Dielectric medium, method for manufacturing dielectric medium, and converter

Abstract

Provided is a dielectric having high dielectric properties, low hysteresis loss, and high flexibility. Provided is a dielectric comprising a polyurethane elastomer and an ionic liquid in the polyurethane elastomer wherein the polyurethane elastomer has a matrix and domains distributed in the matrix, and the domains comprise a specific polyether structure.

Description

Technical Field

[0001] The present disclosure relates to dielectrics, methods of manufacturing dielectrics, and converters. Background Art

[0002] A converter including a dielectric and at least two electrodes with a dielectric inserted therebetween is an element that converts between electrical energy and mechanical energy with high conversion efficiency using deformation (expansion and contraction) of the dielectric, and is being used in various fields. For example, when electrical energy generated by deformation of the dielectric due to an external force is obtained as an output, the converter can be used as a sensor or a power generation element. In addition, the converter can act as an actuator by generating stress in the dielectric by applying a potential difference between a pair of electrodes.

[0003] When the dielectric is used for such driving applications, sensor applications, and power generation applications, the following characteristics are important. That is, it is preferred that the dielectric has a high dielectric constant in order to increase conversion efficiency, has softness in view of the ease of deformation, and has a low hysteresis loss characteristic in order to reduce energy loss due to deformation cycles.

[0004] For example, Patent Document 1 discloses a dielectric sensor using an elastomer composition containing polyolefin polyol as a dielectric. In addition, Patent Document 2 discloses a dielectric having a high dielectric constant by mainly distributing an ionic liquid in a microphase separation structure using a block polymer and forming a high dielectric constant layer and a low dielectric constant layer on a nanometer scale according to the shape of the microphase separation structure.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2022-069960

[0008] Patent Document 2: Japanese Patent Application Publication No. 2021-034207

[0009] Non-patent literature

[0010] Non-patent literature 1: Sustainability 2021, 13(17), 9881

[0011] Non-patent document 2: LK Huang and MJJ Wang. Image thresholding by minimizing the measures of fuzziness. Pattern recognition, 28(1): 41-51, 1995.1, 2.1

[0012] Non-patent literature 3: IEEE Transactions on SYSTEMS, MAN, AND CYBERNETICS, Vol. SMC-9, No. 1, January 1979, pp. 62-66 Summary of the invention

[0013] Problem that the invention aims to solve

[0014] However, the dielectric disclosed in Patent Document 1 has flexibility, but tends to have high hysteresis loss and large energy loss due to deformation. In addition, it is difficult to achieve excellent flexibility with the block polymer comprising a styrene polymer and an acrylate polymer disclosed in Patent Document 2.

[0015] Therefore, when a dielectric is used as a converter, it is difficult to achieve all required characteristics.

[0016] At least one aspect of the present disclosure is to provide a dielectric having a high dielectric constant, low hysteresis loss, and high flexibility. In addition, at least one aspect of the present disclosure is to provide a method for manufacturing a dielectric. In addition, at least one aspect of the present disclosure is to provide a converter including a dielectric.

[0017] Solutions for solving problems

[0018] According to at least one aspect of the present disclosure, a dielectric is provided.

[0019] The dielectric comprises a polyurethane elastomer and an ionic liquid in the polyurethane elastomer;

[0020] The polyurethane elastomer comprises a matrix and domains dispersed in the matrix, and

[0021] The domain comprises a first structure represented by the following formula (1):

[0022]

[0023] In formula (1), R 1 It represents an alkylene group having 3 to 6 carbon atoms.

[0024] In addition, according to another embodiment of the present disclosure, there is provided a method for manufacturing the above-mentioned dielectric, comprising:

[0025] (i) a step of obtaining a second urethane prepolymer having at least two hydroxyl groups by reacting a first urethane prepolymer having at least one isocyanate group with a first polycarbonate polyol having at least two hydroxyl groups;

[0026] (ii) a step of obtaining a first dispersion by dispersing droplets comprising at least a portion of a second urethane prepolymer in a second polycarbonate polyol;

[0027] (iii) a step of obtaining a second dispersion by dispersing an ionic liquid in the first dispersion; and

[0028] (iv) a step of preparing a dielectric-forming mixture containing the second dispersion and a polyisocyanate having at least two isocyanate groups, and then reacting the second urethane prepolymer, the second polycarbonate polyol, and the polyisocyanate in the dielectric-forming mixture to form a dielectric.

[0029] Furthermore, according to another embodiment of the present disclosure, there is provided a converter using the above-mentioned dielectric, which includes at least two electrodes, and the above-mentioned dielectric interposed between the electrodes.

[0030] Effects of the Invention

[0031] According to at least one aspect of the present disclosure, a dielectric having excellent dielectric properties, low hysteresis loss, and high flexibility can be obtained. In addition, according to at least one aspect of the present disclosure, a method for manufacturing the above-mentioned dielectric can be obtained. In addition, according to at least one aspect of the present disclosure, a converter including the above-mentioned dielectric can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] [ Figure 1 ] shows a schematic diagram of a method for manufacturing a dielectric according to the present disclosure.

[0033] [ Figure 2 ] shows a photograph (a photograph in place of a drawing) of the distribution of the ionic liquid in the cross section of the dielectric manufactured in Example 1 by using time-of-flight secondary ion mass spectrometry (TOF-SIMS).

[0034] [ Figure 3 ] shows a graph of temperature-loss tangent (tan δ) curves obtained by dynamic mechanical analysis (DMA) of the dielectrics manufactured in Example 1 and Comparative Example 1.

[0035] [ Figure 4 ] Schematic diagram of a converter according to one aspect of the present disclosure. DETAILED DESCRIPTION

[0036] In the present disclosure, unless otherwise specified, the expression "from XX to YY" or "XX to YY" indicating a numerical range means a numerical range including a lower limit and an upper limit as endpoints. When a numerical range is described in a stepwise manner, the upper limit and the lower limit of each numerical range can be arbitrarily combined. In the present disclosure, for example, descriptions such as "at least one selected from the group consisting of XX, YY, and ZZ" means any one of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, and a combination of XX, YY, and ZZ.

[0037] Hereinafter, embodiments of the present disclosure will be described.Here, the embodiments to be described below are merely examples, and the present disclosure is not limited to these embodiments.

[0038] <Polyurethane elastomer>

[0039] The polyurethane elastomer comprises a matrix and domains dispersed in the matrix. The domains comprise a first structure (polyether structure) represented by the following formula (1).

[0040]

[0041] In formula (1), R 1 It represents an alkylene group having 3 to 6 carbon atoms.

[0042] Generally, polyurethanes obtained by reacting polyols (polyether polyols) having a polyether structure with polyisocyanates have weak intermolecular forces between ether groups. For this reason, since the hardness can be kept very low, it is suitable for imparting flexibility to polyurethane elastomers. On the other hand, due to the weak intermolecular forces, the mobility of the ionic liquid to be described below is high, and due to the occurrence of a phenomenon in which ionic charges are locally concentrated when an electric field is applied (accumulation of space charges), dielectric breakdown easily occurs.

[0043] The domain preferably contains at least one polyether structure represented by formula (1), and more preferably contains a plurality of polyether structures. When the domain contains a plurality of polyether structures represented by formula (1), the polyether structure may be a repeating structural unit.

[0044] The matrix is ​​not particularly limited as long as it is phase-separated from the domain containing the first structure. As will be described below, in order to achieve both softness and low hysteresis loss, it is preferred that the phase separation between the matrix and the domain is clear. That is, the matrix preferably has low compatibility with the polyether structure contained in the domain, and preferably contains the second structure (polycarbonate structure) represented by the following formula (2).

[0045]

[0046] In formula (2), R 2It represents an alkylene group having 3 to 12 carbon atoms.

[0047] Generally, polyurethanes obtained by reacting polyols (polycarbonate polyols) containing polycarbonate structures with polyisocyanates have strong intermolecular forces between carbonate groups. For this reason, the mobility of the ionic liquid to be described below is low, and space charges are unlikely to accumulate, so polyurethanes have excellent resistance to dielectric breakdown. In addition, due to the strong intermolecular forces, polyurethanes exhibit mechanical properties such as good friction characteristics and high wear resistance.

[0048] The matrix contains at least one polycarbonate structure represented by formula (2), and preferably contains a plurality of polycarbonate structures. When the matrix contains a plurality of polycarbonate structures represented by formula (2), the polycarbonate structure may be a repeating structural unit.

[0049] As long as the polyurethane elastomer forms a matrix-domain structure, at least a portion of the outer surface of the dielectric may be formed by the matrix. For example, the entire outer surface of the dielectric may be formed by the matrix.

[0050] The polyurethane elastomer according to the present disclosure has a domain-matrix structure comprising a domain and a matrix. Therefore, the domain comprises a first structure. The inventors have found that when the polyurethane elastomer has such a structure, both excellent softness and low hysteresis loss can be achieved.

[0051] The reason for this is considered to be that since the entire domain acts as a soft crosslinking point due to the effect of entropy elasticity, the polyurethane elastomer exhibits excellent elasticity (entropy elasticity) without plastic deformation due to external forces such as compression, etc. Therefore, it is considered that both excellent flexibility and low hysteresis loss can be achieved.

[0052] In addition, in order to fully utilize the softness derived from the domain, it is preferred that the phase separation between the domain and the matrix is ​​clear. In addition, it is preferred that the matrix and the domain are chemically connected at the interface through a urethane bond. It is particularly preferred that the matrix contains a second structure including a polycarbonate structure represented by formula (2). In this case, both softness and low hysteresis loss can be achieved to a higher level.

[0053] In addition, since the polyurethane elastomer according to the present disclosure has a domain-matrix structure, different functions can be assigned to the matrix and the domain. As an example, when the matrix includes a second structure including a polycarbonate structure represented by formula (2), in addition to softness and low hysteresis loss, resistance to dielectric breakdown, wear resistance and low friction properties can be imparted.

[0054] More surprisingly, the inventors have found that when the dielectric containing polyurethane elastomer contains ionic liquid, it also exhibits a high dielectric constant. The mechanism by which this occurs is unclear, but is believed to be as follows. That is, the polyether structure derived from the polyether polyol contained in the polyurethane elastomer captures and stabilizes the cations of the ionic liquid, so the interaction between ion pairs is reduced. This increases the average distance between ion pairs, which is believed to increase the relaxation component based on the orientation polarization of the dipole.

[0055] In addition, in the temperature-loss tangent (tanδ) curve obtained by dynamic mechanical analysis (DMA) of the dielectric, it is preferred that there are at least two peaks due to the glass transition observed in the temperature range of -80 to +20°C, and it is particularly preferred that there are at least two peaks due to the glass transition observed in the temperature range of -70 to 0°C.

[0056] This indicates that the polyurethane segments containing a polyether structure and the polyurethane segments forming the matrix are clearly phase-separated via the interface between the matrix and the domains.

[0057] As described above, in order to impart resistance to dielectric breakdown, wear resistance and low friction characteristics to the polyurethane elastomer, it is preferred that the matrix contains a second structure which is a polycarbonate structure represented by formula (2). In this case, in the temperature-tan δ curve obtained by DMA of the dielectric, at least one peak due to glass transition is observed in a temperature range of -50°C or less (preferably -80 to -50°C), preferably, at least one peak is in a temperature range of -40°C or more (preferably -40 to 20°C), more preferably, at least one peak is in a temperature range of -60°C or less (preferably -70 to -60°C), and at least one peak is in a temperature range of -35°C or more (preferably -35 to -10°C).

[0058] Generally, a peak due to the glass transition of polyether is observed in the temperature range of -80°C to -50°C or less. In addition, a peak due to the glass transition of polycarbonate is observed in the temperature range of -40°C to +20°C or less. Therefore, the presence of peaks due to the glass transition in two temperature ranges indicates that the fragment composed of the first structure and the fragment composed of the second structure are phase-separated, and the two fragments exist almost incompatible with each other.

[0059] Such clear phase separation prevents the fragments consisting of the first structure from mixing into the matrix. Therefore, when the polyurethane elastomer comprises a second structure comprising a polycarbonate structure as a matrix, both softness and low hysteresis loss can be achieved to a higher level. In addition, it is possible to achieve resistance to dielectric breakdown, good friction characteristics, and high wear resistance.

[0060] The first structure which is contained in the domain of the dielectric and contains the polyether structure represented by the formula (1) will be described. In the first structure which is contained in the domain and contained in the formula (1), R 1 represents an alkylene group having 3 to 6 carbon atoms. 1 It preferably represents an alkylene group having a branched structure having 3 to 5 carbon atoms, and more preferably represents an alkylene group having a branched structure having 3 to 4 carbon atoms.

[0061] By R 1 The alkylene group having 3 to 6 carbon atoms is preferably R. The flexibility of the polymer chain and the density of the ether group are optimized, and the effect of stabilizing the cation derived from the ionic liquid to be described below is ensured. In addition, from the viewpoint that the intermolecular force between the ether groups can be kept low and low hardness can be achieved, it is preferred that R 1 An alkylene group having a branched structure having 3 to 5 carbon atoms is included.

[0062] R 1 Examples include -(CH 2 ) m -(m=3 to 6 (preferably 3 to 5, and more preferably 3 to 4)), -CH 2 CH(CH 3 )-、-CH 2 C(CH 3 ) 2 CH 2 -、-CH 2 CH(CH 3 )CH 2 -、-(CH 2 ) 2 CH(CH 3 )CH 2 -, and -(CH 2 ) 2 CH(CH 3 )(CH 2 ) 2 -. In polyurethane elastomers, all R 1 Can be the same, or different R 1 combination.

[0063] The number average molecular weight (Mn) of the polyether structure represented by formula (1) as a repeating unit in the polyurethane elastomer is preferably from 1,000 to 50,000. The number average molecular weight is based on the raw material polyether polyol. The number average molecular weight (Mn) of the polyether structure represented by formula (1) is more preferably from 1,200 to 30,000.

[0064] When the number average molecular weight is 1,000 or more, the fragment including the polyether structure easily forms a domain. In addition, when the number average molecular weight is 50,000 or less, the phase separation structure can be more stabilized.

[0065] A second structure including a polycarbonate structure represented by formula (2) disclosed as an example of a matrix of a dielectric will be described. In formula (2), R 2 represents an alkylene group having 3 to 12 carbon atoms. 2 It preferably represents an alkylene group having 3 to 9 carbon atoms, and more preferably an alkylene group having 3 to 6 carbon atoms.

[0066] By R 2 The alkylene group having 3 to 12 carbon atoms ensures low compatibility with the segment containing the polyether structure represented by formula (1), and the phase separation between the matrix and the domain can become clearer. In addition, from the viewpoint that the intermolecular force between the carbonate groups can be appropriately reduced and good friction characteristics, high wear resistance and low hardness can be achieved, it is preferred that R 2 Contains an alkylene group having 3 to 12 carbon atoms.

[0067] R 2 Examples include -(CH 2 ) m -(m is an integer from 3 to 12, m is preferably an integer from 3 to 9, and m is more preferably an integer from 5 to 7), -CH 2 C(CH 3 ) 2 CH 2 -、-CH 2 CH(CH 3 )CH 2 -, and -(CH 2 ) 2 CH(CH 3 )(CH 2 ) 2 -. In polyurethane elastomers, all R 2 Can be the same or can use different R 2 combination.

[0068] The number average molecular weight (Mn) of the polycarbonate structure represented by formula (2) as a repeating unit in the polyurethane elastomer is preferably from 500 to 10,000. The number average molecular weight is based on the raw material polycarbonate polyol. The number average molecular weight (Mn) of the polycarbonate structure represented by formula (2) is more preferably from 700 to 8,000. When the number average molecular weight is 500 or more, low compatibility with the polyurethane segment containing the polyether structure represented by formula (1) is ensured, and the phase separation between the matrix and the domain becomes clearer. In addition, when the number average molecular weight is 10,000 or less, the increase in viscosity of the polycarbonate polyol as a raw material can be reduced.

[0069] The number average molecular weight of the polycarbonate structure and the number average molecular weight of the polyol to be described below are values ​​calculated using standard polystyrene molecular weight conversion or hydroxyl value (mg KOH / g) and potency.

[0070] The number average molecular weight in terms of polystyrene molecular weight can be measured using a high performance liquid chromatograph. The measurement can be performed using a column having two columns connected in series (Shodex GPCLF-804, molecular weight exclusion limit: 2×10 6 , separation range: 300 to 2×10 6 ) was carried out using a high-speed GPC apparatus ("HLC-8220GPC", commercially available from Tosoh Corporation).

[0071] When the hydroxyl value and valence are used, the number average molecular weight can be calculated by the following formula: For example, the number average molecular weight of a polyol having a hydroxyl value of 56.1 mgKOH / g and a valence of 2 can be calculated to be 2,000.

[0072] Number average molecular weight = 56.1 × 1,000 × potency ÷ hydroxyl value

[0073] The area ratio of the matrix to the domain observed in a 50 μm×50 μm observation area in the cross section where the domain and the matrix of the dielectric are exposed (matrix / domain) is preferably 40.0 / 60.0 to 90.0 / 10.0, and the area ratio is more preferably 50.0 / 50.0 to 85.0 / 15.0, and still more preferably 55.0 / 45.0 to 80.0 / 20.0. When the area ratio of the matrix / domain is within the above range, the phase separation form becomes more stable, and the matrix and the domain are more likely to be stably formed.

[0074] The area ratio can be controlled by the amount of domain material and matrix material used.

[0075] The arithmetic mean (average diameter) of the circle equivalent diameter of the domains observed in the cross section where the domains and the matrix are exposed is preferably 0.2 to 30.0 μm, and the circle equivalent diameter is more preferably 0.5 to 20.0 μm, and still more preferably 5.0 to 15.0 μm. When the average diameter is 0.2 μm or more, the hardness can be more easily reduced, and when the average diameter is 30.0 μm or less, the phase separation form becomes more stable.

[0076] The equivalent circular diameter of the domain can be controlled, for example, by changing the isocyanate index in the step of obtaining the first urethane prepolymer to be described below. Specifically, the equivalent circular diameter can be increased by reducing the isocyanate index, and the equivalent circular diameter can be reduced by increasing the isocyanate index. In addition, the equivalent circular diameter of the domain can also be controlled by the material and molecular weight of the domain used and the shear force applied when the matrix material is mixed.

[0077] In addition, when observed in three observation areas with a square of 50 μm in the cross section of the dielectric, the ratio of the number of domains having a circularity of 0.60 to 0.95 based on the total number of domains is preferably 70% by number or more, more preferably 80 to 99% by number, and still more preferably 85 to 95% by number.

[0078] In the case of a domain having a circularity within the above range, when the domain recovers from deformation, anisotropy is less likely to occur in the direction in which the domain shape is restored. Therefore, when the number (ratio) of domains having a circularity within the above range increases, recovery from deformation is less likely to be anisotropic. In other words, the dielectric can be made to recover from deformation more isotropically. Therefore, wrinkling, strain, and the like due to anisotropy in recovery from deformation are less likely to occur after recovery from deformation.

[0079] The number ratio can be adjusted, for example, by the speed at which the material is injected into the mold. When the injection speed is low, the shear force applied to the material is also reduced, and thermal curing can be performed while maintaining a high circularity.

[0080] Here, the area ratio of matrix / domain, and the average diameter and circularity of the domain are calculated from a cross-sectional image of the dielectric obtained using a scanning electron microscope. The details will be described below.

[0081] In addition, in the dielectric, the elastic modulus of the domain containing the first structure is preferably designed to be lower than the elastic modulus of the matrix. Specifically, the parameter representing the viscoelastic term of the domain is defined as parameter A, and the parameter representing the viscoelastic term of the matrix is ​​defined as parameter B, which are measured in the viscoelastic image of the cross section in which the domain and the matrix are exposed under a scanning probe microscope. In this case, it is preferred that parameters A and B satisfy A <B。

[0082] The difference in relative elastic modulus between the matrix and the domain of the dielectric can be measured by observing the thinned dielectric under a scanning probe microscope (SPM / AFM). As a scanning probe microscope, "S-Image" (product name, commercially available from Hitachi High-Tech Science Corporation) can be used.

[0083] In addition, examples of devices for thin sections include sharp razors, slicers, and focused ion beam (FIB) devices. Among the above devices, an ultramicrotome capable of preparing ultrathin sections can be particularly appropriately used. Prepare a total of three sections, select any observation area of ​​50 μm square, and observe viscoelastic images in a total of three observation areas.

[0084] The measurement mode of the viscoelastic image taken by SPM is the micro-viscoelastic dynamic force mode (viscoelastic dynamic force mode (VE-DFM)). In addition, as the cantilever, a silicon microcantilever for DFM ("SI-DF3" (product name), commercially available from Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m) was used. In addition, the scanning frequency was 0.5 Hz.

[0085] Here, VE-DFM (micro viscoelastic DFM) is a mode in which an image of the surface shape is obtained while controlling the distance between the probe and the measurement sample so that the vibration amplitude of the cantilever is constant while the cantilever resonates and the viscoelastic distribution is measured at the same time. In VE-DFM, when a periodic force is applied by micro-vibrating the sample in the Z direction, the viscoelastic distribution is imaged from the flexural amplitude of the cantilever. When the sample is hard, the sample deformation is small and the cantilever amplitude is large, while when the sample is soft, the sample deformation vibration is induced and the cantilever amplitude is small.

[0086] The obtained amplitude is converted into a displacement in mV, which becomes a parameter representing the viscoelastic term. Therefore, parameter A and parameter B are indices representing the relationship between the hardness of a domain existing in an observation sample and the hardness of the matrix. Here, in VF-DFM, the magnitude of the amplitude of the cantilever is output as a voltage, and the unit of parameter A and parameter B is mV. In addition, a larger value indicates a higher elasticity.

[0087] After obtaining the viscoelastic image, in each observation area, the parameters representing the viscoelastic items of 10 points each of the matrix and the domain are obtained, and their arithmetic mean values ​​are regarded as the parameter A representing the viscoelastic item of the domain and the parameter B representing the viscoelastic item of the matrix. The measurement flow will be described below.

[0088] The ratio of parameter A to parameter B (A / B) is preferably 0.65 or less, more preferably 0.05 to 0.50, still more preferably 0.05 to 0.40, still more preferably 0.10 to 0.30, and particularly preferably 0.12 to 0.20. When A / B is smaller, because the difference in viscoelasticity between the matrix and the domain is larger, it becomes easier to achieve both softness and low hysteresis loss.

[0089] As a method for increasing the difference in viscoelasticity, it is effective to increase the clarity of phase separation between the domain and the matrix, and as described above, it is preferred that the matrix contains a second structure including a polycarbonate structure represented by formula (2). In addition, as will be described below, in the dielectric manufacturing step, the use of a manufacturing step in which a polyol used as a matrix and a polyether polyol used as a domain are reacted in advance to form a urethane prepolymer is also effective as a method for increasing the clarity of phase separation, that is, increasing the difference in viscoelasticity.

[0090] Parameters A and B can be adjusted, for example, by the elastic modulus of the domain and the matrix. The elastic modulus of the matrix can be increased by, for example, increasing the crosslinking density of the matrix using a trimer compound or a polymer compound of a polyisocyanate as a raw material for forming the matrix. With regard to the elastic modulus of the domain, for example, by increasing the molecular weight of the polyether polyol as a raw material for forming the domain, the crosslinking density of the domain is reduced, and the elastic modulus is reduced.

[0091] In addition, the chemical structures of the components contained in the matrix and the domains can be analyzed using, for example, a spectroscopic analysis device such as an AFM infrared spectroscopic analysis device, a microscopic infrared spectroscopic analysis device, or a microscopic Raman spectroscopic analysis device, or a mass spectrometer.

[0092] <Ionic Liquids>

[0093] The ionic liquid is a liquid containing a cationic component and an anionic component, and is a salt that exists as a liquid in a wide temperature range. Examples thereof include salts having a melting point of 100° C. or less obtained using relatively large organic ions as ionic species to form the salt. The ionic liquid has a function of improving the dielectric properties of the polyurethane elastomer.

[0094] The cationic component is not particularly limited and may be, for example, at least one selected from the group consisting of imidazolium ions, pyridinium ions, pyrrolidinium ions, ammonium ions, piperidinium ions, and phosphonium ions. Among these, at least one selected from the group consisting of ammonium ions and imidazolium ions is preferred. That is, the ionic liquid is preferably at least one ionic liquid selected from the group consisting of ammonium ionic liquids and imidazolium ionic liquids.

[0095] Compared to other cationic frameworks, ammonium ions generally have a higher resistance to reduction potentials, i.e., a wider potential window. Therefore, in dielectrics for converter applications that may be exposed to high electric fields in some cases, ionic liquids composed of ammonium ions that are less likely to undergo electrolysis reactions are appropriately used.

[0096] In addition, the reason why imidazolium ions can be appropriately used is as follows. As mentioned above, the polyether structure derived from polyether polyurethane contained in the domain of polyurethane elastomer stabilizes cations, and therefore exhibits excellent dielectric properties. In this regard, because imidazolium ions have delocalized positive charges and are planar, they are easily stabilized according to the polyether structure, and the Coulomb interaction with anions is relatively weaker than the Coulomb interaction with anions of other cationic skeletons, so a high level of dielectric constant increase can be expected. In addition, due to charge delocalization, ionic liquids composed of imidazolium ions generally have a lower viscosity than the viscosity of other cationic skeletons, and are preferred in view of the treatment in the dielectric manufacturing step.

[0097] The ammonium ion may be, for example, at least one selected from the group consisting of quaternary ammonium salts such as N-trimethyl-N-propylammonium, N-trimethyl-N-butylammonium, bis(2-hydroxyethyl)-methyl-octylammonium, bis(2-hydroxyethyl)-methyl-decylammonium, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium, and N,N-(2-hydroxyethyl)-N-(9-octadecene)-N-methylammonium.

[0098] In addition, the imidazolium ion may be, for example, at least one selected from the group consisting of 1-ethyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-hexyl-2,3-dimethylimidazolium, 1,3-bis(2-hydroxyethyl)imidazolium, 1-(2-hydroxyethyl)-3-methylimidazolium, 1-(3-hydroxypropyl)-3-methylimidazolium, 1-butyl-3-(2-hydroxyethyl)imidazolium, and 1-ethyl-3-(2-hydroxyethyl)imidazolium.

[0099] The anion component is not particularly limited and may be, for example, selected from halogen ions, BF 4 - PF 6 - CF 3 SO 3 - ,(CF 3 SO 2 ) 2 N - , and (FSO 2 ) 2 N -In order to improve the dielectric properties, it is preferred that the interaction between the cation and the anion is not strong. Therefore, BF is selected as an anion having a large molecular volume. 4 - PF 6 - CF 3 SO 3 - ,(CF 3 SO 2 ) 2 N - , and (FSO 2 ) 2 N - At least one of the group consisting of is particularly preferred. The anion is more preferably selected from BF 4 - PF 6 - CF 3 SO 3 - and (CF 3 SO 2 ) 2 N - At least one anion of the group consisting of.

[0100] In addition, the ionic liquid preferably has a reactive functional group that reacts with an isocyanate group. Examples of reactive functional groups that react with an isocyanate group include hydroxyl groups. Because the ionic liquid has a reactive functional group that reacts with an isocyanate group, it reacts with the polyisocyanate used in the step of manufacturing the polyurethane elastomer to be described below and is incorporated into the polymer network. This limits the mobility of the ionic liquid when an electric field is applied, and can minimize the reduction of resistance to dielectric breakdown caused by space charge accumulation. In addition, in order to prevent the ionic liquid from flowing out over time, it is also useful to incorporate the ionic liquid into the polymer network. For example, it is preferred that the cation has a hydroxyl group.

[0101] Specific examples of the ionic liquid that can be suitably used in the present disclosure include at least one selected from the group consisting of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, imide, 1-hexyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide, 1,3-bis(2-hydroxyethyl)imidazolium bis(trifluoromethanesulfonyl)imide, 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-(3-hydroxypropyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-propyl 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-ethylpyridinium bis(trifluoromethanesulfonyl)imide, 1-propylpyridinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide, N-trimethyl-N-butylammonium bis(trifluoromethanesulfonyl)imide, bis(2-hydroxyethyl)-methyl-octylammonium bis(trifluoromethanesulfonyl)imide, bis(2-hydroxyethyl)-methyl-decylammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide, and N,N-(2-hydroxyethyl)-N-(9-octadecene)-N-methylammonium bis(trifluoromethanesulfonyl)imide.

[0102] In addition, examples of commercially available ionic liquid products include "ELEXCEL AS-110", "ELEXCEL MP-442", "ELEXCEL IL-210", "ELEXCEL MP-471", "ELEXCEL MP-456", and "ELEXCEL AS-804" (commercially available from DKS Co., Ltd.), "HMI-FSI" (commercially available from Mitsubishi Materials Corporation), "CIL-312", "CIL-542" and "CIL-313" (commercially available from Japan Carlit Co., Ltd.), and IL-P series, IL-A series, IL-C series, IL-IM series, IL-AP series, and IL-OH series (commercially available from Koei Chemical Co., Ltd.), but the present invention is not particularly limited thereto.

[0103] The ionic liquid is preferably mainly distributed in the matrix of the dielectric. Here, the term "mainly distributed" means that the ratio D / C of the concentration D to the concentration C defined below satisfies D / C>1.0. The concentration of the ionic liquid per 50 μm×50 μm observation area observed in the cross section of the domain in which the dielectric is exposed and the matrix is ​​defined as concentration C, and further, the concentration of the ionic liquid contained in the matrix in the 50 μm×50 μm observation area is defined as concentration D.

[0104] D / C is preferably from 1.0 to 3.0, more preferably from 1.2 to 2.0, and still more preferably from 1.3 to 1.7.

[0105] D / C can be increased by reducing the area ratio of the matrix / domain in the dielectric. Alternatively, D / C can be decreased by increasing the area ratio of the matrix / domain in the dielectric.

[0106] When the ionic liquid is mainly distributed in the matrix, good resistance to dielectric breakdown is easily obtained. To explain the reason, a case where the ionic liquid is present in a large amount in a domain formed by a polyether urethane is considered. In this case, it is believed that because weak intermolecular forces act between the polyether chains, an environment in which ions can easily move is generated, and when an electric field is applied, the ions are concentrated at the domain-matrix interface.

[0107] Typically, when the electric field is released, the concentration of ions at the interface decreases, but when the dielectric is used for converter applications, the above phenomenon occurs repeatedly when the electric field is repeatedly applied, so the bias of the ionic charge is fixed. In this case, it is believed that the electric field is locally concentrated at a location inside the dielectric, which creates an environment where dielectric breakdown is likely to occur. For the above reasons, it is preferred that the ionic liquid is mainly distributed in the matrix of the dielectric. In order to make the ionic liquid mainly distributed in the matrix, it is effective to make the phase separation between the matrix and the domain clear, and it is preferred that the matrix contains a second structure including a polycarbonate structure represented by formula (2).

[0108] More preferably, the ionic liquid is preferably mainly distributed in the matrix near the interface between the matrix and the domain. Here, the term "mainly distributed near the interface" means that the concentration D and the following concentration D3 satisfy D3 / D>1.0. The concentration D3 is the concentration of the ionic liquid contained in the vicinity of the interface of the domain in the matrix in a 50 μm×50 μm observation area observed in a cross section of the domain and the matrix where the dielectric is exposed.

[0109] The definition of the vicinity of the interface will be described below. When the ionic liquid is configured in this manner, the cations are effectively stabilized according to the ether structure of the polyether polyurethane, and thus a higher level of increase in the dielectric constant can be expected.

[0110] A method for calculating the concentrations C and D of the ionic liquid will be described. First, the dielectric is sliced ​​into thin slices. As a thin slice device, a microtome can be exemplified.

[0111] In the cross section of the obtained slice, an arbitrary observation area of ​​50 μm square is set, and the mass spectrum fragment ions detected in the observation area are obtained using a time-of-flight secondary ion mass spectrometer (TOF-SIMS). Examples of time-of-flight secondary ion mass spectrometers (TOF-SIMS) include nanoTOF II (commercially available from ULVAC-PHI, Inc.).

[0112] In the mass spectrum of the fragment ions obtained in the observation area, the intensity of the cations or anions of the ionic liquid, or the fragment ions corresponding to their decomposition products, is expressed as the brightness of the observation area, and a brightness curve of the observation area is generated. Next, the average brightness of the entire observation area is defined as the concentration C of the ionic liquid in the observation area. In addition, the average brightness of the area within the observation area corresponding to the matrix is ​​defined as the concentration D of the ionic liquid contained in the matrix.

[0113] Here, the definition of the vicinity of the interface and the method for calculating the concentration D3 of the ionic liquid near the interface will be further described. The area of ​​any domain is set to a1, and its geometric center is set to c1. In addition, a region a2 having the same geometric center c1 and a shape similar to a1 is considered with a similarity of 1.2.

[0114] In this case, the region a3 obtained by removing a1 from a2 is defined as the vicinity of the interface of the domain in the matrix. In this way, the union of the vicinity regions a3 defined for each domain is defined as A3, and the region A3 is defined as the vicinity of the interface. For the brightness curve in the above-mentioned observation region, the concentration D3 of the ionic liquid near the interface can be obtained by calculating the average brightness in the region A3.

[0115] Here, when a3 includes other domains, such as when the distance between domains is short, the domain is partially excluded from a3.

[0116] The content of ionic liquid in the dielectric based on the mass of the dielectric is preferably 0.5 to 8.0 mass %, more preferably 2.0 to 8.0 mass %, and still more preferably 2.0 to 3.0 mass %. When the content of ionic liquid is 0.5 mass % or more, a higher level increase in dielectric constant can be expected compared to when the content is less than this value. In addition, when the content of ionic liquid is 2.0 mass % or more, the main distribution of ionic liquid at the matrix-domain interface effectively occurs, and an even higher level increase in dielectric constant can be expected. In addition, when the content of ionic liquid is 8.0 mass % or less, it becomes easier to achieve high dielectric constant and resistance to dielectric breakdown.

[0117] Confirmation of the presence of the ionic liquid in the dielectric and calculation of the content of the ionic liquid can be performed by the following method. The ionic liquid can exist in two forms depending on the presence of a reactive functional group that reacts with an isocyanate group and the reactivity of the reactive group. That is, there are two forms: a form in which the ionic liquid is incorporated into the polymer network via an isocyanate group, and a form in which the ionic liquid is not incorporated into the polymer network but remains free.

[0118] The content of the ionic liquid of the former form can be confirmed by structural analysis using, for example, NMR, GC-MS, or LC-MS. The content of the ionic liquid of the latter form can be determined by extracting the ionic liquid from the surface layer and quantitatively determining it. As the solvent for extraction, a solvent that can dissolve the ionic liquid is selected. Its specific example includes methyl ethyl ketone (MEK). Here, the solvent in the extract after extraction is removed using a rotary evaporator, etc., and the ionic liquid is separated by various types of chromatography, so the content ratio of the ionic liquid in the dielectric can be quantitatively determined.

[0119] <Dielectric>

[0120] The relative dielectric constant of the dielectric is preferably 10.0 or more. More preferably, it should be 15.0 or more. Here, the relative dielectric constant in the present disclosure is the relative dielectric constant observed when an alternating voltage of 100 Hz is applied at room temperature. The upper limit of the relative dielectric constant is not particularly limited. The relative dielectric constant is preferably 10.0 to 200.0, and more preferably 15.0 to 100.0.

[0121] When the relative dielectric constant is within the above range, the dielectric can be more appropriately used as a converter dielectric having excellent conversion efficiency between electrical energy and mechanical energy. The relative dielectric constant can be obtained by using an impedance analyzer (1260A, commercially available from Solartron) and a dielectric interface (1296A, commercially available from Solartron), inserting the dielectric into a four-terminal sample holder (SH2-Z type, commercially available from Toyo Corporation), sweeping at room temperature with an AC voltage of 0.1 Vpp and a frequency of 0.01 Hz to 1 MHz, and measuring the relative dielectric constant at 100 Hz.

[0122] The relative dielectric constant of the dielectric can be controlled by the amount of domain material and matrix material used (matrix / domain area ratio), chemical structure, and the content of ionic liquid.

[0123] In addition, the Young's modulus of the dielectric is preferably less than 2.5 MPa. More preferably, it should be 0.1 to 2.5 MPa, and still more preferably 1.0 to 2.2 MPa. Here, in the present disclosure, the Young's modulus is the real part of the complex elastic modulus obtained when a sinusoidal strain of 1 Hz is applied at room temperature. When the Young's modulus is within the above range, the dielectric can be flexibly deformed against external forces such as compression and tension. The Young's modulus can be obtained by measuring the dependence of the complex elastic modulus on frequency using a viscoelasticity measuring device (product name: Rheogel-E4000, commercially available by UBM).

[0124] Young's modulus can be controlled by the amount of domain and matrix material used (matrix / domain area ratio), chemical structure, and crosslink density.

[0125] In addition, the hysteresis loss of the dielectric is preferably 10% or less, and more preferably 6% or less. Here, the hysteresis loss in the present disclosure is a value calculated from the following formula when a stress-strain curve of the dielectric is obtained under the conditions of 33% displacement, 0.275 mm / sec displacement speed, and 5 reciprocating displacements at room temperature.

[0126] Hysteresis loss [%] = (1-(elastic deformation workload / total deformation workload)) × 100

[0127] Hysteresis losses can be controlled by the amount of domain and matrix material used (matrix / domain area ratio), chemical structure, and cross-link density.

[0128] When the hysteresis loss is within the above range, the dielectric can be more appropriately used as a converter dielectric having excellent recovery and low energy loss associated with displacement. The hysteresis loss can be calculated by measuring the stress-strain curve according to the above protocol using a viscoelasticity measurement device (product name: Rheogel-E4000, commercially available from UBM) in tension mode.

[0129] Lower hysteresis loss is preferred, and the lower limit is not particularly limited. The hysteresis loss may be, for example, 0 to 10%, or 1 to 6%.

[0130] In addition, the dielectric breakdown strength of the dielectric is preferably 15kV / mm or more, and more preferably 20kV / mm or more. Here, the dielectric breakdown strength in the present disclosure is defined as the electric field strength at which a leakage current exceeding 5mA is detected in a dielectric without applied strain at room temperature. When the dielectric breakdown strength is within the above range, the dielectric can be appropriately used as a converter dielectric that can withstand use under higher voltage conditions. The dielectric breakdown strength can be obtained by detecting the leakage current using a withstand voltage tester (GPT-9903A, commercially available by Texio Technology Corporation) while changing the electric field strength applied to the dielectric.

[0131] The upper limit of the dielectric breakdown strength is not particularly limited. The dielectric breakdown strength is, for example, 15 to 100 kV / mm, 20 to 50 kV / mm.

[0132] The dielectric breakdown strength can be controlled by the amount of domain material and matrix material used (matrix / domain area ratio), chemical structure, and the content of ionic liquid.

[0133] <Method for manufacturing dielectric>

[0134] The dielectric can be synthesized by, for example, a method comprising the following steps (i) to (iv). The dielectric is preferably a dielectric produced by a method comprising the following steps (i) to (iv).

[0135] Step (i): a step of obtaining a second urethane prepolymer having at least two hydroxyl groups by reacting a first urethane prepolymer having at least one isocyanate group (preferably at least two isocyanate groups) with a first polycarbonate polyol having at least two hydroxyl groups

[0136] Step (ii): a step of obtaining a first dispersion by dispersing droplets comprising at least a portion of the second urethane prepolymer in the second polycarbonate polyol (which may be an excess unreacted component of the first polycarbonate polyol)

[0137] Step (iii): a step of obtaining a second dispersion by dispersing an ionic liquid in the first dispersion

[0138] Step (iv): preparing a dielectric-forming mixture comprising a second dispersion and a polyisocyanate having at least two isocyanate groups, and then reacting the second urethane prepolymer, the second polycarbonate polyol (the ionic liquid when the ionic liquid contains a hydroxyl group), and the polyisocyanate having at least two isocyanate groups in the dielectric-forming mixture to form a dielectric.

[0139] Will refer to Figure 1One aspect of the method for manufacturing the above-mentioned dielectric is described. Here, the method for manufacturing the dielectric is not limited to this aspect.

[0140] In step (i), a first urethane prepolymer 51 having at least one isocyanate group, preferably at least two isocyanate groups, and a first polycarbonate polyol 52 having at least two hydroxyl groups are mixed. Next, the isocyanate group and the hydroxyl group in the obtained mixture are reacted with each other in the presence of a curing catalyst to connect them via a urethane bond, thereby obtaining a second urethane prepolymer 53 having at least two hydroxyl groups.

[0141] Here, in Figure 1 , polyether having two isocyanate groups is shown as an example of the first urethane prepolymer 51. The first urethane prepolymer 51 may be, for example, a first urethane prepolymer including the second structure, and is preferably a reaction product of a polyol such as polyether diol and a polyisocyanate.

[0142] In step (ii), a dispersion is obtained in which droplets containing at least a portion of the second urethane prepolymer are dispersed in the second polycarbonate polyol. Here, the second urethane prepolymer may be mixed with the second polycarbonate polyol newly added in this step. In addition, the excess unreacted components of the first polycarbonate polyol in step (i) may also be used as the second polycarbonate polyol.

[0143] The first urethane prepolymer 51 contained in the second urethane prepolymer 53 is incompatible with the second polycarbonate polyol 55 , and forms droplets 54 .

[0144] On the other hand, the first polycarbonate polyol 52 contained in the second urethane prepolymer 53 is compatible with the second polycarbonate polyol 55. Therefore, the droplets 54 containing the first urethane prepolymer 51 constituting a part of the second urethane prepolymer 53 are uniformly and stably dispersed in the second polycarbonate polyol 55 via the first polycarbonate polyol 52. Thus, a first dispersion in which the droplets 54 containing the first urethane prepolymer 51 (second structure) are dispersed in the second polycarbonate polyol 55 is obtained.

[0145] In step (ii), the second polycarbonate polyol 55 in which the droplets 54 are dispersed may be an unreacted component of the first polycarbonate polyol and the first urethane prepolymer used in step (i). That is, in step (i), when an excess of the first polycarbonate polyol relative to the first urethane prepolymer is used, a dispersion in which the second urethane prepolymer 53 described in step (ii) is dispersed in an excess of the first polycarbonate polyol (i.e., the second polycarbonate polyol 55) may be obtained.

[0146] Here, even when an excess of the first polycarbonate polyol is used, a polycarbonate polyol (second polycarbonate polyol) may be added as a dispersion medium for the second urethane prepolymer. In this case, the polycarbonate polyol to be added may have the same chemical composition as the first polycarbonate polyol used in step (i) or may have a different chemical composition.

[0147] On the other hand, in step (i), when the first polycarbonate polyol and the first urethane prepolymer are reacted in equivalent amounts and the first polycarbonate polyol is completely consumed, in step (ii), new polycarbonate polyol is used as the second polycarbonate polyol to prepare a dispersion. In this case, the polycarbonate polyol used as the second polycarbonate polyol may have the same chemical composition as the first polycarbonate polyol or may have a different chemical composition.

[0148] Here, when an excess unreacted component of the first polycarbonate polyol is used as the second polycarbonate polyol, step (i) and step (ii) may be performed simultaneously.

[0149] In step (iii), a second dispersion is obtained in which the ionic liquid is dispersed in the first dispersion obtained in step (ii). As a dispersion method, any known method such as mechanical stirring can be used.

[0150] Finally, in step (iv), a dielectric-forming mixture is prepared containing the second dispersion prepared in step (iii) and the polyisocyanate 56 having at least two isocyanate groups. Next, the terminal hydroxyl group of the second urethane prepolymer 53, the hydroxyl group of the second polycarbonate polyol 55, and the isocyanate group of the polyisocyanate 56 in the dielectric-forming mixture react with each other.

[0151] It is preferred that the ionic liquid contains a hydroxyl group. In step (iv), it is preferred that the second urethane prepolymer, the second polycarbonate polyol, the ionic liquid, and the polyisocyanate having at least two isocyanate groups in the dielectric-forming mixture react with each other to form a dielectric.

[0152] In this way, a network structure is formed via a urethane bond, and the dielectric-forming mixture is cured to obtain a dielectric according to the present disclosure. The dielectric 33 obtained in this way has a matrix-domain structure in which domains 32 containing a polyether structure (i.e., a first structure) derived from the first urethane prepolymer 51 are dispersed in a matrix 31 containing a urethane elastomer having a polycarbonate structure (i.e., a second structure) derived from the first polycarbonate polyol 52 and the second polycarbonate polyol 55.

[0153] In addition, the domain 32 may be mainly composed of a polyether structure (first structure), and the interior of the domain may be substantially free of a cross-linked structure. In other words, the domain 32 may be present in the matrix in a substantially liquid state. Therefore, in the dielectric 33 according to the present disclosure, the domain may have a low elastic modulus.

[0154] In addition, in the domain, the liquid portion is not simply confined in the matrix, but the domain and the matrix are chemically bonded via a urethane bond at the boundary portion of the domain and the matrix. Therefore, when the load applied to the dielectric 33 is removed, the recovery of the domain from deformation can be associated with the recovery of the matrix from deformation.

[0155] That is, there is substantially no cross-linked structure, for example, inside the liquid domain. Therefore, it is difficult for the domain deformed by the load applied to the dielectric 33 to recover from the deformation autonomously. However, in the dielectric according to the present disclosure, the domain is chemically bonded to the matrix (via a urethane bond) at the boundary portion between the domain and the matrix, so the matrix can recover from the deformation, and the domain can also recover from the deformation. Therefore, even when the dielectric 33 is repeatedly subjected to loading and unloading, stable deformation (deformation amount) and stable recovery from deformation are achieved, and low hysteresis loss is more easily achieved.

[0156] In order to make the ionic liquid mainly distributed in the matrix, it is preferred to disperse the ionic liquid after step (ii) as described above. In step (ii), because the interface between the matrix and the domain is firmly formed via a chemical bond (urethane bond), the ionic liquid is prevented from entering the domain, and a state in which the ionic liquid is mainly distributed in the matrix can be achieved. Alternatively, in step (ii), the ionic liquid can be well dispersed in the matrix by using a second polycarbonate polyol in which the ionic liquid has been pre-dispersed and omitting step (iii).

[0157] Here, steps (i) to (iv) are steps of stably and uniformly dispersing the polyether polyol in the polycarbonate polyol when the compatibility between the polycarbonate polyol used as the matrix and the polyether polyol used as the domain is low. That is, the first urethane prepolymer 51 is reacted with the first polycarbonate polyol 52 to form the second urethane prepolymer 53.

[0158] Therefore, a dispersion can be obtained in which the polyether polyol fragments derived from the first urethane prepolymer 51 are stably and uniformly dispersed in the second polycarbonate polyol. Therefore, it is easy to prepare a dielectric 33 in which domains 32 having high circularity, small size on the order of micrometers, and relatively uniform size distribution are dispersed in the matrix 31.

[0159] Here, another method for mixing materials with low compatibility is, for example, a mixing and dispersion method using high shear force. However, in this method, high shear force is applied to the polyol containing the first structure, so the shape of the domain is distorted, the circularity is reduced, and the size of the domain also becomes uneven. In addition, the dispersion state is also unstable, and the domains are aggregated in a relatively short time.

[0160] In addition, the incompatibility between the polyether polyol and the polycarbonate polyol is not ensured, and the phase separation between the matrix and the domain of the obtained urethane elastomer becomes unclear. Therefore, the main distribution of the ionic liquid in the matrix is ​​not ensured, which leads to a decrease in resistance to dielectric breakdown. In addition, the unclear phase separation also affects the mechanical properties, and it is difficult to obtain a dielectric having excellent softness and low hysteresis loss characteristics according to the present disclosure.

[0161] The amount of the polyol containing the first structure and the polyol containing the second structure used is not particularly limited, and may be any amount in which the droplets 54 can be dispersed in the second polycarbonate polyol 55 to form clear domains. For example, the ratio of the polyol containing the first structure to the polyol containing the second structure on a mass basis is preferably 15:85 to 50:50, and more preferably 20:80 to 50:50.

[0162] The first urethane prepolymer is a polyether having at least one isocyanate group and a structure represented by formula (1). The first urethane prepolymer can be obtained by, for example, the following steps.

[0163] The polyether polyol having at least two hydroxyl groups and a structure represented by formula (1) is reacted with a polyisocyanate having at least two isocyanate groups.

[0164] Examples of polyether polyols include polyether polyols containing an alkylene structure such as polypropylene glycol, polytetramethylene glycol, copolymers of tetrahydrofuran and neopentyl glycol, copolymers of tetrahydrofuran and 3-methyltetrahydrofuran, and random or block copolymers of these polyalkylene glycols. These may be used alone or in combination of two or more thereof.

[0165] Among these polyether polyols, amorphous polyether polyols are preferred because the mobility of the ether group is high, the effect of stabilizing cations is strong, and low hardness can be achieved. Among the polyether polyols, more preferred is one containing at least one selected from polypropylene glycol, a copolymer of tetrahydrofuran and neopentyl glycol, and a copolymer of tetrahydrofuran and 3-methyltetrahydrofuran. Still more preferred is one containing at least polypropylene glycol.

[0166] The number average molecular weight of the polyether polyol is preferably from 1,000 to 50,000, and more preferably from 1,200 to 30,000. When the number average molecular weight is 1,000 or more, the fragment containing the polyether structure easily forms a domain. In addition, when the number average molecular weight is 50,000 or less, it is preferred because the phase separation structure is better stabilized.

[0167] Examples of polyisocyanates that react with polyether polyols include pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, or trimer compounds (isocyanurates) or polymer compounds of these polyisocyanates, allophanate type polyisocyanates, buret type polyisocyanates, and water-dispersible polyisocyanates. These polyisocyanates can be used alone or two or more thereof can be used in combination.

[0168] Among the polyisocyanates exemplified above, difunctional isocyanates (diisocyanates) having two isocyanate groups are preferred because they have high compatibility with polyether polyols and physical properties such as viscosity are easily adjusted. Among the above polyisocyanates, it is more preferred to include at least one selected from hexamethylene diisocyanate, isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate. Xylylene diisocyanate is still more preferred.

[0169] In the step of obtaining the first urethane prepolymer by reacting the polyether polyol containing the structure represented by formula (1) with a polyisocyanate, the isocyanate index is preferably 0.05 to 8.0, and more preferably 0.1 to 5.0. When the isocyanate index is within the above range, the amount of the component derived from the first urethane prepolymer remaining without forming a network structure can be reduced, and the exudation of the liquid substance from the polyurethane elastomer can be suppressed.

[0170] Here, the isocyanate index indicates the ratio of the number of moles of isocyanate groups in the isocyanate compound to the number of moles of hydroxyl groups in the polyol compound ([NCO] / [OH]).

[0171] The first urethane prepolymer obtained by reacting a polyether polyol having a structure represented by formula (1) with a polyisocyanate has a structure in which a hydroxyl group and an isocyanate group react with each other to link them via a urethane bond. The number average molecular weight is preferably from 1,000 to 100,000, and more preferably from 1,200 to 50,000.

[0172] The first polycarbonate polyol is not particularly limited as long as it is phase-separated from the first urethane prepolymer, and is preferably a polycarbonate polyol having at least two hydroxyl groups and a structure represented by formula (2). Examples of the first polycarbonate polyol include reaction products of polyhydric alcohols and phosgene, and ring-opening polymers of cyclic carbonates (alkylene carbonates, etc.).

[0173] Examples of the polyhydric alcohol include propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylene glycol, 1,3-tetramethylene glycol, 2-methyl-1,3-trimethylene glycol, 1,5-pentamethylene glycol, neopentyl glycol, 1,6-hexamethylene glycol, 3-methyl-1,5-pentamethylene glycol, 2,4-diethyl-1,5-pentamethylene glycol, glycerin, trimethylolpropane, trimethylolethane, cyclohexanediol (1,4-cyclohexanediol, etc.), and sugar alcohols (xylitol, sorbitol, etc.).

[0174] Examples of the alkylene carbonate include trimethylene carbonate, tetramethylene carbonate, and hexamethylene carbonate.

[0175] The number average molecular weight (Mn) of the first polycarbonate polyol is preferably from 500 to 10,000, and more preferably from 700 to 8,000. When the number average molecular weight is 500 or more, low compatibility with the polyurethane segment containing the polyether structure represented by formula (1) is ensured, and the phase separation between the matrix and the domain can be clearer. In addition, when the number average molecular weight is 10,000 or less, it is preferred because the handling difficulty caused by the increase in the viscosity of the polycarbonate polyol as a raw material is prevented.

[0176] The number average molecular weight of the first polycarbonate polyol can be calculated using the hydroxyl value (mg KOH / g) and the titer, similar to the number average molecular weight of the polyether polyol.

[0177] As the polyisocyanate 56 having at least two isocyanate groups used in step (iv), the same polyisocyanates as those exemplified as the raw material of the first urethane prepolymer can be used. These polyisocyanates may be used alone or two or more thereof may be used in combination.

[0178] As the polyisocyanate used in step (iv), among the polyisocyanates exemplified above, in order to increase the elastic modulus of the substrate, it is preferred to include a polyisocyanate having at least three isocyanate groups, such as a trimer compound (isocyanurate) or a polymer compound of a polyisocyanate, an allophanate-type polyisocyanate, and a buret-type polyisocyanate.

[0179] More preferably, at least one selected from the group consisting of a trimer compound (isocyanurate) of pentamethylene diisocyanate, a trimer compound (isocyanurate) of hexamethylene diisocyanate, a polymer compound of diphenylmethane diisocyanate, and polymer MDI can be used. Curing catalysts for urethane elastomers are roughly classified into polyurethane catalysts (reaction promoting catalysts) for promoting rubberization (resinization) and foaming, and isocyanation catalysts (isocyanate trimerization catalysts). In the present disclosure, these can be used alone or in combination.

[0180] Among the above examples, polymeric MDI is preferred. Here, polymeric MDI is a mixture of monomeric MDI and high molecular weight polyisocyanate, and is represented by the following formula (A). In formula (A), n is preferably from 0 to 4.

[0181] As the polymer MDI, commercially available products can be used, and examples thereof include Millionate MR series (commercially available from Tosoh Corporation) such as Millionate MR200 (product name).

[0182]

[0183] As the polyisocyanate 56 having at least two isocyanate groups, it is preferred to use a polyisocyanate having at least three isocyanate groups such as polymer MDI in combination with a difunctional isocyanate having two isocyanate groups. According to the above combination, the crosslinking density can be controlled, so this combination is preferred because both low hardness and low compression permanent strain are achieved.

[0184] The amount of the polyisocyanate with at least three isocyanate groups and the difunctional isocyanate with two isocyanate groups is not particularly limited. When mixed into the dispersion in step (iv), the ratio of the amount of the difunctional isocyanate: polyisocyanate with at least three isocyanate groups is preferably 3:1 to 1:10, and more preferably 1:1 to 1:6. The amount of the polyisocyanate per 100 parts by mass of the dispersion in step (iv) is not particularly limited, and can be, for example, 1 to 10 parts by mass, or 3 to 8 parts by mass.

[0185] Examples of the urethanization catalyst include tin-based urethanization catalysts such as dibutyltin dilaurate and stannous octoate, and amine-based urethanization catalysts such as triethylenediamine, tetramethylguanidine, pentamethyldiethylenetriamine, diethylimidazole, tetramethylpropylenediamine, N,N,N'-trimethylaminoethylethanolamine, and 1,4-diazabicyclo[2.2.2]octane-2-methanol. These can be used alone or in combination. Among these urethanization catalysts, triethylenediamine and 1,4-diazabicyclo[2.2.2]octane-2-methanol are preferred because they particularly promote urethane reactions.

[0186] Examples of isocyanation catalysts include Li 2 O and (Bu 3 Sn) 2 O and other metal oxides, such as NaBH 4 Hydrogenated compounds such as NaOCH 3 , KO-(t-Bu), and borate alcoholates such as N(C 2 H 5 ) 3 、N(CH 3 ) 2 CH 2 C 2 H 5 , and 1,4-vinylpiperazine (DABCO) and other amine compounds, such as HCOONa, Na 2 CO 3 、PhCOONa / DMF、CH 3 COOK, (CH 3 COO 2 Ca, alkaline soaps, and alkaline carboxylate compounds such as naphthenates, alkaline formate compounds, and compounds such as ((R) 3 -NR'OH)-OCOR" and other quaternary ammonium salt compounds.

[0187] In addition, examples of combined catalysts (co-catalysts) used as isocyanation catalysts include amine / epoxide, amine / carboxylic acid, and amine / alkylene imide. These isocyanation catalysts and combined catalysts may be used alone or in combination.

[0188] As a catalyst for urethane synthesis, N,N,N′-trimethylaminoethylethanolamine (hereinafter referred to as ETA) which serves as a urethanization catalyst alone and also as an isocyanation catalyst can be used.

[0189] In the method for producing a dielectric, a chain extender (multifunctional low molecular weight polyol) may be used as necessary. The chain extender may be, for example, a diol having a number average molecular weight of 1,000 or less.

[0190] Examples of the diol include ethylene glycol (EG), diethylene glycol (DEG), propylene glycol (PG), dipropylene glycol (DPG), 1,4-butanediol (1,4-BD), 1,6-hexanediol (1,6-HD), 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, benzyl alcohol (p-phenylenediol), and triethylene glycol.

[0191] In addition, examples of chain extenders other than diols include trivalent or higher polyhydric alcohols. Examples of trivalent or higher polyhydric alcohols include trimethylolpropane, glycerol, pentaerythritol, and sorbitol. These can be used alone or in combination.

[0192] In addition, additives such as a conductive agent, a pigment, a plasticizer, a water-repellent agent, an antioxidant, a UV absorber, and a light stabilizer may be used in combination as necessary.

[0193] <Converter>

[0194] Another aspect of the present disclosure provides a converter comprising a dielectric. The converter comprises at least two electrodes and a dielectric inserted between the electrodes. Wiring for conducting electricity to a power source or control element can be connected to the electrodes. In addition, the dielectric and the electrodes can be alternately stacked to form a stacked structure.

[0195] Figure 4 An example of a converter according to the present disclosure is shown. The converter 6 includes a dielectric 61 according to the present disclosure and a pair of electrodes 62 with the dielectric 61 therebetween. Applications of the converter are not particularly limited, and the converter can be used, for example, as an actuator, a sensor, or a power generation element.

[0196] When the converter is used as an actuator, a driving force can be induced in the dielectric 61 by applying a potential difference between a pair of electrodes 62 using the circuit device 7. When the converter is used as a sensor, the amount of deformation can be obtained by measuring a change in capacitance due to expansion of the converter 6 using the circuit device 7. When the converter is used as a power generation element, electric energy according to the deformation of the converter can be obtained by a known method described in, for example, Sustainability 2021, 13(17), 9881.

[0197] The thickness of the dielectric 61 can be appropriately determined according to the application of the transducer 6, and when the transducer is used as an actuator, a thinner dielectric layer is preferred for miniaturization, low voltage driving, and increased displacement. Considering the resistance to dielectric breakdown, the thickness of the dielectric layer is preferably from 1 μm to 1,000 μm.

[0198] The material of the electrode 62 may be a general conductive material, and examples thereof include conductive carbon powders such as carbon black, carbon nanotubes, graphite, and graphene, metal powders such as silver, gold, copper, nickel, rhodium, palladium, chromium, titanium, platinum, iron, and alloys thereof, metal colloids such as colloidal silver, charge transfer complexes such as tetrathiafulvalene / tetracyanoquinodimethane, and conductive polymers such as polypyrrole and polythiophene. A member having elasticity that allows it to conform to the expansion of the dielectric used is preferred.

[0199] Examples of such electrode members include composite materials formed from the above-mentioned conductive materials and binders. Examples include composite materials in which conductive material fillers are dispersed in acrylic, silicone, urethane, or styrene elastomeric materials, or silicone grease, and poly(3,4-ethylenedioxythiophene) poly(4-styrenesulfonic acid) (PEDOT / PSS) aqueous dispersions containing appropriate amounts of organic solvents, resins, or crosslinking agents.

[0200] The method for manufacturing the converter according to the present disclosure is not particularly limited, and examples thereof include a method for spraying an electrode material onto a dielectric according to the present disclosure, a method for bonding an electrode material and a dielectric, a method for impregnating or dispersing the dielectric into the electrode material, and a method for applying or printing the electrode material onto the dielectric.

[0201] When the dielectric of the present disclosure having excellent dielectric properties and having a combination of low hysteresis loss and softness is used as a dielectric of a converter, an actuator that is excellent in terms of increased deformation, increased output, high efficiency, stable driving, and low voltage driving can be realized. In addition, in sensor applications, a sensor that is excellent in terms of high efficiency, high capacity, miniaturization, and recovery from deformation can be provided. Similarly, when the converter is used as a power generation element, an element that is excellent in terms of high efficiency, high output, miniaturization, and increased power generation can be provided.

[0202] In addition, as described above, when the dielectric according to the present disclosure includes a matrix including a polycarbonate structure represented by formula (2), in addition to the above-mentioned properties, it has resistance to dielectric breakdown, wear resistance, and low friction properties. Therefore, when the converter is used, dielectric breakdown due to the application of a high electric field can be minimized, energy loss due to friction with surrounding components can be reduced, and performance degradation due to wear can also be minimized.

[0203] [Example]

[0204] Embodiments of the present disclosure are described below, but the present disclosure is not limited to these embodiments.

[0205] <Materials used>

[0206] Materials used in Examples and Comparative Examples are listed below.

[0207] [Polyol]

[0208] ·A-1: Polyether diol (polypropylene glycol) [Product name: PREMINOL S4013F, R 1 Carbon number = 3 (branched), Mn = 12,000, hydroxyl value: 9.4 mg KOH / g, commercially available from AGC]

[0209] ·A-2: Polyether diol (polypropylene glycol) [Product name: Uniol D-2000, R 1 Carbon number = 3 (branched), Mn = 2,000, hydroxyl value: 55.0 mg KOH / g, commercially available from NOF Corporation]

[0210] ·A-3: Polyether diol (polytetramethylene glycol) [Product name: PTMG4000, R 1 Carbon number = 4 (straight chain), Mn = 4,000, hydroxyl value: 29.1 mg KOH / g, commercially available from Mitsubishi Chemical Corporation]

[0211] A-4: Polycarbonate diol [Product name: Kuraray Polyol C-2090, commercially available from Kuraray Co., Ltd., R 2 The number of carbon atoms is 6 (linear) + 6 (branched), Mn = 2,000, commercially available from Kuraray Co., Ltd.] A-5: polycarbonate diol [product name: Duranol T6002, R 2 Carbon number = 6 (straight chain), Mn = 1,900, hydroxyl value: 57.6 mg KOH / g, commercially available from Asahi Kasei Chemicals Corporation]

[0212] Regarding the number of carbon atoms in the polycarbonate diol, for example, 6 (straight chain) + 6 (branched chain) indicates that R 2 A straight chain structure having 6 carbon atoms and a branched chain structure having 6 carbon atoms are included.

[0213] [Polyisocyanate]

[0214] · B-1: xylylene diisocyanate [commercially available from Tokyo Chemical Industry Co., Ltd.]

[0215] B-2: Polymer MDI [Product name: Millionate MR-200, commercially available from Tosoh Corporation]

[0216] [Curing catalyst]

[0217] · C-1: 1,4-diazabicyclo[2.2.2]octane-2-methanol (product name: RZETA) [commercially available from Tosoh Corporation]

[0218] C-2: Dibutyltin dilaurate [commercially available from Tokyo Chemical Industry Co., Ltd.]

[0219] [Ionic Liquids]

[0220] · E-1: 1,3-bis(2-hydroxyethyl)imidazolium bis(trifluoromethanesulfonyl)imide (synthesized by the method disclosed in Japanese Patent Application Publication No. 2021-113853)

[0221] ·E-2: N,N-(2-hydroxyethyl)-N-(9-octadecene)-N-methylammonium bis(trifluoromethanesulfonyl)imide

[0222] E-3: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (product name: EMITFSI, commercially available from Sigma-Aldrich)

[0223] ·E-4: 1-(Hydroxypropyl)propylbis(trifluoromethanesulfonyl)imide

[0224] <Evaluation>

[0225] Hereinafter, the evaluation methods in Examples and Comparative Examples are as follows.

[0226] [Evaluation 1: Confirmation and analysis of matrix and domain]

[0227] Ultrathin sections (500 μm×500 μm×5 μm) were prepared from the dielectric using a cryosection system (product name: EM FC6, commercially available from Leica Microsystems) and an ultramicrotome (product name: EMUC6, commercially available from Leica Microsystems). Sections were prepared at a total of three locations: the center of the dielectric and two locations sufficiently away from the center.

[0228] The prepared sections were subjected to mapping measurements using an infrared microscope and imaging system (product names: Spectrum 400 (analysis device) and Spotlight 400 (scanning device), commercially available from PerkinElmer) to generate mapping images. For the measurement, mapping measurements were performed using an ATR imaging accessory under the following conditions: pixel size: 1.56 μm, resolution: 16 cm -1 , field of view: 300 μm × 300 μm, and scanning speed: 1.0 cm / s. The mapping image is an image of the size of the integral value of the infrared absorption spectrum for each pixel.

[0229] The presence of the matrix mapped as the continuous phase and the domain mapped as the discontinuous phase is confirmed from the obtained mapping image. In addition, it is confirmed from the infrared absorption spectrum of the matrix of the mapping image that the matrix contains the second structure (for example, corresponding to the structure of polycarbonate diol). In addition, it is confirmed from the infrared absorption spectrum of the domain of the mapping image that the domain contains the first structure (for example, corresponding to the structure of polypropylene glycol). That is, it is confirmed that the matrix contains the carbonate structure represented by formula (2), and the domain contains the ether structure represented by formula (1).

[0230] [Evaluation 2: Evaluation of parameters representing viscoelastic terms]

[0231] Ultrathin sections were prepared in the same manner as in Evaluation 1.

[0232] A total of 3 sections were prepared, an arbitrary observation area of ​​50 μm square was selected, and viscoelastic images were observed in a total of 3 observation areas. The viscoelastic images were measured in a total of three observation areas using a scanning probe microscope (product name: S-Image, commercially available from SII NanoTechnology Inc.).

[0233] The measurement mode for the viscoelastic image was VE-DFM. In addition, as a cantilever, "SI-DF3" (product name, commercially available from Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m) was used. In addition, the scanning frequency was 0.5 Hz.

[0234] From the obtained viscoelastic image, in each observation area, the parameters representing the viscoelastic term are calculated for 10 points each of the matrix and the domain, and the parameter A (mV) representing the viscoelastic term of the domain and the parameter B (mV) representing the viscoelastic term of the matrix are calculated from their arithmetic mean.

[0235] Here, it was confirmed from the viscoelastic images taken by SPM that the domains were exposed in the cross section and that the matrix was exposed in the cross section.

[0236] [Evaluation 3 and 4: Evaluation of the concentrations D / C and D3 / D of the ionic liquid]

[0237] Ultrathin sections were prepared in the same manner as in Evaluation 1.

[0238] An arbitrary observation area of ​​50 μm square was selected from the cross section of the slice, and the distribution of the ionic liquid was evaluated using a time-of-flight secondary ion mass spectrometer (TOF-SIMS). The apparatus, measurement conditions, and analysis method used are shown below.

[0239] Measuring device: nanoTOF II (product name, commercially available from ULVAC-PHI, Inc.)

[0240] Primary ion type: Bi 3++

[0241] Accelerating voltage: 30 kV

[0242] Primary ion current: 0.05pA

[0243] Repetition frequency: 8.2kHz

[0244] Raster mode: Unbunch

[0245] Grating size: 50μm×50μm

[0246] Measurement mode: Positive

[0247] Neutralizing electron gun: Not used

[0248] Measurement time: 360 seconds

[0249] Pixel size: 256×256

[0250] Sample pretreatment: acceleration voltage 10 kV, current 17.2 nA, grating size 400 × 400 μm, sputtering time 48 seconds

[0251] In each of the 256×256 pixels corresponding to the 50 μm×50 μm observation area, the anion having a molecular weight corresponding to the ionic liquid (for example, the bis(trifluoromethanesulfonyl)imide anion (TFSI)) observed under the above measurement conditions is plotted. - ), the counts of fragment ions with a mass number of 280) were regarded as the brightness of each pixel, and then the brightness was converted to 256 grayscale to obtain a monochrome image.

[0252] The obtained monochrome images were smoothed and binarized using image processing software (ImageJ) to separate the matrix (brightness of 255) and the domain (brightness of 0). As a filter for smoothing, a median filter with a kernel size of 3×3 was used. The threshold for binarization was determined from the brightness distribution of the monochrome image based on the fuzzy binarization method of Huang described in Non-Patent Literature 2.

[0253] For the noise processing performed on the obtained binary image, when the number of pixels in the domain with a brightness of 0 is 0.05% or less of the total number of pixels, the domain is considered to be caused by noise and is covered with a brightness of 255. The outline of the matrix (brightness of 255) is extracted from the de-noised binary image obtained in this way, the area surrounded by the obtained outline is set as the selection range, and the average brightness of the monochrome image within the range is calculated and defined as the concentration D of the ionic liquid contained in the matrix. Next, the average brightness of the entire monochrome image is calculated and defined as the concentration C of the ionic liquid for each observation area.

[0254] Next, each domain (brightness of 0) of the denoised binary image is processed as follows. The domain is selected as the range (a1) and is enlarged by 1.2 times (a2) with the geometric center c1 fixed. The set difference a3 between the range a2 after enlargement and the range a1 before enlargement is taken to obtain the range selection of the vicinity of the domain. The union A3 of the vicinity of the domain obtained for each domain is taken, and the average brightness of the monochrome image in the range is calculated and defined as the concentration D3 of the ionic liquid near the interface of the domain in the matrix.

[0255] Here, when a3 contains a domain, it is not included in the calculation of A3. That is, A3 is a region in the matrix.

[0256] When measuring D / C and D3 / D, the arithmetic mean of the three observation areas was used.

[0257] [Evaluation 5: Evaluation of relative dielectric constant]

[0258] The dielectric sample was cut to 1.5 cm×1.5 cm and inserted into a four-terminal sample holder (SH2-Z type, commercially available from Toyo Corporation). Using an impedance analyzer (1260A, commercially available from Solartron) and a dielectric interface (1296A, commercially available from Solartron), a frequency sweep was performed at room temperature with an AC voltage of 0.1 Vpp and a frequency of 0.01 Hz to 1 MHz, and the relative dielectric constant ε at 100 Hz was measured. The arithmetic mean of 3 samples was used.

[0259] [Evaluation 6: Evaluation of dielectric breakdown strength]

[0260] The dielectric test piece was prepared in the same process as described in Evaluation 8 to be described below, and a DC voltage was applied in a range of 1 kV / mm to 20 kV / mm with a step of 1 kV using a withstand voltage tester (GPT-9903A, commercially available from Texio Technology Corporation) under room temperature conditions. The application mode included a 10-second RAMP cycle, and then the set voltage was maintained for 30 seconds. When a current exceeding 5 mA was detected during this application mode in the ARC mode OFF state, it was determined that dielectric breakdown occurred at the electric field strength, and the electric field strength in this step was determined as the dielectric breakdown strength. The arithmetic mean of three samples was used.

[0261] [Evaluation 7: Evaluation of Young's modulus]

[0262] Using a viscoelasticity measuring device (product name: Rheogel-E4000, commercially available from UBM), the measurement was performed as follows. A 5 mm × 30 mm dielectric test piece formed by a punch cutter was set in a tensile tester chuck, a sinusoidal strain with an amplitude of 1 mm was applied at room temperature, and the complex elastic modulus of 1 to 200 Hz was obtained. For this, the real component of 1 Hz was determined as the Young's modulus of the test piece. The arithmetic mean of three samples was used.

[0263] [Evaluation 8: Evaluation of hysteresis loss]

[0264] Using a viscoelasticity measuring device (product name: Rheogel-E4000, commercially available from UBM), the measurement was performed as follows. A 5 mm × 30 mm dielectric test piece formed by a punch cutter was set in the tensile tester chuck, and a stress-strain curve was obtained at room temperature under the conditions of a displacement of 9 mm, a displacement speed of 0.275 mm / sec, and a reciprocating displacement number of 5 times. Calculation was performed using the following formula from the obtained stress-strain curve. The arithmetic mean of three samples was used.

[0265] Hysteresis loss [%] = (1-(elastic deformation workload / total deformation workload)) × 100

[0266] [Evaluation 9: Evaluation of strain amount when electric field is applied]

[0267] The dielectric sample was cut to 1.5 cm × 4.5 cm using a commercially available cutter. The surface of the cut sample was modified using an excimer lamp light source (EX-miniL12530, commercially available from Hamamatsu Photonics KK), and then a conductive coating agent (Denatron SPS-801, commercially available from Nagase ChemteX Corporation) was applied to the 1.5 cm × 4.5 cm surface (both surfaces) in a size of 0.8 cm × 4.1 cm to a thickness of 100 μm, and then the sample was allowed to stand in an environment of 100° C. for 5 minutes, and the solvent contained in the conductive coating agent was evaporated to form an electrode.

[0268] Next, the obtained dielectric with electrodes was suspended in a manner that one side of 1.5 cm was fixed and the other side of 4.5 cm was in the vertical direction. A withstand voltage tester (GPT-9903A, commercially available from Texio Technology Corporation) was used as a voltage source, and an electric field of 8 kv / mm was applied between the electrodes facing each other. In this case, a small laser displacement sensor (HL-G108-SJ, commercially available from Panasonic Corporation) was used to obtain the displacement amount Δd in the normal direction of the 1.5 cm × 4.5 cm surface before the electric field was applied, which was the 1.5 cm side facing the fixed side. The strain amount was calculated from the obtained Δd using the following formula.

[0269] Strain [%] = (Δd [cm] / 4.5 [cm]) × 100

[0270] [Evaluation 10 and 11: Arithmetic mean of circle-equivalent diameters of domains (average diameter), and evaluation of area ratio]

[0271] Each of the three viscoelastic images obtained in Evaluation 2 was converted into a 256-grayscale grayscale image using image processing software (product name: ImageProPlus, commercially available from Media Cybernetics, Inc.), and then binarized to obtain a binarized image for analysis. The threshold for binarization was determined from the monochrome image brightness distribution based on the Otsu's algorithm described in Non-Patent Document 3.

[0272] From the binary image obtained, the area of ​​the domain is calculated using the counting function of the image processing software. However, in the domain determined by the counting function, the domain with a cross-sectional area of ​​less than 0.05 area% in the observation area of ​​50 μm square is regarded as noise and removed from the data. The area corresponding to the matrix is ​​calculated by subtracting the obtained area from the total area of ​​the observation area. The area ratio (matrix / domain) is calculated from these areas.

[0273] In addition, the binarized image was subjected to morphological transformation, and the contour corresponding to the domain-matrix interface was extracted. In the morphological transformation, an image was generated by dilating a binarized image with a kernel size of 3×3, an image was generated by contracting a binarized image with the same kernel size, and the difference between them was obtained as a transformed image. From the obtained contour, a circle was detected using Hough transformation, and the circle equivalent diameter of the domain was calculated from the diameter of the detected circle. The arithmetic mean of all domains in the observation area was used.

[0274] [Evaluation 12 and 13: Measurement of circularity and number of domains]

[0275] The circularity of the domains was calculated using the counting function of the image software from the de-noised binarized images obtained in Evaluations 10 and 11. Then, among the domains in the observation area, the number of domains having a circularity of 0.60 to 0.95 was counted, and the ratio (%) of the number to the total number of domains in the observation area was calculated.

[0276] [Evaluation 14: tanδ peak temperature due to glass transition]

[0277] Using a viscoelasticity measuring device (product name: Physica MCR302, commercially available from Anton Paar), the measurement was performed as follows. A test piece formed by a punch cutter having a thickness of 2 mm and a width of 5 mm was set, and the viscoelasticity was measured in a torsion mode (twist) at a frequency of 1 Hz from -85°C to 20°C at a heating rate of 2°C / min within a length of 20 mm, and a temperature-tan δ curve was obtained.

[0278] [Example 1]

[0279] <Preparation of urethane prepolymer UP1-1>

[0280] 31.2 parts by mass of polyol A-1, 0.3 parts by mass of polyisocyanate B-1, and 1,000 ppm of curing catalyst C-1 were uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal (a first urethane prepolymer). 58.0 parts by mass of polyol A-2 were mixed into the polyol, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP1-1 (a second urethane prepolymer) (step (i) and step (ii)).

[0281] Here, in the following Examples and Comparative Examples, the amount of the curing catalyst C-1 is expressed in ppm by mass based on the mass of all materials used in the dielectric.

[0282] <Synthesis of Dielectric No. 1>

[0283] 89.5 parts by mass of the urethane prepolymer UP1-1 and 2.0 parts by mass of the ionic liquid E-1 were mixed, and the mixture was stirred at an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) until it became homogeneous to obtain a urethane prepolymer UP1-2 containing an ionic liquid (step (iii)).

[0284] 91.5 parts by mass of UP1-2, 3.2 parts by mass of polyisocyanate B-1, and 5.3 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred for about 1 to 2 minutes using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a dielectric forming mixture.

[0285] Next, the dielectric-forming mixture was inserted between release films having an interval of 100 μm, and cured by heating at a temperature of 130° C. for 2 hours (step (iv)). Next, the cured product was peeled off from the film, and post-cured at a temperature of 80° C. for 3 days to obtain a sheet-shaped dielectric No. 1 having a thickness of 100 μm.

[0286] [Example 2]

[0287] <Preparation of urethane prepolymer UP2-1>

[0288] 31.3 parts by mass of polyol A-1,

[0289] 0.2 parts by mass of polyisocyanate B-1, and

[0290] 1,000 ppm of the curing catalyst C-1 was uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal.

[0291] 58.1 parts by mass of Polyol A-4 were mixed therein, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP2-1.

[0292] <Synthesis of Dielectric No. 2>

[0293] 89.6 parts by mass of urethane prepolymer UP2-1, and

[0294] 2.0 parts by mass of ionic liquid E-2 were mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a urethane prepolymer UP2-2 containing an ionic liquid.

[0295] 91.6 parts by mass of UP2-2,

[0296] 3.0 parts by mass of polyisocyanate B-1, and

[0297] 5.4 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm for about 1 to 2 minutes until it became homogeneous to obtain a dielectric-forming mixture.

[0298] Next, a dielectric No. 2 was obtained in the same manner as in Example 1 except that this dielectric-forming mixture was used.

[0299] [Example 3]

[0300] <Preparation of urethane prepolymer UP3-1>

[0301] 31.2 parts by mass of polyol A-1,

[0302] 0.5 parts by mass of polyisocyanate B-1, and

[0303] 1,000 ppm of the curing catalyst C-1 was uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal.

[0304] 58.7 parts by mass of Polyol A-4 were mixed therein, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP3-1.

[0305] <Synthesis of Dielectric No. 3>

[0306] 91.4 parts by mass of urethane prepolymer UP3-1, and

[0307] 1.0 parts by mass of ionic liquid E-3 was mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a urethane prepolymer UP3-2 containing an ionic liquid.

[0308] 92.4 parts by mass of UP3-2,

[0309] 2.2 parts by mass of polyisocyanate B-1, and

[0310] 5.4 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred for about 1 to 2 minutes under the condition of an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) until it became homogeneous to obtain a dielectric-forming mixture. Next, a dielectric No. 3 was obtained in the same manner as in Example 1 except that this dielectric-forming mixture was used.

[0311] [Example 4]

[0312] <Preparation of urethane prepolymer UP4-1>

[0313] 31.4 parts by mass of polyol A-1,

[0314] 0.5 parts by mass of polyisocyanate B-1, and

[0315] 1,000 ppm of the curing catalyst C-1 was uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal.

[0316] 58.3 parts by mass of Polyol A-4 were mixed therein, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP4-1.

[0317] <Synthesis of Dielectric No. 4>

[0318] 90.2 parts by mass of urethane prepolymer UP4-1, and

[0319] 1.8 parts by mass of ionic liquid E-4 was mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a urethane prepolymer UP4-2 containing an ionic liquid.

[0320] 92.0 parts by mass of UP4-2,

[0321] 2.6 parts by mass of polyisocyanate B-1, and

[0322] 5.4 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred for about 1 to 2 minutes under the condition of an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) until it became homogeneous to obtain a dielectric-forming mixture. Next, a dielectric No. 4 was obtained in the same manner as in Example 1 except that this dielectric-forming mixture was used.

[0323] [Example 5]

[0324] <Preparation of Urethane Prepolymer UP5-1>

[0325] 30.4 parts by mass of polyol A-2,

[0326] 2.8 parts by mass of polyisocyanate B-1, and

[0327] 1,000 ppm of the curing catalyst C-1 was uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal.

[0328] 56.6 parts by mass of Polyol A-4 were mixed therein, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP5-1.

[0329] <Synthesis of Dielectric No. 5>

[0330] 89.8 parts by mass of urethane prepolymer UP5-1, and

[0331] 2.0 parts by mass of ionic liquid E-1 was mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a urethane prepolymer UP5-2 containing an ionic liquid.

[0332] 91.8 parts by mass of UP5-2,

[0333] 2.8 parts by mass of polyisocyanate B-1, and

[0334] 5.4 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred for about 1 to 2 minutes under the condition of an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) until it became homogeneous to obtain a dielectric-forming mixture. Next, a dielectric No. 5 was obtained in the same manner as in Example 1 except that this dielectric-forming mixture was used.

[0335] [Example 6]

[0336] <Preparation of urethane prepolymer UP6-1>

[0337] 31.0 parts by mass of polyol A-3,

[0338] 1.4 parts by mass of polyisocyanate B-1, and

[0339] 1,000 ppm of the curing catalyst C-1 was uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal.

[0340] 57.4 parts by mass of Polyol A-4 were mixed therein, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP6-1.

[0341] <Synthesis of Dielectric No. 6>

[0342] 89.8 parts by mass of urethane prepolymer UP6-1, and

[0343] 2.0 parts by mass of ionic liquid E-1 were mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a urethane prepolymer UP6-2 containing an ionic liquid.

[0344] 91.8 parts by mass of UP6-2,

[0345] 2.8 parts by mass of polyisocyanate B-1, and

[0346] 5.4 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred for about 1 to 2 minutes under the condition of an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) until it became homogeneous to obtain a dielectric-forming mixture. Next, a dielectric No. 6 was obtained in the same manner as in Example 1 except that this dielectric-forming mixture was used.

[0347] [Example 7]

[0348] <Preparation of Urethane Prepolymer UP7-1>

[0349] 31.1 parts by mass of polyol A-1,

[0350] 0.5 parts by mass of polyisocyanate B-1, and

[0351] 1,000 ppm of the curing catalyst C-1 was uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal.

[0352] 58.0 parts by mass of Polyol A-5 were mixed therein, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP7-1.

[0353] <Synthesis of Dielectric No. 7>

[0354] 89.6 parts by mass of urethane prepolymer UP7-1, and

[0355] 2.0 parts by mass of ionic liquid E-1 was mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a urethane prepolymer UP7-2 containing an ionic liquid.

[0356] 91.6 parts by mass of UP7-2,

[0357] 3.0 parts by mass of polyisocyanate B-1, and

[0358] 5.4 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred for about 1 to 2 minutes under the condition of an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) until it became homogeneous to obtain a dielectric-forming mixture. Next, a dielectric No. 7 was obtained in the same manner as in Example 1 except that this dielectric-forming mixture was used.

[0359] [Example 8]

[0360] <Preparation of urethane prepolymer UP8-1>

[0361] 40.5 parts by mass of polyol A-1,

[0362] 0.6 parts by mass of polyisocyanate B-1, and

[0363] 1,000 ppm of the curing catalyst C-1 was uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal.

[0364] 49.4 parts by mass of Polyol A-4 were mixed therein, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP8-1.

[0365] <Synthesis of Dielectric No. 8>

[0366] 90.5 parts by mass of urethane prepolymer UP8-1, and

[0367] 2.0 parts by mass of ionic liquid E-1 was mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a urethane prepolymer UP8-2 containing an ionic liquid.

[0368] 92.5 parts by mass of UP8-2,

[0369] 2.1 parts by mass of polyisocyanate B-1, and

[0370] 5.4 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred for about 1 to 2 minutes under the condition of an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) until it became homogeneous to obtain a dielectric-forming mixture. Next, a dielectric No. 8 was obtained in the same manner as in Example 1 except that this dielectric-forming mixture was used.

[0371] [Example 9]

[0372] <Preparation of Urethane Prepolymer UP9-1>

[0373] 40.1 parts by mass of polyol A-1,

[0374] 0.7 parts by mass of polyisocyanate B-1, and

[0375] 1,000 ppm of curing catalyst C-1 was uniformly mixed, and the mixture was heated at a temperature of 100° C. for 24 hours to synthesize a polyol having an isocyanate group at the terminal. 50.4 parts by mass of polyol A-4 was mixed therein, and the mixture was heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP9-1.

[0376] <Synthesis of Dielectric No. 9>

[0377] 91.2 parts by mass of urethane prepolymer UP9-1, and

[0378] 2.0 parts by mass of ionic liquid E-3 were mixed, and the mixture was stirred using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) at an orbital speed of 1,600 rpm until it became homogeneous to obtain a urethane prepolymer UP9-2 containing an ionic liquid.

[0379] 93.2 parts by mass of UP9-2,

[0380] 1.4 parts by mass of polyisocyanate B-1, and

[0381] 5.4 parts by mass of polyisocyanate B-2 were mixed, and the mixture was stirred for about 1 to 2 minutes under the condition of an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer (product name: V-mini300, commercially available from EME Corporation) until it became homogeneous to obtain a dielectric-forming mixture. Next, dielectric No. 9 was obtained in the same manner as in Example 1 except that this dielectric-forming mixture was used.

[0382] [Comparative Example 1]

[0383] 89.4 parts by mass of polyol A-4,

[0384] 5.2 parts by mass of polyisocyanate B-1,

[0385] 5.4 parts by mass of polyisocyanate B-2, and

[0386] 1,000 ppm of curing catalyst C-1 was mixed, and the mixture was stirred for 2 minutes at an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer until it became homogeneous to obtain a dielectric forming mixture. Next, a polyurethane elastomer No. C1 was obtained in the same manner as in Example 1 except that this dielectric forming mixture was used.

[0387] [Comparative Example 2]

[0388] 97.2 parts by mass of polyol A-1,

[0389] 2.8 parts by mass of polyisocyanate B-2, and

[0390] 250 ppm of curing catalyst C-2 was mixed, and the mixture was stirred for 2 minutes under the condition of an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer until it became homogeneous to obtain a dielectric forming mixture. Next, a polyurethane elastomer No. C2 was obtained in the same manner as in Example 1 except that this dielectric forming mixture was used.

[0391] [Comparative Example 3]

[0392] 87.1 parts by mass of polyol A-4, and

[0393] 1.8 parts by mass of the ionic liquid E-1 were mixed, and the mixture was stirred for 10 minutes using a self-rotating vacuum stirring and defoaming mixer under the condition of an orbital speed of 1,600 rpm until it became homogeneous to obtain a mixture containing the ionic liquid.

[0394] 88.9 parts by mass of the obtained mixture,

[0395] 5.7 parts by mass of polyisocyanate B-1,

[0396] 5.4 parts by mass of polyisocyanate B-2, and

[0397] 1,000 ppm of curing catalyst C-1 was mixed, and the mixture was stirred for 2 minutes at an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer until it became homogeneous to obtain a dielectric forming mixture. Next, a polyurethane elastomer No. C3 was obtained in the same manner as in Example 1 except that this dielectric forming mixture was used.

[0398] [Comparative Example 4]

[0399] 94.1 parts by mass of polyol A-1, and

[0400] 2.0 parts by mass of the ionic liquid E-1 were mixed, and the mixture was stirred for 10 minutes using a self-rotating vacuum stirring and defoaming mixer under the condition of an orbital speed of 1,600 rpm until it became homogeneous to obtain a mixture containing the ionic liquid.

[0401] 96.1 parts by mass of the obtained mixture,

[0402] 3.9 parts by mass of polyisocyanate B-2, and

[0403] 250 ppm of curing catalyst C-2 was mixed, and the mixture was stirred for 2 minutes at an orbital speed of 1,600 rpm using a self-rotating vacuum stirring and defoaming mixer until it became homogeneous to obtain a dielectric forming mixture. Next, a polyurethane elastomer No. C4 was obtained in the same manner as in Example 1 except that this dielectric forming mixture was used.

[0404] The results of Evaluations 1 to 14 of Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Tables 1 and 2.

[0405] <Structure of dielectric>

[0406] Regarding the results of Evaluation 1, clear phase separation between the matrix and the domain was observed in the dielectrics No. 1 to 9 according to Examples 1 to 9. In addition, it was confirmed that the matrix contained a polyurethane including a structure (second structure) derived from polycarbonate, and the domain contained a structure (first structure) derived from polyether. In addition, regarding the results of Evaluation 2, in the dielectrics No. 1 to 9, the relationship between the parameter A representing the viscoelastic term of the domain and the parameter B representing the viscoelastic term of the matrix satisfied A. <B。

[0407] Regarding the results of evaluation 3, Figure 2 An image visualized using time-of-flight secondary ion mass spectrometry (TOF-SIMS) of the distribution of the ionic liquid in the cross section of polyurethane elastomer No. 1 is shown. Based on the results, a clear matrix-domain phase separation structure was confirmed, and furthermore, the ionic liquid was mainly distributed in the matrix.

[0408] In addition, in the dielectrics according to Examples 1 to 9, it was confirmed that the relationship between the concentration C of the ionic liquid per unit cross-sectional area and the concentration D of the ionic liquid contained in the matrix per unit cross-sectional area satisfied D / C>1.0.

[0409] In addition, in the dielectrics according to Examples 1 to 9, since the concentration D3 of the ionic liquid in the vicinity of the domain and the concentration D of the ionic liquid contained in the matrix satisfy D3 / D>1.0, the main distribution of the ionic liquid on the matrix side near the interface between the matrix and the domain is clear.

[0410] Regarding the results of evaluation 14, Figure 3 Representative temperature-tan δ curves obtained by viscoelasticity measurements (Examples 1 and 2 and Comparative Example 1) are shown. Figure 3 As shown, in Examples 1 and 2, two tan δ peak temperatures (glass transition temperatures) were confirmed in the range of -80 to 10°C, whereas in Comparative Example 1, only one peak temperature was confirmed.

[0411] In addition, in Examples 3 to 9, two glass transition temperatures were confirmed, as in Examples 1 and 2.

[0412] In addition, in the dielectrics No. 1 to 9 according to Examples 1 to 9, the appearance of the dielectrics was opaque. On the other hand, the dielectrics No. C1 to C4 according to Comparative Examples 1 to 4 had high transparency.

[0413] The tan δ peak temperatures observed in dielectric No. 1 and dielectric No. 2 according to Examples 1 and 2 are -67°C and -18°C, which correspond to the glass transition temperatures of the polyether polyurethane derived from raw material A-1 (polypropylene glycol) and the polycarbonate polyurethane derived from raw material A-4 (polycarbonate polyol) (reference to Comparative Example 1). That is, it can be clearly understood that in dielectric No. 1 and 2 obtained in Examples 1 and 2, the polyurethane containing polycarbonate and the polyurethane containing polyether are almost incompatible with each other, and there is clear phase separation.

[0414] In addition, similarly, in Examples 3 to 9, two glass transition temperatures corresponding to the glass transition temperatures of the polyurethane containing polycarbonate and the polyurethane containing polyether were confirmed.

[0415] On the other hand, in the dielectric Nos. C1 to C4 obtained in Comparative Examples 1 to 4, the absence of a phase separation structure was confirmed in the cross-sectional image observations in Evaluations 1 to 3, and 9 to 12. In addition, as described above, tan δ observed in Comparative Example 1 showed a single peak, and from this result, it was confirmed that there was no phase separation structure. This tendency was also observed in Comparative Examples 2 to 4.

[0416] <Evaluation Results of Dielectric Materials>

[0417] The dielectrics No. 1 to 9 according to Examples 1 to 9 had lower Young's modulus and better low hysteresis loss characteristics than the single polycarbonate polyurethane No. C1 obtained in Comparative Example 1. In addition, a significant increase in relative dielectric constant was observed, and a significant difference was observed in the amount of strain when an electric field was applied.

[0418] In addition, in Comparative Example 3 obtained by adding the ionic liquid to Comparative Example 1, no increase in dielectric constant was observed as in Examples 1 to 9. In addition, Examples 1 to 9 all had resistance to dielectric breakdown equal to or higher than that of Comparative Example 3.

[0419] Single polyether polyurethane No. C2 obtained in Comparative Example 2 had a low Young's modulus, but had a high hysteresis loss, and did not achieve the same high level of increase in relative dielectric constant as in Examples 1 and 2.

[0420] In Comparative Example 4 obtained by adding the ionic liquid to Comparative Example 2, a significant increase in the relative dielectric constant was observed, but the same level of low hysteresis loss as in Examples 1 to 9 could not be achieved.

[0421] It was confirmed that all Examples 1 to 9 had sufficient dielectric breakdown strength, but particularly in Examples 1 and 2 and Examples 4 to 8 using an ionic liquid having a reactive functional group reactive with an isocyanate group, good dielectric breakdown strength exceeding 20 kV / mm was obtained.

[0422] All of Examples 1 to 9 have excellent relative dielectric constants, but in particular, in which R 1 In Examples 1 to 5 and Examples 7 to 9 which are alkylene groups having a branched structure and having 3 to 5 carbon atoms, good relative dielectric constants were obtained.

[0423] Based on the above evaluation results, it can be clearly understood that the dielectric according to the present disclosure has excellent dielectric characteristics and has low hysteresis loss and flexibility in combination, and is suitable as a dielectric for use in a converter or the like.

[0424] [Table 1]

[0425]

[0426] [Table 2]

[0427] Table 2

[0428]

[0429] The present disclosure is not limited to the embodiments, and various changes and modifications can be made without departing from the spirit and scope of the present disclosure. Therefore, in order to disclose the scope of the present disclosure, the following claims are attached.

[0430] This application claims priority from Japanese Patent Application No. 2022-170649 filed on October 25, 2022 and Japanese Patent Application No. 2023-177083 filed on October 12, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A dielectric, wherein the dielectric comprises a polyurethane elastomer and an ionic liquid in the polyurethane elastomer, The polyurethane elastomer comprises a matrix and domains dispersed in the matrix, and The domain comprises a first structure represented by the following formula (1): In formula (1), R 1 It represents an alkylene group having 3 to 6 carbon atoms.

2. The dielectric according to claim 1, wherein the ionic liquid is present in the matrix.

3. The dielectric according to claim 2, The ionic liquid is mainly distributed in the matrix near the interface between the matrix and the domain.

4. The dielectric according to any one of claims 1 to 3, in, In a viscoelastic image measured by a scanning probe microscope of a cross section of a dielectric in which the domain and the matrix are exposed, a relationship between a parameter A representing a viscoelastic term of the domain and a parameter B representing a viscoelastic term of the matrix satisfies A. <B。 5. The dielectric according to claim 2 or 3, in, The concentration of the ionic liquid per 50 μm×50 μm observation area observed in the cross-section in which the domain and the matrix of the dielectric are exposed is defined as concentration C, and the concentration of the ionic liquid contained in the matrix in the observation area is defined as concentration D, and the ratio D / C of the concentration D to the concentration C satisfies D / C>1.

0.

6. The dielectric according to any one of claims 1 to 5, wherein an area ratio of the matrix to the domain (matrix / domain) observed in a 50 μm×50 μm observation area in a cross section in which the domain and matrix of the dielectric are exposed is 50.0 / 50.0 to 85.0 / 15.

0.

7. The dielectric according to any one of claims 1 to 6, The ionic liquid has a reactive functional group that reacts with an isocyanate group.

8. The dielectric according to any one of claims 1 to 7, The ionic liquid is at least one ionic liquid selected from the group consisting of ammonium-based ionic liquids and imidazolium-based ionic liquids.

9. The dielectric according to any one of claims 1 to 8, The anion of the ionic liquid is selected from BF 4 - PF 6 - CF 3 SO 3 - and (CF 3 SO 2 ) 2 N - At least one anion of the group consisting of.

10. The dielectric according to any one of claims 1 to 9, The content of the ionic liquid in the dielectric is 0.5 to 8.0 mass %.

11. The dielectric according to any one of claims 1 to 10, The matrix comprises a structure represented by the following formula (2): In formula (2), R 2 It represents an alkylene group having 3 to 12 carbon atoms.

12. The dielectric according to any one of claims 1 to 11, Where R 1 It is an alkylene group having a branched structure having 3 to 5 carbon atoms.

13. The dielectric according to claim 11, Where R 2 It is an alkylene group having 3 to 9 carbon atoms.

14. The dielectric according to any one of claims 1 to 13, The arithmetic mean of circle-equivalent diameters of domains observed in a cross section in which the domains and the matrix are exposed of the dielectric is 0.2 to 30.0 μm.

15. The dielectric according to any one of claims 1 to 14, The relative dielectric constant of the dielectric is greater than 10.

0.

16. The dielectric according to any one of claims 1 to 15, The Young's modulus of the dielectric is 2.5 MPa or less.

17. The dielectric according to any one of claims 1 to 16, The hysteresis loss of the dielectric is less than 10%.

18. The dielectric according to any one of claims 1 to 17, The dielectric breakdown strength of the dielectric is above 15 kV / mm.

19. A method for manufacturing a dielectric according to any one of claims 1 to 18, wherein include: (i) a step of obtaining a second urethane prepolymer having at least two hydroxyl groups by reacting a first urethane prepolymer having at least one isocyanate group with a first polycarbonate polyol having at least two hydroxyl groups; (ii) a step of obtaining a first dispersion by dispersing droplets comprising at least a portion of the second urethane prepolymer in a second polycarbonate polyol; (iii) a step of obtaining a second dispersion by dispersing an ionic liquid in the first dispersion; and (iv) a step of preparing a dielectric-forming mixture comprising the second dispersion and a polyisocyanate having at least two isocyanate groups, and then reacting the second urethane prepolymer, the second polycarbonate polyol, and the polyisocyanate in the dielectric-forming mixture to form the dielectric.

20. A converter, include: at least two electrodes; and A dielectric according to any one of claims 1 to 18 interposed between the electrodes.

21. The converter according to claim 20, wherein the converter is an actuator, a sensor, or a power generating element.

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