxy-modified polybutadiene.

[0039] In this method, in addition to these components, the composition may contain additives such as a thixotropic agent, a viscosity modifier, a dehydrating agent, an antifoaming agent, a plasticizer, a weathering agent, an antioxidant, a heat stabilizer, a lubricant, an antistatic agent, a whitening agent, a colorant, a conductive agent, a mold release agent, and a flame retardant.

[0040] In this method, the content of F particles in the composition is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 60% by mass or less, more preferably 50% by mass or less. The content of the present resin relative to the content of the F particles in the present composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less. When the content of the F particles in the composition and the content of the resin relative to the content of the F particles are within the above ranges, not only is it easy to obtain a composition that satisfies the liquid physical properties specified in the present invention, but it is also easy to form a thicker coating layer, and it is also easy to obtain a polymer layer from the composition that has better electrical properties and adhesion to the substrate.

[0041] The present composition can be prepared by mixing F particles, the present resin, and the above-mentioned liquid dispersion medium. Examples of mixing methods include adding the F particles and the present resin to the liquid dispersion medium all at once or sequentially and mixing; premixing the F particles and the liquid dispersion medium, and the present resin and the liquid dispersion medium, respectively, and then mixing the resulting mixtures. When water is used as the liquid dispersion medium, the present composition can be prepared by pre-dispersing the F particles in water, and then adding the present resin directly or after mixing with water, or by pre-mixing the present resin in water, and then adding the F particles directly or after mixing with water, which is advantageous and preferred from the perspective of dispersing the F particles more uniformly. If the composition further contains a thickener polymer, an inorganic filler, a nonionic surfactant, or other resin materials or additives, it is preferable to add them simultaneously when dispersing the F particles in a liquid dispersion medium, preferably water, or to add them in advance to water before dispersing the F particles.

[0042] Examples of mixing means for preparing the present composition include stirring using a stirring device equipped with uniaxial or multiaxial blades (stirring blades) such as propeller blades, turbine blades, paddle blades, shell-shaped blades, etc., or a Henschel mixer, pressure kneader, Banbury mixer, or planetary mixer; mixing using a disperser that uses media such as a ball mill, attritor, basket mill, sand mill, sand grinder, Dyno-mill (a bead mill that uses grinding media such as glass beads or zirconium oxide beads), Dispermat, SC mill, spike mill, or agitator mill; and mixing using a disperser that does not use media such as a high-pressure homogenizer such as a Microfluidizer, Nanomizer, or Ultimizer, an ultrasonic homogenizer, a Dissolver, a Disper, a high-speed impeller disperser, a planetary mixer, or a thin-film rotation-and-revolution type high-speed mixer. The mixing may be carried out by either a batch method or a continuous method.

[0043] In this method, the composition having the specific shear viscosity described above is applied to the surface of a substrate while the substrate is running through a lip coater type coating device, thereby obtaining a long substrate having a coating layer made of the composition. The lip coater type coating device used in this method is a coating device, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-152574, in which a nozzle head having a doctor edge is disposed below a backing roll, and a coating liquid is sprayed from the nozzle head under pressure by a coating liquid supply means, and the coating liquid is applied to a substrate by the doctor edge.

[0044] In this device, a first liquid retaining chamber is provided in the width direction inside the nozzle head, an outflow path is provided inside the nozzle head that continues from the first liquid retaining chamber to the front of the doctor edge, a liquid retaining wall is erected from the front of the nozzle head to the lower peripheral surface of the backing roll, leaving a gap for the web to run, the portion formed by the lower peripheral surface of the backing roll, the liquid retaining wall and the front surface of the doctor edge serves as a second liquid retaining chamber that is expanded forward from the outlet of the outflow path to have a volume larger than that of the outflow path, a pressure detection means is provided in the second liquid retaining chamber, and a control means is provided that controls the supply device based on the pressure detected by the pressure detection means.

[0045] With this configuration, the substrate passes through the second liquid retaining chamber filled with the coating liquid and travels to the doctor edge, where the coating liquid is applied by the linear pressure of the cutting edge of the doctor edge. In this case, the second liquid retaining chamber is formed to be larger in volume than the outlet of the outlet channel by expanding forward of the outlet, making it easy to maintain a constant pressure higher than atmospheric pressure inside the second liquid retaining chamber, and therefore, when the web is transported into the second liquid retaining chamber through the gap between the liquid retaining wall and the backing roll, air does not enter the second liquid retaining chamber. In addition, the pressure of the coating liquid inside the second liquid retention chamber is detected by the pressure detection means and transmitted to the control means, and the control means controls the supply means based on the transmitted pressure to maintain the pressure of the coating liquid inside the second liquid retention chamber constant.

[0046] Therefore, this method using such a coating device has the advantage of eliminating problems such as unevenness and streaks on the coated surface that occur when a method of applying a coating liquid to a substrate surface using a reverse roll coater, air knife coater, knife coater, or the like to produce a laminate having a coating layer and a substrate layer, or a method of forming a coating layer on a substrate by dip coating, is applied to a continuous production process using a coating liquid containing a tetrafluoroethylene-based polymer.

[0047] Examples of the substrate include single-layer or multi-layer heat-resistant resin films containing one or more heat-resistant resins such as polyimide, polyarylate, polysulfone, polyarylsulfone, polyamide, polyetheramide, polyphenylene sulfide, polyaryletherketone, polyamideimide, liquid crystal polymer (liquid crystal polyester, liquid crystal polyesteramide), and polytetrafluoroethylene; and metal substrates such as metal foils of copper, nickel, aluminum, titanium, alloys thereof, and the like. Among these, in the present method, the substrate is preferably a polyimide film, a liquid crystal polymer film, a polytetrafluoroethylene film, or a copper foil. As the copper foil, rolled copper foil or electrolytic copper foil is more preferable, and low-roughening copper foil is even more preferable.

[0048] In this method, the composition having the specific shear viscosity described above is applied to the surface of the substrate while the substrate is running through a lip coater-type coating device, thereby obtaining a long substrate having a coating layer (wet film) made of the composition. The long substrate having such a coating layer is further dried and baked to form a polymer layer containing an F polymer (hereinafter also referred to as an "F layer"), thereby obtaining a long substrate having an F layer on the substrate surface. When drying the coating layer, the coating layer is heated to a temperature at which the liquid dispersion medium volatilizes, forming a dry film on the surface of the substrate. The heating temperature is preferably equal to or lower than the boiling point of the liquid dispersion medium, more preferably equal to or lower than the boiling point minus 20°C. The specific temperature during drying is preferably 80°C to 200°C. Air may be blown in the process of removing the liquid dispersion medium. The temperature during baking is preferably a temperature at which baking of the F polymer proceeds, more preferably 380°C or lower.

[0049] The heating may be carried out under either atmospheric pressure or reduced pressure. The heating atmosphere may be any of an oxidizing gas atmosphere (oxygen gas, etc.), a reducing gas atmosphere (hydrogen gas, etc.), and an inert gas atmosphere (helium gas, neon gas, argon gas, nitrogen gas, etc.). The heating time is preferably 0.1 to 30 minutes, more preferably 0.5 to 20 minutes.

[0050] The thickness of the coating layer is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 50 μm or more, from the viewpoint of further improving the physical properties such as the electrical properties of the F layer obtained from the coating layer and the adhesion to the substrate. The thickness of the coating layer is preferably 250 μm or less, and more preferably 100 μm or less from the viewpoint of coatability and stability of the coating layer. The thickness of the F layer formed from such a coating layer is preferably 20 to 250 μm. Specifically, when the substrate layer is a polyimide film, the thickness of the F layer is preferably 20 to 250 μm. The peel strength between the F layer and the substrate layer is preferably 10 N / cm or more, more preferably 15 N / cm or more. The peel strength is preferably 100 N / cm or less. By using this composition, a long substrate can be easily formed without impairing the physical properties of the F polymer in the F layer.

[0051] In this method, the composition may be applied to only one surface of the substrate layer, or to both surfaces of the substrate layer. In this method, a long substrate having a substrate layer and an F layer on both sides of the substrate layer can be preferably obtained in any of the following ways. That is, while the substrate is running through a lip coater type coating device, the present composition is sprayed from a nozzle head to coat the surface of the substrate, resulting in a long substrate having a coating layer formed from the present composition, which is then dried and baked to obtain a long substrate having an F layer on the surface of the substrate, the resulting long substrate having an F layer is wound up, and while the long substrate having the F layer is unwound and running through the lip coater type coating device, the present composition is sprayed from a nozzle head to coat the surface of the substrate opposite to the side having the F layer, which is then dried and baked to obtain a long substrate having an F layer on both sides of the substrate. Alternatively, while a substrate is traveling through a lip coater type coating device, the present composition is sprayed from a nozzle head to coat the surface of the substrate, resulting in a long substrate having a coating layer formed from the present composition, which is then dried and baked to obtain a long substrate having an F layer on the substrate surface; while the long substrate having the F layer is traveling through another lip coater type coating device, the present composition is sprayed from the nozzle head of the other lip coater type coating device to coat the surface of the substrate opposite to the side having the F layer, which is then dried and baked to obtain a long substrate having F layers on both sides of the substrate. Alternatively, the composition may be sprayed from nozzle heads using multiple lip coater-type coating devices to coat both surfaces of the substrate, thereby obtaining a long substrate having coating layers formed from the composition on both surfaces of the substrate, which may then be dried and baked to obtain a long substrate having an F layer on both surfaces of the substrate. A long substrate having a substrate layer and an F layer on both surfaces of the substrate layer is less likely to warp, and is therefore easier to handle during processing.

[0052] Specific examples of long substrates obtainable by this method include metal clad laminates having a metal foil and an F layer on at least one surface of the metal foil, and multilayer films having a polyimide film and an F layer on both surfaces of the polyimide film. Such a long substrate has an F layer with excellent electrical properties, making it suitable as a printed circuit board material. Specifically, it can be used to manufacture printed circuit boards as a flexible metal-clad laminate or a rigid metal-clad laminate, and is particularly suitable for use as a flexible metal-clad laminate to manufacture flexible printed circuit boards. In manufacturing such printed circuit boards, an interlayer insulating film may be formed on a transmission circuit, a solder resist may be laminated on the transmission circuit, or a coverlay film may be laminated on the transmission circuit. These interlayer insulating films, solder resists, and coverlay films may be formed from the present composition.

[0053] Such long substrates are useful as antenna parts, printed circuit boards, aircraft parts, automobile parts, sports equipment, food industry supplies, paints, cosmetics, etc., and specifically as electric wire coating materials (aircraft electric wires, etc.), electrical insulating tape, insulating tape for oil drilling, materials for printed circuit boards, separation membranes (microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, ion exchange membranes, dialysis membranes, gas separation membranes, etc.), electrode binders (for lithium secondary batteries, for fuel cells, etc.), copy rolls, covers for furniture, automobile dashboards, home appliances, etc., sliding parts (load bearings, sliding shafts, valves, bearings, gears, cams, belt conveyors, food transport belts, etc.), tools (shovels, files, saws, saws, etc.), boilers, hoppers, pipes, ovens, baking molds, chutes, dies, toilets, and container coating materials.

[0054] Although the present invention has been described above, it is not limited to the configuration of the above-described embodiment. For example, in the configuration of the above embodiment, the method may have any other steps added thereto, or may be substituted with any steps that produce the same effect. [Example]

[0055] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. 1. Preparation of each ingredient [F particle] F Particle 1: Particles (D50: 2.0 μm) made of polymer 1 (melting temperature: 300°C) containing TFE units, NAH units, and PPVE units in the order of 97.9 mol%, 0.1 mol%, and 2.0 mol%, respectively, and having oxygen-containing polar groups. F Particle 2: Particles (D50: 11.0 μm) made of polymer 2 (melting temperature: 300°C) containing 97.9 mol%, 0.1 mol%, and 2.0 mol% of TFE units, NAH units, and PPVE units, in that order, and having no oxygen-containing polar groups. [Resin varnish] Varnish 1: Water varnish containing a precursor of aromatic polyamideimide (PAI1) (product name "HP-1000", manufactured by Showa Denko Materials Co., Ltd.) [Surfactants] Surfactant 1: Silicone surfactant (trade name "BYK-3450", manufactured by BYK Japan) [Thickener polymer] Thickener 1: Hydroxyethylcellulose [Base material] Substrate 1: 25 μm thick aromatic polyimide film (PI Advanced Materials "FG-100")

[0056] 2. Preparation of liquid composition <Production Example 1> F particles 1, varnish 1, surfactant 1, thickener 1, and water were added to a pot, and zirconia balls were then added. The pot was then rolled at 150 rpm for 1 hour to obtain Liquid Composition 1 containing F particles 1 (40 parts by mass), PAI 1 (0.32 parts by mass), surfactant 1 (3 parts by mass), thickener 1 (0.6 parts by mass), and water (43.92 parts by mass). The obtained liquid composition 1 was subjected to a shear rate of 2.6 sec at 25°C. -1 The shear viscosity at 25°C (shear viscosity 1) is 2800 mPa·s, and the shear rate is 52.8 s -1 The shear viscosity at (shear viscosity 2) was 650 mPa·s.

[0057] <Production Example 2> The same procedure as in Example 1 was repeated except for varying the amount of F Particles 1, to obtain Liquid Composition 2 containing F Particles 1 (30 parts by mass), PAI 1 (0.32 parts by mass), Surfactant 1 (3 parts by mass), Thickener 1 (0.6 parts by mass), and water (53.92 parts by mass). The shear viscosity 1 of the obtained Liquid Composition 2 was 1100 mPa s, and the shear viscosity 2 was 500 mPa s.

[0058] <Production Example 3> The same procedure as in Example 1 was carried out without adding surfactant 1, to obtain liquid composition 3 containing F particles 1 (40 parts by mass), PAI 1 (0.32 parts by mass), thickener 1 (0.6 parts by mass), and water (46.92 parts by mass). The shear viscosity 1 of the obtained liquid composition 3 was 3000 mPa s, and the shear viscosity 2 was 1200 mPa s.

[0059] <Production Example 4> The same procedure as in Example 1 was carried out using F Particles 2 instead of F Particles 1, to obtain Liquid Composition 4 containing F Particles 2 (40 parts by mass), PAI 1 (0.32 parts by mass), Surfactant 1 (3 parts by mass), Thickener 1 (0.6 parts by mass), and water (43.92 parts by mass). The shear viscosity 1 of the obtained Liquid Composition 4 was 1500 mPa s, and the shear viscosity 2 was 750 mPa s.

[0060] 3. Manufacturing of long substrates <Example 1> A nozzle head with a doctor edge was placed on the surface of a backing roll along which the substrate traveled in the forward and backward directions, and the coating liquid was sprayed from the nozzle head under pressure, using a lip coater-type coating device that applied the coating liquid to the substrate using the doctor edge.While the substrate 1 was traveling in a roll-to-roll process, liquid composition 1 was sprayed from the nozzle head as the coating liquid to coat the surface of the substrate 1 to a coating layer thickness of 60 μm.The substrate was then passed through a ventilated drying oven (oven temperature 150°C) for 3 minutes to remove water and form a dry coating, and then passed through a far-infrared oven (oven temperature 300°C near the entrance and exit of the oven, and 360°C near the center) for 5 minutes to melt and bake the F particles 1. As a result, a polymer layer containing the molten and fired F particles 1 and PAI 1 was formed on one surface of the substrate 1, and a laminate (long substrate 1) in which the polymer layer and substrate 1 layer were formed in this order was obtained by a roll-to-roll process. The thickness of the polymer layer in the long substrate 1 was 50 μm. <Examples 2-4> Except for changing Liquid composition 1 to Liquid compositions 2 to 4, respectively, long substrates 2 to 4 were produced in the same manner as in Example 1. The thickness of the polymer layer in long substrate 2, long substrate 3 and long substrate 4 was each 50 μm.

[0061] 4. Evaluation of long substrates 4-1.Superficiality The polymer layer of each of the long substrates 1 to 4 was visually inspected for the presence or absence of streaky patterns in the machine direction, and evaluated according to the following criteria. [Evaluation criteria] ◯: No streaks occur in coating lengths of 1 to 100 m. △: Streaks occurred at the edges in coating lengths of 1 to 100 m. ×: Streaks occurred throughout the coating length of 1 to 100 m.

[0062] 4-2. Adhesion Test pieces were cut out from each of the long substrates 1 to 4, and were immersed in a solder bath heated to 280°C for 5 minutes, then removed from the solder bath and cooled to 25°C. The appearance of each test piece was visually observed and evaluated according to the following criteria. [Evaluation criteria] ◯: No swelling or peeling occurs. △: Some swelling is observed. ×: Blisters or peeling are observed. The evaluation results are summarized in Table 1.

[0063] [Table 1] [Industrial Applicability]

[0064] The long substrate obtained by the production method of the present invention has an excellent surface property without streaks or the like occurring in the polymer layer containing a tetrafluoroethylene-based polymer, and has excellent electrical properties and adhesion to substrates such as polyimide films, and therefore can be used to produce printed circuit boards and the like.

Claims

1. A nozzle head having a doctor edge is disposed on the surface of a backing roll on which a substrate travels in the forward and backward directions, and a coating liquid is sprayed from the nozzle head by pressure to coat the substrate with the doctor edge. While the substrate is traveling through a lip coater type coating device, the coating liquid contains particles of a tetrafluoroethylene-based polymer having an average particle size of 10 μm or less, and is applied to the substrate at a temperature of 25° C. and a shear rate of 2.6 sec. －１ The shear viscosity is 1000 to 10000 mPa·s at a temperature of 25°C and a shear rate of 52.8 sec －１ a liquid composition having a shear viscosity of 200 to 1500 mPa s at 2000 W / mPa s is sprayed from the nozzle head to coat the surface of the substrate, thereby obtaining a long substrate having a coating layer formed from the liquid composition.

2. The temperature is 25°C and the shear rate is 2.6 sec －１ Shear viscosity at 25°C and shear rate 52.8 sec －１ The method according to claim 1, wherein the ratio of shear viscosities in the above formula (1) is 0.05 or more and less than 0.

40.

3. The method according to claim 1 , wherein the tetrafluoroethylene-based polymer is a heat-fusible tetrafluoroethylene-based polymer.

4. The method according to claim 1 , wherein the tetrafluoroethylene-based polymer is a tetrafluoroethylene-based polymer having an oxygen-containing polar group.

5. The method according to claim 1 , wherein the liquid composition further contains at least one resin selected from the group consisting of polyimide, polyamideimide, polyetherimide, and maleimide.

6. The method according to claim 1 , wherein the liquid composition further comprises at least one liquid dispersion medium selected from water, a ketone, or an amide.

7. The method according to claim 1 , wherein the liquid composition further comprises at least one thickener polymer selected from an acrylic thickener, a cellulose thickener, or a polyvinyl alcohol thickener.

8. The method according to claim 1 , wherein the liquid composition further comprises an inorganic filler.

9. The method according to claim 1 , wherein the liquid composition further comprises a nonionic surfactant.

10. The method according to claim 1, wherein the content of the tetrafluoroethylene polymer particles in the liquid composition is 20 to 50% by mass.

11. The manufacturing method according to claim 1 , wherein the substrate is a polyimide film, a liquid crystal polymer film, a polytetrafluoroethylene film, or a copper foil.

12. The method according to claim 1, wherein the coating layer has a thickness of 20 μm to 250 μm.

13. A method for producing a long substrate, comprising: further drying and baking a long substrate having a coating layer made of the liquid composition obtained by the production method according to any one of claims 1 to 12, to obtain a long substrate having a polymer layer containing the tetrafluoroethylene-based polymer on the surface of the substrate.

14. A nozzle head having a doctor edge is disposed on the surface of a backing roll on which a substrate travels in the forward and backward directions, and a coating liquid is sprayed from the nozzle head by pressure to coat the substrate with the doctor edge. While the substrate is traveling through a lip coater type coating device, the coating liquid contains particles of a tetrafluoroethylene-based polymer having an average particle size of 10 μm or less, and is applied to the substrate at a temperature of 25° C. and a shear rate of 2.6 sec. －１ The shear viscosity is 1000 to 10000 mPa·s at a temperature of 25°C and a shear rate of 52.8 sec －１ a liquid composition having a shear viscosity of 200 to 1500 mPa s at 1000 kJ / s is sprayed from the nozzle head to coat the surface of the substrate, thereby obtaining a long substrate having a coating layer formed from the liquid composition; the long substrate is further dried and baked to obtain a long substrate having a polymer layer containing the tetrafluoroethylene-based polymer on the surface of the substrate; the long substrate having the obtained polymer layer is wound up; and while the long substrate having the polymer layer is unwound and allowed to run on the lip coater-type coating device, the liquid composition is sprayed from the nozzle head as the coating liquid to coat the surface of the substrate opposite to the surface having the polymer layer; and further dried and baked to obtain a long substrate having polymer layers containing the tetrafluoroethylene-based polymer on both surfaces of the substrate.

15. A nozzle head having a doctor edge is disposed on the surface of a backing roll on which a substrate travels in the forward and backward directions, and a coating liquid is sprayed from the nozzle head by pressure to coat the substrate with the doctor edge. While the substrate is traveling through a lip coater type coating device, the coating liquid contains particles of a tetrafluoroethylene-based polymer having an average particle size of 10 μm or less, and is applied to the substrate at a temperature of 25° C. and a shear rate of 2.6 sec. －１ The shear viscosity is 1000 to 10000 mPa·s at a temperature of 25°C and a shear rate of 52.8 sec －１ a liquid composition having a shear viscosity of 200 to 1500 mPa s at 1000 kJ / s is sprayed from the nozzle head to coat the surface of the substrate, thereby obtaining a long substrate having a coating layer formed from the liquid composition; the long substrate is further dried and baked to obtain a long substrate having a polymer layer containing the tetrafluoroethylene-based polymer on the surface of the substrate; while the long substrate having the polymer layer is traveling through another lip coater-type coating device, the liquid composition is sprayed from the nozzle head as the coating liquid to coat the surface of the substrate opposite to the surface having the polymer layer, and further dried and baked to obtain a long substrate having polymer layers containing the tetrafluoroethylene-based polymer on both surfaces of the substrate.

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