Dielectric body for dielectric transducer, dielectric transducer, dielectric actuator, capacitive sensor, and power generation element

Abstract

This dielectric body for a dielectric transducer exhibits a stress retention rate [%] of 90% of more, which is determined from a stress F1 and a stress F2 found in a stress relaxation test, by the mathematical formula F2 / F1 × 100, the stress F1 being the stress that occurs when the dielectric body is stretched to a deformation of 20% and the stress F2 being the stress that occurs after the dielectric body is subsequently held stretched for 30 minutes. Further, the dielectric body for a dielectric transducer has, as a main component, a reactant of a telechelic polymer having, on a weight average basis, 2.0 to 3.9 reactive functional groups per molecule, and a weight average molecular weight of 2,000 or more. Provided is a dielectric body for a dielectric transducer, said body demonstrating a high output when used in a dielectric actuator or a dielectric sensor.

Description

Dielectric for dielectric transducer, dielectric transducer, dielectric actuator, capacitive sensor, and power generation element

[0001] The present invention relates to a dielectric material for a dielectric transducer, and to a dielectric transducer, a dielectric actuator, a capacitance type sensor, and a power generating element using the same.

[0002] A transducer is a device that converts one type of energy into another for various purposes, including measurement and information transmission. Known examples include actuators, sensors, and power generation elements that convert mechanical energy to electrical energy, and speakers and microphones that convert acoustic energy to electrical energy.

[0003] One form of such transducer is a dielectric transducer, which uses an easily deformable and recoverable dielectric material to convert mechanical energy and electrical energy, making it flexible and capable of achieving large displacement and high sensitivity. As a specific example of a dielectric transducer, for example, as shown in Figure 1, an actuator can be configured by arranging a pair of deformable electrodes 11a, 11b on both sides of a deformable dielectric material 10 in the thickness direction, and such a device is called a dielectric actuator.

[0004] When a voltage is applied between the electrodes of this dielectric actuator, Maxwell stress is generated, the electrostatic attraction between the electrodes increases, and the dielectric sandwiched between the electrodes is compressed in the thickness direction, resulting in a thinner dielectric. As the film thickness decreases, the dielectric expands in the direction parallel to the electrode surface.

[0005] On the other hand, when the voltage applied between the electrodes is reduced, the electrostatic attraction between the electrodes is also reduced. As a result, the compressive force on the dielectric in the thickness direction is reduced, and the film thickness increases due to the elastic restoring force of the dielectric. As the film thickness increases, the dielectric contracts in the direction parallel to the electrode surface. In this way, the actuator drives the member to be driven by expanding and contracting the dielectric.

[0006] Non-Patent Document 1 proposes the use of silicone elastomer as the dielectric material for such dielectric transducers because of its low dielectric loss, high electrical insulation, low energy loss, low elastic modulus, temperature dependency, low moisture absorption, etc. Furthermore, Patent Document 1 proposes a dielectric film containing an elastomer and dielectric particles, in order to obtain a transducer that is flexible, has a large relative dielectric constant, and has high dielectric breakdown strength even when made thin, and in which the dispersion state of the dielectric particles in the dielectric film is specified by specifying the number of dielectric particles per unit thickness, the number of dielectric particles per unit thickness that are larger than 1 / 10 of the film thickness, and the number of regions where the area ratio of particles is 30% or less. Furthermore, in Patent Document 2, in order to obtain a sensor that has little effect on the detection target during detection, high detection sensitivity, a wide dynamic range of detection, and little change due to repeated detection, the polyrotaxane composition is proposed, in which two polyrotaxane cyclic molecules are crosslinked with a crosslinking agent present between them in a dielectric, and the polyrotaxane composition has a hysteresis loss of 10% or less, an elongation at break of 200% or more, an initial Young's modulus of 5 MPa or less, and a relative dielectric constant of 8.0 or more.

[0007] Soft transducers using dielectric electroactive polymers https: / / www.dow.com / ja-jp / market / mkt-electronics / sub-elec-soft-transducers.html

[0008] JP 2015-189776 A JP 2020-055929 A

[0009] The inventors have examined the dielectrics proposed in the aforementioned Non-Patent Document 1, Patent Documents 1 and 2, and have found that when used as a dielectric for a dielectric actuator, there is a problem that the actuator displacement or stress, which corresponds to the output, is small in response to an applied electric field. Also, when used as a sensor, there is a problem that the voltage or capacitance, which corresponds to the output, is low in response to an input displacement. In view of the above, an object of the present invention is to provide a dielectric for a dielectric transducer that has high output when used in a dielectric actuator or sensor.

[0010] The present inventors have completed the following invention as a result of extensive research. That is, preferred configurations of the present invention are as follows: (1) A dielectric for a dielectric transducer, in which a stress retention rate [%] calculated by the formula F2 / F1×100 in a stress relaxation test is 90% or more, where F1 is the stress when stretched to a 20% deformation and F2 is the stress after holding that state for 30 minutes. (2) A dielectric for a dielectric transducer according to (1), which satisfies the following condition 1: Condition 1: At 25°C, the tensile hysteresis loss at a 20% deformation measured in the tensile hysteresis loss test according to JIS K7312 (1996) is less than 10%. (3) A dielectric for a dielectric transducer according to (1) or (2), which satisfies the following condition 2: Condition 2: At 25°C, the dielectric constant at a frequency of 100 Hz measured by the measurement method according to JIS C2151 (2019) is 5 or more. (4) A dielectric for a dielectric transducer according to any one of (1) to (3), which satisfies the following conditions 3 and 4. Condition 3: At 25°C, the tensile modulus as defined in JIS K7161 (2014) is less than 10 MPa. Condition 4: At 25°C, the tensile breaking strain as defined in JIS K7161 (2014) is 100% or more. (5) A dielectric for a dielectric transducer according to any one of (1) to (4), which satisfies the following conditions 5 and 6. Condition 5: At 25°C, the tensile yield strain as defined in JIS K7161 (2014) is 20% or more. Condition 6: At 25°C, the elastic limit strain is 20% or more. (6) A dielectric for a dielectric transducer according to any one of (1) to (5), which has, on a weight average, 2.0 to 3.9 reactive functional groups per molecule and is composed mainly of a reaction product of a telechelic polymer having a weight-average molecular weight of 2000 or more. (7) A dielectric for a dielectric transducer, which has, on a weight average, 2.0 to 3.9 reactive functional groups per molecule and is composed mainly of a reaction product of a telechelic polymer having, on a weight average, 2000 or more. (8) A dielectric for a dielectric transducer according to any one of (1) to (7), which contains segments of the following chemical formulas 1 to 3: R １R denotes hydrogen or a methyl group. ２ R refers to: a substituted or unsubstituted alkylene group; a substituted or unsubstituted arylene group; an alkylene group having an ether group, ester group, or amide group therein; an arylene group having an ether group, ester group, or amide group therein; an unsubstituted alkylene group having an ether group, ester group, or amide group therein; or an unsubstituted arylene group having an ether group, ester group, or amide group therein. ３ R refers to: a substituted or unsubstituted alkylene group; or a substituted or unsubstituted arylene group. ４ "n" refers to: a substituted or unsubstituted alkylene group; a substituted or unsubstituted arylene group; an alkylene group having an ether group or an ester group therein; an arylene group having an ether group or an ester group therein; an unsubstituted alkylene group having an ether group or an ester group therein; or an unsubstituted arylene group having an ether group or an ester group therein, where n is an integer of 2 or more. (9) A dielectric transducer comprising the dielectric for a dielectric transducer according to any one of (1) to (8) and an electrode formed on the dielectric. (10) A dielectric actuator comprising the dielectric for a dielectric transducer according to any one of (1) to (8) and an electrode formed on the dielectric. (11) A capacitance-type sensor comprising the dielectric for a dielectric transducer according to any one of (1) to (8) and an electrode formed on the dielectric. (12) A power generation element comprising the dielectric for a dielectric transducer according to any one of (1) to (8) and an electrode formed on the dielectric.

[0011] When used in a dielectric actuator or a dielectric sensor, a dielectric for a dielectric transducer having excellent output can be provided.

[0012] 5 is a schematic cross-sectional view showing an example of an actuator in a state where no voltage is applied; FIG. 6 is a schematic cross-sectional view showing an example of an actuator in a state where a voltage is applied; FIG. 7 is a top view showing an example of a capacitance type sensor; FIG. 8 is a cross-sectional view taken along II-II in FIG. 3; FIG. 9 is a front side front view showing an example of an actuator attached to a measuring device; and FIG. 10 is a cross-sectional view taken along II-II in FIG.

[0013] The inventors have found that an effective way to solve the above-mentioned problems is to set the stress retention rate of a dielectric after a certain time has elapsed within a specific range. Regarding the reason why the stress retention rate after a certain time has elapsed affects the output of a dielectric transducer, it is thought that the elastic modulus of the dielectric, which is the focus of the conventional technology, is a physical property value based on the stress generated in an extremely small deformation region, whereas the dielectric for a dielectric transducer is affected by the mechanical properties in a large strain region, and therefore the influence of a more static relaxation phenomenon appears.

[0014] The inventors checked the prior art and found that Non-Patent Document 1 uses a silicone elastomer as the dielectric, but it has a low dielectric constant and, because it is a compound with functional groups on the side chains of the polymer, it has free chains (dangling chains) at the ends of the polymer chains. As a result, the stress retention rate is low and, when compared at the same applied voltage, the output is low.

[0015] Furthermore, the technology of Patent Document 1 increases the dielectric constant and dielectric breakdown strength by dispersing dielectric particles in a specific state in the elastomer, but because it contains a large amount of dielectric particles, the aggregation state between the particles changes gradually during static deformation, which is thought to have significantly reduced the stress retention rate and resulted in low output. Furthermore, the technology of Patent Document 2 uses a polyrotaxane composition, which causes the cyclic molecules of the polyrotaxane to slip during static deformation, which is thought to have significantly reduced the stress retention rate and resulted in low output.

[0016] A specific method for achieving this will be described below. It is important that the dielectric for a dielectric transducer of the present invention has a stress retention rate F2 / F1×100 [%] of 90% or more, calculated using the ratio of the stress F1 when stretched to a strain of 20% to the stress F2 after holding that state for 30 minutes, in a stress relaxation test, with 95% or more being more preferable, and 97% or more being particularly preferable. The upper limit is, in principle, 100%. The measurement method for the stress relaxation test will be described in the Examples.

[0017] By setting the stress retention rate of the dielectric within the aforementioned range, the dielectric transducer can obtain a high output. A high stress retention rate when stretched to a large strain of 20% means that the entanglement and network structure within the dielectric are deep-rooted, and that the entanglement and network structure still remains even after stretching by 20%, and that there is little variation in density within the structure. Furthermore, a high stress retention rate after holding for 30 minutes means that the deep-rooted entanglement structure is difficult to unravel even over time (i.e., even if there is thermal movement of the molecular chains), and that it is a structure that is chemically crosslinked rather than physically crosslinked.

[0018] When the dielectric of the present invention is used in a dielectric transducer, the dielectric undergoes large deformation due to stress caused by electrostatic attraction generated by application of an electric field. However, since the dielectric has a stress retention rate of 90% or more after being stretched to a strain of 20% and held for 30 minutes, the structure still retains entanglements and a network structure even after large deformation, and the degree of untangling over time is also small, so that large stress and strain can be obtained.

[0019] Similarly, when a dielectric is used in a capacitance sensor, there is little variation in the density of the entanglement or mesh structure, so there are few slowly changing components and stress relaxation loss can be suppressed, so a larger voltage can be obtained even with small deformations, thereby increasing the S / N ratio and achieving high sensitivity.

[0020] Furthermore, the tensile hysteresis loss at 20% strain of the dielectric for dielectric transducers of the present invention at 25°C as specified in JIS K7312 (1996) is preferably less than 10%, more preferably less than 8%, and particularly preferably less than 5%. The lower limit of the tensile hysteresis loss is, in principle, 0%. The method for measuring the tensile hysteresis loss is described in the Examples. By reducing the tensile hysteresis loss under the above conditions, the responsiveness and reproducibility of the dielectric transducer can be improved.

[0021] Furthermore, the dielectric constant at 100 Hz of the dielectric for the dielectric transducer of the present invention at 25°C as defined in JIS C2151 (2019) is preferably 5 or more, more preferably 8 or more, and particularly preferably 10 or more. The dielectric constant is measured at 100 Hz to avoid the effects of irreversible changes due to polarization and to take into account the frequency band in which the dielectric transducer is used. Specific methods for measuring the dielectric constant are described in the Examples. If the dielectric constant of the dielectric for the dielectric transducer under the above conditions is less than 5, the output of the dielectric transducer may be reduced. Furthermore, since responsiveness is evaluated based on the output per unit time immediately after application of an electric field, a low dielectric constant may result in reduced responsiveness.

[0022] Furthermore, the dielectric for a dielectric transducer of the present invention preferably has an elastic modulus, as defined in JIS K7312 (1996), of less than 10 MPa, more preferably less than 5 MPa, and particularly preferably less than 1 MPa. At the same time, the elongation at break (breaking elongation) as defined in JIS K7312 (1996) is preferably 100% or more. If the elastic modulus of the dielectric for a dielectric transducer is 10 MPa or more, the output of the dielectric transducer may be reduced. If the breaking elongation of the dielectric for a dielectric transducer is less than 100%, the stability of the dielectric transducer may be reduced.

[0023] Furthermore, the tensile yield strain of the dielectric for dielectric transducers of the present invention at 25°C as defined in JIS K7161 (2014) is preferably 20% or more, more preferably 50% or more. At the same time, the elastic limit strain at 25°C is preferably 20% or more, more preferably 50% or more. The elastic limit strain is the limit strain at which the strain completely disappears when the tensile stress is gently removed. The methods for measuring the tensile yield strain and elastic limit strain are described in the Examples. By increasing the tensile yield strain and elastic limit strain under the above conditions, the displacement of the dielectric transducer can be expanded.

[0024] Furthermore, the dielectric for a dielectric transducer of the present invention preferably comprises, as its main component, a reaction product of a telechelic polymer having, on a weight average, 2.0 to 3.9 reactive functional groups per molecule at its terminals. Here, a telechelic polymer refers to a polymer having a weight-average molecular weight of 1,500 or more, which has the same type of reactive functional groups capable of reacting with each other at its terminals. Preferably, the reactive functional groups capable of reacting with each other are addition-polymerizable functional groups. For example, a telechelic polymer having two reactive functional groups can be a telechelic polymer with an [a]-[b]-[a] structure. Here, [a] is the terminal portion, which is a reactive functional group, and [b] is the portion of the main chain having a flexible structure. In addition, the phrase "the dielectric is mainly composed of a telechelic polymer reactant having, on average by weight, 2.0 to 3.9 reactive functional groups per molecule at its terminal" means that the content of the telechelic polymer reactant in the dielectric is 90% by volume or more, and the content of the telechelic polymer reactant in the dielectric is preferably 95% by volume or more, and more preferably 97% by volume or more. If the content is less than 90% by volume, the stress retention rate may decrease, and the output of the transducer may decrease. In principle, the upper limit of the content of the telechelic polymer reactant is 100% by volume.

[0025] The dielectric of a dielectric transducer is required to be a polymer that is flexible and exhibits excellent rubber elasticity in terms of transducer output, responsiveness, and reproducibility. For a polymer to exhibit rubber elasticity, it is important to chemically or physically crosslink flexible polymer chains to create a three-dimensional network structure.

[0026] In general elastomers, to create a three-dimensional network structure, it is often necessary to chemically crosslink the unsaturated bonds in the middle of the polymer chain using various chemical crosslinking agents, or to physically crosslink them using physical bonds such as hydrogen bonds or π-π interactions, but in either case, the crosslinked structure is in the middle of the polymer chain, so the ends of the polymer chain become free chains (dangling chains). Because these free chain portions are not included in the three-dimensional network structure, they do not contribute to the development of rubber elasticity, and this is thought to be one of the reasons why dielectrics obtained with conventional technology have low stress retention.

[0027] In response to this, the inventors of the present invention considered that, in order to minimize stress relaxation, it is important to reduce free chains, increase the three-dimensional network structure as much as possible, and make the molecular weight between crosslinks uniform. When a telechelic polymer is reacted to form a three-dimensional crosslinked structure, the ends of the polymers react with each other, and the resulting elastomer becomes a polymer network with few free chains. Therefore, by using the reactant of the telechelic polymer as the main component of the dielectric, the proportion of a uniform network structure can be increased in the resin component that constitutes the dielectric, thereby obtaining a dielectric with high stress retention.

[0028] In the dielectric of the present invention, as described above, the number of reactive functional groups of the telechelic polymer is preferably 2.0 to 3.9 per molecule on weight average, and more preferably 2.5 to 3.4. If the number of reactive functional groups per molecule on weight average is less than 2.0, the formation of a three-dimensional network structure may be insufficient, resulting in a decrease in stress retention. If the number of reactive functional groups per molecule on weight average exceeds 3.9, the three-dimensional network structure may become too dense and difficult to move, and the proportion of rigid crosslinked portions may increase, resulting in a decrease in stress retention and a decrease in the output of the dielectric transducer. Furthermore, if the three-dimensional network structure becomes too dense and difficult to deform, the response may also be reduced.

[0029] In the examples of the present invention, the number of reactive functional groups is a value calculated from the amount charged during polymer synthesis. However, when the reactive functional group is an acryloyl group, the number can also be determined by experimentally determining the acryloyl group equivalent and multiplying it by the weight average molecular weight.

[0030] As described above, the type of reactive functional group is not particularly limited as long as it is the same type and can react with each other, but one or more types selected from an alkenyl group, an acryloyl group, and a methacryloyl group are preferred, and an acryloyl group and / or a methacryloyl group (hereinafter sometimes referred to as a "(meth)acryloyl group") are particularly preferred.

[0031] The type of telechelic polymer used in forming the dielectric is not particularly limited, and different types of telechelic polymers may be mixed, but it is preferable that the reactive end of the telechelic polymer is the same as the segment constituting the polymer in terms of reactivity and compatibility. In this case, the number of reactive functional groups is the sum of the numbers of reactive functional groups of each telechelic polymer multiplied by the mass fraction.

[0032] The weight-average molecular weight of the telechelic polymer is not particularly limited, but is preferably 2,000 or more and less than 50,000, and more preferably 8,000 or more and less than 40,000. If the weight-average molecular weight is less than 2,000, the proportion of rigid crosslinked portions increases, which can reduce the stress retention rate, reduce the output of the dielectric transducer, and increase the elastic modulus, which can reduce the responsiveness of the dielectric transducer. If the weight-average molecular weight is 50,000 or more, the viscosity becomes high, making it difficult to produce a dielectric with a uniform thickness.

[0033] In forming the dielectric, the type of telechelic polymer used is not particularly limited, and different telechelic polymers may be mixed and used. However, when mixed, it is preferable that the reactive functional groups of the telechelic polymers and the repeating units of the telechelic polymers are the same or similar in terms of reactivity and compatibility.

[0034] In forming the dielectric, compounds such as polymers or monomers that are not telechelic polymers but have the same reactive functional group, or that have different structures but have reactive functional groups, may be mixed.

[0035] When the dielectric is a reaction product of two or more telechelic polymers, the number of reactive functional groups is the sum of the numbers of reactive functional groups of each telechelic polymer multiplied by the weight fraction, i.e., the weight average value. When the dielectric is a reaction product containing a polymer or monomer other than a telechelic polymer that can react with a telechelic polymer, the number of reactive functional groups is the number of only the reactive functional groups of the telechelic polymer.

[0036] When a dielectric is a reaction product of multiple types of telechelic polymers, the weight-average molecular weight of the telechelic polymer is the sum of the weight-average molecular weights of each telechelic polymer multiplied by its weight fraction. In other words, it is a weight-average value. Also, when the dielectric is a reaction product containing a polymer or monomer that can react with a telechelic polymer other than a telechelic polymer, the weight-average molecular weight of the telechelic polymer only applies to the telechelic polymer.

[0037] Furthermore, the dielectric for the dielectric transducer of the present invention preferably contains segments of Chemical Formula 1, Chemical Formula 2, and Chemical Formula 3, that is, the reactant of the telechelic polymer preferably contains segments of Chemical Formula 1, Chemical Formula 2, and Chemical Formula 3.

[0038]

[0039]

[0040]

[0041] The segment of Chemical Formula 1 refers to a segment in which a (meth)acryloyl group is radically polymerized, suggesting that the dielectric contains a polymer formed by the radical polymerization reaction of a methacryloyl group.

[0042] R in Chemical Formula 1 １ represents hydrogen or a methyl group, and R in Chemical Formula 1 ２indicates any of the following: - A substituted or unsubstituted alkylene group - A substituted or unsubstituted arylene group - An alkylene group having an ether group, ester group, or amide group inside - An arylene group having an ether group, ester group, or amide group inside - An unsubstituted alkylene group having an ether group, ester group, or amide group inside - An unsubstituted arylene group having an ether group, ester group, or amide group inside

[0043] The segment of Chemical Formula 2 refers to a segment formed by a urethane bond. ３ indicates any of the following: a substituted or unsubstituted alkylene group; a substituted or unsubstituted arylene group. R in Chemical Formula 3 ４ indicates any of the following: - A substituted or unsubstituted alkylene group - A substituted or unsubstituted arylene group - An alkylene group having an ether group or an ester group inside - An arylene group having an ether group or an ester group inside - An unsubstituted alkylene group having an ether group or an ester group inside - An unsubstituted arylene group having an ether group or an ester group inside

[0044] From the viewpoint of recovery, Chemical Formula 3 is preferably a segment of one or more selected from polyether, polyester, and polycarbonate polyol residues. In particular, from the viewpoint of dielectric constant, a polyether segment is preferred, and it is particularly preferred to include a polyethylene glycol segment and a polypropylene glycol segment.

[0045] If a segment in which n in Chemical Formula 3 is less than 2 is contained, flexibility will decrease, and in particular, if a compound in which n is 1 is contained, recovery may decrease. From the viewpoint of dielectric constant, n in Chemical Formula 3 is preferably 4 or more. The upper limit of n in Chemical Formula 3 depends on the structure of Chemical Formula 3, and from the viewpoint of heat resistance and recovery, n is preferably selected so that the weight-average molecular weight of the segment in Chemical Formula 3 is 2,500 or less.

[0046] The telechelic polymer preferably contains a segment of Chemical Formula 4, and more preferably a segment of Chemical Formula 5, at its terminal.

[0047]

[0048] where R of the segment of formula 4 ５ denotes hydrogen or a methyl group, and R ６ indicates any of the following: - A substituted or unsubstituted alkylene group - A substituted or unsubstituted arylene group - An alkylene group having an ether group, ester group, or amide group inside - An arylene group having an ether group, ester group, or amide group inside - An unsubstituted alkylene group having an ether group, ester group, or amide group inside - An unsubstituted arylene group having an ether group, ester group, or amide group inside

[0049] Furthermore, R ７ indicates one of the following: a substituted or unsubstituted alkylene group a substituted or unsubstituted arylene group

[0050]

[0051] where R of the segment of formula 5 ８ denotes hydrogen or a methyl group, and R ９ , R １１ represents any of the following, where n is an integer of 2 or more: a substituted or unsubstituted alkylene group a substituted or unsubstituted arylene group an alkylene group having an ether group, ester group, or amide group therein an arylene group having an ether group, ester group, or amide group therein an unsubstituted alkylene group having an ether group, ester group, or amide group therein an unsubstituted arylene group having an ether group, ester group, or amide group therein

[0052] Furthermore, R of the segment of formula 5 １０ indicates one of the following: a substituted or unsubstituted alkylene group a substituted or unsubstituted arylene group

[0053] It is possible to determine by various analytical methods that the dielectric for a dielectric transducer of the present invention contains segments of Chemical Formula 1 to Chemical Formula 3, and that the reactant of the telechelic polymer contains segments of Chemical Formula 4 and Chemical Formula 5. However, a method using pyrolysis GC-MS is convenient. It can also be determined from the raw materials forming the dielectric for a dielectric transducer.

[0054] The dielectric for a dielectric transducer of the present invention may contain inorganic particles for increasing the dielectric constant or for reinforcement, in addition to the reactant of the telechelic polymer, but the content of inorganic particles is preferably less than 10% by volume of the dielectric. If the content of inorganic particles is too high, the aggregation state of the particles changes during deformation, which may reduce the stress retention rate and decrease the output of the dielectric transducer.

[0055] [Dielectric] The dielectric of the present invention is not particularly limited in the number of layers, and may be formed from one layer or two or more layers, as long as it has the above-mentioned characteristics and can form a film-like structure by itself. The composition of the dielectric of the present invention is not particularly limited, but it is preferable that the main component is a reaction product of a telechelic polymer having a weight-average molecular weight of 2,000 or more and having a weight-average number of reactive functional groups per molecule of 2.0 to 3.9.

[0056] [Method for producing dielectric for dielectric transducer] The method for producing the dielectric of the present invention is not particularly limited, but it is preferable to carry out the following steps in this order: a step of applying a coating composition containing a resin component onto a supporting substrate to form a coating layer (step 1); a step of irradiating the coating layer with active energy rays to react the telechelic polymer to form a laminate having a supporting substrate and a resin layer (step 2); and a step of peeling the supporting substrate from the laminate to obtain the dielectric (step 3).

[0057] The method for applying the coating composition onto the supporting substrate in step 1 is not particularly limited as long as it is possible to apply the coating composition onto the supporting substrate and form a uniform coating layer within the surface. However, from the viewpoint of achieving a uniform film thickness, it is preferable to use a telechelic polymer with low viscosity as the resin component of the coating composition.

[0058] The coating method on the film can be appropriately selected from dip coating, roller coating, wire bar coating, gravure coating, die coating (U.S. Pat. No. 2,681,294), etc. Here, the coating layer refers to a "liquid layer" formed by the coating process.

[0059] In step 1, the coating composition may contain a solvent, as described below, for the purpose of reducing the viscosity of the coating composition during application. In this case, a drying step for removing the solvent is required after application in step 1. The drying method is not particularly limited as long as it can remove the solvent from the coating layer formed on the support substrate, but examples of drying methods include heat transfer drying (contact with a high-heat object), convection heat transfer (hot air), radiation heat transfer (infrared rays), and others (microwaves, induction heating). Among these, in the production method of the present invention, a method using convection heat transfer or radiation heat transfer is preferred from the viewpoint of precisely achieving a uniform drying rate even in the width direction.

[0060] The crosslinking method in step 2 is not particularly limited as long as it can cause the dielectric to exhibit the mechanical properties of an elastomer. However, a method in which the coating layer is irradiated with active energy rays to cause a reaction and crosslinking of the telechelic polymer is preferred.

[0061] The crosslinking using active energy rays is preferably an electron beam (EB) and / or ultraviolet light (UV) from the viewpoint of versatility. The type of ultraviolet lamp used for irradiating ultraviolet light includes, for example, a discharge lamp type, a flash lamp type, a laser type, and an electrodeless lamp type.

[0062] The step of peeling off the support substrate in step 3 is not particularly limited as long as the dielectric alone can be extracted, but if the application requires subsequent processing such as printing or lamination, the support substrate may be left unpeeled and used as a film for subsequent processing.

[0063] [Supporting substrate] The supporting substrate used in the method for producing a dielectric of the present invention is also used to make the flexible dielectric easier to handle, and to achieve this purpose, either a thermoplastic resin or a thermosetting resin may be used, and it may be a homoresin, a copolymer, or a mixture of two or more resins. The resin constituting the supporting substrate is preferably one that has good moldability, and from this point of view, a thermoplastic resin is more preferable.

[0064] Examples of thermoplastic resins that can be suitably used for the support substrate include polyolefin resins such as polyethylene, polypropylene, polystyrene, and polymethylpentene, alicyclic polyolefin resins, polyamide resins such as nylon 6 and nylon 66, aramid resins, polyimide resins, polyester resins, polycarbonate resins, polyarylate resins, polyacetal resins, polyphenylene sulfide resins, fluororesins such as tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, and vinylidene fluoride resin, acrylic resins, methacrylic resins, polyacetal resins, polyglycolic acid resins, and polylactic acid resins.

[0065] Examples of thermosetting resins suitable for use in the support substrate include phenolic resins, epoxy resins, urea resins, melamine resins, unsaturated polyester resins, polyurethane resins, polyimide resins, and silicone resins. The thermoplastic resin is preferably a resin with sufficient stretchability and conformability. From the viewpoints of strength, heat resistance, and transparency, the thermoplastic resin is more preferably a polyester resin, polycarbonate resin, acrylic resin, or methacrylic resin.

[0066] The polyester resin suitable for use in the support substrate is a general term for polymers in which ester bonds are the main bonding chains in the main chain, and is obtained by polycondensation of an acid component, its ester, and a diol component. Specific examples include polyethylene terephthalate, polypropylene terephthalate, polyethylene-2,6-naphthalate, and polybutylene terephthalate. These may also be copolymerized with other dicarboxylic acids and their esters or diol components as the acid component or diol component. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate are particularly preferred in terms of transparency, dimensional stability, heat resistance, and the like.

[0067] The supporting substrate may also contain various additives, such as antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, organic particles, viscosity reducers, heat stabilizers, lubricants, infrared absorbers, ultraviolet absorbers, dopants for adjusting the refractive index, etc. Furthermore, the supporting substrate may have either a single-layer structure or a multilayer structure.

[0068] It is also possible to provide a functional layer such as an easy-adhesion layer, an antistatic layer, an undercoat layer, an ultraviolet absorbing layer, or a release layer on the surface of the support substrate in advance, and it is preferable that the laminate of the present invention has a release layer in order to control the peel force between the support substrate and the dielectric for an electrostatic transducer of the present invention.

[0069] Examples of support substrates provided with a release layer include silicone release type release layers such as "Cerapeel" (registered trademark) manufactured by Toray Advanced Film Co., Ltd., "Unipeel" (registered trademark) manufactured by Unitika Ltd., and "Panapeel" (registered trademark) manufactured by Panac Corporation, as well as long-chain alkyl type and fluorine type non-silicone release layers, and these products can also be used.

[0070] [Coating Composition] The "coating composition" used in the method for producing a dielectric of the present invention is not particularly limited as long as it can be applied uniformly in-plane onto the supporting substrate in step 1 and can form a dielectric exhibiting the properties of the present invention, but is preferably a coating composition containing a telechelic polymer.

[0071] The coating composition may contain solids other than the telechelic polymer, but the content of such solids is preferably less than 10% by volume based on the solids. Examples of solids other than the telechelic polymer include high-dielectric-constant inorganic particles and monomers, prepolymers, and polymer components different from the telechelic polymer, which is the main component. The method for controlling the number of functional groups and molecular weight of the telechelic polymer varies depending on the type of polymer, and is not particularly limited. However, in the case of the telechelic polymers described in the examples and comparative examples of the present invention described below, these can be controlled by appropriately selecting the number of functional groups and molecular weight of the polyol and polyisocyanate used during synthesis and then optimizing the polymerization conditions.

[0072] The method of adding inorganic particles is not particularly limited, but it is preferable to obtain a particle dispersion by adding the above-mentioned dielectric particles to a solution in which a dispersant is dissolved in a solvent, performing pre-dispersion, and then adding a medium such as zirconia beads and performing main dispersion. In addition, the surfaces of the dielectric particles may be subjected to a surface treatment in advance.

[0073] The coating composition used in the method for producing a dielectric of the present invention may contain a solvent to form a coating layer uniformly within the surface. The number of types of solvents is preferably from 1 to 20, more preferably from 1 to 10, even more preferably from 1 to 6, and particularly preferably from 1 to 4. Here, the term "solvent" refers to a substance that is liquid at room temperature and normal pressure and can be completely evaporated in the drying step described above.

[0074] [Other Components in the Coating Composition] The coating composition used in the method for producing a dielectric of the present invention preferably contains an anti-degradation agent necessary for durability, and a polymerization initiator, curing agent, and catalyst necessary for the crosslinking reaction. The anti-degradation agent is appropriately selected from antioxidants, hydrolysis inhibitors, ultraviolet absorbers, etc., depending on the composition of the resin component, the degradation mechanism, and the intended use.

[0075] Various polymerization initiators, curing agents, and catalysts can be used. The polymerization initiators, curing agents, and catalysts may be used alone, or multiple polymerization initiators, curing agents, and catalysts may be used simultaneously. Furthermore, an acidic catalyst or a thermal polymerization initiator may be used in combination. Examples of acidic catalysts include aqueous hydrochloric acid, formic acid, and acetic acid. Examples of thermal polymerization initiators include peroxides and azo compounds. Examples of photopolymerization initiators include alkylphenone compounds, sulfur-containing compounds, acylphosphine oxide compounds, and amine compounds. Examples of crosslinking catalysts that promote the urethane bond-forming reaction include dibutyltin dilaurate and dibutyltin diethylhexoate.

[0076] As the photopolymerization initiator, an alkylphenone compound is preferred from the viewpoint of curability. Specific examples of the alkylphenone compound include 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-phenyl)-1-butane, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-(4-phenyl)-1-butane, 2-benzyl-2-dimethylamino-1-(4- morpholinophenyl)-1-butane, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butane, 1-cyclohexyl-phenyl ketone, 2-methyl-1-phenylpropan-1-one, 1-[4-(2-ethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, bis(2-phenyl-2-oxoacetic acid)oxybisethylene, and polymerized versions of these materials.

[0077] Furthermore, a leveling agent, a lubricant, an antistatic agent, etc. may be added to the coating composition used to form the dielectric, so long as the effects of the present invention are not impaired. As a result, the dielectric for an electrostatic transducer of the present invention can contain a leveling agent, a lubricant, an antistatic agent, etc.

[0078] Examples of the leveling agent include acrylic copolymers, silicone-based, and fluorine-based leveling agents. Examples of the antistatic agent include metal salts such as lithium salts, sodium salts, potassium salts, rubidium salts, cesium salts, magnesium salts, and calcium salts.

[0079] [Examples of Use] The dielectric for dielectric transducers of the present invention can be widely used as a dielectric for dielectric actuators, sensors, power generation elements, etc. that convert mechanical energy to electrical energy, or for speakers, microphones, and noise cancellers that convert acoustic energy to electrical energy.

[0080] [1] Dielectric elastomer actuator An example of an embodiment of the actuator of the present invention will be described. Figures 1 and 2 show cross-sectional schematic diagrams of the actuator of this embodiment. Figure 1 shows the state when no voltage is applied, and Figure 2 shows the state when voltage is applied.

[0081] 1 and 2, the dielectric actuator 1 includes a dielectric 10, electrodes 11a and 11b, and wirings 12a and 12b. The dielectric 10 has a rectangular thin film shape. The electrode 11a is disposed so as to cover the entire upper surface of the dielectric 10. Similarly, the electrode 11b is disposed so as to cover the entire lower surface of the dielectric 10. The electrodes 11a and 11b are connected to a power source 13 via wirings 12a and 12b, respectively. The electrodes 11a and 11b preferably contain silicone oil and carbon black.

[0082] When applying a voltage, the voltage is applied between the pair of electrodes 11a and 11b. The application of the voltage reduces the thickness of the dielectric 10, causing it to expand in the direction indicated by the thick black arrow in Figure 2. This causes the actuator 1 to output a driving force in the left-right direction.

[0083] According to this embodiment, the dielectric 10 has a high stress retention rate. Furthermore, it has a small tensile hysteresis loss, a large dielectric constant, and a low elastic modulus. The electrodes 11a and 11b are also flexible and can expand and contract together with the dielectric 10. Therefore, according to the actuator 1, the amount of deformation of the dielectric 10 in response to the applied voltage is large, and therefore a large output and displacement can be obtained.

[0084] [2] Capacitance Sensor An embodiment of an example of the capacitance sensor of the present invention will be described. First, the configuration of the capacitance sensor of this embodiment will be described. FIG. 3 shows a top view of the capacitance sensor. FIG. 4 shows a cross-sectional view taken along line II of FIG. 3. As shown in FIGS. 3 and 4, the capacitance sensor 2 includes a dielectric 20, a pair of electrodes 21a, 21b, wiring 22a, 22b, and overcoat layers 23a, 23b.

[0085] The dielectric 20 is strip-shaped and extends in the vertical and horizontal directions. The electrodes 21a and 21b are square-shaped. Six electrodes 21a are formed on the upper surface of the dielectric 20. Six electrodes 21b are formed on the lower surface of the dielectric 20, facing the electrodes 21a with the dielectric 20 in between. The electrodes 21a and 21b are made by screen printing. In this way, six pairs of electrodes 21a and 21b are arranged with the dielectric 20 in between. The electrodes 21a and 21b are made of commercially available elastic metal paste. The thickness of the electrodes 21a and 21b is 10 μm each.

[0086] The wiring 22a is connected to each of the electrodes 21a formed on the upper surface of the dielectric 20. The wiring 22a is formed on the upper surface of the dielectric 20 by screen printing. Similarly, the wiring 22b is connected to each of the electrodes 21b formed on the lower surface of the dielectric 20 by screen printing. The wiring 22b connects the electrodes 21b to a connector (not shown in the figure). The wiring 22b is formed on the lower surface of the dielectric 20 by screen printing. The wirings 22a and 22b contain acrylic rubber and silver particles.

[0087] The overcoat layer 23a has a composition similar to that of the dielectric and is strip-shaped extending in the up-down and left-right directions. The overcoat layer 23a covers the upper surfaces of the dielectric 20, the electrode 21a, and the wiring 22a. Similarly, the overcoat layer 23b has a composition similar to that of the dielectric and is strip-shaped extending in the up-down and left-right directions. The overcoat layer 23b covers the lower surfaces of the dielectric 20, the electrode 21b, and the wiring 22b.

[0088] Next, the movement of the capacitance sensor 2 will be described. For example, when the capacitance sensor 2 is pressed from above, the dielectric 20, the electrode 21a, and the overcoat layer 23a are integrally bent downward. The thickness of the dielectric 20 decreases due to compression. As a result, the capacitance between the electrodes 21a and 21b increases. This change in capacitance allows deformation due to compression to be detected.

[0089] Next, the effects of the capacitance sensor 2 will be described. According to this embodiment, the dielectric 20 is flexible and has excellent stretchability. In addition, the dielectric 20 has a high relative dielectric constant. The electrodes 21a, 21b and the wiring 22a, 22b are also flexible and can stretch integrally with the dielectric 20. Therefore, the capacitance sensor 2 has good responsiveness and a high S / N ratio. In the example of the capacitance sensor 2 shown in FIGS. 3 and 4, six electrodes 21a, 21b are formed, facing each other across the dielectric 20. However, the number, size, shape, arrangement, etc. of the electrodes may be determined appropriately depending on the application.

[0090] Next, the present invention will be described based on examples, but the present invention is not necessarily limited to these. Unless otherwise specified below, "parts" means parts by mass and "%" means % by mass.

[0091] Synthesis Example 1 Synthesis of Telechelic Polymer (X-1) A four-neck flask equipped with a thermometer, a condenser, and a stirrer was charged with 87.0 parts by mass of polytetramethylene glycol (PTMG2000 manufactured by Mitsubishi Chemical Corporation, hydroxyl value 56 mg KOH / g) as Component A, 11.3 parts by mass of isophorone diisocyanate (Desmodur® I manufactured by Covestro AG, isocyanate concentration 37.5% by mass) as Component B, 0.03 parts by mass of dibutyltin laurate (Neostan® U-100 manufactured by Nitto Kasei Co., Ltd.), and 67 parts by mass of methyl isobutyl ketone (hereinafter referred to as MIBK), and the internal temperature was maintained at 60°C while nitrogen was blown in, allowing the mixture to react for 5 hours. Subsequently, 1.7 parts by mass of 2-hydroxyethyl acrylate (HEA manufactured by Osaka Organic Chemical Industry Co., Ltd.) and 0.1 parts by mass of hydroquinone monomethyl ether were added as Component C, and the mixture was reacted at the same temperature for 3 hours while blowing in air. After that, the isocyanate group content was confirmed to be 0.1% or less by the method of JIS K7301 (1995), and a telechelic polymer solution (X-1) having a weight average molecular weight of 27,000 and a functionality of 2.0 was obtained. The molecular weight of the telechelic polymer was measured using a GPC apparatus HLC-8220 (manufactured by Tosoh Corporation).

[0092] Synthesis Examples 2 to 14: Synthesis of telechelic polymers (X-2) to (X-14) Telechelic polymers (X-2) to (X-14) were obtained in the same manner as in Synthesis Example 1, except that the raw materials and amounts charged were changed as shown in the table. The polymers were purified as needed, and those with the number of functional groups shown in the table were used in the next step.

[0093]

[0094] The abbreviations in the table represent the following compounds. PTMG-2000: Polytetramethylene glycol, manufactured by Mitsubishi Chemical Corporation, product name "PTMG2000", hydroxyl value 56 mg KOH / g, number average molecular weight 2000 P-2050: Polyester polyol obtained by condensation polymerization of 3-methyl-1.5-pentanediol and sepacic acid, manufactured by Kuraray Co., Ltd., product name "Kuraray Polyol" P-2050, hydroxyl value 56 mg KOH / g, number average molecular weight 2000 GI-2000: Polybutadiene hydrogenated with hydroxyl groups at both ends, manufactured by Nippon Soda Co., Ltd., product name "NISSO" (registered trademark)-PB GI-2000, hydroxyl value 40 to 55 mg KOH / g, number average molecular weight 2000 PL-312: Polycaprolactone triol, manufactured by Daicel Corporation, product name "PLACCEL" (registered trademark) 312, hydroxyl value 136.1 mg KOH / g, number average molecular weight 1250. PL-L212AL: Polycaprolactone diol, manufactured by Daicel Corporation, product name "PLACCEL" (registered trademark) L212AL, hydroxyl value 90.2 mg KOH / g, number average molecular weight 1250. PL-208: Polycaprolactone diol, manufactured by Daicel Corporation, product name "PLACCEL" (registered trademark) 208, hydroxyl value 137.5 mg KOH / g, number average molecular weight 830. PL-205: Polycaprolactone diol, manufactured by Daicel Corporation, product name "PLACCEL" (registered trademark) 205, hydroxyl value 213.3 mg KOH / g, number average molecular weight 530. PL-410: Polycaprolactone tetraol, manufactured by Daicel Corporation, product name "Placcel" (registered trademark) 410, hydroxyl value 217.8 mg KOH / g, number average molecular weight 1030 PL-FA1: Lactone-modified acrylate, manufactured by Daicel Corporation, product name "Placcel" (registered trademark) FA1, hydroxyl value 244 mg KOH / g BL-AE200: Hydroxyl-terminated polyalkylene glycol monoacrylate, manufactured by NOF Corporation, product name "Blenmar" (registered trademark) AE200, molecular weight 270 NP-GP-400: Trifunctional polypropylene glycol, manufactured by Sanyo Chemical Industries, Ltd., product name "Newpol (registered trademark)" GP-400, number average molecular weight 420, hydroxyl value 400 mg KOH / gNP-PEG-2000: Bifunctional polyethylene glycol, manufactured by Sanyo Chemical Industries, Ltd., product name "PEG-2000", number average molecular weight 2000, hydroxyl value 56 mgKOH / g NP-PE-64: Bifunctional polyoxyethylene polyoxypropylene block polymer, manufactured by Sanyo Chemical Industries, Ltd., product name "Newpol" (registered trademark) PE-64, number average molecular weight 3100 DS-I: Isophorone diisocyanate, manufactured by Covestro AG, product name "Desmodur" (registered trademark) I, isocyanate group content 37.5% by mass DS-W: Hydrogenated MDI (4,4'-methylenebiscyclohexyl diisocyanate), manufactured by Covestro AG, product name "Desmodur" (registered trademark) W, isocyanate group content 31.8% by mass DS-XP2580: Allophanate-modified hexamethylene diisocyanate, manufactured by Covestro AG, product name "Desmodur" (registered trademark) XP2580, isocyanate group content 12% by mass DU-AE700-100: Adduct of hexamethylene diisocyanate, manufactured by Asahi Kasei Corporation, product name "Duranate" (registered trademark) AE700-100, isocyanate group content 11.9% by mass DU-TPA100: Isocyanurate of hexamethylene diisocyanate, manufactured by Asahi Kasei Corporation, product name "Duranate" (registered trademark) TPA-100, isocyanate group content 23.1% by mass HEA: 2-hydroxyethyl acrylate, manufactured by Osaka Organic Chemical Industry Ltd., product name "HEA" 4-HBA: 4-hydroxybutyl acrylate, manufactured by Osaka Organic Chemical Industry Ltd., product name "4-HBA" DBTDL: dibutyltin laurate, manufactured by Nitto Kasei Co., Ltd., product name "Neostan" (registered trademark) U-100) MEHQ: hydroquinone monomethyl ether MIBK: methyl isobutyl ketone TOL: toluene

[0095] <Preparation Example 1: Preparation of particle dispersion P1> 50 parts by mass of a mixed solvent of ethanol and toluene in a mass ratio of 25:75, 1.5 parts by mass of dispersant 1 (DISPER BYK-103, manufactured by BYK Additives & Instruments), 50 parts by mass of barium titanate particles (manufactured by Kyoritsu Material Co., Ltd., median diameter D50: 50 nm) as high dielectric constant particles, and zirconia beads were placed in a sealed container, and the container was placed in a ball mill and dispersed at 115 rpm for 100 hours to obtain particle dispersion P1, which was a barium titanate dispersion with a solids concentration of 50% by mass.

[0096] <Preparation Example 2: Preparation of Particle Dispersion P2> Particle Dispersion P2, a barium titanate dispersion with a solids concentration of 50 mass%, was obtained in the same manner as in Preparation Example 1, except that 100 parts by mass of toluene was used instead of 50 parts by mass of the mixed solvent of ethanol and toluene in a mass ratio of 25:75, and Dispersant 1 was replaced with Dispersant 2 (DISPER BYK-107, manufactured by BYK Additives & Instruments).

[0097] Example 1 Preparation of Coating Composition Y1 Coating composition Y1 was obtained by uniformly mixing 167 parts by mass of the telechelic polymer solution (X-1) obtained in Synthesis Example 1, 3.0 parts by mass of an α-hydroxyacetophenone-based photopolymerization initiator (manufactured by IGM Resins B.V., product name "Omnirad" (registered trademark) 184), 0.2 parts by mass of a non-silicone-based leveling agent (manufactured by BYK Additives & Instruments, product name "BYK-3560"), and 36.5 parts by mass of a solvent (methyl ethyl isobutyl ketone).

[0098] Examples 2 to 13 and Comparative Examples 3 to 6: Preparation of Coating Compositions Y2 to Y13 and Z3 to Z6 Coating compositions Y2 to Y13 and Z3 to Z6 were obtained in the same manner as in Preparation Example 1, except that the raw materials in Example 1 were changed to those shown in the table.

[0099] Comparative Example 1: Preparation of coating composition Z1 Coating composition Z1 was obtained by uniformly mixing 100 parts by mass of an addition reaction silicone (manufactured by Wacker Asahi Kasei Silicones Co., Ltd., product name "ELASTSIL" (registered trademark) LR3003 / 05), 0.2 parts by mass of a non-silicone leveling agent (manufactured by BYK Additives & Instruments, product name "BYK-3560"), and 100.2 parts by mass of toluene.

[0100] Comparative Example 2: Preparation of coating composition Z2 60 parts by mass of carboxylated hydrogenated acrylonitrile-butadiene rubber (manufactured by ARLANXEO, product name "Therban" (registered trademark) XT VP KA 8889) was dissolved in 60.2 parts by mass of toluene. Next, 3.0 parts by mass of alkoxy titanate (manufactured by Nippon Soda Co., Ltd., product name "TOT") as a crosslinking agent was uniformly mixed with the prepared polymer solution. Next, 40 parts by mass of the above-mentioned particle dispersion (C) was mixed in to obtain coating composition Z2.

[0101] The abbreviations shown in the table refer to the following compounds: HPNDA: Hydroxypivalic acid neopentyl glycol diacrylate, manufactured by MIWON, product name "Miramer" (registered trademark) M210, molecular weight: 312 LR3003 / 50: Addition reaction silicone, manufactured by Wacker Asahi Kasei Silicones Co., Ltd., product name "ELASTSIL" (registered trademark) LR3003 / 05 XT8889: Carboxylated hydrogenated acrylonitrile-butadiene rubber, manufactured by ARLANXEO, product name "Therban" (registered trademark) XT VP KA 8889 O184: α-hydroxyacetophenone-based photopolymerization initiator, manufactured by IGM Resins B.V. Product name "Omnirad" (registered trademark) 184 manufactured by Nippon Soda Co., Ltd. TOT: Alkoxy titanate, product name "TOT" manufactured by Nippon Soda Co., Ltd. B3560: Non-silicone leveling agent, product name "BYK-3560" manufactured by BYK Additives & Instruments MIBK: Methyl isobutyl ketone TOL: Toluene

[0102]

[0103]

[0104] [Method for producing dielectric] In producing the dielectric, the following supporting substrates were used in addition to the above-mentioned coating composition: Supporting substrate A: Product name "Cerapeel" (registered trademark) SY 50 μm, manufactured by Toray Industries, Inc. Supporting substrate B: Product name "Cerapeel" (registered trademark) MDA 38 μm, manufactured by Toray Industries, Inc.

[0105] <Preparation of Dielectric of Example 1> The dielectric of Example 1 was prepared according to the following steps 1 to 3.

[0106] In step 1, using a continuous coating device with a slot die coater, the aforementioned coating composition Y1 was applied to the surface of the support substrate A having the release layer by adjusting the discharge flow rate of the coating composition and the conveying speed of the substrate so that the resin layer would have a specified film thickness. The coating layer was then dried under the following conditions to remove the solvent, and the support substrate B was laminated. The conveying direction of the support substrate A at this time was the MD direction of the dielectric, and the perpendicular direction was the CD direction. Air temperature: Temperature: 90°C Air speed: Coated side: 2 m / s, non-coated side: 2 m / s Air direction: Coated side: parallel to the surface of the substrate, non-coated side: perpendicular to the surface of the substrate Residence time: 2 minutes

[0107] In step 2, the coating layer was irradiated with active energy rays under the following conditions to crosslink it and form a resin layer, thereby obtaining a laminate: Irradiation light source: high-pressure mercury lamp Irradiation output: 400 W / cm ２ Accumulated light intensity: 120 mJ / cm ２

[0108] In step 3, the supporting substrate A and the supporting substrate B were peeled off from the laminate to obtain a dielectric.

[0109] <Preparation of Dielectrics of Examples 2 to 13 and Comparative Examples 3 to 6> Dielectrics were obtained by carrying out the above-mentioned steps 1 to 3 in the same manner as in the method for producing the dielectric of Example 1, except that coating composition Y1 was replaced with coating compositions Y2 to Y13 and Z3 to Z6.

[0110] <Preparation of dielectric of comparative example 1> The dielectric of comparative example 1 was obtained by changing the conditions of step 1 in Example 1 as follows, and by carrying out step 3 without carrying out step 2. Air temperature: 120°C Air speed: coated side: 2 m / sec, non-coated side: 2 m / sec Air direction: coated side: parallel to the surface of the substrate, non-coated side: perpendicular to the surface of the substrate Residence time: 2 minutes

[0111] <Preparation of Dielectric of Comparative Example 2> In Comparative Example 2, the conditions of step 1 were changed as follows, and step 2 was not carried out, but step 3 was carried out to obtain a dielectric.

[0112] In step 1, the aforementioned coating composition A was applied to the release layer-bearing surface of the support substrate A using a continuous coating device with a slot die coater, adjusting the discharge flow rate and the substrate conveying speed so that the thickness of the resin layer after crosslinking would be the specified film thickness, to form a coating layer. The coating layer was then dried under the following conditions to remove the solvent. Air temperature: 140°C Air speed: coated side: 2 m / sec, non-coated side: 2 m / sec Air direction: coated side: parallel to the surface of the substrate, non-coated side: perpendicular to the surface of the substrate Residence time: 2 minutes

[0113] Furthermore, the coated and dried film was cut out, fixed on a glass plate, and heated in a hot air oven at 150° C. for 1 hour to cause crosslinking.

[0114] [Physical Properties of Dielectrics] The following physical properties of the dielectrics were evaluated, and the results are shown in Table 1. Unless otherwise specified, in each example and comparative example, measurements were taken three times at different locations for one sample.

[0115] [Thickness] The thickness of the dielectric was measured by observing the cross section using an electron microscope (SEM). The thickness of each layer was measured according to the following method. The thickness was read from an image of a cross-sectional slice of the dielectric taken with an SEM at 3000x magnification using software (image processing software ImageJ). The layer thickness was measured at a total of 30 points, and the average value was used as the measured value.

[0116] [Stress retention rate] The dielectric was cut into a rectangular specimen measuring 30 mm wide x 120 mm long. Using a tensile tester (manufactured by Orientec, product name "Tensilon" (registered trademark) UCT-100), the initial tensile chuck distance was set to 30 mm, and the tensile speed was set to 60 mm / min (strain rate 0.033 s －１ ) and a tensile test was carried out in an environment at a temperature of 25°C.

[0117] During this test, the test piece was stretched to a strain of 6 mm (20% deformation) and held in this state for 30 minutes. From the start of stretching, the stress was recorded every 0.1 seconds while the 20% deformation was held for 30 minutes. This test method was designated as a stress relaxation test. From these results, the stress when the 20% deformation was reached from the start of stretching was designated as F1, and the stress when the 20% deformation was held for 30 minutes was designated as F2, and the stress retention rate F2 / F1 x 100 (%) was calculated.

[0118] [Tensile hysteresis loss] The tensile hysteresis loss of a dielectric was measured by processing a dielectric into a rectangular test piece of 25 mm width x 120 mm length with the MD direction of the dielectric as the major axis, and peeling off the support substrate to obtain a dielectric test piece. The thickness of the test piece was measured, and a tensile test was performed using a tensile tester (manufactured by Orientec, product name "Tensilon" (registered trademark) UCT-100) with an initial tensile chuck distance of 30 mm, at a speed of 300 mm / min and a measurement temperature of 25°C.

[0119] In this case, the dielectric was stretched to a strain of 6 mm (amount of deformation 20%) and then restored at the same speed to a strain of 0 mm (amount of deformation 0%). This process was repeated 10 times, and the stress from the start of stretching through the deformation of 20% to the restoration to the deformation of 0% was measured at intervals of 0.01 seconds, and stress-strain curves for 10 round trips were obtained.

[0120] The tensile hysteresis loss was calculated using the method of calculation from the stress-strain curve described in JIS K7312 (1996), Section 11. Hysteresis loss test, Section 11.2.4 Calculation, by calculating the hysteresis loss for the stress-strain curves from the first to tenth cycles, and the average value was taken as the tensile hysteresis loss.

[0121] [Dielectric Constant of Dielectric] The dielectric constant of the dielectric was measured based on Method A described in JIS C2151 (2019). Specifically, the dielectric was dried under high vacuum at 60°C for 12 hours, one side was masked to match the shape of the electrode, a gold electrode was formed on the surface by sputtering, and this film was placed on a sample holder (Solartron, Model 12962A). Measurements were performed using a dielectric constant measurement interface (Solartron, Model 1296) and a frequency response analyzer (Solartron, Model 1255B) in combination, from 20 Hz to 10 kHz, and the value at 100 kHz was taken as the dielectric constant of the dielectric.

[0122] [Tensile Modulus of Elasticity (Elastic Modulus), Tensile Strain at Break (Elongation at Break), and Tensile Yield Strain of Dielectric] The tensile modulus of elasticity (Elastic Modulus), tensile strain at break (Elongation at Break), and tensile yield strain of a dielectric at 25°C as specified in JIS K7161 (2014) were measured by punching the aforementioned dielectric into a dumbbell-shaped test piece (ASTM D638 TYPE V, gripper distance L: 25.4 mm) with the MD direction as the major axis to prepare a dielectric test piece. The thickness of the test piece was measured, and the dielectric test piece was placed in a tensile tester (manufactured by Orientec, product name "Tensilon" UCT-100) under conditions based on JIS K7161 (2014), and a tensile test was performed at a test speed of 10 mm / min and a measurement temperature of 25°C.

[0123] At that time, the stress-strain curve was recorded, and the stress-strain curves for deformations of 1% to 5% were linearly approximated, and the average value of the slope was taken as the tensile modulus. The strain at the breaking point was taken as the tensile breaking strain (breaking elongation) of the dielectric. The tensile yield strain was determined as the tensile strain corresponding to the first point (yield point) in the stress-strain curve where an increase in strain occurs without an increase in stress. Furthermore, the tensile yield strain was taken as infinite for specimens without a yield point.

[0124] [Elastic limit strain of dielectric] In measuring the elastic limit strain of a dielectric, a rectangular test piece of 25 mm wide x 120 mm long was processed with the MD direction of the dielectric as the major axis, and the support substrate was peeled off to obtain a dielectric test piece. The thickness of the test piece was measured, and the dielectric test piece was placed in a tensile tester (manufactured by Orientec, product name "Tensilon" (registered trademark) UCT-100) with an initial tensile chuck distance of 20 mm, and a tensile test was performed at a speed of 300 mm / min and a measurement temperature of 25°C.

[0125] In this case, the dielectric was stretched to a strain of 4 mm (amount of deformation 20%), and then restored at the same speed to a strain of 0 mm (amount of deformation 0%). This process was repeated 10 times, and the stress from the start of stretching through a deformation of 20% to restoration to a deformation of 0% was measured at intervals of 0.01 seconds, and a stress-strain curve for 10 round trips was obtained. From this curve, the strain S [mm] at which the stress becomes 0 in the restoration process of each process was determined, and the elastic restoration rate z was calculated from the following formula: １ The elastic recovery rate z [%] was calculated and the average value of the 10 times was calculated. １ =(1-(S / 20))×100[%]

[0126] If the average value of these 10 cycles exceeded 95%, the elastic limit strain was determined to be 20% or more.

[0127] Similarly, the dielectric was stretched to a strain of 10 mm (amount of deformation 50%) and then restored to a strain of 0 mm (amount of deformation 0%) at the same speed. This process was repeated 10 times, and the stress from the start of stretching through a deformation of 50% to restoration to a deformation of 0% was measured at intervals of 0.01 seconds, and a stress-strain curve for 10 round trips was obtained. From this curve, the strain S at which the stress becomes 0 in the restoration process of each process was determined. ２ [mm], and use the following formula to calculate the elastic recovery rate z ２ The elastic recovery rate z [%] was calculated and the average value of the 10 times was calculated. ２ = (1-(S ２ / 20)) x 100 [%]

[0128] If the average value of these 10 cycles exceeded 95%, the elastic limit strain was determined to be 50% or more.

[0129] [Composition of Dielectrics] For the dielectrics of Examples 1 to 13 and Comparative Examples 1 to 6, the table shows (1) whether or not a telechelic polymer reactant is contained, (2) the number of reactive functional groups in the telechelic polymer, (3) the volume content of the telechelic polymer reactant, and (4) the weight-average molecular weight of the telechelic polymer, and the presence or absence of segments of Chemical Formulas 1 to 3. The presence or absence of segments of (1) to (3) and Chemical Formulas 1 to 3, and the number of reactive functional groups were calculated from each raw material and its blending amount.

[0130] Comparative Example 1 is an addition reaction silicone material that proceeds through an addition reaction between a polymer having multiple vinylsilyl groups in the side chains and a crosslinker having hydrosilyl groups, and therefore does not qualify as a telechelic polymer. Furthermore, the polymer network structure is non-uniform, resulting in a low stress retention rate.

[0131] Comparative Example 2 is a type of acrylonitrile butadiene rubber (NBR), in which the double bonds of the polybutadiene in the main chain form a crosslinked structure via the organic titanate crosslinking agent. Therefore, it does not qualify as a telechelic polymer. Furthermore, no crosslinks are formed at the ends, and many components that do not form a network structure are included, resulting in a low stress retention rate.

[0132] [Dielectric Actuator Characteristics of Dielectrics] The characteristics of the dielectrics of Examples 1 to 13 and Comparative Examples 1 to 6 used in dielectric actuators were evaluated and compared in terms of actuator output, responsiveness, reproducibility, and breakdown voltage. The measurement methods are shown below.

[0133] The output of the dielectric actuator was measured by forming expandable electrodes on both sides of the dielectric and measuring the stress before and after applying an electric field to the electrodes, and this was used as the output of the actuator. The measuring device and method will now be described.

[0134] Figure 5 shows a front view of the dielectric actuator attached to the measuring device, and Figure 6 shows a cross-sectional view taken along line II-II of Figure 5. As shown in Figures 5 and 6, the upper end of the dielectric actuator 4 is held by an upper chuck 42 of the measuring device. The lower end of the dielectric actuator 4 is held by a lower chuck 43. The dielectric actuator 4 is attached between the upper chuck 42 and the lower chuck 43 in a state in which it has been stretched in the vertical direction beforehand. To stabilize the attitude of the dielectric, a strain of 20% (hereinafter referred to as initial strain) is applied beforehand. A load cell (not shown in the figure) is placed above the upper chuck 42.

[0135] The dielectric actuator 4 comprises a dielectric 40 and a pair of electrodes 41a and 41b. In its natural state, the dielectric 40 is a rectangular thin film measuring 50 mm in length and 25 mm in width. The electrodes 41a and 41b are arranged facing each other across the dielectric 40. In their natural state, the electrodes 41a and 41b are each a rectangular thin film measuring 40 mm in length and 20 mm in width and 50 μm in thickness. The electrodes 41a and 41b are arranged with a vertical offset of 10 mm. In other words, the electrodes 41a and 41b overlap each other by a distance of 30 mm in length and 20 mm in width, separated by the dielectric 40. A wiring (not shown) is connected to the lower end of the electrode 41a. Similarly, a wiring (not shown) is connected to the upper end of the electrode 41b. The electrodes 41a and 41b are connected to a high-voltage power supply (not shown) via their respective wiring.

[0136] When a voltage is applied between the electrodes 41a and 41b, an electrostatic attraction is generated between the electrodes 41a and 41b, compressing the dielectric 40. This reduces the thickness of the dielectric 40, generating a force in the stretching direction (vertical direction), and the tension in the vertical direction decreases accordingly.

[0137] This decrease in tension becomes the output of the actuator, and the amount of change before and after voltage application is measured using a load cell. The value obtained by dividing this by the width and thickness of the sample before measurement is taken as the generated stress [MPa].

[0138] In addition, because films with different stress relaxation rates were used in both measurements, the stress due to the initial strain was relaxed before evaluation. After the initial strain was applied, the electric field was applied once the stress change was within 3% in 5 minutes, and the value of the generated stress was taken as the value 5 seconds after the application of the electric field.

[0139] The stress was measured by increasing the applied voltage stepwise until the dielectric 40 was broken. The representative value of the actuator output of the dielectric was the stress generated at an applied voltage of 2 kV, and a value of 0.010 MPa or more was considered acceptable.

[0140] The responsiveness of the dielectric actuator was measured using the gradient [MPa / s] of the stress generated when an electric field of 2 kV was applied. The reproducibility was measured using the deviation [%] when the application of 2 kV was repeated three times.

[0141] The dielectric breakdown strength was determined by dividing the voltage value at which the dielectric was broken by the film thickness of the dielectric 40 in its natural state, and a value of 0.08 kV / μm or more was considered acceptable.

[0142] The evaluation results of Examples 1 to 13 and Comparative Examples 1 to 6 are summarized in the table.

[0143] [Sensor characteristics of dielectrics] When the dielectrics of Examples 1 to 13 and Comparative Examples 1 to 6 were used in sensors, the change in capacitance before and after deformation, responsiveness, and reproducibility were evaluated. The change in capacitance before and after deformation was measured using the same device as in the evaluation of the dielectric actuator characteristics described above. Specifically, the dielectric actuator 4 in FIG. 5 was considered a capacitance sensor, and an LCR meter (manufactured by Keysight, product name "E4980AL") was connected to the electrodes 41 a and 41 b instead of connecting a high-voltage power supply, and the capacitance was measured when the sensor was subjected to extension and deformation.

[0144] The capacitance change [nF] was calculated by first measuring the initial (unstretched) capacitance, then stretching the sensor by 50% on the upper chuck 42 (see Figure 5) to determine the capacitance, and then subtracting the initial capacitance from the measured capacitance. The responsiveness was measured using the slope [nF / ms] of the capacitance change during stretching and deformation, and the reproducibility was measured using the deviation [%] when the deformation was repeated three times. The table below shows the measurement results for the capacitance change, responsiveness, and reproducibility of each sensor.

[0145]

[0146]

[0147] The dielectric for dielectric transducers of the present invention can be widely used as a dielectric for dielectric actuators, sensors, power generation elements, etc. that convert mechanical energy to electrical energy, or for speakers, microphones, and noise cancellers that convert acoustic energy to electrical energy.

[0148] 1: Dielectric actuator 10: Dielectric 11a, 11b: Electrodes 12a, 12b: Wiring 13: Power supply 2: Capacitive sensor 20: Dielectric 21a, 21b: Electrodes 22a, 22b: Wiring 23a, 23b: Overcoat layer 4: Dielectric actuator 40: Dielectric 41a, 41b: Electrodes 42: Upper chuck 43: Lower chuck

Claims

1. A dielectric for dielectric transducers that has a stress retention rate [%] of 90% or more, calculated by the formula F2 / F1 x 100, where F1 is the stress when stretched to a deformation of 20% and F2 is the stress after maintaining that state for 30 minutes, in a stress relaxation test.

2. The dielectric for a dielectric transducer according to claim 1, which satisfies the following condition 1: Condition 1: At 25°C, the tensile hysteresis loss at 100% deformation determined by the tensile hysteresis loss test according to JIS K7312 (1996) is less than 10%.

3. The dielectric for a dielectric transducer according to claim 1, which satisfies the following condition 2: Condition 2: The relative dielectric constant at 25°C and a frequency of 100 Hz, as determined by the measurement method specified in JIS C2151 (2019), is 5 or more.

4. The dielectric for a dielectric transducer according to claim 1, which satisfies the following conditions 3 and 4: Condition 3: The tensile modulus as specified in JIS K7161 (2014) at 25°C is less than 10 MPa. Condition 4: The tensile breaking strain as specified in JIS K7161 (2014) at 25°C is 100% or more.

5. The dielectric for a dielectric transducer according to claim 1, which satisfies the following conditions 5 and 6. Condition 5: At 25°C, the tensile yield strain defined in JIS K7161 (2014) is 20% or more. Condition 6: At 25°C, the elastic limit strain is 20% or more.

6. A dielectric for a dielectric transducer according to claim 1, which is mainly composed of a reaction product of a telechelic polymer having a weight average molecular weight of 2,000 or more and having a weight average of 2.0 to 3.9 reactive functional groups per molecule.

7. A dielectric for a dielectric transducer, the main component of which is a reaction product of a telechelic polymer having a weight average molecular weight of 2,000 or more and having a weight average of 2.0 to 3.9 reactive functional groups per molecule.

8. A dielectric for a dielectric transducer according to claim 1 or 7, comprising segments of the following chemical formulas 1 to 3: R １ R denotes a hydrogen or methyl group. ２ R refers to: a substituted or unsubstituted alkylene group; a substituted or unsubstituted arylene group; an alkylene group having an ether group, ester group, or amide group therein; an arylene group having an ether group, ester group, or amide group therein; an unsubstituted alkylene group having an ether group, ester group, or amide group therein; or an unsubstituted arylene group having an ether group, ester group, or amide group therein. ３ R refers to: a substituted or unsubstituted alkylene group; or a substituted or unsubstituted arylene group. ４ refers to: a substituted or unsubstituted alkylene group; a substituted or unsubstituted arylene group; an alkylene group having an ether group or an ester group therein; an arylene group having an ether group or an ester group therein; an unsubstituted alkylene group having an ether group or an ester group therein; or an unsubstituted arylene group having an ether group or an ester group therein, and n is an integer of 2 or more.

9. A dielectric transducer comprising the dielectric for a dielectric transducer according to any one of claims 1 to 7 and an electrode formed on said dielectric.

10. A dielectric actuator comprising a dielectric for a dielectric transducer according to any one of claims 1 to 7 and electrodes formed on the dielectric.

11. A capacitive sensor comprising a dielectric for a dielectric transducer according to any one of claims 1 to 7 and an electrode formed on said dielectric.

12. A power generating element comprising the dielectric for a dielectric transducer according to any one of claims 1 to 7 and electrodes formed on the dielectric.

Images