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JP2015187931

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DESCRIPTION JP2015187931
Abstract: PROBLEM TO BE SOLVED: To provide a flexible dielectric film having high relative
dielectric constant and dielectric breakdown strength, and a method of manufacturing the same.
A dielectric film includes an elastomer and nanoparticles dispersed in the elastomer in a state of
being chemically bonded to the elastomer, the nanoparticle having a cyano group and using an
organometallic compound. It is manufactured by a sol-gel method. The method of manufacturing
a dielectric film includes a chelating step of forming a chelate of an organometallic compound,
and adding a silane coupling agent having a cyano group, an organic solvent, and water to the
chelate to obtain metal oxidation having a cyano group. Of the sol production process for
obtaining the sol of the particles, the sol of the metal oxide particles having cyano group, and the
polymer solution containing the rubber polymer having the functional group capable of reacting
with the hydroxyl group to prepare a mixed liquid And a film forming step of applying the liquid
mixture on a substrate and curing the coating film. [Selected figure] None
Dielectric film, method of manufacturing the same, and transducer using the same
[0001]
The present invention relates to a transducer using an elastomeric material, and more
particularly to a dielectric film used in the transducer and a method of manufacturing the same.
[0002]
As the transducer, an actuator that converts mechanical energy and electrical energy, a sensor, a
power generation element, or a speaker that converts acoustic energy to electrical energy, a
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microphone, and the like are known.
Polymeric materials such as dielectric elastomers are useful for constructing a flexible, compact
and lightweight transducer. For example, a transducer can be configured by arranging a pair of
electrodes on both sides in the thickness direction of a dielectric film made of dielectric
elastomer.
[0003]
In order to increase the amount of force and displacement output from the transducer, it is
necessary to increase the electrostatic attraction with respect to the applied voltage or to
increase the dielectric breakdown strength of the dielectric film so that a large voltage can be
applied. For this reason, various attempts have been made to increase the relative permittivity
and volume resistivity of the dielectric film (see, for example, Patent Documents 1 to 5).
[0004]
International Publication No. 2013/047311 Japanese Patent Application Publication No. 2009173691 Japanese Patent Application Publication No. 2007-153961 Japanese Patent Application
Publication No. 2011-72112 Japanese Patent Application Publication No. 2008-199784
[0005]
Patent Document 1 discloses a dielectric film in which metal oxide nanoparticles are dispersed in
an elastomer.
In the dielectric film, the flow of electrons is blocked by the metal oxide nanoparticles, so the
dielectric breakdown strength of the dielectric film is improved. However, the dielectric constant
of the dielectric film is not large. In order to enable low voltage drive and further improve the
performance of the transducer, it is required to increase the dielectric constant of the dielectric
film.
[0006]
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2
In this regard, Patent Documents 2 and 3 disclose a dielectric film in which dielectric particles
having a large relative dielectric constant are dispersed in an elastomer. However, dielectric
particles are easily aggregated because of their high crystallinity. For this reason, it is difficult to
uniformly disperse the dielectric particles in the elastomer. When the dielectric particles are
agglomerated, the agglomerates become the starting point and the dielectric breakdown is
caused. Patent Documents 2 and 3 disclose that particles subjected to silane coupling treatment
are used as dielectric particles. The silane coupling treatment is intended to improve the
compatibility of the dielectric particles with the elastomer and to integrate the dielectric particles
into the elastomer. That is, in the dielectric films described in Patent Documents 2 and 3, since
particles having originally large relative dielectric constants are blended, the relative dielectric
constants of the particles are not increased by the silane coupling process.
[0007]
Further, Patent Document 4 discloses a dielectric film in which a polar compound such as diallyl
dicarbonate is grafted to a polymer chain of an elastomer. Diallyl dicarbonate has an ether
linkage. For this reason, there is a possibility that the electric resistance of the dielectric film may
be lowered due to ionization by the moisture which has entered the dielectric film. Patent
Document 5 describes that by directly introducing a polar group such as a cyano group to the
side chain of the polymer, the orientation of the dielectric film can be improved and the relative
dielectric constant can be increased. However, it is difficult to introduce polar groups directly
into the polymer. In addition, when the content of the polar group in the polymer reaches a
certain level or more, the crystallinity increases and the glass transition temperature (Tg)
increases. As a result, the dielectric constant of the dielectric film is reduced, and the flexibility is
reduced.
[0008]
The present invention has been made in view of such circumstances, and it is an object of the
present invention to provide a flexible dielectric film having a large dielectric constant and a high
dielectric breakdown strength. Another object of the present invention is to provide a method of
manufacturing the dielectric film. Another object of the present invention is to provide a
transducer which is excellent in resistance to dielectric breakdown and can output a large force.
[0009]
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(1) The dielectric film of the present invention comprises an elastomer and nanoparticles
dispersed in the elastomer in a state of being chemically bonded to the elastomer, the
nanoparticles having a cyano group, and containing an organometallic compound It is
characterized in that it is produced by the sol-gel method used.
[0010]
The nanoparticles are produced by a sol-gel method using an organometallic compound.
That is, the nanoparticles are mainly composed of metal oxide particles formed by hydrolysis and
polycondensation of the organic metal compound. The nanoparticles have a cyano group (-CN).
The cyano group is disposed on either or both of the surface and the inside of the metal oxide
particle. Due to the large polarity of cyano groups, the relative dielectric constant of the
nanoparticles is large compared to the relative dielectric constant of metal oxide particles
produced solely by the sol-gel method. By including the nanoparticles having a large relative
dielectric constant, the relative dielectric constant of the dielectric film of the present invention
becomes large.
[0011]
The nanoparticles are chemically bonded to the elastomer. For this reason, nanoparticles are
hard to aggregate. Moreover, the metal oxide particle which is the main body of a nanoparticle
has insulation. Thus, the flow of electrons is blocked by the insulating network formed by the
elastomer and the nanoparticles. Thereby, the volume resistivity of the dielectric film of the
present invention is increased.
[0012]
In the present specification, particles having a maximum length of 100 nm or less are
nanoparticles. The particle diameter of the nanoparticles can be measured, for example, by
observing the cross section of the dielectric film with a transmission electron microscope (TEM).
In addition, although the manufacturing method will be described in detail later, it is assumed
that the particle diameter of the particles (metal oxide particles having a cyano group) in the sol
in the manufacturing process of the dielectric film is equal to the particle diameter of the
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nanoparticles in the dielectric film. Presumed. Therefore, the particle size of particles in the sol
may be adopted as the particle size of nanoparticles in the dielectric film. The particle diameter
of the particles in the sol can be measured, for example, using a laser diffraction / scattering
particle diameter / particle size distribution measuring apparatus. Alternatively, the sol can be
dried and measured by observation using a scanning electron microscope (SEM).
[0013]
In the dielectric film of the present invention, a cyano group having polarity is indirectly
introduced into the elastomer via the metal oxide particles having an insulating property.
Thereby, the dielectric constant can be improved while maintaining the flexibility and the
dielectric breakdown strength of the dielectric film. According to the dielectric film of the present
invention, the electrostatic attraction with respect to the applied voltage is large because the
relative dielectric constant is large. In addition, since the volume resistivity is large, a large
amount of charge can be accumulated near the interface between the dielectric film and the
electrode. Therefore, according to the transducer provided with the dielectric film of the present
invention, large force and displacement can be obtained even when the applied voltage is small.
Moreover, the dielectric breakdown strength of the dielectric film of the present invention is
large. Therefore, a larger voltage can be applied to obtain a larger amount of force and
displacement.
[0014]
(2) The method for producing a dielectric film according to the present invention is the method
for producing a dielectric film according to the present invention, wherein a chelating agent is
added to the organometallic compound to form a chelate of the organometallic compound. And a
silane coupling agent having a cyano group, an organic solvent, and water added to the chelate
compound to hydrolyze the organometallic compound and react with the silane coupling agent to
oxidize the metal having a cyano group. Of the sol production process for obtaining the sol of the
particles, the sol of the metal oxide particles having cyano group, and the polymer solution
containing the rubber polymer having the functional group capable of reacting with the hydroxyl
group to prepare a mixed liquid The method is characterized by comprising a mixed liquid
preparing step, and a film forming step of applying the mixed liquid on a substrate and curing a
coated film to obtain a dielectric film.
[0015]
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In the production method of the present invention, a mixed solution of a sol of metal oxide
particles having a cyano group and a polymer solution containing a rubber polymer is deposited
to form the dielectric film of the present invention.
First, in the chelating step, a chelating agent is used to chelate an organic metal compound as a
raw material. The organometallic compound reacts with water to hydrolyze. By chelating the
organometallic compound in advance, the rapid reaction of the organometallic compound with
water can be suppressed in the next step, and metal oxide particles having a small particle size
can be produced without aggregation.
[0016]
Next, in the sol production process, the organic metal compound is hydrolyzed to allow the
reaction between the hydrolyzed organic metal compound and the silane coupling agent having a
cyano group to proceed. That is, metal oxidation is generated by reacting the hydroxyl group (OH) of the hydrolyzed organic metal compound and the silanol group (Si-OH) obtained by
hydrolysis of the alkoxy group of the silane coupling agent having a cyano group. The silane
coupling agent is bonded to the product particle to introduce a cyano group. Thereby, a sol of
metal oxide particles having a cyano group is produced.
[0017]
Next, in the liquid mixture preparation step, a mixture of a sol of metal oxide particles having a
cyano group and a polymer solution containing a rubber polymer is mixed to prepare a liquid
mixture. A hydroxyl group remains in the metal oxide particles in the sol. On the other hand, the
rubber polymer has a functional group capable of reacting with a hydroxyl group. Therefore, in
the next film forming step, the coating film formed from the mixed solution is cured, and the
hydroxyl group and the functional group react to chemically bond the metal oxide particle having
a cyano group and the rubber polymer. Thereby, metal oxide particles (nanoparticles) having a
cyano group are uniformly dispersed in the cured rubber polymer (elastomer). Thus, according to
the manufacturing method of the present invention, the dielectric film of the present invention
can be easily manufactured.
[0018]
(3) The transducer of the present invention is characterized by comprising the dielectric film of
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the present invention and a plurality of electrodes disposed via the dielectric film.
[0019]
The transducer of the present invention comprises the dielectric film of the present invention.
As described above, the dielectric constant of the dielectric film of the present invention is large.
For this reason, the electrostatic attraction with respect to the applied voltage is large. In
addition, the dielectric film of the present invention is flexible. Therefore, according to the
transducer of the present invention, a large amount of force and displacement can be obtained
even when the applied voltage is small. In the dielectric film of the present invention, the
dielectric breakdown strength is large. Thus, according to the transducer of the present
invention, a larger voltage can be applied to obtain a larger amount of force and displacement.
[0020]
It is a perspective view of the speaker which is one embodiment of the transducer of the present
invention. It is II-II sectional drawing of FIG. It is a front side front view of an actuator attached to
a measuring device. It is IV-IV sectional drawing of FIG. It is a graph which shows the
measurement result of the dielectric constant of a dielectric film. It is a graph which shows the
measurement result of the generated stress of an actuator.
[0021]
Hereinafter, embodiments of a dielectric film, a method of manufacturing the same, and a
transducer of the present invention will be described. The dielectric film of the present invention,
the method for producing the same, and the transducer are not limited to the following
embodiments, and modifications, improvements and the like can be made by those skilled in the
art without departing from the scope of the present invention. It can be implemented in various
forms.
[0022]
<Dielectric Film> The dielectric film of the present invention contains an elastomer and
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nanoparticles.
[0023]
[Elastomer] The elastomer is not particularly limited as long as it can be chemically bonded to the
nanoparticles and can be dissolved in the polar solvent of the component of the sol liquid in the
production process of the dielectric film.
From the viewpoint of increasing the electrostatic attraction with respect to the applied voltage,
it is desirable to use an elastomer having a large polarity, that is, a large dielectric constant.
Specifically, one having a relative dielectric constant of 2.8 or more (measurement frequency
100 Hz) is preferable. As an elastomer having a large dielectric constant, for example, nitrile
rubber (NBR), hydrogenated nitrile rubber (H-NBR), acrylic rubber, ethylene-vinyl acetate
copolymer, ethylene-vinyl acetate-acrylate copolymer, Epichlorohydrin rubber, chloroprene
rubber, chlorinated polyethylene, chlorosulfonated polyethylene, urethane rubber and the like. As
an elastomer, it can be used individually by 1 type or in mixture of 2 or more types.
[0024]
As described in the following production method, the dielectric film of the present invention is
produced using a rubber polymer having a functional group capable of reacting with the
hydroxyl group of nanoparticles. As a functional group which can react with a hydroxyl group, a
carboxyl group (-COOH), an amino group (-NH), an epoxy group etc. are mentioned. Therefore, it
is preferable to use an elastomer modified by introducing such functional groups. For example,
carboxyl group-modified nitrile rubber (X-NBR), carboxyl group-modified hydrogenated nitrile
rubber (XH-NBR) and the like are preferable. In X-NBR and XH-NBR, those having an acrylonitrile
content (an amount of bonded AN) of 33% by mass or more are desirable. The bonded AN
amount is a mass ratio of acrylonitrile when the total mass of the rubber is 100% by mass.
[0025]
[Nanoparticles] Nanoparticles are produced by a sol-gel method using an organometallic
compound, and are mainly composed of metal oxide particles. The metal oxide particles
constituting the nanoparticles desirably contain one or more elements selected from titanium,
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zirconium and silicon from the viewpoint of high insulation. For example, titanium oxide (TiO2),
zirconium dioxide (ZrO2), silica (SiO2), etc., each single oxide particle, these composite particles
(TiO2 / ZrO2, TiO2 / SiO2, etc.) are mentioned. The nanoparticles have a cyano group. The cyano
group may be disposed on either or both of the surface and the inside of the metal oxide particle.
The method of introducing a cyano group into the metal oxide particles will be described in the
method of manufacturing a dielectric film described later.
[0026]
The nanoparticles are chemically bonded to the elastomer and dispersed in the elastomer by the
reaction of their hydroxyl groups with the functional groups of the elastomer. The nanoparticles
contained in the elastomer may be one kind or two or more kinds different in kind of metal oxide.
[0027]
The content of the nanoparticles may be appropriately determined in accordance with the
amount of cyano groups contained in the nanoparticles so that desired dielectric constant and
flexibility can be realized in the dielectric film. For example, the content of the nanoparticles may
be 1 part by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the
elastomer. When the content of the nanoparticles is less than 1 part by mass, not only the
improvement effect of the relative dielectric constant is small but also the improvement effect of
the volume resistivity is small because the amount of cyano group introduced is small. 10 mass
parts or more are suitable. On the other hand, when the content of the nanoparticles exceeds 70
parts by mass, the elastic modulus of the dielectric film is increased to inhibit the flexibility.
[0028]
From the viewpoint of making the film quality of the dielectric film uniform, etc., it is desirable
that the particle diameter of the nanoparticles be smaller. For example, the median diameter of
the nanoparticles in the elastomer is desirably 10 nm or more and 50 nm or less. The median
diameter is more preferably 30 nm or less, and further preferably 20 nm or less.
[0029]
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Other Components The dielectric film of the present invention may contain other components in
addition to the elastomer and the nanoparticles. Other components include crosslinking agents,
reinforcing agents, plasticizers, antiaging agents, coloring agents and the like. For example, when
insulating inorganic particles or the like are blended as a reinforcing material, the mechanical
strength and dielectric breakdown strength of the dielectric film can be further improved.
[0030]
[Physical Properties and the Like of Dielectric Film] The thickness of the dielectric film of the
present invention is not particularly limited. When used for a transducer, it is desirable that the
thickness of the dielectric film be as small as possible from the viewpoints of downsizing, driving
with low voltage, and increasing displacement. In this case, the dielectric film may have a
thickness of 1 μm or more and 100 μm or less in consideration of the dielectric breakdown
resistance and the like. It is more preferable that the thickness be 50 μm or less, and further 10
μm or less. From the viewpoint of increasing the electrostatic attraction with respect to the
applied voltage, the dielectric constant of the dielectric film of the present invention is preferably
13 or more. Further, from the viewpoint of flexibility, the elastic modulus of the dielectric film of
the present invention is preferably 50 MPa or less. In the present specification, as the elastic
modulus, a static shear elastic modulus which is calculated by measuring a tensile force of 25%
strain in a tensile test defined in JIS K 6254: 2010 is adopted.
[0031]
<Method of Manufacturing Dielectric Film> The method of manufacturing a dielectric film of the
present invention includes a chelating step, a sol manufacturing step, a mixed liquid preparation
step, and a film forming step. Hereinafter, each process is demonstrated in order.
[0032]
[Chelating Step] In this step, a chelating agent is added to the organic metal compound to form a
chelate of the organic metal compound. In addition, when manufacturing the sol of composite
particles, such as TiO2 / ZrO2 and TiO2 / SiO2, in this process, the organometallic compound of
the raw material of one metal oxide which comprises composite particles is chelated, and the
04-05-2019
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next sol manufacture is carried out. In the process, an organic metal compound as a raw material
of another metal oxide may be added to the chelate.
[0033]
The organic metal compound may be appropriately selected from metal alkoxide compounds and
metal acylate compounds according to the type of the target metal oxide particles. Examples of
metal alkoxide compounds include tetra-n-butoxytitanium, tetra-n-butoxyzirconium, tetra-nbutoxysilane, tetraisopropoxytitanium, tetraethoxysilane, tetrakis (2-ethylhexyloxy) titanium,
titanium butoxide dimer, etc. It can be mentioned. In addition, examples of the metal acylate
compound include polyhydroxytitanium stearate and zirconium tributoxy monostearate.
[0034]
As the chelating agent, for example, β-diketones such as acetylacetone, benzoylacetone and
dibenzoylmethane, β-keto acid esters such as ethyl acetoacetate and ethyl benzoylacetate,
triethanolamine, lactic acid, 2-ethylhexane-1,3 Diol, 1,3 hexanediol etc. can be used. The
chelating agent is preferably the same as the solvent for dissolving the rubber polymer in the
liquid mixture preparation step.
[0035]
[Sol Preparation Step] In this step, a silane coupling agent having a cyano group, an organic
solvent, and water are added to the formed chelate to hydrolyze the organometallic compound
and the silane coupling agent. The reaction is carried out to obtain a sol of metal oxide particles
having a cyano group. In this step, the hydroxyl group (-OH) of the hydrolyzed organic metal
compound is reacted with the silanol group (Si-OH) obtained by hydrolysis of the alkoxy group of
the silane coupling agent having a cyano group. A silane coupling agent having a cyano group is
bonded to the metal oxide particle. Thereby, a sol of metal oxide particles having a cyano group
is produced.
[0036]
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The silane coupling agent having a cyano group may be appropriately selected from the group of
compounds having a functional group having a cyano group at the end in consideration of the
reactivity with the organic metal compound, and the like. For example, compounds represented
by the following formulas (1) to (6) are preferable. Among them, trimethoxysilane having a short
alkoxy group is more preferable because it has good reactivity with an organic metal compound
as in the compounds represented by the formulas (1), (4) and (6). The silane coupling agent
which has a cyano group may be used individually by 1 type, and may mix and use 2 or more
types.
[0037]
In this step, it is desirable to add a silane coupling agent having a cyano group prior to water.
When water is added and then a silane coupling agent having a cyano group is added, the silane
coupling agent which does not react with the organometallic compound tends to remain.
Unreacted silane coupling agents react with one another to form particulate aggregates. When
aggregates are present in the dielectric film, they become the starting point and easily cause
dielectric breakdown.
[0038]
As the organic solvent, alcohols such as methanol, ethanol and isopropyl alcohol (IPA), ketones
such as methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK), ethers such as
tetrahydrofuran (THF) and the like may be used. For example, when IPA is added, the affinity
between the chelate and water is improved, and nuclei of metal oxide particles are easily
generated. Further, when MEK is added, the compatibility between the sol of the metal oxide
particles having a cyano group and the polymer solution can be improved in the mixed liquid
preparation step.
[0039]
In addition to the organic solvent, it is desirable to add acetic acid, formic acid or the like for the
purpose of accelerating the hydrolysis reaction of the silane coupling agent having a cyano group
and setting the pH range in which the silanol group is stable.
[0040]
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12
When adding a silane coupling agent having a cyano group, an organic solvent, and water to the
chelate compound, it may be carried out with stirring.
Moreover, it is good to continue stirring at a temperature of 40 ° C. or more and 80 ° C. or less
even after the addition. By so doing, it is possible to promote the reaction of forming the metal
oxide particles and the reaction of the metal oxide particles with the silane coupling agent having
a cyano group while leaving the hydroxyl groups of the metal oxide particles. Stirring for 1 to
several hours is sufficient. The obtained sol can be subjected to the mixed liquid preparation step
as it is. Alternatively, it may be allowed to stand at room temperature for a while and then
subjected to a mixture preparation step. For example, by heat-treating the sol at high
temperature, the crystallinity of the metal oxide particles can be enhanced and the relative
dielectric constant can be increased. However, when the sol is heated to a high temperature, the
hydroxyl groups of the metal oxide particles are reduced. For this reason, it becomes difficult to
chemically bond with the rubber polymer in a later step.
[0041]
[Mixed liquid preparation step] In this step, a mixed liquid of a sol of the produced metal oxide
particles having a cyano group and a polymer solution containing a rubber polymer having a
functional group capable of reacting with a hydroxyl group is mixed. Prepare.
[0042]
The polymer solution is prepared by dissolving a predetermined rubber polymer in a solvent.
As described above, as the solvent, it is desirable to use the same one as the chelating agent that
chelates the organic metal compound. The blending amount of the sol may be appropriately
determined in consideration of the amount of nanoparticles to be contained in the elastomer. In
addition, other components such as a crosslinking agent and insulating inorganic particles may
be blended in the liquid mixture, as necessary. In this case, the other components may be
previously blended in the polymer solution. As the crosslinking agent, an organic metal
compound is suitable. The reaction residue of the crosslinking agent becomes an impurity and
contributes to a reduction in the dielectric breakdown strength of the dielectric film. When an
organic metal compound is used, a reaction residue hardly occurs. Therefore, it is possible to
suppress a decrease in the dielectric breakdown strength of the dielectric film.
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[0043]
[Film Forming Step] In this step, the prepared mixed solution is applied onto a substrate, and the
coating is cured to obtain a dielectric film. The application method of the mixed solution is not
particularly limited. For example, in addition to printing methods such as inkjet printing,
flexographic printing, gravure printing, screen printing, pad printing and lithography, dip
method, spray method, bar coat method and the like can be mentioned. Further, the curing
temperature of the coating film may be appropriately determined in consideration of the type of
solvent used and the reaction rate. For example, it is desirable to set the boiling point or more of
the solvent.
[0044]
A hydroxyl group remains in the metal oxide particles in the sol. On the other hand, the rubber
polymer has a functional group capable of reacting with a hydroxyl group. For this reason, in this
process, while the coating film formed from a liquid mixture hardens, a hydroxyl group and a
functional group react, and the metal oxide particle which has a cyano group, and a rubber
polymer chemically bond. Thus, the dielectric film of the present invention in which the metal
oxide particles (nanoparticles) having a cyano group are uniformly dispersed in the cured rubber
polymer (elastomer) is produced.
[0045]
<Transducer> The transducer of the present invention comprises the dielectric film of the present
invention and a plurality of electrodes disposed via the dielectric film. The transducer of the
present invention may be configured by alternately laminating a plurality of dielectric films and a
plurality of electrodes. Adopting a laminated structure can generate a larger force. The
configuration and manufacturing method of the dielectric film of the present invention are as
described above. Therefore, the explanation is omitted here. Also in the transducer of the present
invention, it is desirable to adopt the preferred embodiment of the dielectric film of the present
invention.
[0046]
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In the transducer of the present invention, the material of the electrode is not particularly limited.
It is desirable that the electrode be able to expand and contract following the deformation of the
dielectric film. In this case, deformation of the dielectric film is less likely to be regulated by the
electrodes. Therefore, in the transducer of the present invention, it becomes easy to obtain the
desired output. For example, the electrode can be formed of a conductive paste or a conductive
paint in which a conductive material is mixed with a binder such as oil or elastomer. As the
conductive material, carbon materials such as carbon black, ketjen black, carbon nanotubes, and
graphene, and metal powders such as silver may be used. Alternatively, the electrodes may be
formed by knitting carbon fibers or metal fibers in a mesh shape.
[0047]
Hereinafter, an embodiment in which the transducer of the present invention is embodied in a
speaker will be described. FIG. 1 shows a perspective view of the speaker of this embodiment. In
FIG. 2, II-II sectional drawing of FIG. 1 is shown. In FIG. 1, the insulating film on the front side is
shown passing through. First, the configuration of the speaker according to the present
embodiment will be described. As shown to FIG. 1, FIG. 2, the speaker 2 is equipped with the
vibration member 20, the front side frame 30a, and the rear side frame 30b.
[0048]
The front side frame 30a and the rear side frame 30b are respectively made of resin and have a
ring shape. The front side frame 30 a and the rear side frame 30 b are disposed to face each
other with the peripheral portion of the vibrating member 20 interposed therebetween. The front
frame 30 a and the rear frame 30 b are fixed by eight bolts 31 and eight nuts 32. The set of
bolt 31 -nut 32 is arranged at predetermined intervals in the circumferential direction of the
speaker 2. The bolt 31 penetrates from the front of the front frame 30a to the rear of the rear
frame 30b. The nut 32 is screwed to the through end of the bolt 31.
[0049]
The vibrating member 20 is interposed between the front side frame 30a and the rear side frame
30b. The vibrating member 20 includes three dielectric films 21a to 21c, four electrodes 22a to
22d, and two insulating films 23a and 23b. In the vibrating member 20, the dielectric films 21a
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to 21c and the electrodes 22a to 22d are alternately stacked.
[0050]
Each of the dielectric films 21a to 21c includes a carboxyl group-modified hydrogenated nitrile
rubber and nanoparticles, and has a circular thin film shape. The nanoparticles consist of TiO 2
particles having a cyano group. The nanoparticles are manufactured by a sol-gel method using a
titanium alkoxide and a silane coupling agent having a cyano group represented by the above
chemical formula (1). The thickness of the dielectric films 21a to 21c is 20 μm. The dielectric
films 21a to 21c are included in the dielectric film of the present invention. Each of the
electrodes 22a to 22d contains silicone rubber and silver particles. The electrodes 22a to 22d
each have a circular thin film shape smaller in diameter than the dielectric films 21a to 21c. The
electrodes 22a to 22d are arranged substantially concentrically with the dielectric films 21a to
21c, respectively. The electrodes 22a to 22d respectively have terminal portions 220a to 220d.
The terminal portions 220a to 220d respectively project from the outer peripheral edge above
the electrodes 22a to 22d in the radial direction. Each of the terminal portions 220a to 220d has
a strip shape. A voltage is applied to the terminal portions 220a to 220d from the outside via a
wire (not shown). Each of the insulating films 23a and 23b is made of acrylic rubber, and is in the
form of a circular thin film having the same size as the dielectric films 21a to 21c.
[0051]
Next, a method of manufacturing the speaker 2 of the present embodiment will be described.
First, dielectric films 21a to 21c are prepared. Next, conductive paint in which silver powder is
mixed with silicone rubber is printed on the front and back surfaces of the dielectric film 21a to
form electrodes 22a and 22b. Then, an insulating paint containing acrylic rubber is printed on
the entire front surface of the formed electrode 22a and the front surface of the dielectric film
21a on which the electrode 22a is not formed, thereby forming the insulating film 23a. Similarly,
conductive paint is printed on the front and back surfaces of the dielectric film 21c to form the
electrodes 22c and 22d. Then, an insulating paint is printed on the entire rear surface of the
formed electrode 22d and the rear surface of the dielectric film 21c on which the electrode 22d
is not formed, to form an insulating film 23b. Then, the dielectric film 21a having the electrodes
22a and 22b and the insulating film 23a, the dielectric film 21b, and the dielectric film 21c
having the electrodes 22c and 22d and the insulating film 23b are stacked to fabricate the
vibrating member 20. Next, the peripheral edge portion of the manufactured laminate is held by
the front frame 30a and the rear frame 30b. In this state, the front frame 30a and the rear frame
30b are fixed by eight bolts 31 and eight nuts 32. Thus, the speaker 2 is manufactured.
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[0052]
Next, the movement of the speaker 2 of this embodiment will be described. In the initial state, a
predetermined bias voltage is applied to the electrodes 22a to 22d via a wiring (not shown). In
this state, an alternating voltage as an electrical signal of sound is applied to the electrodes 22a
to 22d. Then, due to the change in the film thickness of the dielectric films 21a to 21c, the
vibrating member 20 vibrates in the front-rear direction, as indicated by a white arrow in FIG. As
a result, the air vibrates and a sound is generated.
[0053]
Next, the operation and effects of the speaker 2 of the present embodiment will be described. In
the speaker 2 of the present embodiment, the dielectric films 21a to 21c are flexible and
excellent in stretchability. In addition, the dielectric constants of the dielectric films 21a to 21c
are large. The electrodes 22a to 22d are also flexible and can extend and contract integrally with
the dielectric films 21a to 21c. Therefore, in the speaker 2, the amount of deformation of the
vibrating member 20 with respect to the applied voltage becomes large, and the sound pressure
to be output becomes large. Also, the dielectric breakdown strength of the dielectric films 21a to
21c is large. For this reason, the speaker 2 is excellent in durability.
[0054]
The vibrating member 20 includes three dielectric films 21a to 21c stacked via the electrodes
22a to 22d. Therefore, the amount of deformation of the vibrating member 20 with respect to
the applied voltage is large, and the sound pressure to be output is large, as compared with the
configuration in which the electrodes are disposed on both surfaces of one dielectric film. In
addition, the speaker 2 is lightweight and compact and relatively inexpensive.
[0055]
Next, the present invention will be more specifically described by way of examples.
[0056]
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<Production of Silane Coupling Agent Having a Cyano Group> First, 5.3 g (0.10 mol) of
acrylonitrile and 21.57 g (0.11 mol) of 3-mercaptopropyltrimethoxysilane in 70 mL of methanol
(super dehydrated). Dissolved.
Next, to this methanol solution, diisopropylamine as an amine catalyst was added and stirred
overnight at room temperature. The addition amount of diisopropylamine was 5 mol% with
respect to 3-mercaptopropyl trimethoxysilane. Then, the solvent is removed by evaporation
under reduced pressure, methanol is added, and 20 wt / s of a silane coupling agent having a
cyano group represented by the above chemical formula (1) (hereinafter referred to as "CNcontaining coupling agent") A vol% methanol solution was prepared.
[0057]
<Production of Dielectric Film> Example 1 First, 0.02 mol of acetylacetone was added to 0.01
mol of an organic metal compound, tetraisopropoxy titanium, for chelating. Next, 0.083 mol of
isopropyl alcohol (IPA) and 32 g of a 20 wt / vol% methanol solution of a CN-containing coupling
agent were added to the obtained chelate. Subsequently, stirring is performed while adding
0.139 mol of methyl ethyl ketone (MEK), 0.03 mol of acetic acid, and 0.08 mol of water, and the
temperature is raised to 40 ° C. after the addition is completed, and stirring is further
performed for 2 hours, A sol of TiO 2 particles to which a CN-containing coupling agent was
bound was obtained. The obtained sol was allowed to stand at room temperature overnight, and
then concentrated by an evaporator to a half mass. The concentrated sol was then allowed to
stand overnight at room temperature. The sol thus produced is hereinafter referred to as
"concentrated sol". When the particle diameter of the particles contained in the concentrated sol
was measured using a laser diffraction / scattering particle diameter / particle size distribution
measuring device manufactured by Nikkiso Co., Ltd., the median diameter was 8 nm.
[0058]
Next, a carboxyl group-modified hydrogenated nitrile rubber ("Terban (registered trademark) XT
8889" manufactured by LANXESS Corporation) was dissolved in acetylacetone to prepare a
polymer solution having a polymer concentration of 12% by mass. Subsequently, a concentrated
sol and a 20 mass% acetylacetone solution of tetrakis (2-ethylhexyloxy) titanium of an organic
metal compound as a crosslinking agent were mixed with the prepared polymer solution to
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prepare a liquid mixture. The concentrated sol was blended such that the amount of TiO2 was
6.6 parts by mass and the amount of CN-containing coupling agent was 52 parts by mass with
respect to 100 parts by mass of the polymer. The crosslinking agent was blended so that the
amount of tetrakis (2-ethylhexyloxy) titanium was 5 parts by mass with respect to 100 parts by
mass of the polymer.
[0059]
Then, the prepared mixed solution was applied onto a substrate, dried, and heated at 150 ° C.
for 1 hour to produce a dielectric film having a thickness of 20 μm.
[0060]
Example 2 A dielectric film was produced in the same manner as in Example 1 except that the
addition amount of a 20 wt / vol% methanol solution of a CN-containing coupling agent to a
chelate was changed to 16 g in the production of a sol.
In this case, the concentration of TiO 2 is 6.6 parts by mass and the amount of CN-containing
coupling agent is 26 parts by mass with respect to 100 parts by mass of the polymer component
as the concentrated sol to be blended in the polymer solution.
[0061]
Example 3 A dielectric film was produced in the same manner as in Example 1 except that the
amount of the 20 wt / vol% methanol solution of the CN-containing coupling agent to the chelate
was changed to 8 g in the production of the sol. In this case, the concentration of TiO2 is 6.6
parts by mass and the amount of CN-containing coupling agent is 13 parts by mass with respect
to 100 parts by mass of the polymer component as the concentrated sol to be blended in the
polymer solution.
[0062]
Comparative Example 1 A CN-containing coupling agent alone was directly incorporated into a
polymer solution to produce a dielectric film. First, a polymer solution of the same carboxyl
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group-modified hydrogenated nitrile rubber as used in Example 1, a 20 wt / vol% methanol
solution of a CN-containing coupling agent, and tetrakis (2-ethylhexyloxy) titanium as a
crosslinking agent The 20 mass% acetylacetone solution was mixed, and the liquid mixture was
prepared. The 20 wt / vol% methanol solution of the CN-containing coupling agent was blended
such that the amount of the CN-containing coupling agent was 52 parts by mass with respect to
100 parts by mass of the polymer component. The crosslinking agent was blended so that the
amount of tetrakis (2-ethylhexyloxy) titanium was 5 parts by mass with respect to 100 parts by
mass of the polymer. Next, the prepared mixed solution was applied onto a substrate, dried, and
heated at 150 ° C. for 1 hour to produce a dielectric film having a thickness of 20 μm.
[0063]
Comparative Example 2 A sol of TiO 2 particles was produced without using a CN-containing
coupling agent, and a dielectric film was produced using the sol. First, 0.02 mol of acetylacetone
was added to 0.01 mol of organometallic compound tetraisopropoxy titanium to chelate. Next,
stir while adding IPA of 0.083 mol, MEK of 0.139 mol, and water of 0.08 mol to the obtained
chelate, and after completion of the addition, raise the temperature to 40 ° C. and stir for
additional 2 hours. Thus, a sol of TiO 2 particles was obtained. The resulting sol was allowed to
stand overnight at room temperature. The sol of TiO 2 particles thus produced is added to, and
mixed with, the same polymer solution of carboxyl group-modified hydrogenated nitrile rubber
as that used in Example 1, and further tetrakis (2-ethylhexyloxy) as a crosslinking agent A 20
mass% acetylacetone solution of titanium was added and mixed to prepare a mixture. About the
sol of TiO2 particle ¦ grains, it mix ¦ blended so that the amount of TiO2 may be 6.6 mass parts
with respect to 100 mass parts of polymer parts. The crosslinking agent was blended so that the
amount of tetrakis (2-ethylhexyloxy) titanium was 5 parts by mass with respect to 100 parts by
mass of the polymer.
[0064]
About the kind and compounding quantity of the raw material which were used for manufacture
of the dielectric film of an Example and a comparative example, it summarizes in Table 1 of a
postscript.
[0065]
<Evaluation of dielectric film> The manufactured dielectric film was evaluated by the following
items.
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The evaluation results of the dielectric film are summarized in Table 1 below.
[0066]
[Volume Resistivity] The volume resistivity of the dielectric film was measured according to the
parallel terminal electrode method defined in JIS K6271: 2008. The measurement was performed
by applying a DC voltage of 100V.
[0067]
[Elastic Modulus] The static shear modulus of the dielectric film was calculated by measuring a
tensile force of 25% strain in a tensile test defined in JIS K 6254: 2010.
[0068]
[Dielectric Permittivity] With regard to the dielectric constant of the dielectric film, the dielectric
film is placed in the sample holder (Solatron, model 12962A), the permittivity measurement
interface (model, model 1296), and the frequency response analyzer (the company) Made in
combination with Model 1255B).
[0069]
<Evaluation of Actuator Characteristics> The manufactured dielectric film was used to
manufacture an actuator, which is a form of a transducer, and the actuator characteristics were
evaluated.
First, carbon black was mixed and dispersed in an acrylic rubber polymer solution to prepare a
conductive paint.
Next, a conductive paint was screen printed on both sides in the thickness direction of the
manufactured dielectric film to form an electrode. An actuator comprising the dielectric film of
the embodiment is included in the transducer of the present invention.
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[0070]
The generated stress was measured as a characteristic of the manufactured actuator. First, the
measuring apparatus and the measuring method will be described. FIG. 3 shows a front side front
view of an actuator attached to the measuring device. In FIG. 4, IV-IV sectional drawing of FIG. 3
is shown.
[0071]
As shown in FIGS. 3 and 4, the upper end of the actuator 5 is gripped by the upper chuck 52 in
the measuring device. 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 of being
stretched in the vertical direction in advance (stretching ratio 25%). A load cell (not shown) is
disposed above the upper chuck 52.
[0072]
The actuator 5 is composed of a dielectric film 50 and a pair of electrodes 51a and 51b. The
dielectric film 50 is in the form of a rectangular thin film having a length of 50 mm, a width of
25 mm, and a thickness of 20 μm in a natural state. The electrodes 51 a and 51 b are disposed
to face each other in the front and back direction with the dielectric film 50 interposed
therebetween. The electrodes 51a and 51b each have a rectangular thin film shape of 40 mm
long, 25 mm wide, and 10 μm thick in a natural state. The electrodes 51a and 51b are arranged
in a state of being offset by 10 mm in the vertical direction. That is, the electrodes 51 a and 51 b
overlap each other in the range of 30 mm long and 25 mm wide via the dielectric film 50. A wire
(not shown) is connected to the lower end of the electrode 51a. Similarly, a wire (not shown) is
connected to the upper end of the electrode 51b. The electrodes 51a and 51b are connected to a
power supply (not shown) via the respective wirings.
[0073]
When a voltage is applied between the electrodes 51a and 51b, an electrostatic attractive force is
generated between the electrodes 51a and 51b to compress the dielectric film 50. As a result, the
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thickness of the dielectric film 50 becomes thinner and extends in the stretching direction
(vertical direction). The stretching of the dielectric film 50 reduces the stretching force in the
vertical direction. The stretching force reduced before and after the application of voltage was
measured by the load cell and used as the generated stress. The measurement of the generated
stress was performed by gradually increasing the applied voltage until the dielectric film 50 was
broken.
[0074]
Table 1 summarizes the types and blending amounts of the raw materials used for manufacturing
the dielectric film, and the evaluation results of the dielectric film and the actuator
characteristics. Further, FIG. 5 shows the measurement results of the relative dielectric constant
of the dielectric film. FIG. 6 shows the measurement results of the generated stress of the
actuator.
[0075]
As shown in Table 1 and FIG. 5, the dielectric films of Examples 1 to 3 containing TiO 2 particles
(nanoparticles having a cyano group) produced by bonding CN-containing coupling agents
include conventional TiO 2 particles. Compared with the dielectric film of Comparative Example
2, the relative dielectric constant was increased. In addition, as the amount of CN-containing
coupling agent to be bound increases, that is, as the content of cyano groups in the dielectric film
increases, the relative dielectric constant increases. On the other hand, in the dielectric film of
Comparative Example 1, despite the incorporation of the CN-containing coupling agent, the
improvement of the relative dielectric constant was hardly observed at a practical frequency
around 50 to 100 Hz.
[0076]
As shown in FIG. 6, a large voltage could be applied to the actuators provided with the dielectric
films of Examples 1 to 3. Then, the generated stress with respect to the electric field strength is
increased in proportion to the magnitude of the relative dielectric constant of the dielectric film.
On the other hand, in the actuator provided with the dielectric film of Comparative Example 1,
the breakdown occurred at an electric field strength of 30 V / μm. This is considered to be due
to the fact that the aggregates formed by the reaction of CN-containing coupling agents become
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the origin of the dielectric breakdown.
[0077]
The transducer using the dielectric film of the present invention can be widely used as an
actuator, sensor or the like for converting between mechanical energy and electric energy, or as a
speaker, microphone, noise canceler, etc. for converting between acoustic energy and electric
energy. .
[0078]
2: Speaker (transducer), 20: vibrating member, 21a to 21c: dielectric film, 22a to 22d: electrode,
23a, 23b: insulating film, 220a to 220d: terminal portion, 30a: front frame, 30b: rear frame, 31:
Bolt, 32: Nut.
5: actuator (transducer), 50: dielectric film, 51a, 51b: electrode, 52: upper chuck, 53: lower
chuck.
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