JP2015199244A - Dielectric film, film capacitor, and dielectric film manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dielectric film which achieves both increase of the dielectric constant and reduction of the dielectric loss, a film capacitor and a production apparatus for a dielectric film.SOLUTION: A dielectric film 1 includes a dielectric layer 13 containing a branched polymer 15 which contains a high-dielectric-constant polymer 16 of a relative dielectric constant at the frequency of 1 kHz of 4.0 or higher as the main chain and a low-dielectric-constant polymer 17 lower in relative dielectric constant than the high-dielectric-constant polymer 16 as a side chain and an oriented inductive layer 12 containing a linear polymer 18 which contains the high-dielectric-constant polymer as the main chain, and the branched polymer 15 contained in the dielectric layer 13 and the linear polymer 18 contained in the oriented inductive layer 12 are oriented monoaxially along the stratabound direction.

Description

  The present invention relates to a dielectric film, a film capacitor, and a dielectric film manufacturing apparatus.

  The film capacitor includes a laminated film in which a metal foil such as aluminum or a metal deposited film is laminated on a dielectric film, and such a laminated film is further laminated or wound to form a multilayer structure. Are often manufactured. As a dielectric film material for a film capacitor constituting such a laminated film, polypropylene (PP), polyethylene terephthalate (PET), polyphenylene sulfide (PPS) and the like have been generally employed.

  Since these dielectric film materials have a low relative dielectric constant of about 2.5 to 3, it is required to reduce the film thickness of the dielectric film in order to increase the capacity of the film capacitor. However, thin dielectric films have problems such as difficulty in production and poor insulation performance, and it is not always easy to reduce the thickness of dielectric films. Further, in recent years, there has been an increasing demand for miniaturization of the film capacitor, and a fundamental countermeasure for improving the dielectric constant of the dielectric film material has been demanded.

  As a technique for improving the dielectric constant of a dielectric film material, a technique using a fluorine-based resin material having a high dielectric constant such as polyvinylidene fluoride (PVDF) as a dielectric film material has attracted attention. However, when the dielectric constant of the dielectric film material is improved in this way, generally, a tendency of increasing loss of dielectric loss tangent (hereinafter referred to as dielectric loss) appears. Therefore, as a means for reducing dielectric loss in a dielectric film material having a high dielectric constant such as a fluorine resin material, polyethyl methacrylate (PEMA) is added to the main chain of a high dielectric constant polymer made of a PVDF copolymer. A method using a composite polymer material obtained by graft polymerization using a low dielectric constant polymer made of a polymer or the like as a side chain has been studied (see Non-Patent Document 1).

J. Mater. Chem., 22, 23468-23476 (2012).

  In order to increase the capacity of the film capacitor, it is necessary to take measures to achieve both an increase in dielectric constant and a reduction in loss of dielectric loss tangent in consideration of ensuring voltage resistance. In Non-Patent Document 1, although means for suppressing dielectric loss in a dielectric film has been studied, there is a demand for a dielectric film that exhibits a higher dielectric constant and further reduced dielectric loss.

  Therefore, an object of the present invention is to provide a dielectric film, a film capacitor, and a dielectric film manufacturing apparatus that achieve both increase in dielectric constant and reduction in dielectric loss.

  In order to solve the above problems, the dielectric film according to the present invention has a high dielectric constant polymer having a relative dielectric constant of 4.0 or more at a frequency of 1 kHz as a main chain, and has a relative dielectric constant higher than that of the high dielectric constant polymer. A dielectric layer comprising a branched polymer having a low dielectric constant polymer having a small side chain as a side chain, and an alignment-inducing layer comprising a linear polymer having the high dielectric constant polymer as a main chain; The branched polymer contained in the dielectric layer and the linear polymer contained in the orientation-inducing layer are uniaxially oriented along the layering direction. .

  The film capacitor according to the present invention has a high dielectric constant polymer having a relative dielectric constant of 4.0 or more at a frequency of 1 kHz as a main chain, and has a low dielectric constant and a high relative dielectric constant smaller than that of the high dielectric constant polymer. A dielectric layer comprising a branched polymer having a molecule as a side chain; an alignment-inducing layer comprising a linear polymer having a high dielectric constant polymer as a main chain; and the dielectric layer; A dielectric layer comprising a branching polymer contained in the dielectric layer and a linear polymer contained in the orientation-inducing layer uniaxially oriented along the layering direction. And a pair of first and second electrodes electrically connected to the dielectric film.

  The dielectric film manufacturing apparatus according to the present invention includes a dielectric layer comprising a branched polymer having a high dielectric constant polymer as a main chain and a low dielectric constant polymer as a side chain; An alignment-inducing layer comprising a linear polymer having a dielectric constant polymer as a main chain, the branched polymer contained in the dielectric layer, and the linear polymer contained in the alignment-inducing layer A dielectric film manufacturing apparatus that manufactures a dielectric film in which a linear polymer is uniaxially oriented along the layering direction, and presses the block including the linear polymer onto the substrate Means for sweeping the pressure-bonded substrate to form the alignment-inducing layer in which the linear polymer is uniaxially oriented along the layering direction; and the branch on the surface of the alignment-inducing layer. The branched polymer is uniaxially oriented in the same direction as the linear polymer. Characterized in that it comprises a coating means for forming the dielectric layer.

  According to the present invention, it is possible to provide a dielectric film, a film capacitor, and a dielectric film manufacturing apparatus that achieve both increase in dielectric constant and reduction in dielectric loss.

It is the schematic which shows the dielectric film which concerns on one Embodiment of this invention. (A) is sectional drawing which shows the layer structure of a dielectric film, (b) is a conceptual diagram which shows the state of a dielectric material layer, (c) is a conceptual diagram which shows the state of an orientation induction layer. It is a figure which shows the concept of the orientation state of a branched polymer contained in the dielectric film which concerns on this embodiment, and a polarization state. It is the schematic which shows the dielectric material film which concerns on a comparative example. (A) is sectional drawing which shows the layer structure of a dielectric film, (b) is a conceptual diagram which shows the state of a dielectric material layer. It is the schematic which shows the structure of the dielectric material film manufacturing apparatus which concerns on this embodiment. It is the schematic which compared the size of the converter to which the film capacitor which concerns on this embodiment is applied with the size of the power converter provided with the film capacitor which concerns on a comparative example. It is a figure which shows the relationship between the dielectric constant and dielectric loss of the dielectric film which concerns on an Example, and the dielectric film which concerns on a comparative example.

  Hereinafter, a dielectric film, a film capacitor, and a dielectric film manufacturing apparatus according to an embodiment of the present invention will be described.

  FIG. 1 is a schematic view showing a dielectric film according to an embodiment of the present invention. (A) is sectional drawing which shows the layer structure of a dielectric film, (b) is a conceptual diagram which shows the state of a dielectric material layer, (c) is a conceptual diagram which shows the state of an orientation induction layer.

  As shown in FIG. 1, the dielectric film 1 according to the present embodiment includes an orientation induction layer 12 and a dielectric layer 13. In FIG. 1, an alignment-inducing layer 12 and a dielectric layer 13 containing a ferroelectric polymer material as a dielectric between a first electrode layer 11 and a second electrode layer 14 constituting a pair of electrodes. A laminated structure in which is sandwiched is shown. The dielectric film 1 according to this embodiment is characterized in that the orientation-inducing layer 12 is formed as a base of the dielectric layer 13 in order to align the polymer material contained in the dielectric layer 13. Yes. The dielectric film 1 is not limited to the two-layer configuration including the single-layer orientation inducing layer 12 and the single-layer dielectric layer 13 as shown in FIG. 1, but the orientation inducing layer 12 and the dielectric layer 13. And a multi-layer structure in which a plurality of stacked structures are repeatedly stacked.

  The dielectric layer 13 is a layer containing the branched polymer 15 that is a high dielectric material as a main component. The branched polymer 15 has a high dielectric constant polymer 16 having a high relative dielectric constant as a main chain and a low dielectric constant polymer 17 having a relative dielectric constant smaller than that of the high dielectric constant polymer 16 constituting the main chain. Has as a chain. In the dielectric layer 13, while increasing the dielectric constant mainly by the action of the high dielectric constant polymer 16 constituting the main chain, the dielectric loss is caused by the action of the low dielectric constant polymer 17 constituting the side chain. We are trying to reduce it.

  The high dielectric constant polymer 16 is a polymer obtained by polymerizing a monomer having an electric dipole moment, and the electric dipole moment is rotated in the same direction in each monomer unit by applying an electric field. It is a polymer that exhibits a high relative dielectric constant by being polarized so as to be oriented in the direction. The high dielectric constant polymer 16 is a molecular chain constituting the main chain skeleton of the branched polymer 15, and has a branch made of the graft-polymerized low dielectric constant polymer 17 as a side chain. . As shown in FIG. 1B, the dielectric layer 13 of the dielectric film 1 has a main chain high-dielectric-constant polymer 16 of the branched polymer 15 in the direction along the dielectric layer 15. Is formed so as to be uniaxially oriented.

  Here, a branched polymer 15 having a high dielectric constant polymer 16 as a main chain and a low dielectric constant polymer 17 as a side chain is a main component of the dielectric layer 13, and the branched polymer 15 is uniaxially formed. The reason for orientation will be described.

  FIG. 2 is a conceptual diagram of the orientation state and the polarization state of the branched polymer contained in the dielectric film according to this embodiment. In FIG. 2, the concept of dielectric polarization generated in the dielectric layer 13 constituting the dielectric film is shown by taking polyvinylidene fluoride as an example.

As shown in FIG. 2A, the branched polymer 15 has a main chain structure made of polyvinylidene fluoride, which is a high dielectric constant polymer 16, and this main chain structure has a low chain (not shown). It has a molecular structure in which side chains made of dielectric constant polymer 17 are bonded. In FIG. 2A, a region where a low dielectric constant polymer 17 (not shown) may exist is indicated by a broken line. The monomer vinylidene fluoride (— [CH ₂ —CF ₂ ] —) constituting the branched polymer 15 is substantially in the direction in which the main chain is oriented, as indicated by the arrows in FIG. It has a dipole moment (electric dipole moment, permanent dipole moment) including orthogonal components.

  Generally, it is known that polyvinylidene fluoride has a plurality of crystal structures different from each other. Polyvinylidene fluoride usually has an α-phase (type II) crystal structure in the molecular single state, but in the α-phase, the dipole moment is oriented in the opposite direction between adjacent monomers. Therefore, the relative dielectric constant shows a low value of about 3-4. On the other hand, in the molecular assembly state, it is possible to form a β phase (I type) crystal structure as shown in FIG. In the β phase, the dipole moment of the monomer is oriented in substantially the same direction, so that the polarization is large. Therefore, by forming the main chain skeleton of the branched polymer 15 with such a high dielectric constant polymer 16 and appropriately orienting the main chain, polarization in a direction substantially orthogonal to the main chain can be increased. Is possible. That is, the dielectric constant can be increased by uniaxially orienting the high dielectric constant polymer 16 of the main chain of the branched polymer 15 along the creeping direction of the dielectric layer 13 in the dielectric film 1. And the capacity of the film capacitor can be increased.

  On the other hand, the dielectric loss in the dielectric film 1 is strongly influenced by the residual polarization. The polarization state of the high dielectric constant polymer 16 as shown in FIG. 2A can be eliminated by a depolarization operation by molecular rotation around a single bond. When surface charges appear on the upper surface and the lower surface of the polarization region, the electric field formed by these acts as a reversal force. Therefore, when the polarization region is in contact with the electrode, the surface charge is offset by the electrode charge. In this case, since no depolarization force is generated, polarization remains and dielectric hysteresis occurs, leading to an increase in dielectric loss. Therefore, by introducing the low dielectric constant polymer 17 as a side chain of the branched polymer 15, the polarization region is subdivided so that the surface charge is not easily canceled by the electrode charge, thereby reducing the dielectric loss. It becomes possible to plan.

  However, when such a low dielectric constant polymer 17 is introduced in a large amount, the dielectric constant of the branched polymer 15 is greatly reduced. Therefore, it is required to reduce the size of the polarization region in order to reduce the dielectric loss while suppressing the introduction of the low dielectric constant polymer 17. This is because the depolarization force is inversely proportional to the polarization region size, and thus the repolarization force is ensured by reducing the polarization region size. In general, when the branched polymer 15 is formed into a molecular assembly by forming a film, the branched polymer 15 often exhibits a lamellar structure in which a crystalline region and an amorphous region are mixed. Are often large and non-uniform. Therefore, as shown in FIG. 2 (b), the branched polymer 15 is arranged so that the high dielectric constant polymer 16 constituting the main chain is oriented in a uniaxial direction to form a molecular assembly. When the size is reduced, it is possible to achieve both an increase in dielectric constant and a reduction in dielectric loss at a high level.

  As the high dielectric constant polymer 16, a polymer having a relative dielectric constant of 4.0 or more at a frequency of 1 kHz measured at room temperature (25 ° C.) can be used. By including such a high dielectric constant polymer 16 having a high relative dielectric constant in the dielectric layer 13, the dielectric constant of the dielectric film 1 can be increased and the capacitance can be greatly improved. The high dielectric constant polymer 16 is more preferably a polymer having a relative dielectric constant of 5.0 or more. The number average polymerization degree of the high dielectric constant polymer 16 is preferably 300 or more and 100,000 or less, and more preferably about 800 or more and 50,000 or less.

  Specific examples of the high dielectric constant polymer 16 include fluoropolymer (fluorine resin), nylon, urea resin, polyphenylene sulfide, polyurethane, polyester, vinyl acetate resin, acrylic resin, and epoxy resin. . What is necessary is just to provide desired dielectric property to these polymeric materials by introduce | transducing a polar group as needed. Among these, the high dielectric constant polymer 16 is preferably a fluorine-based polymer. By using a fluorine-based polymer as the high dielectric constant polymer 16, the dielectric constant per mass can be improved. Two or more high dielectric constant polymers 16 may be used in combination, but it is more preferable to use one kind alone.

  As the monomer constituting the high dielectric constant polymer 16, for the fluorine-based polymer, for example, fluoroolefin such as vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, ethylene, And olefins such as propylene, and perfluoroalkyl vinyl ethers. That is, as the high dielectric constant polymer 16, for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride, polytetrafluoroethylene, and vinylidene fluoride-trifluoroethylene containing vinylidene fluoride and trifluoroethylene as monomers are used. Binary copolymer, vinylidene fluoride-trifluoroethylene-tetrafluoroethylene terpolymer containing vinylidene fluoride, trifluoroethylene and tetrafluoroethylene as monomers, ethylene-tetrafluoroethylene copolymer, Examples thereof include vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and the like as a main chain skeleton.

  Among these, the high dielectric constant polymer 16 includes, among these, polyvinylidene fluoride using vinylidene fluoride as a monomer, and vinylidene fluoride co-polymer containing vinylidene fluoride as a main monomer and other monomers. A polymer is preferable, and polyvinylidene fluoride (PVDF) and a vinylidene fluoride-trifluoroethylene binary copolymer are more preferable. By using such a polymer using vinylidene fluoride as a monomer, the dielectric constant can be further improved. In addition, since the residual polarization when an external voltage is applied can be reduced, the dielectric loss can be effectively reduced.

  As for the high dielectric constant polymer 16 in the dielectric layer 13, it is preferable to use a derivative of the above exemplified monomer as a monomer constituting the high dielectric constant polymer 16. This is because side chains are introduced into the main chain of the high dielectric constant polymer 16 using a derivative having a reactive group as a reaction point. Examples of the derivative having a reactive group include chlorofluoroethylene, chlorodifluoroethylene, chlorotrifluoroethylene, bromofluoroethylene, bromodifluoroethylene, and bromotrifluoroethylene. By using such an alkyl halide together, a radical reaction point for graft polymerization of the side chain to the main chain can be formed.

  The low dielectric constant polymer 17 is a polymer that binds as a side chain to the high dielectric constant polymer 16 constituting the main chain of the branched polymer 15. Also, a polymer having a small relative dielectric constant is used. By introducing such a low dielectric constant polymer 17 having a small relative dielectric constant as a side chain, the dielectric loss can be reduced as described above.

  As the low dielectric constant polymer 17, it is preferable to use a polymer having a relative dielectric constant of less than 4.0 at a frequency of 1 kHz measured at room temperature (25 ° C.), and a relative dielectric constant of less than 3.0. It is more preferable to use a polymer. Further, a polymer having high compatibility with the high dielectric constant polymer 16 is preferable, and the ratio of the low dielectric constant polymer 17 is preferably 30% by mass or less with respect to the high dielectric constant polymer 16 of the main chain. More preferably, it is around mass%. By using a polymer having such a low relative dielectric constant and high compatibility with the high dielectric constant polymer 16, the polarization region can be effectively subdivided, and the dielectric loss can be reliably reduced. Become.

  Specific examples of the low dielectric constant molecule 17 include polyolefins such as polyethylene and polypropylene, polymethacrylates such as polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), and polybutyl methacrylate, and polymethyl. Examples thereof include polyacrylates such as acrylate, polyethyl acrylate, and polybutyl acrylate, and polyvinyls such as polystyrene (PS) and polyvinyl toluene. Among these, the low dielectric constant polymer 17 is preferably polymethyl methacrylate, polyethyl methacrylate, or polystyrene. By using these polymers as the low dielectric constant polymer 17, the dielectric loss can be effectively reduced. Two or more low dielectric constant polymers 17 may be used in combination, but it is more preferable to use one kind alone. The low dielectric constant polymer 17 may be a homopolymer or a copolymer, but is preferably a homopolymer.

  Here, the reason why the orientation induction layer 12 is formed as a base of the dielectric layer 13 having such a configuration will be described.

  FIG. 3 is a schematic view showing a dielectric film according to a comparative example. (A) is sectional drawing which shows the layer structure of a dielectric film, (b) is a conceptual diagram which shows the state of a dielectric material layer. In the dielectric film 100 according to the comparative example, as shown in FIG. 3A, only the dielectric layer 113 is sandwiched between the first electrode layer 11 and the second electrode layer 14 constituting a pair of electrodes. Has a structure.

  As described above, a branch having a high dielectric constant polymer 16 having a high relative dielectric constant as a main chain and a low dielectric constant polymer 17 having a relative dielectric constant smaller than that of the high dielectric constant polymer 16 constituting the main chain as a side chain. By using the polymer 15 as the dielectric layer 113 and forming the high-chain polymer 16 in the main chain so as to form a molecular assembly oriented in a uniaxial direction, the dielectric constant can be increased and the dielectric loss can be reduced. Both can be achieved. However, it is not easy to form a molecular assembly of the branched polymer 15 having such side chains in the dielectric film manufacturing process, and the dielectric film 100 according to the comparative example shown in FIG. As described above, the high dielectric constant polymer 16 of the main chain of the branched polymer 15 is often in a state of being oriented in the directions of a plurality of axes. In such a dielectric film 100, the polarization region size is large, steric hindrance in molecular rotation is likely to occur, and it is difficult to eliminate residual polarization during the depolarization operation. Therefore, in the dielectric film 1 according to the present embodiment, the alignment inducing layer 12 is formed in advance as a base of the dielectric layer 13, and the branched polymer 15 of the dielectric layer 13 is favorably uniaxially formed by the alignment inducing layer 12. Orientation is induced in the direction.

  The alignment-inducing layer 12 is a layer containing a linear polymer 18 that is a ferroelectric as a main component. The linear polymer 18 is a linear high dielectric constant polymer that does not have a side chain made of a polymer, and has a low dielectric constant polymer as a side chain like the branched polymer 15 described above. It is a polymer different from the graft polymer having 17. The alignment-inducing layer 12 of the dielectric film 1 is formed so that such a linear polymer 18 is uniaxially oriented along the layering direction of the orientation-inducing layer 12 as shown in FIG. The By using such a linear polymer 18 with less steric hindrance in the alignment-inducing layer 12, it is easy to form the alignment-inducing layer 12 in which the alignment-inducing polymer is well uniaxially oriented, and the main chain is The linear polymer 18 that is a high dielectric constant polymer also increases the dielectric constant.

  When the dielectric layer 13 is formed on such an orientation inducing layer 12, as shown in FIGS. 1B and 1C, the linear high-order uniaxially oriented in the creeping direction in the orientation inducing layer 12 is performed. The branched polymer 16 is oriented in the same direction as the molecule 18. A dielectric film in which the branched polymer 15 contained in the dielectric layer 13 and the linear polymer 18 contained in the orientation inducing layer 12 are uniaxially oriented in the same direction along the layering direction. 1 is formed. In the dielectric layer 13 of the dielectric film 1, as shown in FIG. 1 (b), the low dielectric constant polymer 17 is interposed between adjacent uniaxially oriented branched polymers 15. Since the dispersion state is maintained at a predetermined interval, the polarization region is appropriately subdivided, and the dielectric loss can be effectively reduced.

  As the linear polymer 18, a polymer selected from the same group as the polymer used as the high dielectric constant polymer 16 constituting the main chain of the branched polymer 15 can be used. Specifically, a fluorine-based polymer is preferable, such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, vinylidene fluoride-trifluoroethylene binary copolymer, or vinylidene fluoride-trifluoroethylene-tetrafluoroethylene ternary. A copolymer is more preferred. The linear polymer 18 is more preferably a polymer of the same type as the high dielectric constant polymer 16 constituting the main chain of the branched polymer 15 contained in the dielectric layer 13.

  The first electrode layer 11 and the second electrode layer 14 may be thin film electrode layers formed by vapor deposition of metal or metal foils. As a metal which comprises the 1st electrode layer 11 and the 2nd electrode layer 14, aluminum, zinc, copper, tin, these alloys etc. are mentioned, for example, Aluminum or aluminum alloy is used suitably.

  Next, a method for manufacturing the dielectric film 1 and a dielectric film manufacturing apparatus will be described.

  FIG. 4 is a schematic view showing the configuration of the dielectric film manufacturing apparatus according to this embodiment.

  As shown in FIG. 4, the dielectric film manufacturing apparatus 50 mainly includes a pressing unit 51, sweeping units 52 and 53, and a coating unit 54.

  The pressing means 51 is a device that presses the supplied polymer pellets (blocks) and presses them against the base material. The dielectric film manufacturing apparatus 50 is provided with a heating stage 55 so as to face the pressing means 51. The substrate to be conveyed is heated by the heating stage 55, and the polymer pellets to be pressure-bonded to the substrate are heated and softened. The temperature at which the substrate is heated is preferably not higher than the melting point of the linear polymer 18, and is preferably not higher than 130 ° C., for example. Within such a temperature range, alteration of the linear polymer 18 can be avoided, and sweeping with good accuracy can be performed.

  As the polymer pellets, polymer pellets obtained by molding the linear polymer 18 are supplied. The linear polymer 18 (the high dielectric constant polymer of the main chain of the linear polymer 18) can be synthesized using an appropriate polymerization method depending on the type of the polymer. Examples of the polymerization method include radical polymerization methods such as an emulsion polymerization method, a suspension polymerization method, and a solution polymerization method. As a base material, an appropriate metal substrate, an inorganic substrate, a resin substrate, or the like that can withstand a pressure load can be used, but a glass substrate suitable for orientation is preferably used.

  The sweeping means 52, 53 sweeps the substrate in a direction substantially perpendicular to the direction of pressing by the pressing means 51, and forms the alignment-inducing layer 12 in which the linear polymer 18 is uniaxially oriented along the layering direction. It is. The sweeping means 52 and 53 include a movable body 52 on which a base material is placed and a drive mechanism 53 that drives the movement of the movable body 52. For example, the movable body 52 is configured by a slat, a belt, a roller, and the like, and the drive mechanism 53 is rotated so that the movable body 52 is sequentially moved. In the dielectric film manufacturing apparatus 50, the sweep means 52 and 53 also have a function of sequentially transporting the base material and the dielectric film to each step.

  In the production of the dielectric film 1, the pressing means 51 pressure-bonds the polymer pellets containing the linear polymer 18 to the conveyed substrate. And the polymer pellet press-bonded to the base material becomes a softened state or a molten state by heating by the heating stage 55. Therefore, the substrate on which the semi-molten polymer pellets containing the linear polymer 18 are pressure-bonded is swept by the sweeping means 52 and 53, and the orientation inducing layer 12 is formed by using a friction transfer method. Thus, by employing the friction transfer method as the means for forming the orientation induction layer 12, it is possible to form the orientation induction layer 12 in which the linear polymer 18 is well uniaxially oriented along the layering direction. Become. Moreover, in this dielectric film manufacturing apparatus 50, since the sweep means 52 and 53 also have the function to convey a base material and a dielectric film, the dielectric film of a roll-to-roll format is also possible. Note that the sweep speed and the pressure bonding load can be adjusted as appropriate. If the film thickness of the alignment induction layer 12 is 10 nm or more, alignment induction can be performed.

  The coating means 54 wet-coats the branched polymer 15 on the surface of the orientation-inducing layer 12 to form the dielectric layer 13 in which the branched polymer 15 is uniaxially oriented in the same direction as the linear polymer 18. It is a device to do. As the coating means 54, a known wet coating apparatus such as a slot die coater, a blade coater, a bar coater, a roll coater, or a gravure coater can be used.

  The branched polymer 15 is obtained by graft polymerizing a low-dielectric polymer 17 having a side chain to a high-dielectric polymer 16 having a main chain synthesized by the same polymerization method as the linear polymer 18 described above. Can be synthesized. As a method for graft polymerization, living radical polymerization is preferably used, and an atom transfer radical polymerization method (ATRP method) performed using a transition metal complex catalyst such as a CuCl / bipyridine complex is particularly preferable. Specifically, the method described in Non-Patent Document 1 can be applied. Examples of the solvent for the branched polymer 15 include N, N-dimethylformamide, diethyl carbonate, 2-pentanone, 3-pentanone, 2-hexanone, 2-heptanone, 3-heptanone, and cyclohexanone. An appropriate solvent can be used depending on the case.

  In the production of the dielectric film 1, the branched polymer 15 is wet coated on the surface of the orientation inducing layer 12 by the application means 54, so that the orientation of the branched polymer 15 is aligned in the orientation inducing layer 12. A linear polymer 18 that is uniaxially oriented along the layer direction, a branched polymer 15 that is induced in the same direction and is included in the dielectric layer 13, and a linear polymer that is included in the alignment-inducing layer 12 The dielectric film 1 in which the molecules 18 are uniaxially oriented in the same direction along the layering direction is manufactured. The wet-applied dielectric layer 13 can be dried in an appropriate atmosphere, and the solvent can be removed in any of an inert gas atmosphere such as argon gas and nitrogen gas, and an oxidizing gas atmosphere such as air. Good.

  The dielectric film manufacturing apparatus 50 may further include at least one of a polarization unit, a stretching unit, and a multilayer film forming unit. The polarization means is composed of an electric field application device, a magnetic field application device, or the like. By applying such an electric field or magnetic field to the dielectric film in a heated atmosphere by such a polarization means, the high dielectric constant polymer 16 contained in the dielectric film 1 can be brought into a polarized state. In particular, by making the branched polymer 15 have a β-phase crystal structure, the dipole moment is oriented in the direction perpendicular to the layering direction to maximize polarization. In addition, the dielectric film 1 is further uniaxially stretched in the layering direction by a stretching means, so that the branched polymer 15 included in the dielectric layer 13 and the linear high molecular weight included in the alignment-inducing layer 12 are obtained. The molecules 18 can be better oriented and the dielectric loss can be effectively reduced. Moreover, the dielectric film 1 can be thickened by supplying and multilayering the dielectric film 1 formed in the feed block or multi-manifold provided in the multilayer film forming means. The dielectric film manufacturing apparatus 50 is configured such that, instead of the pressing means 51 described above, sweeping is performed when an apparatus that presses polymer pellets and presses them against the base material moves relative to the base material. Alternatively, instead of the coating means 52, the coating may be performed in a stationary state by a spin coater or the like.

  The dielectric film manufacturing apparatus 50 may further include an electrode forming unit. The electrode forming means is composed of a vapor deposition apparatus or the like that vapor-deposits electrodes. After the first electrode layer 11 and the second electrode layer 14 are formed on the surface of the dielectric film 1 by such electrode forming means, the dielectric film 1 is wound, and external electrodes are connected and accommodated in the casing. Thereby, it can be set as the film capacitor 64 provided with the dielectric film 1 and a pair of 1st electrode and 2nd electrode electrically connected to the dielectric film 1. FIG.

  FIG. 5 is a schematic diagram comparing the size of the converter to which the film capacitor according to the present embodiment is applied with the size of the power converter having the film capacitor according to the comparative example.

  FIG. 5 shows a power converter (inverter) 60 to which a film capacitor 64 including the dielectric film 1 according to the present embodiment is applied, and a film capacitor 61 (film capacitor according to a comparative example) employing conventional polypropylene or the like. A power converter 160 is shown. The power converter 60 and the power converter 160 each include a common power module 62 and a power distribution board 63.

  As shown in FIG. 5, in the conventional power converter 160 whose operating voltage exceeds 1 kV, the film capacitor 61 occupies nearly 70% of the total volume. In contrast, in the power converter 60 to which the film capacitor 64 including the dielectric film 1 according to the present embodiment is applied, the capacitor volume can be reduced to about 1/5, and the capacitor cooling system is also small. Can be realized. As a result, the MMC (modular multi-level converter) composed of such a power converter 60 can be greatly reduced in size, which is suitable for reducing the installation cost of power generation equipment and the like.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using the Example of this invention, the technical scope of this invention is not limited to this.

  The dielectric film 1 according to the example in which the dielectric layer 13 was formed on the orientation induction layer 12 was manufactured, and the orientation state of the polymer was analyzed. Moreover, the dielectric constant 1 and the dielectric loss were evaluated about the dielectric film 1 which concerns on an Example.

[Example]
First, a powder made of vinylidene fluoride-trifluoroethylene binary copolymer polymer P (VDF-TrFE) (70/30 mol%: manufactured by Piezotech) was compressed to prepare polymer pellets. Subsequently, the orientation-inducing layer 12 was formed by friction transfer of the produced polymer pellets on a glass substrate heated to 130 ° C. which is not higher than the melting point of P (VDF-TrFE). For the friction transfer, a friction transfer device “Hot Melt Coating Machine 115A” (manufactured by Imoto Seisakusho Co., Ltd.) was used, and the pressing condition was 10 kgf / cm ² and the sweep speed was 200 mm / min. The thin film of the obtained orientation induction layer 12 was about 10 nm in thickness, and the main chain of P (VDF-TrFE) was uniaxially oriented on the glass substrate surface. The orientation state of the polymer is 2D-GIXD (polarization FTIR (Fourier transform infrared absorption method), SEM (scanning electron microscope), electron diffraction of TEM (transmission electron microscope), Spring 8 and the like as a radiation light source. Analysis was performed using a very low angle incident X-ray two-dimensional diffraction method.

  Next, vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene terpolymer polymer P (VDF-TrFE-CTFE) (62/30/8 mol%: manufactured by Piezotech), polyethyl methacrylate (PEMA), Was graft polymerized by an atom transfer radical polymerization method (ATRP method). Note that the mass ratio of PEMA to P (VDF-TrFE-CTFE) was 20 mass%. As a result, a branched polymer P (VDF-TrFE-CTFE) -g-PEMA having P (VDF-TrFE-CTFE) as the main chain and PEMA as the side chain was obtained. Subsequently, the branched polymer 15 is dissolved in a solvent N, N-dimethylformamide (DMF) so as to have a concentration of 3% by mass, and wet-coated on the orientation-inducing layer 12 to form a dielectric. Layer 13 was laminated. The total film thickness of the orientation induction layer 12 and the dielectric layer 13 was 100 nm.

  Next, the orientation state of the polymer in the dielectric layer 13 was analyzed. As a result, branched polymer P (VDF-TrFE-CTFE) -g-PEMA is compared with P (VDF-TrFE) that is uniaxially oriented in the direction of the thin film of the orientation inducing layer 13. It was confirmed that they were arranged substantially parallel and both were uniaxially oriented in substantially the same direction. Further, the side chain PEMA which is the low dielectric constant polymer 17 is interposed between the main chains P (VDF-TrFE-CTFE) which are the high dielectric constant polymer 16, whereby the high dielectric constant polymer 16. It was confirmed that P (VDF-TrFE-CTFE) of the main chain as shown in FIG.

  Next, the first electrode layer 11 and the second electrode layer 14 were formed on both surfaces of the dielectric film 1 peeled from the glass substrate. The first electrode layer 11 and the second electrode layer 14 were formed to have a thickness of 50 nm by depositing aluminum. Then, using a parameter analyzer “HP4284A” (manufactured by Hewlett Packard), the capacitance at each frequency of 100 Hz, 1 kHz, and 10 kHz was measured at room temperature (25 ° C.) and 100 ° C., and the relative dielectric constant and dielectric loss. And asked.

  FIG. 6 is a diagram illustrating the relationship between the dielectric constant and dielectric loss of the dielectric films according to the examples and the dielectric films according to the comparative examples. In FIG. 6, the vertical axis represents the relative dielectric constant, and the horizontal axis represents the dielectric loss (tan δ). Moreover, the black circle has shown the dielectric film which concerns on an Example, and the white hexagon has shown the dielectric film which concerns on the comparative example which does not have an orientation induction layer. White circles, white triangles, and white squares are dielectric films according to comparative examples each having only a dielectric layer containing a branched polymer, both of which are not subjected to stretching treatment and polarization treatment, Each is manufactured by changing the mass ratio of the low dielectric constant polymer. The black triangle indicates a dielectric film according to a reference example using polypropylene as a material.

As shown in FIG. 6, for each dielectric film according to each comparative example, the relative permittivity and the dielectric loss have different values, but as shown by the broken line, both are the relative permittivity and the dielectric loss. The tendency to be a trade-off relationship was shown. On the other hand, in the dielectric film 1 according to the example, compared with the dielectric films according to these comparative examples, the relative dielectric constant is about 10 ⁻³ while realizing a value of about 10 ^−3. It was confirmed that it was reduced to a certain extent. In addition, it was confirmed that although the dielectric loss was at a high level as compared with the dielectric film according to the reference example using polypropylene as a material, the relative dielectric constant achieved a value of about 5 times. As described above, it was confirmed that the dielectric films according to the examples were highly compatible with increase in dielectric constant and reduction in dielectric loss. This dielectric loss level can be said to be sufficiently low, for example, in the application of a power converter (inverter) used in a frequency band from 100 Hz to 1 kHz.

DESCRIPTION OF SYMBOLS 1 Dielectric film 11 1st electrode layer 12 Orientation induction layer 13 Dielectric layer 14 2nd electrode layer 15 Branched polymer 16 High dielectric constant polymer 17 Low dielectric constant polymer 18 Linear polymer

Claims (9)

  A branched high chain having a high dielectric constant polymer having a relative dielectric constant of 4.0 or more at a frequency of 1 kHz as a main chain and a low dielectric constant polymer having a relative dielectric constant smaller than that of the high dielectric constant polymer as a side chain. A dielectric layer comprising molecules, and an orientation-inducing layer comprising a linear polymer having the high-dielectric-constant polymer as a main chain, and a branched high layer contained in the dielectric layer. A dielectric film characterized in that molecules and a linear polymer contained in the orientation-inducing layer are uniaxially oriented along the layering direction.   The dielectric film according to claim 1, wherein the high dielectric constant polymer is a fluorine-based polymer.   The dielectric film according to claim 1, wherein the high dielectric constant polymer is polyvinylidene fluoride or a vinylidene fluoride-based copolymer.   The dielectric film according to claim 1, wherein the low dielectric constant polymer is interposed between the uniaxially oriented adjacent branched polymers.   The dielectric film according to claim 1, wherein the low dielectric constant polymer is polymethyl methacrylate, polyethyl methacrylate, or polystyrene.   The dielectric film according to claim 1, wherein the low dielectric constant polymer is polymerized to the high dielectric constant polymer by graft polymerization.   The dielectric film according to claim 1, wherein the dielectric film is uniaxially stretched in the layering direction.   A branched high chain having a high dielectric constant polymer having a relative dielectric constant of 4.0 or more at a frequency of 1 kHz as a main chain and a low dielectric constant polymer having a relative dielectric constant smaller than that of the high dielectric constant polymer as a side chain. Comprising a dielectric layer comprising molecules, an alignment-inducing layer comprising a linear polymer having the high dielectric constant polymer as a main chain, the dielectric layer and the alignment-inducing layer, A dielectric film in which a branched polymer contained in the dielectric layer and a linear polymer contained in the orientation-inducing layer are uniaxially oriented along the layering direction; and A film capacitor comprising a pair of first electrodes and second electrodes connected together.   A dielectric layer comprising a branched polymer having a high dielectric constant polymer as a main chain and a low dielectric constant polymer as a side chain, and a linear polymer having the high dielectric constant polymer as a main chain The branched polymer contained in the dielectric layer and the linear polymer contained in the orientation-inducing layer are uniaxially oriented along the layering direction. A dielectric film manufacturing apparatus for manufacturing a dielectric film, wherein a pressing means for press-bonding a lump containing the linear polymer to a base material, and sweeping the press-bonded base material Sweeping means for forming the alignment-inducing layer in which the linear polymer is uniaxially oriented along the layering direction; wet-coating the branched polymer on the surface of the alignment-inducing layer; and Coating means for forming the dielectric layer in which the polymer is uniaxially oriented in the same direction as the linear polymer. The dielectric film manufacturing apparatus characterized.

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