JP5736186B2 - Porous membrane containing inorganic particles and method for producing the same - Google Patents

Description

  The present invention includes a porous film containing inorganic particles functionalized with inorganic particles and having pore characteristics of a porous film, and a method for producing the same, a laminate including the porous film, and a method for producing the same, The present invention relates to a functional laminate including a porous film or a laminate. The porous film of the present invention is, for example, an electronic paper display device (film for electronic paper), a photoelectrode such as a dye-sensitized solar cell, a photocatalyst, a circuit board, a heat dissipation material (heat sink, heat dissipation plate), an electromagnetic wave shield, It can be used for an electromagnetic wave control material such as an electromagnetic wave absorber, an antenna, a reflection sheet (a reflection sheet used for a backlight light source of a liquid crystal display or a display body), and the like.

  In recent years, in the United States and other countries, electronic books are entering a full-fledged period due to attractive electronic book terminals and abundant contents. Electronic paper and liquid crystal panels are used for this electronic book. Electronic paper is easy to read like paper, is thin and lightweight, features ultra-low power consumption, and can rewrite characters and image display. Since the whitened part of the electronic paper reflects sunlight and indoor illumination light, and the text and images are displayed in the blackened part, it is gentle to the human eye like printed matter, and for a long time. I'm never tired of reading the letters. On the other hand, liquid crystal screens of mobile phones and the like always emit light, and it is said that eyes are tired when used for a long time. Thus, in electronic paper, visibility equal to that of paper is one of the research and development goals where the highest priority is given. For this purpose, it is very important to increase the reflectance. Of the various electronic paper systems, the most popular microcapsule electrophoresis system has a reflectivity of about 35%, which is lower than 50-60% of newspaper, and is not always sufficient at present. It can be said that increasing the reflectance leads to an increase in visibility and is preferable.

  On the other hand, in the hope of expanding the use of renewable energy, there is an expectation for solar cells that use inexhaustible sunlight, and the market continues to expand. However, crystalline silicon solar cells, which account for more than 90% of the current global market, are concerned about the stable supply of high-purity silicon raw materials. In these circumstances, attention has been focused on dye-sensitized solar cells. Cost reduction can be expected and the market is expected to expand into new fields due to its colorfulness. In dye-sensitized solar cells, a porous titanium oxide film is often used as a photoelectrode. The titanium oxide porous film is formed by applying a titanium oxide paste on a transparent electrode and drying the solvent, but there are problems in adhesion and cracking.

  Recently, several proposals for functional porous membranes containing inorganic particles have been made. International Publication WO2006 / 006340 pamphlet describes a water treatment film comprising a porous film of vinylidene fluoride resin in which 0.01 to 5 parts by weight of photocatalytic titanium oxide is dispersed in 100 parts by weight of vinylidene fluoride resin. Is disclosed. JP 2009-179698 A discloses a composition containing a specific amount of polyolefin and inert fine particles and containing a specific amount of a volatile solvent. After cooling and cooling, the solvent is dried and removed. A method for producing a porous film containing inert fine particles by stretching and a reflective sheet using the porous film obtained by the method are described. However, a porous film containing these inorganic particles is still not sufficient in terms of functionality.

International Publication WO2006 / 006340 Pamphlet JP 2009-179698 A

  An object of the present invention is to provide an inorganic fine particle-containing porous membrane that can express new or high functionality by combining other materials that contain inorganic particles in an organic porous membrane.

  As a result of intensive studies to achieve the above object, the inventors of the present invention cast a dispersion liquid containing a polymer and inorganic particles to form a porous film on a substrate in the form of a film, and solidify it. A highly functional porous material in which inorganic particles are uniformly dispersed in the polymer by being immersed in a liquid and dried, and having an average pore diameter of 0.01 to 10 μm and a porosity of 30 to 85%. The inventors found that a film was obtained and completed the present invention.

That is, the present invention is a porous film having a large number of micropores, and the porous film is composed of a composition containing a polymer and inorganic particles, and the polymer includes a polyamide-imide resin, a poly It is at least one selected from the group consisting of etherimide resins, polyethersulfone resins, cellulose resins and polysulfone resins, and the average pore diameter of the micropores in the porous membrane is 0.01 to 10 μm, the porosity There was 30% to 85%, air permeability indicating the communication of the micropores, Ri 0.2-30 sec / 100 cc der Gurley value for the film thickness 30 [mu] m, the inorganic particles are titanium oxide particles, silica particles , Alumina particles, barium titanate particles, barium sulfate particles, indium tin oxide particles, zirconium oxide particles, copper oxide particles, iron oxide particles, magnetic powder, carbon particles and carbon particles Provided is a porous membrane which is at least one selected from the group consisting of carbon nanotubes, and the content of the inorganic particles in the porous membrane is 20 to 90% by weight .

  The average particle size of the primary particles of the inorganic particles is, for example, 0.01 to 10 μm.

  The thickness of the porous film is, for example, 5 to 200 μm.

  The porous membrane is obtained by casting a porous film-forming material dispersion liquid containing the polymer and inorganic particles constituting the porous film in the form of a film on a substrate, and thereafter, The film-like porous layer may be formed by immersing the film-like porous layer, peeling the formed film-like porous layer from the substrate, and then subjecting the film-like porous layer to drying.

  The present invention is also a method for producing the porous film, wherein a porous film-forming material dispersion liquid containing a polymer and inorganic particles that constitute the porous film is flown onto the substrate in the form of a film. And then dipping it in a coagulation liquid, peeling off the formed film-like porous layer from the substrate, and then subjecting the film-like porous layer to drying. I will provide a.

  In this production method, after casting the porous film-forming material dispersion in the form of a film on a substrate, it is held for 0.2 minutes or more in an atmosphere at a relative humidity of 70 to 100% and a temperature of 15 to 100 ° C., Thereafter, this may be immersed in a coagulation liquid.

  The present invention further comprises a laminate having at least a base material and a porous film layer containing inorganic particles provided on at least one surface of the base material, wherein the porous film layer is the porous material described above. Provided is a laminate composed of a film.

  Furthermore, the present invention is a method for producing the above laminate, wherein a porous membrane-forming material dispersion containing a polymer and inorganic particles that constitute the porous membrane is formed into a film on a substrate. There is provided a method for producing a laminate comprising casting, then immersing it in a coagulation liquid and then subjecting it to drying.

  In this production method, the porous film-forming material dispersion is cast in the form of a film on a substrate, and then kept for 0.2 minutes or more in an atmosphere with a relative humidity of 70 to 100% and a temperature of 15 to 100 ° C. Thereafter, this may be immersed in a coagulation liquid.

  In the present invention, at least one functional layer selected from the group consisting of a conductor layer, a dielectric layer, a semiconductor layer, an insulator layer, and a resistor layer is provided on at least one surface of the porous film. Provided functional laminate.

  The present invention further provides at least one functional layer selected from the group consisting of a conductor layer, a dielectric layer, a semiconductor layer, an insulator layer, and a resistor layer on the surface of the porous film layer of the laminate. Provided functional laminate.

  The porous film containing the inorganic particles of the present invention is given a new or high function by combining other materials depending on the type of inorganic particles to be blended. For this reason, it is useful as a highly functional porous membrane in a wide range of fields.

  More specifically, the porous film containing the inorganic particles of the present invention can be used as a material for a display device of electronic paper. When a white pigment such as titanium oxide is contained as the inorganic particles, the reflectance can be increased. Even in the air particle movement method that does not use a liquid, it is possible to utilize the high reflectance, but the function can be exhibited more in the method in which the porous film is impregnated with the liquid. Porous membranes that do not contain titanium oxide are in a state where irregular reflection occurs at the interface between the resin and air and the reflectance is high, but when the porous membrane is impregnated with liquid, irregular reflection is suppressed and the reflectance tends to decrease. is there. However, in a porous film containing a white pigment such as titanium oxide, even if the porous film is impregnated with a liquid, the white pigment such as titanium oxide has a high reflectance, so that a decrease in reflectance is reduced.

  The porous film of the present invention can be used as a photoelectrode for a dye-sensitized solar cell. Since it is possible to contain a large amount of titanium oxide in the porous membrane and it can be handled in a flexible film form, it has excellent adhesion compared to conventional titanium oxide porous membranes, There is an advantage that it is difficult to break. Also in the manufacturing process of the solar cell, the process of applying and drying the paste on the transparent electrode can be achieved by simply stacking the porous film on the transparent electrode, which can contribute to simplification of the process.

  Also, as inorganic particles, titanium oxide particles, silica particles, alumina particles, barium titanate particles, barium sulfate particles, indium tin oxide particles, zirconium oxide particles, copper oxide particles, iron oxide particles, magnetic powder, carbon particles, carbon nanotubes By using boron nitride, aluminum nitride, etc., for example, reflection characteristics, aesthetics, electrical conductivity, thermal conductivity, electromagnetic wave shielding characteristics, electromagnetic wave absorption characteristics, adsorption characteristics, corrosion resistance, wear resistance, heat resistance, water repellency, Various functions according to the kind of inorganic particles, such as wettability, catalytic activity, high dielectric property, insulating property, pyroelectricity, and piezoelectricity, can be imparted to the porous film.

  Furthermore, the laminate of the present invention in which the porous film of the present invention is laminated on a substrate, and the conductor layer and dielectric layer on the surface of the porous film of the present invention or on the surface of the porous film in the laminate According to the functional laminate in which at least one functional layer selected from the group consisting of a semiconductor layer, an insulator layer and a resistor layer is provided, the functionality is further enhanced by providing other functions. It can be used as a porous membrane.

2 is an electron micrograph (SEM photograph) of the surface of a porous membrane containing inorganic particles obtained in Example 1. FIG. It is an electron micrograph (SEM photograph) of the surface of the porous membrane containing the inorganic particles obtained in Example 6.

[Porous membrane]
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 composition containing a polymer and inorganic particles, and the average of micropores in the porous membrane is The pore diameter is 0.01 to 10 μm, and the porosity is 30 to 85%. In the porous membrane of the present invention, inorganic particles are dispersed in the polymer with good uniformity. In addition, the porous film of the present invention is characterized in that the inorganic particles are dispersed in the polymer, so that a high porosity is maintained without filling the pores.

  Examples of the polymer constituting the porous membrane include polyimide resins, polyamideimide resins, polyetherimide resins, polyethersulfone resins, cellulose resins, polyamide resins (aromatic polyamide resins, non-aromatics). Group polyamide resins), polysulfone resins, acrylic resins, aramid resins, polyimidazole resins, polyparaphenylene benzoxazole resins, polyphenylene sulfide resins, polyarylate resins, polyester resins (liquid crystalline polyester resins) Include), polycarbonate resins, polyether ether ketone resins, and the like. These resins may be copolymers (graft copolymers, block copolymers, random copolymers). In addition, a polymer containing the resin skeleton (polymer chain) in the main chain or side chain (for example, a polysiloxane-containing polyimide containing a polysiloxane and polyimide skeleton in the main chain) can also be used. These resins can be used alone or in combination of two or more.

  Among these, as the polymer, polyimide resin, polyamideimide resin, polyetherimide resin, polyethersulfone resin, cellulose resin, polyamide resin (aromatic polyamide resin, non-aromatic polyamide resin) And at least one selected from the group consisting of polysulfone resins. In particular, at least one resin selected from the group consisting of polyimide resins, polyamideimide resins, polyetherimide resins, and polyamide resins (aromatic polyamide resins and non-aromatic polyamide resins) is preferable. These polymers are particularly excellent in heat resistance, mechanical strength, chemical resistance, and electrical properties.

  The polymer constituting the porous film may be a polymer having a crosslinked structure. Such a polymer is, for example, a porous material containing a polymer having a crosslinkable functional group and a crosslinker capable of undergoing a crosslinking reaction with the crosslinkable functional group in the method for producing a porous film of the present invention described later. It can be obtained by forming a porous film using a material for forming a film and then causing a crosslinking reaction. A porous film using a polymer having a crosslinked structure is excellent in film strength, heat resistance, chemical resistance, and durability.

  Examples of the crosslinkable functional group include an amide group, a carboxyl group, an amino group, an isocyanate group, a hydroxyl group, an epoxy group, an aldehyde group, and an acid anhydride group.

  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 membrane is composed of a polyimide resin, the solubility becomes worse when imidized. Therefore, after first forming the porous membrane at the polyamic acid stage, imidization (thermal imidization, chemical imidization, etc.) Often done. Since the molecule of the polyimide precursor has many carboxyl groups and amide groups, these can be used as crosslinkable functional groups. In addition, the polyimide resin often has a carboxyl group, an amino group, or the like remaining at the terminal, and these can also be used as crosslinkable functional groups.

  The polyamide-imide 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 the polyamideimide resin has many amide groups in the molecule, it can be used as a functional group capable of crosslinking. In addition, some imides remain reactive in the state of an unreacted precursor (amic acid), and the amide group or carboxyl group constituting this amic acid is used as a crosslinkable functional group. Can do. In addition, since the polyamideimide resin is produced by the above reaction, a carboxyl group, an isocyanate group, an amino group or the like often remains at the terminal, and these can be used as a functional group capable of crosslinking. .

  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. In addition, the polyetherimide resin often has a carboxyl group, an isocyanate group, an amino group, or the like remaining 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. Polyamide resins also include aromatic polyamide resins. Since the polyamide-based resin has a large number of amide groups in the molecule, it can be preferably used as a crosslinkable functional group. In addition, the polyamide resin often has a carboxyl group, an amino group, or the like remaining at the terminal, and these can be used as a functional group capable of crosslinking.

  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 functional group which can be bridge | crosslinked may exist in rings, such as a benzene ring contained in polymer | macromolecule.

  The crosslinking agent is a compound that can react with a crosslinkable functional group of the polymer to form a crosslinked structure. Examples of the crosslinking agent include compounds having two or more epoxy groups, polyisocyanate compounds, silane coupling agents, melamine resins, phenol resins, urea resins, guanamine resins, alkyd resins, dialdehyde compounds, acid anhydrides, and the like. Can be mentioned. A crosslinking agent can be used individually or in combination of 2 or more types.

  The compound having two or more epoxy groups is a crosslinkable functional group possessed by the polymer, such as an amide group, a carboxyl group, an amino group, an isocyanate group, a hydroxyl group, an epoxy group, an aldehyde group, an acid. Can react with anhydride groups. The polyisocyanate compound can react with a crosslinkable functional group of the polymer, for example, a carboxyl group, an amino group, a hydroxyl group, an epoxy group, or an acid anhydride group. The silane coupling agent reacts with the crosslinkable functional group of the polymer, for example, amide group, carboxyl group, amino group, isocyanate group, hydroxyl group, epoxy group, aldehyde group, and acid anhydride group. sell. The melamine resin can react with a crosslinkable functional group possessed by the polymer, for example, an amino group, a hydroxyl group, or an aldehyde group. The phenol resin can react with a crosslinkable functional group possessed by the polymer, for example, a carboxyl group, an amino group, an isocyanate group, a hydroxyl group, an epoxy group, an aldehyde group, or an acid anhydride group. The urea resin can react with a crosslinkable functional group possessed by the polymer, for example, an amino group, a hydroxyl group, or an aldehyde group. The guanamine resin can react with a crosslinkable functional group of the polymer, for example, an aldehyde group. The alkyd resin can react with a crosslinkable functional group of the polymer, for example, a carboxyl group, an isocyanate group, a hydroxyl group, an epoxy group, or an acid anhydride group. The dialdehyde compound can react with a crosslinkable functional group of the polymer, for example, an amino group or a hydroxyl group. The acid anhydride can react with a crosslinkable functional group of the polymer, for example, an amino group, an isocyanate group, a hydroxyl group, or an epoxy group.

  Examples of a method of reacting a crosslinkable functional group in a polymer with a crosslinking agent include a method by heat and irradiation with active energy rays (visible light, ultraviolet rays, electron beams, radiation, etc.). The reaction with the cross-linking agent can proceed without a catalyst, but a catalyst can be added to promote the reaction.

  The blending ratio of the polymer having a crosslinkable functional group and the crosslinking agent is not particularly limited, and the desired degree of crosslinking, the kind of the polymer and the crosslinking agent, the functional group and the crosslinking agent, It is appropriately determined in consideration of the reactivity of For example, the compounding amount of the crosslinking agent is 2 to 312.5 parts by weight, preferably 10 to 200 parts by weight, more preferably 20 to 150 parts by weight with respect to 100 parts by weight of the polymer having a crosslinkable functional group. is there. If the amount of the crosslinking agent is too large, the crosslinking agent that does not contribute to the crosslinking reaction may remain in the porous film after the crosslinking treatment, and the characteristics of the porous film may be deteriorated.

  In the present invention, the inorganic particles constituting the porous membrane are not particularly limited, and inorganic particles having various functions can be used depending on the purpose. Examples of the material constituting the inorganic particles include titanium oxide, silica, alumina, barium titanate, barium sulfate, indium tin oxide, zirconium oxide, copper oxide, iron oxide, ferrite, carbon, calcium carbonate, talc, clay, and alumino. Examples include silicate, zinc oxide, zinc sulfide, lead white, lead titanate, barium sulfide, molybdenum sulfide, strontium titanate, mica, boron nitride, aluminum nitride, metal (copper, nickel, silver, etc.). By including these inorganic particles in the porous film, depending on the type, for example, reflection characteristics (titanium oxide particles, zirconium oxide particles, barium sulfate particles, barium titanate particles, silica particles, alumina particles, etc.), Aesthetics (titanium oxide particles, zirconium oxide particles, barium sulfate particles, barium titanate particles, silica particles, alumina particles, etc.), electrical conductivity (carbon particles, carbon nanotubes, indium tin oxide particles, etc.), thermal conductivity (boron nitride) Particles, aluminum nitride particles, alumina particles, carbon particles, carbon nanotubes, etc.), electromagnetic shielding properties [metal powder (copper particles, nickel particles, silver particles, etc.)], electromagnetic wave absorption properties (magnetic powder, iron oxide particles, ferrite particles, etc.) , Carbon particles, etc.), adsorption characteristics (silica particles, alumina particles, titanium oxide) Particles), corrosion resistance (zirconium oxide particles, etc.), wear resistance (molybdenum disulfide particles, etc.), heat resistance (zirconium oxide particles, titanium oxide particles, alumina particles, etc.), water repellency, wettability (titanium oxide particles, etc.) ), Catalytic activity (photocatalytic activity, etc.) (titanium oxide particles, copper oxide particles, iron oxide particles, etc.), high dielectric properties (barium titanate particles, strontium titanate particles, titanium oxide particles, etc.), insulation, pyroelectricity Various functions such as (barium titanate particles, etc.) and piezoelectric properties (barium titanate particles, zirconium oxide particles, etc.) can be imparted to the porous film.

  Among these, as the inorganic particles, titanium oxide particles, silica particles, alumina particles, barium titanate particles, barium sulfate particles, indium tin oxide particles, zirconium oxide particles, copper oxide particles, iron oxide particles, magnetic powder, carbon particles and It is preferably at least one selected from the group consisting of carbon nanotubes.

  The average particle size of the primary particles of the inorganic particles is, for example, 0.01 to 10 μm, preferably 0.05 to 8 μm, and more preferably 0.1 to 3 μm. If the average particle size of the inorganic particles is too small, aggregation tends to occur and it becomes difficult to uniformly disperse in the polymer. Moreover, when the average particle diameter of the inorganic particles is too large, the pore structure formed by the polymer tends to be inhomogeneous.

  The content of inorganic particles in the porous membrane of the present invention is, for example, 10 to 95% by weight, preferably 20 to 90% by weight, and more preferably 25 to 85% by weight. If the content of the inorganic particles is too small, the effect of adding the inorganic particles, that is, the functionality based on the inorganic particles is reduced. Conversely, if the content of the inorganic particles is too large, the film tends to become brittle.

  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 is difficult to produce stably, and cushioning properties, printing characteristics, and mechanical strength may be reduced. On the other hand, when it is too thick, it becomes difficult to uniformly control the pore size distribution.

  In the present invention, the numerous micropores of the porous membrane may be independent micropores (independent micropores) with low communication or may be micropores with communication (continuous micropores). . Porous membranes with many independent micropores are suitable for applications that require heat insulation, cushioning, and impermeability, and porous membranes with many continuous micropores require permeability, adsorptivity, and high catalytic activity. Suitable for the intended use. The average pore diameter of the micropores in the porous membrane [in the case of a porous membrane having many continuous micropores (a porous membrane having a Gurley value of 30 seconds / 100 cc or less, which will be described later), the average pore size on the surface of the porous membrane, In a porous film having many pores (a porous film having a Gurley value exceeding 30 seconds / 100 cc described later), the average pore diameter of the micropores in the porous film] is 0.01 to 10 μm. The average pore diameter of the micropores is preferably 0.1 to 8 μm, more preferably 0.5 to 5 μm. If the average pore diameter of the micropores is out of the above range, it is difficult to obtain a desired effect according to the application. For example, when the average pore diameter of the micropores is too small, the permeation performance and strength are reduced. If the average pore size of the micropores is too large, it may be difficult to uniformly control the pore size distribution in the porous membrane, and the relative dielectric constant may be inhomogeneous at each part of the porous membrane. In addition, separation efficiency, reflection characteristics, adsorption characteristics, catalytic activity, and the like are likely to decrease. The maximum pore diameter on the porous membrane surface is preferably 15 μm or less.

  In the present invention, the porosity of the porous membrane (internal average porosity) is 30 to 85%, preferably 35 to 83%, and more preferably 40 to 80%. If the porosity of the porous membrane is out of the above range, desired pore characteristics depending on the application cannot be obtained. For example, if the porosity is too low, the permeation performance, adsorption characteristics, cushioning properties, etc. may not be sufficient, or the function may not be exhibited even if functional materials are filled. On the other hand, if the porosity is too high, the mechanical strength may be inferior.

  When the porous membrane has such an average pore diameter and porosity, the porous membrane has flexibility and excellent pore characteristics, but has excellent rigidity and handling properties.

  The porosity of the surface of the porous film (surface porosity) is, for example, 48% or more (for example, 48 to 80%), and preferably about 60 to 80%. If the surface area ratio is too low, the transmission performance may not be sufficient, and even if the pores are filled with a functional material, the function may not be fully achieved. It becomes easy to do.

  The connectivity of the micropores existing in the porous membrane can be determined by using the Gurley value representing the air permeability and the pure water permeation rate as an index. The Gurley value of the porous film having a thickness of 30 μm is, for example, 0.2 to 30 seconds / 100 cc, preferably 0.5 to 25 seconds / 100 cc, more preferably 0.8 to 20 seconds / 100 cc, and particularly preferably 1 to 1. 10 seconds / 100 cc. If the numerical value is too large, the practical permeation performance may not be sufficient, or the functional material may not be sufficiently filled and the function may not be exhibited. On the other hand, if the value is too small, the mechanical strength may be inferior.

  The pore size, porosity, air permeability, and porosity of the porous membrane are the substrate used, the type and amount of the water-soluble polymer, the amount of water used, and the casting time in the porous membrane manufacturing method described later. By appropriately selecting the humidity, temperature, time, and the like, it can be adjusted to a desired value.

[Manufacture of porous membrane]
The porous film of the present invention is obtained by casting a dispersion liquid of a porous film forming material containing a polymer and inorganic particles that constitute the porous film onto a substrate in the form of a film, and then coagulating the liquid. It can be manufactured by dipping in, peeling the formed film-like porous layer from the substrate, and then subjecting the film-like porous layer to drying.

  Examples of substrates used in this production method include glass plates; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyesters such as nylon and polyethylene terephthalate (PET); polycarbonates, styrene resins, and polytetrafluoroethylene (PTFE). ), A plastic sheet made of a fluororesin such as polyvinylidene fluoride (PVDF), a vinyl chloride resin, or other resin; a metal plate such as a stainless steel plate or an aluminum plate. In addition, the composite board which combined the surface material and the internal material with a different thing may be sufficient.

  The dispersion of the porous film-forming material (hereinafter sometimes simply referred to as “dispersion”) includes, for example, a polymer component, inorganic particles, and a water-soluble polar solvent that are the main materials constituting the porous film. If necessary, it contains a water-soluble polymer, water if necessary, and a crosslinking agent (if a crosslinked structure is formed in the molecule of the polymer) if necessary. In the dispersion, instead of the polymer component constituting the porous membrane, a monomer component of the polymer component, an oligomer thereof, a precursor before imidization or cyclization, or the like may be used. .

  Adding a water-soluble polymer or water to the dispersion is effective for making the membrane structure porous. Examples of the water-soluble polymer include polyethylene glycol, polyvinyl pyrrolidone, polyethylene oxide, polyvinyl alcohol, polyacrylic acid, polysaccharides, and derivatives thereof. These water-soluble polymers can be used alone or in combination of two or more. Among these, polyvinylpyrrolidone is particularly preferable from the viewpoint of the connectivity of the micropores present in the porous membrane. In order to make it porous, the weight average molecular weight of the water-soluble polymer should be 200 or more, preferably 300 or more, more preferably 1000 or more, and particularly preferably 5000 or more (for example, 5000 to 200,000). The pore size can be adjusted by the amount of water added. For example, the pore size can be increased by increasing the amount of water added to the dispersion.

  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 kind 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 inversion method, components that do not constitute a porous membrane (unnecessary components) are removed by heating, and water-soluble polymers are usually unsuitable for removal by heating, so use them as additives. Is extremely difficult. 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.

  In the method of the present invention, when the amount of the water-soluble polymer added is increased, the pore connectivity tends to increase. Therefore, when it is desired to obtain a porous membrane with low connectivity (a porous membrane having many independent micropores), it is preferable to minimize the amount of the water-soluble polymer, and it is also possible not to use the water-soluble polymer. is there.

  Examples of the water-soluble polar solvent include dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), 2-pyrrolidone, and γ-butyrolactone. In addition, those having solubility (good solvent for the polymer component) can be used according to the chemical skeleton of the polymer used as the polymer component. These solvents can be used alone or in combination of two or more.

  The amount of each component in the dispersion is 8 to 25% by weight of the polymer component, 0 to 25% by weight of the cross-linking agent, 10 to 50% by weight of the water-soluble polymer, and 0 to 0% by weight of water based on the dispersion. It is preferable to set it as 10 weight% and 30-82 weight% of water-soluble polar solvents. At this time, if the concentration of the polymer component is too low, the thickness of the porous membrane becomes insufficient, the desired pore characteristics are difficult to obtain, and the strength of the porous membrane tends to be weak, while If the concentration of the molecular component is too high, the porosity tends to decrease. If the concentration of the water-soluble polymer is too low, huge voids exceeding 10 μm are generated inside the porous membrane, and the homogeneity tends to be lowered. If the concentration of the water-soluble polymer is too high, problems such as poor solubility of each component and a decrease in the strength of the porous membrane are likely to occur.

  A dispersion of the porous film-forming material is cast into a film on a substrate, and then immersed in a coagulation liquid to cause phase change.

  When the porous film-forming material dispersion is cast into a film on the substrate and then immersed in the coagulation liquid, it may or may not adhere to the substrate depending on the type of polymer component. There is. Specifically, a polyamideimide resin or a polyimide resin is a resin that easily attaches to a substrate, and a polyetherimide resin is a resin that does not easily attach to a substrate.

  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. Monohydric alcohols such as methanol and ethanol, alcohols such as polyhydric alcohols such as glycerin; water-soluble polymers such as polyethylene glycol; water-soluble coagulating liquids such as a mixture thereof can be used.

  The temperature of the coagulation liquid is not particularly limited, but is preferably in the range of 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 coagulating liquid, water is preferably used from the viewpoints of cost, safety and the like. When water is used as the coagulation 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 the time for sufficiently washing the water-soluble polar solvent and the water-soluble polymer is 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 and the product cost is increased. Since the cleaning time depends on the thickness of the porous film and the like, it cannot be generally specified, but can be about 0.5 to 30 minutes.

  Before immersing the film-like material after casting in the coagulating liquid, the film-like material after casting is 0.2 minutes or more (for example, in an atmosphere consisting of a relative humidity of 70 to 100% and a temperature of 15 to 100 ° C. 0.2 to 180 minutes), preferably 0.2 to 60 minutes, more preferably 0.2 to 15 minutes), and then led into the coagulation liquid. By placing the film-like material after casting under the above humidification conditions, a highly homogeneous porous membrane can be easily obtained. When placed under humidification, it is considered that moisture penetrates from the film surface to the inside, and promotes layer separation of the dispersion efficiently. Therefore, it is presumed that the porosity of the surface opposite to the substrate side surface of the porous membrane (the air side surface of the porous membrane) is improved. 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.

  In the step of peeling the film-like porous layer from the substrate, the film-like porous layer may be forcibly separated from the substrate, or a combination of the polymer component constituting the porous film and the substrate material may be used. If selected and immersed in the coagulation liquid, the film-like porous layer may be peeled off from the substrate.

  Forced peeling tends to make the thickness of the porous film uniform, but care must be taken because it may damage the porous film when 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 substrate to be peeled naturally when guided to the coagulation liquid, it is preferable to use a substrate having high water repellency. For example, a fluorine-based film [for example, a Teflon (registered trademark) film or the like], a film obtained by bonding or coating a fluorine-based resin on the surface, or the like can be used.

  Next, the peeled film-like porous layer is dried. The method for the drying treatment is not particularly limited, and it may be a hot air treatment, a hot roll treatment, or a method of putting it in a thermostat or 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 or an inert gas such as nitrogen. When air is used, it is the cheapest, but may involve an oxidation reaction. In order to avoid this, it is preferable to use an inert gas such as nitrogen, and nitrogen is preferred from the viewpoint of cost. The heating conditions can be appropriately set in consideration of productivity, physical properties of the porous membrane, and the like.

  According to the said method, it has many micropores, the average pore diameter of the said micropores is 0.01-10 micrometers, a porosity is 30-85%, and thickness contains, for example, inorganic particles of 5-200 micrometers A porous membrane can be easily formed. As described above, the micropore diameter, porosity, and open area ratio of the porous membrane are determined by appropriately determining the type and amount of the constituent components of the dispersion, the amount of water used, the humidity during casting, the temperature, and the time. By selecting, it can be adjusted to a desired value.

  When a crosslinked structure is formed in the polymer molecule, the resulting porous film is subjected to a crosslinking treatment. The crosslinking agent (added as necessary) contained in the porous membrane obtained as described above is usually in an unreacted state. However, when the cross-linking agent is thermally cross-linked, depending on the drying treatment conditions, a part or all of the cross-linking agent may react to form a cross-linked structure.

  The cross-linking treatment can be carried out by heat treatment and / or active energy ray (visible light, ultraviolet ray, electron beam, radiation, etc.) irradiation treatment depending on the type of the cross-linking agent. Set appropriate conditions for each. For example, the heat treatment is preferably performed under conditions of 100 to 400 ° C. and 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. When various functional layers are formed on the surface of the porous membrane (porous membrane layer), the functional layer is formed (functional expression) as in the following (b) and (c). It is effective for improving the adhesion between the porous film and the functional layer if cross-linking is caused at the time.

When a functional layer is provided on the surface of the porous membrane (functionalization treatment) to obtain a functional laminate, there is a timing 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 functional layer on the obtained porous membrane surface. And then performing a crosslinking treatment to obtain a functional laminate (the crosslinking treatment by heating may also serve as a 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. [Here, the partial cross-linking treatment is intended to be a semi-cured state (so-called B stage)]

  The porous membrane may shrink 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, a part of the porous film may be fixed to a film, plate, frame-like object (frame), bat or the like made of resin, metal, glass or the like. In addition, the shrinkage rate in the surface direction can be appropriately controlled by the fixing method, and the thickness, porosity, and the like can also be controlled.

  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.

  In the porous membrane of the present invention, the porous membrane may be coated with a chemical resistant polymer compound.

  Here, the chemical is known as a 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 solvent such as 2-pyrrolidone (NMP), 2-pyrrolidone, cyclohexanone, acetone, methyl acetate, ethyl acetate, ethyl lactate, acetonitrile, methylene chloride, chloroform, tetrachloroethane, tetrahydrofuran (THF); alkaline solution; acidic Solutions; and mixtures thereof. The alkaline solution includes inorganic salts such as sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, and potassium carbonate; amines such as triethylamine; aqueous solutions and organic solvent solutions in which alkaline substances such as ammonia are dissolved. . Examples of the acidic solution include aqueous solutions and organic solvent solutions in which acids such as inorganic acids such as hydrogen chloride, sulfuric acid, and nitric acid; and organic acids such as carboxylic acids such as acetic acid and phthalic acid are dissolved.

  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 of two or more. The polymer compound may be a copolymer or a graft polymer.

  When a 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 occurs, such as when it occurs, or there is no influence on the purpose of use or the use. 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 often has heat resistance at the same time, there is little fear that the heat resistance of the porous membrane is lowered. 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 chemical-resistant 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, applications using both the pore characteristics of the porous film and the characteristics of the inorganic particles, for example, electronic paper display devices (films for electronic paper), photoelectrodes such as dye-sensitized solar cells, For photocatalysts, circuit boards, heat radiation materials (heat sinks, heat radiation plates), electromagnetic wave control materials such as electromagnetic wave shields and electromagnetic wave absorbers, antennas, reflection sheets (reflection sheets used for backlight light sources for liquid crystal displays and display bodies, etc.) Available.

[Laminated body having porous membrane layer]
The laminate of the present invention is a laminate having at least a base material and a porous film layer containing inorganic particles provided on at least one side of the base material, and the porous film layer is a porous material. It consists of a membrane.

  Such a laminate can be manufactured using the phase change method described above. That is, a base material (corresponding to the “substrate” in the production of the porous membrane) is a dispersion of a porous membrane-forming material containing a polymer and inorganic particles that constitute the porous membrane (porous membrane layer). It can be produced by casting it in the form of a film and then immersing it in a coagulation liquid and then subjecting it to drying.

For example, the laminate preferably does not cause interfacial peeling between the substrate and the porous membrane layer when a tape peel test based on the following method is performed. That is, it is preferable that the base material and the porous membrane layer are directly laminated with an interlayer adhesion strength that does not cause interfacial peeling in the following tape peeling test.
Tape peel test:
On the surface of the porous membrane layer of the laminate, a 24 mm wide masking tape manufactured by Teraoka Seisakusho [film masking tape No. 603 (# 25)] is applied for a length of 50 mm from one end of the tape, and the attached tape is a roller having a diameter of 30 mm and a load of 200 gf (Holbein Art Materials Inc., oil resistant hard rubber roller No. 10). Then, the other end of the tape is pulled at a peeling speed of 50 mm / min using a tensile tester to perform T-type peeling.

  The substrate may be any of a resin film, a metal foil, a substrate having many through holes, and the like. The substrate may be a single layer or a composite film composed of a plurality of layers made of the same or different materials. The composite film may be a laminated film obtained by laminating a plurality of films using an adhesive or the like as necessary, or may be obtained by performing a treatment such as coating, vapor deposition, or sputtering. In addition, for the base material, roughening treatment, easy adhesion treatment, antistatic treatment, sand blast treatment (sand mat treatment), corona discharge treatment, plasma treatment, chemical etching treatment, water mat treatment, flame treatment, acid treatment, alkali treatment Further, one or more surface treatments such as oxidation treatment, ultraviolet irradiation treatment, silane coupling agent treatment, etc. may be performed.

  Examples of the material constituting the resin film include polyimide resins, polyamideimide resins, polyethersulfone resins, polyetherimide resins, polycarbonate resins, polyphenylene sulfide resins, polyester resins (polyethylene terephthalate resins). , Polyethylene naphthalate resins, polybutylene naphthalate resins, liquid crystalline polyester resins, etc.), polyamide resins (aromatic polyamide resins, non-aromatic polyamide resins), polybenzoxazole resins, polybenzimidazole resins Resin, polybenzothiazole resin, polysulfone resin, cellulose resin, acrylic resin, polyetheretherketone resin, fluorine resin, olefin resin (including cyclic olefin resin), polyary Plastics such as over preparative resins. These materials may be used alone or in admixture of two or more, and the above copolymer of resins may be used alone or in combination of two or more. Furthermore, a polymer containing the above resin skeleton (polymer chain) in the main chain or side chain (for example, a polysiloxane-containing polyimide containing a polysiloxane and polyimide skeleton in the main chain) can also be used.

  The thickness of the resin film substrate is, for example, 1 to 300 μm, preferably 5 to 200 μm, and more preferably 5 to 100 μm. If the thickness is too thin, handling becomes difficult, while if it is too thick, the flexibility may decrease.

  The material constituting the metal foil base material is not particularly limited as long as it does not cause interface peeling with the porous film layer by the tape peeling test, and can be appropriately selected according to the material constituting the porous film layer. Examples of the material constituting the metal foil substrate include copper foil, aluminum foil, iron foil, nickel foil, gold foil, silver foil, tin foil, zinc foil, and stainless steel foil. These materials can be used alone or in admixture of two or more.

  When the porous film layer is formed on one side of the metal foil base material, the adhesive layer may be formed on the surface opposite to the surface when the porous film layer is laminated, and it is easier to handle. Thus, a protective film (release film) may be stuck on the pressure-sensitive adhesive layer.

  The thickness of the metal foil substrate is, for example, 1 to 300 μm, preferably 5 to 200 μm, and more preferably 5 to 100 μm. If the thickness is too thin, handling becomes difficult, while if it is too thick, the flexibility may decrease.

  Moreover, the material which comprises the base material which has many through-holes includes a woven fabric, a mesh cloth, a punching film, a wire net, a punching metal, an expanded metal, an etching metal, and the like. Here, the “base material having a through hole” means a base material having a hole penetrating in a direction substantially perpendicular to the base material plane. The base material having a large number of through holes is not particularly limited as long as a large number of through holes are formed and interface peeling with the porous membrane layer does not occur in the tape peeling test. Examples of the material constituting the base material having a large number of through holes include plastic films or sheets such as woven fabric, mesh cloth, and punching film; metal foils or sheets such as wire mesh, punching metal, expanded metal, and etching metal. Can be selected and used according to the characteristics such as water resistance, heat resistance and chemical resistance. Among these, a mesh cloth having a fine and regular structure is preferably used.

  As the woven fabric, for example, natural fibers such as cotton fibers and silk fibers; one kind selected from glass fibers, PEEK fibers, aromatic polyamide fibers, polybenzoxazole fibers (such as Zylon), carbon fibers, or the like A woven fabric formed by combining two types can be used.

  The mesh cloth has mesh openings (micron number of gap size between threads), thread diameter (micron number of thread thickness), mesh (number of threads between 1 inch), opening rate ( There are various product numbers depending on the ratio of the opening portion to the entire mesh), the thickness (micron number of the thickness of the mesh), and the like. There are various ways of weaving mesh cloth, and there are various types such as ASTM (American Industrial Standard), DIN (German Industrial Standard), HD, XX, GG, HC & P, Schlinger and the like. Among these, those having physical properties according to the purpose can be appropriately selected and used.

  Examples of the punching film include those in which holes such as a circle, a square, a rectangle and an ellipse are formed by punching a film such as PET or polyimide.

  Commercially available plain woven wire mesh, twill woven wire mesh, flat woven wire mesh, twill woven wire mesh, or the like can be used as the wire mesh. Examples of the material include iron, stainless steel, copper, and nickel.

  Examples of the punching metal include those obtained by punching a metal foil or sheet to form holes such as a circle, a square, a rectangle, and an ellipse. Examples of the material include iron, aluminum, stainless steel, copper, and titanium.

  As an expanded metal, the thing of the shape of a JIS specification can be mentioned. For example, there are XS63 and XS42 flats. Examples of the material include iron, aluminum, and stainless steel.

  The base material having a large number of through holes can be manufactured by a conventional method according to the material such as a processing method such as etching, punching, or laser irradiation. According to the base material having a large number of such through holes, there is an advantage that the porous film layer can be laminated with excellent interlayer adhesion strength by applying the polymer solution to the surface and laminating the porous membrane layer. Moreover, since it has a softness | flexibility and the outstanding void | hole characteristic, but has moderate rigidity, the effect which improves a handleability can be acquired.

  When the base material having a large number of through holes is a mesh cloth, the average pore diameter (opening: size of the gap between the wire and the wire) on the surface of the base is, for example, about 30 to 1000 μm, preferably about 40 to 200 μm. The surface opening ratio (opening ratio: the ratio of the opening area to the entire mesh area) is, for example, 20 to 70%, preferably about 25 to 60%. When each numerical value of the opening and the opening ratio is too low, interlayer adhesion is insufficient or flexibility tends to be low, and when each numerical value is too high, the mechanical strength is rigid. It tends to decrease and tends to be inferior in handleability, both of which are not preferred.

  When the substrate having a large number of through holes is a punching film or a punching metal, the surface opening ratio is about 20 to 80%, preferably about 30 to 70%. When the numerical value of the surface open area ratio is too low, the permeability of gas or liquid tends to deteriorate, and when the numerical value is too high, the strength tends to decrease and the handling property tends to be inferior.

  When the base material having a large number of through holes is a wire mesh, the surface area ratio is about 20 to 80%, preferably about 25 to 70%. When the numerical value of the surface open area ratio is too low, the permeability of gas or liquid tends to deteriorate, and when the numerical value is too high, the strength tends to decrease and the handling property tends to be inferior.

  When the base material having a large number of through holes is an expanded metal, the surface open area ratio is about 20 to 80%, preferably about 25 to 70%. When the numerical value of the surface open area ratio is too low, the permeability of gas or liquid tends to deteriorate, and when the numerical value is too high, the strength tends to decrease and the handling property tends to be inferior.

  The thickness of the substrate having a large number of through holes is, for example, 1 to 1000 μm. If the thickness is too thin, handling becomes difficult, while if it is too thick, the flexibility may decrease.

  The porous film constituting the porous film layer is the porous film of the present invention.

  When the substrate is a resin film or a metal foil, the thickness of the porous membrane layer is, for example, 0.1 to 100 μm, preferably 0.5 to 70 μm, and more preferably 1 to 50 μm. If the thickness is too thin, it is difficult to produce stably, whereas if it is too thick, it is difficult to uniformly control the pore size distribution.

  The thickness of the porous membrane layer is, for example, 0.1 to 1000 μm, preferably 0.5 to 500 μm, and more preferably 1 to 200 μm when the substrate has a large number of through holes. If the thickness is too thin, it is difficult to produce stably, whereas if it is too thick, it is difficult to uniformly control the pore size distribution.

  In the laminate of the present invention, the base material and the porous membrane layer are directly laminated with an interlayer adhesion strength that does not cause interfacial peeling in the tape peeling test without passing through another layer. Means for improving the adhesion between the base material and the porous membrane layer include, for example, sandblasting (sand matting) corona discharge treatment, acid treatment, alkali on the surface of the base material on which the porous membrane layer is laminated. Method of performing appropriate surface treatment such as treatment, oxidation treatment, ultraviolet irradiation treatment, plasma treatment, chemical etching treatment, water mat treatment, flame treatment, silane coupling agent treatment; component constituting the substrate and the porous membrane layer And a method using a combination of materials that can exhibit good adhesion (affinity, compatibility). A plurality of the surface treatments may be performed in combination, and depending on the substrate, it is preferable that the surface treatment is performed in combination with a silane coupling agent treatment and other treatments.

  From the viewpoint of adhesion between the substrate and the porous membrane layer, the laminate of the present invention has, for example, a polymer component constituting the porous membrane layer comprising a polyimide resin, a polyamideimide resin, a polyetherimide resin. And at least one selected from aromatic polyamide-based and non-aromatic polyamide-based resins, and the material constituting the base material is polyimide-based resin, polyamide-imide-based resin, polyether-imide-based resin, polyester-based resin, liquid crystal It is preferably composed of at least one selected from a reactive polyester resin, an aromatic polyamide resin, a polyethylene terephthalate resin, and a polyethylene naphthalate resin. From the same viewpoint, as a preferred embodiment of the laminate, some or all of the components constituting the substrate and the porous membrane layer are the same, for example, at least some of the monomer units of the polymer compound constituting both layers are common The structure which is is mentioned. In such a porous membrane laminate, for example, the material constituting the substrate / porous membrane layer is polyimide / polyimide, polyamideimide / polyimide, polyimide / polyamideimide, polyetherimide / polyimide, polyimide / polyetherimide. , A laminate comprising a combination of polyamideimide / polyetherimide, polyetherimide / polyamideimide, and the like.

  The porous membrane layer should just be formed in the at least single side | surface of a base material, and can also be formed in both surfaces. By forming a porous film layer on both sides of the substrate, taking advantage of its pore characteristics and the characteristics of inorganic particles, both sides have reflectivity, optical characteristics, low dielectric constant, cushioning, heat insulation, etc. A given porous membrane laminate can be obtained.

  Since the laminate of the present invention has a structure in which a flexible porous film is laminated on a substrate having sufficient strength, it has the above-described excellent pore characteristics and various characteristics of inorganic particles and is sufficient. Has excellent folding resistance. The folding resistance is evaluated by repeatedly performing a bending test based on the following conditions and having folding resistance when the number of times until the test material is cut is 10 times or more. In addition, it is judged that the higher the number of folds until cutting, the better the folding resistance. For example, in applications where repeated bending is required for electronic materials, etc., the number of folds is about 100 or more. It is preferable. The bending test uses an MIT fatigue resistance tester MIT-D manufactured by Toyo Seiki Seisakusho, sample shape 15 × 110 mm, bending angle 135 °, bending radius of curvature (R) 0.38 mm, bending speed 175 cpm, tension It is performed according to the fold resistance test of JIS C 5016 under the condition of 4.9N.

  According to the laminated body of the present invention, a laminate that is not cut even when the number of folding times is 20000 times and has extremely excellent folding resistance is included. For this reason, excellent workability and moldability can be exhibited, and it can be used in a wide variety of applications in various forms.

  In the preferred form of the laminate of the present invention, when the substrate is a resin film or a metal foil, one or both surfaces of the substrate are covered with a porous membrane layer, and have micropores with high communication properties. A porous membrane laminate having a porous membrane layer having an average pore diameter of 0.01 to 10 μm, the thickness of the porous membrane layer is 5 to 200 μm, and the porosity is 30 to 85%. The thickness of the base material is 1 to 300 μm. Such a porous membrane laminate can be produced by appropriately setting the material and thickness constituting the porous membrane layer and the substrate, production conditions (for example, humidification conditions), and the like.

  As described above, the laminate of the present invention uses a dispersion of a porous film-forming material containing a polymer to form a porous film and inorganic particles as a base material (“substrate” in the production of the porous film). The film can be cast in the form of a film, and then immersed in a coagulating liquid and then dried. That is, the laminate of the present invention uses the base material as a “substrate” in the method for producing the porous membrane (however, the film-like porous membrane layer formed by immersion in a coagulating liquid is used as the base material). Can be manufactured by omitting the step of peeling from the substrate.

  In the method for producing a laminate of the present invention, a porous layer is directly laminated on the surface of the substrate by directing it to a coagulating liquid and forming a porous layer on the surface of the substrate, followed by drying as it is. A porous membrane laminate having the following is produced. Drying is not particularly limited as long as it is a method capable of removing a solvent component such as a coagulation liquid as described above, and may be under heating or natural drying at room temperature. The method for the heat 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, an oven, or the like, as long as the porous film laminate can be controlled to a predetermined temperature. The heating temperature can be selected from a wide range of room temperature to about 600 ° C., for example. The atmosphere during the heat treatment 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 layer and the substrate, and the like. By subjecting to drying, a porous membrane laminate in which the porous membrane layer is directly formed on the substrate surface can be obtained.

  The porous film laminate thus obtained may be further subjected to a crosslinking treatment using heat, visible light, ultraviolet light, electron beam, radiation or the like. By the treatment, polymerization, crosslinking, curing, etc. of the precursor constituting the porous membrane layer proceed to form a polymer compound, and when the polymer porous membrane layer is composed of a polymer compound, crosslinking is performed. And a porous film laminate having a porous film layer that has been further improved in properties such as rigidity and chemical resistance due to progress of curing and the like. For example, a polyimide porous membrane layer can be obtained by subjecting a porous membrane layer formed using a polyimide precursor to thermal imidization or chemical imidization. The porous membrane layer formed using the polyamide-imide resin can be subjected to thermal crosslinking. The thermal crosslinking can also be performed simultaneously with the heat treatment for drying after being led to the coagulation liquid. Even when a cross-linking agent is added to the dispersion of the porous film-forming material, the cross-linking reaction proceeds by the same treatment as above, and a cross-linked structure is formed in the polymer molecule.

  In some cases, the crosslinking treatment may cause a crosslinking reaction between the polymer porous membrane layer and the base film. Thereby, the adhesiveness of a base film and a porous membrane layer improves. For example, when a polyimide film on which a porous film layer of a polyimide-based precursor is formed is heat-treated, the precursor becomes a polyimide and simultaneously adheres to the polyimide film. Further, when the polyimide film on which the polyamideimide resin porous film layer is formed is heat-treated, the porous film layer adheres to the polyimide film.

  According to the method for producing a laminate of the present invention, one side or both sides of a base film are covered with a polymer porous membrane layer containing inorganic particles, and the polymer porous membrane layer has a large number of highly communicable layers. A film having micropores and having an inorganic particle-containing porous membrane layer having an average pore size of 0.01 to 10 μm can be easily obtained.

  The laminate (porous membrane laminate) of the present invention only needs to have an inorganic particle-containing porous membrane layer laminated on at least one side of the substrate, and has an inorganic particle-containing porous membrane layer on both sides of the substrate. May be. Moreover, the inorganic particle containing porous membrane layer may be laminated | stacked on one surface of a base material, and the inorganic particle non-containing porous membrane layer may be laminated | stacked on the other surface of the base material. Further, the porous film laminate may be subjected to heat treatment or film formation treatment as necessary in order to impart desired characteristics.

  Since the laminated body of this invention has the said structure, it can apply to various uses in a wide field | area. Specifically, by utilizing the pore characteristics of the porous film layer containing inorganic particles and the various characteristics of the inorganic particles, for example, reflectors, electronic paper display device materials, dye-sensitized solar cells It can be used as a photoelectrode, a low dielectric constant material, a separator, a cushion material, an ink image receiving sheet, a test paper, an insulating material, a heat insulating material, and the like. Furthermore, as a composite material in which other layers (metal plating layer, magnetic plating layer, etc.) are laminated on the porous membrane laminate, electromagnetic wave control such as circuit boards, heat dissipation materials (heat dissipation plates, etc.), electromagnetic wave shields and electromagnetic wave absorbers, etc. It can be used as a material, cell culture substrate and the like.

[Functional laminate (composite material)]
Functional layers such as a conductor layer, a dielectric layer, a semiconductor layer, an insulator layer, and a resistor layer can be provided on the surface of the porous film of the present invention or the surface of the porous film layer of the laminate. . Thus, by providing a conductor layer on the surface of the porous film or the porous film layer of the laminate, in addition to the pore characteristics of the porous film and the functional characteristics of the inorganic particles, it is further separated. Can be added. Since such a functional laminate has a plurality of functions, it can be used for various purposes in a wider field. In the present specification, a functional laminate in which a functional layer is provided on the surface of the porous membrane or the porous membrane layer of the laminate is sometimes referred to as a “composite material”.

  The formation of various functional layers or precursor layers thereof on the surface of the porous film or the porous film layer of the laminate can be performed by, for example, plating, printing technology, or the like. The layer formed by plating includes a metal plating layer and a magnetic plating layer.

  The metal plating layer is formed, for example, as a thin metal coating on the surface of the porous film or the porous film layer of the laminated body (hereinafter, these may be simply referred to as “porous film”). Also good. 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, etc. An alloy film can also be mentioned. 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 is a compound having 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 a site capable of generating radicals such as methoxyacetonitrile polymer, metal complex compounds such as charge transfer complexes of decamethylferrocene, and carbonized carbon materials An organic magnetic material composed 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 to provide a photosensitive layer, and the photosensitive layer through a mask. A method comprising: exposing and forming a reactive group in the exposed portion; and bonding the reactive group generated in the exposed portion with a metal to form a conductor pattern; or A method comprising a step of using a compound that loses a reactive group by light instead of a compound to be generated, a step of eliminating the reactive group in an exposed portion, and a step of forming a conductor pattern by combining a reactive group remaining in an unexposed portion with a metal. Done.

  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 it can form a bond with a sufficient metal per unit area, and can easily obtain desired conductivity. 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 catalytic 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 a porous membrane or laminate in an aqueous copper sulfate solution, washing away excess copper sulfate as necessary, and then immersing it in an aqueous solution of sodium borohydride. A catalyst nucleus composed of copper fine particles can be formed on the surface of the 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 the metal plating layer on the porous film surface, a method of immersing the porous film or laminate 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 and precipitation control agents such as sodium, EDTA, tartaric acid, malic acid, citric acid and glycine, and many of these are commercially available and can be easily obtained. Electroless plating is performed by immersing the porous film or laminate subjected to the above treatment in the above plating solution. In addition, since electroless plating is performed only on the other surface by applying electroless plating in a state where a protective sheet is pasted on one side of the porous film or laminate, for example, metal deposition on a substrate or the like is performed. Can be prevented.

  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 layer 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 applying more efficient electrolytic plating. It becomes.

  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 and laminate of the present invention are extremely useful as a circuit board manufactured by a method of directly forming fine wiring on the porous film surface. 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 or laminate of the present invention is used, it is possible to form fine wiring firmly entangled with the porous film, and to form wiring easily with high precision using an exposure technique. be able to. Single-sided wiring can be formed in a laminate having a porous film on one side, and double-sided wiring can be formed in a laminate having a porous film on both sides. When via wiring connecting both surfaces is required, a hole can be formed by a conventionally used drill or laser and filled by conductive paste or plating. 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 using the porous film and laminated body of this invention, sufficient intensity | strength can be ensured and the circuit board excellent in the handleability can be provided.

  The electromagnetic wave control material is used as a material that blocks (shields) or absorbs 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 electrical / electronic devices, wireless devices, systems, etc. that are close to 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, for example, by providing conductivity by a metal plating layer, and can absorb electromagnetic waves by filling the pores constituting the porous film with an electromagnetic wave absorbing material. 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 when 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. It is done. 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 and laminate of the present invention are 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 in high frequency circuits, (1) transmission signal delay due to high dielectric constant, (2) signal interference / attenuation due to high dielectric loss, power consumption Increase, and heat generation in the circuit occurs. 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 and laminate of the present invention are not only low dielectric constant characteristics, but can ensure sufficient strength for handling the porous film, and are a preferable medium as a low dielectric constant material.

  When using the porous or laminate of the present invention as a low dielectric constant circuit board material, as described above, the copper foil is bonded to the surface of the porous film, and unnecessary portions of the copper foil are removed by etching. It is conceivable to manufacture by a method of forming a wiring. Although miniaturization and high density of wiring are becoming difficult, almost all circuit boards are still made by this conventional method, and the porous film and laminate 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.

  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) as described above, a printing technique will be described 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 amount can be greatly reduced, it is also true that high-definition printing that has never been required is required and is 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. In the porous film or laminate of the present invention, the fine porous structure of the porous film can absorb ink or fix the ink precisely, so that high-definition printing unprecedented can be achieved. Can be used very preferably. 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 liquid crystal displays, organic EL displays, field emission displays (FEDs), IC cards, IC tags, solar cells, LED elements, organic transistors, capacitors (capacitors), electronic paper, Examples include a flexible battery, a flexible sensor, a membrane switch, a touch panel, and an EMI shield.

  The method for manufacturing the electronic material includes a step of printing ink containing an electronic material such as a conductor, a dielectric, a semiconductor, an insulator, and a resistor on the surface of the porous film. For example, a capacitor (capacitor) can be formed by printing on the surface of the porous film 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 and laminate of the present invention are organic materials, the firing temperature is preferably relatively low in order to avoid deterioration. However, in order to reduce the electrical resistance of the wiring, it is generally fired at a high temperature. It is necessary to select and use an ink having an appropriate curing temperature. 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. 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.

  The porous membrane and laminate of the present invention can be used not only in the case where the pores of the porous membrane are left as they are, but also by losing the pore structure of the porous membrane by solvent treatment. It is also possible to use

  When the surface of the wiring is covered with a resin, if there are many fine holes having communication properties, the resin tends to enter the holes, so that the holes are filled with the resin and the holes tend 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 “Aradite” from Huntsman Advanced Materials, “Denacol” from Nagase Chemtech, “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 Company, polyamideimide resin “Vilomax” manufactured by Toyobo Co., Ltd., polyimide ink “Iupicoat” manufactured by Ube Industries, Ltd. Polyimide ink “Everrec” 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. Further, a method of dropping an appropriate amount onto the surface of the porous film layer using 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 layer, it is preferable that heat treatment is performed 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 the composite material, in addition to the case where the porous structure of the porous film is maintained, the porous film has a porous film surface after the functional film is formed (after functionalization). The case where the porous structure is made transparent by removing the pore structure with a solvent, for example, is also included.

  In the present invention, the composite material may have a configuration 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 coated with a resin by the above-described method.

  The porous film and laminate of the present invention can be used for antennas with better 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 or the laminate of the present invention, an antenna having higher frequency characteristics can be manufactured. As a manufacturing method, a subtractive method can be used. Specifically, as shown in the low dielectric constant circuit board manufacturing method, a copper foil is bonded to the surface of a porous film laminate based on a porous film or a resin film to form a resist pattern. Then, it can carry out by removing the unnecessary part of copper foil by etching. As another method, after forming a resist pattern on a porous film laminate based on a metal foil such as copper, etching can be performed by removing 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 and the laminate 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 film and laminated body of this invention can be utilized preferably for the said use.

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

  The average pore diameter, porosity, and air permeability of the micropores of the porous membrane were calculated and measured by the following methods. The average pore diameter and the 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 pores on the surface or cross section of the porous membrane 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 the circumference ratio.
Surface or internal average pore diameter [μm] = 2 × (Save / π) ^1/2

2. Porosity The porosity inside the porous membrane was calculated by 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 And a density calculated by distributing the density of each component constituting the composition by weight composition ratio).
Porosity [%] = 100-100 × W / (ρ · V)
In addition, the density of each component in the porous membrane composition used in the Example is as follows.
Density of polyamideimide (trade name “Bilomax HR-11NN”): 1.45 [g / cm ³ ]
Density of polyetherimide (trade name “Ultem 1000”): 1.27 [g / cm ³ ]
Density of titanium oxide (trade name “R-42”): 4.1 [g / cm ³ ]
Density of titanium oxide (trade name “R-45M”): 3.9 [g / cm ³ ]
Density of alumina (Al ₂ O ₃ nanopowder): 4 [g / cm ³ ]
Silica (SiO ₂ nanopowder) density: 2.4 [g / cm ³ ]
Density of barium titanate (BaTiO ₃ nanosize powder): 6.08 [g / cm ³ ]
Density of ferric oxide (Fe ₂ O ₃ nanopowder): 5.12 [g / cm ³ ]

3. 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 smaller the value of the air permeability (Gurley value), the higher the air permeability, that is, the higher the connectivity of the micropores in the porous membrane. Since the Gurley value changes in proportion to the film thickness, the value for the film thickness of 30 μm is shown here. If the Gurley value is 30 seconds / 100 cc or less, it can be determined that the micropores have high connectivity.

  In the following Examples and Comparative Examples, an easy-adhesion surface of a polyethylene terephthalate (PET) film (manufactured by Teijin DuPont, HS74AS type, thickness 100 μm) is used as a base material (casting substrate) for producing a porous film. It was.

Example 1
Polyamideimide resin solution (trade name “Vilomax HR-11NN” manufactured by Toyobo Co., Ltd .; solid content concentration 15% by weight, solvent NMP, solution viscosity 20 dPa · s / 25 ° C.) as a water-soluble polymer 30 parts by weight of polyvinylpyrrolidone (molecular weight 50,000) and 7.5 parts by weight of titanium oxide as inorganic particles (trade name “R-42” manufactured by Sakai Chemical Industry Co., Ltd., rutile type, average particle size 0.29 μm) Polyamideimide resin / NMP / polyvinylpyrrolidone / titanium oxide was mixed at a ratio of 15/85/30 / 7.5 to obtain a stock solution (dispersion) for film formation.
A PET film substrate (manufactured by Teijin DuPont, HS74AS type, thickness 100 μm) is fixed on a glass plate with a tape so that the easy-adhesion surface of the PET film is on the outside, and the stock solution at 25 ° C. is used with a film applicator Then, the film was cast under the condition of a gap of 102 μm between the film applicator and the PET film 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 PET film base material naturally. Then, the film | membrane which consists only of a porous layer was obtained by air-drying at room temperature. The thickness of the film consisting only of the obtained porous layer was 40 μm.
When this porous membrane was observed with an electron microscope, the inside of the porous membrane was almost homogeneous, and there existed micropores having a communication property with an average pore diameter of 0.5 μm over the entire area. The porosity inside the porous membrane was 76%. The content of inorganic particles in the porous membrane is 33.3% by weight. An electron micrograph (SEM photograph) of the surface of the obtained porous membrane is shown in FIG. In FIG. 1, black portions are holes, gray portions are resins, and white portions are titanium oxide particles.

Example 2
Polyetherimide resin (trade name “Ultem 1000” manufactured by SABIC Innovative Plastics), N-methyl-2-pyrrolidone (NMP) as a solvent, and the weight ratio of polyetherimide resin / NMP is 18/82. A polyetherimide resin solution was prepared by mixing at a ratio. In this liquid, 30 parts by weight of polyvinyl pyrrolidone (molecular weight 50,000) as a water-soluble polymer and titanium oxide as inorganic particles (trade name “R-45M” manufactured by Sakai Chemical Industry Co., Ltd., rutile type, average particle size 0. 29 μm) 9 parts by weight are mixed in a ratio such that the weight ratio of polyetherimide resin / NMP / polyvinylpyrrolidone / titanium oxide is 18/82/30/9 to obtain a stock solution (dispersion) for film formation It was.
A PET film substrate (manufactured by Teijin DuPont, HS74AS type, thickness 100 μm) is fixed on a glass plate with a tape so that the easy-adhesion surface of the PET film is on the outside, and the stock solution at 25 ° C. is used with a film applicator Then, the film was cast under the condition of a gap of 102 μm between the film applicator and the PET film 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 PET film base material naturally. Then, the film | membrane which consists only of a porous layer was obtained by air-drying at room temperature. The thickness of the film made of only the obtained porous layer was 35 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 1 μm over the entire area. The porosity inside the porous membrane was 78%. The content of inorganic particles in the porous membrane is 33.3% by weight.

Example 3
Titanium oxide (trade name “R-42” manufactured by Sakai Chemical Industry Co., Ltd., rutile type, average particle size 0.29 μm) is used as inorganic particles, and weight of polyetherimide resin / NMP / polyvinylpyrrolidone / titanium oxide in the stock solution Except that the ratio was 18/82/20/9, the same operation as in Example 2 was performed to obtain a film consisting only of a porous layer. The thickness of the film made only of the obtained porous layer was 37 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 1 μm over the entire area. The porosity inside the porous membrane was 74%. The content of inorganic particles in the porous membrane is 33.3% by weight.

Example 4
Titanium oxide (trade name “R-42” manufactured by Sakai Chemical Industry Co., Ltd., rutile type, average particle size 0.29 μm) is used as inorganic particles, and weight of polyetherimide resin / NMP / polyvinylpyrrolidone / titanium oxide in the stock solution Except that the ratio was 18/82/20/18, the same operation as in Example 2 was performed to obtain a film consisting of only a porous layer. The thickness of the film consisting only of the obtained porous layer was 40 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 1 μm over the entire area. The porosity inside the porous membrane was 70%. The content of inorganic particles in the porous membrane is 50% by weight.

Example 5
Titanium oxide (trade name “R-42” manufactured by Sakai Chemical Industry Co., Ltd., rutile type, average particle size 0.29 μm) is used as inorganic particles, and weight of polyetherimide resin / NMP / polyvinylpyrrolidone / titanium oxide in the stock solution Except that the ratio was 18/82/20/27, the same operation as in Example 2 was performed to obtain a film consisting only of the porous layer. The thickness of the film made of only the obtained porous layer was 56 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 1 μm over the entire area. The porosity inside the porous membrane was 66%. The content of inorganic particles in the porous membrane is 60% by weight.

Example 6
Titanium oxide (trade name “R-42” manufactured by Sakai Chemical Industry Co., Ltd., rutile type, average particle size 0.29 μm) is used as inorganic particles, and weight of polyetherimide resin / NMP / polyvinylpyrrolidone / titanium oxide in the stock solution Except that the ratio was 18/82/20/42, the same operation as in Example 2 was performed to obtain a film consisting only of a porous layer. The thickness of the film made of only the obtained porous layer was 41 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 2 μm over the entire area. The porosity inside the porous membrane was 64%. The content of inorganic particles in the porous membrane is 70% by weight. An electron micrograph (SEM photograph) of the surface of the obtained porous membrane is shown in FIG. In FIG. 2, black portions are holes, gray portions are resins, and white portions are titanium oxide particles.

Example 7
Titanium oxide (trade name “R-42” manufactured by Sakai Chemical Industry Co., Ltd., rutile type, average particle size 0.29 μm) is used as inorganic particles, and weight of polyetherimide resin / NMP / polyvinylpyrrolidone / titanium oxide in the stock solution Except that the ratio was 18/82/20/72, the same operation as in Example 2 was performed to obtain a film consisting of only a porous layer. The thickness of the film made of only the obtained porous layer was 57 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 1 μm over the entire area. The porosity inside the porous membrane was 63%. The content of inorganic particles in the porous membrane is 80% by weight.

Example 8
Titanium oxide (trade name “R-42” manufactured by Sakai Chemical Industry Co., Ltd., rutile type, average particle size 0.29 μm) is used as inorganic particles, and weight of polyetherimide resin / NMP / polyvinylpyrrolidone / titanium oxide in the stock solution Except that the ratio was 18/82/20/102, the same operation as in Example 2 was performed to obtain a film consisting only of a porous layer. The thickness of the film made of only the obtained porous layer was 46 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 1 μm over the entire area. The porosity inside the porous membrane was 64%. The content of inorganic particles in the porous membrane is 85% by weight.

Example 9
Alumina (Aldrich, Al ₂ O ₃ nanopowder, average particle size of 50 nm or less) was used as the inorganic particles, and the weight ratio of polyetherimide resin / NMP / polyvinylpyrrolidone / alumina in the stock solution was 18/82/20/27. Except for the above, the same operation as in Example 2 was performed to obtain a film consisting of only a porous layer. The thickness of the film consisting only of the obtained porous layer was 60 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 1 μm over the entire area. The porosity inside the porous membrane was 69%. The content of inorganic particles in the porous membrane is 60% by weight.

Example 10
Silica (manufactured by Aldrich, SiO ₂ nanopowder, average particle size 15 nm) was used as the inorganic particles, and the weight ratio of polyetherimide resin / NMP / polyvinylpyrrolidone / silica in the stock solution was 18/82/20/9. Except for the above, the same operation as in Example 2 was performed to obtain a film consisting of only a porous layer. The thickness of the film made of only the obtained porous layer was 53 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 3 μm over the entire area. The porosity inside the porous membrane was 63%. The content of inorganic particles in the porous membrane is 33.3% by weight.

Example 11
Barium titanate (manufactured by Aldrich, BaTiO ₃ nanosize powder, average particle size 40 nm) was used as the inorganic particles, and the weight ratio of polyetherimide resin / NMP / polyvinylpyrrolidone / barium titanate in the stock solution was 18/82/20. Except that it was set to / 27, the same operation as Example 2 was performed, and the film | membrane which consists only of a porous layer was obtained. The thickness of the film made of only the obtained porous layer was 58 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 1 μm over the entire area. The porosity inside the porous membrane was 72%. The content of inorganic particles in the porous membrane is 60% by weight.

Example 12
Ferric oxide (Aldrich, Fe ₂ O ₃ nanopowder, average particle diameter of 50 nm or less) is used as the inorganic particles, and the weight ratio of polyetherimide resin / NMP / polyvinylpyrrolidone / ferric oxide in the stock solution is 18 Except for setting to / 82/20/27, the same operation as in Example 2 was performed to obtain a film consisting of only a porous layer. The thickness of the film made of only the obtained porous layer was 58 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 2 μm over the entire area. The porosity inside the porous membrane was 72%. The content of inorganic particles in the porous membrane is 60% by weight.

Comparative Example 1
The same procedure as in Example 2 was carried out except that the weight ratio of polyetherimide resin / NMP / polyvinylpyrrolidone in the stock solution was 18/82/20 without using inorganic particles, and a membrane consisting only of a porous layer was obtained. Obtained. The thickness of the film made of only the obtained porous layer was 36 μm.
When this porous film was observed with an electron microscope, the inside of the porous film was almost homogeneous, and there existed micropores having an average pore diameter of 3 μm over the entire area. The porosity inside the porous membrane was 73%. The content of inorganic particles in the porous membrane is 0% by weight.

Example 13
Polyetherimide resin (trade name “Ultem 1000” manufactured by SABIC Innovative Plastics), N-methyl-2-pyrrolidone (NMP) as a solvent, and the weight ratio of polyetherimide resin / NMP is 18/82. A polyetherimide resin solution was prepared by mixing at a ratio. In this liquid, 27 parts by weight of titanium oxide as inorganic particles (trade name “CR-50” manufactured by Ishihara Sangyo Co., Ltd., rutile type, average particle diameter of 0.25 μm) is added to polyetherimide resin / NMP / titanium oxide. Mixing was performed at a ratio of 18/82/27 by weight to obtain a stock solution (dispersion) for film formation.
A PET film substrate (manufactured by Teijin DuPont, HS74AS type, thickness 100 μm) is fixed on a glass plate with a tape so that the easy-adhesion surface of the PET film is on the outside, and the stock solution at 25 ° C. is used with a film applicator Then, the film was cast under the condition of a gap of 51 μm between the film applicator and the PET film 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 PET film base material naturally. Then, the film | membrane which consists only of a porous layer was obtained by air-drying at room temperature. The thickness of the film made of only the obtained porous layer was 28 μm.
When the cross section of the porous membrane was observed with an electron microscope, the inside of the porous membrane was almost homogeneous and there existed micropores with poor average connectivity having an average pore diameter of 1.5 μm over the entire area. The porosity inside the porous membrane was 60%. The content of inorganic particles in the porous membrane is 60% by weight.

[Evaluation test]
<Air permeability test>
Test 1
When the air permeability of the porous film containing 60% by weight of titanium oxide obtained in Example 5 was measured, the Gurley value was 4 seconds / 100 cc.
For comparison, when the air permeability of the porous film containing no inorganic particles obtained in Comparative Example 1 was measured, the Gurley value was 3 seconds / 100 cc.
From this, it can be seen that the porous film containing 60% by weight of titanium oxide has the same pores as the porous film containing no inorganic particles, and titanium oxide almost completely inhibits the connectivity. It was confirmed that they did not.

Test 2
When the air permeability of the porous membrane containing 60% by weight of titanium oxide obtained in Example 13 was measured, the Gurley value was 4000 seconds or more (second measurement limit) / 100 cc.
From this, it was confirmed that the air permeability of the porous membrane of Example 13 containing titanium oxide was poor and the connectivity of the micropores in the porous layer was low.

<Visual observation of whiteness during liquid immersion>
Test 1
The porous membrane containing 60% by weight of titanium oxide obtained in Example 5 was formed into a size of 5 cm × 5 cm and immersed in ion-exchanged water placed in a glass petri dish for 10 seconds. A sample was removed and placed on a black desk. For comparison, the same operation was performed on the porous film containing no titanium oxide of Comparative Example 1. Then, these samples were visually observed.
As a result, the sample of Example 5 remained white with almost no change in the degree of white before and after immersion in ion-exchanged water. On the other hand, the sample of Comparative Example 1 was white before immersion, but after immersion, the film became slightly transparent and the blackness of the desk was felt. From this, it was confirmed that the porous membrane containing titanium oxide has higher characteristics of maintaining white color than the porous membrane not containing titanium oxide even when immersed in ion-exchanged water.

Test 2
A porous film containing 60% by weight of titanium oxide obtained in Example 5 was formed into a size of 5 cm × 5 cm, and immersed in n-dodecane placed in a glass petri dish for 10 seconds. A sample was removed and placed on a black desk. For comparison, the same operation was performed on the porous film containing no titanium oxide of Comparative Example 1. Then, these samples were visually observed.
As a result, the sample of Example 5 remained white with almost no change in the degree of white before and after the n-dodecane immersion. On the other hand, the sample of Comparative Example 1 was white before immersion, but after immersion, the film became slightly transparent and the blackness of the desk was felt. From this, it was confirmed that the porous film containing titanium oxide has higher characteristics of maintaining the white color than the porous film not containing titanium oxide even when immersed in n-dodecane.

Claims (11)

A porous membrane having a large number of micropores, wherein the porous membrane is composed of a composition containing a polymer and inorganic particles, and the polymer comprises a polyamideimide resin, a polyetherimide resin, It is at least one selected from the group consisting of an ether sulfone resin, a cellulose resin and a polysulfone resin, and the average pore diameter of the micropores in the porous membrane is 0.01 to 10 μm, and the porosity is 30 to 85%. There, air permeability indicating the communication of the micropores, 0.2-30 sec / 100 cc der Gurley value for the film thickness 30μm is, the inorganic particles are titanium oxide particles, silica particles, alumina particles, titanate Barium particles, barium sulfate particles, indium tin oxide particles, zirconium oxide particles, copper oxide particles, iron oxide particles, magnetic powder, carbon particles and carbon nanotubes A porous membrane which is at least one selected from the group consisting of the inorganic particles in the porous membrane and has a content of 20 to 90% by weight . The porous membrane according to claim 1, wherein the average particle size of the primary particles of the inorganic particles is 0.01 to 10 μm. The porous membrane according to claim 1, wherein the porous membrane has a thickness of 5 to 200 μm. The porous membrane is obtained by casting a porous film-forming material dispersion liquid containing the polymer and inorganic particles constituting the porous film in the form of a film on a substrate, and thereafter, The film-like porous layer formed by being immersed in the substrate, peeled off from the substrate, and then dried by subjecting the film-like porous layer to drying. The porous membrane as described. A method for producing a porous film according to any one of claims 1 to 4, wherein a porous film-forming material dispersion liquid comprising a polymer and inorganic particles constituting the porous film is formed on a substrate. The film-like porous layer is cast into a film, and then immersed in a coagulation solution, the formed film-like porous layer is peeled off from the substrate, and then the film-like porous layer is dried. A method for producing a membrane. After the porous film-forming material dispersion is cast into a film on a substrate, it is kept for 0.2 minutes or more in an atmosphere having a relative humidity of 70 to 100% and a temperature of 15 to 100 ° C., and then solidified. The manufacturing method of the porous membrane of Claim 5 immersed in a liquid. It is a laminated body which has a base material and the porous membrane layer containing the inorganic particle provided on the at least single side | surface of the said base material, Comprising: The said porous membrane layer is any one of Claims 1-4. A laminate comprising the porous film described in 1. A method for producing a laminate according to claim 7, wherein a porous film-forming material dispersion containing a polymer and inorganic particles that constitute the porous film is cast onto a substrate in the form of a film, Then, the manufacturing method of the laminated body including immersing this in a coagulation liquid and giving to drying then. After casting the porous film-forming material dispersion on a substrate in the form of a film, it is kept for 0.2 minutes or more in an atmosphere having a relative humidity of 70 to 100% and a temperature of 15 to 100 ° C. The manufacturing method of the laminated body of Claim 8 immersed in a coagulation liquid. At least one surface selected from the group consisting of a conductor layer, a dielectric layer, a semiconductor layer, an insulator layer, and a resistor layer on at least one surface of the porous film according to any one of claims 1 to 4. A functional laminate provided with a functional layer. A function in which at least one functional layer selected from the group consisting of a conductor layer, a dielectric layer, a semiconductor layer, an insulator layer, and a resistor layer is provided on the porous film layer surface of the laminate according to claim 7. Laminate.