WO2018061393A1 - Dielectric elastomer material and transducer using same - Google Patents

Abstract

Provided is a dielectric elastomer material which contains a copolymer having a structure in which a monomer A and/or a monomer C having a crosslinkable functional group and a monomer B having a polar group are randomly or alternately copolymerized. In constituent units comprising the monomer B in the copolymer, the polar group is bonded to the main polymer chain via 3 or more atoms connected in the form of a straight chain. A transducer (1) is provided with a dielectric layer (10) comprising the dielectric elastomer material and a plurality of electrodes (11a and 11b) disposed with the dielectric layer (10) interposed therebetween.

Description

Dielectric elastomer material and transducer using the same

The present invention relates to a dielectric elastomer material suitable for a dielectric layer of a transducer.

Known transducers include actuators, sensors, power generation elements, etc. that convert mechanical energy and electrical energy, or speakers, microphones, etc. that convert acoustic energy and electrical energy. Polymer materials such as dielectric elastomers are useful for constructing highly flexible, small and light transducers.

For example, an electrostrictive actuator can be configured by arranging a pair of electrodes on both sides in the thickness direction of a dielectric layer made of a dielectric elastomer. This type of actuator drives a member to be driven by extending and contracting a dielectric layer according to the magnitude of a voltage applied between electrodes. The generated force and displacement amount of the actuator are determined by the magnitude of the applied voltage and the magnitude of the electrostatic attraction generated between the electrodes. That is, the greater the electrostatic attractive force that can be applied between the electrodes and the greater the electrostatic attractive force generated between the electrodes, the greater the generated force and displacement of the actuator.

Similarly, a sensor and a power generation element can be configured by arranging a pair of electrodes on both sides in the thickness direction of a dielectric layer made of a dielectric elastomer. In the sensor and the power generation element, an electromotive force is generated when the dielectric layer expands and contracts. The amount of electromotive force generated is proportional to the amount of displacement of the interelectrode distance and the relative dielectric constant of the dielectric layer. That is, the greater the amount of displacement of the interelectrode distance and the greater the relative dielectric constant of the dielectric layer, the greater the electromotive force.

For example, silicone rubber has excellent dielectric breakdown resistance but low dielectric constant. For this reason, when the dielectric layer is formed from silicone rubber, the electrostatic attractive force with respect to the applied voltage is small, and it is difficult to obtain a desired generated force and displacement in the actuator. In addition, it is difficult to obtain a desired electromotive force in the sensor and the power generation element. On the other hand, acrylic rubber and nitrile rubber have a relative dielectric constant larger than that of silicone rubber, but it is still not sufficient. For this reason, attempts have been made to improve the dielectric constant of the dielectric layer by introducing polar groups into the base elastomer or dispersing particles having a large dielectric constant.

For example, Patent Document 1 describes an artificial muscle including a stretchable thin film made of an electrostrictive polymer in which a polar group is introduced into a side chain such as silicone rubber and a stretchable electrode. Patent Document 2 describes a polymer material obtained by crosslinking a copolymer of (meth) acrylic acid ester, (meth) acrylic acid, ionic liquid, and acrylonitrile. Patent Document 3 describes a dielectric for a polymer actuator comprising a block copolymer (A) having a polymer block (B1) of methyl methacrylate and a polymer block (B2) of an alkyl acrylate ester. Has been. Paragraph [0040] of Patent Document 3 describes a form in which the polymer blocks (B1) and (B2) contain a monomer having a polar group as a subcomponent for the purpose of improving the relative dielectric constant. Patent Document 4 describes an elastomer dielectric film in which a polar compound is grafted. Patent Document 5 describes an elastomeric dielectric film in which nanoparticles having a cyano group are dispersed.

JP 2008-199784 A Japanese Patent Laying-Open No. 2015-67662 International Publication No. 2009/025187 JP 2011-072112 A Japanese Patent Laying-Open No. 2015-187931

When polar groups are introduced into the elastomer, the polarity of the elastomer increases and the relative dielectric constant increases. In this case, the generated force obtained when the voltage is applied is increased according to the following equation (i). For this reason, conventionally, in order to increase the relative dielectric constant of the dielectric layer, studies have been made from the viewpoint of how much polar groups are contained.
F = ε ₀ ε _r × (V / d) ² (i)
[F: generated force, ε ₀ : dielectric constant of vacuum, ε _r : relative dielectric constant of dielectric layer, V: applied voltage, d: thickness of dielectric layer]
However, as a result of intensive studies by the present inventors, it has been found that even if the amount of polar groups in the elastomer is simply increased, the effect of improving the dielectric constant cannot be sufficiently obtained simply by increasing the elastic modulus. It was. The reason is considered to be that when the amount of polar groups increases, polar groups or polar groups and polymer chains interfere with each other, or polar groups aggregate due to interaction. For example, acrylonitrile has a polar group (cyano group: —CN). However, polyacrylonitrile obtained by polymerizing this is hard and has a relative dielectric constant of about 4, which is not high. The polymer material described in Patent Document 2 is copolymerized with acrylonitrile. However, this alone is not sufficient for improving the dielectric constant. In addition, paragraph [0028] of the same document describes that when the acrylonitrile content exceeds 45 mass%, the elastic modulus increases.

The present invention has been made in view of such circumstances, and an object thereof is to provide a flexible dielectric elastomer material having a large relative dielectric constant. Another object of the present invention is to provide a flexible transducer using the dielectric elastomer material.

(1) The dielectric elastomer material of the present invention has a structure in which at least one of a monomer A, a monomer C having a crosslinkable functional group, and a monomer B having a polar group are randomly or alternately copolymerized. In the copolymer, in the structural unit consisting of the monomer B, the polar group is bonded to the polymer main chain via three or more atoms linked in a straight chain. And

The copolymer constituting the dielectric elastomer material of the present invention includes a structural unit composed of monomer B having a polar group. The polar group is a functional group having high polarity. In the structural unit composed of the monomer B, the polar group is bonded to the polymer main chain via three or more atoms connected in a straight chain. In other words, at least three atoms bonded in series are interposed between the polar group and the polymer main chain. By separating the polar group from the polymer main chain, the polar group is less likely to interfere with the polymer chain, and the movement of the polar group is less likely to be regulated by the polymer chain. This makes it easier for the polar groups to move, thereby increasing the flexibility of the copolymer and thus the dielectric elastomer material. In addition, since the characteristics of the polar group having a high polarity are fully exhibited, the relative dielectric constant of the copolymer, and hence the dielectric elastomer material, can be increased.

The copolymer constituting the dielectric elastomer material of the present invention has a random copolymer structure or an alternating copolymer structure composed of at least one of the monomer A and the monomer C and the monomer B. The constitutional unit of the copolymer is any one of AB, BC, and ABC (the order of repeating units is not limited). Since each structural unit is couple | bonded at random or alternately, compared with the structure of a block copolymer, the structural unit which consists of the monomer B which has a polar group cannot continue easily. That is, the structural unit consisting of the monomer B having a polar group is unlikely to be adjacent to each other. Thereby, interference of polar groups is suppressed and a polar group becomes easy to move. Therefore, the flexibility of the copolymer, and thus the dielectric elastomer material, can be increased. In addition, since the characteristics of the polar group having a high polarity are fully exhibited, the relative dielectric constant of the copolymer, and hence the dielectric elastomer material, can be increased.

The block described in Patent Document 3 is a block copolymer. As described in paragraphs [0056]-[0060] of the same document, the block copolymer (A) is prepared after the first polymer block (B1) is produced, and then the second polymer block (B2 ) And connected to the first polymer block (B1). In the produced polymer blocks (B1) and (B2), the same monomer is continuous. For this reason, when a polymer block is produced by adding a monomer having a polar group, the polar groups interfere with each other, and the effect of improving the relative dielectric constant is small.

(2) A transducer according to the present invention includes a dielectric layer made of the dielectric elastomer material according to the present invention, and a plurality of electrodes disposed via the dielectric layer.

As described above, the dielectric constant of the dielectric elastomer material of the present invention is large. For this reason, in the dielectric layer of the transducer of this invention, the electrostatic attraction with respect to an applied voltage is large. In addition, the dielectric elastomer material of the present invention is flexible. Therefore, according to the transducer of the present invention, a large force and displacement can be obtained even when the applied voltage is relatively small.

It is a cross-sectional schematic diagram of the actuator which is one Embodiment of the transducer of this invention. It is a front side view of the actuator attached to the measuring device. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. It is a top view of the actuator for displacement amount measurement. FIG. 5 is a VV cross-sectional view of FIG. 4.

1: Actuator (transducer), 10: Dielectric layer, 11a, 11b: Electrode, 12a, 12b: Wiring.
5: Actuator, 50: Dielectric layer, 51a, 51b: Electrode, 52: Upper chuck, 53: Lower chuck.
6: Actuator, 60: Dielectric layer, 61a, 61b: Electrode, 62: Power supply, 63: Displacement meter, 610a, 610b: Terminal part, 630: Marker.

Hereinafter, embodiments of the dielectric elastomer material and the transducer of the present invention will be described. Note that the dielectric elastomer material and transducer of the present invention are not limited to the following forms, 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 elastomer material>
The dielectric elastomer material of the present invention is a copolymer having a structure in which at least one of monomer A, monomer C having a crosslinkable functional group, and monomer B having a polar group are randomly or alternately copolymerized. Includes coalescence.

[Monomer A]
The monomer A is not particularly limited. When the dielectric elastomer material of the present invention is used as a dielectric layer of a transducer, it is desirable to select a monomer that can exhibit flexibility and has a relatively high relative dielectric constant. Further, it is desirable to select a monomer that can be copolymerized with the monomer B and has a glass transition point (Tg) as a copolymer that is not higher than normal temperature (20 ° C.). Examples thereof include monomers used for isoprene rubber, butadiene rubber, ethylene propylene rubber, nitrile rubber, chloroprene rubber, butyl rubber, chlorosulfonated polyethylene rubber, fluororubber, thermoplastic elastomer, acrylic rubber, silicone rubber, and urethane rubber. Among these, from the viewpoint of easy copolymerization with the monomer B, monomers used for acrylic rubber, silicone rubber, and urethane rubber, that is, (meth) acrylate monomer, silicone monomer, and urethane monomer are preferable. Monomer A may be one type or two or more types.

The notation “(meth) acrylate” means that both acrylate and methacrylate are included. The (meth) acrylate monomer means a monomer having a (meth) acryloyl group. The expression “(meth) acryloyl group” means that both an acryloyl group and a methacryloyl group are included. (Meth) acrylate monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) Acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, dodecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) Alkyl (meth) acrylates such as acrylate are preferred.

When employing alkyl (meth) acrylate, the alkyl group preferably has 1 to 12 carbon atoms. It is more preferable that it is 8 or less. As the number of carbon atoms increases, the alkyl group becomes longer or larger. In this case, the polar group of monomer B tends to interfere with the alkyl group of monomer A, and the effect of improving the relative dielectric constant may be reduced. Moreover, when an alkyl group becomes long, crystallinity will increase and flexibility will fall.

Silicone monomer means a monomer capable of siloxane bond. As the silicone monomer, diethoxydimethylsilane, diethoxymethylsilane, diethoxymethylvinylsilane, dimethoxydimethylsilane, dimethoxy (methyl) silane, dimethoxymethylvinylsilane and the like having a bifunctional alkoxy group are suitable. The urethane monomer means a monomer capable of urethane bonding.

[Monomer B]
Monomer B has a polar group. The polar group is preferably a functional group consisting of a bond having a high dipole moment that correlates with the relative dielectric constant. Specific examples include cyano groups, ether groups, ester groups, fluorine groups, trifluoromethyl groups, carbonate groups, which are known highly polar groups.

In the copolymer, in the structural unit consisting of monomer B, the polar group is bonded to the polymer main chain via three or more atoms linked in a straight chain. The number of atoms interposed in series between the polar group and the polymer main chain is more preferably 4 or more from the viewpoint of flexibility and polymerization control. When there are a plurality of polar groups, the number of atoms interposed between the polar group closest to the polymer main chain and the polymer main chain is counted. The atoms interposed in series between the polar group and the polymer main chain are preferably at least one selected from carbon (C), oxygen (O), nitrogen (N), and sulfur (S). For example, the skeleton of the monomer B excluding the polar group is a silane having an alkyl (meth) acrylate having 2 or more carbon atoms in the alkyl group, a bifunctional alkoxy group, and an alkyl group having 2 or more carbon atoms. Is mentioned.

To sum up the above, the monomer B is composed of cyanomethyl (meth) acrylate (polymer main chain—3 atoms between cyano groups), cyanoethyl (meth) acrylate (polymer main chain—4 atoms between cyano groups), cyanopropyl ( Preferable examples include meth) acrylate (polymer main chain—5 atoms between cyano groups) and cyanobutyl (meth) acrylate (polymer main chain—6 atoms between cyano groups). In addition, cyano group-modified silane obtained by reacting acrylonitrile with dimethoxy-3-mercaptopropylmethylsilane (the number of atoms between the polymer main chain and the cyano group is 6), dimethoxy-3-mercaptopropylmethylsilane with 2-methyleneglutaronitrile. A cyano group-modified silane (the number of atoms between the polymer main chain and the cyano group is 6) or the like reacted with One of these may be used alone, or two or more may be used in combination.

When the content of polar groups increases, the flexibility of the copolymer decreases. On the other hand, if there are too few polar groups, the effect of improving the relative dielectric constant cannot be obtained. For these reasons, the content of the polar group is preferably 10% by mass or more, preferably 12% by mass or more when the entire copolymer is 100% by mass. The content of the polar group is preferably 25% by mass or less, preferably 22% by mass or less, based on 100% by mass of the entire copolymer. For the same reason, it is desirable that the content of the monomer B is 50 mol% or more, preferably 60 mol% or more when the entire copolymer is 100 mol%. Further, the content of the monomer B is desirably 98 mol% or less, preferably 90 mol% or less, based on 100 mol% of the entire copolymer.

[Monomer C]
The monomer C has a crosslinkable functional group (crosslinking group) and plays a role of crosslinking the copolymer. Examples of the crosslinkable functional group include a hydroxy group, an amino group, a thiol group, a carboxyl group, a silanol group, an epoxy group, and a vinyl group. When the dielectric elastomer material of the present invention is used as a dielectric layer of a transducer, it is desirable to select a monomer that can exhibit flexibility and has a relatively high relative dielectric constant as the monomer C. For example, (meth) acrylic acid, hydroxyethyl (meth) acrylate, (meth) acrylamide, glycidyl (meth) acrylate, 3-aminopropyldimethoxymethylsilane, dimethoxymethylvinylsilane, 3-glycidyloxypropyl (dimethoxy) methylsilane, Examples include 3-mercaptopropyl (dimethoxy) methylsilane, 3-aminopropyldiethoxymethylsilane, diethoxy (3-glycidyloxypropyl) methylsilane, and diethoxymethylvinylsilane. Monomer C may be one type or two or more types.

[Copolymer]
The copolymer constituting the dielectric elastomer material of the present invention has a random copolymer structure or an alternating copolymer structure composed of at least one of the monomer A and the monomer C and the monomer B. The method for producing the copolymer is not particularly limited. For example, random copolymer or alternating copolymer of monomer A and monomer B, random copolymer or alternating copolymer of monomer B and monomer C, random copolymer or alternating of monomer A, monomer B, and monomer C Any of the copolymers may be mentioned. Further, at least one of monomer A and monomer C and the precursor of monomer B (monomer B ′ having no polar group) are copolymerized randomly or alternately, and then the monomer having polar group is constituted of monomer B ′. You may make it react with a unit and synthesize | combine the structural unit which consists of the monomer B which has a polar group. That is, after a copolymer is produced from at least one of monomer A and monomer C and monomer B ′, a modification treatment for imparting a polar group to monomer B ′ may be performed. For example, when a cyano group is added, a cyano group-containing monomer such as acrylonitrile, 2-methyleneglutaronitrile, or tetracyanoethylene may be used.

The weight average molecular weight of the copolymer is preferably 10,000 or more from the viewpoint of ensuring flexibility. More preferably, it is 50,000 or more, further 80,000 or more. On the other hand, it is good that it is 5 million or less from the viewpoint of ensuring uniform solubility in a solvent required during film formation. More preferably, it is 2 million or less. The weight average molecular weight may be measured using a gel permeation chromatography (GPC) apparatus.

The glass transition point (Tg) of the copolymer is normal temperature (20 ° C.) or lower, and is preferably 5 ° C. or lower from the viewpoint of ensuring flexibility. More preferably, it is 0 ° C. or lower. The glass transition point may be measured using a differential scanning calorimeter (DSC).

The relative dielectric constant of the copolymer is preferably 10 or more. In this specification, a copolymer sample is placed in a sample holder (Solartron, model 12962A), and a dielectric constant measurement interface (manufactured by the company, model 1296) and a frequency response analyzer (manufactured by the company, model 1255B) are used together. Then, the relative dielectric constant is measured (measurement frequency: 100 Hz).

It is desirable that the copolymer has a crosslinked structure, that is, a crosslinked body. When it has a crosslinked structure, the elastic modulus increases and the mechanical strength increases. Also, the dielectric breakdown strength is increased. In order to cross-link the copolymer, a known cross-linking agent, cross-linking accelerator, cross-linking auxiliary or the like may be used according to the cross-linking group of the monomer C. For example, when sulfur is used, a reaction residue composed of unreacted sulfur, a vulcanization accelerator, or a decomposition product thereof often remains in the copolymer after crosslinking. The reaction residue is ionized and contributes to a decrease in the dielectric breakdown strength of the copolymer and thus the dielectric elastomer material. Therefore, it is desirable to use an organometallic compound or an isocyanate compound as a crosslinking agent because it reduces the ionic component in the copolymer. When an organometallic compound is used, metal oxide particles generated from the organometallic compound are dispersed in the copolymer. Therefore, the dielectric breakdown strength of the copolymer can be further increased. Examples of organometallic compounds include metal alkoxide compounds, metal acylate compounds, and metal chelate compounds. One kind selected from these may be used alone, or two or more kinds may be used in combination. The organometallic compound contains one or more elements selected from titanium, zirconium, aluminum, silicon, boron, vanadium, manganese, iron, cobalt, germanium, yttrium, niobium, lanthanum, cerium, tantalum, tungsten, and magnesium. desirable.

The dielectric elastomer material of the present invention may contain other components in addition to the copolymer. For example, when an insulating filler having electrical insulation is included, the dielectric breakdown strength of the dielectric elastomer material is increased. As the insulating filler, inorganic particles having a volume resistivity of 10 ⁸ Ω · cm or more are suitable. Examples thereof include particles of titanium oxide, silica, zirconium oxide, barium titanate, calcium carbonate, clay, fired clay, talc and the like. As an insulating filler, 1 type may be used independently and 2 or more types may be used together.

In the case of including a piezoelectric filler, the dielectric elastomer material of the present invention can be used as a piezoelectric layer of a transducer element having a piezoelectric function. As the piezoelectric filler, a piezoelectric compound may be used. The compound having piezoelectricity is not limited to an organic substance or an inorganic substance, and for example, a ferroelectric having a perovskite crystal structure is desirable. For example, barium titanate, strontium titanate, potassium niobate, sodium niobate, lithium niobate, potassium sodium niobate, lead zirconate titanate (PZT), barium strontium titanate (BST), bismuth lanthanum titanate (BLT) ), Bismuth strontium tantalate (SBT), and the like. As a piezoelectric filler, 1 type may be used independently and 2 or more types may be used together.

[Production method of dielectric elastomer material]
The dielectric elastomer material of the present invention can be produced by copolymerizing at least one of monomer A and monomer C and monomer B randomly or alternately. Alternatively, at least one of monomer A and monomer C and the precursor of monomer B (monomer B ′ having no polar group) are randomly or alternately copolymerized, and then the monomer having a polar group is converted to monomer B ′. It can be produced by reacting with a structural unit. At this time, a crosslinking agent or the like may be added to the obtained copolymer to crosslink the copolymer. Moreover, you may blend another polymer to such an extent that a function is not impaired. Moreover, you may mix | blend other components, such as an insulating filler, a piezoelectric filler, a plasticizer, a processing aid, an anti-aging agent, a softening agent, and a coloring agent, with the obtained copolymer.

<Transducer>
The transducer according to the present invention includes a dielectric layer made of the dielectric elastomer material according to the present invention, and a plurality of electrodes disposed via the dielectric layer.

The thickness of the dielectric layer is desirably 5 μm or more from the viewpoint of ensuring film formation accuracy and reducing film defects. On the other hand, when the thickness of the dielectric layer is increased, a large voltage is required for driving, resulting in an increase in cost. Therefore, the thickness of the dielectric layer is desirably 200 μm or less.

It is desirable that the plurality of electrodes can be deformed following the dielectric layer. Such an electrode can be formed using a binder and a conductive material. From the viewpoint of forming an electrode that does not easily increase in electrical resistance even when stretched, an elastomer is suitable as the binder. Elastomers include nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), ethylene-propylene-diene copolymer (EPDM), silicone rubber, natural rubber, styrene-butadiene rubber (SBR), acrylic rubber, urethane Examples thereof include crosslinked rubbers such as rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, and chlorinated polyethylene, and thermoplastic elastomers such as styrene, olefin, vinyl chloride, polyester, polyurethane, and polyamide. Moreover, you may use the elastomer modified | denatured by introduce | transducing a functional group like an epoxy group modified acrylic rubber, a carboxyl group modified hydrogenated nitrile rubber, etc.

The type of conductive material is not particularly limited. Conductive carbon powder such as carbon black, carbon nanotube, graphite, graphene, metal powder such as silver, gold, copper, nickel, rhodium, palladium, chromium, titanium, platinum, iron, and alloys thereof are selected as appropriate. That's fine. Moreover, you may use the powder which consists of particle | grains coat | covered with metals, such as silver covering copper powder. Alternatively, a conductive polymer having a structure in which π electrons are conjugated may be used. One of these may be used alone, or two or more may be used in combination.

The electrode may contain additives such as a dispersant, a reinforcing agent, a plasticizer, an anti-aging agent, and a colorant as required in addition to the binder and the conductive material. For example, when an elastomer is used as a binder, a conductive paint is prepared by adding a conductive material and, if necessary, an additive to a polymer solution obtained by dissolving the polymer for the elastomer in a solvent, and stirring and mixing. Can do. The electrode may be formed by directly applying the prepared conductive paint to one surface of the dielectric layer. Alternatively, an electrode may be formed by applying a conductive paint to the releasable film, and the formed electrode may be transferred to one surface of the dielectric layer.

If the transducer of the present invention has a laminated structure in which a plurality of dielectric layers and electrodes are alternately laminated, a larger force can be generated. In the transducer of the present invention, a protective layer may be disposed on the outermost layer. By disposing the protective layer, insulation can be ensured and the transducer can be protected from external mechanical stress. The protective layer is preferably flexible and stretchable. The protective layer may be formed including, for example, urethane rubber, silicone rubber, NBR, H-NBR, ethylene-propylene copolymer rubber, EPDM, natural rubber, styrene-butadiene rubber, acrylic rubber, and the like. In the transducer of the present invention, the same or different layers may be laminated to form a dielectric layer. Further, an ion fixed layer or the like having a charge amplification function may be stacked on the dielectric layer.

Hereinafter, an embodiment of the transducer of the present invention will be described. FIG. 1 shows a schematic sectional view of an actuator. As shown in FIG. 1, the actuator 1 includes a dielectric layer 10, a pair of electrodes 11a and 11b, and wirings 12a and 12b. The dielectric layer 10 is made of a crosslinked product of a random copolymer of butyl acrylate (monomer A), cyanoethyl acrylate (monomer B), and acrylic acid (monomer C). The structural formula of the random copolymer is shown in the following formula (1).

Monomer B has a cyano group (—CN) as a polar group. The monomer C has a carboxyl group (—COOH) as a crosslinking group. As shown in the formula (1), in the constituent unit consisting of the monomer B in the copolymer, the polar group (—CN) is linear with the carbon atom to which it is bonded as the first atom. It is connected to the polymer main chain via four linking atoms (C—C—O—C). The relative permittivity of the random copolymer is 15, and the elastic modulus is 0.8 MPa. The crosslinked body of the random copolymer is included in the dielectric elastomer material of the present invention. The actuator 1 is included in the transducer of the present invention.

The electrode 11a is arranged so as to cover substantially the entire upper surface of the dielectric layer 10. Similarly, the electrode 11b is disposed so as to cover substantially the entire lower surface of the dielectric layer 10. The electrodes 11a and 11b both contain acrylic rubber and carbon black. The electrodes 11a and 11b are connected to the power supply 13 via wirings 12a and 12b, respectively.

When a voltage is applied between the pair of electrodes 11a and 11b, the thickness of the dielectric layer 10 is reduced, and the portion extends in a direction parallel to the surfaces of the electrodes 11a and 11b. Thereby, the driving force in the vertical direction and the horizontal direction in the figure is output.

In the structural unit composed of the monomer B of the copolymer constituting the dielectric layer 10, four atoms connected in a straight chain are interposed between the polar group and the polymer main chain. That is, the polar group and the polymer main chain are separated at a predetermined interval. For this reason, the polar group does not easily interfere with the polymer chain, and the movement of the polar group is less likely to be regulated by the polymer chain. In addition, since the monomers A, B, and C are randomly copolymerized, the constituent units composed of the monomer B having a polar group are less likely to be continuous as compared with the case of block copolymerization. Thereby, interference of polar groups is suppressed and a polar group becomes easy to move. Accordingly, the flexibility of the copolymer is increased. In addition, since the polar group characteristic of high polarity is fully exhibited, the relative dielectric constant of the copolymer is increased. Therefore, the dielectric layer 10 is flexible and the dielectric constant of the dielectric layer 10 is large. Thereby, according to the actuator 1, a big force and displacement amount can be obtained. Further, when the structure of the actuator 1 is used as a sensor, a highly sensitive sensor can be realized.

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

<Manufacture of copolymer>
(1) Copolymer 1
First, 37.2 g (0.29 mol) of butyl acrylate of monomer A, 86.3 g (0.69 mol) of cyanoethyl acrylate of monomer B, and 1.4 g (0.02 mol) of acrylic acid of monomer C were used. The flask was placed in a neck flask and dissolved in 200 ml of N, N-dimethylformamide. Next, nitrogen bubbling was performed for 30 minutes. Then, azobisisobutyronitrile as a radical initiator was added in an amount of 0.1% by mass of the total mass of the monomer, and the mixture was heated to reflux at 65 ° C. for 14 hours in a nitrogen atmosphere. After completion of the reaction, methanol was used for reprecipitation, washing, and drying under reduced pressure to obtain a copolymer 1. When the obtained copolymer was analyzed with a nuclear magnetic resonance (NMR) apparatus, it was confirmed that the copolymer 1 was a random copolymer having the structure represented by the above formula (1) (hereinafter referred to as a copolymer). Same for polymers 2 and 3). The presence of a carboxyl group in the structural unit consisting of monomer C was confirmed by neutralization titration using a 0.1N potassium hydroxide methanol solution using a phenolphthalein solution as an indicator (hereinafter referred to as copolymers 2 to 12, Same in 18-21).

(2) Copolymer 2
Copolymer 2 was produced in the same manner as Copolymer 1, except that the amount of butyl acrylate was changed to 25.6 g (0.20 mol) and the amount of cyanoethyl acrylate was changed to 97.6 g (0.78 mol). .

(3) Copolymer 3
Copolymer 3 was produced in the same manner as Copolymer 1, except that the amount of butyl acrylate was changed to 12.8 g (0.10 mol) and the amount of cyanoethyl acrylate was changed to 110.1 g (0.88 mol). .

(4) Copolymer 4
A copolymer 4 was produced in the same manner as the copolymer 1 except that the monomer A was changed to 2-ethylhexyl acrylate. The blending amount of 2-ethylhexyl acrylate is 53.4 g (0.29 mol). When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 4 was a random copolymer having a structure represented by the following formula (2) (hereinafter, in the copolymers 5 and 6). the same).

(5) Copolymer 5
Copolymer 5 was prepared in the same manner as Copolymer 1, except that the amount of 2-ethylhexyl acrylate was changed to 36.9 g (0.20 mol) and the amount of cyanoethyl acrylate was changed to 97.6 g (0.78 mol). Manufactured.

(6) Copolymer 6
Copolymer 6 was prepared in the same manner as Copolymer 1, except that the amount of 2-ethylhexyl acrylate was changed to 18.4 g (0.10 mol) and the amount of cyanoethyl acrylate was changed to 110.1 g (0.88 mol). Manufactured.

(7) Copolymer 7
A copolymer 7 was produced in the same manner as the copolymer 1 except that the monomer A was changed to octyl acrylate. The blending amount of octyl acrylate is 53.4 g (0.29 mol). When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 7 was a random copolymer having a structure represented by the following formula (3) (hereinafter the same for the copolymer 8). .

(8) Copolymer 8
Copolymer 8 was produced in the same manner as Copolymer 7, except that the amount of octyl acrylate was changed to 36.9 g (0.20 mol) and the amount of cyanoethyl acrylate was changed to 97.6 g (0.78 mol). .

(9) Copolymer 9
A copolymer 9 was produced in the same manner as the copolymer 1 except that the monomer A was changed to ethyl acrylate. The amount of ethyl acrylate is 29.0 g (0.29 mol). When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 9 was a random copolymer having a structure represented by the following formula (4).

(10) Copolymer 10
First, DCEA as monomer B was produced. 2-Methyleneglutaronitrile 10.6 g (0.10 mol), 3-mercapto-1-propanol 9.2 g (0.10 mol), and diisopropylamine 0.62 ml were placed in an eggplant flask and dissolved in 100 ml of methanol. Then, the mixture was stirred at room temperature for 6 hours. After completion of the reaction, the reaction mixture was dried under reduced pressure, and further 100 ml of toluene, 7.2 g (0.10 mol) of acrylic acid, 0.5 g of p-toluenesulfonic acid, and 0.01 g of hydroquinone were added and heated to reflux for 6 hours. After completion of the reaction, the organic phase was recovered by a liquid separation operation using purified water and dried under reduced pressure to obtain DCEA having a structure represented by the following formula (5).

Next, 97.6 g (0.78 mol) of cyanoethyl acrylate of monomer B, 50.5 g (0.20 mol) of DCEA of monomer B, and 1.4 g (0.02 mol) of acrylic acid of monomer C The flask was placed in a flask and dissolved in 200 ml of N, N-dimethylformamide. Subsequently, nitrogen bubbling was performed for 30 minutes. Then, azobisisobutyronitrile as a radical initiator was added in an amount of 0.1% by mass of the total mass of the monomer, and the mixture was heated to reflux at 65 ° C. for 14 hours in a nitrogen atmosphere. After completion of the reaction, methanol was used for reprecipitation, washing, and drying under reduced pressure to obtain a copolymer 10. When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 10 was a random copolymer having a structure represented by the following formula (6).

(11) Copolymer 11
First, CEVE as monomer B was produced. 8.8 g (0.10 mol) of ethylene glycol monovinyl ether and 5.3 g (0.10 mol) of acrylonitrile were placed in an eggplant flask, dissolved in 100 ml of 2M aqueous sodium hydroxide solution, and stirred at room temperature for 6 hours. did. After completion of the reaction, the organic phase was collected by a liquid separation operation using dichloromethane and purified water, and dried under reduced pressure to obtain CEVE having a structure represented by the following formula (7).

Next, 18.0 g (0.34 mol) of acrylonitrile of monomer B, 90.4 g (0.64 mol) of CEVE of monomer B, and 1.4 g (0.02 mol) of acrylic acid of monomer C The flask was placed in a flask and dissolved in 200 ml of N, N-dimethylformamide. Subsequently, nitrogen bubbling was performed for 30 minutes. Then, azobisisobutyronitrile as a radical initiator was added in an amount of 0.1% by mass of the total mass of the monomer, and the mixture was heated to reflux at 65 ° C. for 14 hours in a nitrogen atmosphere. After completion of the reaction, methanol was used for reprecipitation, washing, and drying under reduced pressure to obtain a copolymer 11. When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 11 was a random copolymer having a structure represented by the following formula (8).

(12) Copolymer 12
Copolymer 12 was produced in the same manner as Copolymer 1, except that monomer A was not used and the amount of cyanoethyl acrylate was changed to 122.6 g (0.98 mol). When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 12 was a random copolymer having a structure represented by the following formula (9).

(13) Copolymer 13
A copolymer was used in the same manner as in Copolymer 1 except that monomer C was not used, but the amount of butyl acrylate was changed to 38.5 g (0.30 mol) and the amount of cyanoethyl acrylate was changed to 87.6 g (0.70 mol). Polymer 13 was produced. When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 13 was a random copolymer having a structure represented by the following formula (10).

(14) Copolymer 14
First, cyan group-modified silane 1 and cyan group-modified silane 2 as monomer B were produced.

[Cyan group-modified silane 1]
Acrylonitrile (5.3 g, 0.10 mol), dimethoxy-3-mercaptopropylmethylsilane (19.8 g, 0.11 mol) and diisopropylamine (0.62 ml) were placed in an eggplant flask and dissolved in methanol (100 ml). For 6 hours. After completion of the reaction, the reaction mixture was dried under reduced pressure to obtain cyan group-modified silane 1 having a structure represented by the following formula (11).

[Cyan group-modified silane 2]
10.6 g (0.10 mol) of 2-methyleneglutaronitrile, 19.8 g (0.11 mol) of dimethoxy-3-mercaptopropylmethylsilane and 0.62 ml of diisopropylamine were placed in an eggplant flask and dissolved in 100 ml of methanol. Then, the mixture was stirred at room temperature for 6 hours. After completion of the reaction, the reaction mixture was dried under reduced pressure to obtain cyan group-modified silane 2 having a structure represented by the following formula (12).

Next, a copolymer was produced from monomer A and monomer B without using monomer C. First, 40.9 g (0.34 mol) of diethoxydimethylsilane as monomer A, 77.0 g (0.33 mol) of cyan group-modified silane 1 and 94.5 g (0.33 mol) of cyan group-modified silane 2 as monomer B ) Was placed in an eggplant flask and stirred at room temperature for 1 hour. Subsequently, 10% by mass of dibutyltin diacetate as a catalyst was added to the total monomer mass, and the mixture was heated and stirred at 110 ° C. for 6 hours under atmospheric pressure. After completion of the reaction, methanol was used for reprecipitation, washing, and drying under reduced pressure to obtain a copolymer 14 (cyano group-modified silicone rubber). When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 14 was a random copolymer having a structure represented by the following formula (13). Here, diethoxydimethylsilane was treated as monomer A. However, diethoxydimethylsilane has a silanol group which is a crosslinkable functional group. For this reason, diethoxydimethylsilane may be handled as the monomer C (hereinafter, the same applies to the copolymers 15 to 17).

(15) Copolymer 15
A copolymer 15 was produced in the same manner as the copolymer 14 except that only 189.1 g (0.66 mol) of the cyan group-modified silane 2 was used as the monomer B. When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 15 was a random copolymer having a structure represented by the following formula (14).

(16) Copolymer 16
First, carbonate group-modified silane as monomer B was produced. 11.4 g (0.10 mol) of vinyl ethylene carbonate, 19.8 g (0.11 mol) of dimethoxy-3-mercaptopropylmethylsilane and 0.62 ml of diisopropylamine were placed in an eggplant flask and dissolved in 100 ml of methanol. And stirred at room temperature for 6 hours. After completion of the reaction, the residue was dried under reduced pressure to obtain a carbonate group-modified silane having a structure represented by the following formula (15).

Next, copolymer 16 was produced in the same manner as copolymer 14 except that only 194.3 g (0.66 mol) of carbonate group-modified silane was used as monomer B. When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 16 was a random copolymer having a structure represented by the following formula (16).

(17) Copolymer 17
Copolymer 17 was prepared in the same manner as Copolymer 14 except that 94.5 g (0.33 mol) of cyan group-modified silane 2 and 97.2 g (0.33 mol) of carbonate group-modified silane were used as monomer B. Manufactured. When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 17 was a random copolymer having a structure represented by the following formula (17).

(18) Copolymer 18
First, 1.25 g of carboxyl group-containing NBR (“XER-32” manufactured by JSR Corporation) was dissolved in 100 ml of tetrahydrofuran (THF), and then 0.5 M of 9-borabicyclo [3.3.1] nonane (9 -18.4 ml of a THF solution of -BBN) and 0.95 g of 5-chlorovaleronitrile were added and stirred for 0.5 hour. Subsequently, 1.90 g of potassium 2,6-di-tert-butylphenol was added in a water bath and stirred for 2 hours. After completion of the reaction, methanol was used for reprecipitation, washing, and drying under reduced pressure to obtain a copolymer 18 (cyano group-modified NBR). When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 18 was a random copolymer having a structure represented by the following formula (18).

(19) Copolymer 19
First, 88.4 g (0.69 mol) of butyl acrylate of monomer A, 15.4 g (0.29 mol) of acrylonitrile having a polar group, and 1.4 g (0.02 mol) of acrylic acid of monomer C Nitrogen bubbling was performed for 30 minutes in a three-necked flask. Next, 0.1% by mass of azobisisobutyronitrile as a radical initiator was added based on the total mass of the monomer, and the mixture was heated to reflux at 65 ° C. for 3 hours in a nitrogen atmosphere. After completion of the reaction, methanol was used for reprecipitation, washing, and drying under reduced pressure to obtain a copolymer 19. When the obtained copolymer was analyzed with an NMR apparatus, it was confirmed that the copolymer 19 was a random copolymer having a structure represented by the following formula (19) (hereinafter, in the copolymers 20, 21). the same).

(20) Copolymer 20
A copolymer 20 was produced in the same manner as the copolymer 19 except that the amount of butyl acrylate was changed to 69.2 g (0.54 mol) and the amount of acrylonitrile was changed to 23.3 g (0.44 mol).

(21) Copolymer 21
A copolymer 21 was produced in the same manner as the copolymer 19 except that the amount of butyl acrylate was changed to 62.8 g (0.49 mol) and the amount of acrylonitrile was changed to 26.0 g (0.49 mol).

<Measurement of physical properties of copolymer>
The weight average molecular weight of the produced copolymer was measured using a GPC apparatus, and the glass transition point was measured using DSC. Moreover, the measurement sample manufactured as follows was used for the measurement of the dielectric constant, volume resistivity, and elastic modulus of the copolymer. First, the copolymer was dissolved in acetylacetone to prepare a polymer solution having a solid content concentration of 20% by mass. Next, the prepared polymer solution was applied onto a substrate, dried, and then heated at 150 ° C. for 60 minutes to obtain a thin-film measurement sample.

[Relative permittivity]
As described above, the relative dielectric constant was measured at a frequency of 100 Hz using an apparatus manufactured by Solartron.

[Volume resistivity]
About volume resistivity, it measured according to the parallel terminal electrode method prescribed | regulated to JISK6271: 2008. The measurement was performed by applying a DC voltage of 100V.

[Elastic modulus]
The elastic modulus was measured according to the method for measuring the static shear modulus specified in JIS K6254: 2010. For the measurement, a strip-shaped No. 1 test piece was used, the tensile speed in the tensile test was 100 mm / min, and the tensile strain was 25%.

Tables 1 and 2 summarize the composition and physical properties of the copolymer. Copolymers 1 to 18 are included in the copolymer constituting the dielectric elastomer material of the present invention. For comparison, commercially available acrylic rubber (“Nipol (registered trademark) AR53L” manufactured by Nippon Zeon Co., Ltd.), silicone rubber (“KE-1935” manufactured by Shin-Etsu Chemical Co., Ltd.), and carboxyl group-containing NBR (JSR ( The physical properties of “XER-32”) are also shown.

Comparative Examples 1 to 13 and Comparative Examples 1 to 4, Examples 14 to 17 and Comparative Example 5, Examples 18 and Comparative Example 6, and the same base polymer were compared with each other. Was larger than that of the comparative example. The main difference between Examples 1 to 13 (Copolymers 1 to 13) and Comparative Examples 1 to 3 (Copolymers 19 to 21) is the type of monomer B. In Comparative Examples 1 to 3, acrylonitrile was used as monomer B. In this case, in the structural unit comprising the monomer B of the copolymers 19 to 21, the cyano group is directly bonded to the carbon of the polymer main chain. That is, no atom is interposed between the cyano group and the polymer main chain. Therefore, it is considered that the properties as a polar group are hardly exhibited because the cyano group interferes with the polymer chain.

Focusing on the copolymers 1 to 3, 4 to 6, 7, and 8 in the examples, it was confirmed that when the monomer B was the same, the relative dielectric constant and elastic modulus increased as the blending amount increased. It was. In contrast, in the copolymers 19 to 21 of the comparative examples, even if the blending amount of the monomer B is increased and the content of the cyano group is increased, the elastic modulus is increased, but the relative dielectric constant is increased. There wasn't. This is also because the cyano group is directly bonded to the carbon of the polymer main chain, so that the cyano group interferes with the polymer chain and the characteristics as a polar group are hardly exhibited.

Copolymers 10 to 17 of the examples are binary copolymers composed of monomers B and C or monomers A and B. In these cases, as in the case of the ternary copolymer composed of the monomers A, B, and C, an effect of improving the dielectric constant was observed.

<Actuator characteristics 1>
A dielectric layer was manufactured using the copolymers 1, 2, 11, 14, and 19, and an electrostrictive actuator including the dielectric layer was manufactured. First, the copolymer was dissolved in acetylacetone to prepare a polymer solution having a solid content concentration of 20% by mass. Next, 5 parts by mass of an acetone solution (concentration 20% by mass) of tetrakis (2-ethylhexyloxy) titanium as a crosslinking agent and 12.42 parts by mass of titanium oxide particles as an insulating filler are added to 100 parts by mass of the polymer solution. Thus, a mixed solution was prepared. The prepared mixed solution was applied onto a substrate, dried, and then heated at 150 ° C. for 60 minutes to produce a thin dielectric layer having a thickness of 10 μm. Separately, 10 parts by mass of carbon black was added to 100 parts by mass of the acrylic rubber polymer solution to prepare a conductive paint. The prepared conductive paint was applied onto a substrate, dried, and then heated at 150 ° C. for 60 minutes to produce a thin-film electrode having a thickness of 5 μm. The volume resistivity of the electrode is 5 Ω · cm. The manufactured electrodes were attached to both the front and back surfaces in the thickness direction of the dielectric layer to form a pair of electrodes. In this way, four types of actuators with different dielectric layers were manufactured. Copolymers 1, 2, 11, and 14 are included in the copolymer constituting the dielectric elastomer material of the present invention. The actuators of Examples 1, 2, 11, and 14 comprising dielectric layers made from copolymers 1, 2, 11, and 14 are included in the transducer of the present invention. In addition, dielectric layers were also produced from the above-mentioned commercially available acrylic rubber and silicone rubber, and electrodes were formed on both the front and back surfaces in the thickness direction of the dielectric layer in the same manner to produce an actuator. And about each actuator, the dielectric breakdown strength, the generated force, and the displacement amount were measured.

First, a measurement apparatus and a measurement method for dielectric breakdown strength will be described. FIG. 2 shows a front side view of the actuator attached to the measuring device. FIG. 3 is a cross-sectional view taken along the line III-III in FIG.

2 and 3, the upper end of the actuator 5 is gripped by the upper chuck 52 in the measuring 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 layer 50 and a pair of electrodes 51a and 51b. The dielectric layer 50 has a rectangular plate shape with a length of 50 mm and a width of 25 mm in a natural state. The electrodes 51a and 51b are arranged to face each other in the front and back direction with the dielectric layer 50 interposed therebetween. The electrodes 51a and 51b are in a natural state and each have a rectangular plate shape with a length of 40 mm, a width of 25 mm, and a thickness of about 10 μm. The electrodes 51a and 51b are arranged in a state shifted by 10 mm in the vertical direction. That is, the electrodes 51a and 51b overlap with each other through the dielectric layer 50 in a range of 30 mm length and 25 mm width. A wiring (not shown) is connected to the lower end of the electrode 51a. Similarly, a wiring (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) through each wiring.

The dielectric breakdown strength was measured until the dielectric layer 50 was broken by gradually increasing the voltage applied between the electrodes 51a and 51b. A value obtained by dividing the voltage value immediately before the dielectric layer 50 was broken by the thickness of the dielectric layer 50 was taken as the dielectric breakdown strength.

Next, an apparatus and a method for measuring generated force will be described. The generated force was measured using the same apparatus as that for measuring the dielectric breakdown strength (see FIGS. 2 and 3). 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 layer 50 is compressed. Thereby, the thickness of the dielectric layer 50 becomes thin and extends in the extending direction (vertical direction). The stretching force in the vertical direction decreases due to the elongation of the dielectric layer 50. The stretching force that decreased when the voltage was applied was measured by a load cell and used as the generated force. The generated force was measured at an electric field strength of 30 V / μm. Next, a displacement measuring device and a measuring method will be described. FIG. 4 shows a top view of the actuator. FIG. 5 shows a VV cross-sectional view of FIG. As shown in FIGS. 4 and 5, the actuator 6 includes a dielectric layer 60 and a pair of electrodes 61a and 61b. The dielectric layer 60 has a circular thin film shape with a diameter of 70 mm. The dielectric layer 60 is arranged in a state of being stretched 25% in the vertical and horizontal biaxial directions. The pair of electrodes 61a and 61b are arranged to face each other in the thickness direction with the dielectric layer 60 interposed therebetween. The electrodes 61a and 61b have a circular thin film shape with a diameter of about 27 mm, and are arranged substantially concentrically with the dielectric layer 60, respectively. A terminal portion 610a protruding in the diameter increasing direction is formed on the outer peripheral edge of the electrode 61a. The terminal portion 610a has a rectangular plate shape. Similarly, a terminal portion 610b protruding in the diameter increasing direction is formed on the outer peripheral edge of the electrode 61b. The terminal portion 610b has a rectangular plate shape. The terminal portion 610b is disposed at a position facing the terminal portion 610a by 180 °. The terminal portions 610a and 610b are each connected to the power source 62 via a conducting wire.

When a voltage is applied between the electrodes 61a and 61b, an electrostatic attractive force is generated between the electrodes 61a and 61b, and the dielectric layer 60 is compressed. Thereby, the thickness of the dielectric layer 60 becomes thin, and it expand | extends in the diameter expansion direction. At this time, the electrodes 61 a and 61 b are also integrated with the dielectric layer 60 and extend in the diameter increasing direction. A marker 630 is attached to the electrode 61a in advance. The displacement of the marker 630 was measured by the displacement meter 63 and used as the displacement amount of the actuator 6. The displacement was measured at an electric field strength of 30 V / μm. And the displacement rate was computed by following Formula (ii) from the measured displacement amount.
Displacement rate (%) = (displacement amount / radius of electrode) × 100 (ii)
Tables 3 and 4 show the measurement results of the generated force, displacement rate, and dielectric breakdown strength of each actuator.

As described above, the copolymers 1 and 2 and the copolymer 19 are different in the type of the monomer B, and the copolymers 1 and 2 have a higher relative dielectric constant. As a result, as shown in Tables 3 and 4, the actuators of Examples 1 and 2 including the dielectric layers manufactured from the copolymers 1 and 2 are compared with the dielectric layer manufactured from the copolymer 19. Compared with the actuator of Example 1, the generated force and the displacement rate increased. In addition, compared with the actuators of Comparative Examples 4 and 5 having a dielectric layer made of acrylic rubber or silicone rubber, the actuators of Examples 1, 2, 11, and 14 had higher generation force and displacement rate. .

<Actuator characteristics 2>
A dielectric layer was manufactured using the copolymers 1 and 11, and an electrostrictive actuator provided with the dielectric layer was manufactured. The structure of the manufactured actuator is the same as that in <Actuator characteristic 1> except that ion-fixed layers are laminated on both front and back surfaces in the thickness direction of the dielectric layer. That is, in the manufactured actuator, electrodes are arranged on both the front and back surfaces of a laminate composed of a cation fixed layer / dielectric layer / anion fixed layer. The manufacturing method of the dielectric layer and the electrode is the same as that in <Actuator characteristic 1>. Hereinafter, the anion fixing layer and the cation fixing layer (ion fixing layer) will be described.

[Anion fixed layer]
First, a reactive ionic liquid was produced. In 5.0 g of 1-butyl-3-methylimidazolium bicarbonate solution (solvent: methanol / water = 3: 2 mixed solution, concentration 50% by mass, 0.0125 mol), equimolar amount of acrylic acid monomer (0 0.0125 mol) was added dropwise on an ice bath. At that time, it was confirmed that bubbles appeared. After 30 minutes, the temperature was returned to room temperature and stirred for 6 hours. After depressurizingly distilling a solvent, methanol (super dehydration) (Wako Pure Chemical Industries) was added, and the solvent was depressurizingly distilled again. In this way, an ionic liquid monomer was obtained. 2.10 g (10.0 mmol) of the obtained ionic liquid monomer and 1.87 ml (10.1 mmol) of 3-mercaptopropyltrimethoxysilane were dissolved in 20 ml of methanol (super-dehydrated). 10 mol% of diisopropylamine as a catalyst with respect to 3-mercaptopropyltrimethoxysilane was added and stirred at room temperature for 20 hours, and the solvent was distilled off under reduced pressure to obtain a reactive ionic liquid represented by the following formula (20). It was.

Next, an anion fixing layer was produced. The produced reactive ionic liquid was dissolved in a mixed solution in which titanium tetraisopropoxide and acetylacetone were mixed at a molar ratio of 1: 1. Isopropyl alcohol (IPA) was added to this mixed solution, and water was added dropwise in an amount 4 times the number of moles of titanium tetraisopropoxide to conduct a hydrolysis reaction. In this way, a sol containing TiO ₂ particles on which the anion component of the reactive ionic liquid was fixed and the cation component of the reactive ionic liquid was obtained. The obtained sol was mixed with a 12 mass% solution (solvent: acetylacetone) of carboxyl group-modified hydrogenated nitrile rubber (HX-NBR, “Terban (registered trademark) XT8889” manufactured by LANXESS). The sol was mixed such that 2.4 parts by mass in terms of TiO _{2 was} added to 100 parts by mass of HX-NBR. A liquid elastomer composition was prepared by adding 5 parts by mass of a tetrakis (2-ethylhexyloxy) titanium acetylacetone solution (concentration 20% by mass) as a crosslinking agent to the mixed solution obtained by mixing the sol. The elastomer composition was applied on a substrate, dried, and then heated at 150 ° C. for 1 hour to obtain an anion-fixing layer. The thickness of the anion fixing layer was 10 μm.

[Cation fixed layer]
First, a reactive ionic liquid was produced. In 16.2 g of a solution of 1-methyl-3-vinylimidazolium methyl carbonate (solvent: methanol / water = 3: 2 mixture, concentration 25% by mass, 0.022 mol), equimolar benzenesulfonic acid Hydrate 3.80 (0.022 mol) was added dropwise. After stirring at room temperature for 1 hour, the solvent was distilled off under reduced pressure, followed by drying under reduced pressure for 2 hours. In this way, an ionic liquid monomer was obtained. 3.00 g (11.3 mmol) of the obtained ionic liquid monomer and 2.43 g (12.4 mmol) of 3-mercaptotrimethoxysilane were dissolved in 40 ml of methanol (super-dehydrated). After adding 15 mol% of azobisisobutyronitrile as a radical generator with respect to 3-mercaptotrimethoxysilane and performing argon bubbling for 30 minutes, the mixture was refluxed at 75 ° C. under argon for 7 hours. The solvent was distilled off under reduced pressure, washed with diethyl ether, and then dried under reduced pressure to obtain a reactive ionic liquid represented by the following formula (21).

Next, a cation fixed layer was produced. The produced reactive ionic liquid was dissolved in a mixed solution in which titanium tetraisopropoxide and acetylacetone were mixed at a molar ratio of 1: 1. IPA was added to this mixed solution, and water was added dropwise in an amount 4 times the number of moles of titanium tetraisopropoxide to conduct a hydrolysis reaction. In this way, a sol containing TiO ₂ particles to which the cation component of the reactive ionic liquid was fixed and the anion component of the reactive ionic liquid was obtained. The obtained sol was mixed with a 12% by mass solution (solvent: acetylacetone) of HX-NBR (same as above). The sol was mixed such that 2.4 parts by mass in terms of TiO _{2 was} added to 100 parts by mass of HX-NBR. A liquid elastomer composition was prepared by adding 5 parts by mass of a tetrakis (2-ethylhexyloxy) titanium acetylacetone solution (concentration 20% by mass) as a crosslinking agent to the mixed solution obtained by mixing the sol. The elastomer composition was applied on a substrate, dried, and then heated at 150 ° C. for 1 hour to obtain a cation fixed layer. The thickness of the cation fixing layer was 10 μm.

A laminate having a three-layer structure was manufactured by attaching a cation fixing layer on the surface of the dielectric layer and an anion fixing layer on the back surface, and peeling the substrate from each. An actuator was manufactured by attaching electrodes to both the front and back surfaces of the manufactured laminate. The actuators of Examples 1 and 11 including dielectric layers manufactured from the copolymers 1 and 11 are included in the transducer of the present invention. For each actuator, the dielectric breakdown strength, generated force, and displacement were measured in the same manner as in <Actuator characteristic 1>.

Table 3 above also shows the measurement results of the generated force, displacement rate, and dielectric strength of each actuator. As shown in Table 3, by laminating the ion-fixed layer on the dielectric layers produced from the copolymers 1 and 11, all of the generated force, the displacement rate, and the dielectric breakdown strength were greatly increased.

<Sensor characteristics>
A dielectric layer was manufactured using the copolymers 1 to 21, and a capacitive sensor including the dielectric layer was manufactured. First, the copolymer was dissolved in acetylacetone to prepare a polymer solution having a solid content concentration of 20% by mass. Next, 5 parts by mass of an acetone solution (concentration 20% by mass) of tetrakis (2-ethylhexyloxy) titanium as a crosslinking agent was added to 100 parts by mass of the polymer solution to prepare a mixed solution. The prepared mixed solution was applied onto a substrate, dried, and then heated at 150 ° C. for 60 minutes to produce a thin dielectric layer having a thickness of 10 μm. Separately, 10 parts by mass of carbon black was added to 100 parts by mass of the acrylic rubber polymer solution to prepare a conductive paint. The prepared conductive paint was applied onto a substrate, dried, and then heated at 150 ° C. for 60 minutes to produce a thin-film electrode having a thickness of 5 μm. The volume resistivity of the electrode is 5 Ω · cm. The manufactured electrodes were attached to both the front and back surfaces in the thickness direction of the dielectric layer to form a pair of electrodes. In this way, 15 types of sensors with different dielectric layers were manufactured. Copolymers 1 to 18 are included in the copolymer constituting the dielectric elastomer material of the present invention. The sensors of Examples 1-18 comprising a dielectric layer made from Copolymers 1-18 are included in the transducer of the present invention. In addition, a dielectric layer was also manufactured from the above-mentioned commercially available acrylic rubber, silicone rubber, and carboxyl group-containing NBR, and electrodes manufactured in the same manner were attached to both the front and back surfaces in the thickness direction of the dielectric layer to manufacture a sensor. .

For the manufactured sensor, first, the initial capacitance (when not stretched) was measured. Next, the sensor was stretched in one direction of the surface direction, and the capacitance was measured at a stretch rate of 100%. Then, the amount of change in capacitance was calculated by subtracting the initial capacitance from the capacitance at the time of extension. The capacitance was measured using an LCR meter (“E4980AL” manufactured by Keysight).

Tables 3 and 4 also show the measurement results of the capacitance and the amount of change in capacitance at the initial stage and at the extension of each sensor. As shown in Tables 3 and 4, Examples 1 to 13 and Comparative Examples 1 to 4, Examples 14 to 17 and Comparative Example 5, Examples 18 and Comparative Example 6, and the like with the same base polymer In comparison, the capacitance of the sensor of the example and the capacitance change amount were larger than those of the sensor of the comparative example. In the sensor of Example 12, the capacitance change amount was slightly smaller than that of the sensor of Comparative Example 1, but was larger than that of the sensors of Comparative Examples 2 to 4. The larger the capacitance change amount, the higher the sensitivity and the smaller displacement can be detected.

The transducer of the present invention can be widely used as an actuator, a sensor, a power generation element, etc. for converting mechanical energy and electric energy, or a speaker, a microphone, a noise canceller, etc. for converting acoustic energy and electric energy. Among them, artificial muscles used for industrial, medical, welfare robots, assist suits, etc., small pumps for cooling electronic parts and medical use, tactile function (haptics) elements by vibration, and flexible for medical instruments It is suitable as an actuator. Moreover, it is suitable as a pressure sensor that is disposed on a wearable biological information sensor, artificial skin of a robot, a mattress for medical use or nursing care, a seat of a wheelchair, or the like.

Claims (12)

1. A copolymer having a structure in which at least one of the monomer A, the monomer C having a crosslinkable functional group, and the monomer B having a polar group are randomly or alternately copolymerized,
   In the copolymer, in the structural unit comprising the monomer B, the polar group is bonded to the polymer main chain via three or more atoms linked in a straight chain.
2. The dielectric elastomer material according to claim 1, wherein the content of the polar group is 10% by mass or more and 25% by mass or less when the entire copolymer is 100% by mass.
3. 3. The dielectric elastomer material according to claim 1, wherein the content of the monomer B is 50 mol% or more and 98 mol% or less when the entire copolymer is 100 mol%.
4. The dielectric elastomer material according to any one of claims 1 to 3, wherein the atom interposed between the polar group and the polymer main chain is one or more selected from carbon, oxygen, nitrogen, and sulfur.
5. The dielectric elastomer material according to any one of claims 1 to 4, wherein the polar group is at least one selected from a cyano group, an ether group, an ester group, a fluorine group, a trifluoromethyl group, and a carbonate group.
6. The dielectric elastomer material according to any one of claims 1 to 5, wherein the copolymer has a weight average molecular weight of 10,000 to 5,000,000.
7. The dielectric elastomer material according to any one of claims 1 to 6, wherein a glass transition point of the copolymer is 0 ° C or lower.
8. The dielectric according to any one of claims 1 to 7, wherein the functional group of the monomer C is one or more selected from a hydroxy group, an amino group, a thiol group, a carboxyl group, a silanol group, an epoxy group, and a vinyl group. Elastomer material.
9. The dielectric elastomer material according to any one of claims 1 to 8, wherein the monomer A is at least one selected from a (meth) acrylate monomer, a silicone monomer, and a urethane monomer.
10. The dielectric elastomer material according to any one of claims 1 to 9, further comprising an insulating filler.
11. The dielectric elastomer material according to any one of claims 1 to 10, wherein the copolymer has a crosslinked structure.
12. A transducer comprising: a dielectric layer made of the dielectric elastomer material according to any one of claims 1 to 11; and a plurality of electrodes disposed through the dielectric layer.

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