Porous membrane, resist composition purification method, and resist film manufacturing method

Abstract

Provided are: a porous membrane capable of satisfactorily removing minute impurities when used as a filter for removing minute impurities from a liquid; a resist composition purification method using said porous membrane; and a resist film manufacturing method using a resist composition purified using said porous membrane.　This porous membrane, comprising at least one resin component (A) selected from the group consisting of polyimide, polyamide imide, and polyethersulfone, or a resin composition containing the resin component (A), and having an average pore diameter of 9-40 nm and a surface area of 1,500 m2 to 3,500 m2 per 1 m2 of the porous membrane, as calculated on the basis of the specific surface area of the porous film measured by the BET method, is used.

Description

Porous film, method for purifying resist composition, and method for producing resist film

[0001] The present invention relates to a porous film, a method for purifying a resist composition, and a method for producing a resist film.

[0002] Various porous membranes have been used for applications such as filters for separating gases or liquids, etc. Porous membranes are used as filters for removing minute substances contained in cleaning solutions, coating solutions, etc. in the manufacture of semiconductors.

[0003] For example, a known method for producing a porous polyimide film involves coating a substrate with a varnish in which silica particles are dispersed in a solution of polyamic acid or polyimide, and then heating the coated film as necessary to obtain a polyimide film containing silica particles, and then eluting and removing the silica in the polyimide film with hydrogen fluoride water to make it porous (see Patent Document 1).

[0004] Patent No. 5605566

[0005] In the manufacturing of semiconductor devices, processing is becoming increasingly finer every day. As a result, manufacturing yields are declining due to the effects of minute impurities contained in cleaning solutions, coating solutions, etc. Therefore, there is a demand for porous films that can be used as filters to more reliably capture minute impurities.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a porous film that can effectively remove minute impurities when used as a filter for removing minute impurities from a liquid, a method for purifying a resist composition using the porous film, and a method for producing a resist film that uses the resist composition purified using the porous film.

[0007] The present inventors have discovered a porous membrane made of at least one resin component (A) selected from the group consisting of polyimide, polyamideimide, and polyethersulfone, or a resin composition containing the resin component (A), the porous membrane having an average pore size of 9 nm or more and 40 nm or less, and a specific surface area of ​​1 m of the porous membrane calculated based on the specific surface area of ​​the porous membrane measured by the BET method. ２ The surface area per ２More than 3500m ２ The inventors have found that the above problems can be solved by the porous membrane described below, and have completed the present invention. Specifically, the present invention provides the following.

[0008] A first aspect of the present invention is a porous membrane made of at least one resin component (A) selected from the group consisting of polyimide, polyamideimide, and polyethersulfone, or a resin composition containing the resin component (A), wherein the average pore size is 9 nm or more and 40 nm or less, and the specific surface area of ​​the porous membrane is calculated based on the specific surface area of ​​the porous membrane measured by the BET method. ２ The surface area per ２ More than 3500m ２ The following is a porous membrane.

[0009] A second aspect of the present invention is a method for purifying a resist composition, which comprises filtering a liquid resist composition using the porous membrane according to the first aspect.

[0010] A third aspect of the present invention is a method for producing a resist film, comprising: filtering a liquid resist composition using the porous membrane according to the first aspect to purify the resist composition; applying the purified resist composition onto a substrate to form a coating film; and drying the coating film to form a resist film.

[0011] According to the present invention, it is possible to provide a porous film that can effectively remove minute impurities when used as a filter for removing minute impurities from a liquid, a method for purifying a resist composition using the porous film, and a method for producing a resist film that uses the resist composition purified using the porous film.

[0012] <<Porous Membrane>> The porous membrane used as a filter is made of at least one resin component (A) selected from the group consisting of polyimide, polyamideimide, and polyethersulfone, or a resin composition containing the resin component (A).

[0013] The porous membrane preferably has interconnected pores. The interconnected pores are formed by adjacent, connected individual pores (hereinafter sometimes simply referred to as "pores") that impart porosity to the porous membrane. The individual pores are preferably pores having a curved inner surface, as described below, and more preferably spherical or nearly spherical pores, as described below. In the porous membrane, the portions where such individual pores are formed adjacent to each other are interconnected pores. The interconnected pores have a structure in which such individual pores are interconnected. Typically, a plurality of such pores are connected together to form a flow path for the liquid to be purified. The "flow path" is usually formed by a series of individual "pores" and / or "interconnected pores." The individual pores can also be said to be pores formed by removing individual particles present in the resin-particle composite membrane in a later process in the porous membrane manufacturing method described below. The interconnected pores can also be said to be adjacent individual pores formed by removing the particles in a later process at the portion where individual particles present in the resin-particle composite membrane were in contact with each other in the porous membrane manufacturing method described below.

[0014] The porous membrane preferably has communicating holes that have openings on the outer surface of the porous membrane, which communicate the interior of the porous membrane and also have openings on the outer surface on the opposite side (back side) of the porous membrane, ensuring a flow path for a fluid passing through the porous membrane.

[0015] The average pore size of the porous membrane is 9 nm or more and 40 nm or less, and preferably 13 nm or more and 30 nm or less. The average pore size is the average pore size measured by a porometer.

[0016] The average pore size measured by a porometer is the mean flow pore size determined by liquid-liquid phase displacement. The average pore size can be measured, for example, using a PMI Liquid Liquid Porometer LLP-1500A (ultra-low pressure pore size distribution permeability measurement device) in accordance with the pore size distribution measurement test method [half-dry method (ASTM E1294-89)]. Perfluoropolyester (trade name Galwick) and isopropyl alcohol (interfacial tension: 4.6 dyne / cm) are used as test solutions for measuring the average pore size. After filling the pores of the porous membrane with isopropyl alcohol, one main surface of the porous membrane is filled with perfluoropolyester. Compressed air is used to apply pressure to the main surface of the porous membrane filled with perfluoropolyester, gradually increasing the pressure. The measurement temperature is 25°C, and the measurement pressure is in the range of 50 to 500 psi.

[0017] 1 m of the porous membrane, calculated based on the specific surface area of ​​the porous membrane measured by the BET method ２ The surface area per ２ More than 3500m ２ Less than 1800m ２ More than 3000m ２ It is preferable that the thickness of the porous membrane is less than 1 m. ２ The surface area per 1 m of porous membrane ２ The mass (g) per unit area and the specific surface area (m ２ / g).

[0018] When the porous membrane having the average pore size and specific surface area within the above range is used as a filter membrane to filter the liquid containing minute impurities, it can effectively remove minute impurities.It is presumed that this is because the average pore size by BET method is within the above range, it can provide the pores such as interconnected pores with the pore size suitable for the sieving to remove impurities.In addition, it is presumed that the surface area of ​​the porous membrane is within the above range, it can increase the contact frequency between minute impurities and the surface of the pores in the porous membrane, and the removal efficiency of minute impurities by adsorption on the surface of the pores is improved.

[0019] Here, the BET method is a method in which an adsorption isotherm is measured by adsorbing and desorbing adsorbed molecules (e.g., nitrogen) onto a porous body, and the measured data is analyzed based on the BET formula represented by equation (1). Based on this method, the specific surface area A and the total pore volume V can be calculated. Specifically, first, an adsorption isotherm is obtained by adsorbing and desorbing adsorbed molecules onto a porous body. Then, from the obtained adsorption isotherm, [P / {V ａ (P ０ -P)}] and the equilibrium relative pressure (P / P ０ ) and plot it against the value of the slope s (= [(C-1) / (V ｍ C)]) and intercept i (= [1 / (V ｍ Then, V is calculated based on the obtained slope s and intercept i, based on equations (2-1) and (2-2). ｍ and C are calculated. ｍ From this, the specific surface area A can be calculated based on equation (3). Furthermore, the adsorption data of the obtained adsorption isotherm is linearly interpolated to determine the adsorption amount at the relative pressure set as the pore volume calculation relative pressure. The total pore volume V can be calculated from this adsorption amount. Note that this BET method is a measurement method based on JIS R 1626-1996 "Method for measuring the specific surface area of ​​fine ceramic powder by the gas adsorption BET method." There are no particular limitations on the measurement device used in the BET method, but examples include a Micromeritics (manufactured by Shimadzu Corporation).

[0020] [P / {V ａ (P ０ -P)}] = [1 / (V ｍ ・C)]+[(C-1) / (V ｍ · C)] (P / P ０ ) (1) V ｍ =1 / (s+i) (2-1) C=(s / i)+1 (2-2) A=(V ｍ ・L・σ) / 22414 (3)

[0021] However, V ａ : Adsorption amount V ｍ: adsorption amount of monolayer P: pressure at equilibrium of adsorbed molecules P ０ : saturated vapor pressure of adsorbed molecules L: Avogadro's number σ: adsorption cross section of adsorbed molecules

[0022] As described above, the porous membrane is preferably a porous membrane containing pores having a curved inner surface, and more preferably, most (preferably substantially all) of the pores in the porous membrane are formed with a curved surface. In this specification, the phrase "having a curved inner surface" in relation to pores means that at least the inner surface of the pore that creates the porosity has a curved surface in at least a part of the inner surface.

[0023] It is preferable that substantially the entire inner surface of the pores in the porous membrane is a curved surface, and such pores may be referred to as "spherical pores or approximately spherical pores" hereinafter. In this specification, "spherical pores or approximately spherical pores" refers to pores whose inner surface forms a spherical pore or an approximately spherical space. Spherical pores or approximately spherical pores can also be said to be pores formed when the microparticles (b) used in the porous membrane manufacturing method described below are spherical pores or approximately spherical. In this specification, "spherical pores or approximately spherical" is a concept that includes a perfect sphere. The concept of a perfect sphere is not necessarily limited to a perfect sphere, but also includes particles that are substantially spherical. In this specification, "substantially spherical" means that the sphericity, defined by the sphericity expressed by the value of the major axis of the particle divided by the minor axis, is within 1±0.3. The sphericity of the spherical or nearly spherical pores of the porous membrane is preferably 0.9 or more and 1.1 or less, and more preferably 0.95 or more and 1.05 or less.

[0024] By having the pores in the porous membrane have a curved inner surface, when a fluid is passed through the porous membrane, the fluid can be sufficiently distributed inside the pores in the porous membrane and can fully contact the inner surface of the pores. In some cases, it is possible that the fluid may undergo convection along the curved inner surface. For this reason, it is thought that minute substances such as metal particles present in the fluid are easily adsorbed into the pores in the porous membrane or into recesses that may exist on the inner surface of the pores. The spherical or approximately spherical pores may further have recesses on their inner surfaces. For example, the recesses may be formed by pores with a smaller pore diameter than the spherical or approximately spherical pores, which have openings on the inner surface of the spherical or approximately spherical pores.

[0025] The thickness of the porous membrane is preferably 40 μm or more and 90 μm or less, more preferably 50 μm or more and 80 μm or less, from the viewpoint of achieving both an excellent filtration rate and excellent membrane strength.

[0026] As described above, the porous membrane is made of at least one resin component (A) selected from the group consisting of polyimide, polyamideimide, and polyethersulfone, or a resin composition containing the resin component (A). The porous membrane is produced by a production method including forming a composite membrane made of a porous membrane production composition (hereinafter also referred to as "varnish") described below on a substrate, and removing the fine particles (b) from the composite membrane. The porous membrane can be produced by the porous membrane production method described below.

[0027] <Composition for producing porous membrane> The composition for producing porous membrane (varnish) contains at least one resin component (a) selected from the group consisting of polyamic acid, polyimide, polyamideimide precursor, polyamideimide, and polyethersulfone, fine particles (b), and a solvent (s).

[0028] [Resin component (a)] As described above, the composition for producing a porous membrane contains at least one resin component (a) selected from the group consisting of polyamic acid, polyimide, polyamideimide precursor, polyamideimide, and polyethersulfone. These resin components (a) will be described below.

[0029] [Polyamic Acid] The polyamic acid may be any product obtained by polymerizing any tetracarboxylic dianhydride and diamine. The amounts of the tetracarboxylic dianhydride and diamine used are not particularly limited. The amount of diamine used per mole of tetracarboxylic dianhydride is preferably 0.50 moles or more and 1.50 moles or less, more preferably 0.60 moles or more and 1.30 moles or less, and particularly preferably 0.70 moles or more and 1.20 moles or less.

[0030] The tetracarboxylic dianhydride can be appropriately selected from tetracarboxylic dianhydrides that have conventionally been used as raw materials for synthesizing polyamic acids. The tetracarboxylic dianhydride may be an aromatic tetracarboxylic dianhydride or an aliphatic tetracarboxylic dianhydride. From the viewpoint of the heat resistance of the resulting polyimide resin, it is preferable to use an aromatic tetracarboxylic dianhydride as the tetracarboxylic dianhydride. One type of tetracarboxylic dianhydride may be used alone, or two or more types may be used in combination.

[0031] Specific examples of suitable aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, and 2,2,6,6-biphenyltetracarboxylic dianhydride. Carboxylic acid dianhydrides, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 3,3',4,4'-benzophenone tetraanhydride Carboxylic acid dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 2,2',3,3'-benzophenonetetracarboxylic acid dianhydride, 4,4-(p-phenylenedioxy)diphthalic dianhydride, 4,4-(m-phenylenedioxy)diphthalic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid Examples of the aliphatic tetracarboxylic dianhydride include 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 9,9-bisphthalic anhydride fluorene, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, etc. Examples of the aliphatic tetracarboxylic dianhydride include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, cyclohexane tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, and 1,2,3,4-cyclohexane tetracarboxylic dianhydride.Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride are preferred in terms of price, availability, etc. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

[0032] The diamine can be appropriately selected from diamines conventionally used as raw materials for synthesizing polyamic acid. The diamine may be an aromatic diamine or an aliphatic diamine. From the viewpoint of the heat resistance of the resulting polyimide resin, aromatic diamines are preferred. These diamines may be used alone or in combination of two or more.

[0033] Examples of aromatic diamines include diamino compounds having one phenyl group bonded thereto or from 2 to 10. Specific examples include phenylenediamine and its derivatives, diaminobiphenyl compounds and their derivatives, diaminodiphenyl compounds and their derivatives, diaminotriphenyl compounds and their derivatives, diaminonaphthalene and its derivatives, aminophenylaminoindan and its derivatives, diaminotetraphenyl compounds and their derivatives, diaminohexaphenyl compounds and their derivatives, and cardo-type fluorenediamine derivatives.

[0034] Phenylenediamines include m-phenylenediamine, p-phenylenediamine, etc. Phenylenediamine derivatives include diamines to which alkyl groups such as methyl groups and ethyl groups are bonded, such as 2,4-diaminotoluene and 2,4-triphenylenediamine.

[0035] In diaminobiphenyl compounds, two aminophenyl groups are bonded to each other, such as 4,4'-diaminobiphenyl and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl.

[0036] A diaminodiphenyl compound is a compound in which two aminophenyl groups are bonded together via another group. The bond may be an ether bond, a sulfonyl bond, a thioether bond, a bond via an alkylene or its derivative group, an imino bond, an azo bond, a phosphine oxide bond, an amide bond, or a ureylene bond. The number of carbon atoms in the alkylene bond is approximately 1 to 6. A derivative group of an alkylene group is an alkylene group substituted with one or more halogen atoms, etc.

[0037] Examples of the diaminodiphenyl compound include 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ketone, 3,4'-diaminodiphenyl ketone, 2,2-bis(p-aminophenyl)propane, 2,2'-bis(p-aminophenyl)hexafluoropropane, 4-methyl-2,4-bis(p-aminophenyl)-1-pentene, 4-methyl-2,4-bis(p-aminophenyl)

[0033] Examples of the bis(4-aminophenoxy)phenyl compound include 1,4-bis(4-aminophenoxy)phenyl, 2,4-bis(4-aminophenoxy)phenyl, 4-methyl-2,4-bis(p-aminophenyl)pentane, bis(p-aminophenyl)phosphine oxide, 4,4'-diaminoazobenzene, 4,4'-diaminodiphenylurea, 4,4'-diaminodiphenylamide, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane.

[0038] Among these, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, and 4,4'-diaminodiphenyl ether are preferred in terms of cost, availability, and the like.

[0039] A diaminotriphenyl compound is a compound in which two aminophenyl groups and one phenylene group are bonded via other groups. The other groups are selected from the same groups as those in the diaminodiphenyl compound. Examples of diaminotriphenyl compounds include 1,3-bis(m-aminophenoxy)benzene, 1,3-bis(p-aminophenoxy)benzene, and 1,4-bis(p-aminophenoxy)benzene.

[0040] Examples of diaminonaphthalenes include 1,5-diaminonaphthalene and 2,6-diaminonaphthalene.

[0041] Examples of aminophenylaminoindan include 5 or 6-amino-1-(p-aminophenyl)-1,3,3-trimethylindan.

[0042] Examples of the diaminotetraphenyl compound include 4,4'-bis(p-aminophenoxy)biphenyl, 2,2'-bis[p-(p'-aminophenoxy)phenyl]propane, 2,2'-bis[p-(p'-aminophenoxy)biphenyl]propane, and 2,2'-bis[p-(m-aminophenoxy)phenyl]benzophenone.

[0043] Examples of the cardo-type fluorenediamine derivatives include 9,9-bisanilinefluorene.

[0044] The number of carbon atoms of the aliphatic diamine is preferably, for example, from about 2 to about 15. Specific examples of the aliphatic diamine include pentamethylenediamine, hexamethylenediamine, and heptamethylenediamine.

[0045] The diamine may be a compound in which the hydrogen atom of the diamine is substituted with at least one substituent selected from the group consisting of halogen atoms, methyl groups, methoxy groups, cyano groups, phenyl groups, and the like.

[0046] There are no particular limitations on the means for producing the polyamic acid, and any known method can be used, such as reacting an acid and a diamine component in a solvent.

[0047] The reaction between the tetracarboxylic dianhydride and the diamine is usually carried out in a solvent. The solvent used for the reaction between the tetracarboxylic dianhydride and the diamine is not particularly limited as long as it can dissolve the tetracarboxylic dianhydride and the diamine and does not react with the tetracarboxylic dianhydride and the diamine. One solvent may be used alone, or two or more solvents may be used in combination.

[0048] Examples of solvents used in the reaction of tetracarboxylic dianhydride with diamine include nitrogen-containing polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, N-methylcaprolactam, and N,N,N',N'-tetramethylurea; lactone-based polar solvents such as β-propiolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, and ε-caprolactone; dimethyl sulfoxide; acetonitrile; fatty acid esters such as ethyl lactate and butyl lactate; ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dioxane, tetrahydrofuran, methyl cellosolve acetate, and ethyl cellosolve acetate; and phenolic solvents such as cresols and xylene-based mixed solvents. These solvents may be used alone or in combination of two or more. There is no particular limitation on the amount of solvent used, but the amount of solvent used is preferably an amount that results in a polyamic acid content of 5 to 50% by mass.

[0049] Among these solvents, nitrogen-containing polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, N-methylcaprolactam, and N,N,N',N'-tetramethylurea are preferred in terms of the solubility of the polyamic acid produced.

[0050] The polymerization temperature is generally from -10°C to 120°C, preferably from 5°C to 30°C. The polymerization time varies depending on the raw material composition used, but is usually from 3 hours to 24 hours. One type of polyamic acid may be used alone, or two or more types may be used in combination.

[0051] [Polyimide] The structure and molecular weight of the polyimide are not limited, and known polyimides can be used. The polyimide may have a condensable functional group such as a carboxyl group or a functional group that promotes a crosslinking reaction during baking in its side chain. In addition, a soluble polyimide that can be dissolved in the solvent (S) contained in the varnish is preferred.

[0052] In order to make the polyimide soluble in the solvent (s), it is effective to use a monomer for introducing a flexible, bent structure into the main chain, for example, aliphatic diamines such as ethylenediamine, hexamethylenediamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, and 4,4'-diaminodicyclohexylmethane; aromatic diamines such as 2-methyl-1,4-phenylenediamine, o-tolidine, m-tolidine, 3,3'-dimethoxybenzidine, and 4,4'-diaminobenzanilide; polyoxyalkylene diamines such as polyoxyethylene diamine, polyoxypropylene diamine, and polyoxybutylene diamine; polysiloxane diamine; 2,3,3',4'-oxydiphthalic anhydride, 3,4,3',4'-oxydiphthalic anhydride, and 2,2-bis(4-hydroxyphenyl)propanedibenzoate-3,3',4,4'-tetracarboxylic dianhydride. It is also effective to use a monomer having a functional group that improves solubility in a solvent, for example, a fluorinated diamine such as 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl or 2-trifluoromethyl-1,4-phenylenediamine. Furthermore, in addition to the monomer for improving the solubility of the polyimide, the same monomer as the monomer described in the polyamic acid section above can also be used in combination, as long as the solubility is not impaired. Each of the polyimide and its monomer may be used alone or in combination of two or more.

[0053] There are no particular limitations on the means for producing the polyimide. Known methods, such as chemical imidization or thermal imidization of polyamic acid, can be used to produce the polyimide. Examples of such polyimides include aliphatic polyimides (fully aliphatic polyimides) and aromatic polyimides, with aromatic polyimides being preferred. Examples of aromatic polyimides include those obtained by thermally or chemically ring-closing polyamic acids having repeating units represented by formula (1), or polyimides having repeating units represented by formula (2). In the formula, Ar represents an aryl group. These polyimides are then preferably dissolved in the solvent (S) to be used.

[0054] [Polyamideimide and polyamideimide precursor] The polyamideimide is not limited in structure or molecular weight, and known polyamideimides can be used. The polyamideimide may have a condensable functional group such as a carboxyl group or a functional group that promotes a crosslinking reaction during baking in the side chain. In addition, a soluble polyamideimide that can be dissolved in the solvent (S) contained in the varnish is preferred.

[0055] Polyamideimides that can be used are generally, without particular limitation, (i) resins obtained by reacting an acid having a carboxyl group and an acid anhydride group in one molecule, such as trimellitic anhydride, with a diisocyanate, or (ii) resins obtained by imidizing a precursor polymer (polyamideimide precursor) obtained by reacting a reactive derivative of the above acid, such as trimellitic anhydride chloride, with a diamine.

[0056] Examples of the above acid or its reactive derivative include trimellitic anhydride, trimellitic anhydride halides such as trimellitic anhydride chloride, and trimellitic anhydride esters.

[0057] Examples of the optional diamine include the diamines exemplified in the description of polyamic acid above. Diaminopyridine compounds can also be used.

[0058] The optional diisocyanate is not particularly limited, and examples thereof include diisocyanate compounds corresponding to the optional diamines. Specific examples of the diisocyanate include metaphenylene diisocyanate, p-phenylene diisocyanate, o-tolidine diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, 4,4'-oxybis(phenylisocyanate), 4,4'-diisocyanatodiphenylmethane, bis[4-(4-isocyanatophenoxy)phenyl]sulfone, 2,2'-bis[4-(4-isocyanatophenoxy)phenyl]propane, 2,4- Examples of the isocyanate include tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethyldiphenyl-4,4'-diisocyanate, 3,3'-diethyldiphenyl-4,4'-diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, m-xylene diisocyanate, p-xylene diisocyanate, and naphthalene diisocyanate.

[0059] In addition to the above, compounds described as general formulas in JP-A-63-283705 and JP-A-2-198619 can also be used as raw material monomers for polyamideimides. Furthermore, the imidization in the above method (ii) can be either thermal imidization or chemical imidization. Chemical imidization can be achieved by immersing a composite film (unbaked composite film) formed using a varnish containing a polyamideimide precursor or the like in acetic anhydride or a mixed solvent of acetic anhydride and isoquinoline. The polyamideimide precursor can also be referred to as a polyimide precursor from the perspective of a precursor before imidization.

[0060] The polyamideimide contained in the varnish may be, for example, (1) a polymer obtained by reacting an acid such as trimellitic anhydride with a diisocyanate, or (2) a polymer obtained by imidizing a precursor polymer obtained by reacting a reactive derivative of the acid such as trimellitic anhydride chloride with a diamine. In this specification and claims, "polyamideimide precursor" refers to a polymer (precursor polymer) before imidization. Each of the polyamideimide and polyamideimide precursor may be used alone or in combination of two or more. Furthermore, for polyamideimide, each of the polymers, raw material monomers, and oligomers may be used alone or in combination of two or more.

[0061] [Polyethersulfone] The polyethersulfone is not particularly limited as long as it is soluble in the solvent (s) used in the varnish. The polyethersulfone can be appropriately selected depending on the application of the porous membrane to be produced, and may be hydrophilic or hydrophobic. It may also be an aliphatic polyethersulfone or an aromatic polyethersulfone. The mass average molecular weight is, for example, preferably 5,000 to 1,000,000, and more preferably 10,000 to 300,000.

[0062] [Fine particles (b)] The average particle size of the fine particles (b) is appropriately selected depending on the average pore size of the porous film to be finally formed. The average particle size of the fine particles (b) can be selected, for example, in the range of 9 nm to 150 nm. The average pore size of the porous film measured by a porometer is 9 nm to 40 nm. The average particle size is the volume average particle size measured by a laser diffraction particle size distribution analyzer.

[0063] The material of the fine particles (b) is not particularly limited, and any known material can be used as long as it is insoluble in the solvent (s) contained in the varnish and can be removed from the composite film (resin-particle composite film) formed using the varnish in the fine particle removal step, and either an inorganic material or an organic material can be used.

[0064] Examples of inorganic material fine particles (b) include inorganic oxide fine particles, and specific examples thereof include silica (silicon dioxide) fine particles, titanium oxide fine particles, and alumina (Al ２ O ３ Examples of silica include colloidal silica. Among them, monodispersed spherical silica particles are preferred because they can form uniform pores.

[0065] Examples of fine particles of organic materials include fine particles of organic polymers such as high molecular weight olefins (polypropylene, polyethylene, etc.), polystyrene, epoxy resins, cellulose, polyvinyl alcohol, polyvinyl butyral, polyesters, and polyethers.

[0066] Furthermore, it is preferable that the fine particles (b) have a high sphericity and a small particle size distribution index. Fine particles satisfying these conditions (b) have excellent dispersibility in the varnish and can be used in a state where they do not aggregate with each other.

[0067] The fine particles (b) may be used alone or in combination of two or more kinds. The porous membrane can be produced using two or more kinds of fine particles (b). When fine particles (b2) having a large average particle size are used, a porous membrane having an average pore size within the above range can be produced by combining fine particles (b1) having a small average particle size with fine particles (b2) having a large average particle size.

[0068] The fine particles (b1) have an average particle size of less than 100 nm.

[0069] When the varnish contains, as the fine particles (b), fine particles (b1) and fine particles (b2) having an average particle size larger than the fine particles (b1), and the average particle size of the fine particles (b1) is less than 100 nm, the pore size of the produced porous membrane can be reduced and the flow rate can be improved, as shown in the examples described below. This is believed to be due to the following reason. The pores (spherical pores) of the porous membrane are formed by removing individual fine particles present in a composite membrane (resin-particle composite membrane) formed using the varnish in a subsequent particle removal step. The porous membrane has a structure in which the spherical pores are interconnected (communicating pores). The communicating pores are formed by removing multiple fine particles (b) that are present in contact with each other in a composite membrane (resin-particle composite membrane) formed using the varnish in a subsequent particle removal step in the porous membrane manufacturing method. The points at which the spherical pores communicate with each other in the communicating pores originate from the points (contact points) where multiple fine particles (b) come into contact with each other before removal. The pore size of the communicating pores is measured using the porometer described above. When small particles (b1) with an average particle size of less than 100 nm and particles (b2) with an average particle size larger than the particles (b1) are used as the two types of particles (b) with different sizes, the pore size of the communicating holes formed at the points where the particles contact each other (contact points) depends on the particle size of the small particles (particles (b1)), and the pore size is equivalent to the pore size of the communicating holes formed at the contact points between the small particles (particles (b1)). On the other hand, when two types of particles with different sizes (particles (b1) and particles (b2)) are used, the number of holes formed is reduced compared to when only small particles (particles (b1)) are used. This reduces the resistance when a fluid flows through the porous membrane, and increases the flow rate of the fluid when filtering the fluid using the porous membrane. Therefore, by using small particles (b1) with an average particle size of less than 100 nm and particles (b2) larger than the particles (b1) as the particles (b), a porous membrane is formed with small pores and a high flow rate of the fluid when filtering the fluid.

[0070] The average particle size of the fine particles (b1) is less than 100 nm. The average particle size of the fine particles (b1) may be, for example, 90 nm or less, 60 nm or less, or 30 nm or less. The average particle size of the fine particles (b1) may be, for example, 10 nm or more.

[0071] The average particle size of the fine particles (b2) is larger than that of the fine particles (b1). The average particle size of the fine particles (b2) may be less than 100 nm. The average particle size of the fine particles (b2) may be, for example, 40 nm or more, 70 nm or more, 90 nm or more, or 100 nm or more. The average particle size of the fine particles (b1) may be, for example, 150 nm or less, or 100 nm or less.

[0072] The difference between the average particle size of the fine particles (b1) and the average particle size of the fine particles (b2) is not particularly limited and may be, for example, 5 nm to 140 nm, 10 nm to 100 nm, or 20 nm to 60 nm.

[0073] Specific examples include the following combinations of 1) to 5): 1) Average particle size of fine particles (b1): 70 nm or more and 90 nm or less Average particle size of fine particles (b2): 100 nm or more and 150 nm or less 2) Average particle size of fine particles (b1): 70 nm or more and 90 nm or less Average particle size of fine particles (b2): 90 nm or more and 110 nm or less 3) Average particle size of fine particles (b1): 40 nm or more and 60 nm or less Average particle size of fine particles (b2): 70 nm or more and 90 nm or less 4) Average particle size of fine particles (b1): 10 nm or more and 30 nm or less Average particle size of fine particles (b2): 70 nm or more and 90 nm or less 5) Average particle size of fine particles (b1): 10 nm or more and 30 nm or less Average particle size of fine particles (b2): 40 nm or more and 60 nm or less

[0074] In this specification, the average particle size of the fine particles (b) is D50, which means the particle size at an integrated value of 50% in the volume-based particle size distribution determined by a laser diffraction / scattering method.

[0075] The ratio (d2 / d1) of the average particle size (d2) of the fine particles (b2) to the average particle size (d1) of the fine particles (b1) is preferably 1.2 to 6.0.

[0076] The ratio (m1:m2) of the mass (m1) of the fine particles (b1) to the mass (m2) of the fine particles (b2) is preferably 100:1 to 1:5, more preferably 100:1 to 1:3, and even more preferably 100:1 to 2:3.

[0077] [Solvent (s)] The solvent (s) is not particularly limited as long as it can dissolve the resin component (A) comprised of polyamic acid, polyimide, polyamideimide precursor, polyamideimide, and / or polyethersulfone contained in the varnish, and does not dissolve the fine particles (b). Examples of the solvent (S) include the solvents exemplified as solvents used in the reaction between tetracarboxylic dianhydride and diamine. The solvent (s) may be used alone or in combination of two or more. When the resin component (A) is polyethersulfone, examples of the solvent (S) include polar solvents such as diphenyl sulfone, dimethyl sulfone, dimethyl sulfoxide, benzophenone, tetrahydrothiophene-1,1-dioxide, and 1,3-dimethyl-2-imidazolidinone, in addition to the nitrogen-containing polar solvents described above.

[0078] [Dispersant] A dispersant may be added together with the fine particles (b) for the purpose of uniformly dispersing the fine particles (b) in the varnish. By adding a dispersant, the fine particles (b) can be mixed more uniformly in the varnish, and furthermore, the fine particles (b) can be uniformly distributed in the film formed from the varnish. As a result, dense openings can be formed on the surface of the finally obtained porous film, and the front and back surfaces can be efficiently connected, thereby improving the air permeability of the porous film. Furthermore, the addition of a dispersant tends to improve the drying properties of the varnish and also tends to improve the peelability of the formed unfired composite film from the substrate, etc.

[0079] The dispersant is not particularly limited, and known dispersants can be used. Examples of dispersants include anionic surfactants such as coconut fatty acid salts, castor sulfated oil salts, lauryl sulfate salts, polyoxyalkylene allyl phenyl ether sulfate salts, alkyl benzene sulfonic acids, alkyl benzene sulfonates, alkyl diphenyl ether disulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinate salts, isopropyl phosphate, polyoxyethylene alkyl ether phosphate salts, and polyoxyethylene allyl phenyl ether phosphate salts; cationic surfactants such as oleylamine acetate, lauryl pyridinium chloride, cetyl pyridinium chloride, lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, behenyl trimethyl ammonium chloride, and didecyl dimethyl ammonium chloride; amphoteric surfactants such as coconut alkyl dimethyl amine oxide, fatty acid amidopropyl dimethyl amine oxide, alkyl polyaminoethyl glycine hydrochloride, amido betaine surfactants, alanine surfactants, and lauryliminodipropionic acid; Nonionic surfactants of polyoxyalkylene primary alkyl ethers or polyoxyalkylene secondary alkyl ethers, such as polyoxyethylene octyl ether, polyoxyethylene decyl ether, polyoxyethylene lauryl ether, polyoxyethylene laurylamine, polyoxyethylene oleylamine, polyoxyethylene polystyrylphenyl ether, and polyoxyalkylene polystyrylphenyl ether; other polyoxyalkylene-based nonionic surfactants, such as polyoxyethylene dilaurate, polyoxyethylene laurate, polyoxyethylenated castor oil, polyoxyethylenated hydrogenated castor oil, sorbitan laurate, polyoxyethylene sorbitan laurate, and fatty acid diethanolamides; fatty acid alkyl esters, such as octyl stearate and trimethylolpropane tridecanoate; and polyether polyols, such as polyoxyalkylene butyl ether, polyoxyalkylene oleyl ether, and trimethylolpropane tris(polyoxyalkylene) ether, but are not limited to these.The above dispersants may also be used in combination of two or more.

[0080] The content of the dispersant in the varnish is, for example, preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.05% by mass or more and 1% by mass or less, and even more preferably 0.1% by mass or more and 0.5% by mass or less, relative to the mass of the microparticles (b), from the viewpoint of film-forming properties.

[0081] The method for producing the porous membrane-producing composition (varnish) is not particularly limited. The varnish is typically produced by a step of preparing a fine particle dispersion by dispersing fine particles (b) in a solvent, a step of preparing a resin solution containing the resin component (A), and a step of kneading the fine particle dispersion and the resin solution together to adjust the concentration.

[0082] The viscosity of the varnish at 25°C is preferably 0.1 Pa·s or more and 3 Pa·s or less. The solid content concentration is preferably 10 mass % or more and 50 mass % or less. The varnish is produced by kneading for preferably 2 minutes to 10 hours, more preferably 2 minutes to 60 minutes. The viscosity of the varnish is measured using an E-type viscometer. A rotary / revolution mixer (product name: Awatori Rentaro, manufactured by Thinky Corporation), a planetary mixer, a bead mill, etc. can be used to knead the varnish. In addition, in the kneading process, a mixture of 1960 μm2 of a cross-sectional area is used. ２ 785,000 μm or more ２ A dispersion process may be performed by using a dispersion device having the following flow path, and passing a mixed liquid (slurry) containing a microparticle dispersion and a resin solution pressurized to 50 MPa or more through the flow path. An example of a method for performing a dispersion process by passing the mixed liquid through such a flow path is the method described in JP 2020-104105 A.

[0083] <<Method for Producing Porous Film>> The method for producing a porous film includes a composite film formation step of forming a composite film made of the above-mentioned porous film-producing composition on a substrate, and a particle removal step of removing particles from the composite film. The method for producing a porous film may also include a baking step of baking the composite film, after the composite film formation step and before the particle removal step, in which the resin component (a) includes at least one of a polyamic acid and a polyamide-imide precursor.

[0084] [Composite Film Formation Step (Production of Unbaked Composite Film)] In the composite film formation step, a composite film made of the porous film-producing composition (varnish) described above is formed on a substrate. The composite film (hereinafter also referred to as "unbaked composite film") may be formed directly on the substrate. The composite film made of the varnish described above (unbaked composite film) is preferably formed as a single layer film on the substrate. The unbaked composite film can be formed, for example, by applying the varnish to the substrate and then performing a drying step in which the varnish is dried at a temperature of 0°C to 100°C under normal pressure or in a vacuum, preferably at a temperature of 10°C to 100°C under normal pressure. Examples of the substrate include a PET film, a SUS substrate, and a glass substrate.

[0085] The unsintered composite film is then subjected to a baking step in which the unsintered composite film is baked to obtain a polyimide-particle composite film. The unsintered composite film may be baked as is, or may be peeled off from the substrate before the baking step.

[0086] When peeling the composite film (unfired composite film) from the substrate, a substrate pre-formed with a release layer can be used to further enhance the film's releasability. When a release layer is pre-formed on the substrate, a release agent is applied to the substrate and dried or baked before applying the varnish. The release agent used here can be any known release agent, such as an alkyl ammonium phosphate salt, a fluorine-based agent, or a silicone-based agent, without any particular restrictions. When peeling the dried unfired composite film from the substrate, a small amount of release agent remains on the peeled surface of the unfired composite film, which can cause discoloration during firing and adversely affect the electrical properties, so it is preferable to remove it as much as possible. To remove the release agent, a cleaning step can be introduced in which the unfired composite film peeled from the substrate is washed with an organic solvent.

[0087] On the other hand, when the substrate is used as is without providing a release layer for forming the green composite film, the above-mentioned release layer forming step and the above-mentioned cleaning step can be omitted. Furthermore, in the production of the green composite film, the following optional steps may be provided before the firing step described below: a step of immersing in a solvent containing water, a pressing step, and a drying step after the immersion step.

[0088] [Baking Step (Production of Resin-Particle Composite Film)] The baking step is a step of baking the composite film after the composite film formation step and before the particle removal step. When the resin component (A) contained in the varnish is a polyamic acid or a polyamideimide precursor, the composite film (unbaked composite film) is subjected to a post-treatment (baking step) by heating to form a composite film (resin-particle composite film) consisting of a resin made of polyimide and / or polyamideimide and particles (b). When the resin component (a) contained in the varnish is polyimide, polyamideimide, or polyethersulfone, the baking step may be included, but may be omitted.

[0089] The baking temperature in the baking step is preferably 120° C. or higher and 450° C. or lower, more preferably 150° C. or higher and 420° C. or lower. When an organic material is used for the fine particles (b), the baking temperature must be set to a temperature lower than the thermal decomposition temperature of the organic material. When the resin component (a) contained in the varnish is polyamic acid, it is preferable to complete imidization in the baking step.

[0090] The firing conditions may include, for example, a method in which the temperature is raised from room temperature to 400° C. or lower over 3 hours and then maintained at 400° C. for 20 minutes, or a stepwise drying-thermal imidization method in which the temperature is raised from room temperature to 400° C. in steps of 50° C. (each step is maintained for 20 minutes) and finally maintained at 400° C. for 20 minutes. When an unfired composite film is formed on a substrate and then temporarily peeled off from the substrate, a method in which the edges of the unfired composite film are fixed to a stainless steel mold or the like to prevent deformation can be used.

[0091] The thickness of the completed resin-particle composite film can be determined by measuring the thickness at multiple locations with, for example, a micrometer and averaging the measured thickness. The preferred average film thickness varies depending on the application of the porous film, but for example, when used as a filter, the film thickness is preferably 40 μm or more and 90 μm or less, and more preferably 50 μm or more and 80 μm or less.

[0092] [Particle Removal Step (Making Resin-Particle Composite Film Porous)] In the particle removal step, the particles (b) are removed from the composite film after the composite film formation step (or from the composite film (resin-particle composite film) after the baking step, if a baking step has been performed). By selecting an appropriate method to remove the particles (b), a porous film can be produced with good reproducibility.

[0093] When silica is used as the material of the fine particles (b), for example, the resin-fine particle composite film can be treated with low-concentration hydrogen fluoride water or the like to dissolve and remove the silica.

[0094] An organic material can also be selected as the material for the fine particles (b). There are no particular limitations on the organic material, as long as it decomposes at a lower temperature than the resin contained in the resin-particle composite film. For example, resin fine particles made of a linear polymer or a known depolymerizable polymer can be used. In a normal linear polymer, the molecular chain of the polymer is randomly cut upon thermal decomposition, while in a depolymerizable polymer, the polymer is decomposed into monomers upon thermal decomposition. In either case, the polymer is a low molecular weight substance or a CO ２ By decomposing the resin particles to a temperature of 200°C or higher and 320°C or lower, the resin particles disappear from within the porous film. The decomposition temperature of the resin particles used is preferably 200°C or higher and 320°C or lower, and more preferably 230°C or higher and 260°C or lower. If the decomposition temperature is 200°C or higher, film formation can be performed even when a high-boiling point solvent is used in the varnish, and the range of selection of baking conditions for the resin-particle composite film becomes wider. Furthermore, if the decomposition temperature is lower than 320°C, only the resin particles can be eliminated without thermally damaging the resin contained in the resin-particle composite film.

[0095] The total thickness of the porous membrane is not particularly limited. For example, when used in a filter or the like, the total thickness of the porous membrane is preferably 40 μm or more and 90 μm or less, and more preferably 50 μm or more and 80 μm or less. The above-mentioned thickness can be determined by measuring the thickness at multiple locations with, for example, a micrometer or the like and averaging the thicknesses, in the same way as when measuring the resin-particle composite membrane.

[0096] [Resin Removal Step] The method for producing a porous membrane may include a resin removal step of removing at least a portion of the resin portion of the resin-particle composite membrane before the particle removal step, or removing at least a portion of the porous membrane after the particle removal step. By removing at least a portion of the resin portion of the resin-particle composite membrane or at least a portion of the porous membrane, it is possible to improve the pore size of the porous membrane in the final product compared to when no removal is performed.

[0097] The step of removing at least a portion of the resin portion or the step of removing at least a portion of the porous film can be carried out by a common chemical etching method, a physical removal method, or a combination of these.

[0098] Examples of chemical etching methods include treatment with a chemical etching solution such as an inorganic alkaline solution or an organic alkaline solution. Inorganic alkaline solutions are preferred. Examples of inorganic alkaline solutions include hydrazine solutions containing hydrazine hydrate and ethylenediamine; solutions of alkali metal hydroxides such as potassium hydroxide, sodium hydroxide, sodium carbonate, sodium silicate, and sodium metasilicate; ammonia solutions; and etching solutions containing an alkali hydroxide, hydrazine, and 1,3-dimethyl-2-imidazolidinone as main components. Examples of organic alkaline solutions include alkaline solutions of primary amines such as ethylamine and n-propylamine; secondary amines such as diethylamine and di-n-butylamine; tertiary amines such as triethylamine and methyldiethylamine; alcohol amines such as dimethylethanolamine and triethanolamine; quaternary ammonium salts such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; and cyclic amines such as pyrrole and piheridine.

[0099] The solvent for each of the above solutions can be selected appropriately from pure water or alcohols. It is also possible to use a solution containing an appropriate amount of surfactant. The alkali concentration is, for example, 0.01 to 20% by mass.

[0100] As a physical method, for example, dry etching using plasma (oxygen, argon, etc.), corona discharge, etc., or a surface treatment method in which an abrasive (e.g., alumina (hardness 9), etc.) is dispersed in a liquid and irradiated onto the surface of the film at a speed of 30 to 100 m / s can be used.

[0101] The above-mentioned method is preferable because it can be applied to the resin removal step either before or after the fine particle removal step.

[0102] On the other hand, as a physical method applicable only to the resin removal process performed after the particle removal process, a method can be adopted in which the target surface is pressed against a mount film (e.g., a polyester film such as a PET film) wetted with a liquid, and then the porous membrane is peeled off from the mount film either without drying or after drying. Due to the surface tension or electrostatic adhesion of the liquid, the porous membrane is peeled off from the mount film with only the surface layer of the porous membrane remaining on the mount film.

[0103] <Filtration Treatment Method> A liquid is filtered using the porous membrane described above. The purpose of the filtration is not particularly limited. Examples of the purpose of filtration include separating solids contained in the liquid and purifying the liquid by removing solids contained in the fluid.

[0104] The liquid to be filtered is not particularly limited. Preferred liquids include various chemicals used in semiconductor device manufacturing. Specific examples of chemicals include organic solvents and liquid resist compositions. Liquid resist compositions include various resist compositions used in the manufacture of electronic components such as displays and semiconductor elements to form protective films, insulating films, etching masks, light-shielding films, colored films, high-refractive-index films, low-refractive-index films, plating molds, and the like. The resist composition may be a photosensitive composition or a non-photosensitive composition, and is preferably a photosensitive composition. Resist compositions typically contain components such as various resins; polymerizable monomers or crosslinkers such as (meth)acrylate compounds, epoxy compounds, vinyl ether compounds, and methylol compounds; radical polymerization initiators; photoacid generators; quenchers; sensitizers; and surfactants.

[0105] When performing filtration, the porous membrane can be attached to various filter devices. In this case, the porous membrane may be processed into various shapes. For example, the porous membrane may be folded to increase the surface area. The porous membrane may also be processed into a cylindrical or bag shape.

[0106] The filtration of the fluid is carried out appropriately by a method depending on the type of filter device in which the porous membrane is mounted.

[0107] Specific Methods for Purifying Liquids A method for purifying a liquid involves causing a portion or all of the liquid to permeate from one side of the porous membrane described above to the other side by means of a pressure difference.

[0108] In the method for purifying a liquid, a part or all of the liquid can be permeated from one side of the porous membrane to the other side by filtering the part or all of the liquid using the porous membrane as a separating or adsorbing material. The porous membrane used as a separating or adsorbing material may be incorporated into a filter device described below.

[0109] The porous membrane may be used in a liquid purification method in a flat shape or a pipe shape with opposing sides of the porous membrane joined together. A pipe-shaped porous membrane is preferably pleated to increase the contact area with the feed liquid. The porous membrane is appropriately sealed to prevent the feed liquid and the filtrate from mixing, as described below.

[0110] The purification of liquid can be carried out by using the above-mentioned porous membrane without differential pressure, that is, by natural filtration by gravity, but it is preferable to carry out by differential pressure.The differential pressure is not particularly limited as long as it is a pressure difference between one side and the other side of the porous membrane.The differential pressure usually includes pressurization (positive pressure) that applies pressure to one side (feed liquid side) of the porous membrane, and decompression (negative pressure) that applies negative pressure to one side (filtrate side) of the porous membrane, and the like, and pressurization is preferable.

[0111] Pressurization involves applying pressure to the side of the porous membrane (the supply liquid side) where the liquid (sometimes referred to herein as the "supply liquid") is present before being passed through the porous membrane. For example, pressure is preferably applied by utilizing the pressure generated by the circulation or delivery of the supply liquid or by utilizing positive gas pressure. Pressurization can be performed using an active pressurizing device such as a pump (a liquid delivery pump, a circulation pump, etc.). Specifically, a rotary pump, a diaphragm pump, a metering pump, a chemical pump, a plunger pump, a bellows pump, a gear pump, a vacuum pump, an air pump, a liquid pump, etc. can be used. When pressurizing with gas, the gas used for pressurization is preferably a gas that is inert or non-reactive with the supply liquid, specifically, nitrogen or a rare gas such as helium or argon. Pressurization is preferred in the manufacturing field of electronic materials, particularly semiconductors. In this case, the side where the liquid that has permeated the porous membrane is collected can be atmospheric pressure without reducing the pressure, and positive gas pressure is preferred. The above pressurization method may also be performed via a pressure valve, a pressure valve, a three-way valve, or other valve. The pressure is reduced on the side (filtrate side) where the liquid that has permeated the porous polyimide resin membrane is collected. The pressure may be reduced, for example, by a pump, but it is preferable to reduce the pressure to a vacuum. When circulating or transporting the supply liquid by a pump, the pump is usually placed between the supply liquid tank (or circulation tank) and the porous membrane.

[0112] The pressurization may utilize both pressurization of the liquid by a device such as a pump and pressurization by gas. Furthermore, the differential pressure may be a combination of pressurization and decompression. Combinations of pressurization and decompression may, for example, utilize both pressurization of the liquid by a device such as a pump and decompression, both pressurization by gas and decompression, or pressurization of the liquid by a device such as a pump, and pressurization by gas and decompression. When combining methods for creating a differential pressure, a combination of pressurization of the liquid by a device such as a pump and positive gas pressure, or a combination of pressurization of the liquid by a device such as a pump and decompression, is preferred in terms of simplifying production, etc. In the present invention, since a porous membrane is used, even if only one method, such as positive gas pressure, is used as a method for creating a differential pressure, purification with excellent impurity removal performance can be achieved.

[0113] The pressure difference applied before and after the porous membrane by providing a pressure difference can be appropriately set according to the membrane thickness, porosity or average pore size of the porous membrane used, or the desired degree of purification, flow rate, flow velocity, or the concentration or viscosity of the feed solution.For example, in the case of a so-called cross-flow method (where the feed solution flows parallel to the porous membrane), the pressure difference is, for example, 3 MPa or less, and in the case of a so-called dead-end method (where the feed solution flows crosswise to the porous membrane), the pressure difference is, for example, 1 MPa or less.The lower limit is not particularly limited, and is, for example, 10 Pa.

[0114] In the method for purifying a liquid, when part or all of the liquid is permeated from one side to the other side of a porous membrane, if the liquid contains a solute, the feed liquid may be appropriately diluted with a diluent.

[0115] In the method for purifying a liquid, before passing the feed liquid through the porous membrane, a solution such as an alcohol (e.g., methanol, ethanol, isopropyl alcohol), a ketone (e.g., acetone, methyl ethyl ketone), water, a solvent contained in the feed liquid, or a mixture thereof may be contacted with the porous membrane and passed through in order to clean the porous membrane, improve its wettability to the feed liquid, or adjust the surface energy between the porous membrane and the feed liquid. When contacting the porous membrane with the solution before passing the feed liquid through the porous membrane, the porous membrane may be impregnated or immersed in the solution. By contacting the porous membrane with the solution, for example, the solution can penetrate into the pores inside the porous membrane. The contact between the solution and the porous membrane before passing the feed liquid through the porous membrane may be carried out by the above-mentioned differential pressure, and may be carried out under pressure, particularly when the solution is to penetrate into the pores inside the porous membrane.

[0116] In the liquid purification method, a porous membrane having the above-mentioned average pore size and surface area is considered to remove some or all of the impurities from the liquid before treatment by separation and / or adsorption. In this specification, "separation" may include at least one selected from the group consisting of filtration, isolation, removal, capture, purification, and sieving. The liquid purification method of the present invention can also be suitably used for processes that involve both separation and adsorption, such as a process of separating microsubstances from a liquid that contained the microsubstances by adsorbing the microsubstances into the pores and / or communicating pores of a porous membrane.

[0117] In the method for purifying a liquid, the porous membrane can be used, for example, as a filter medium or other filter material, specifically, it can be used alone, or it can be used as a filter material to which other functional layers (membranes) are added, or it can be used as a membrane to be combined with other filter materials, for example, it can be used as a membrane to be used in a filter device, etc. The functional layer that can be used in combination with the porous membrane of the present invention is not particularly limited, and examples thereof include nylon membranes, polytetrafluoroethylene (PTFE) membranes, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) membranes, or membranes modified from these, which have chemical or physicochemical functions.

[0118] In the liquid purification method of the present invention, the porous membrane can be used as a filter medium, such as an impurity removal filter used in the semiconductor manufacturing field, and can also be used as a laminate containing the filter medium and other filter materials, or as a filter device.The filter device is not particularly limited, but in the filter device, the porous membrane is arranged so that the feed liquid and the filtrate intersect.In relation to the liquid flow path, it may be arranged parallel to the flow path or so as to intersect.The regions before and after passing through the porous membrane are appropriately sealed so that the feed liquid is separated from the filtrate.For example, as a sealing method, the porous membrane may be processed, as necessary, by light (UV) curing adhesion or heat adhesion (including anchor effect adhesion (thermal welding, etc.)), or adhesion using an adhesive, or the porous membrane of the present invention and other filter materials (filters) can be bonded, for example, by an integration method, and these porous membranes can be further used with an outer container made of a thermoplastic resin such as polyethylene, polypropylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyethersulfone (PES), polyimide, polyamideimide, etc.

[0119] <<Method for Producing a Resist Film>> The resist composition purified by the above-described liquid purification method contains little or no minute impurities. The purified resist composition is used to produce a resist film by being applied to various substrates or attached to various substrates as a photosensitive dry film. The method for producing the dry film is not particularly limited. The dry film can be produced by various known methods. The resist film may be patterned or unpatterned.

[0120] The method for producing a resist film includes filtering a liquid resist composition using the porous membrane described above to purify the resist composition, applying the purified resist composition to a substrate to form a coating film, and drying the coating film to form a resist film. When the resist composition is a photosensitive composition, the resist film may be patterned by exposing and developing the resist film using a method appropriate for the type of resist composition. The material of the substrate, the coating method, the method for drying the coating film, the development method, etc. are appropriately selected from well-known materials and methods, taking into consideration the type of resist composition and the use of the resist film.

[0121] According to the above method, by using a resist composition from which minute impurities have been effectively removed, a resist film with few defects can be formed.

[0122] As described above, the present inventors provide the following (1) to (6): (1) A porous membrane made of at least one resin component (A) selected from the group consisting of polyimide, polyamideimide, and polyethersulfone, or a resin composition containing the resin component (A), wherein the average pore size is 9 nm or more and 40 nm or less, and the specific surface area of ​​the porous membrane is calculated based on the specific surface area of ​​the porous membrane measured by the BET method. ２ The surface area per ２ More than 3500m ２ (2) The porous film according to (1), which has interconnected pores in which spherical or nearly spherical pores are interconnected. (3) The porous film according to (1) or (2), which has a film thickness of 40 μm or more and 90 μm or less. (4) The porous film according to any one of (1) to (3), which is used in the filtration treatment of a liquid resist composition. (5) A method for purifying a resist composition, which comprises filtering a liquid resist composition using the porous film according to any one of (1) to (4). (6) A method for producing a resist film, which comprises filtering a liquid resist composition using the porous film according to any one of (1) to (4), purifying the resist composition, applying the purified resist composition onto a substrate to form a coating film, and drying the coating film to form a resist film.

[0123] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to the following examples.

[0124] Examples 1 to 4 and Comparative Examples 1 to 5 A silica dispersion was added to a solution of polyamic acid (resin component (a)) so that the ratio of the mass of polyamic acid to the total mass of polyamic acid and silica (fine particles (b)) was 30 mass % and 70 mass %, respectively. The silica dispersion contained 0.5 mass % of dispersant relative to the mass of silica. Furthermore, organic solvent (1) and organic solvent (2) were added to the porous membrane production composition (varnish). The mass ratio of organic solvent (1) to organic solvent (2) was organic solvent (1):organic solvent (2) = 90:10. The resulting mixture was stirred in a 1000 mL container with a stirring blade at 4000 rpm for 30 minutes to disperse the silica in the mixture. Thereafter, a 60 μm diameter (cross-sectional area 2826 μm) dispersion (manufactured by Yoshida Kikai Kogyo Co., Ltd.) was used. ２ ), a dispersion treatment was carried out 10 times by passing the mixed solution through the flow path at 200 MPa to prepare a composition for producing a porous film (varnish) with a solids concentration of 30% by mass. The ratio of polyamic acid to silica (polyamic acid:silica) in the obtained varnish was 38:62 by volume and 30:70 by mass. The following polyamic acid solution, organic solvent, dispersant, and fine particles were used. The type of silica is as shown in Table 1. Polyamic acid solution: reaction product of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether (solids content 20% by mass (organic solvent: N,N-dimethylacetamide)) Organic solvent (1): N,N-dimethylacetamide (DMAc) Organic solvent (2): gamma-butyrolactone Dispersant: polyoxyethylene secondary alkyl ether dispersant

[0125] The obtained porous film-forming composition was applied to a polyethylene terephthalate (PET) film substrate using an applicator, and the resulting coating film was dried at 90°C for 5 minutes to form a composite film on the substrate (composite film formation step).

[0126] This composite film (unbaked composite film) was baked at 380° C. for 15 minutes to complete the imidization, thereby obtaining a resin-particle composite film (baking step).

[0127] The resin-particle composite film was peeled off from the substrate and immersed in an aqueous solution of hydrofluoric acid (HF) for 10 minutes to remove the silica particles contained in the film, thereby obtaining a porous film (particle removal step).

[0128] Thereafter, the porous membrane was washed with water and dried to obtain polyimide porous membranes of Examples 1 to 4 and Comparative Examples 1 to 5, each having a membrane thickness as shown in Table 1. Cracks were observed in the porous membranes of Comparative Examples 3 and 5. The average pore diameters of the polyimide porous membranes of Examples 1 to 4 and Comparative Examples 1 to 5 were measured using a porometer according to the above-mentioned method. Furthermore, based on the specific surface areas of the polyimide porous membranes of Examples 1 to 4 and Comparative Examples 1 to 5 measured by the BET method, the average pore diameter of the porous membrane was calculated. ２ The average pore size and surface area are shown in Table 1.

[0129]

[0130] <Filtration Test> A 47φ disk filter was prepared, equipped as a filter membrane with each of the polyimide porous films of Examples 1 to 4 and Comparative Examples 1 to 5. Using these disk filters, the following resist compositions were filtered at a filtration pressure of 0.15 MPa (G).

[0131] The resist composition used contained 100 parts by mass of the following polymer compound (1), 3.6 parts by mass of the following acid generator (1), 0.4 parts by mass of tri-n-octylamine, and a mixed solvent of propylene glycol monomethyl ether acetate:propylene glycol monomethyl ether = 60:40 (mass ratio). The mass ratio of polymer compound (1) to the mass of the resist composition was approximately 7 mass%.

[0132] High molecular compound (1)

[0133] Acid generator (1)

[0134] <Change in Weight Average Molecular Weight of Resin Included in Resist Composition Due to Filtration> The weight average molecular weight (Mw1) of the resin included in the resist composition before filtration and the weight average molecular weight (Mw2) after filtration were measured by gel permeation chromatography (GPC). The weight average molecular weight is the polystyrene-equivalent weight average molecular weight measured by GPC. The reduction rate of the average molecular weight of the resin was calculated from Mw1 and Mw2 using the following formula: Reduction rate of average molecular weight (%) = (Mw1 - Mw2) / Mw1 × 100

[0135] <Number of defects in resist film> Each of the resist compositions purified using the porous film of Examples 1 to 4 and Comparative Examples 1 to 5 was applied to a 12-inch silicon substrate treated with hexamethyldisilazane (HMDS) using a spinner. The formed coating film was pre-baked on a hot plate at 80°C for 60 seconds to dry the coating film, forming a resist film with a thickness of 40 nm. The number of defects larger than 40 nm in size was measured for the resulting resist film using a surface defect observation device (KLA-Tencor Corporation, SurfScan SP5 instrument). The number of defects in the resist film is shown in Table 2 as a relative value, with the value for the resist composition produced using the porous film of Example 1 being set to 1.00.

[0136] *Because the membrane is hard and easily cracked, it is difficult to create a porous membrane that can be used as a filter membrane.

[0137] As shown in Table 2, the average pore diameter is 9 nm or more and 40 nm or less, and the ２ The surface area per ２ More than 3500m ２ The number of defects in the resist films formed using the resist compositions purified using the porous membranes of Examples 1 to 4, which had an average pore size of 1 nm or less, was small. ２ The surface area per ２ More than 3500m ２ The resist films formed using the resist compositions purified using the porous films of Comparative Examples 1, 2, and 4, which fall outside the range below, had a large number of defects.

Claims

1. A porous membrane made of at least one resin component (A) selected from the group consisting of polyimide, polyamideimide, and polyethersulfone, or a resin composition containing the resin component (A), wherein the average pore size is 9 nm or more and 40 nm or less, and the specific surface area of ​​the porous membrane measured by the BET method is 1 m 2 . ２ The surface area per ２ More than 3500m ２ A porous membrane that is:

2. The porous membrane according to claim 1, having interconnected pores in which the spherical or nearly spherical pores are interconnected.

3. The porous membrane according to claim 1, having a membrane thickness of 40 μm or more and 90 μm or less.

4. The porous film according to claim 1, which is used in the filtration of a liquid resist composition.

5. A method for purifying a resist composition, comprising filtering a liquid resist composition using the porous membrane according to claim 1.

6. A method for producing a resist film, comprising: filtering a liquid resist composition using the porous membrane according to claim 1 to purify the resist composition; applying the purified resist composition onto a substrate to form a coating film; and drying the coating film to form a resist film.

Images