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

Abstract

To provide a porous film capable of satisfactorily removing 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 using a resist composition purified using the porous film.SOLUTION: The porous membrane is composed 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), and has an average pore diameter of 9 nm or more and 40 nm or less, and a surface area per 1m2 of the porous membrane calculated based on a specific surface area of the porous membrane measured by a BET method is 1500m2 or more and 3500m2 or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[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 applying a varnish, in which silica particles are dispersed in a solution of polyamic acid or polyimide, onto a substrate, and then heating the applied film as necessary to obtain a polyimide film containing silica particles.Then, the silica in the polyimide film is dissolved and removed with hydrogen fluoride water to make it porous (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5605566 Summary of the Invention [Problem to be solved by the invention]

[0005] In the manufacturing of semiconductor devices, processing is becoming increasingly finer every day. As a result, minute impurities contained in cleaning solutions, coating solutions, etc. are affecting manufacturing yields. 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. [Means for solving the problem]

[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 Surface area per unit is 1500m 2 More 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), The average pore size is 9 nm or more and 40 nm or less, The specific surface area of ​​the porous membrane measured by the BET method is calculated based on the specific surface area of ​​the porous membrane. 2 Surface area per unit is 1500m 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 provides a method for purifying a liquid resist composition by filtering the liquid resist composition using the porous membrane according to the first aspect; applying the purified resist composition onto a substrate to form a coating film; and drying the coating film to form a resist film. [Effects of the Invention]

[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. DETAILED DESCRIPTION OF THE INVENTION

[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 a resin-particle composite membrane in a later step in the manufacturing method for a porous membrane described below. The interconnected pores can also be said to be adjacent individual pores formed by removing individual particles present in a resin-particle composite membrane in a later step in the manufacturing method for a porous membrane described below, at portions where the individual particles present in the resin-particle composite membrane were in contact with each other.

[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 to pass through the porous membrane.

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

[0016] The mean pore size measured by a porometer is the mean flow pore size measured by liquid-liquid phase displacement. The mean pore size can be measured, for example, using a PMI Liquid Liquid Porometer LLP-1500A (ultra-low pressure, pore size distribution, and permeability measurement device) according to 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 mean 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 applied 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] The specific surface area of ​​the porous membrane measured by the BET method is calculated based on the specific surface area of ​​the porous membrane. 2 The surface area per 2 More than 3500m 2 Below 1800m 2 More than 3000m 2 Preferably, it is: 1m of porous membrane 2 The surface area per 1 m of porous membrane 2 mass (g) per unit area and the specific surface area (m 2 / g).

[0018] When a porous membrane having an average pore size and specific surface area within the above ranges is used as a filter membrane to filter a liquid containing minute impurities, the minute impurities can be effectively removed. This is presumably because the average pore size determined by the BET method within the above range can provide pores such as interconnected pores with a pore size suitable for sieving to remove impurities. Furthermore, by having the surface area of ​​the porous film within the above range, it is possible to increase the frequency of contact between minute impurities and the surfaces of the pores in the porous film, and it is presumed that this increases the efficiency of removing minute impurities by adsorption onto the surfaces of the pores.

[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 material, and the measured data is analyzed based on the BET equation represented by equation (1). Based on this method, the specific surface area A and the total pore volume V can be calculated. Specifically, first, adsorbed molecules are adsorbed and desorbed to the porous material to obtain an adsorption isotherm. Then, from the obtained adsorption isotherm, [P / {V a (P0-P)} is calculated and plotted against the equilibrium relative pressure (P / P0). This plot is then considered as a straight line, and 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 according to 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. From this adsorption amount, the total pore volume V can be calculated. The BET method is a measurement method conforming to 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 measuring device used in the BET method, but examples include Micromeritics (manufactured by Shimadzu Corporation).

[0020] [P / {V a (P0-P)}] =[1 / (V m ·C)]+[(C-1) / (V m ·C)](P / P0) (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 : Monolayer adsorption amount P: Pressure at equilibrium of adsorbed molecules P0: Saturated vapor pressure of adsorbed molecules L: Avogadro's number σ: Adsorption cross section of adsorbed molecule is.

[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 the inner surfaces of the pores in the porous membrane are substantially entirely curved. Such pores are hereinafter sometimes referred to as "spherical or approximately spherical pores." In this specification, "spherical or approximately spherical pores" refers to pores whose inner surfaces form spherical or approximately spherical spaces. Spherical 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 or approximately spherical. In this specification, "spherical or approximately spherical" refers to a concept that includes true spheres, but is not necessarily limited to true spheres, and includes particles that are substantially spherical. In this specification, "substantially spherical" refers to particles with a sphericity of 1±0.3 or less, defined as the sphericity obtained by dividing the major axis by the minor axis. The sphericity of the spherical or approximately spherical pores in the porous membrane is preferably 0.9 to 1.1, more preferably 0.95 to 1.05.

[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 film is produced by a production method including forming a composite film made of a porous film production composition (hereinafter also referred to as "varnish") described below on a substrate, and removing the fine particles (b) from the composite film. The porous film can be produced by the porous film production method described below.

[0027] <Composition for porous membrane production> The composition (varnish) 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, 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) are 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, but the amount of the diamine used is preferably 0.50 to 1.50 moles, more preferably 0.60 to 1.30 moles, and particularly preferably 0.70 to 1.20 moles, per mole of the tetracarboxylic dianhydride.

[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, but from the viewpoint of the heat resistance of the resulting polyimide resin, it is preferable to use an aromatic tetracarboxylic dianhydride. The tetracarboxylic dianhydride may be used alone or in combination of two or more.

[0031] Specific preferred examples of the aromatic tetracarboxylic dianhydride 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 dianhydrides, 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 suitable aliphatic tetracarboxylic dianhydrides 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, and 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride. Examples of suitable aliphatic tetracarboxylic dianhydrides include ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and 1,2,3,4-cyclohexanetetracarboxylic dianhydride. Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride are preferred in terms of price, availability, and the like.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, but aromatic diamines are preferred from the viewpoint of the heat resistance of the resulting polyimide resin. 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 and p-phenylenediamine, and 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] Diaminobiphenyl compounds have two aminophenyl groups bonded together, such as 4,4'-diaminobiphenyl and 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl.

[0036] Diaminodiphenyl compounds are compounds in which two aminophenyl groups are bonded to each other 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. The alkylene group derivative 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'-diaminodiphenyl methane, 3,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl methane, 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) bis(p-aminophenyl)-2-pentene, iminodianiline, 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, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and the like.

[0038] Among these, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, and 4,4'-diaminodiphenyl ether are preferred in terms of price, 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 in the diaminodiphenyl compounds. 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 diaminotetraphenyl compounds 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 cardo-type fluorenediamine derivatives include 9,9-bisanilinefluorene.

[0044] The number of carbon atoms in 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 a halogen atom, a methyl group, a methoxy group, a cyano group, a phenyl group, 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 a method of reacting an acid and a diamine component in a solvent.

[0047] The reaction between tetracarboxylic dianhydride and diamine is usually carried out in a solvent. The solvent used for the reaction between tetracarboxylic dianhydride and diamine is not particularly limited as long as it can dissolve the tetracarboxylic dianhydride and diamine and does not react with the tetracarboxylic dianhydride and 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 phenol-based 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 it is desirable that the content of the produced polyamic acid be 5 to 50 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 composition of the raw materials used, but is usually from 3 hours to 24 hours. The polyamic acid may be used alone or in combination of two or more kinds.

[0051] [Polyimide] The polyimide is not limited in structure or molecular weight, 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] 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, an aliphatic diamine such as ethylenediamine, hexamethylenediamine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, or 4,4'-diaminodicyclohexylmethane; an aromatic diamine such as 2-methyl-1,4-phenylenediamine, o-tolidine, m-tolidine, 3,3'-dimethoxybenzidine, or 4,4'-diaminobenzanilide; a polyoxyalkylene diamine such as polyoxyethylenediamine, polyoxypropylenediamine, or polyoxybutylenediamine; a polysiloxane diamine; or 2,3,3',4'-oxydiphthalic anhydride, 3,4,3',4'-oxydiphthalic anhydride, or 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. The polyimide and the monomer thereof may be used singly or in combination of two or more kinds.

[0053] There are no particular limitations on the means for producing polyimides. For example, known methods such as chemical imidization or thermal imidization of polyamic acid can be used. 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. [ka] [ka]

[0054] [Polyamideimide and polyamideimide precursors] 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 thereof 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'- ... Examples of suitable isocyanates include 2,4-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 Japanese Patent Application Laid-Open Nos. 63-283705 and 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 (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 above acid such as trimellitic anhydride chloride with a diamine. In this specification and claims, "polyamideimide precursor" means a polymer (precursor polymer) before imidization. The polyamideimide and polyamideimide precursor may each be used alone or in combination of two or more thereof.Furthermore, with respect to the polyamideimide, the polymer, raw material monomer, and oligomer may each be used alone or in combination of two or more thereof.

[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 or more and 1,000,000 or less, more preferably 10,000 or more and 300,000 or less.

[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 a 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 process, and either an inorganic material or an organic material can be used.

[0064] Examples of inorganic material particles (b) include inorganic oxide particles, and specific examples include silica (silicon dioxide) particles, titanium oxide particles, and metal oxide particles such as alumina (Al2O3) particles. 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 that satisfy these conditions (b) have excellent dispersibility in the varnish and can be used in a state where they do not aggregate together.

[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 using a combination of fine particles (b1) having a small average particle size and 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 that of the fine particles (b1), and the average particle size of the fine particles (b1) is less than 100 nm, the pore size of the porous membrane produced can be reduced and the flow rate can be improved, as shown in the examples described later. This is thought to be due to the following reasons. The pores (spherical pores) in the porous membrane are formed by removing individual microparticles present in a composite membrane (resin-particle composite membrane) formed using varnish in a subsequent microparticle removal step. The porous membrane includes a structure in which spherical pores are interconnected (communicating pores). The communicating pores are formed in the porous membrane manufacturing method by removing multiple microparticles (b) that are present in contact with each other in a composite membrane (resin-particle composite membrane) formed using varnish in a subsequent microparticle removal step. The points at which the spherical pores in the communicating pores are interconnected originate from the points (contact points) where multiple microparticles (b) come into contact with each other before being removed. The diameter of the communicating holes is measured by the above-mentioned porometer. 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 diameter of the interconnected pores formed at the points where the particles come into contact with each other (contact points) depends on the diameter of the small particles (particles (b1)) and becomes the same diameter as the interconnected pores formed at the contact points between the small particles (particles (b1)). On the other hand, when two types of particles of different sizes (particles (b1) and particles (b2)) are used, the number of pores formed is reduced compared to when only small particles (particles (b1)) are used. This reduces the resistance to fluid flow through the porous membrane, and increases the flow rate of 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 in which the pore size of the communicating holes is small and the fluid flow rate is high when filtering the fluid.

[0070] The fine particles (b1) have an average particle size of 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, or may be, for example, 10 nm or more.

[0071] The average particle size of the fine particles (b2) is larger than the average particle size of the fine particles (b1), and 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, and 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, but may be, for example, 5 nm or more and 140 nm or less, 10 nm or more and 100 nm or less, or 20 nm or more and 60 nm or less.

[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 The average particle size of the fine particles (b2) is 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 50% of the cumulative value 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) contained in the varnish, which is composed of polyamic acid, polyimide, polyamideimide precursor, polyamideimide, and / or polyethersulfone, 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 the above-mentioned nitrogen-containing polar solvents as well as polar solvents such as diphenylsulfone, dimethylsulfone, dimethylsulfoxide, benzophenone, tetrahydrothiophene-1,1-dioxide, and 1,3-dimethyl-2-imidazolidinone.

[0078] [Dispersant] A dispersant may be added together with the fine particles (b) to uniformly disperse the fine particles (b) in the varnish. Adding a dispersant allows the fine particles (b) to be mixed more uniformly in the varnish and to be uniformly distributed in the film formed from the varnish. As a result, dense openings can be formed on the surface of the final porous film, and the front and back surfaces can be efficiently connected, improving the air permeability of the porous film. Furthermore, adding a dispersant tends to improve the drying properties of the varnish and the peelability of the resulting unfired composite film from the substrate, etc.

[0079] The dispersant is not particularly limited, and known dispersants can be used. For example, anionic surfactants such as coconut fatty acid salts, castor sulfated oil salts, lauryl sulfate salts, polyoxyalkylene allyl phenyl ether sulfate salts, alkyl benzene sulfonic acid, alkyl benzene sulfonate salts, alkyl diphenyl ether disulfonate salts, alkyl naphthalene sulfonate salts, 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 ethylene 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 can 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 composition (varnish) for producing the porous film is not particularly limited. The varnish is typically produced by a microparticle dispersion preparation step of dispersing microparticles (b) in a solvent, a step of preparing a resin solution containing resin component (A), and a kneading step of combining and kneading the microparticle dispersion and the resin solution 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 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. For kneading the varnish, a rotation-revolution mixer (trade name: Awatori Rentaro, manufactured by Thinky Corporation), a planetary mixer, a bead mill, or the like can be used. In addition, in the kneading process, the cross-sectional area is 1960 μm 2 More than 785000μm 2 A dispersion treatment may be performed by using a dispersion device equipped with 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 treatment by passing the mixed liquid through such a flow path is the method described in JP 2020-104105 A.

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

[0084] [Composite film formation process (manufacturing unsintered composite film)] In the composite film forming step, a composite film made of the above-mentioned porous film manufacturing composition (varnish) is formed on a substrate. The composite film (hereinafter also referred to as "unfired composite film") may be formed (deposited) directly on a substrate. The composite film (unfired composite film) made of the varnish described above is preferably formed as a single layer film on a substrate. The unsintered composite film can be formed, for example, by applying a varnish to a substrate and then performing a drying step in which the varnish is dried at a temperature of 0°C or higher and 100°C or lower, preferably under atmospheric pressure or in a vacuum, and more preferably at a temperature of 10°C or higher and 100°C or lower, at atmospheric 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 firing step in which the unsintered composite film is fired to obtain a polyimide-particle composite film. The unsintered composite film may be fired as is, or may be peeled off from the substrate before the firing 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. This can cause discoloration during firing or adversely affect the electrical properties, so it is preferable to remove it as much as possible. A washing step in which the unfired composite film peeled from the substrate is washed with an organic solvent can be introduced to remove the release agent.

[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 process (manufacturing resin-particle composite film)] The firing step is a step of firing the composite film after the composite film formation step and before the particulate 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 the baking step may be omitted.

[0089] The firing temperature in the firing 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 firing temperature must be set lower than the thermal decomposition temperature of the organic material. When the resin component (a) contained in the varnish is a polyamic acid, it is preferable to complete imidization in the baking step.

[0090] The firing conditions may include, for example, raising the temperature from room temperature to 400°C or less over 3 hours, followed by holding 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 50°C increments (holding each step for 20 minutes), and finally holding at 400°C for 20 minutes.When an unfired composite film is formed on a substrate and then peeled off from the substrate, a method can be used in which the edges of the unfired composite film are fixed to a stainless steel mold or the like to prevent deformation.

[0091] The thickness of the completed resin-particle composite membrane can be determined by measuring the thickness at multiple locations with, for example, a micrometer and averaging the measured thickness. The preferred average membrane thickness varies depending on the intended use of the porous membrane. For example, when used as a filter, the membrane 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 process (making the resin-particle composite membrane porous)] In the particle removal step, the particles (b) are removed from the composite film after the composite film formation step (if a baking step is performed, the composite film (resin-particle composite film) after the baking step). 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] Organic materials can also be selected as the material for the fine particles (b). Any organic material can be used, as long as it decomposes at a lower temperature than the resin contained in the resin-particle composite film. Examples include resin fine particles made of linear polymers or known depolymerizable polymers. Typical linear polymers undergo random cleavage of the polymer chains during thermal decomposition, while depolymerizable polymers decompose into monomers during thermal decomposition. Both types of fine particles disappear from the porous film by decomposing into low-molecular-weight compounds or CO2. The decomposition temperature of the resin fine 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. A decomposition temperature of 200°C or higher allows film formation even when a high-boiling-point solvent is used in the varnish, broadening the range of baking conditions for the resin-particle composite film. Furthermore, a decomposition temperature of less than 320°C allows the resin fine particles to disappear without thermally damaging the resin contained in the resin-particle composite film.

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

[0096] [Resin removal process] 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 a resin removal step of 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 the resin portion is not removed.

[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] Chemical etching methods include treatment with chemical etching solutions such as inorganic alkaline solutions or organic alkaline solutions. 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 alkali hydroxides, 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 and 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] Physical methods that can be used include, for example, dry etching using plasma (oxygen, argon, etc.) or corona discharge, and a surface treatment method in which an abrasive (e.g., alumina (hardness 9)) is dispersed in a liquid and irradiated onto the surface of the film at a speed of 30 to 100 m / s.

[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 onto 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 method> The porous membrane described above is used to filter a liquid. The purpose of the filtration is not particularly limited. Examples of the purpose of the 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 chemical liquids used in semiconductor device manufacturing. Specific examples of chemical liquids 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, etc. 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 such as (meth)acrylate compounds, epoxy compounds, vinyl ether compounds, and methylol compounds, or crosslinking agents; 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 method for refining liquid> The method for purifying a liquid involves forcing some or all of the liquid through a porous membrane as described above from one side to the other by differential pressure.

[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 liquid purification 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, but 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 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 permeating the porous membrane. For example, pressure is preferably applied by utilizing the pressure generated by circulating or feeding the supply liquid or by utilizing positive gas pressure. Pressurization can be performed using an active pressurizing device such as a pump (a liquid feed 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, and although this may be reduced by a pump, it is preferable to reduce the pressure to a vacuum. When the supply liquid is circulated or sent 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 depressurization, for example, a method utilizing both pressurization of the liquid by a device such as a pump and depressurization, a method utilizing both pressurization by gas and depressurization, or a method utilizing pressurization of the liquid by a device such as a pump, and pressurization by gas and depressurization. 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 depressurization, is preferred in terms of simplifying production. 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 across the porous membrane by providing a pressure difference may be appropriately set depending on the membrane thickness, porosity or average pore size of the porous membrane used, or the desired degree of purification, flow rate, flow velocity, or concentration or viscosity of the feed liquid, but for example, in the case of a so-called cross-flow method (where the feed liquid flows parallel to the porous membrane), it is, for example, 3 MPa or less, and in the case of a so-called dead-end method (where the feed liquid flows crosswise to the porous membrane), it 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 supply liquid through the porous membrane, a solution of an alcohol such as methanol, ethanol, or isopropyl alcohol, a ketone such as acetone or methyl ethyl ketone, water, a solvent contained in the supply liquid, or a mixture thereof may be brought into contact with the porous membrane and passed through in order to wash the porous membrane, improve the wettability of the porous membrane with the supply liquid, or adjust the surface energy between the porous membrane and the supply liquid. In contacting the porous membrane with the solution before the feed solution is passed through, the porous membrane may be impregnated or immersed in the solution, and by contacting the porous membrane with the solution, for example, the solution can be allowed to penetrate into the pores inside the porous membrane. The contacting of the porous membrane with the solution before the feed solution is passed through may be carried out by the above-mentioned pressure difference, and in particular, when the solution is allowed to penetrate into the pores inside the porous membrane, the contacting may be carried out under pressure.

[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 filtering material. Specifically, it may be used alone, or it may be used as a filtering material to which another functional layer (membrane) is added, or it may be used as a membrane to be combined with another filtering material, 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 those having chemical or physicochemical functions, such as nylon membranes, polytetrafluoroethylene (PTFE) membranes, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) membranes, and membranes modified from these.

[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 semiconductor manufacturing. It 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 a filter device, the porous membrane is arranged so that the feed liquid and the filtrate intersect. With respect to the liquid flow path, the porous membrane may be arranged parallel to the flow path or intersect the flow path. To separate the feed liquid from the filtrate, the regions before and after passing through the porous membrane are appropriately sealed. For example, as a sealing method, the porous membrane may be processed, as needed, by light (UV) curing or heat bonding (including anchoring effect bonding (thermal welding, etc.)), or bonding with an adhesive. Alternatively, the porous membrane of the present invention can be bonded to another filter material (filter) by, for example, an integration method. 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, or polyamideimide.

[0119] <<Resist film manufacturing method>> 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 by being 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] A 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 onto 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 substrate material, coating method, coating film drying method, development method, etc. are appropriately selected from well-known materials and methods, taking into consideration the type of resist composition and the intended 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 comprising 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 average pore size is 9 nm or more and 40 nm or less, The specific surface area of ​​the porous membrane measured by the BET method is calculated based on the specific surface area of ​​the porous membrane. 2 Surface area per unit is 1500m 2 More than 3500m 2 A porous membrane that is: (2) The porous membrane according to (1), which has interconnected pores in the form of spherical or nearly spherical pores. (3) The porous membrane according to (1) or (2), having a membrane 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, comprising filtering a liquid resist composition using the porous membrane according to any one of (1) to (4). (6) Purifying a liquid resist composition by filtering the resist composition using the porous membrane according to any one of (1) to (4). applying the purified resist composition onto a substrate to form a coating film; and drying the coating film to form a resist film. [Example]

[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 a dispersant relative to the mass of silica. Furthermore, organic solvent (1) and organic solvent (2) were added to the composition for producing a porous membrane (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 at 4000 rpm with a stirring blade for 30 minutes to disperse the silica in the mixture. 2 Using a dispersing device equipped with a flow path of 1000 psi, the mixture was passed through the flow path at 200 MPa for 10 cycles to prepare a composition for producing a porous membrane (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 silica types are as listed in Table 1. Polyamic acid solution: reaction product of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether (solid 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. The formed 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 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 membranes was calculated. 2 The average pore size and surface area are shown in Table 1.

[0129] [Table 1]

[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] Polymer compounds (1) [ka]

[0133] Acid Generator (1) [ka]

[0134] <Change in mass average molecular weight of resin contained in resist composition due to filtration> The weight average molecular weight (Mw1) of the resin contained 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 weight average molecular weight calculated as polystyrene 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 x 100

[0135] <Number of defects in resist film> The resist compositions purified using the porous membranes of Examples 1 to 4 and Comparative Examples 1 to 5 were each applied using a spinner onto a 12-inch silicon substrate treated with hexamethyldisilazane (HMDS). The formed coating was pre-baked on a hot plate at 80°C for 60 seconds to dry the coating, 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 inspection 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 membrane of Example 1 set at 1.00.

[0136] [Table 2] *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 size is 9 nm or more and 40 nm or less, and the 2 Surface area per unit is 1500m 2 More than 3500m 2 The resist films formed using the resist compositions purified using the porous films of Examples 1 to 4 below had a small number of defects. On the other hand, if the average pore size is outside the range of 9 nm to 40 nm or 2 Surface area per unit is 1500m 2 More than 3500m 2 The resist films formed using the resist compositions purified using the porous membranes of Comparative Examples 1, 2, and 4, which fall outside the range below, had a large number of defects.

Claims

1. A porous membrane comprising 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 average pore diameter is 9 nm or more and 40 nm or less, The specific surface area of ​​the porous membrane measured by the BET method is calculated based on the specific surface area of ​​the porous membrane. ２ The surface area per ２ More than 3500m ２ A porous membrane that is:

2. The porous membrane according to claim 1 , wherein the spherical or nearly spherical pores have interconnected pores.

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 a filtration process 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. 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.

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