JP2012055095A - Polymer composition for electret material and electret material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electret material capable of being optimally used as electrostatic induction type vibration power generation material, and polymer composition for electret material for acquiring the same.SOLUTION: The polymer composition for electret material includes a specific amount of inorganic dielectric and fluorine-containing polymer.

Description

The present invention relates to a polymer composition for electret materials and an electret material obtained using the same. More specifically, a polymer composition for electret materials that can be suitably used to form an electrostatic induction vibration power generation material, and a material formed by the composition, the electrostatic induction vibration The present invention relates to an electret material constituting an electrode on an electret electrode substrate in a power generation device.

The electret material is a charged body made of a material having dielectric properties, and in recent years, use as a so-called electrostatic induction conversion element has been proposed, and research for practical use is being started. For example, it is expected to be applied to a power generation element using electrostatic induction in which electric power is generated by generating inductive charges with an electret material in which charges are injected into an insulating material. Such a power generation element by electret type power generation can be reduced in size, and thus has been attracting attention as being suitable for a mobile electronic device that is rapidly spreading.

As a technique related to a conventional electret, an electret having a layer made of an organic-inorganic composite material containing an organic polymer and inorganic fine particles having a relative dielectric constant of 2.0 to 4.0 × 10 ³ is disclosed (for example, , See Patent Document 1). Further, as a composition similar to the composition for producing the electret material, a liquid composition for a composite dielectric containing an inorganic dielectric and a fluorinated aromatic polymer is disclosed (for example, see Patent Document 2). ).
These are materials in which an inorganic material as a dielectric is contained in a resin material. By specifying the inorganic material or the resin material, the thermal stability of the injected electric charge is increased, or a high dielectric constant is obtained. It was something to do. As described above, it is disclosed that an inorganic material and a resin material are combined to form a material having dielectric characteristics. However, the material is suitable for electret power generation, and the performance as a power generation element is put to practical use. In order to improve the quality, it is necessary to overcome various technical problems, and there is room to devise the configuration for obtaining a dielectric in the prior art.

JP 2009-253050 A (page 1-2) Republished patent WO2005 / 033209 (page 1-2)

Among electret type power generation, electrostatic induction type vibration power generation is useful as a system for generating power by efficiently using dielectric characteristics.
If the conceptual diagram of the electric power generation element for demonstrating the principle is shown, it will become like FIG. In FIG. 1, an electret electrode substrate and a counter electrode substrate are electrically connected to each other, and both the substrates are made of a conductive material (for example, a metal material). A plurality of electrodes are arranged on each electrode substrate so as to face the other electrode substrate, and the plurality of electrodes on the electret electrode substrate are made of an electret material and are disposed via an insulating layer. The plurality of electrodes on the counter electrode substrate are made of a conductive material (for example, a metal material).

In such a power generation element, when a positive charge is injected into an electrode made of an electret material, a negative dielectric charge is generated at the counter electrode. When the power generating element is vibrated, the positions of both substrates with respect to the other substrates are shifted, and in FIG. 1, the horizontal position of the counter electrode substrate is shifted with respect to the electret electrode substrate. Has been. At this time, the positive charge and the negative charge were balanced against each other, but they were not balanced due to the displacement of the positions of the electrodes. (P) occurs.
That is, the principle of electrostatic induction type vibration power generation using electret material can be (1) induction charge generation by electret material, and (2) AC generation by charge transfer by vibration power generation. Assuming that the maximum value of the vibration power generation output is the vibration power generation output (Pmax), this is proportional to the square of the surface charge density (σ) at the electrode at the time of charge injection.

The theoretical formula for deriving the surface charge density (σ) can be expressed by the following formula (1).

σ: surface charge density (mC / m ² )
ε: dielectric constant ε _o : vacuum dielectric constant (F / m)
V: Surface potential value (V)
d: Film thickness (m)
In the electret materials useful for the electrostatic induction vibration power generation as described above, there is a demand for a material design that can improve the vibration power generation output (Pmax). After research and development with three technical issues (1) high surface charge density, (2) suppression of decay over time, and (3) heat resistance, electrostatic induction vibration of electret materials made of inorganic materials and resin materials In order to realize practical use as a useful material for power generation and the like, it has been found that there is room for further improvement in the materials in the prior art, particularly in terms of high surface charge density.

The present invention has been made in view of the above-mentioned present situation, and when used as an electret electrode, it has a high surface charge density and is suitable as a resin composition for forming a power generation element material for electrostatic induction vibration power generation. It aims at providing the polymer composition for electret materials which can be used for, and the electret material obtained by this composition.

As a result of various studies on the structure of the polymer composition for electret materials, the present inventor first used an electret material composed of an inorganic material and a resin material (binder) for electrostatic induction vibration power generation, etc. In order to put it into practical use, we have found that there are several issues to overcome. Then, in the surface charge density of the electret material by the composition combining the inorganic material and the resin material, the inorganic material is related to the relative dielectric constant (ε) and the resin material is related to the surface potential value (V). In order to improve the basic performance as an electret material, it was noted that a composition containing an inorganic dielectric and a fluorine-containing polymer is suitable. In order to improve the surface charge density (σ) and achieve a high surface charge density, the content of the inorganic dielectric composition in the composition must be set higher than a specific amount, and such weight It has been found that when an electret material is produced using a combined composition, the electret material is useful for electrostatic induction vibration power generation and the like. Further, it has been found that when barium titanate is selected from various inorganic dielectrics and used as an essential element, the performance concerning the surface charge density (σ) can be remarkably increased. As described above, when barium titanate selected and specified as an inorganic dielectric is used, the electret material exhibits outstanding performance when applied to electrostatic induction vibration power generation. It has extremely great technical significance for the practical application of inductive vibration power generation.

In the technique disclosed in Patent Document 1, as an embodiment, a polymer containing a surfactant using zirconium oxide or titanium oxide as inorganic particles and an aliphatic cyclic fluoropolymer as an organic polymer (binder). A composition in which the content of inorganic particles is 1.9 to 11.3% by mass with respect to 100% by mass of the solid content of the organic-inorganic composite material by mixing the solution and the inorganic particle dispersion solution and performing an extraction operation. I am making it. And the electret is produced by apply | coating the obtained composition to a board | substrate by the spin coat method, and injecting an electric charge by corona discharge. As the physical properties of the electret thus obtained, the surface charge density was equivalent to −2.0 to −3.6 mC / m ² .
Here, in order to maintain the smoothness of the film as a thin electret material, the inorganic particles need to be very fine, but if the inorganic particles are very fine, the surface area of the inorganic particles increases. For this reason, the dispersibility of the inorganic particles in the polymer solution is significantly reduced. Therefore, in the technique disclosed in Patent Document 1, in order to disperse the inorganic particles in the polymer solution without agglomeration, the polymer solution and the inorganic particle dispersion solution are once mixed, and then the inorganic particles are mixed with the surfactant in the polymer solution. A method is used in which particles are transferred to a polymer solution in a dispersed state, and then an extraction operation is performed.

That is, the present invention is a polymer composition for electret materials comprising an inorganic dielectric and a fluorine-containing polymer, wherein the composition contains 5 wt% of the inorganic dielectric relative to 100 wt% of the solid content of the composition. It is a polymer composition for electret materials characterized by including more than weight%.
The present invention also provides a polymer composition for electret materials comprising an inorganic dielectric and a fluorine-containing polymer, wherein the inorganic dielectric essentially comprises barium titanate. It is also a composition.
The present invention is described in detail below.

The polymer composition for electret materials of the present invention contains an inorganic dielectric and a fluorine-containing polymer, and each of them may be contained in one kind or in two or more kinds. Moreover, the said polymer composition may contain the other component, as long as the inorganic dielectric and the fluorine-containing polymer are included.

In the present invention, in the polymer composition, the inorganic dielectric is contained in an amount of 5% by weight or more with respect to 100% by weight of the solid content of the composition, or barium titanate is essential as the inorganic dielectric. Depending on the use, an electret material having a high surface charge density can be produced. Therefore, among the polymer compositions for electret materials, those containing 5% by weight or more of the inorganic dielectric with respect to 100% by weight of the solid content of the composition are also referred to as the first polymer composition for electret materials of the present invention. Describe.
Moreover, what uses barium titanate as an essential thing as an inorganic dielectric material is described as the 2nd polymer composition for electret materials of this invention. And the polymer composition for 1st electret materials of this invention and the polymer composition for 2nd electret materials are match | combined, and it describes as the polymer composition for electret materials of this invention.
In the present invention, if the polymer composition corresponds to either the first polymer composition for electret materials or the second polymer composition for electret materials, the above-described effects can be obtained. A polymer composition corresponding to both the first polymer composition for electret materials and the second polymer composition for electret materials is more preferable.

First, the first polymer composition for electret materials of the present invention will be described.
The 1st polymer composition for electret materials of this invention contains 5 weight% or more of inorganic dielectrics with respect to 100 weight% of solid content of a composition. By including an inorganic dielectric within such a range, the electret material obtained using the polymer composition has a sufficiently high surface charge density. The preferred content of the inorganic dielectric is 10% by weight or more, more preferably 20% by weight or more, based on 100% by weight of the solid content of the composition. However, if the content of the inorganic dielectric becomes too high, the viscosity of the polymer composition will increase, and the handleability may decrease, or a coating film may be formed by applying the polymer composition to a substrate or the like. In such a case, the coating film may become brittle. Therefore, the content of the inorganic dielectric is preferably 99% by weight or less. More preferably, it is 96 weight% or less, More preferably, it is 93 weight% or less.

As the inorganic dielectric, those having a relative dielectric constant of 200 or more are preferable. By using an inorganic dielectric having a relative dielectric constant in such a range, the electret material obtained using the first polymer composition for electret materials of the present invention has a higher surface charge density. be able to. The relative dielectric constant of the inorganic dielectric is more preferably 400 or more, still more preferably 600 or more, and particularly preferably 800 or more.
Thus, it is also one of the suitable embodiment of the polymer composition for 1st electret materials of this invention that the dielectric constant of an inorganic dielectric material is 200 or more.

As the inorganic dielectric, an ABO ₃ type dielectric having a perovskite crystal structure and a binary or ternary composite perovskite dielectric are preferable, and titanium oxide can also be used.

The dielectric of the ABO ₃ type, for example, lead titanate PbTiO _3, lead tungstate PbWO _3, zinc, lead PbZnO _3, Tetsusan'namari PbFeO _3, magnesium lead PbMgO _3, lead niobate PbZbO _3, nickelate Lead PbNiO ₃ , lead zirconate PbZrO ₃ , barium titanate BaTiO ₃ , strontium titanate SrTiO ₃ , calcium zirconate CaZrO ₃ , calcium titanate CaTiO ₃ , zinc titanate ZnTiO ₃ , magnesium titanate ZnTiO _{3 a} , barium zirconate B a ₃ , magnesium zirconate MgZrO ₃ , zinc zirconate ZnZrO _{3 and the} like.

As the composite Perubusukaito based dielectric of the binary or ternary, for _{example, (Ba x Sr (1-} x)) (Sn y Ti (1-y)) O 3, Ba (Ti x Sn (1- _x) ) O ₃ , Ba _x Sr _(1-x) TiO ₃ , BaTiO ₃ —CaZrO ₃ , BaTiO ₃ —Bi ₄ Ti ₃ O ₁₂ , (Ba _x Ca _(1-x) ) (Zr _y TiO _{(1- y)} ) O _{3 and the} like.

Among the above-described inorganic dielectrics, barium titanate is more preferable.
The barium titanate in the present invention is preferably a compound referred to as barium titanate composed of a titanium atom, a barium atom, and an oxygen atom such as BaTiO ₃ , BaTiO ₃ —Bi ₄ Ti ₃ O _12. Any compound may be used as long as these atoms are essential. That is, as long as it has an inorganic compound structure that essentially includes a titanium atom, a barium atom, and an oxygen atom, it may have other atoms. A suitable form for electrostatic induction vibration power generation or the like is to obtain a relative dielectric constant (ε) that can be evaluated as equivalent to barium titanate such as BaTiO ₃ , BaTiO ₃ —Bi ₄ Ti ₃ O _12, etc. It is an inorganic compound that can essentially contain a titanium atom, a barium atom, and an oxygen atom.

Examples of the shape of the inorganic dielectric include particles, fibers, flakes, and cones.
The average particle size of the inorganic dielectric is appropriately selected in consideration of the thickness of the electret material obtained using the polymer composition. When used as a thin film, the average particle size is 0.01 to 10 μm. It is preferably within the range, more preferably within the range of 0.1 to 5 μm, and most preferably within the range of 0.5 to 3 μm. The specific surface area per volume of the inorganic dielectric is ^preferably in the range of 1m ² / g~10m 2 / ^g, more preferably in the range of ^{2m 2 / g~8m 2 / g,} 2m 2 / g~5m Most preferably within the range of ² / g.

Next, the second polymer composition for electret materials of the present invention will be described.
In the second polymer composition for electret materials of the present invention, the inorganic dielectric material is essentially composed of barium titanate.

The content of the inorganic dielectric in the second polymer composition for electret materials of the present invention is preferably 5 to 99% by weight with respect to 100% by weight of the solid content of the composition. When the content of the inorganic dielectric is less than 5% by weight, the electret material obtained using the polymer composition may not have a sufficiently high surface charge density. On the other hand, if an inorganic dielectric having a content exceeding 99% by weight is included in the polymer composition, the viscosity of the polymer composition may increase, and the handleability may decrease. When a coating film is formed by coating on a substrate or the like, the coating film may become brittle. The content of the inorganic dielectric is more preferably 10 to 96% by weight, still more preferably 20 to 93% by weight with respect to 100% by weight of the solid content of the composition.

The shape and average particle diameter of the inorganic dielectric in the second polymer composition for electret materials of the present invention can be the same as those described above.

In the following, the contents common to the first polymer composition for electret materials and the second polymer composition for electret materials of the present invention will be described.
The fluorine-containing polymer used in the present invention preferably has a glass transition temperature (Tg) of 150 ° C. or higher. If glass transition temperature is less than 150 degreeC, there exists a possibility that the heat resistance of the electret material obtained using the polymer composition for electret materials may fall. The glass transition temperature of the fluorine-containing polymer is more preferably in the range of 150 ° C to 400 ° C, and still more preferably in the range of 170 ° C to 300 ° C.
The glass transition temperature can be measured using DSC (product name; DSC6200, manufactured by Seiko Denshi Kogyo Co., Ltd.) under a nitrogen atmosphere under a temperature increase rate of 20 ° C./min.

The surface resistance value of the fluorine-containing polymer is preferably 1.0 × 10 ¹⁵ Ω / cm ² or more. If the surface resistance value is less than 1.0 × 10 ¹⁵ Ω / cm ² , the insulating properties of the electret material obtained using the polymer composition for electret materials may be reduced. The surface resistance value of the fluorine-containing polymer is more preferably in the range of 1.0 × 10 ¹⁷ Ω / cm ² or more.
The surface resistance value can be measured using a resistance value measuring device (product name: High Resistance Meter 4329A & Resistivity Cell 16008A, manufactured by Hewlett Packard) under a measurement voltage of 500V.

The average molecular weight of the fluorine-containing polymer is preferably in the range of 5,000 to 500,000 in terms of number average molecular weight (Mn). If the number average molecular weight is less than 5,000, the heat resistance of the electret material obtained using the polymer composition for electret materials may be reduced. If the number average molecular weight exceeds 500,000, the viscosity of the polymer composition will be low. This may increase the workability. The number average molecular weight (Mn) is more preferably in the range of 10,000 to 200,000, and still more preferably in the range of 10,000 to 100,000.

The polydispersity (weight average molecular weight / number average molecular weight; Mw / Mn) of the fluorine-containing polymer is preferably in the range of 1 to 5. When Mw / Mn exceeds 5, the polymer composition may be gelled. The polydispersity (Mw / Mn) is more preferably in the range of 1 to 4.5, and still more preferably in the range of 1 to 4.
In addition, the number average molecular weight of the said fluorine-containing polymer and a weight average molecular weight are G-5000HXL + GMHXL-L as a column using a gel permeation chromatograph analyzer (GPC) (product name; HLC-8120GPC, the Tosoh company make). Using THF as a developing solvent and standard polystyrene as a standard, it can be measured under a flow rate of 1 mL / min.

The fluorine-containing polymer preferably has a fluorination rate of 7 to 80%. By using a fluorine-containing polymer having such a fluorination rate, it is considered that the interaction between the inorganic dielectric and the fluorine-containing polymer is moderately suppressed, and in producing a polymer composition for electret materials. Phenomena that cause troubles such as significant thickening, gelation, loss of fluidity, and aggregation are reduced. Therefore, it is possible to produce a polymer composition for electret materials blended with more inorganic dielectrics by an easy method such as kneading an inorganic dielectric and a fluorine-containing polymer. Not only can a high surface charge density be exhibited, but also the viscosity can be lowered, so that the electret material can be easily formed into a thin film. More preferably, it is 10-70% as a fluorination rate of the said fluorine-containing polymer, More preferably, it is 15-60%.
In addition, a fluorination rate can be calculated | required by following Numerical formula (2).

The fluorine-containing polymer includes an aromatic ring having at least one fluorine group and at least one bond selected from the group consisting of an ether bond, a ketone bond, a sulfone bond, an amide bond, an imide bond, and an ester bond. A fluorinated aromatic polymer composed of repeating units is preferred. Specific examples of such polymers include fluorine-containing polyimides, polyethers, polyetherimides, polyether ketones, polyether sulfones, polyamide ethers, polyamides, polyether nitriles, and polyesters. .

The fluorinated aromatic polymer is preferably a polymer having, as essential components, an aromatic ring having at least one fluorine group and a repeating unit containing an ether bond among the above-described ones. 1);

(In the formula, R is the same or different and represents a divalent organic chain having an aromatic ring having 1 to 150 carbon atoms. Z represents a divalent chain or a direct bond. M and m ′ are 0. It is an integer above, and m + m ′ = 1 to 8, which is the same or different and represents the number of fluorine atoms bonded to the aromatic ring, n represents the degree of polymerization, and is in the range of 2 to 5000. Preferably, it is more preferably within a range of 5 to 500.), and more preferably a polyaryl ether having a fluorine atom containing a repeating unit represented by: In addition, the repeating unit represented by the general formula (1) may be the same or different, and may have any form such as a block form or a random form.

In the general formula (1), m + m ′ is preferably in the range of 2 to 8, and more preferably in the range of 4 to 8.

In the general formula (1), the position where the ether structure moiety (—O—R—O—) is bonded to the aromatic ring is preferably bonded to the para position relative to Z.

In the general formula (1), R is a divalent organic chain, and is preferably any one of the following structural formula groups (2) or a combination thereof.
In Structural Formula Group (2), Y ^{1 to} Y ⁴ are the same or different and each represents a hydrogen atom or a substituent. The substituent represents a fluorine atom, an alkyl group, or an alkoxyl group, and one benzene ring may be the same or different and a plurality thereof may be present.

Specific examples of the more preferable form of R in the general formula (1) include organic chains represented by the following structural formula group (3).

In the general formula (1), Z represents a divalent chain or a direct bond. The divalent chain is preferably, for example, a chain represented by the following structural formula group (4).
In Structural Formula Group (4), X represents a divalent organic chain having 1 to 50 carbon atoms.

Examples of X in the structural formula group (4) include organic chains represented by the structural formula group (3). Among them, a diphenyl ether chain, a bisphenol A chain, a bisphenol F chain, and a fluorene chain are preferable.

As a method for synthesizing the fluorine-containing polymer used in the present invention, a general polymerization reaction may be used, and examples thereof include condensation polymerization, addition polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. What is necessary is just to set reaction conditions, such as reaction temperature and reaction time in the case of the said polymerization reaction, suitably. Moreover, it is preferable to perform the said polymerization reaction in nitrogen atmosphere.

For example, when synthesizing a polyaryl ether having a fluorine atom containing a repeating unit represented by the general formula (1), Z is (4-6) in the structural formula group (4). Furthermore, when obtaining a polyaryl ether having a fluorine atom in which X is a diphenyl ether chain, 4,4′-bis (2,3,4,5,6-pentafluoro in an organic solvent in the presence of a basic compound. And a method of heating benzoyl) diphenyl ether (hereinafter referred to as “BPDE”) and a divalent phenol compound.

As reaction temperature in said synthesis method, the inside of the range of 20 to 150 degreeC is preferable, and the inside of the range of 50 to 120 degreeC is further more preferable.

Examples of the organic solvent used in the synthesis method include polar solvents such as N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide and methanol, and aromatic solvents such as toluene.

Examples of the basic compound used in the above synthesis method include potassium carbonate, lithium carbonate, potassium hydroxide and the like.

In the above synthesis method, examples of the divalent phenol compound include 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoropropane (hereinafter referred to as “6FBA”). ), Bisphenol A (hereinafter referred to as “BA”), 9,9-bis (4-hydroxyphenyl) fluorene (hereinafter referred to as “HF”), bisphenol F, hydroquinone, resorcinol and the like.

The amount of the divalent phenol compound used is in the range of 0.8 to 1.2 mol per mol of 4,4′-bis (2,3,4,5,6-pentafluorobenzoyl) diphenyl ether. Is preferable, and the range of 0.9 to 1.1 mol is more preferable.

In the above synthesis method, after completion of the reaction, the solvent is removed from the reaction solution, and the distillate is washed as necessary to obtain a fluorine-containing polymer. Alternatively, the reaction solution can be added to a solvent having a low solubility of the fluorine-containing polymer to precipitate the polymer, and the precipitate can be separated by filtration.

It is preferable to mix | blend a solvent with the polymer composition for electret materials of this invention for the purpose of the improvement of a moldability or film formability, and a viscosity control.

Examples of the solvent include aromatic solvents such as toluene, xylene, nitrobenzene, and benzonitrile, ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, cyclopentanone, and isobutyl ketone, methanol, ethanol, and N-methyl-2-pyrrolidone. (NMP), N, N-dimethylacetamide, acetonitrile and the like.
Moreover, in order to improve the stability of the polymer composition for electret materials, to adjust drying property, or to improve the physical property of a molding and a molding film, you may use the mixed solvent which used several solvents together.

The blending amount of the solvent is preferably in the range of 1 to 70% by mass with respect to 100% by mass of the total amount of the polymer composition. If the amount of the solvent is less than 1% by mass, the viscosity of the polymer composition is not sufficiently reduced, and the moldability may be lowered. Moreover, when it exceeds 70 mass%, there exists a possibility that a solvent may remain in the obtained electret material and performance may fall. The blending amount of the solvent is more preferably in the range of 2% by mass to 60% by mass, and still more preferably in the range of 3% by mass to 50% by mass with respect to 100% by mass of the total amount of the polymer composition.

The polymer composition for electret materials of the present invention may contain other compounds and auxiliary materials as necessary. Examples of the other compounds and auxiliary materials include polyamide resins, polyamideimide resins, epoxy resins, phenol resins, fluororesins, inorganic fillers such as silica, alumina, aluminum hydroxide, glass, graphite, and silane cups. Examples thereof include a ring agent, a titanate coupling agent, a flame retardant, an antioxidant, a plasticizer, a leveling agent, a repellency inhibitor, and a dispersant.

In the polymer composition for electret materials of the present invention, the compounding amount of the above-mentioned other compounds and auxiliary materials may be within a range that does not impair the effects of the invention. The range of 001 mass parts to 500 mass parts is preferable.

Among those described above, a mode in which a dispersant is contained in the polymer composition for electret materials of the present invention is also one of the preferred embodiments of the present invention. Examples of the dispersant include acid group-containing dispersants such as carboxylic acid groups, sulfonic acid groups, and phosphoric acid groups; nonionic dispersants such as polyoxyethylene alkyl ethers and glycerin fatty acid esters; alkylamine salts, quaternary grades Cationic dispersants such as ammonium salts; amphoteric dispersants such as alkylbetaines and alkylamine oxides can be used. Among these, preferable examples include BYK-W9010, BYK-W995, and BYK-W996 (all manufactured by Big Chemie Japan).

The method of molding the electret material obtained using the polymer composition for electret materials of the present invention is appropriately selected depending on the required shape of the electret material. For example, wet coating, press molding, vapor deposition, CVD (chemical) Vapor phase growth), drive process methods such as sputtering, and the like. Among these, when the electret material is used as a thin layer (thin film), the wet coating method is preferable from the viewpoint of the film forming process.

The above wet coating methods include casting, water casting, dipping coating, spin coating, roll coating, spray coating, die coating, bar coating, ink jet, Langmuir / Blodget, letterpress printing, gravure printing, lithographic printing, screen printing, flexographic printing. And the like. Among these, a casting method, a spin coating method, and a bar coating method are preferable.
By the method as described above, for example, after a polymer composition for electret materials is applied on a substrate to form a coating film, the solvent can be dried to form a thin layer. Thus, electret material can be produced by injecting electric charge into a layer (hereinafter referred to as “composite material layer”) formed from the polymer composition for electret material.
Such an electret material obtained using the polymer composition for electret materials of the present invention is also one aspect of the present invention.
Furthermore, as described above, there is a method for producing an electret material from a polymer composition for electret materials comprising an inorganic dielectric and a fluorine-containing polymer, wherein the production method comprises an inorganic dielectric and a fluorine-containing polymer. And a method for producing an electret material comprising a step of preparing a polymer composition by kneading the composition, a step of coating the obtained polymer composition on a substrate, and a step of injecting charges. One.

The substrate is not particularly limited as long as it can be connected to the ground when injecting charges into the coating film obtained by applying the polymer composition. Examples of the substrate material include gold, Examples thereof include conductive metals such as platinum, copper, aluminum, chromium, and nickel. Further, the material may be an insulating material other than a conductive metal, for example, a semiconductor material such as silicon, an inorganic material such as glass, an organic polymer material such as polyethylene terephthalate, polyimide, polycarbonate, and acrylic resin. As long as the surface is coated with a metal film by a method such as sputtering, vapor deposition or wet coating, it can be used.
Note that the substrate may be peeled off after the charge injection.

When the electret material of the present invention is used as a thin layer (thin film), the thickness of the composite material layer is preferably in the range of 0.1 to 100 μm, and more preferably in the range of 0.5 to 50 μm.

The electret material of the present invention has a composite material layer, but may have other layers as long as it has a composite material layer. The other layer is a layer that can be laminated with the composite material layer, and examples thereof include a protective layer, a layer made of only the fluorine-containing polymer, and a layer made of an inorganic material similar to the inorganic dielectric.

The relative dielectric constant of the composite material layer is preferably in the range of 5 to 10,000. If the relative dielectric constant is less than 5, the obtained electret material may have a low capacity for accumulating charges as the electret material. The relative dielectric constant is more preferably within the range of 10 to 10,000, and still more preferably within the range of 15 to 10,000.
The relative dielectric constant can be measured together with the dielectric loss tangent, using an impedance analyzer (product name “HP4294A” manufactured by Hewlett Packard Co., Ltd.) as in the examples described later.

In the charge injection step, the method of injecting charges into the composite material layer is not particularly limited as long as it is generally a method of charging an insulator. For example, a belt conveyor type corona discharge method, a stationary corona discharge method, and the like. And electron beam collision method, ion beam collision method, radiation irradiation method, light irradiation method, contact charging method, liquid contact charging method and the like. Among these, the belt conveyor type corona discharge method and the electron beam collision method are preferable from the viewpoints of workability and productivity.

In the charge injection step, the temperature at which the charge is injected is preferably equal to or higher than the glass transition temperature of the fluorine-containing polymer contained in the polymer composition. By setting it as such a temperature range, the stability of the electric charge hold | maintained at an electret material after electric charge injection | pouring can be improved. More preferably, the temperature at the time of injecting the charge is a temperature 10 to 20 ° C. higher than the glass transition temperature of the fluorine-containing polymer.
In addition, the voltage applied when injecting the charge is preferably applied at a high voltage within a range equal to or lower than the dielectric breakdown voltage of the composite material layer. In the composite material layer in the present invention, it is more preferably −6 to −30 kV, and further preferably −8 to −15 kV.

The electret material of the present invention is obtained by using the polymer composition for electret materials of the present invention, and is therefore a material having a very high surface charge density. The surface charge density of the electret material is preferably 5 to 200 mC / m ² in absolute value. An electret material having a surface charge density in such a range can be said to be a material having a very high surface charge density. The surface charge density is more preferably 8 to 200 mC / m ² , and further preferably 10 to 200 mC / m ² .
The surface charge density was measured by measuring the surface potential using a surface potentiometer (product name; S-211, manufactured by Kawaguchi Electric Co., Ltd.), as described in the examples described later. The following mathematical formula (1);

(In the formula, σ represents a surface charge density (mC / m ² ), ε represents a relative dielectric constant, ε _o represents a vacuum dielectric constant (F / m), and V represents a surface potential value ( V), and d represents the film thickness (m)).

The electret material of the present invention is useful as a power generation element for electrostatic induction vibration power generation among electret type power generation.
The configuration and the like are as described above with reference to FIG. That is, the electret electrode substrate and the counter electrode substrate are electrically connected to each other, and both the substrates are electrostatic induction vibration power generation elements made of a conductive material, and the other electrode substrate is placed on each electrode substrate. A plurality of electrodes are arranged so as to face each other, and the plurality of electrodes on the electret electrode substrate are made of an electret material and are disposed through an insulating layer, and the plurality of electrodes on the counter electrode substrate have conductivity. It is comprised by the material which has. Examples of the conductive material include metal materials usually used for substrates and electrodes.

In the electrostatic induction vibration power generation element, as described above, the electret material is opposed to the metal electrode, and one of them is vibrated along the other to generate an induced charge. Can be generated. In such electrostatic induction type vibration power generation, the vibration power output correlates with the surface charge density of the electret material. Therefore, since the electret material of the present invention is a material having a very high surface charge density as described above, it can be suitably used as a material for electrostatic induction vibration power generation.
The electrostatic induction vibration power generation material obtained using the polymer composition for electret materials of the present invention is also one aspect of the present invention.
In this specification, the electret material and the electrostatic induction vibration power generation material are members constituting an electret power generation element obtained from the polymer composition for the electret material, preferably the electret electrode or the like. Can be mentioned.

The polymer composition for electret materials of the present invention has the above-described configuration, and when an electret material is produced using such a polymer composition, a material having a very high surface charge density can be produced. It is useful as a raw material for electret materials that can be suitably used as a material for electrostatic induction vibration power generation.

FIG. 1 is a conceptual diagram of a power generation element showing an outline of the principle of electrostatic induction vibration power generation.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “mass%”.

In the following Examples and Comparative Examples, analysis and evaluation were performed as follows.
<Glass transition temperature of fluorine-containing polymer>
The glass transition temperature of the fluorine-containing polymer was measured with the following apparatus and measurement conditions.
Measuring device: DSC (product name: DSC6200, manufactured by Seiko Electronics Co., Ltd.)
Measurement conditions Atmosphere: Temperature rise rate under nitrogen atmosphere: 20 ° C / min

<Number average molecular weight (Mn) of fluorine-containing polymer>
The number average molecular weight of the fluorine-containing polymer was measured with the following apparatus and measurement conditions.
Measuring device: Gel permeation chromatograph (GPC) (Product name: HLC-8120GPC, manufactured by Tosoh Corporation)
Measurement condition column: G-5000HXL + GMHXL-L (product name, manufactured by Tosoh Corporation)
Developing solvent: Tetrahydrofuran (THF)
Standard: Standard polystyrene (manufactured by Tosoh Corporation)
Flow rate: 1 mL / min

<Surface resistance value of fluorine-containing polymer>
The surface resistance value of the fluorine-containing polymer was measured with the following apparatus and measurement conditions.
Measuring device: Resistance measuring device (product name: High Resistance Meter 4329A & Resistivity Cell 16008A, manufactured by Hewlett Packard)
Measurement conditions Measurement voltage: 500V

(Synthesis Example 1)
A reactor equipped with a thermometer, a cooling pipe, a gas introduction pipe, and a stirrer was charged with 16.74 parts of BPDE, 10.5 parts of HF, 4.34 parts of potassium carbonate, and 90 parts of dimethylacetamide. The mixture was heated to 60 ° C. and reacted for 5 hours. After completion of the reaction, the reaction solution was poured into a 1% aqueous acetic acid solution with vigorous stirring with a blender. The precipitated reaction product was separated by filtration, washed with distilled water and methanol, and then dried under reduced pressure to obtain a fluorine-containing polymer (1). The fluorine-containing polymer (1) had a glass transition temperature (Tg) of 242 ° C., a number average molecular weight (Mn) of 70,770, and a surface resistance value of 1.0 × 10 ¹⁸ Ω / cm ² or more.

Example 1
As a composite liquid composition, 10 parts of a fluorine-containing polymer (1), 90 parts of toluene as an organic solvent, 0.7 parts of BYK-W9010 (manufactured by Big Chemie Japan) as a dispersant, and barium titanate (as an inorganic dielectric) The average particle size: 0.5 μm, the specific surface area: 2.2 m ² / g) were blended in the order of 70 parts and mixed uniformly by a chemistor to obtain a liquid polymer composition 1.
Next, release paper was spread on a glass plate with double-sided tape, and the liquid polymer composition 1 was coated thereon with a bar coater. After drying at room temperature for 30 minutes, it was dried in a vacuum dryer at 100 ° C. for 6 hours. Thereafter, the dried coating film was peeled off from the release paper to obtain a composite film 1 having a thickness of 15 μm before charge injection.
A part of the surface of the composite film 1 was made into a platinum film by ion sputtering, and the relative dielectric constant was measured as the relative dielectric constant measuring film 1.
Furthermore, the electret film 1 for evaluation was obtained by injecting the composite film 1 with a belt conveyor type corona discharge treatment machine (product name: HFSS-101, manufactured by Kasuga Denki Co., Ltd.). The surface potential value was measured on the electret film 1 on an aluminum foil, and the surface charge density was calculated by the above formula (1).

The results are shown in Table 1.
The relative dielectric constant and the surface potential value were measured as follows.

<Relative permittivity>
The relative dielectric constant was measured under the following measurement conditions using an impedance analyzer (product name: HP4294A, manufactured by Hewlett Packard).
Measurement conditions Measurement frequency: 1 MHz

<Surface potential value>
The surface potential value was measured using a surface potentiometer (product name; S-211, manufactured by Kawaguchi Electric Co., Ltd.).

(Comparative Example 1)
As a comparative liquid composition, 10 parts of a fluorine-containing polymer (1) and 90 parts of toluene as an organic solvent were blended and mixed uniformly by a chemistor to obtain a comparative liquid polymer composition 1.
Next, a release paper was spread on a glass plate with a double-sided tape, and the comparative liquid polymer composition 1 was coated thereon with a bar coater. After drying at room temperature for 30 minutes, it was dried in a vacuum dryer at 100 ° C. for 6 hours. Thereafter, the dried coating film was peeled off from the release paper to obtain a comparative composite film 1 having a thickness of 15 μm before charge injection.
A part of the surface of the comparative composite film 1 was made into a platinum film by ion sputtering, and the relative dielectric constant was measured in the same manner as in Example 1 as the comparative dielectric constant measuring film 1.
Further, a comparative electret film 1 for evaluation was obtained by injecting the comparative composite film 1 with a belt conveyor type corona discharge treatment machine (product name: HFSS-101, manufactured by Kasuga Denki Co., Ltd.). The comparative electret film 1 was measured on the aluminum foil, the surface potential value was measured in the same manner as in Example 1, and the surface charge density was calculated by the above formula (1).
The results are shown in Table 1.

The following was found from the results of the examples.
The electret film 1 produced using the liquid polymer composition 1 is an electret film having a sufficiently high surface charge density as compared with the comparative electret film 1 produced using the comparative liquid polymer composition 1. It was confirmed. From this, the polymer composition obtained by containing an inorganic dielectric material in an amount of 5% by weight or more with respect to 100% by weight of the solid content of the composition, or using barium titanate as an essential inorganic dielectric material. It has been demonstrated that electret materials made using materials have a high surface charge density.

1: Electret material 2: Electret electrode substrate 3: Counter electrode substrate 4: Counter electrode

Claims (3)

A polymer composition for electret materials comprising an inorganic dielectric and a fluorine-containing polymer,
The polymer composition for electret materials, wherein the composition contains 5% by weight or more of an inorganic dielectric with respect to 100% by weight of the solid content of the composition. A polymer composition for electret materials comprising an inorganic dielectric and a fluorine-containing polymer,
The polymer composition for electret materials, wherein the inorganic dielectric material essentially comprises barium titanate. An electret material obtained by using the polymer composition for electret materials according to claim 1 or 2.

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