JP2011072112A - Dielectric film and transducer using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric film having a large dielectric constant without lowering electrical resistivity, and to provide a transducer improved in insulation breakdown resistance and electric field responsiveness. <P>SOLUTION: The dielectric film is composed of a cross-linked body which is cross-linked with an elastomer composition including an elastomer and a polarity chemical compound which is larger than the elastomer in dielectric constant and can be coupled with the elastomer. In the cross-linked body, the polarity chemical compound is graft-coupled to the elastomer. The transducer is constituted by interposing the dielectric film between at least a pair of electrodes. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a dielectric film suitable for a transducer such as an actuator or a sensor, and a transducer using the dielectric film.

  Examples of the transducer include an actuator that converts mechanical energy and electric energy, a sensor, a power generation element, and the like, or a speaker that converts acoustic energy and electric energy, a microphone, and the like. Polymer materials such as dielectric elastomers are useful for constructing a highly flexible, small and lightweight transducer.

  For example, an actuator can be configured by arranging a pair of electrodes on both sides in the thickness direction of a dielectric film made of a dielectric elastomer. In this type of actuator, increasing the voltage applied between the electrodes increases the electrostatic attractive force between the electrodes. For this reason, the dielectric film sandwiched between the electrodes is compressed in the thickness direction, and the thickness of the dielectric film is reduced. As the film thickness decreases, the dielectric film extends in a direction parallel to the electrode surface. On the other hand, when the applied voltage between the electrodes is reduced, the electrostatic attractive force between the electrodes is reduced. For this reason, the compressive force from the thickness direction to the dielectric film is reduced, and the film thickness is increased by the elastic restoring force of the dielectric film. As the film thickness increases, the dielectric film shrinks in the direction parallel to the electrode surface. Thus, the actuator drives the member to be driven by extending and contracting the dielectric film.

  From the viewpoint of increasing the force and displacement taken out from the actuator, the dielectric film desirably has the following characteristics. That is, the dielectric constant is large to store a large amount of charge at the interface between the dielectric film and the electrode, the dielectric breakdown resistance is excellent to withstand a high electric field, and the flexibility is flexible so that it can be repeatedly expanded and contracted. , Etc. Therefore, as a material for the dielectric film, silicone rubber having excellent dielectric breakdown resistance, nitrile rubber having high relative dielectric constant, acrylic rubber, and the like are often used (see, for example, Patent Documents 1 and 2). In addition, from the viewpoint of increasing the relative dielectric constant, attempts have been made to blend fine particles having a high dielectric constant such as barium titanate in an elastomer (for example, see Patent Documents 2 and 3).

JP-T-2001-524278 Special table 2003-505865 gazette JP 2008-53527 A

  For example, silicone rubber has a siloxane bond as a skeleton. For this reason, volume resistivity is large. Therefore, the dielectric film made of silicone rubber is difficult to break down even when a large voltage is applied. However, the polarity of silicone rubber is small. That is, the relative dielectric constant is small. For this reason, when the actuator is configured using a dielectric film made of silicone rubber, the electrostatic attractive force with respect to the applied voltage is small. Therefore, the electric field response is inferior, and sufficient force and displacement cannot be obtained.

  On the other hand, the relative dielectric constant of nitrile rubber or acrylic rubber is larger than that of silicone rubber. For this reason, when nitrile rubber or the like is used as the material of the dielectric film, the electrostatic attractive force with respect to the applied voltage becomes larger than when silicone rubber or the like is used. However, even if an actuator is configured using a dielectric film made of nitrile rubber or the like, the force and displacement taken out are still not satisfactory. For this reason, it is necessary to further increase the relative dielectric constant of the dielectric film.

  Nitrile rubber has a structure that induces a large dipole moment by causing orientation polarization or ion polarization in an electric field. For this reason, the polarity of nitrile rubber is large. Therefore, nitrile rubber belongs to a class having a relatively large relative dielectric constant. However, when the content of the polar group exceeds a certain level, the crystallinity increases and the glass transition temperature (Tg) increases. As a result, the relative dielectric constant decreases. Therefore, there is a limit to the improvement of the dielectric constant only by increasing the polar group.

  Further, as in Patent Documents 2 and 3, when high-permittivity fine particles are blended in the elastomer, it is difficult to maintain the flexibility of the dielectric film. That is, by blending fine particles having a high dielectric constant, the dielectric constant of the dielectric film is improved, but the elastic modulus of the elastomer is increased and the elongation is reduced. That is, the inherent flexibility of the elastomer is impaired. As a result, expansion and contraction of the dielectric film with respect to the applied voltage may be hindered.

  This invention is made | formed in view of such a situation, and makes it a subject to provide the dielectric film with a large relative dielectric constant, without reducing volume resistivity. It is another object of the present invention to provide a transducer having excellent dielectric breakdown resistance and electric field response.

  (1) In order to solve the above problems, the dielectric film of the present invention is a dielectric film interposed between at least a pair of electrodes in a transducer, and has an elastomer and a relative dielectric constant larger than that of the elastomer. And a crosslinkable product obtained by crosslinking an elastomer composition containing the polar compound, wherein the polar compound is graft-bonded to the elastomer.

  According to the dielectric film (crosslinked product) of the present invention, the elastomer is crosslinked and a polar compound is grafted to the polymer chain. That is, the polar compound is not simply dispersed in the elastomer but is grafted to the elastomer. By incorporating a polar compound into the structure of the elastomer, the properties of the elastomer itself change. That is, the relative dielectric constant of the polar compound is larger than that of the elastomer. Therefore, the relative dielectric constant of the elastomer to which the polar compound is grafted (that is, the dielectric film of the present invention) is larger than that of the original elastomer. In addition, the functional group derived from the polar compound and a new structure are introduced into the elastomer by grafting the polar compound. Thereby, since the crystallinity of the elastomer is disturbed, it is considered that an increase in the glass transition temperature (Tg) in the dielectric film is suppressed.

  Many polar compounds have a small volume resistivity. However, according to the dielectric film of the present invention, the polar compound is grafted to the elastomer. For this reason, even if it contains a polar compound, it is thought that the influence with respect to the volume resistivity of a dielectric film is small. Therefore, according to the dielectric film of the present invention, it is possible to improve the relative dielectric constant without reducing the volume resistivity.

  The polar compound is grafted to the elastomer. Therefore, in Patent Documents 2 and 3, unlike the case where the high dielectric constant fine particles are mixed with the elastomer, there is little possibility of reducing the flexibility of the dielectric film. Therefore, it is difficult to inhibit expansion and contraction of the dielectric film. As described above, when the dielectric film of the present invention is used, a large force and displacement can be obtained, for example, in an actuator.

  (2) Further, the transducer of the present invention comprises a crosslinked body obtained by crosslinking an elastomer composition containing an elastomer and a polar compound having a relative dielectric constant larger than that of the elastomer and capable of binding to the elastomer. The polar compound includes a dielectric film graft-bonded to the elastomer, and a plurality of electrodes disposed through the dielectric film.

  A transducer is a device that converts one type of energy into another type of energy. The transducer includes an actuator, a sensor, etc. that convert mechanical energy and electrical energy, a speaker, a microphone, etc. that converts acoustic energy and electrical energy. The transducer of the present invention includes the dielectric film of the present invention. That is, in the transducer of the present invention, the dielectric film has a high relative dielectric constant. For this reason, a lot of charges can be stored at the interface between the dielectric film and the electrode. Moreover, even if a polar compound is grafted, the flexibility and volume resistivity of the elastomer itself are difficult to decrease. Therefore, the transducer of the present invention is excellent in dielectric breakdown resistance and electric field response.

It is a cross-sectional schematic diagram of the actuator which is one Embodiment of the transducer of this invention, Comprising: (a) shows an OFF state, (b) shows an ON state, respectively. It is a cross-sectional schematic diagram of the capacitive sensor which is one Embodiment of the transducer of this invention. It is a cross-sectional schematic diagram of the electric power generating element which is one Embodiment of the transducer of this invention, Comprising: (a) is at the time of expansion | extension, (b) shows the time of contraction. It is a perspective view of the speaker which is one Embodiment of the transducer of this invention. It is VV sectional drawing of FIG. It is a front view of the actuator attached to the experimental apparatus. It is a VII-VII direction sectional view of Drawing 6.

  Hereinafter, embodiments of the dielectric film and the transducer of the present invention will be described. The dielectric film and the transducer of the present invention are not limited to the following embodiments, and can be variously modified and improved by those skilled in the art without departing from the gist of the present invention. Can be implemented.

<Dielectric film>
The dielectric film of the present invention comprises a crosslinked product obtained by crosslinking an elastomer composition containing an elastomer and a polar compound having a relative dielectric constant larger than that of the elastomer and capable of binding to the elastomer.

It is desirable to use an elastomer having a large volume resistivity. A dielectric film having a large volume resistivity is excellent in dielectric breakdown resistance. For this reason, a larger voltage can be applied to the dielectric film. Thereby, the output and displacement amount of the transducer can be increased. For example, the volume resistivity of the elastomer is desirably 10 ⁹ Ω · cm or more. 10 ¹⁰ Ω · cm or more is preferable. Further, those having a relatively large relative dielectric constant and those having high flexibility are suitable. If the elastomer is highly flexible, the stretchability of the dielectric film is improved. This improves the electric field response and durability of the transducer.

  From this point of view, suitable elastomers include nitrile rubber, hydrogenated nitrile rubber, acrylic rubber, natural rubber, isoprene rubber, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate. -Acrylic acid ester copolymer, butyl rubber, styrene-butadiene rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, chloroprene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, urethane rubber and the like. Further, an elastomer modified by introducing a functional group, such as epoxidized natural rubber or carboxyl-modified hydrogenated nitrile rubber, may be used. An elastomer can be used individually by 1 type or in mixture of 2 or more types.

  What is necessary is just to select a polar compound suitably according to the elastomer to be used. That is, it may be selected from compounds having a relative dielectric constant larger than that of an elastomer and a structure or functional group that can be bonded to the elastomer.

  Examples of polar compounds include carbon-carbon double bonds (C═C), hydroxyl groups (—OH), amino groups (—NH), carboxyl groups (—COOH), thiol groups (—SH), and halogenated compounds. The compound which has 1 or more types chosen from an alkyl group is mentioned. Such a polar compound and an elastomer can be bonded with, for example, the following structures and combinations of functional groups. Hereinafter, the combination of the bondable structure and the functional group is shown in the order of [structure and functional group on the elastomer side]-[structure and functional group on the polar compound side].

  [Carbon-carbon double bond]-[Carbon-carbon double bond], [Phenol or its substitution product]-[Carbon-carbon double bond], [Quinone derivative]-[Carbon-carbon double bond], [ Isocyanate]-[hydroxyl group], [isocyanate]-[amino group], [isocyanate]-[carboxyl group], [carboxyl group]-[hydroxyl group], [carboxyl group]-[amino group], [epoxy group] -[Hydroxyl group], [epoxy group]-[amino group], [epoxy group]-[carboxyl group], [halogenated alkyl group]-[amino group], [halogenated alkyl group]-[carboxyl group], [Halogenated alkyl group]-[thiol group], [carboxyl group]-[halogenated alkyl group], [amino group]-[halogenated alkyl group].

In addition, it is desirable that the relative permittivity of the polar compound is large. For example, a compound having a relative dielectric constant of 15 or more is suitable. For example, sulfoxide (R ₁ —S (═O) —R ₂ ), sulfonamide (R ₁ —SO ₂ —NR ₂ R ₃ ), carbonate (R ₁ O—C (═O) —OR ₂ ), and Many compounds having a structure of any one of the cyano groups (—CN) have a large relative dielectric constant. For example, vinylene carbonate, allyl methyl carbonate, diallyl dicarbonate, phenyl vinyl sulfoxide and the like can be mentioned.

  In the dielectric film of the present invention, the polar compound is grafted to the elastomer. The determination of the presence or absence of graft bonding can be performed, for example, as follows. First, a solvent in which a polar compound is soluble is prepared. Next, the dielectric film is immersed in the solvent for a predetermined time. Thereafter, the mass of the dielectric film (insoluble matter) remaining without being dissolved in the solvent is measured. And the mass ratio of the insoluble part with respect to the mass of the dielectric film before solvent immersion is calculated. If the mass ratio of the insoluble component is close to 100%, it can be determined that the blended polar compound is grafted to the elastomer.

<Dielectric film manufacturing method>
The dielectric film of the present invention is produced by crosslinking an elastomer composition containing an elastomer and a polar compound. A cross-linking agent, a vulcanization accelerator, a processing aid, a plasticizer, an anti-aging agent, a reinforcing agent, a colorant, and the like may be added to the elastomer composition as necessary. What is necessary is just to determine a crosslinking method suitably according to the kind of elastomer. For example, sulfur crosslinking, peroxide crosslinking, isocyanate crosslinking, electron beam (EV) crosslinking, ultraviolet (UV) crosslinking and the like can be mentioned. Depending on the crosslinking method, necessary additives such as a crosslinking agent may be added to the elastomer composition.

  The elastomer composition can be prepared, for example, by kneading an elastomer, a polar compound, and, if necessary, an additive with a roll or a kneader. In this case, the dielectric film may be produced by filling the prepared elastomer composition into, for example, a mold and press-crosslinking under a predetermined condition. Further, an elastomer composition can be prepared by dissolving an elastomer, a polar compound, and, if necessary, an additive in a predetermined solvent. In this case, first, the prepared elastomer composition is applied to a substrate or the like. Next, the coating film is dried to evaporate the solvent. Thereafter, the dielectric film may be manufactured by advancing the crosslinking reaction under predetermined conditions. In addition, when the grafting of the polar compound to the elastomer does not proceed sufficiently only by crosslinking the elastomer composition, grafting may be performed under predetermined conditions in addition to the crosslinking.

  The blending amount of the polar compound is desirably equal to or less than the carbon-carbon double bond amount and the functional group amount in the elastomer. If the amount exceeds the same amount, the amount that is not grafted increases, which may reduce the volume resistivity of the dielectric film. Moreover, it is desirable to set it as 1 to 100 mass parts with respect to 100 mass parts of an elastomer. When the amount is less than 1 part by mass, the effect of improving the relative dielectric constant is small. 5 parts by mass or more is preferable. On the other hand, when the amount exceeds 100 parts by mass, there is a possibility that the amount that is not grafted increases and the volume resistivity of the dielectric film is lowered. 30 parts by mass or less is preferable.

<Transducer>
The transducer according to the present invention includes the dielectric film according to the present invention and a plurality of electrodes disposed via the dielectric film. The configuration of the dielectric film and the manufacturing method of the present invention are as described above. Therefore, the description is omitted here. In the transducer according to the present invention, it is desirable to adopt a preferable aspect of the dielectric film according to the present invention.

  What is necessary is just to determine the thickness of a dielectric film suitably according to a use etc. For example, when the transducer of the present invention is used as an actuator, it is desirable that the thickness of the dielectric film is small from the viewpoints of downsizing the actuator, driving at a low potential, and increasing the amount of displacement. In this case, it is desirable that the thickness of the dielectric film be 1 μm or more and 1000 μm (1 mm) or less in consideration of dielectric breakdown properties and the like. A more preferable range is 5 μm or more and 200 μm or less.

  In the transducer of the present invention, the material of the electrode is not particularly limited. For example, a conductive material made of carbon material such as carbon black or carbon nanotube or a conductive material made of metal and a paste or paint mixed with oil or elastomer as a binder, or an electrode made by knitting carbon material or metal in a mesh shape, etc. Can be used. It is desirable that the electrode can expand and contract according to the expansion and contraction of the dielectric film. When the electrode expands and contracts together with the dielectric film, the deformation of the dielectric film is not easily disturbed by the electrode. For this reason, when the transducer of the present invention is used as an actuator or the like, a desired amount of displacement can be easily obtained.

  Further, when the transducer of the present invention has a laminated structure in which a plurality of dielectric films and electrodes are alternately laminated, a larger force can be generated. Therefore, when the laminated structure is adopted, for example, the output of the actuator can be increased. Thereby, a drive object member can be driven with bigger force.

[First embodiment]
As a first example of the transducer of the present invention, an embodiment embodied in an actuator will be described. FIG. 1 is a schematic cross-sectional view of the actuator of this embodiment. (A) shows an OFF state, and (b) shows an ON state.

  As shown in FIG. 1, the actuator 1 includes a dielectric film 10 and electrodes 11a and 11b. The dielectric film 10 is made of a crosslinked material obtained by crosslinking an elastomer composition containing hydrogenated nitrile rubber (elastomer) and diallyl dicarbonate (polar compound). The dielectric film 10 is included in the dielectric film of the present invention. The electrodes 11a and 11b are fixed to the upper and lower surfaces of the dielectric film 10, respectively. The electrodes 11a and 11b are connected to the power source 12 via a conducting wire. When switching from the off state to the on state, a voltage is applied between the pair of electrodes 11a and 11b. As the voltage is applied, the thickness of the dielectric film 10 is reduced, and accordingly, as shown by the white arrow in FIG. 1B, the dielectric film 10 extends in a direction parallel to the surfaces of the electrodes 11a and 11b. Thereby, the actuator 1 outputs the driving force in the vertical direction and the horizontal direction in the drawing.

  Here, the dielectric constant of the dielectric film 10 is large. For this reason, many electric charges can be stored in the interface of the dielectric film 10 and electrode 11a, 11b. That is, a large electrostatic attractive force is generated between the electrodes 11a and 11b. The dielectric film 10 is flexible. Therefore, according to the actuator 1, a large force and displacement can be obtained. The dielectric film 10 includes a polar compound. However, the dielectric film 10 maintains a volume resistivity substantially equal to the volume resistivity of a dielectric film manufactured only from an elastomer. Therefore, the dielectric breakdown resistance of the dielectric film 10 is high. For this reason, a large voltage can be applied to the dielectric film 10. As a result, a greater force and displacement can be obtained. If the dielectric film 10 is arranged in a state extending in the surface extending direction, the dielectric breakdown resistance of the dielectric film 10 is improved. Therefore, a larger voltage can be applied to the dielectric film 10. Thereby, the output and displacement amount of the actuator 1 can be further increased.

[Second Embodiment]
As a second example of the transducer of the present invention, an embodiment embodied in a capacitive sensor will be described. FIG. 2 is a schematic cross-sectional view of the capacitive sensor of this embodiment. As shown in FIG. 2, the capacitive sensor 2 includes a dielectric film 20, electrodes 21 a and 21 b, and a substrate 22. The dielectric film 20 is made of a crosslinked material obtained by crosslinking an elastomer composition containing hydrogenated nitrile rubber (elastomer) and diallyl dicarbonate (polar compound). The dielectric film 20 is included in the dielectric film of the present invention. The dielectric film 20 has a strip shape extending in the left-right direction. The dielectric film 20 is disposed on the upper surface of the substrate 22 via the electrode 21b. The electrodes 21a and 21b have a strip shape extending in the left-right direction. The electrodes 21a and 21b are fixed to the upper and lower surfaces of the dielectric film 20, respectively. Conductive wires (not shown) are connected to the electrodes 21a and 21b. The substrate 22 is an insulating flexible film and has a strip shape extending in the left-right direction. The substrate 22 is fixed to the lower surface of the electrode 21b.

The capacitance (capacitance) of the capacitance type sensor 2 can be obtained by the following equation (I).
C = ε ₀ ε _r S / d (I)
[C: capacitance, ε ₀ : dielectric constant in vacuum, ε _r : relative dielectric constant of dielectric film, S: electrode area, d: distance between electrodes]
For example, when the capacitive sensor 2 is pressed from above, the dielectric film 20 is compressed and correspondingly extends in the direction parallel to the surfaces of the electrodes 21a and 21b. As the film thickness, that is, the inter-electrode distance d decreases, the capacitance between the electrodes 21a and 21b increases. The magnitude and position of the applied load are detected by this capacitance change.

  Here, the dielectric film 20 is flexible. For this reason, the dielectric film 20 is easily deformed with respect to a load applied from the outside. That is, the displacement amount of the interelectrode distance d is large. The relative dielectric constant of the dielectric film 20 is large. For this reason, the change of the electrostatic capacitance with respect to the load is large. Therefore, the detection sensitivity of the capacitive sensor 2 is high. Further, the dielectric film 20 is difficult to break down. Therefore, the capacitive sensor 2 is excellent in durability.

[Third embodiment]
An embodiment of a power generation element will be described as a third example of the transducer of the present invention. In FIG. 3, the cross-sectional schematic diagram of the electric power generating element of this embodiment is shown. (A) shows the time of expansion, and (b) shows the time of contraction. As shown in FIG. 3, the power generation element 3 includes a dielectric film 30 and electrodes 31a and 31b. The dielectric film 30 is made of a crosslinked material obtained by crosslinking an elastomer composition containing hydrogenated nitrile rubber (elastomer) and diallyl dicarbonate (polar compound). The dielectric film 30 is included in the dielectric film of the present invention. The electrodes 31a and 31b are fixed to the upper and lower surfaces of the dielectric film 30, respectively. Conductive wires are connected to the electrodes 31a and 31b, and the electrode 31b is grounded.

  As shown in FIG. 3A, when the power generating element 3 is compressed and the dielectric film 30 is extended in a direction parallel to the surfaces of the electrodes 31a and 31b, the thickness of the dielectric film 30 is reduced, and between the electrodes 31a and 31b. The charge is stored in Thereafter, when the compressive force is removed, the dielectric film 30 contracts due to the elastic restoring force of the dielectric film 30 and the film thickness increases as shown in FIG. At that time, electric charges are released and electric power is generated.

  Here, the dielectric constant of the dielectric film 30 is large. For this reason, many electric charges can be stored in the interface with electrode 31a, 31b. The dielectric film 30 is flexible. For this reason, it is easy to expand and contract the dielectric film 30. That is, the expansion / contraction amount of the dielectric film 30 is large. Therefore, the power generation amount of the power generation element 3 is large. Further, the dielectric film 30 is difficult to break down. Therefore, the power generating element 3 is excellent in durability.

[Fourth embodiment]
As a fourth example of the transducer of the present invention, an embodiment embodied in a speaker will be described. First, the configuration of the speaker of this embodiment will be described. FIG. 4 shows a perspective view of the speaker of this embodiment. FIG. 5 shows a VV cross-sectional view of FIG. As shown in FIGS. 4 and 5, the speaker 4 includes a first outer frame 40a, a first inner frame 41a, a first dielectric film 42a, a first outer electrode 43a, a first inner electrode 44a, One diaphragm 45a, a second outer frame 40b, a second inner frame 41b, a second dielectric film 42b, a second outer electrode 43b, a second inner electrode 44b, a second diaphragm 45b, A bolt 460, eight nuts 461, and eight spacers 462 are provided.

  The first outer frame 40a and the first inner frame 41a are each made of resin and have a ring shape. The first dielectric film 42a has a circular thin film shape. The first dielectric film 42a is made of a crosslinked material obtained by crosslinking an elastomer composition containing hydrogenated nitrile rubber (elastomer) and diallyl dicarbonate (polar compound). The first dielectric film 42a is included in the dielectric film of the present invention. The first dielectric film 42a is stretched between the first outer frame 40a and the first inner frame 41a. That is, the first dielectric film 42a is sandwiched and fixed by the front-side first outer frame 40a and the back-side first inner frame 41a in a state in which a predetermined tension is secured.

  The first diaphragm 45a is made of resin and has a disk shape. The first diaphragm 45a has a smaller diameter than the first dielectric film 42a. The first diaphragm 45a is disposed approximately at the center of the surface of the first dielectric film 42a. The first outer electrode 43a is made of a flexible conductive material and has a ring shape. The first outer electrode 43a is attached to the surface of the first dielectric film 42a. The first inner electrode 44a is also made of a flexible conductive material and has a ring shape. The first inner electrode 44a is adhered to the back surface of the first dielectric film 42a. The first outer electrode 43a and the first inner electrode 44a face away from each other across the first dielectric film 42a. As shown in FIG. 5, the first outer electrode 43a includes a terminal 430a. The first inner electrode 44a includes a terminal 440a. A voltage is applied to the terminals 430a and 440a from the outside.

  Configurations of the second outer frame 40b, the second inner frame 41b, the second dielectric film 42b, the second outer electrode 43b, the second inner electrode 44b, and the second diaphragm 45b (hereinafter collectively referred to as “second member”). The first outer frame 40a, the first inner frame 41a, the first dielectric film 42a, the first outer electrode 43a, the first inner electrode 44a, the first diaphragm 45a (hereinafter referred to as “first member”). This is the same as the configuration, material, and shape. The arrangement of the second member is symmetrical with the arrangement of the first member in the front and back direction. In brief, the second dielectric film 42b is stretched between the second outer frame 40b and the second inner frame 41b. The second diaphragm 45b is disposed substantially at the center of the surface of the second dielectric film 42b. The second outer electrode 43b is printed on the surface of the second dielectric film 42b. The second inner electrode 44b is printed on the back surface of the second dielectric film 42b. A voltage is applied from the outside to the terminal 430b of the second outer electrode 43b and the terminal 440b of the second inner electrode 44b.

  The first member and the second member are fixed by eight bolts 460 and eight nuts 461 via eight spacers 462. A set of “bolt 460 -nut 461 -spacer 462” is arranged in the circumferential direction of the speaker 4 at a predetermined interval. The bolt 460 penetrates from the surface of the first outer frame 40a to the surface of the second outer frame 40b. The nut 461 is screwed to the penetrating end of the bolt 460. The spacer 462 is made of resin and is mounted around the shaft portion of the bolt 460. The spacer 462 ensures a predetermined interval between the first inner frame 41a and the second inner frame 41b. The back surface of the center part of the first dielectric film 42a (the back side of the part where the first diaphragm 45a is disposed) and the back surface of the center part of the second dielectric film 42b (the back side of the part where the second diaphragm 45b is disposed). And are joined. Therefore, a biasing force is accumulated in the first dielectric film 42a in the direction indicated by the white arrow Y1a in FIG. Further, an urging force is accumulated in the second dielectric film 42b in the direction indicated by the white arrow Y1b in FIG.

  Next, the movement of the speaker of this embodiment will be described. Through the terminals 430a and 440a and the terminals 430b and 440b, the first outer electrode 43a and the first inner electrode 44a, and the second outer electrode 43b and the second inner electrode 44b are in an initial state (offset state). A predetermined voltage (offset voltage) is applied. When the speaker 4 is in operation, voltages having opposite phases are applied to the terminals 430a and 440a and the terminals 430b and 440b.

  For example, when the offset voltage + 1V is applied to the terminals 430a and 440a, the thickness of the portion of the first dielectric film 42a disposed between the first outer electrode 43a and the first inner electrode 44a is thin. Become. In addition, the portion extends in the radial direction. At the same time, an antiphase voltage (offset voltage -1 V) is applied to the terminals 430b and 440b. Then, the film thickness of the part arrange | positioned between the 2nd outer electrode 43b and the 2nd inner electrode 44b among the 2nd dielectric films | membranes 42b becomes thick. In addition, the portion contracts in the radial direction. Thereby, the second dielectric film 42b is elastically deformed by its own urging force in the direction indicated by the white arrow Y1b in FIG. 5 while pulling the first dielectric film 42a. On the other hand, when the offset voltage + 1V is applied to the terminals 430b and 440b and the reverse phase voltage (offset voltage -1V) is applied to the terminals 430a and 440a, the first dielectric film 42a pulls the second dielectric film 42b. However, it is elastically deformed by its own urging force in the direction indicated by the white arrow Y1a in FIG. In this way, the first diaphragm 45a and the second diaphragm 45b are vibrated to vibrate air and generate sound.

  Next, the effect of the speaker 4 of this embodiment is demonstrated. According to the speaker 4 of the present embodiment, the relative dielectric constant of the first dielectric film 42a and the second dielectric film 42b is large. Therefore, a large amount of electric charge is applied to the interface between the first dielectric film 42a and the first outer electrode 43a and the first inner electrode 44a, and to the interface between the second dielectric film 42b and the second outer electrode 43b and the second inner electrode 44b. Can be stored. The first dielectric film 42a and the second dielectric film 42b are flexible. For this reason, the first dielectric film 42a and the second dielectric film 42b can be easily expanded and contracted. That is, the amount of expansion / contraction of the first dielectric film 42a and the second dielectric film 42b with respect to the applied voltage is large. Therefore, the electric field response of the speaker 4 is good. Further, the first dielectric film 42a and the second dielectric film 42b are unlikely to break down. Therefore, the speaker 4 is excellent in durability.

  The first outer electrode 43a, the first inner electrode 44a, the second outer electrode 43b, and the second inner electrode 44b are made of a flexible conductive material. Therefore, the first dielectric film 42a and the second dielectric film 42b can be deformed following the deformation. That is, the movement of the first dielectric film 42a and the second dielectric film 42b is not easily hindered by the electrodes 43a, 44a, 43b, and 44b. Furthermore, even if the electrodes 43a, 44a, 43b, and 44b are extended, the increase in electrical resistance is small. For this reason, the electric field responsiveness of the speaker 4 is good.

  Next, the present invention will be described more specifically with reference to examples.

<Manufacture of dielectric film>
[Dielectric film of Example 1]
First, hydrogenated nitrile rubber ("Zetpol (registered trademark) 1000L" manufactured by Nippon Zeon Co., Ltd., relative dielectric constant: about 13 (100 Hz)) was dissolved in methyl ethyl ketone (MEK). Subsequently, a polar compound, diallyl dicarbonate (relative dielectric constant: about 20 (100 Hz)), was added to the solution to prepare an elastomer composition. Next, the prepared elastomer composition was applied onto a substrate, and the coating film was dried at 80 ° C. for about 30 minutes. Then, the coating film was irradiated with a 300 kGy electron beam for crosslinking. Thus, the dielectric film of Example 1 was obtained. The film thickness of the dielectric film of Example 1 is about 40 μm.

[Dielectric film of Comparative Example 1]
The difference between the dielectric film of Example 1 and the dielectric film of Comparative Example 1 is the presence or absence of a polar compound. That is, a dielectric film of Comparative Example 1 was produced in the same manner as in Example 1 except that the elastomer composition was prepared without adding diallyl dicarbonate. The film thickness of the dielectric film of Comparative Example 1 is about 40 μm.

<Physical properties of dielectric film>
[Measurement of MEK insoluble matter]
For the dielectric film of Example 1, it was confirmed whether or not a polar compound was grafted to the elastomer. First, 1 g of the dielectric film of Example 1 was prepared as a sample. Next, the sample was immersed in 40 ml of MEK used for manufacturing the dielectric film at room temperature for 4 hours. Thereafter, the mass of the sample (MEK insoluble matter) remaining without being dissolved in MEK was measured. And the mass ratio of the MEK insoluble part with respect to 1g of samples before MEK immersion was computed. On the other hand, for comparison, the mass ratio of MEK insoluble matter was calculated in the same manner for the dielectric film of Comparative Example 1 made of only an elastomer.

  The measurement results are shown in Table 1 below. As shown in Table 1, the mass ratio of MEK insoluble matter in the dielectric film of Example 1 was 97.81%. Moreover, the mass ratio of the MEK insoluble matter in the dielectric film of Comparative Example 1 was 97.79%. Thus, the mass ratio of both MEK insolubles was substantially the same value. Moreover, all were values close to 100% by mass. From the above, it was confirmed that in the dielectric film of Example 1, the polar compound was grafted to the elastomer.

[Measurement of volume resistivity]
The volume resistivity of the dielectric films of Example 1 and Comparative Example 1 was measured according to JIS K 6911 (1995). The measurement was performed by applying a DC voltage of 100V. The measurement results are shown in Table 1 below. As shown in Table 1, the volume resistivity of the dielectric film of Example 1 was substantially the same value as the volume resistivity of the dielectric film of Comparative Example 1. From this, it can be seen that the dielectric film of Example 1 maintains high dielectric breakdown resistance.

[Measurement of relative permittivity]
The relative dielectric constants of the dielectric films of Example 1 and Comparative Example 1 were measured. For measurement of relative dielectric constant, each dielectric film is placed in a sample holder (Solartron, type 12962A), and a dielectric constant measurement interface (manufactured by the company, type 1296) and a frequency response analyzer (made by the company, type 1255B) are used in combination. And measured (frequency 100 Hz). The measurement results are shown in Table 1 below. As shown in Table 1, the relative dielectric constant of the dielectric film of Example 1 was larger than that of the dielectric film of Comparative Example 1.

<Actuator evaluation>
Next, an actuator was manufactured using each dielectric film of Example 1 and Comparative Example 1, and the generated stress of the actuator was measured. First, an experimental apparatus and an experimental method will be described.

  Electrodes obtained by mixing carbon black with acrylic rubber were adhered to both the front and back surfaces of each dielectric film of Example 1 and Comparative Example 1 to produce an actuator. Hereinafter, the manufactured actuators are referred to as the actuator of Example 1 and the actuator of Comparative Example 1 in accordance with the types of dielectric films. FIG. 6 shows a front side view of the actuator attached to the experimental apparatus. FIG. 7 shows a cross-sectional view in the VII-VII direction of FIG.

  As shown in FIGS. 6 and 7, the upper end of the actuator 5 is held by the upper chuck 52 in the experimental apparatus. The lower end of the actuator 5 is gripped by the lower chuck 53. The actuator 5 is attached between the upper chuck 52 and the lower chuck 53 in a state in which the actuator 5 is previously stretched in the vertical direction (stretching ratio 25%). A load cell (not shown) is disposed above the upper chuck 52.

  The actuator 5 includes a dielectric film 50 and a pair of electrodes 51a and 51b. The dielectric film 50 is in a natural state and has a rectangular thin film shape with a length of 50 mm, a width of 25 mm, and a thickness of about 40 μm. The electrodes 51a and 51b are arranged to face each other in the front and back direction with the dielectric film 50 interposed therebetween. The electrodes 51a and 51b are in a natural state and each have a rectangular thin film shape with a length of 38 mm, a width of 20 mm, and a thickness of about 10 μm. The electrodes 51a and 51b are arranged in a state shifted by 8 mm in the vertical direction. That is, the electrodes 51a and 51b overlap with each other through the dielectric film 50 in a range of 30 mm in length and 20 mm in width. A conducting wire (not shown) is connected to the lower end of the electrode 51a. Similarly, a conducting wire (not shown) is connected to the upper end of the electrode 51b. The electrodes 51a and 51b are connected to a power source (not shown) via respective conductive wires.

  When a voltage is applied between the electrodes 51a and 51b, an electrostatic attractive force is generated between the electrodes 51a and 51b, and the dielectric film 50 is compressed. Thereby, the thickness of the dielectric film 50 becomes thin and extends in the extending direction (vertical direction). Due to the extension of the dielectric film 50, the stretching force in the vertical direction decreases. The stretching force decreased before and after the voltage application was measured with a load cell, and used as the generated stress. The generated stress was measured until the applied voltage was increased stepwise until the dielectric film 50 was broken. The generated stress when the electric field strength is 20 V / μm in each of the actuators of Example 1 and Comparative Example 1 is summarized in Table 1 above.

  As shown in Table 1, the generated stress of the actuator of Example 1 was larger than the generated stress of the actuator of Comparative Example 1. From the above, it can be seen that the dielectric film of the present invention can constitute an actuator with a large output.

  The dielectric film of the present invention can be widely used in actuators, sensors, power generation elements, etc. that convert between mechanical energy and electrical energy, or transducers such as speakers, microphones, noise cancellers, etc., that convert between acoustic energy and electrical energy. . Especially, it is suitable for flexible actuators used for artificial muscles for industrial, medical, and welfare robots, small pumps for cooling electronic components, medical devices, and medical instruments.

1: Actuator (transducer) 10: Dielectric film 11a, 11b: Electrode 12: Power supply 2: Capacitance type sensor (transducer) 20: Dielectric film 21a, 21b: Electrode 22: Substrate 3: Power generation element (transducer) 30: Dielectric Membrane 31a, 31b: Electrode 4: Speaker (transducer)
40a: first outer frame 40b: second outer frame 41a: first inner frame 41b: second inner frame 42a: first dielectric film 42b: second dielectric film 43a: first outer electrode 43b: second outer electrode 44a: First inner electrode 44b: Second inner electrode 45a: First diaphragm 45b: Second diaphragm 430a, 430b, 440a, 440b: Terminal 460: Bolt 461: Nut 462: Spacer 5: Actuator 50: Dielectric films 51a, 51b : Electrode 52: Upper chuck 53: Lower chuck

Claims (6)

A dielectric film interposed between at least a pair of electrodes in the transducer,
A crosslinked product obtained by crosslinking an elastomer composition comprising an elastomer and a polar compound having a relative dielectric constant larger than that of the elastomer and capable of binding to the elastomer;
The dielectric film, wherein the polar compound is graft-bonded to the elastomer in the crosslinked product. The dielectric film according to claim 1, wherein the elastomer has a volume resistivity of 10 ⁹ Ω · cm or more.   The dielectric film according to claim 1, wherein the polar compound has one or more selected from a carbon-carbon double bond, a hydroxyl group, an amino group, a carboxyl group, a thiol group, and a halogenated alkyl group.   The dielectric film according to claim 1, wherein the polar compound has a structure or a functional group of any one of sulfoxide, sulfonamide, carbonate, and cyano group.   The elastomer is nitrile rubber, hydrogenated nitrile rubber, carboxyl-modified hydrogenated nitrile rubber, acrylic rubber, natural rubber, isoprene rubber, ethylene-propylene-diene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate- The acrylate ester copolymer, butyl rubber, styrene-butadiene rubber, fluorine rubber, silicone rubber, epichlorohydrin rubber, chloroprene rubber, chlorinated polyethylene, chlorosulfonated polyethylene and urethane rubber are one or more selected from claims 1 to 3. 4. The dielectric film according to any one of 4 above. An elastomer composition comprising an elastomer and a polar compound having a relative dielectric constant greater than that of the elastomer and capable of binding to the elastomer, wherein the polar compound is graft-bonded to the elastomer. A dielectric film,
A plurality of electrodes disposed via the dielectric film;
A transducer comprising:

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