Porous films and laminates

Abstract

To provide a porous film having high adhesion, and a laminate including the porous film.SOLUTION: An porous film has a porous structure having a plurality of holes inside and on it, and a coating layer that coats at least partially the inner wall of the porous structure. The plurality of holes have a pore size distribution from one principal face to the other principal face of the porous structure. There is also provided an application thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to porous films and laminates. [Background technology]

[0002] In recent years, porous films have been applied to a variety of fields.

[0003] For example, Patent Document 1 describes an embodiment in which metal electrodes are joined by mechanical pressure to a pair of current collectors made of a gas-permeable porous body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-113192 Summary of the Invention [Problem to be solved by the invention]

[0005] In some cases, porous films are required to have improved adhesiveness.

[0006] The present disclosure has been made in view of the above circumstances, and a problem to be solved by one embodiment of the present disclosure is to provide a porous film having excellent adhesion. Another problem to be solved by another embodiment of the present disclosure is to provide a laminate using the porous film. [Means for solving the problem]

[0007] The means for solving the above problems include the following aspects. <1> A porous film comprising: a porous structure having a plurality of pores inside and on a surface thereof; and a coating layer covering at least a portion of the inner wall of the porous structure, wherein the plurality of pores have a pore size distribution from one main surface of the porous structure to the other main surface. <2> The plurality of pores have an internal pore size smaller than a surface pore size. <1> The porous film according to claim 1. <3> The area ratio of the coating layer on the inner wall of the porous structure is 30% or more of the total surface area of ​​the inner wall. <1> or <2> The porous film according to claim 1. <4> The coating layer includes a conductor or a catalyst. <1> ~ <3> 10. The porous film according to claim 9, wherein the porous film is a porous film having a thickness of 100 nm or less. <5> The conductor or catalyst is at least one selected from the group consisting of platinum, iridium, rhodium, ruthenium, palladium, silver, copper, tantalum, nickel, iron phosphide, nickel phosphide, and iridium oxide. <4> The porous film according to claim 1. <6> The porous structure comprises a polymer, <1> ~ <5> 10. The porous film according to claim 9, wherein the porous film is a porous film having a thickness of 100 nm or less. <7> The polymer has a glass transition temperature of 150°C or higher. <6> The porous film according to claim 1. <8> The polymer includes at least one selected from the group consisting of a liquid crystal polymer and a polysulfone. <6> or <7> The porous film according to claim 1. <9> The liquid crystal polymer contains a constitutional unit represented by any one of formulas (1) to (3): <8> The porous film according to claim 1. Formula (1) -O-Ar 1 -CO- Formula (2) -CO-Ar 2 -CO- Formula (3) -X-Ar 3 -Y- In formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar 2 and Ar 3 each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, Ar 1 ~Ar 3 Each hydrogen atom in the group represented by the formula (I) may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Formula (4) -Ar 4 -Z-Ar5 - In formula (4), Ar 4 and Ar 5 each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group. <10> The electrode is <1> ~ <9> 10. The porous film according to claim 9, wherein the porous film is a porous film having a thickness of 100 nm or less. <11> <10> and an electrolyte membrane disposed on the porous film. <12> It is an adhesive film, <1> ~ <9> 10. The porous film according to claim 9, wherein the porous film is a porous film having a thickness of 100 nm or less. <13> a metal layer; <12> and a resin layer, in this order. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, a porous film having excellent adhesion can be provided. According to another embodiment of the present disclosure, a laminate using the porous film can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present disclosure will be described in detail below. The following description of the components may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments. In this specification, the use of "to" to indicate a range of values ​​means that the values ​​before and after it are included as the lower and upper limits. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. Furthermore, in the description of groups (atomic groups) in this specification, a description that does not specify whether it is substituted or unsubstituted includes both unsubstituted and substituted groups. For example, the term "alkyl group" includes not only alkyl groups that do not have a substituent (unsubstituted alkyl groups) but also alkyl groups that have a substituent (substituted alkyl groups). Furthermore, the term "step" in this specification does not only refer to an independent step, but also includes a step that cannot be clearly distinguished from other steps as long as the intended purpose of the step is achieved. Furthermore, in this disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous. Furthermore, in the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. Furthermore, unless otherwise specified, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) in the present disclosure are molecular weights determined by gel permeation chromatography (GPC) using columns of TSKgel GMHxL, TSKgel G4000HxL, or TSKgel G2000HxL (all trade names manufactured by Tosoh Corporation), detection with a differential refractometer using THF (tetrahydrofuran) as a solvent, and conversion using polystyrene as a standard substance.

[0010] The present disclosure will be described in detail below.

[0011] [Porous film] The porous film according to the present disclosure includes a porous structure having a plurality of pores inside and on its surface, and a coating layer that covers at least a portion of the inner wall of the porous structure, and the plurality of pores have a pore size distribution from one main surface of the porous structure to the other main surface.

[0012] The present inventors have found that conventional porous films do not have sufficient adhesion to other layers (for example, resin layers, metal layers, etc.). As a result of extensive research, the present inventors have found that by adopting the above-mentioned configuration, a porous film having excellent adhesiveness can be provided.

[0013] In the porous film according to the present disclosure, the plurality of pores have a pore size distribution from one main surface of the porous structure to the other main surface, and therefore the film has better adhesion than conventional films.

[0014] <Porous structure> The porous film according to the present disclosure includes a porous structure having a plurality of pores inside and on the surface. The porous structure is preferably in the form of a film. The plurality of pores have a pore size distribution from one main surface of the porous structure to the other main surface. The main surface means the surface having the major area of ​​the surface. In the present disclosure, the main surfaces of the porous structure refer to two surfaces perpendicular to the thickness direction of the porous structure.

[0015] The plurality of holes formed in the porous structure may be through-holes. In the porous film according to the present disclosure, the porous structure preferably has through-holes that penetrate from one main surface to the other main surface.

[0016] Through holes refer to holes that penetrate from one surface to the other surface. When a porous structure has through holes, the openings of the through holes are present on the two main surfaces of the porous structure. The porous structure may have through holes other than the through holes that penetrate from one main surface to the other main surface. The other through holes are, for example, through holes that penetrate from one main surface to a side surface. In other words, the porous structure may have through hole openings on surfaces other than the two main surfaces.

[0017] Furthermore, a through hole penetrating from one main surface to the other main surface may have only two openings, or may have three or more openings. When there are two openings, it means that the through hole is formed from one main surface to the other main surface without branching. On the other hand, when there are three or more openings, it means that the through hole has a branched portion inside.

[0018] In the porous structure, the number of through-holes penetrating from one main surface to the other main surface is not particularly limited.

[0019] The plurality of pores in the porous structure have a pore size distribution from one main surface to the other main surface of the porous structure.

[0020] In the present disclosure, "having a pore size distribution from one main surface of the porous structure to the other main surface" means that the pore size is not constant but changes from one main surface of the porous structure to the other main surface.

[0021] Whether or not the pores in the porous structure have a pore size distribution from one main surface to the other main surface of the porous structure is determined by the following method.

[0022] A porous film is cut using a microtome or the like to obtain a sample for cross-section evaluation. A cross-sectional SEM image of the sample for cross-section evaluation is obtained, and the average pore diameter at an arbitrary thickness from one main surface of the porous film is calculated for the pores present in the cross section. The average pore diameters calculated at each thickness are compared, and if the maximum value is 1.1 times or more the minimum value, it is determined that the porous structure has a pore size distribution from one main surface to the other main surface. The thickness position and number at which the average pore diameter is calculated are appropriately set depending on the thickness of the porous film, but the number of thickness positions measured at thickness positions equally dividing the other main surface from the main surface to calculate the average pore diameter is 5 or more.

[0023] The pore diameter refers to the equivalent circle diameter when the pores are circular, and refers to the average value of the major and minor diameters when the pores are elliptical.

[0024] Examples of embodiments in which the porous structure has a pore size distribution from one main surface to the other main surface include an embodiment in which the pore size continuously increases (or decreases) from one main surface of the porous structure to the other main surface; an embodiment in which the pore size continuously increases from any interior of the porous structure (for example, the center position; a position 1 / 3 of the way from one main surface in the thickness direction) to the other main surface; and an embodiment in which the pore size continuously decreases from one main surface of the porous structure to the interior, there is a region inside where the pore size is smallest (hereinafter also referred to as the "smallest pore size region"), and the pore size continuously increases from the smallest pore size region to the other main surface.

[0025] The continuous increase in pore size and the continuous decrease in pore size can be confirmed by comparing the average pore sizes in adjacent cross sections. The term "continuously increasing" essentially means a uniform increase without any decrease, but the decrease may occur accidentally. Similarly, the term "continuously decreasing" essentially means a uniform decrease without any increase, but the increase may occur accidentally.

[0026] The pores in the porous structure preferably have a smaller internal pore size than the surface pore size. Specifically, it is more preferable that the pore size continuously decreases from one main surface of the porous structure to the other main surface, that a minimum pore size portion exists in the interior, and that the pore size continuously increases from the minimum pore size portion toward the other end surface.

[0027] The minimum pore diameter of the plurality of pores in the porous structure is preferably 0.001 μm to 10 μm, more preferably 0.05 μm to 7 μm. The porous film is virtually divided into a plurality of sections in a direction perpendicular to the thickness direction of the porous film, and the minimum value among the average pore diameters in each section is defined as the "minimum pore diameter."

[0028] The maximum pore diameter of the multiple pores in the porous structure is preferably 0.1 μm to 25 μm, and more preferably 0.5 μm to 20 μm. The porous film is virtually divided into multiple sections in a direction perpendicular to the thickness direction of the porous film, and the maximum value of the average pore diameters in each cross section is defined as the "maximum pore diameter."

[0029] The thickness of the porous structure is not particularly limited, but when the porous structure is used as an independent membrane, it is preferably 10 μm to 1000 μm, more preferably 30 μm to 300 μm, from the viewpoint of film strength.

[0030] The porous structure preferably contains a polymer. The porous structure may contain only one type of polymer, or may contain two or more types of polymer.

[0031] The type of polymer is not particularly limited, and known polymers can be used.

[0032] From the viewpoints of heat resistance and dimensional stability during long-term use, the polymer preferably has a glass transition temperature of 150° C. or higher, more preferably 180° C. or higher. The upper limit of the glass transition temperature is not particularly limited, but is, for example, 300° C. Note that depending on the type of polymer, the glass transition temperature may not be observed.

[0033] The glass transition temperature is measured using a differential scanning calorimetry (DSC) analyzer. 5 mg of a sample is placed in the DSC measurement pan, and the temperature is raised from 30°C at a rate of 10°C / min in a nitrogen stream. The midpoint of the inflection of the baseline that appears when the sample is heated can be taken as the glass transition temperature.

[0034] Examples of polymers include liquid crystal polymers, polyesters, polycarbonates, acrylic resins, polystyrenes, polyolefins, polyamides, polyimides, polysulfones, polyethersulfones, polyetheretherketones, polyphenylene sulfides, polyvinyl alcohols, polyvinylidene chloride, epoxy resins, and fluororesins.

[0035] In particular, from the viewpoint of improving adhesion, the polymer preferably contains at least one selected from the group consisting of liquid crystal polymers and polysulfones.

[0036] -Liquid Crystal Polymer- The type of liquid crystal polymer is not particularly limited, and any known liquid crystal polymer can be used. The liquid crystal polymer may be a thermotropic liquid crystal polymer that exhibits liquid crystallinity in a molten state, or a lyotropic liquid crystal polymer that exhibits liquid crystallinity in a solution state. In the case of a thermotropic liquid crystal, it is preferable that the polymer melts at a temperature of 450°C or less.

[0037] Examples of liquid crystal polymers include liquid crystal polyester, liquid crystal polyester amide in which an amide bond is introduced into liquid crystal polyester, liquid crystal polyester ether in which an ether bond is introduced into liquid crystal polyester, and liquid crystal polyester carbonate in which a carbonate bond is introduced into liquid crystal polyester.

[0038] From the viewpoint of liquid crystallinity, the liquid crystal polymer is preferably a polymer having an aromatic ring, and more preferably an aromatic polyester or an aromatic polyester amide.

[0039] Furthermore, the liquid crystal polymer may be a polymer in which an imide bond, a carbodiimide bond, an isocyanate-derived bond such as an isocyanurate bond, or the like is further introduced into an aromatic polyester or an aromatic polyester amide.

[0040] The liquid crystal polymer is preferably a wholly aromatic liquid crystal polymer made using only aromatic compounds as raw material monomers.

[0041] Examples of liquid crystal polymers include the following: 1) A compound obtained by polycondensation of (i) an aromatic hydroxycarboxylic acid, (ii) an aromatic dicarboxylic acid, and (iii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 2) A compound obtained by polycondensation of multiple types of aromatic hydroxycarboxylic acids. 3) (i) A compound obtained by polycondensation of an aromatic dicarboxylic acid and (ii) at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine. 4) (i) Polyester such as polyethylene terephthalate and (ii) aromatic hydroxycarboxylic acid are polycondensed. Here, the aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid, aromatic diol, aromatic hydroxyamine and aromatic diamine may each independently be replaced in part or in whole by a polycondensable derivative thereof.

[0042] Examples of polymerizable derivatives of compounds having a carboxy group, such as aromatic hydroxycarboxylic acids and aromatic dicarboxylic acids, include those in which the carboxy group is converted to an alkoxycarbonyl group or an aryloxycarbonyl group (esters), those in which the carboxy group is converted to a haloformyl group (acid halides), and those in which the carboxy group is converted to an acyloxycarbonyl group (acid anhydrides). Examples of polymerizable derivatives of compounds having a hydroxy group, such as aromatic hydroxycarboxylic acids, aromatic diols, and aromatic hydroxyamines, include those obtained by acylation of the hydroxy group to convert it into an acyloxy group (acylated products). Examples of polymerizable derivatives of compounds having an amino group, such as aromatic hydroxyamines and aromatic diamines, include those obtained by acylation of the amino group to convert it into an acylamino group (acylated product).

[0043] From the viewpoint of liquid crystallinity, the liquid crystal polymer preferably has a constitutional unit represented by any one of the following formulas (1) to (3) (hereinafter, a constitutional unit represented by formula (1) etc. may be referred to as unit (1) etc.), more preferably has a constitutional unit represented by formula (1) below, and particularly preferably has a constitutional unit represented by formula (1) below, a constitutional unit represented by formula (2) below, and a constitutional unit represented by formula (2) below. Formula (1) -O-Ar 1 -CO- Formula (2) -CO-Ar 2 -CO- Formula (3) -X-Ar 3 -Y- In formulas (1) to (3), Ar 1 represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar 2 and Ar 3 each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, Ar 1 ~Ar 3 Each hydrogen atom in the group represented by the formula (I) may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Formula (4) -Ar 4 -Z-Ar 5 - In formula (4), Ar 4 and Ar 5 each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group.

[0044] The halogen atom includes a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, and an n-decyl group, and the number of carbon atoms thereof is preferably 1 to 10. Examples of the aryl group include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group, and the number of carbon atoms therein is preferably 6 to 20. When the hydrogen atoms are substituted with these groups, the number of the groups is 1 , Ar 2 or Ar 3 The number of the groups represented by the formula (I) is preferably two or less, and more preferably one.

[0045] Examples of the alkylene group include a methylene group, a 1,1-ethanediyl group, a 1-methyl-1,1-ethanediyl group, a 1,1-butanediyl group, and a 2-ethyl-1,1-hexanediyl group, and the number of carbon atoms is preferably 1 to 10.

[0046] The unit (1) is a structural unit derived from a specific aromatic hydroxycarboxylic acid. Unit (1) is Ar 1 is a p-phenylene group (a structural unit derived from p-hydroxybenzoic acid), and Ar 1 is preferably a 2,6-naphthylene group (a structural unit derived from 6-hydroxy-2-naphthoic acid) or a 4,4'-biphenylylene group (a structural unit derived from 4'-hydroxy-4-biphenylcarboxylic acid).

[0047] The unit (2) is a structural unit derived from a specific aromatic dicarboxylic acid. Unit (2) is Ar 2 is a p-phenylene group (a structural unit derived from terephthalic acid), Ar 2 is an m-phenylene group (a structural unit derived from isophthalic acid), Ar 2 is a 2,6-naphthylene group (a structural unit derived from 2,6-naphthalenedicarboxylic acid), or Ar 2 is a diphenylether-4,4'-diyl group (a structural unit derived from diphenylether-4,4'-dicarboxylic acid) is preferred.

[0048] The unit (3) is a structural unit derived from a specific aromatic diol, aromatic hydroxylamine, or aromatic diamine. Unit (3) is Ar 3 is a p-phenylene group (structural unit derived from hydroquinone, p-aminophenol or p-phenylenediamine), Ar 3 is an m-phenylene group (a structural unit derived from isophthalic acid), or Ar 3 is a 4,4'-biphenylylene group (a structural unit derived from 4,4'-dihydroxybiphenyl, 4-amino-4'-hydroxybiphenyl or 4,4'-diaminobiphenyl).

[0049] The content of unit (1) is preferably 30 mol% or more, more preferably 30 mol% to 80 mol%, even more preferably 30 mol% to 60 mol%, and particularly preferably 30 mol% to 40 mol% of the total amount of all structural units (the value obtained by dividing the mass of each structural unit constituting the liquid crystal polymer by the formula weight of that unit to determine the substance equivalent (mol) of each unit, and then adding them up). The content of the unit (2) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all structural units. The content of the unit (3) is preferably 35 mol % or less, more preferably 10 mol % to 35 mol %, even more preferably 20 mol % to 35 mol %, and particularly preferably 30 mol % to 35 mol %, based on the total amount of all structural units. The greater the content of the unit (1), the more likely it is that the heat resistance, strength and rigidity will improve, but if the content is too high, the solubility in solvents will tend to decrease.

[0050] The ratio of the content of units (2) to the content of units (3), expressed as [content of units (2)] / [content of units (3)] (mol / mol), is preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and even more preferably 0.98 / 1 to 1 / 0.98.

[0051] The liquid crystal polymer may have two or more types of units (1) to (3) independently. The liquid crystal polymer may also have structural units other than units (1) to (3), but the content of such units is preferably 10 mol % or less, more preferably 5 mol % or less, based on the total amount of all units.

[0052] The liquid crystal polymer preferably has, as the unit (3), one in which at least one of X and Y is an imino group, that is, one in which at least one of a structural unit derived from a specific aromatic hydroxylamine and a structural unit derived from an aromatic diamine, because this provides excellent solubility in a solvent. It is more preferable that the liquid crystal polymer has, as the unit (3), only one in which at least one of X and Y is an imino group.

[0053] The liquid crystal polymer is preferably produced by melt-polymerizing the raw material monomers corresponding to the structural units constituting the polymer. The melt-polymerization may be carried out in the presence of a catalyst. Examples of the catalyst include metal compounds such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide, and nitrogen-containing heterocyclic compounds such as 4-(dimethylamino)pyridine and 1-methylimidazole. Nitrogen-containing heterocyclic compounds are preferably used. The melt-polymerization may be further subjected to solid-phase polymerization if necessary.

[0054] The liquid crystal polymer has a flow initiation temperature of preferably 250° C. or higher, more preferably 250° C. or higher and 350° C. or lower, and even more preferably 260° C. or higher and 330° C. or lower. When the flow initiation temperature of the liquid crystal polymer is within the above range, the polymer has excellent solubility, heat resistance, strength, and rigidity, and the viscosity of the solution is appropriate.

[0055] The flow initiation temperature is also called the flow temperature or flow temperature, and is measured using a capillary rheometer at 9.8 MPa (100 kg / cm 2When a liquid crystal polymer is melted and extruded through a nozzle with an inner diameter of 1 mm and a length of 10 mm while heating at a rate of 4°C / min under a load of 1000 kJ / s, the temperature at which the polymer shows a viscosity of 4,800 Pa·s (48,000 poise) is measured. This temperature is an indicator of the molecular weight of the liquid crystal polymer (see "Liquid Crystal Polymer - Synthesis, Molding, and Applications," edited by Naoyuki Koide, CMC Corporation, June 5, 1987, p. 95).

[0056] Furthermore, the liquid crystal polymer preferably has a weight-average molecular weight of 1,000,000 or less, more preferably 3,000 to 300,000, even more preferably 5,000 to 100,000, and particularly preferably 5,000 to 30,000. When the weight-average molecular weight of the liquid crystal polymer is within the above range, the film after heat treatment has excellent thermal conductivity in the thickness direction, heat resistance, strength, and rigidity.

[0057] The polymer content is preferably 70% by volume or more, more preferably 80% by volume or more, and even more preferably 90% by volume or more, relative to the total volume of the porous structure. The upper limit of the polymer content is not particularly limited, and may be 100% by mass.

[0058] -Other additives- The porous structure may contain additives other than the polymer as long as the effects of the present disclosure are not significantly impaired.

[0059] As the other additives, known additives can be used, such as fillers, leveling agents, antifoaming agents, antioxidants, ultraviolet absorbers, flame retardants, and colorants.

[0060] <Coating layer> The porous film according to the present disclosure includes a coating layer that covers at least a portion of the inner wall of the porous structure.

[0061] The inner wall of the porous structure means the surface of the pores formed in the porous structure. The coating layer may cover only a part of the surface of the pores, or may cover the entire surface of the pores.

[0062] The area ratio of the coating layer on the inner wall of the porous structure is preferably 30% or more, more preferably 60% or more, and even more preferably 85% or more, relative to the total surface area of ​​the inner wall. The upper limit of the area ratio is not particularly limited and may be 100%. When the area ratio is 30% or more, the function of the coating layer can be efficiently exerted. In addition, there is an effect of increasing the frequency at which the coating layers form a continuous phase, thereby improving strength.

[0063] The area ratio is expressed by the following formula. Area ratio (%) = (area of ​​coating layer / total surface area of ​​inner wall of porous structure) × 100

[0064] The area of ​​the coating layer and the total surface area of ​​the inner walls of the porous structure are measured by the following method. The porous film is cut using a microtome or the like to prepare multiple samples for cross-sectional evaluation. The cross-section of each sample is observed using a scanning electron microscope, X-ray photoelectron spectroscopy imaging, time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging, infrared spectroscopy imaging, Raman imaging, or the like to measure the area of ​​the coating layer and the total surface area of ​​the inner walls of the porous structure.

[0065] The coating layer preferably contains a conductor or a catalyst from the viewpoint of imparting functionality to the porous film.

[0066] Examples of the conductor or catalyst include metals, metal phosphides, and metal oxides. The conductor or catalyst may be an organic compound. Among them, the conductor or catalyst is preferably at least one selected from the group consisting of platinum, iridium, rhodium, ruthenium, palladium, silver, copper, tantalum, nickel, iron phosphide, nickel phosphide, and iridium oxide.

[0067] The average thickness of the coating layer is not particularly limited, but from the viewpoint of achieving both functionality and cost, it is preferably 0.001 μm to 10 μm, more preferably 0.01 μm to 1 μm, and even more preferably 0.03 μm to 0.5 μm.

[0068] The average thickness of the coating layer is calculated by the following method. First, a porous film is cut using a microtome or the like to prepare multiple cross-sectional evaluation samples. The cross-section of each sample is observed using a scanning electron microscope, X-ray photoelectron spectroscopy imaging, infrared spectroscopy imaging, Raman imaging, or the like, and the thickness of the coating layer is measured. The average value of the measured thicknesses is taken as the average thickness.

[0069] From the viewpoint of strength, the average thickness of the porous film according to the present disclosure is preferably 10 μm to 1000 μm, more preferably 10 μm to 500 μm, and even more preferably 30 μm to 300 μm.

[0070] The average thickness of the porous film is determined by measuring any five points using an adhesive film thickness meter, for example, an electronic micrometer (product name "KG3001A" manufactured by Anritsu Corporation), and averaging these values.

[0071] <Method of manufacturing porous film> The method for producing a porous film according to the present disclosure includes, for example, the following steps. (1) A step of casting a solution of a polymer and a compound incompatible with the polymer in a solvent onto a support to form a membrane A (casting step). (2) A step of immersing membrane A in a coagulation bath to form membrane B (immersion step) (3) A step of eluting compounds incompatible with the polymer from membrane B to prepare a porous structure (elution step). (4) A step of firing the porous structure (firing step) (5) A step of impregnating the fired porous structure with a coating layer forming solution (impregnation step)

[0072] (Casting process) The casting step is a step of forming a membrane A by casting a solution in which a polymer and a compound incompatible with the polymer are dissolved in a solvent onto a support.

[0073] The casting method in the casting step is not particularly limited, and any known casting method can be used.

[0074] There are no particular limitations on the casting temperature and casting speed, and they may be determined with reference to known casting methods and the composition of the solution used.

[0075] The average thickness of the film A is not particularly limited as long as it is a desired thickness, but is preferably 0.1 μm to 10 mm, more preferably 1 μm to 5 mm, even more preferably 10 μm to 1,000 μm, and particularly preferably 50 μm to 500 μm.

[0076] Examples of the support include a metal drum, a metal band, a glass plate, a resin film, and a metal foil, and among these, the support is preferably a glass plate or a resin film.

[0077] The polymer preferably includes at least one selected from the group consisting of liquid crystal polymers and polysulfones.

[0078] The compound that is incompatible with the polymer is not particularly limited as long as it is a compound that can undergo phase separation when the film A is formed, but it is preferably water-soluble from the viewpoint of ease of elution. In the present disclosure, "water-soluble" means that 0.1 g or more can be dissolved in 100 g of water at 25°C.

[0079] The compound that is incompatible with the polymer may be a low-molecular-weight compound having a molecular weight of less than 1,000, or may be a high-molecular-weight compound having a weight-average molecular weight Mw of 1,000 or more. From the viewpoints of pore-forming ability and ease of elution, however, it is preferably a high-molecular-weight compound having a weight-average molecular weight Mw of 1,000 or more, and more preferably a water-soluble resin.

[0080] Examples of water-soluble resins include polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, poly(N-vinylacetamide), water-soluble polyester, and water-soluble polyurethane. Among these, the compound incompatible with the first polymer is preferably polyvinylpyrrolidone.

[0081] The solvent is not particularly limited as long as it can dissolve the polymer and the compound that is incompatible with the polymer.

[0082] <Soaking process> The immersion step is a step in which Membrane A is immersed in a coagulation bath to form Membrane B.

[0083] The components of the coagulation bath are not particularly limited, but from the viewpoint of coagulation properties and thermal conductivity, water, a polar solvent, or a mixed solvent of water and a polar solvent is preferable, water or a mixed solvent of water and a polar solvent is more preferable, and water is particularly preferable.

[0084] Polar solvents for use in the coagulation bath include dioxane, tetrahydrofuran, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, cellosolves, methanol, ethanol, propanol, acetone, tetrahydrofuran, polyethylene glycol, and glycerin.

[0085] From the viewpoint of coagulation properties, the temperature of the coagulation bath is preferably 0°C to 50°C, more preferably 10°C to 35°C, and particularly preferably 20°C to 30°C.

[0086] The immersion time is not particularly limited and may be selected appropriately.

[0087] In addition, the method for producing a porous film according to the present disclosure preferably includes, after the casting step and before the immersion step, a step of exposing the membrane A to a gas. By adjusting the time for exposing the membrane A to the gas, it is possible to adjust the average pore size on the side opposite to the support (also referred to as the air side) of the resulting porous structure.

[0088] The gas is not particularly limited, but air is preferred.

[0089] The temperature of the gas is preferably 0° C. to 50° C., more preferably 10° C. to 35° C., and particularly preferably 20° C. to 30° C. The relative humidity of the gas is preferably 30% to 90%, more preferably 35% to 80%, and particularly preferably 40% to 70%.

[0090] The time for which the gas is applied is not particularly limited, and may be selected so as to obtain a desired average pore size.

[0091] Furthermore, the method for producing a porous film according to the present disclosure preferably includes a step of peeling off the membrane B from the support during or after the immersion step. The peeling may be carried out in the coagulation bath or outside the coagulation bath. The peeling method is not particularly limited, and can be carried out by a known method. The temperature during peeling is not particularly limited, but is preferably 0°C to 50°C. The peeling speed is not particularly limited and can be selected appropriately.

[0092] <Elution process> The elution step is a step of eluting compounds that are incompatible with the polymer from membrane B to produce a porous structure.

[0093] As the elution method in the elution step, a method of bringing the membrane B into contact with the elution solution is preferred, and a method of immersing the membrane B in the elution solution is more preferred.

[0094] The eluent may be any compound that does not dissolve the polymer but dissolves compounds that are incompatible with the polymer at a certain temperature, but is preferably a water-soluble solvent from the viewpoint of selective elution.

[0095] Examples of water-soluble solvents include glycerin, 1,2,6-hexanetriol, trimethylolpropane, and alkanediols (e.g., ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, and 4-methyl-1,2-pentanediol). and polyhydric alcohols such as polyalkylene glycols (e.g., diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, polyoxyethylene polyoxypropylene glycol, etc.); and polyhydric alcohol ethers such as polyalkylene glycol ethers (e.g., diethylene glycol monoalkyl ether, triethylene glycol monoalkyl ether, tripropylene glycol monoalkyl ether, polyoxypropylene glyceryl ether, etc.).

[0096] Among these, from the viewpoint of selective elution, the water-soluble solvent is preferably a polyhydric alcohol or a polyhydric alcohol ether, more preferably a polyhydric alcohol, further preferably a polyalkylene glycol, and particularly preferably diethylene glycol.

[0097] The elution temperature in the elution step depends on the solubility of the polymer, etc., and the boiling point and melting point of the eluent used, but is preferably 20°C to 150°C, more preferably 50°C to 100°C, and particularly preferably 60°C to 90°C.

[0098] The elution time in the elution step is not particularly limited, but is preferably 0.1 minutes to 24 hours, more preferably 0.5 minutes to 60 minutes, and particularly preferably 1 minute to 10 minutes.

[0099] The method for producing a porous film according to the present disclosure preferably includes a step of washing the porous structure after the elution step.

[0100] In addition, the method for producing a porous film according to the present disclosure preferably includes a step of drying the porous structure after the elution step or after the step of washing the porous structure.

[0101] The cleaning liquid used for cleaning is not particularly limited, but is preferably water, a polar solvent, or a mixed solvent of water and a polar solvent, more preferably water, or a mixed solvent of water and a polar solvent, and particularly preferably water. The washing temperature and washing time are not particularly limited and can be selected appropriately. The cleaning means is not particularly limited, and any known cleaning means can be used.

[0102] The drying temperature and drying time are not particularly limited and can be selected appropriately. The drying means is not particularly limited, and any known drying means can be used.

[0103] (Firing process) The firing step is a step of firing the porous structure.

[0104] The firing temperature is not particularly limited, but is preferably 200 to 400°C, and more preferably 250 to 300°C.

[0105] The firing time is not particularly limited, but is preferably 0.1 to 5 hours, and more preferably 2 to 4 hours.

[0106] The firing is preferably carried out in an inert gas atmosphere, such as nitrogen.

[0107] (Impregnation process) The impregnation step is a step in which the fired porous structure is impregnated with a coating layer forming solution.

[0108] The solution for forming the coating layer is preferably an electroless plating solution, and known solutions can be used as the electroless plating solution.

[0109] In addition, the method for producing a porous film according to the present disclosure preferably includes a step of drying the obtained porous film after the impregnation step.

[0110] The drying temperature and drying time are not particularly limited and can be selected appropriately. The drying means is not particularly limited, and any known drying means can be used.

[0111] In the impregnation step, the electroless plating solution enters the pores formed in the porous structure, thereby forming a coating layer on the inner wall of the porous structure.

[0112] -Applications- The porous film according to the present disclosure can be used in various applications, particularly as an electrode, and can also be used as an electrolyte membrane.

[0113] The porous film according to the present disclosure can also be suitably used as an adhesive film.

[0114] [Laminate] The laminate according to the present disclosure may be any laminate including the porous film according to the present disclosure. The laminate according to the present disclosure preferably includes the porous film according to the present disclosure and a layer disposed on at least one surface of the porous film. The layer disposed on at least one surface of the porous film is not particularly limited, and examples thereof include a polymer layer and a metal layer. The layer disposed on at least one surface of the porous film may be a coating layer.

[0115] Furthermore, the layer disposed on at least one surface of the porous film may be disposed on the entire surface of the porous film, or may be disposed on only a part of the porous film.

[0116] In particular, it is preferable that the porous film according to the present disclosure is used as an electrode, and that the laminate according to the present disclosure includes a porous film as an electrode and an electrolyte membrane disposed on the porous film.

[0117] The method for attaching the porous film according to the present disclosure to the electrolyte membrane is not particularly limited, and any known lamination method can be used.

[0118] The peel strength between the porous film and the electrolyte membrane is preferably 0.5 kN / m or more, more preferably 0.7 kN / m or more, even more preferably 0.7 kN / m to 2.0 kN / m, and particularly preferably 0.9 kN / m to 1.5 kN / m.

[0119] In the present disclosure, the peel strength between the porous film and the electrolyte membrane is measured by the following method.

[0120] A 1.0 cm wide peel test piece is prepared from the laminate of the porous film and the electrolyte membrane, and the porous film is fixed to a flat plate with double-sided adhesive tape. The strength (kN / m) is measured when the porous film is peeled from the electrolyte membrane at a rate of 50 mm / min using the 180° method in accordance with JIS C 5016 (1994).

[0121] Furthermore, the porous film according to the present disclosure is used as an adhesive film, and the laminate according to the present disclosure preferably includes a metal layer, a porous film as an adhesive film, and a resin layer in this order.

[0122] The method for attaching the porous film according to the present disclosure to the metal layer, and the porous film according to the present disclosure to the resin layer is not particularly limited, and any known lamination method can be used.

[0123] Examples of the laminate include a three-layer structure of metal layer / porous film / resin layer and a five-layer structure of metal layer / porous film / resin layer / porous film / metal layer. [Example]

[0124] The present disclosure will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific examples shown below.

[0125] <<Measurement method>> [Pore size distribution] The porous film was cut with a microtome to prepare three samples for cross-sectional evaluation. The holes formed on both end surfaces of the porous film in the thickness direction and the holes formed on the three cross sections were observed using a scanning electron microscope. The hole diameters of 50 randomly selected holes on each cross section were measured, and the average hole diameter was calculated. When the maximum value of the calculated average hole diameter was 1.1 times or more the minimum value, the porous film was determined to have a hole diameter distribution in the thickness direction.

[0126] [Area ratio of the coating layer on the inner wall of the porous structure] The porous film was cut with a microtome to prepare cross-sectional samples, and the cross-sections were imaged and measured using X-ray photoelectron spectroscopy (XPS) or time-of-flight secondary ion mass spectrometry (TOF-SIMS). The total surface area of ​​the inner wall and the area of ​​the coating layer were measured from the five sample images, and the area ratio was calculated using the following formula. Note that when the coating layer material was inorganic, the XPS results took priority, and when it was organic, the TOS-SIMS results took priority. Area ratio (%) = (area of ​​coating layer / total surface area of ​​inner wall of porous structure) × 100

[0127] [Peel strength] A 1.0 cm wide peel test piece was prepared from the laminate of the porous film and the electrolyte membrane, and the porous film was fixed to a flat plate with double-sided adhesive tape. The strength (kN / m) was measured when the porous film was peeled from the electrolyte membrane at a rate of 50 mm / min using the 180° method in accordance with JIS C 5016 (1994).

[0128] <Polymers used to prepare porous films> LC-A: Liquid crystal polymer prepared according to the following manufacturing method

[0129] -Production of LC-A- A reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer, and a reflux condenser was charged with 940.9 g (5.0 mol) of 6-hydroxy-2-naphthoic acid, 377.9 g (2.5 mol) of 4-hydroxyacetaminophen, 415.3 g (2.5 mol) of isophthalic acid, and 867.8 g (8.4 mol) of acetic anhydride. The gas in the reactor was replaced with nitrogen gas, and the mixture was heated from room temperature (23°C) to 140°C over 60 minutes while stirring under a nitrogen gas stream, and then refluxed at 140°C for 3 hours. Next, while distilling off by-product acetic acid and unreacted acetic anhydride, the temperature was raised from 150°C to 300°C over 5 hours, and after holding at 300°C for 30 minutes, the contents were removed from the reactor and cooled to room temperature. The resulting solid was pulverized in a pulverizer to obtain a powdered liquid crystalline polyester (B1). The flow initiation temperature of this liquid crystalline polyester (B1) was 193.3°C.

[0130] The liquid crystal polyester (B1) obtained above was heated in a nitrogen atmosphere from room temperature to 160°C over 2 hours and 20 minutes, then heated from 160°C to 180°C over 3 hours and 20 minutes, and held at 180°C for 5 hours to undergo solid-state polymerization. The mixture was then cooled and pulverized in a pulverizer to obtain powdered liquid crystal polyester (B2). The flow initiation temperature of this liquid crystal polyester (B2) was 220°C.

[0131] The liquid crystalline polyester (B2) obtained above was heated in a nitrogen atmosphere from room temperature (23°C) to 180°C over 1 hour 25 minutes, then heated from 180°C to 255°C over 6 hours 40 minutes, and held at 255°C for 5 hours to undergo solid-state polymerization. The resulting mixture was then cooled to obtain a powdered liquid crystalline polyester (LC-A). The flow initiation temperature of the liquid crystalline polyester (LC-A) was 302°C. The melting point of this liquid crystalline polyester (LC-A) was measured using a differential scanning calorimeter (DSC8230, manufactured by Rigaku Corporation) and found to be 311°C.

[0132] PVP-A: Polyvinylpyrrolidone (product name "Pitzcol K-50", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used. Note that PVP-A is a compound that is not compatible with LC-A at temperatures between 0°C and 100°C. PSU-A: Polysulfone (product name "Udel P-3500", manufactured by Solvay Japan Co., Ltd.) was used. PAI-A: A polyamideimide resin solution (trade name "Vylomax HR-11NN", manufactured by Toyobo Co., Ltd., solid content concentration 15% by mass, N-methyl-2-pyrrolidone solution) was used.

[0133] Example 1 -Preparation of polymer solution- LC-A was added to N-methylpyrrolidone and stirred at 140° C. for 4 hours under a nitrogen atmosphere to obtain a solution with a solid content of 12% by mass. Next, 87 parts by mass of PVP-A, 7 parts by mass of lithium chloride, and 8 parts by mass of water were added to 100 parts by mass of LC-A and dissolved uniformly. Subsequently, the mixture was passed through a sintered fiber metal filter having a nominal pore size of 10 μm, and then through a sintered fiber filter also having a nominal pore size of 10 μm to obtain a polymer solution.

[0134] -Film forming- The polymer solution was cast onto a glass plate using a casting coater to a thickness of 140 μm after drying (casting process). LC-A and PVP-A were phase-separated, and the liquid film had a bicontinuous structure. Air adjusted to a temperature of 25°C and a relative humidity of 50% was blown onto the surface of the cast liquid film at a wind speed of 1.2 m / sec. The glass plate on which the film had been formed was then immediately immersed in a coagulation bath filled with water at 25°C (immersion process). After solidification, the obtained film was peeled off from the glass plate in water, washed in diethylene glycol at 75°C for 5 minutes to elute PVP-A (elution step), and then washed with water and dried.

[0135] -Firing- The membrane after the elution process was heated at 280°C in a nitrogen atmosphere for 3 hours to obtain a porous structure (firing process). The porous structure had multiple pores on the surface and inside, and it was found that the multiple pores had a pore size distribution from one main surface to the other. It was also found that the pore size of the multiple pores was smaller in the inside than in the surface.

[0136] -Coating- The obtained porous structure was immersed in an electroless platinum plating solution for 10 minutes (impregnation step). A porous film was obtained in which a platinum coating was formed on the surface of the porous structure and on the inner walls of the pores of the porous structure. The area ratio of the coating layer on the inner walls of the porous structure was 99%.

[0137] -Making laminates- A polymer electrolyte membrane was produced according to Example 1 of JP 2018-60789 A. Two of the above porous films were produced to serve as electrodes. The polymer electrolyte membrane was sandwiched between two electrodes (the above porous films) and heat-pressed to obtain a membrane electrode assembly. The obtained membrane electrode assembly had a porous film / polymer electrolyte membrane / porous film structure. It was confirmed that the peel strength between the polymer electrolyte membrane and the porous film in the obtained membrane electrode assembly was 0.5 kN / m or more.

[0138] Example 2 A porous film was obtained in the same manner as in Example 1.

[0139] -Making laminates- A polymer electrolyte membrane was produced in accordance with Example 1 of JP 2018-60789 A. A platinum plate with a surface roughness (Rz) of 0.9 μm was also prepared.

[0140] The polymer electrolyte membrane was sandwiched between two electrodes (the porous films), and platinum plates were attached to the outside of each porous film and then heated and pressed to obtain a membrane electrode assembly. The resulting membrane electrode assembly had a platinum plate / porous film / polymer electrolyte membrane / porous film / platinum plate structure. It was confirmed that the peel strength between the polymer electrolyte membrane and the porous film in the resulting membrane electrode assembly was 0.5 kN / m or more.

[0141] Example 3 A polymer solution was obtained in the same manner as in Example 1, except that the LC-A used in Example 1 was replaced with PSU-A, and PSU-A was added to N-methylpyrrolidone and stirred at 140°C for 4 hours under a nitrogen atmosphere to obtain a solution with a solids concentration of 20% by mass. The casting, immersion, and elution processes were then performed in the same manner as in Example 1, and a porous structure was obtained without performing a baking process. The porous structure had multiple pores on the surface and inside, and it was found that the multiple pores had a pore size distribution from one main surface to the other. It was also found that the pore size of the multiple pores was smaller in the interior than in the surface. The impregnation step was carried out in the same manner as in Example 1 to obtain a porous film in which a platinum coating was formed on the surface of the porous structure and on the inner walls of the pores of the porous structure. The area ratio of the coating layer on the inner walls of the porous structure was 98%.

[0142] -Making laminates- Using the obtained porous film, a membrane electrode assembly was obtained in the same manner as in Example 1. The obtained membrane electrode assembly had a structure of porous film / polymer electrolyte membrane / porous film. It was confirmed that the peel strength between the polymer electrolyte membrane and the porous film in the obtained membrane electrode assembly was 0.5 kN / m or more.

[0143] Example 4 A porous film was obtained in the same manner as in Example 3.

[0144] -Making laminates- Using the obtained porous film, a membrane electrode assembly was obtained in the same manner as in Example 2. The obtained membrane electrode assembly had a structure of platinum plate / porous film / polymer electrolyte membrane / porous film / platinum plate. It was confirmed that the peel strength between the polymer electrolyte membrane and the porous film in the obtained membrane electrode assembly was 0.5 kN / m or more.

[0145] (Comparative Example 1) A polymer electrolyte membrane was produced according to Example 1 of JP 2018-60789 A. A platinum plate with a surface roughness (Rz) of 0.9 μm was also prepared. The polymer electrolyte membrane was sandwiched between two platinum plates and heat-pressed to obtain a membrane electrode assembly. The obtained membrane electrode assembly had a platinum plate / polymer electrolyte membrane / platinum plate structure. It was confirmed that the peel strength between the polymer electrolyte membrane and the platinum plate in the obtained membrane electrode assembly was 0.1 kN / m.

[0146] From the above, it has been found that a porous film comprising a porous structure having a plurality of pores inside and on its surface, and a coating layer covering at least a portion of the inner wall of the porous structure, in which the plurality of pores have a pore size distribution from one main surface of the porous structure to the other main surface, has excellent adhesion.

[0147] (Comparative Example 2) 35 parts by weight of polyvinylpyrrolidone (molecular weight 55,000) was added to 100 parts by weight of the PAI-A solution to prepare a film stock solution, which was then cast onto a PET (polyethylene terephthalate) film and immediately placed in an environment of approximately 100% humidity and 50°C for 4 minutes. Thereafter, the PET film on which the membrane was formed was immersed in a coagulation bath filled with water. After solidification, the resulting membrane was peeled off from the PET film in water. After washing in water to elute the PAI-A, the membrane was air-dried, yielding a porous structure approximately 50 μm thick. When the obtained porous structure was observed under an electron microscope, it was found that the average pore size of the pores on the surface of the porous structure was approximately 0.5 μm, and that the interior of the porous structure was almost homogeneous, with micropores in a continuous phase with an average pore size of approximately 0.5 μm present throughout the entire area. When the impregnation step was carried out in the same manner as in Example 1, clogging of the plating solution occurred near the surface of the porous structure, and the area ratio of the coating layer on the inner wall of the porous structure was 20%.

Claims

1. a porous structure having a plurality of pores inside and on a surface thereof; a coating layer that coats at least a portion of the inner wall of the porous structure, the plurality of pores have a pore size distribution from one main surface of the porous structure to the other main surface, The plurality of holes have an internal pore size smaller than a surface pore size, the coating layer includes a conductor or a catalyst; the porous structure comprises a polymer; A porous film, wherein the polymer comprises a liquid crystal polymer.

2. The porous film according to claim 1 , wherein an area ratio of the coating layer on the inner wall of the porous structure is 30% or more with respect to a total surface area of ​​the inner wall.

3. The conductor or catalyst is at least one selected from the group consisting of platinum, iridium, rhodium, ruthenium, palladium, silver, copper, tantalum, nickel, iron phosphide, nickel phosphide, and iridium oxide. The porous film according to claim 1.

4. The porous film according to any one of claims 1 to 3, wherein the polymer has a glass transition temperature of 150°C or higher.

5. The porous film according to any one of claims 1 to 4, wherein the liquid crystal polymer contains a constitutional unit represented by any one of formulas (1) to (3). Formula (1) -O-Ar １ -CO- Formula (2) -CO-Ar ２ -CO- Formula (3) -X-Ar ３ -Y- In formulas (1) to (3), Ar １ represents a phenylene group, a naphthylene group, or a biphenylylene group; Ar ２ and Ar ３ each independently represents a phenylene group, a naphthylene group, a biphenylylene group, or a group represented by the following formula (4), X and Y each independently represent an oxygen atom or an imino group, Ar １ ~Ar ３ Each hydrogen atom in the group represented by the formula (I) may be independently substituted with a halogen atom, an alkyl group, or an aryl group. Formula (4) -Ar ４ -Z-Ar ５ -[[]]END]] In formula (4), Ar ４ and Ar ５ each independently represents a phenylene group or a naphthylene group, and Z represents an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylene group.

6. The porous film according to any one of claims 1 to 5, which is an electrode.

7. A laminate comprising the porous film according to claim 6 and an electrolyte membrane disposed on the porous film.

8. The porous film according to any one of claims 1 to 5, which is an adhesive film.

9. A laminate comprising a metal layer, the porous film according to claim 8, and a resin layer in this order.