JP2011122124A - Porous film and method of producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous film having excellent pore characteristics, flexibility, handling and molding workability and further film strength, heat resistance, chemical resistance and durability by crosslinking structure formation and a method of producing the same. <P>SOLUTION: The porous film in which many micropores are present comprises a composition containing a polymer having a cross-linkable functional group as an essential component and a cross-linking agent cross-linking the cross-linkable functional group. The average pore diameter of micropores in the porous film is 0.01-10 μm and the porosity is 30-85%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a porous membrane mainly composed of a polymer and a method for producing the same, and more particularly to a porous membrane excellent in membrane strength, heat resistance, chemical resistance and durability and a method for producing the same.

  The porous membrane of the present invention utilizes the pore characteristics of the porous membrane to provide separation membranes in membrane separation technologies such as microfiltration and separation / concentration, low dielectric constant materials, battery separators, electrolytic capacitors, cushioning materials, It can be used as a wide range of substrate materials such as ink image-receiving sheets, insulating materials, heat insulating materials, and electrolyte membrane base materials. Furthermore, by making the surface of the porous membrane functional, it can be used as circuit boards, heat radiation materials (heat sinks, heat radiation plates), electromagnetic wave control materials such as electromagnetic wave shields and electromagnetic wave absorbers, antennas, cell culture substrates, etc. be able to.

  Since the porous film of the present invention exhibits excellent printing characteristics due to the micropores of the porous film, fine printing of the functional material on the porous film is possible. It is useful as a substrate material for circuit boards, antennas, heat sinks and the like.

  Conventionally, porous membranes mainly composed of polymers have been known. As a method for producing the porous membrane, a solution containing a polymer that is to constitute the porous membrane is cast on a substrate in the form of a film, which is then introduced into a coagulation liquid to obtain a porous membrane (wet process). The phase change method is known.

  For example, JP-A-2003-313356, JP-A-2004-175104, JP-A-2005-162858, JP-A-2007-126638, and JP-A-2007-246876 disclose porosity by a wet phase conversion method. A porous membrane consisting only of a porous layer is disclosed.

  Japanese Patent Application Laid-Open No. 2009-73124 discloses a laminate composed of a substrate and a porous layer formed by a wet phase conversion method, and discloses a porous film formed only of a porous layer formed by a wet phase conversion method. Has been.

JP 2003-313356 A JP 2004-175104 A JP 2005-162885 A JP 2007-126638 A JP 2007-246876 A JP 2009-73124 A JP 2006-237322 A

  However, recently, the applications to which the porous membrane is applied are spreading, and in the conventional porous membrane mainly composed of a polymer, performance required for each usage, for example, membrane strength, heat resistance, chemical resistance, Performance such as durability is often insufficient.

  For example, in various applications, porous membranes may be exposed to strong polar solvents, alkalis, acids, and other chemicals. Moreover, when forming a functional layer (functional pattern) on a porous membrane, it may receive a high temperature process. In addition, it is not preferable to cause a dimensional change even in a high temperature and high humidity environment during the use period of the porous membrane. Furthermore, it is necessary that the porous membrane can withstand repeated use.

  An object of the present invention is a porous film mainly composed of a polymer, which has excellent pore characteristics, flexibility, excellent handleability and moldability, and formation of a crosslinked structure, resulting in film strength and heat resistance. An object of the present invention is to provide a porous film having excellent properties, chemical resistance and durability, and a method for producing the same.

  Another object of the present invention is to obtain a functional laminate in which a functional layer made of a functional material such as a conductive material is formed on the surface of the porous membrane or the polymer layer derived from the porous membrane. Another object of the present invention is to provide the porous membrane used also in the present invention.

The present invention includes the following inventions.
(1) A porous membrane having a large number of micropores,
The porous membrane is composed of a composition comprising a polymer having a crosslinkable functional group as a main component and a crosslinker capable of undergoing a crosslinking reaction with the crosslinkable functional group,
A porous film having an average pore diameter of 0.01 to 10 μm and a porosity of 30 to 85% in the porous film.

  The polymer constituting the porous film has a crosslinkable functional group. The crosslinking agent is capable of crosslinking with a functional group in each polymer. Therefore, according to the said crosslinking agent, a crosslinked structure is formed in the said porous film by performing a heat processing and / or an active energy ray irradiation process, and making a crosslinking agent react.

  (2) The crosslinkable functional group contained in the polymer is at least one selected from the group consisting of an amide group, a carboxy group, an amino group, an isocyanate group, a hydroxyl group, an epoxy group, an aldehyde group, and an acid anhydride group. The porous membrane as described in (1) above.

  (3) The polymer according to (1) or (2), wherein the polymer is at least one selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyamide resin, and a polyetherimide resin. Porous membrane.

  (4) The crosslinking agent is at least one selected from the group consisting of a compound containing two or more epoxy groups, a polyisocyanate compound, and a silane coupling agent, among the above (1) to (3) A porous membrane according to any one of the above.

  (5) The porous membrane according to any one of (1) to (4), wherein the porous membrane has a thickness of 5 to 200 μm.

  (6) The porous film is a film of a porous film forming material containing the polymer and the cross-linking agent that should form the porous film, and is cast into a film on a substrate. This is formed by immersing this in a coagulation liquid, peeling the film-like porous layer from the base material, and then subjecting the film-like porous layer to drying. ). The porous membrane according to any one of the above.

  (7) The porous membrane according to any one of (1) to (6), wherein the crosslinking agent contained in the porous membrane is in an unreacted state.

  (8) The porous membrane according to any one of (1) to (6), wherein the porous membrane has a cross-linked structure formed by the cross-linking agent.

(9) A method for producing the porous membrane according to any one of (1) to (8) above,
A solution of a porous film forming material containing the polymer and the cross-linking agent that constitute the porous film is cast into a film on a base material, and then immersed in a coagulation liquid. A method for producing a porous membrane, comprising peeling the film-like porous layer from the substrate and then subjecting the film-like porous layer to drying.

  (10) After casting the solution of the material for forming a porous film in the form of a film on the substrate, it is kept in an atmosphere of relative humidity of 70 to 100% and temperature of 15 to 100 ° C. for 0.2 to 15 minutes. Then, the method for producing a porous membrane according to the above (9), wherein this is immersed in a coagulation liquid.

(11) On the surface of the porous film according to any one of the above (1) to (6) or the polymer layer derived from the porous film, a conductor layer, a dielectric layer, a semiconductor layer, an insulator A functional laminate having a functional layer selected from the group consisting of a layer and a resistor layer,
The porous film or the polymer layer derived from the porous film is a functional laminate in which a crosslinked structure is formed by the crosslinking agent.

  In this specification, the polymer layer derived from the porous membrane is used for crosslinking treatment (heating treatment, active energy ray irradiation treatment) for forming a crosslinked structure and / or for expressing the functionality of the functional layer. This means a layer in which the micropores in the porous film have disappeared by the treatment (heat treatment or the like). The polymer layer derived from the porous membrane may be transparent due to the disappearance of micropores.

  (12) The functional layered product according to (11), wherein the functional layer is patterned.

(13) On the surface of the porous film according to any one of (1) to (6) or the polymer layer derived from the porous film, a conductor layer, a dielectric layer, a semiconductor layer, an insulator A method for producing a functional laminate having a functional layer selected from the group consisting of a layer and a resistor layer,
On the surface of the porous film according to any one of (1) to (6) above, a conductor layer, a dielectric layer, a semiconductor layer, an insulator layer, a resistor layer, and a precursor layer of the layer Forming a layer selected from the group consisting of:
A method for producing a functional laminate, comprising performing heat treatment and / or active energy ray irradiation treatment to form a crosslinked structure with the crosslinking agent in the porous film.

  (14) The functional layered product according to (13), wherein the functional layer is patterned.

  In the porous membrane of the present invention, the average pore diameter and porosity of the micropores in the porous membrane are in a specific range, and the porous membrane is excellent in flexibility, folding resistance, and handleability.

  And since the said porous membrane is comprised from the composition containing the polymer which has a functional group which can be bridge | crosslinked, and the crosslinking agent which can be bridge | crosslinked with the said functional group, according to the kind of said crosslinking agent Thus, a crosslinked structure is formed in the porous film by performing a crosslinking treatment such as a heat treatment and / or an active energy ray irradiation treatment. By forming a crosslinked structure, a porous film excellent in film strength, heat resistance, chemical resistance (solvent resistance, acid resistance, alkali resistance, etc.) and durability can be obtained.

  Further, when the porous film is a heat-resistant polymer made of a resin material selected from the group consisting of a polyimide-based resin, a polyamide-imide resin, a polyamide-based resin, and a polyetherimide-based resin, further heat resistance, A porous membrane excellent in chemical resistance and durability can be obtained.

  The porous membrane of the present invention utilizes the pore characteristics of the porous membrane to provide separation membranes in membrane separation technologies such as microfiltration and separation / concentration, low dielectric constant materials, battery separators, electrolytic capacitors, cushioning materials, It can be used as a wide range of substrate materials such as ink image-receiving sheets, insulating materials, heat insulating materials, and electrolyte membrane base materials. Furthermore, by making the surface of the porous membrane functional, it can be used as circuit boards, heat radiation materials (heat sinks, heat radiation plates), electromagnetic wave control materials such as electromagnetic wave shields and electromagnetic wave absorbers, antennas, cell culture substrates, etc. be able to.

  Since the porous film of the present invention exhibits excellent printing characteristics due to the micropores of the porous film, fine printing of the functional material on the porous film is possible. It is useful as a substrate material for circuit boards, antennas, heat sinks and the like.

  In addition, the porous membrane of the present invention provides a functional laminate in which a functional layer made of a functional material such as a conductive material is formed on the surface of the porous membrane or the polymer layer derived from the porous membrane. Therefore, it is also preferably used. By forming the crosslinked structure, the porous film or the polymer layer derived from the porous film is excellent in film strength, heat resistance, chemical resistance, and durability.

It is a top view for demonstrating the dimensional change measurement in a chemical-resistance evaluation test.

1: Porous membrane sample a, b, c: Each side of right triangle

  The porous membrane of the present invention will be described.

  The porous membrane of the present invention is a porous membrane having a large number of micropores, and the porous membrane is composed of a polymer having a crosslinkable functional group as a main component, and a crosslinkable functional group. It is comprised from the composition containing the crosslinking agent which can react, The average hole diameter of the micropore in the said porous membrane is 0.01-10 micrometers, and the porosity is 30-85%. By forming a crosslinked structure, a porous film having excellent film strength, heat resistance, chemical resistance and durability can be obtained.

  Examples of the crosslinkable functional group contained in the polymer constituting the porous membrane include an amide group, a carboxy group, an amino group, an isocyanate group, a hydroxyl group, an epoxy group, an aldehyde group, and an acid anhydride group. it can. Any number of these functional groups may be contained in the polymer.

  The polymer constituting the porous membrane has at least one high functional group having a crosslinkable functional group selected from the group consisting of polyimide resins, polyamideimide resins, polyamide resins, and polyetherimide resins. Molecules are preferred. These polymer components have excellent heat resistance, can be thermoformed, and have excellent mechanical strength, chemical resistance, and electrical characteristics.

  Polyamideimide resin can be usually produced by imidization after polymerization by reaction of trimellitic anhydride and diisocyanate, or reaction of trimellitic anhydride chloride and diamine. Since it has many amide groups in the molecule, it can be preferably used as a crosslinkable functional group. In addition, some imides remain reactive as unreacted precursors (amic acids), and the amide groups and carboxyl groups that make up the amic acids can be used as crosslinkable functional groups. Can do. In addition, since the polyamideimide resin is produced by polymerization by reaction of trimellitic anhydride and diisocyanate or reaction of trimellitic anhydride chloride and diamine as described above, a carboxyl group, isocyanate group, amino In many cases, groups and the like remain, and these can also be used as crosslinkable functional groups.

  A polyimide-type resin can be manufactured by obtaining a polyamic acid (polyimide precursor) by reaction with a tetracarboxylic acid component and a diamine component, and imidating it further, for example. When the porous layer is composed of a polyimide resin, the solubility becomes worse when imidized, so first form a porous film at the polyamic acid stage and then imidize (thermal imidization, chemical imidization, etc.) Good. Since the precursor molecule has a large number of carboxyl groups and amide groups, it can be preferably used as a crosslinkable functional group. In addition, as in the case of the polyamideimide resin, a carboxyl group, an amino group, or the like often remains at the terminal, and these can also be used as crosslinkable functional groups.

  The polyamide-based resin can be produced by polycondensation of diamine and dicarboxylic acid, ring-opening polymerization of lactam, polycondensation of aminocarboxylic acid, or the like. Aromatic polyamide resins are also included. Since it has many amide groups in the molecule, it can be preferably used as a crosslinkable functional group. As in the case of the polyamideimide resin, a carboxyl group, an amino group or the like often remains at the terminal, and these can be used as a crosslinkable functional group.

  The polyetherimide resin can be produced, for example, by obtaining a polyamic acid by a reaction between an aromatic tetracarboxylic acid component having an ether bond and a diamine component, and further imidizing it. The amide group and carboxyl group constituting this amic acid can be used as a crosslinkable functional group. Further, as in the case of the polyamideimide resin, a carboxyl group, an isocyanate group, an amino group, etc. often remain at the terminal, and these can also be used as crosslinkable functional groups.

  Such crosslinkable functional groups may be present in the precursor of the polymer. An imide resin (polyimide resin, polyamideimide resin, polyetherimide resin) is a precursor in which the imide group part is completely unreacted (amic acid), or a part of the precursor is unreacted Some can be produced in the form of a body (amic acid), and some are actually sold in that form. Generally, it is used as an imide resin by converting an amic acid to an imide by heating, but in the present invention, an amide group or a carboxyl group constituting this precursor amic acid is used as a crosslinkable functional group. Including that.

  Moreover, you may introduce | transduce into these resin the functional group which can be bridge | crosslinked by modifying a polyimide-type resin, a polyamideimide-type resin, a polyamide-type resin, or a polyetherimide-type resin.

  The crosslinkable functional group may be present in the main chain of the resin or may be present in the side chain. Furthermore, it may exist in the middle of the molecular chain or may exist at the end. Moreover, the crosslinkable functional group may exist in the benzene ring contained in the polymer.

  In the present invention, as a polymer constituting the porous membrane, in addition to polyimide resin, polyamideimide resin, polyamide resin, polyetherimide resin, for example, polyethersulfone resin, polycarbonate resin, polyphenylene sulfide Resins, polyester resins, liquid crystalline polyester resins, polybenzoxazole resins, polybenzimidazole resins, polybenzothiazole resins, polysulfone resins, cellulose resins, acrylic resins, and the like may be used.

  These polymer components may be used singly or in combination of two or more, and copolymers of the above resins (graft polymer, block copolymer, random copolymer) alone or in combination. It is also possible to use it. Furthermore, you may use the polymer which contains the frame | skeleton (polymer chain) of the said resin in a principal chain or a side chain. Specific examples of such a polymer include a polysiloxane-containing polyimide containing a polysiloxane and polyimide skeleton in the main chain, and as a crosslinkable functional group, an amide group or a carboxyl group constituting the amic acid of the polyimide precursor Can be used.

  The crosslinking agent is capable of reacting with the crosslinkable functional group of the polymer to crosslink. Examples of the cross-linking agent include compounds containing two or more epoxy groups, polyisocyanate compounds, and silane coupling agents.

  The compound containing two or more epoxy groups is a crosslinkable functional group (amide group, carboxy group, amino group, isocyanate group, hydroxyl group, epoxy group, aldehyde group, acid anhydride, etc. possessed by the polymer. Group). The compound containing two or more epoxy groups is generally often referred to as an epoxy resin.

  Various epoxy resins such as bisphenol A type and bisphenol F type bisphenol type, novolak type glycidyl ether type epoxy resins such as phenol novolak type and cresol novolak type, alicyclic epoxy resins, and modified resins thereof Resins can be mentioned. Commercially available epoxy resins include “Araldite” from Huntsman Advanced Materials, “Denacol” from Nagase ChemteX, “Celoxide” from Daicel Chemical Industries, “Epototo” from Toto Kasei, Japan Epoxy Resin “JER” or the like can be used.

  The polyisocyanate compound can react with a crosslinkable functional group (a carboxy group, an amino group, a hydroxyl group, an epoxy group, an acid anhydride group) possessed by the polymer. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), phenylene diisocyanate, diphenyl diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI), lysine diisocyanate, and the like Aliphatic polyisocyanates such as isophorone diisocyanate (IPDI), cyclohexane-1,4-diisocyanate, and hydrogenated MDI. As commercially available products of polyisocyanate compounds, “Takenate” from Mitsui Chemicals Polyurethanes, “Coronate” from Japan Polyurethanes, etc. can be used.

  The silane coupling agent can react with a crosslinkable functional group (amide group, carboxy group, amino group, isocyanate group, hydroxyl group, epoxy group, aldehyde group, acid anhydride group) possessed by the polymer. . Examples of the silane coupling agent include N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane and 3-glycidoxypropyltriethoxysilane. A silane coupling agent from Shin-Etsu Chemical Co., Ltd. can be used. When various functional layers are formed on the surface of the porous membrane, it is effective for improving the adhesion between the porous membrane and the functional layer.

  Examples of the crosslinking agent other than the above include melamine resin, phenol resin, urea resin, guanamine resin, alkyd resin, dialdehyde compound, acid anhydrides and the like.

  The melamine resin can react with a crosslinkable functional group (amino group, hydroxyl group, aldehyde group) possessed by the polymer. As the melamine resin, for example, “Uban 20SB” from Mitsui Chemicals, Inc. and “Super Becamine” from DIC can be used.

  The phenol resin can react with a crosslinkable functional group (a carboxy group, an amino group, a hydroxyl group, an epoxy group, an isocyanate group, an aldehyde group, an acid anhydride group) possessed by the polymer. As the phenol resin, for example, “Sumilite Resin” manufactured by Sumitomo Bakelite Co., Ltd. can be used.

  The urea resin can react with a crosslinkable functional group (amino group, hydroxyl group, aldehyde group) possessed by the polymer. For example, “Uban 10S60” manufactured by Mitsui Chemicals, Inc. can be used as the urea resin.

  The guanamine resin can react with a crosslinkable functional group (aldehyde group) possessed by the polymer. As the guanamine resin, for example, “Nicarac BL-60” manufactured by Sanwa Chemical Co., Ltd. can be used.

  The alkyd resin can react with a crosslinkable functional group (a carboxy group, a hydroxyl group, an epoxy group, an isocyanate group, an acid anhydride group) possessed by the polymer. As the alkyd resin, for example, “Becozole” manufactured by DIC can be mentioned.

  The dialdehyde compound can react with a crosslinkable functional group (amino group, hydroxyl group) possessed by the polymer. An example of the dialdehyde compound is glyoxal.

  Acid anhydrides can react with crosslinkable functional groups (amino group, epoxy group, isocyanate group) possessed by the polymer. As acid anhydrides, tetrahydrophthalic anhydride (THPA), hexahydrophthalic anhydride (HHPA), methyltetrahydrophthalic anhydride (Me-THPA), methylhexahydrophthalic anhydride (Me-HHPA), methyl nadic anhydride (NMA), hydrogenated methylnadic acid anhydride (H-NMA), trialkyltetrahydrophthalic anhydride (TATHPA), methylcyclohexenetetracarboxylic dianhydride (MCTC), phthalic anhydride (PA), trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), benzophenonetetracarboxylic dianhydride (BTDA), ethylene glycol bisanhydro trimellitate (TMEG), glycerin bis (anhydro trimellitate) monoacetate (TMTA), Dodecenyl anhydride Click acid (DDSA), aliphatic dibasic acid polyanhydrides can include chlorendic anhydride and the like.

  In the present invention, a crosslinking agent may be selected in consideration of reactivity depending on the type of the polymer used. You may use a crosslinking agent 1 type or in combination of 2 or more types.

  Examples of the method of reacting a crosslinkable functional group in a polymer with a crosslinking agent include physical treatment by irradiation with heat and active energy rays (visible light, ultraviolet rays, electron beams, radiation). It is preferably used because the heat treatment is simple. In addition, irradiation with active energy rays such as ultraviolet rays, electron beams, and radiations is preferably used because it can give large energy in a short time and promote the reaction. Further, the reaction of the crosslinking agent can be allowed to proceed without a catalyst, but a catalyst can be added to promote the reaction.

  In the composition constituting the porous membrane, the compounding ratio of the polymer having a crosslinkable functional group and the crosslinker capable of crosslinking with the functional group is not particularly limited, and a desired crosslink It is appropriately determined in consideration of the degree, the kind of polymer and crosslinking agent, the reactivity between the functional group and the crosslinking agent, and the like. For example, the crosslinking agent may be 2 to 312.5 parts by weight with respect to 100 parts by weight of the polymer. If the crosslinking agent is less than 2 parts by weight relative to 100 parts by weight of the polymer, the degree of crosslinking will be small. When the crosslinking agent exceeds 312.5 parts by weight with respect to 100 parts by weight of the polymer, the crosslinking agent becomes excessive, and there is a possibility that the crosslinking agent that does not contribute to the crosslinking reaction remains in the porous film after the crosslinking treatment. About the minimum amount of a crosslinking agent, 10 weight part or more of crosslinking agents are preferable with respect to 100 weight part of polymers, and 20 weight part or more of crosslinking agents are more preferable. About the upper limit of a crosslinking agent, 200 weight part or less of a crosslinking agent is preferable with respect to 100 weight part of polymers, and 150 weight part or less of a crosslinking agent is more preferable.

  The thickness of the porous membrane is, for example, 5 to 200 μm, preferably 10 to 100 μm, and more preferably 15 to 50 μm. If the thickness is too thin, it will be difficult to produce stably, and cushion performance may be degraded, and printing characteristics may be degraded. On the other hand, when it is too thick, it becomes difficult to uniformly control the pore size distribution.

  In the present invention, the large number of micropores of the porous membrane may be independent micropores with low communication or may be micropores with communication. The average pore diameter of the micropores in the porous membrane (= the average pore size of the micropores inside the porous membrane) is 0.01 to 10 μm, preferably 0.05 to 5 μm. When the average pore diameter is outside the above range, the pore characteristics are inferior in that it is difficult to obtain a desired effect according to the application. When the average pore diameter is smaller than 0.01 μm, cushion performance may be deteriorated or heat insulation may be deteriorated, and a porous membrane is difficult to produce by the phase separation method of the present invention. On the other hand, when the average pore diameter exceeds 10 μm, it is difficult to uniformly control the pore diameter distribution in the porous film, and the relative dielectric constant may be nonuniform in each part of the porous film.

  The feature that the porous film has a large number of micropores can be determined by observation with an electron microscope. In many cases, the presence of spherical chambers, circular / elliptical holes, or fibrous components can be determined by observation from the surface of the porous membrane, and spherical walls can be determined by observing the cross section of the porous membrane. It is possible to confirm the existence of a small chamber surrounded by a fibrous structure. A thin skin layer may be formed on the surface of the porous membrane, or may be a state in which a hole is opened.

  The porosity (average porosity) in the porous layer is, for example, 30 to 85%, preferably 35 to 85%, and more preferably 40 to 85%. When the porosity is out of the above range, it is difficult to obtain desired porosity characteristics corresponding to the application.For example, if the porosity is too low, the dielectric constant increases, the cushion performance decreases, the heat insulating property May decrease, and printing characteristics may deteriorate. On the other hand, if the porosity is too high, the strength and folding resistance may be inferior.

  Since the porous membrane has such an average pore diameter and porosity, it has flexibility and excellent pore characteristics, and has an appropriate rigidity, so that handling properties are improved.

  Moreover, as a hole area ratio (surface hole area ratio) of the surface of a porous membrane, it is 90% or less (for example, 0 to 90%), for example, Preferably it is about 0 to 80%. If the surface area ratio is too high, the mechanical strength and folding resistance may be easily lowered. Depending on the application, the higher the porosity of the surface of the porous membrane, the better, and the lower the better.

  For example, when manufacturing a copper-clad laminate with a low dielectric constant substrate by bonding a porous film and copper foil, the adhesive may penetrate into the copper foil when bonding to the copper foil, which may reduce the relative dielectric constant. In addition, when a circuit is formed by further etching, the etching solution may penetrate into the porous film and undesired etching may occur from the inside, so that the surface porosity is preferably low.

  For example, when it is used as an electrolyte membrane substrate for a fuel cell, it is preferable that the surface porosity is higher because the porous membrane is filled with an electrolyte. In addition, when plating or printing is performed on the surface of the porous film, an appropriate opening may be preferable in order to exert an anchor effect and ensure adhesion with the plating or ink. In addition, in order to sufficiently wash the water-soluble polar solvent and the water-soluble polymer used when forming the porous film, an appropriate opening may be preferable.

  The porous membrane of the present invention is obtained by casting a solution of a porous membrane forming material containing the polymer and the cross-linking agent that constitute the porous membrane into a film, and then It can be produced by immersing this in a coagulation liquid, peeling the film-like porous layer from the substrate, and then subjecting the film-like porous layer to drying. That is, after forming a film-like porous layer on a substrate using a wet phase change method, the film-like porous layer is peeled off from the substrate and dried.

  Examples of the base material used in this production include glass plates; polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate (PET); polycarbonate resins, styrene resins, polytetrafluoroethylene (PTFE), and polyvinylidene fluoride ( PVDF) and other fluorine-based resins, vinyl chloride resins, plastic sheets made of other resins; stainless steel plates, metal plates such as aluminum, and the like. In addition, the base material which consists of several layers from which the surface raw material by which the solution of the material for porous membrane formation should be cast | casted and a back surface material or an internal raw material differs may be sufficient.

  The solution of the porous film forming material (hereinafter sometimes referred to as the porous film solution) includes, for example, a polymer component that is a main material constituting the porous film, a crosslinking agent, and a water-soluble polar solvent. It contains a water-soluble polymer as required and water as required.

  In the solution for the porous membrane, instead of the polymer component constituting the porous membrane, the monomer component (raw material) of the polymer component, its oligomer, the precursor before imidization or cyclization, etc. May be used.

  The addition of a water-soluble polymer or water to the porous membrane solution is effective for making the membrane structure porous like a sponge. Examples of the water-soluble polymer include polyethylene glycol, polyvinyl pyrrolidone, polyethylene oxide, polyvinyl alcohol, polyacrylic acid, polysaccharides, derivatives thereof, and mixtures thereof. Of these, polyvinylpyrrolidone is preferable in that it can suppress the formation of micropores inside the porous membrane and improve the mechanical strength of the porous membrane. These water-soluble polymers can be used alone or in combination of two or more. From the viewpoint of porosity, the weight average molecular weight of the water-soluble polymer is preferably 200 or more, preferably 300 or more, particularly preferably 400 or more (for example, about 400 to 200,000), and particularly the molecular weight. It may be 1000 or more. The pore size can be adjusted by adding water. For example, increasing the amount of water added to the porous membrane solution can increase the pore size.

  The water-soluble polymer is very effective for making the membrane structure into a homogeneous sponge-like porous structure, and various structures can be obtained by changing the type and amount of the water-soluble polymer. For this reason, the water-soluble polymer is very suitably used as an additive for forming a porous film for the purpose of imparting desired pore characteristics.

  On the other hand, the water-soluble polymer is an unnecessary component to be removed that does not ultimately form a porous film. In the method of the present invention using the wet phase conversion method, the water-soluble polymer is removed by washing in a step of phase conversion by dipping in a coagulating liquid such as water. On the other hand, in the dry phase conversion method, components that do not constitute the porous membrane (unnecessary components) are removed by heating, and water-soluble polymers are usually unsuitable for removal by heating, making them extremely difficult to use as additives. It is. Thus, while it is difficult to form various pore structures depending on the dry phase conversion method, the production method of the present invention can easily produce a porous film having desired pore characteristics. Is advantageous in that it is possible.

  However, when the amount of the water-soluble polymer is increased, the hole communication tends to be increased. Therefore, when it is preferable that the connectivity is low, the amount of the water-soluble polymer is preferably the minimum amount. Since the strength tends to decrease as the connectivity increases, it is not preferable to add an excessive amount of the water-soluble polymer. Excessive addition is not preferable because it requires a longer washing time. It is also possible not to use a water-soluble polymer.

  Examples of the water-soluble polar solvent include dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), 2-pyrrolidone, γ-butyrolactone, and the like. A mixture having solubility (good solvent for the polymer component) can be used according to the chemical skeleton of the resin used as the polymer component.

  The compounding amount of each component in the porous membrane solution is 8 to 25% by weight of the polymer component, 0.5 to 25% by weight of the cross-linking agent, and 0 of the water-soluble polymer, based on the solution for the porous membrane. It is preferable to set it as -50 weight%, water 0-10 weight%, and water-soluble polar solvent 30-82 weight%. At this time, if the concentration of the polymer component is too low, the thickness of the porous film becomes insufficient or it is difficult to obtain desired pore characteristics. On the other hand, if the concentration of the polymer component is too high, the porosity is low. Tend to be smaller. When the concentration of the crosslinking agent is too low, it is difficult to obtain a sufficient improvement effect of chemical resistance and heat resistance. On the other hand, if the concentration of the crosslinking agent is too high, the surface of the resulting porous film tends to be sticky, and there is a risk that excess crosslinking agent will remain even after crosslinking. If the concentration of the water-soluble polymer is too high, problems such as poor solubility of each component in the solution for the porous membrane and a decrease in the strength of the porous membrane are likely to occur. The amount of water added can be used to adjust the pore size, and the pore size can be increased by increasing the amount added.

  The porous membrane solution is cast into a film on a substrate, and then immersed in a coagulation liquid.

  The coagulation liquid used in the phase change method may be any solvent (non-solvent for the polymer component) that coagulates the polymer component, and is appropriately selected depending on the type of polymer used as the polymer component. Any solvent that coagulates an imide resin or polyamic acid may be used, for example, water; monohydric alcohols such as methanol and ethanol; alcohols such as polyhydric alcohols such as glycerin; water-soluble polymers such as polyethylene glycol; A water-soluble coagulating liquid such as a mixture can be used.

  The temperature of the coagulation liquid is not particularly limited, but may be 0 to 100 ° C., for example. When the temperature of the coagulation liquid is less than 0 ° C., the cleaning effect of a solvent or the like tends to be lowered. When the temperature of the coagulating liquid exceeds 100 ° C., the solvent and the coagulating liquid are volatilized and the working environment is impaired. As the coagulation liquid, water is preferably used from the viewpoints of cost, safety, toxicity and the like. When water is used as the coagulating liquid, a temperature of water of about 5 to 60 ° C. is appropriate. The immersion time in the coagulation liquid is not particularly limited, but a time for sufficiently washing the solvent and the water-soluble polymer may be appropriately selected. If the washing time is too short, the porous structure may be broken in the drying process due to the remaining solvent. If the cleaning time is too long, the production efficiency is lowered, leading to an increase in product cost. The cleaning time depends on the thickness of the porous film and the like and cannot be generally specified, but can be about 0.5 to 30 minutes.

  Before immersing the film-like material after casting in the coagulation liquid, the film-like material after casting is held in an atmosphere consisting of a relative humidity of 70 to 100% and a temperature of 15 to 100 ° C. for 0.2 to 15 minutes. Then, it is desirable to guide into the coagulation liquid. By placing the film-like material after casting under the humidification conditions described above, a highly homogeneous porous membrane can be easily obtained. When placed under humidification, it is considered that moisture penetrates from the surface of the film into the inside and promotes phase separation of the polymer solution efficiently. Preferred conditions are a relative humidity of 90 to 100% and a temperature of 30 to 80 ° C., and a more preferred condition is a relative humidity of about 100% (eg, 95 to 100%) and a temperature of 40 to 70 ° C. If the amount of moisture in the air is less than this, the porosity may not be sufficient.

  In the step of peeling the film-like porous layer from the base material, the film-like layer may be forcibly peeled from the base material, or a combination of a polymer component constituting the porous film and the base material When this is selected and immersed in the coagulation liquid, the film-like layer may be peeled off from the base material.

  Forcible peeling tends to make the thickness of the porous film uniform, but care must be taken since it may damage the porous film if pulled strongly.

  Although it is easier to produce the film when it is naturally peeled off, the thickness of the porous film tends to be slightly uneven. In order for the film-like porous layer and the base material to be naturally peeled when guided to the coagulation liquid, it is preferable to use a base material having high water repellency. For example, a fluorine film (for example, Teflon (registered trademark) film), a film obtained by bonding or coating a fluorine resin, or the like can be used.

  The peeled film-like porous layer is dried. The method for the drying treatment is not particularly limited, and may be a hot air treatment, a hot roll treatment, or a method of putting it in a thermostatic bath or an oven, as long as the film-like porous layer can be controlled to a predetermined temperature. The atmosphere during the drying process may be air, nitrogen or an inert gas. The use of air is the least expensive but may involve an oxidation reaction. In order to avoid this, nitrogen or an inert gas is preferably used, and nitrogen is preferable from the viewpoint of cost. The heating conditions are appropriately set in consideration of productivity, physical properties of the porous membrane, and the like.

  According to the above method, the porous membrane has a large number of micropores, the average pore diameter of the micropores is 0.01 to 10 μm, the porosity is 30 to 85%, and the thickness is 5 to 200 μm. Can be easily formed. As described above, the micropore diameter, porosity, and porosity of the porous membrane in the present invention are the types and amounts of the constituent components of the polymer solution, the amount of water used, the humidity during casting, the temperature, and the time. It is possible to adjust to a desired value by appropriately selecting and the like.

  The resulting porous membrane is subjected to a crosslinking treatment. The crosslinking agent contained in the porous membrane obtained as described above is usually in an unreacted state. However, when the crosslinking agent is thermally crosslinked, a crosslinked structure may be formed by the reaction of a part or all of the crosslinking agent depending on the drying treatment conditions.

  The crosslinking treatment can be performed by heat treatment and / or active energy ray irradiation (visible light, ultraviolet ray, electron beam, radiation, etc.) treatment depending on the kind of the crosslinking agent. Appropriate conditions should be set for each. For example, the heat treatment may be performed at 100 to 400 ° C. for 10 seconds to 5 hours.

  By performing the crosslinking treatment, the crosslinkable functional group in the polymer and the functional group of the crosslinking agent react to form a crosslinked structure in the porous film. By forming the crosslinked structure, a porous film excellent in film strength, heat resistance, chemical resistance, durability, and rigidity of the porous film can be obtained. Further, when various functional layers are formed on the surface of the porous layer, as shown in the following (b) or (c), crosslinking is caused during the formation of the functional layer (expression of functionality). By doing so, it is effective in improving the adhesion between the porous membrane and the functional layer.

When a functional layer is provided on the surface of the porous membrane (functionalization treatment) to obtain a functional laminate, there are several timings for performing the following crosslinking treatment.
(A) A method of obtaining a functional laminate by subjecting the obtained porous membrane to a crosslinking treatment and then providing a functional layer on the porous membrane surface.
(B) A method of providing a functional layered product by providing a functional layer on the surface of the obtained porous membrane and then performing a crosslinking treatment. The crosslinking treatment by heating may also serve as the heat treatment for expressing the function of the functional layer.
(C) The obtained porous membrane is subjected to a partial cross-linking treatment, and then a functional layer is provided on the surface of the porous membrane, and the cross-linking treatment is completed again by performing a cross-linking treatment again. The method obtained, here partial crosslinking treatment, is intended to be thereby semi-cured (so-called B-stage).

  Since the porous film is composed of a single layer of a porous layer, a shrinkage phenomenon may be observed when a crosslinking reaction occurs. In order to avoid this, it is preferable to perform the crosslinking reaction in a state where the porous membrane is appropriately fixed to the fixing member. For example, it is conceivable to fix a part of the porous membrane to a film, plate or the like made of resin, metal, glass or the like. Alternatively, fixing to the edge of a frame-like (frame-like) thing or something like a bat can be considered. As a fixing method, a method of sticking a part of the porous film with a single-sided tape or a double-sided tape, a method of sandwiching with a clip, a method of fixing with a screw, a method of piercing and fixing a pin, and the like are conceivable. At the time of industrial production, a pin tenter used when a polyamic acid is heated to produce a polyimide film can also be used. In addition, it is possible to control the structure such as thickness and porosity by appropriately controlling the shrinkage rate in the plane direction by fixing.

  The porous film of the present invention may be subjected to heat treatment or film formation treatment as necessary in order to impart desired characteristics.

  Although the chemical resistance of the porous membrane of the present invention is further improved by cross-linking, the porous membrane may be separately coated with a chemical resistant polymer compound.

  Here, the chemical is a known material that dissolves, swells, shrinks, and decomposes a resin that constitutes a conventional porous film to lower its function as a porous film. The specific examples of such chemicals are dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methyl. Strong polar solvents such as 2-pyrrolidone (NMP), 2-pyrrolidone, cyclohexanone, acetone, methyl acetate, ethyl acetate, ethyl lactate, acetonitrile, methylene chloride, chloroform, tetrachloroethane, tetrahydrofuran (THF); sodium hydroxide, Potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate Inorganic salts such as triethylamine; Alkaline solutions such as aqueous solutions and organic solvents in which alkalis such as ammonia are dissolved; Inorganic acids such as hydrogen chloride, sulfuric acid and nitric acid; Organic acids having carboxylic acids such as acetic acid and phthalic acid An aqueous solution in which an acid such as an acid is dissolved, an acidic solution such as an organic solvent, and a mixture thereof.

  The chemical resistant polymer compound is not particularly limited as long as it has excellent resistance to chemicals such as strong polar solvents, alkalis, acids, etc. For example, phenolic resin, xylene resin, urea resin, melamine Thermosetting resin such as resin, benzoguanamine resin, benzoxazine resin, alkyd resin, triazine resin, furan resin, unsaturated polyester, epoxy resin, silicon resin, polyurethane resin, polyimide resin, or light Curable resin: Thermoplastic resins such as polyvinyl alcohol, cellulose acetate resin, polypropylene resin, fluorine resin, phthalic acid resin, maleic acid resin, saturated polyester, ethylene-vinyl alcohol copolymer, chitin, chitosan, etc. Is mentioned. These polymer compounds can be used alone or in combination. The polymer compound may be a copolymer or a graft polymer.

  When the porous film is coated with such a chemical resistant polymer compound, the porous film dissolves or swells and deforms even when it comes into contact with the strong polar solvent, alkali, acid, or other chemicals. The alteration can be suppressed to such an extent that no alteration such as the occurrence of the occurrence occurs or the use purpose or the application is not affected. For example, in an application where the porous membrane and the chemical are in contact with each other for a short time, it is only necessary to provide chemical resistance that does not change within that time.

  In addition, since the said chemical-resistant polymer compound also has heat resistance in many cases, there is little possibility that the heat resistance of a porous membrane will fall. It is also possible to change the properties of the porous membrane surface by coating with a chemical resistant polymer compound. For example, if a fluororesin is used, the surface can be made water repellent, and if an ethylene-vinyl alcohol copolymer is used, the surface can be made hydrophilic. Furthermore, if a phenolic resin is used, the surface can be rendered water repellent with respect to neutral water and the surface can be rendered hydrophilic with respect to an alkaline aqueous solution. Thus, the affinity (hydrophilicity etc.) with respect to a liquid can be changed by selecting suitably the kind of high molecular compound used for coating | cover.

  Since the porous membrane of the present invention has the above configuration, it can be applied to various uses in a wide range of fields. Specifically, using the pore characteristics of the porous membrane as it is, for example, separation membranes in membrane separation technologies such as microfiltration, separation and concentration, low dielectric constant materials, battery separators, electrolytic capacitors, cushioning materials, It can be used as a wide range of substrate materials such as ink image-receiving sheets, insulating materials, heat insulating materials, and electrolyte membrane base materials. Furthermore, by making the surface of the porous membrane functional, it can be used as circuit boards, heat radiation materials (heat sinks, heat radiation plates), electromagnetic wave control materials such as electromagnetic wave shields and electromagnetic wave absorbers, antennas, cell culture substrates, etc. be able to.

  Examples of the battery separator include a lithium ion secondary battery separator. In separator applications for lithium ion secondary batteries, chemical resistance to various components contained in the electrolyte solution is required. Since the porous membrane of the present invention has enhanced chemical resistance by crosslinking, it can be preferably applied.

  The porous membrane of the present invention can also be used as an electrolyte membrane substrate for fuel cells. For example, Japanese Unexamined Patent Application Publication No. 2004-171994 discloses a method for producing an electrolyte membrane for a fuel cell using a porous membrane as a base material. By filling the porous membrane substrate with an electrolyte, an electrolyte membrane for a fuel cell can be obtained. The electrolyte membrane for fuel cells is required to have resistance to swelling against water and methanol in use, and when the electrolyte membrane substrate is filled with the electrolyte, the electrolyte or its precursor and the solvent dissolving them are used. Tolerance is required. In other words, a porous sheet having excellent chemical resistance is required, but at present, the porous sheet produced by the wet phase separation method often has insufficient chemical resistance to the solvent. Since the porous membrane of the present invention has enhanced chemical resistance by crosslinking, it can be preferably applied.

  Next, the functional laminate using the porous membrane of the present invention will be described. In the present invention, the functional laminate is composed of a conductor layer, a dielectric layer, a semiconductor layer, an insulator layer, and a resistor layer on the surface of the porous film or the polymer layer derived from the porous film. A functional laminate having a functional layer selected from the group consisting of the porous membrane and the polymer layer derived from the porous membrane has a crosslinked structure formed by the crosslinking agent. Such a functional laminate is sometimes referred to as “composite material” in the present specification.

  The formation of various functional layers or precursor layers thereof on the surface of the porous film described above can be performed by, for example, plating, printing technology, or the like.

  For example, the metal plating layer may be formed as a thin metal coating on the surface of the porous film. Examples of the metal constituting the metal plating layer include copper, nickel, silver, gold, tin, bismuth, zinc, aluminum, lead, chromium, iron, indium, cobalt, rhodium, platinum, palladium, and alloys thereof. be able to. In addition, nickel-phosphorus, nickel-copper-phosphorus, nickel-iron-phosphorus, nickel-tungsten-phosphorus, nickel-molybdenum-phosphorus, nickel-chromium-phosphorus, nickel-boron-phosphorus, and other elements other than metals. Also included are alloy films. The metal plating layer may be used alone or in combination of the above metals, may be a single layer, or a plurality of layers may be laminated.

  The material constituting the magnetic plating layer is not particularly limited as long as it has magnetism, and may be either a ferromagnetic material or a paramagnetic material. For example, nickel-cobalt, cobalt-iron-phosphorus, cobalt -Alloys such as tungsten-phosphorus, cobalt-nickel-manganese; compounds having sites capable of generating radicals such as methoxyacetonitrile polymers, metal complex compounds such as charge transfer complexes of decamethylferrocene, and carbon materials in the process of graphitization An organic magnetic material made of a compound such as polyacrylonitrile can be exemplified.

  For example, a known method such as electroless plating or electrolytic plating can be used to form the metal plating layer. In the present invention, electroless plating is preferably used from the viewpoint that the porous film is composed of a polymer component, and a combination of electroless plating and electrolytic plating can also be used.

  The plating solutions used for forming the metal plating layer are known in various compositions, and those sold by manufacturers can also be obtained. The composition of the plating solution is not particularly limited, and various requests (aesthetics, hardness, abrasion resistance, discoloration resistance, corrosion resistance, electrical conductivity, thermal conductivity, heat resistance, sliding property, water repellency, wettability) The soldering wettability, sealing properties, electromagnetic wave shielding characteristics, reflection characteristics, etc. may be selected.

  One embodiment of a method for producing a composite material includes a step of applying a photosensitive composition comprising a compound that generates a reactive group by light to the surface of the porous film of the present invention to provide a photosensitive layer, and a mask on the photosensitive layer. And reacting with light in the above production method; or a method of forming a conductive pattern by bonding a reactive group generated in the exposed portion with a metal; Using a compound that eliminates a reactive group by light instead of a compound that generates a group, and a step of eliminating the reactive group in the exposed portion, and a step of forming a conductor pattern by combining the reactive group remaining in the unexposed portion with a metal. Method.

  The compound that generates a reactive group by light is not particularly limited as long as it is a compound that generates a reactive group in a molecule that can form a bond with a metal (including a metal ion). For example, an onium salt derivative or a sulfonium ester And photosensitive compounds containing at least one derivative selected from derivatives, carboxylic acid derivatives and naphthoquinonediazide derivatives. These photosensitive compounds are versatile and can easily generate a reactive group capable of binding to a metal by light irradiation, so that a conductive portion having a fine pattern can be accurately formed.

  As a compound that loses a reactive group by light, for example, a compound having a reactive group capable of forming a bond with a metal (including a metal ion), and the reactive group generates a hydrophobic functional group by irradiation with light. And compounds that are difficult to dissolve or swell in water.

The reactive group generated or disappeared by the light is not particularly limited as long as it is a reactive group capable of forming a bond with the metal (including a metal ion), and examples thereof include a functional group capable of ion exchange with a metal ion. Preferably, a cation exchange group is used. The cation exchange group includes an acidic group such as a —COOX group, a —SO ₃ X group or a —PO ₃ X ₂ group (where X is a hydrogen atom, an alkali metal, an alkaline earth metal, or an ammonium group). ) Etc. are included. Among them, a cation exchange group having a pKa value of 7.2 or less is preferable because a bond with a sufficient metal per unit area can be formed, and desired conductivity can be easily obtained. Such a reactive group is subjected to metal ion exchange in the next step, and can exhibit a stable adsorption ability by a metal reductant or metal fine particles.

  The irradiation light is not particularly limited as long as the generation or disappearance of the reactive group can be promoted. For example, light having a wavelength of 280 nm or more can be used. However, in order to avoid deterioration due to exposure of the porous film, the wavelength is preferably 300 nm or more. (About 300 to 600 nm) In particular, light of 350 nm or more is preferably used.

  By irradiating with light through a mask and then washing as necessary, a pattern composed of reactive groups can be formed in the exposed or unexposed areas. In this way, the reactive group provided on the surface of the porous membrane is bonded to a metal by the method described below to form a conductor pattern.

  In the present invention, an electroless plating method is preferably used as a method for bonding the reactive group to the metal. Electroless plating is known to be useful as a method of laminating a metal on a resin layer generally formed of plastic or the like. The surface of the porous membrane may be subjected to treatments such as degreasing, washing, neutralization, and catalyst treatment in advance for the purpose of improving the adhesion with the metal. As the catalyst treatment, for example, a catalyst metal nucleation method in which a catalyst metal capable of promoting metal deposition is attached to the surface to be treated can be used. The catalytic metal nucleation method is a method of promoting chemical plating by contacting a colloidal solution containing a catalytic metal (salt) and then contacting an acid or alkali solution or a reducing agent (catalyzer (catalyst) -accelerator). Method): A method of forming a catalytic metal nucleus by contacting a colloidal solution containing fine particles of catalytic metal and then removing the solvent and additives by heating or the like (metal fine particle method); An acid or alkali solution containing a reducing agent And then contacting the catalyst metal with an acid or alkali solution and bringing the catalyst into contact with an activating liquid (sensitizing)-activating (activating) ) Method).

  As the catalyst metal (salt) -containing solution in the catalyzer-accelerator method, for example, a metal (salt) -containing solution such as a tin-palladium mixed solution or copper sulfate can be used. The catalyzer-accelerator method is, for example, by immersing the porous membrane laminate in an aqueous copper sulfate solution, washing and removing excess copper sulfate as necessary, and then immersing in an aqueous solution of sodium borohydride, Catalyst nuclei made of copper fine particles can be formed on the surface of the porous membrane. In the metal fine particle method, for example, a colloidal solution in which silver nanoparticles are dispersed is brought into contact with the surface of the porous film, and then heated to remove additives such as a surfactant and a binder, whereby the surface of the porous film is removed. Catalyst nuclei made of silver particles can be deposited. In the sensitizing-activating method, for example, after contacting with a hydrochloric acid solution of tin chloride, a catalyst nucleus made of palladium can be precipitated by contacting with a hydrochloric acid solution of palladium chloride. As a method of bringing the porous film into contact with these treatment liquids, a method of applying a metal plating layer on the porous film surface, a method of immersing the porous film in the treatment liquid, or the like can be used.

  Examples of main metals used for electroless plating include copper, nickel, silver, gold, nickel-phosphorus, and the like. The plating solution used for electroless plating contains, for example, the above metals or salts thereof, reducing agents such as formaldehyde, hydrazine, sodium hypophosphite, sodium borohydride, ascorbic acid, glyoxylic acid, acetic acid It contains complexing agents such as sodium, EDTA, tartaric acid, malic acid, citric acid, glycine, and precipitation control agents, and many of these are commercially available and can be easily obtained. Electroless plating is performed by immersing the porous film subjected to the above treatment in the above plating solution. In addition, electroless plating is performed only on the other surface by performing electroless plating in a state where a protective sheet is stuck on one surface of the porous film.

  The thickness of the metal plating layer is not particularly limited and can be appropriately selected depending on the application, and is, for example, about 0.01 to 20 μm, preferably about 0.1 to 10 μm. In order to efficiently increase the thickness of the metal plating layer, for example, a method of forming a metal plating layer by combining electroless plating and electrolytic plating may be performed. In other words, since the surface of the porous film on which the metal film is formed by electroless plating is imparted with conductivity, it is possible to obtain a thick metal plating layer in a short time by performing more efficient electrolytic plating. Become.

  The above method is particularly suitable as a method for obtaining a composite material used for a circuit board, a heat dissipation material, or an electromagnetic wave control material.

  Conventionally, circuit boards are manufactured by a method in which a copper foil is bonded to the surface of a substrate generally made of glass, epoxy resin, polyimide or the like, and wiring is formed by removing unnecessary portions of the copper foil by etching. It was. However, according to such a conventional method, it has become difficult to form fine wiring that can be used for a circuit board with a high density. In order to advance the miniaturization of wiring, it is necessary to attach a very thin copper foil strongly to a substrate made of glass, epoxy resin, polyimide, etc., but the thin copper foil is extremely inferior in handleability, The lamination process was very difficult. In addition, the manufacture of thin copper foils is difficult and expensive per se, and the glass / epoxy resin and polyimide used for the base material and the copper foil do not have a large adhesive force, so miniaturization is promoted. There was a problem that the wiring peeled off from the substrate.

  In such a background, according to the composite material of the present invention, it is also possible to form a fine opening on the surface of the porous film. In this case, sufficient adhesion with the metal plating layer can be ensured, and the fine wiring can be secured. It is suitable for the circuit board material which has. When constituting the circuit board material, the metal plating layer is preferably made of copper, nickel, silver or the like.

  The porous film of the present invention is extremely useful as a circuit board manufactured by a method of forming fine wiring directly on the surface of the porous film. As a method for producing such a circuit board, the method described as the method for producing a composite material of the present invention can be used. According to this method, since the porous film of the present invention is used, it is possible to form fine wiring that is firmly entangled with the porous film, and furthermore, it is possible to easily and accurately form wiring using an exposure technique. . Up to now, a method of forming a wiring by using an electroless plating method on a porous body has been known. However, the conventional porous body has poor strength and has a problem in that it is inferior in handleability and damaged during the manufacturing process. It was. On the other hand, when the porous film of the present invention is used, a sufficient strength can be ensured and a circuit board excellent in handleability can be provided.

  An electromagnetic wave control material is used as a material for shielding (shielding) or absorbing electromagnetic waves in order to reduce or suppress the influence on the surrounding electromagnetic environment and the influence of the device itself from the surrounding electromagnetic environment. There are many electromagnetic sources such as electric / electronic devices, wireless devices, systems, etc. around us, such as the spread of digital electronic devices, personal computers and mobile phones, and they emit various electromagnetic waves. Electromagnetic waves radiated from these devices may affect the surrounding electromagnetic environment, and the device itself is also affected by the surrounding electromagnetic environment. As countermeasures against these problems, electromagnetic wave control materials such as electromagnetic wave shielding materials and electromagnetic wave absorber materials have become important year after year. The composite material of the present invention can provide an electromagnetic wave shielding property by blocking electromagnetic waves by, for example, imparting conductivity by a metal plating layer. Therefore, it is extremely useful as an excellent electromagnetic wave control material.

  The metal plating layer constituting the electromagnetic wave control material is preferably one that can impart conductivity, and for example, it is effective to be formed of nickel, copper, silver, or the like. Further, when the composite material has a layer structure in which a magnetic plating layer is formed on the surface of the porous film by electroless plating, it is useful as an electromagnetic wave absorber material. Examples of the material used for forming the magnetic plating layer by electroless plating include magnetic materials such as alloys of nickel, nickel-cobalt, cobalt-iron-phosphorus, cobalt-tungsten-phosphorus, cobalt-nickel-manganese, and the like. Can be mentioned. The composite material of the present invention is very thin and highly flexible, and since the metal or magnetic material formed by plating is entangled with the porous film, the plating layer is difficult to peel off, and bending resistance (fold resistance) Sex) can be improved. Such a composite material can be used by being installed or affixed in any place of an electronic device.

  The porous film of the present invention is also useful as a low dielectric constant material. With the advent of the broadband era, it is necessary to transmit a large amount of information at high speed. For this reason, the frequency used in electronic devices is also increasing, and the electronic components used therein must also support high-frequency signals. When conventional wiring boards (mainly glass epoxy resin) are used for high frequency circuits, (1) transmission signal delay due to high dielectric constant, (2) signal interference / attenuation due to high dielectric loss, power consumption Problems such as an increase and heat generation in the circuit occur. A porous material is considered useful as a high-frequency wiring board material for solving these problems. This is because the relative dielectric constant of air is as low as 1, whereas a porous material can achieve a low relative dielectric constant. For this reason, a porous substrate material has been conventionally required. However, in order to achieve a low dielectric constant, it is necessary to increase the porosity, resulting in a problem that the strength as a substrate is reduced. It was. The porous film of the present invention not only has a low dielectric constant characteristic but also can ensure a sufficient strength for handling the porous film, and is a preferable medium as a low dielectric constant material.

  When the porous film of the present invention is used as a low dielectric constant circuit board material, as described above, a copper foil is bonded to the surface of the porous film, and wiring is removed by removing unnecessary portions of the copper foil by etching. It is conceivable to manufacture by a forming method. Although miniaturization and high density of wiring are becoming difficult, most circuit boards are still made by this conventional method, and the porous film of the present invention can also be used by this method. It can be said that this is a useful material that can cope with the reduction of the dielectric constant of the substrate, which has become very demanding. When using a porous film with low micropore connectivity, when etching the copper foil, the etching solution is difficult to enter the porous film, and undesirable etching from the back side of the copper foil does not occur easily. It is possible to take advantage of the characteristics of a low independent porous membrane.

  As one form of the method for producing a composite material of the present invention, a method using a printing technique is exemplified. Since the porous film of the present invention is excellent in printing characteristics, it can be used by forming a pattern on the porous film by printing. Since it is also used as an ink image receiving sheet (printing medium) in this way, the printing technique will be described in detail next.

  Ink image-receiving sheets, also called print media, are often used in printing technology. On the other hand, many printing methods are currently put into practical use and used. For example, inkjet printing, screen printing, dispenser printing, letterpress printing (flexographic printing), sublimation printing, offset printing, laser, etc. Examples include printer printing (toner printing), intaglio printing (gravure printing), contact printing, and microcontact printing. The constituent components of the ink used are not particularly limited, and examples thereof include conductors, dielectrics, semiconductors, insulators, resistors, dyes, and the like.

  Advantages of creating electronic materials by printing methods are: (1) can be manufactured with a simple process, (2) is a low environmental impact process with little waste, (3) can be manufactured in a short time with low energy consumption, ( 4) Although the initial investment can be significantly reduced, it is also true that high-definition printing is required, which is unprecedented and technically difficult. Therefore, especially for printing used for manufacturing electronic materials, not only the performance of the printing machine but also the characteristics of the ink and the ink image-receiving sheet have a great influence on the printing result. The fine porous structure of the porous membrane of the present invention can be closely adhered to the printing plate due to its cushioning properties, and can absorb ink or fix ink precisely, so far. High-definition printing that is not possible with the above can be achieved, and it is very preferably used. Moreover, sufficient strength for handling the porous membrane can be ensured. For example, continuous printing can be performed by roll-to-roll, and the production efficiency can be remarkably improved.

  When the electronic material is manufactured by printing, the above-described method can be used as a printing method. Specific examples of electronic materials produced by printing include electromagnetic wave control materials such as electromagnetic wave shields and electromagnetic wave absorbers, circuit boards, antennas, heat sinks, and the like. More specifically, liquid crystal displays, organic EL displays, Field emission display (FED), IC card, IC tag, solar cell, LED element, organic transistor, capacitor (capacitor), electronic paper, flexible battery, flexible sensor, membrane switch, touch panel, EMI shield and the like can be mentioned.

  The method for producing the electronic material includes a step of printing on the surface of the porous film (substrate) an ink containing an electronic material such as a conductor, a dielectric, a semiconductor, an insulator, or a resistor. For example, a capacitor (capacitor) can be formed by printing on the surface of the porous film (substrate) with ink containing a dielectric. Examples of such a dielectric material include barium titanate and strontium titanate. A transistor or the like can be formed by printing with an ink containing a semiconductor. As the semiconductor, pentacene, liquid silicon, fluorene-bithiophene copolymer (F8T2), poly (3-hexylthiophene) (P3HT), and the like can be given.

  Since wiring can be formed by printing with ink containing a conductor, a flexible substrate, a TAB substrate, an antenna, or the like can be manufactured. Examples of the conductor include conductive inorganic particles such as silver, gold, copper, nickel, ITO, carbon, and carbon nanotube; and particles made of conductive organic polymers such as polyaniline, polythiophene, polyacetylene, and polypyrrole. Can do. Examples of the polythiophene include poly (ethylenedioxythiophene) (PEDOT). These can be used as a solution or a colloidal ink. Among these, conductor particles made of inorganic particles are preferable, and silver particles and copper particles are particularly preferably used from the viewpoint of balance of electrical characteristics and cost. Examples of the shape of the particles include a spherical shape and a scale shape (flakes). The particle size is not particularly limited, but so-called nanoparticles having an average particle diameter of about several μm to several nanometers can also be used. These particles can be used by mixing a plurality of types. As a conductive ink, a silver ink (silver paste) that can be easily obtained will be described as an example. However, the present invention is not limited to this, and other types of ink can also be applied.

  Silver ink generally contains silver particles, a surfactant, a binder, a solvent, and the like as components. As another example, utilizing the property that silver oxide is reduced by heating, an ink containing silver oxide particles is printed and then heated and reduced to form a silver wiring. As yet another example, there is an ink that contains an organic silver compound and is then thermally decomposed to form a silver wiring. Organic silver compounds that can be dissolved in a solvent can also be used. As particles constituting the silver ink, silver particles, silver oxide, organic silver compounds and the like may be used singly or in combination, and those having different particle diameters may be used in combination. The temperature (baking temperature) at which the ink is cured after printing with the silver ink can be appropriately selected according to the composition of the ink, the particle diameter, etc., but is usually in the range of about 100 to 300 ° C. Many. Since the porous film of the present invention is an organic material, the firing temperature is preferably relatively low in order to avoid deterioration, but in order to reduce the electrical resistance of the wiring, it is generally preferably fired at a high temperature, It is necessary to select and use an ink having an appropriate curing temperature. As commercial products of such silver ink, trade name “CA-2503” manufactured by Daiken Chemical Industry Co., Ltd., trade name “Nano-Dotite XA9053” manufactured by Fujikura Kasei Co., Ltd., manufactured by Harima Kasei Co., Ltd. Trade names “NPS”, “NPS-J” (average particle diameter of about 5 nm), and trade names “Finesphere SVW102” (average particle diameter of about 30 nm) manufactured by Nippon Paint Co., Ltd. are known. In consideration of the balance between the electrical resistance required for the wiring board and the wiring adhesion, it is preferable to select the particle size, particle size distribution, and mixing ratio of the conductor added to the ink.

  In the case of screen printing, if the viscosity is too low, it is difficult to retain the ink on the screen, so it is preferable that the viscosity is rather high, and there is no particular problem even if the particle size of the particles contained in the ink is large. When is small, it is preferable to reduce the amount of solvent. Therefore, the particle diameter is preferably about 0.01 to 10 μm.

  The wiring may be formed only on one side of the porous film, or may be formed on both sides thereof. When wiring is formed on both sides, a via that connects the wirings on both sides can be formed as necessary. The via hole may be formed by a drill or a laser. The conductor in the via hole may be formed by a conductive paste or may be formed by plating.

  Further, the surface of the wiring formed of conductive ink can be used by being coated with plating or an insulator. In particular, it has been pointed out that silver wiring tends to cause electromigration and ion migration when compared with copper wiring (Nikkei Electronics, 2002.2.67, page 75). Therefore, for the purpose of improving the reliability of the wiring, it is effective to cover the wiring surface formed of silver ink with plating. Examples of plating include copper plating, gold plating, and nickel plating. Plating can be performed by a known method.

  Furthermore, the surface of the wiring formed of conductive ink can be covered with a resin. The above configuration can be suitably used for purposes such as wiring protection, wiring insulation, wiring oxidation and migration prevention, and flexibility improvement. For example, there is a possibility that the silver wiring becomes silver oxide by oxidation and the copper wiring becomes copper oxide, and the conductivity may decrease. However, by covering the wiring surface with the resin, the wiring comes into contact with oxygen or moisture. Can be avoided, and a decrease in conductivity can be suppressed. Examples of the method for selectively coating the surface of the wiring with a resin include methods such as dropper, dispenser, screen printing, and inkjet using a curable resin or a soluble resin described later as the resin to be coated.

  When the pores of the porous film are maintained after the wiring is formed, the porous film portion has a low dielectric constant, and therefore is preferably used as a high-frequency wiring board.

  As the use of the porous membrane laminate of the present invention, the porous membrane laminate of the present invention is used in addition to the porous membrane laminate of the present invention in addition to the case where the pores of the porous membrane are left as they are. It is also conceivable to use it by losing it.

  When the wiring surface is covered with a resin, if the porous film is composed of independent micropores with low communication, the resin does not easily enter the pores, so that the pore structure tends to be maintained. On the contrary, when the porous film is composed of fine pores having communication properties, the resin easily enters the pores, so that the pores are filled with the resin and the pore structure tends to disappear.

  Although it does not specifically limit as resin which coat | covers wiring, For example, the curable resin used without a solvent, the soluble resin utilized by melt | dissolving in a solvent, etc. are mentioned. When using a soluble resin, it is necessary to coat in consideration of the volume reduction when the solvent volatilizes.

  Examples of the curable resin include an epoxy resin, an oxetane resin, an acrylic resin, and a vinyl ether resin.

  Epoxy resins include bisphenol A type and bisphenol F type bisphenol type, novolak type glycidyl ether type epoxy resins such as phenol novolak type and cresol novolak type; alicyclic epoxy resins and their modified resins Resin is included. Commercially available epoxy resins include “Araldite” from Huntsman Advanced Materials, “Denacol” from Nagase ChemteX, “Celoxide” from Daicel Chemical Industries, “Epototo” from Toto Kasei Co., Ltd., etc. The cured epoxy resin can be obtained, for example, by a method in which a curing reaction is started by a curable resin composition obtained by mixing a curing agent with an epoxy resin and the reaction is accelerated by heating. As the curing agent for the epoxy resin, for example, organic polyamine, organic acid, organic acid anhydride, phenols, polyamide resin, isocyanate, dicyandiamide and the like can be used.

  The cured epoxy resin is obtained by a method in which a curing reaction is initiated by heating or irradiation with light such as ultraviolet rays to a curable resin composition obtained by mixing a curing catalyst called a latent curing agent with an epoxy resin. You can also. As the latent curing agent, commercially available products such as “Sun-Aid SI” manufactured by Sanshin Chemical Industry Co., Ltd. can be used.

  If a highly flexible thing is used as a cured epoxy resin, it can be made flexible like a flexible substrate. Moreover, when heat resistance and high dimensional stability are requested | required, it can also be used as a rigid board | substrate (hard board | substrate) by using the composition which becomes hard after hardening as a curable resin composition.

  When an epoxy resin is used for coating, the curable resin composition is easy to handle if it has a low viscosity. Examples of such a characteristic include a bisphenol F-based composition and an aliphatic polyglycidyl ether-based composition.

  Examples of the oxetane resin include “Aron Oxetane” manufactured by Toagosei Co., Ltd. The cured oxetane resin can be obtained by mixing the oxetane resin with, for example, a cationic photopolymerization initiator “IRGACURE 250” manufactured by Ciba Specialty Chemicals, and starting the curing reaction by irradiating with ultraviolet rays. it can.

  Soluble resins include low dielectric resin “Oligo-Phenylene Ether” manufactured by Mitsubishi Gas Chemical Co., Ltd., polyamideimide resin “Vilomax” manufactured by Toyobo Co., Ltd., polyimide ink “Iupicoat” manufactured by Ube Industries, Ltd. Polyimide ink “Evereck” manufactured by NI Material, polyimide ink “ULIN COAT” manufactured by NI Material Co., Ltd., polyimide ink “Q-PILON” manufactured by PI Engineering Laboratory, saturated polyester resin “Nichigo Polyester” manufactured by Nippon Synthetic Chemical Co., Ltd. Commercially available products such as an acrylic solvent-type pressure-sensitive adhesive “Coponil” and an ultraviolet / electron beam curable resin “Shikou” can be used.

  As a solvent for dissolving the soluble resin used at the time of coating, it can be appropriately selected from known organic solvents according to the kind of the resin. A typical example of a resin solution (soluble resin solution) in which a soluble resin is dissolved in a solvent is, for example, a resin solution in which “oligo-phenylene ether” is dissolved in a general-purpose solvent such as methyl ethyl ketone or toluene; A resin solution (trade name “HR15ET”) dissolved in an ethanol / toluene mixed solvent; a resin solution in which “Iupicoat” is dissolved in triglyme can be used.

  The method of coating the wiring with the resin is not particularly limited, but the curable resin composition or the soluble resin solution described above is spread on the surface of the porous film by using means such as a dropper, a spoon, a dispenser, screen printing, and ink jet. (Applying) and, if necessary, a method of removing excess resin with a spatula or the like can be used. Examples of the spatula include fluorine resins such as polypropylene and Teflon (registered trademark), rubbers such as silicone rubber, resins such as polyphenylene sulfide, and metals such as stainless steel. Among these, a resin spatula is preferably used because it hardly damages the wiring and the porous film. In addition, a method of dropping an appropriate amount onto the surface of the porous film using a means capable of controlling the discharge amount such as a dropper, a dispenser, screen printing, and ink jet without using a spatula or the like is also possible.

  In order to smoothly spread the resin on the surface of the porous membrane, an uncured resin having a low viscosity is preferably used. In addition, it is possible to improve the handleability of a resin having a high viscosity by lowering the viscosity using means such as heating at an appropriate temperature. However, when a curable resin is used, the curing reaction rate is increased by heating, so that heating more than necessary is not preferable because workability deteriorates.

  After the resin component is spread on the surface of the porous membrane, it is preferable to perform heat treatment for the purpose of accelerating the curing of the resin or volatilizing the solvent. The heating method is not particularly limited, but rapid heating is preferably a method in which the temperature is gently raised because there is a possibility that unevenness may occur due to volatilization of the resin or curing agent or volatilization of the solvent. The temperature increase may be either continuous or sequential. It is preferable to appropriately adjust the temperature and time for curing and drying depending on the type of resin and solvent.

  In the present invention, in addition to the case where the porous structure of the porous membrane is maintained, the composite material has a porous layer void after the functional layer is formed on the surface of the porous membrane (after functionalization). The case where the pore structure is eliminated by solvent treatment, for example, and the porous membrane is preferably transparent is also included.

  In the present invention, the composite material may have a structure in which the pores of the porous film are left as they are. The composite material in which the pores of the porous membrane are left as it is means that the porous membrane has characteristics as a porous body. Specifically, for example, the composite material is a printing technology. This means that the same pore structure as that of the porous film at the time when the conductor is formed is retained. Such a composite material may have a configuration in which other layers are laminated or various treatments are performed as long as the porous film can maintain the characteristics as a porous body.

  For example, when leaving the pores of the porous film as they are for reducing the dielectric constant, the solvent treatment is not performed. However, in order to protect the wiring, insulate the wiring, prevent the wiring from being oxidized, and improve the flexibility, only the wiring portion may be covered with a resin by the above-described method.

  The porous membrane laminate of the present invention can be used for an antenna having more excellent high frequency characteristics.

  Recently, many wireless devices are used, and an antenna is required for transmitting and receiving signals. The spread of mobile phones, wireless LANs, IC cards, etc. is remarkable. Use of a low dielectric constant material for the antenna is preferable because it can increase the antenna gain. For example, a loop-shaped RFID antenna is used for an IC card or the like, and these are currently made by a subtractive method (etching method).

  By replacing a conventionally used PET substrate or the like with the porous film of the present invention, an antenna with higher frequency characteristics can be manufactured. As a manufacturing method, a subtractive method can be used. Specifically, in the same manner as shown in the method for producing a low dielectric constant circuit board, a copper foil is bonded to the surface of a porous film based on a resin film, and after forming a resist pattern, etching of the copper foil is performed. This can be done by removing unnecessary portions. Another method can be performed by forming a resist pattern on a porous film having a metal foil such as copper as a base material, and then etching to remove unnecessary portions of the copper foil. And the conventional subtractive method is a method which requires a long process and requires labor and cost. As described in the ink image-receiving sheet, when an antenna is formed by printing with ink containing a conductor, it can be manufactured more easily and at low cost.

  Japanese Unexamined Patent Application Publication No. 2006-237322 discloses a method for producing a copper polyimide substrate. A method for producing a copper polyimide substrate comprising hydrophilizing a surface of a polyimide resin film, providing a physical development nucleus layer, forming a silver film by a silver diffusion transfer method, and then copper plating. Since the polyimide resin film does not have good adhesion, alkali treatment or corona discharge treatment is required for surface modification. However, in the porous film of the present invention, the adhesive formed on the porous film can enter the pores, and stronger adhesion can be expected due to the anchor effect. Therefore, the porous membrane can be preferably used for the above-mentioned use.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. First, each measurement method will be described.

  The average pore diameter and porosity of the porous membrane were calculated by the following method. These average pore diameter and porosity are obtained only for the micropores visible in the electron micrograph.

1. Average pore diameter From the electron micrograph, the area of any 30 or more holes on the surface or cross section of the laminate was measured, and the average value was defined as the average pore area Save. Assuming that the hole is a perfect circle, the value converted from the average hole area to the hole diameter using the following formula was defined as the average hole diameter. Here, π represents a circumference ratio.
Surface or internal average pore diameter [μm] = 2 × (Save / π) ^1/2

2. Porosity The porosity inside the porous membrane was calculated from the following formula. V is the volume of the porous membrane [cm ³ ], W is the weight of the porous membrane [g], ρ is the density of the porous membrane composition [g / cm ³ ] (where the density of the porous membrane composition is , Calculated by dividing the density of each component constituting the composition by weight composition ratio). The volume V of the porous membrane and the weight W of the porous membrane were calculated by subtracting the volume or weight of the substrate from the volume or weight of the laminate in which the porous membrane was laminated on the substrate, respectively.
Porosity [%] = 100-100 × W / (ρ · V)

3. Chemical resistance evaluation test I (Porous membrane solubility in NMP)
A chemical resistance test I (solubility of the porous membrane in NMP) for each of the porous membranes before and after the heat crosslinking treatment was performed as follows.
A porous membrane sample was cut into a size of about 40 mm × 30 mm, and 1 drop (about 26 mg) of N-methyl-2-pyrrolidone (NMP) was dropped on the porous membrane using a dropper. After 2 minutes, the sample was immersed in a large amount of water (about 1 liter) and stirred to wash NMP. Then, the sample was taken out and naturally dried at room temperature on a waste cloth. After drying, the state of the sample was visually observed.

4). Chemical resistance evaluation test II (Measurement of dimensional change rate of porous membrane)
The chemical resistance test II (measurement of the dimensional change rate of the porous membrane) for each of the porous membranes before and after the heat crosslinking treatment was performed as follows.
Referring to FIG. 1, a porous membrane sample was cut into a size of 30 mm × 20 mm (1). In the cut sample (1), three small holes are made so as to form a vertex of a right triangle whose length of each side is in the range of 8 to 30 mm, and the distances a, b, c between the three points are set. By measuring, the dimensional change of the porous membrane was measured.

First, the distances a ₁ , b ₁ , and c ₁ of the cut sample (1) were measured (initial distance).
Next, about 50 cc of solvent tetrahydrofuran (THF) was put into a petri dish having a diameter of about 100 mm, and sample (1) was put therein. Two minutes after immersion, the sample (1) was taken out, the sample (1) was sandwiched between two upper and lower glass slides so as not to dry, and the distances a ₂ , b ₂ and c ₂ were measured in the sandwiched state (after immersion) Distance). Next, the sample (1) was taken out of the slide glass, allowed to stand at room temperature for 10 minutes and naturally dried, and the distances a ₃ , b ₃ and c ₃ after drying were measured (distance after immersion drying). The change rate of each of a, b, and c was calculated using the following formula.

Change rate of a after immersion in THF (%) = [(a ₂ −a ₁ ) / a ₁ ] × 100
Change rate of a after immersion in THF (%) = [(a ₃ −a ₁ ) / a ₁ ] × 100

The rate of change of b (b ₁ , b ₂ , b ₃ ) and c (c ₁ , c ₂ , c ₃ ) was also calculated by the same method.
A change rate value of + indicates that the porous membrane sample (1) has expanded (swelled), and a change rate of-indicates that it has shrunk.

5). Air permeability test The air permeability was measured according to JIS P8117 using a Gurley type densometer type B manufactured by Tester Sangyo Co., Ltd. The number of seconds was measured with a digital auto counter. The larger the value of the air permeability (Gurley value), the lower the air permeability, that is, the lower the pore permeability in the porous membrane. If the Gurley value is 30 seconds / 100 cc or more, it can be determined that the connectivity of the micropores is low. For comparison, a 93 μm thick plain paper (“Ozone 100 recycled PPC paper” manufactured by Kokusai Pulp & Paper Co., Ltd.) was measured for air permeability under the same conditions. The Gurley value was 27 seconds / 100 cc. Met.

[Example 1]
As a base material for producing a porous film, an easy adhesion surface of a polyethylene terephthalate (PET) film (manufactured by Teijin DuPont, HS74AS type, thickness 100 μm) was used.

  Polyamideimide resin (trade name “Torlon AI-10” manufactured by Solvay Advanced Polymers), N-methyl-2-pyrrolidone (NMP) as a solvent, and phenol novolac type epoxy resin (Japan Epoxy Resin Co., Ltd.) as a crosslinking agent (Trade name “jER 152”) manufactured by the manufacture was mixed at a ratio in which the weight ratio of polyamideimide resin / NMP / phenol novolac epoxy resin was 25/75/5 to obtain a stock solution for film formation. A PET film substrate (made by Teijin DuPont, HS74AS type, thickness 100 μm) is fixed on a glass plate with tape so that the easy adhesion surface of the PET film is on the outside, and this undiluted solution at 25 ° C. is used with a film applicator Then, the film was cast under the condition of a gap of 38 μm between the film applicator and the substrate. Immediately after casting, it was kept in a container having a humidity of about 100% and a temperature of 50 ° C. for 4 minutes. Then, when it was immersed in water and solidified, the porous layer peeled from the base material naturally. Then, the membrane A which consists only of a porous layer was obtained by air-drying at room temperature. The thickness of the obtained film A composed of only the porous layer was about 27 μm.

  When this porous film A was observed with an electron microscope, there was a tendency that a skin layer was basically formed on the surface of the porous film, the inside of the porous film was almost homogeneous, and the average pore diameter was about 1 over the entire region. There were 0.0 μm independent micropores. The porosity inside the porous membrane was 75%.

[Example 2]
Polyamideimide resin solution (trade name “Vilomax N-100H” manufactured by Toyobo Co., Ltd .; solid content concentration 20% by weight, solvent NMP, solution viscosity 350 dPa · s / 25 ° C.), NMP as solvent, water-soluble polymer Polyvinylpyrrolidone K-15 (average molecular weight of about 10,000) and a bisphenol A type epoxy resin (trade name “jER 828” manufactured by Japan Epoxy Resin Co., Ltd.) as a crosslinking agent were used as polyamideimide resin / NMP / polyvinylpyrrolidone / A bisphenol A type epoxy resin was mixed at a ratio of 15/85/25/5 to obtain a stock solution for film formation. A PET film substrate (made by Teijin DuPont, HS74AS type, thickness 100 μm) is fixed on a glass plate with tape so that the easy adhesion surface of the PET film is on the outside, and this undiluted solution at 25 ° C. is used with a film applicator Then, the film was cast under conditions of a gap of 51 μm between the film applicator and the substrate. Immediately after casting, it was kept in a container having a humidity of about 100% and a temperature of 50 ° C. for 4 minutes. Then, when it was immersed in water and solidified, the porous layer peeled from the base material naturally. Then, the membrane B which consists only of a porous layer was obtained by air-drying at room temperature. The thickness of the obtained film B consisting only of the porous layer was about 36 μm.

  When this porous membrane B was observed with an electron microscope, the inside of the porous membrane was almost homogeneous, and there existed micropores having connectivity with an average pore diameter of about 0.3 μm over the entire area. The porosity inside the porous membrane was 70%.

[Heat-crosslinking treatment of porous membrane]
The porous membrane samples A and B obtained in Examples 1 and 2, respectively, were subjected to heat crosslinking treatment as follows.

  Each porous membrane sample was heated on a hot plate under the heating conditions (temperature, time) shown in Table 1. In order to heat the entire sample uniformly, the sample was heated with an aluminum vat about 20 mm deep from the top.

  Table 1 shows the measurement results of the porous membrane thickness (μm), chemical resistance evaluation test I (solubility of the porous membrane in NMP), and air permeability before and after the heat crosslinking treatment for each porous membrane sample. . Furthermore, Table 2 shows the measurement results of the chemical resistance evaluation test II (measurement of the dimensional change rate of the porous membrane) before and after the heat treatment for the porous membrane sample B.

From Table 1, about the porous membrane samples A and B, the chemical resistance with respect to NMP improved remarkably after heat processing compared with before heat processing. In the chemical resistance evaluation I of Table 1, “dissolved” indicates that the sample in the portion where NMP was dropped was dissolved. “With traces” indicates that the traces were observed in the portion where NMP was dropped.
For the porous membrane sample A, the air permeability was 4000 seconds or more (second measurement limit) before and after the heat treatment. It was confirmed that the characteristic that the connectivity of the micropores in the porous membrane A was low was maintained.
For the porous membrane sample B, the air permeability before the heat treatment changed slightly from 76 seconds to the air permeability after the heat treatment of 48 seconds. This slight change in air permeability indicates that the degree of connectivity of the micropores in the porous membrane B is maintained.

  From Table 2, the chemical resistance with respect to THF was remarkably improved after the heat treatment for the porous membrane sample B after the heat treatment. In the sample before the heat treatment, swelling was observed at the time of immersion in THF, and after drying, the deformation of the film itself was so severe that measurement on a flat surface was impossible. In the sample after the heat treatment, swelling during immersion in THF and shrinkage during drying after immersion in THF were not observed. Thus, in the porous membrane, it was confirmed that the cross-linking between the polymer having a crosslinkable functional group and the cross-linking agent is very effective in improving the membrane strength and chemical resistance of the porous membrane. It was done.

Claims (10)

A porous membrane having a large number of micropores,
The porous membrane is composed of a composition comprising a polymer having a crosslinkable functional group as a main component and a crosslinker capable of undergoing a crosslinking reaction with the crosslinkable functional group,
A porous film having an average pore diameter of 0.01 to 10 μm and a porosity of 30 to 85% in the porous film.   The crosslinkable functional group contained in the polymer is at least one selected from the group consisting of an amide group, a carboxy group, an amino group, an isocyanate group, a hydroxyl group, an epoxy group, an aldehyde group, and an acid anhydride group. The porous membrane according to claim 1.   The porous film according to claim 1 or 2, wherein the polymer is at least one selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyamide resin, and a polyetherimide resin.   The said crosslinking agent is at least 1 sort (s) chosen from the group which consists of a compound containing 2 or more epoxy groups, a polyisocyanate compound, and a silane coupling agent in any one of Claims 1-3. The porous membrane as described.   The porous membrane according to any one of claims 1 to 4, wherein the porous membrane has a thickness of 5 to 200 µm.   The porous membrane is obtained by casting a solution of a porous membrane forming material containing the polymer and the cross-linking agent that constitute the porous membrane on a base material, and then coagulating it. It is formed by immersing in a liquid, peeling the film-like porous layer from the substrate, and then subjecting the film-like porous layer to drying. 2. The porous membrane according to item 1.   The porous film according to any one of claims 1 to 6, wherein the cross-linking agent contained in the porous film is in an unreacted state.   The porous film according to claim 1, wherein a cross-linked structure is formed by the cross-linking agent. A method for producing the porous membrane according to any one of claims 1 to 8,
A solution of a porous film forming material containing the polymer and the cross-linking agent that constitute the porous film is cast into a film on a base material, and then immersed in a coagulation liquid. A method for producing a porous membrane, comprising peeling the film-like porous layer from the substrate and then subjecting the film-like porous layer to drying.   After casting the solution of the material for forming a porous film in the form of a film on the substrate, it is kept in an atmosphere of a relative humidity of 70 to 100% and a temperature of 15 to 100 ° C. for 0.2 to 15 minutes, The method for producing a porous membrane according to claim 9, wherein the porous membrane is immersed in a coagulating liquid.

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