Resin composition, polymer composite piezoelectric material, polymer composite piezoelectric element, sensor device, and ink

Abstract

To provide a resin composition which improves piezoelectric characteristics when being used as a polymer composite piezoelectric element.SOLUTION: A resin composition contains a piezoelectric inorganic compound (A), a polymer (B) and a conductive material (C), preferably contains at least one kind selected from the group consisting of metal, a metal oxide, carbon or a conductive resin as the conductive material (C), a blending ratio of the conductive material (C) in the resin composition is 0.01 to 10 vol.% with respect to the solid content total amount of the resin composition, and the piezoelectric inorganic compound (B) is a metal oxide which is represented by the following (formula 1) and contains niobium. Formula (1): NaxK1-xNbO3+y (0≤x<1 and -0.05≤y≤0.05).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a resin composition containing a piezoelectric inorganic compound and a polymer, a polymer composite piezoelectric material or ink containing the same, a polymer composite piezoelectric element using the resin composition, and the like.

Background Art

[0002] Ceramics such as lead zirconate titanate are excellent in piezoelectricity and can convert vibration and pressure into electrical signals, and conversely, convert electrical signals into vibration and strain. Due to this property, they are applied to sensors, actuators, power generation elements, acoustic devices, and the like. Recently, they have also been used in wearable devices worn on the body.

[0003] However, such piezoelectric ceramics are brittle materials and are vulnerable to physical shock and vibration. Also, due to their lack of flexibility, there are problems in processing into complex shapes and increasing the area. In addition, in consideration of the environment, the use of lead-free piezoelectric ceramics is required.

[0004] On the other hand, polymers such as resins have a relatively low density, are lightweight and flexible, and are easy to mold. Therefore, a polymer composite piezoelectric body that makes use of the characteristics of both piezoelectric ceramics and polymers and contains a piezoelectric ceramic as a filler in a polymer has been proposed (see, for example, Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0006] Conventional polymer composite piezoelectric materials can be endowed with flexibility and light weight in addition to piezoelectricity, and also have excellent moldability. However, the piezoelectricity is lower than that of piezoelectric ceramics alone, so there is room for improvement, such as increasing the piezoelectricity. The piezoelectricity of a polymer composite piezoelectric material is usually improved by increasing the packing ratio of piezoelectric ceramic particles. For this reason, Patent Document 2 discloses a composite piezoelectric material in which two types of particles, small potassium niobate particles with a D50 of 0.1 to 1.2 μm and large potassium niobate particles with a D50 of 1 to 15 μm, are kneaded into a polymer, and the small particles are allowed to enter the gaps between the large particles, thereby increasing the packing density in the polymer composite piezoelectric material. However, the piezoelectric constant of the composite piezoelectric material element is only about 5.75 pC / N, and it cannot be said that sufficient piezoelectricity is exhibited.

[0007] In Patent Document 3, since an increase in the filling rate leads to a decrease in the flexibility of the composite piezoelectric body, it can be said that the piezoelectric performance is efficiently improved without increasing the filling rate of the ceramic particles too much by using a filler with a high aspect ratio such as a fiber shape. However, the use of fibrous ceramics has problems such as a decrease in productivity and a rise in costs.

[0008] On the other hand, adding a conductive material to a piezoelectric body, which is an insulator, is usually thought to reduce the piezoelectricity due to a decrease in electrostatic charge. However, as a result of intensive research, the present inventor unexpectedly found that adding a conductive material to a composite of a piezoelectric inorganic compound and a polymer improves the piezoelectric properties, and developed a resin composition that can combine high levels of flexibility and piezoelectricity and contribute to productivity.

[0009] Therefore, an object of the present invention is to provide a resin composition having good piezoelectric properties when used as a polymer composite piezoelectric element, a polymer composite material or ink containing the same, a polymer composite piezoelectric element containing the resin composition, and a sensor device using the piezoelectric element. **Means for Solving the Problems**

[0010] The present invention has the aspects described in [1] to

[12] below.

[0011] [1]. A resin composition containing a piezoelectric inorganic compound (A), a polymer (B), and a conductive material (C).

[0012] [2]. The resin composition according to [1], wherein the piezoelectric inorganic compound (A) is a metal oxide containing niobium.

[0013] [3]. The resin composition according to [2], wherein the metal oxide containing niobium is a compound represented by the following (Formula 1).

[0014] Na x K 1-x NbO 3+y ···(Formula 1) (0 ≦ x < 1, -0.05 ≦ y ≦ 0.05)

[0015] [4]. The resin composition according to any one of [1] to [3], wherein the conductive material (C) contains at least one selected from the group consisting of metals, metal oxides, carbon, and conductive resins.

[0016] [5]. The resin composition according to any one of [1] to [4], wherein the blending ratio of the conductive material (C) in the resin composition is 0.01 to 10% by volume based on the total solid content of the resin composition.

[0017] [6]. The resin composition according to any one of [1] to [5], wherein the blending ratio of the piezoelectric inorganic compound (A) in the resin composition is 20 to 95% by volume based on the total solid content of the resin composition.

[0018] [7]. The resin composition according to any one of [1] to [6], comprising at least one resin selected from the group consisting of a polyimide resin, an epoxy resin, and an acrylic resin as the polymer (B).

[0019] [8]. A polymer composite piezoelectric material comprising the resin composition according to any one of [1] to [7].

[0020] [9]. A polymer composite piezoelectric element obtained by polarizing the resin composition according to any one of [1] to [7].

[0021]

[10] . A sensor device using the polymer composite piezoelectric element according to [9].

[0022]

[11] . An ink containing the resin composition according to any one of [1] to [7] and a solvent.

[0023]

[12] . A method for improving the piezoelectric constant d by blending a conductive material (C) into a resin composition containing a piezoelectric inorganic compound (A) and a polymer (B). 33 thereby improving it. [Advantages of the Invention]

[0024] The resin composition of the present invention has good piezoelectric properties when formed into a polymer composite piezoelectric element by blending a conductive material (C) into a piezoelectric inorganic compound (A) and a polymer (B). In particular, compared with a polymer composite piezoelectric having the same or approximate blending ratio of the piezoelectric inorganic compound (A) and the polymer (B), by blending the conductive material (C), the piezoelectric constant d 33 can be increased. [Brief Description of the Drawings]

[0025]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0026] Hereinafter, the present invention will be described based on one embodiment. However, the present invention is not limited to this embodiment.

[0027] <Resin Composition> The resin composition of one embodiment of the present invention (hereinafter, also referred to as the present resin composition) contains a piezoelectric inorganic compound (A), a polymer (B), and a conductive material (C).

[0028] <Piezoelectric Inorganic Compound (A)> The piezoelectric inorganic compound (A) of the present resin composition is not particularly limited as long as it is an inorganic compound having piezoelectricity. Note that piezoelectricity is a property of generating electric charges by stress or deforming by applying an electric field. Further, a lead-free material not containing lead is preferable from the viewpoints of environmental load and biocompatibility for application in the healthcare field. As the piezoelectric inorganic compound (A), ceramics are preferable. For example, metal oxides containing niobium, metal oxides containing titanium, zinc oxide, aluminum nitride, etc. can be mentioned, and mixtures or composite metal oxides of these may also be used.

[0029] Among these, metal oxides containing niobium or metal oxides containing titanium are preferable. Examples of the metal oxide containing niobium include alkali metal niobates such as potassium niobate, sodium niobate, lithium niobate, potassium sodium niobate, and potassium sodium lithium niobate. Examples of the metal oxide containing titanium include metal titanates such as barium titanate, lead zirconate titanate, bismuth sodium titanate, bismuth potassium titanate, and bismuth potassium sodium titanate. Among the metal oxides containing niobium, potassium niobate or potassium sodium niobate is preferred, and among the metal oxides containing titanium, barium titanate is preferred.

[0030] When potassium sodium niobate is used as the piezoelectric inorganic compound (A), it is preferably a compound represented by the following (Formula 1).

[0031] Na x K 1-x NbO 3+y ···(Formula 1) (0 ≦ x < 1, -0.05 ≦ y ≦ 0.05)

[0032] More preferably, the above x is 0.4 ≦ x ≦ 0.6, and particularly preferably 0.45 ≦ x ≦ 0.55. Particularly preferably, the above y is -0.01 ≦ y ≦ 0.01. When the above x and the above y are within this range, it becomes possible to impart an excellent piezoelectric constant.

[0033] As the piezoelectric inorganic compound (A), commercially available products can be used. Further, for example, potassium sodium niobate can also be produced by a solid-phase reaction method using sodium carbonate, potassium carbonate, and niobium oxide and appropriately adjusting the blending ratio.

[0034] The piezoelectric inorganic compound (A) may be in various forms such as particulate or fibrous. When the piezoelectric inorganic compound (A) is in particulate form, the average particle diameter (D50) is not particularly limited, but is preferably 100 nm or more and 2000 nm or less, more preferably 200 nm or more and 1000 nm or less, and particularly preferably 300 nm or more and 800 nm or less. The average particle diameter (D50) can be measured, for example, as the integrated 50% particle diameter determined by measuring the volume frequency particle size distribution by the laser light scattering method.

[0035] The piezoelectric inorganic compound (A) can be surface-treated in a range that does not impair its piezoelectricity in order to improve various properties such as water resistance, stability, and dispersibility. For surface treatment, coupling agents such as silane-based, titanate-based, aluminate-based, and zirconate-based, as well as surface treatment agents such as fatty acids, fatty acid esters, higher alcohols, and hardened oils can be used.

[0036] The surface treatment method is not particularly limited, and known methods can be used. For example, a wet method can be used in which the piezoelectric inorganic compound (A) and the surface treatment agent are dispersed in water or an organic solvent, followed by filtration and drying for surface treatment.

[0037] The blending ratio of the piezoelectric inorganic compound (A) in the present resin composition is preferably in the range of 20 to 95% by volume, more preferably 25 to 85% by volume, and particularly preferably 30 to 70% by volume with respect to the total solid content of the present resin composition.

[0038] <Polymer (B)> The polymer (B) of the present resin composition is not particularly limited, but those having excellent dispersibility of the piezoelectric inorganic compound (A) as the matrix of the present resin composition and capable of imparting flexibility when made into a polymer composite piezoelectric element or the like are preferred, and either a thermoplastic polymer or a thermosetting polymer may be used. Further, the polymer (B) does not necessarily have piezoelectricity itself, and those having no piezoelectricity are preferred because they do not cancel out the piezoelectricity generated by the piezoelectric inorganic compound (A).

[0039] Examples of the polymer (B) include synthetic resins (including thermoplastic elastomers) such as polyimide resin, epoxy resin, acrylic resin, ethylene-vinyl acetate copolymer (EVA) resin, polyvinyl chloride resin, polyurethane resin, acrylic urethane resin, ionomer resin, polyolefin resin, polypropylene resin, polyethylene resin, silicone resin, polyester resin, polystyrene resin, polyimide resin, polyamide resin, polysulfone resin, and polyethersulfone resin. These can be used alone or in combination of two or more kinds. Among these, as the polymer (B), any one kind of polyimide resin, epoxy resin, and acrylic resin or a mixture thereof is preferable, and a polyimide resin or an epoxy resin is particularly preferable. More specifically, examples of the polyimide resin include maleimide-terminated polyimide resin, and examples of the epoxy resin include bisphenol A type epoxy resin.

[0040] The blending ratio of the polymer (B) in the present resin composition is preferably in the range of 5 to 80% by volume, more preferably 15 to 75% by volume, and particularly preferably 30 to 70% by volume with respect to the total solid content of the present resin composition.

[0041] <Conductive material (C)> The conductive material (C) is not particularly limited as long as it is a material having conductivity, and examples thereof include metals, metal oxides, carbon, and conductive resins. These can be used alone or in combination of two or more kinds.

[0042] As the conductive material (C), more specifically, metals such as gold, silver, platinum, copper, and silicon; metal oxides such as tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), and mica coated with ATO, titanium oxide coated with ATO, titanium oxide coated with SnO2, potassium titanate coated with SnO2, etc.; carbon such as graphite, carbon black, ketjen black, carbon nanofiller, carbon nanotube, etc.; and conductive resins such as polyaniline-based, polypyrrole-based, polythiophene-based resins can be mentioned.

[0043] The conductive material (C) may be in various forms such as particulate, fibrous (including acicular), flaky, plate-like, etc. When the conductive material (C) is in particulate form, the average particle diameter (D50) is not particularly limited, but is preferably 100 nm or more and 1000 nm or less, more preferably 300 nm or more and 1000 nm or less, and particularly preferably 300 nm or more and 800 nm or less. The average particle diameter (D50) can be measured, for example, as the integrated 50% particle diameter obtained by measuring the volume frequency particle size distribution by the laser light scattering method.

[0044] Specific examples of the conductive material (C) include the filler "Dentole WK-200B" (manufactured by Otsuka Chemical Co., Ltd.) which is a product with tin oxide coated on the surface of potassium titanate fibers.

[0045] The blending ratio of the conductive material (C) in the present resin composition is preferably in the range of 0.01 to 10% by volume based on the total solid content of the present resin composition. Among them, the lower limit value is any one of 0.1, 0.5, 0.8, 0.9, 0.95, 1.0% by volume, and the upper limit value is more preferably any one of 5.0, 3.0, 2.9, 2.5, 2.0, 1.7, 1.5% by volume.

[0046] <Other components (D)> In addition to the piezoelectric inorganic compound (A), polymer (B), and conductive material (C), other components (D) may be blended within a range that does not affect the piezoelectricity of this resin composition. Examples of the other components (D) include curing agents, glass powders, coupling agents, polymer additives, reactive diluents, polymerization inhibitors, leveling agents, wetting improvers, surfactants, plasticizers, ultraviolet absorbers, antioxidants, inorganic fillers, fungicides, humidity regulators, dye solvents, buffers, chelating agents, flame retardants, silane coupling agents, and the like.

[0047] The blending ratio of the other components (D) in this resin composition is preferably 5% by volume or less, more preferably 4% by volume or less, and particularly preferably 2.5% by volume or less, based on the total solid content of this resin composition.

[0048] <Form of this resin composition> This resin composition may be in powder form, or may be in a liquid or fluid form such as a solution or slurry containing a solvent. Examples of the solvent include alcohol-based solvents such as toluene and ethanol, ketone-based solvents such as methyl ethyl ketone, cycloalkane-based solvents such as cyclohexane, and the like. A mixed solvent of these may also be used. Among them, toluene is preferred.

[0049] <Manufacturing method of this resin composition> This resin composition can be manufactured by blending and mixing the piezoelectric inorganic compound (A), polymer (B), and conductive material (C) with other components (D) as necessary. A solvent may be used during mixing. Examples of the solvent include alcohol-based solvents such as toluene and ethanol, ketone-based solvents such as methyl ethyl ketone, cycloalkane-based solvents such as cyclohexane, and the like. Among them, toluene is preferred.

[0050] Mixing may be performed by a known method. For example, it can be carried out using a magnetic stirrer, shaker, planetary stirrer, ultrasonic device, or the like. When mixing, the blending ratio of each component is preferably in the range of 20 to 95% by volume of the piezoelectric inorganic compound (A), 5 to 80% by volume of the polymer (B), and 0.01 to 10% by volume of the conductive material (C), and more preferably in the range of 30 to 70% by volume of the piezoelectric inorganic compound (A), 30 to 70% by volume of the polymer (B), and 0.01 to 2.8% by volume of the conductive material (C).

[0051] <Polymer composite piezoelectric element> This resin composition is used as a polymer composite piezoelectric element material, and a polymer composite piezoelectric element can be produced from this resin composition. The polymer composite piezoelectric element is not particularly limited, but can be formed into shapes such as sheet-like, film-like, plate-like, porous, membrane-like, fiber-like, and laminated with an internal electrode structure, and may also have a three-dimensional structure.

[0052] For example, to form it into a film shape, the resin composition made into a solution containing a solvent is applied onto a release film, then dried to volatilize the solvent and cured, and then the release film is peeled off. By performing a poling treatment on the cured film-shaped resin composition, a polymer composite piezoelectric element can be produced.

[0053] The method of applying the solution may be performed by a conventionally known method. For example, it can be performed by a spin coating method, a spray coating method, a roll coating method, a slit coating method, a gravure coating method, a cast coating method, etc. Also, when patterning is required for manufacturing a piezoelectric element or the like, it can be performed using a known method such as an inkjet method, a screen printing method, a flexographic printing method, etc. The poling treatment may be performed by a conventionally known method. For example, it can be performed with an applied electric field of 1 to 20 kV / mm and an applied time of 1 to 60 minutes.

[0054] When it is a film-shaped polymer composite piezoelectric element, the thickness is preferably in the range of 50 to 1000 μm, more preferably in the range of 50 to 500 μm, and particularly preferably in the range of 75 to 200 μm.

[0055] <Piezoelectric constant>

[0056] In addition, the polymer composite piezoelectric element produced using this resin composition has an increased piezoelectric constant due to the inclusion of the conductive material (C). Compared with a polymer composite piezoelectric element (when not containing the conductive material (C)) in which the blending ratio of the piezoelectric inorganic compound (A) is the same or approximate, the piezoelectric constant d 33 can be increased to 7 pC / N or higher. Preferably, it can be increased to 10 pC / N or higher, more preferably 12 pC / N or higher. In the present invention, when the blending ratios are approximate, it means that the blending ratio of the piezoelectric inorganic compound (A) in this resin composition is preferably within ±5% by volume, more preferably within ±3% by volume, and particularly preferably within ±1% by volume.

[0057] <Use> The polymer composite piezoelectric element can be suitably used for various sensor devices such as pressure sensors, pressure distribution sensors, gyro sensors, shock sensors, seating sensors, wearable sensors, precision electronic devices, automobiles, damping materials used in buildings, etc., power generation elements using environmental vibrations generated by human walking or automobile driving, ignition devices such as lighters and gas appliances, oscillation circuits used in receivers such as radios and televisions, driving devices for scanning probe microscopes and ultrasonic motors, various actuators used in liquid ejection heads of inkjet printers, and medical materials related to tissue regeneration.

[0058] Among them, it is preferably used as a sensor device, and for example, it can be used as a tactile sensor of a robot or a health sensor attached to the body of a medical diagnostic device.

[0059] <Ink> This resin composition can be in the form of ink. When in the form of ink, a solvent is blended in the range of preferably 0.9 to 35 parts by mass, more preferably 2.5 to 28 parts by mass, and particularly preferably 5 to 24 parts by mass with respect to 100 parts by mass of this resin composition. Examples of the solvent include alcohol-based solvents such as toluene and ethanol, ketone-based solvents such as methyl ethyl ketone, and cycloalkane-based solvents such as cyclohexane. Among these, toluene is preferred. This ink can also be used as a polymer composite piezoelectric material.

Examples

[0060] Hereinafter, an example of the present invention will be described. However, the present invention is not limited to this example.

[0061] The polymer composite piezoelectric elements of Examples 1 to 4 and Comparative Examples 1 to 6 shown below were fabricated. The following were used as materials

[0062] [Materials] <Piezoelectric inorganic compound (A)> Potassium sodium niobate (manufactured by Nippon Chemical Industry Co., Ltd.: average particle diameter (D50) 810 nm) <Polymer (B)> 1. Toluene solution of maleimide-terminated polyimide resin (manufactured by Shima Trading Co., Ltd., ULTIMID 3000S: polyimide resin in the solution is 65% by volume) 2. Epoxy resin (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-40-2678") <Conductive material (C)> Metal oxide particles (manufactured by Otsuka Chemical Co., Ltd., Dentol WK-500, tin oxide-coated titanium oxide, needle-shaped: diameter 0.3 mm, length 15 μm)

[0063] [Examples 1 to 4] By mixing and stirring the above-described materials at the blending ratios shown in Table 1 below, a liquid resin composition was obtained. Note that the blending ratios in Table 1 are the values of the solid content excluding solvents such as toluene. This liquid resin composition was applied onto a release PET film using a 300-μm-thick film applicator (manufactured by Imoto Seisakusho Co., Ltd.), dried and cured at 180 °C for 3 hours or more to form a film. The film-shaped resin composition was peeled off from the release PET film, and polarization treatment was performed to obtain the polymer composite piezoelectric elements of Examples 1 to 4. The reflection electron scanning electron micrograph of the cross section of the film-shaped resin composition of Example 1 is shown in Fig. 1.

[0064] The polarization treatment was carried out by applying a voltage of 3 kV for 300 seconds while heating the film-shaped resin composition to 90 °C.

[0065] [Comparative Examples 1 to 3] A liquid resin composition was obtained in the same manner as in the examples, except that the conductive material (C) was not blended. The blending ratios are shown in Table 1 below. Using this liquid resin composition, a film-shaped resin composition was produced in the same manner as in the examples, and polarization treatment was performed to produce the polymer composite piezoelectric elements of Comparative Examples 1 to 3.

[0066] [Comparative Examples 4 to 6] A liquid resin composition was obtained in the same manner as in the examples, except that the polymer (B) was changed to an epoxy resin, the conductive material (C) was not blended, and toluene (manufactured by Fujifilm Wako Pure Chemical Corporation) was used as the solvent. The blending ratios are shown in Table 1 below. Using this liquid resin composition, a film-shaped resin composition was produced in the same manner as in the examples, and polarization treatment was performed to produce the polymer composite piezoelectric elements of Comparative Examples 4 to 6.

[0067] [Table 1]

[0068] <Piezoelectric constant d 33 Measurement> The piezoelectric constant d of the polymer composite piezoelectric elements of each example and each comparative example 33 was measured. The piezoelectric constant d of the polymer composite piezoelectric element 33 is d 33The piezometer (PKDs-2000 manufactured by PolyK Technologies LLC) was set to sandwich the thickness direction of the polymer composite piezoelectric element, and measurements were taken with a static force of 1 N, a vibration frequency of 110 kHz, and an amplitude of 0.25 N.

[0069] <Results> Piezoelectric constant d 33 As a result of the measurement, it was 51 pC / N in Example 1, 58 pC / N in Example 2, 72 pC / N in Example 3, and 51 pC / N in Example 4. Also, it was 39 pC / N in Comparative Example 1, 46 pC / N in Comparative Example 2, and 65 pC / N in Comparative Example 3. In Comparative Example 4 where an epoxy resin was used as the polymer (B), it was 38 pC / N, 46 pC / N in Comparative Example 5, and 67 pC / N in Comparative Example 6.

[0070] Based on these results, Fig. 2 shows a graph plotting the piezoelectric constant against the volume ratio (%) of the piezoelectric inorganic compound (A) in Examples 1 to 3 and Comparative Examples 1 to 3. Fig. 3 shows a graph plotting the piezoelectric constant against the volume ratio (%) of the conductive material (C) in Examples 1, 4 and Comparative Example 1.

[0071] <Discussion> By comparing Comparative Examples 1 to 3 with Comparative Examples 4 to 6, it was shown that the piezoelectric constant d 33 does not change significantly depending on the type of the polymer (B).

[0072] According to Fig. 2, it was understood that when the piezoelectric inorganic compound (A) has approximately the same volume ratio (%), blending the conductive material (C) can increase the piezoelectric constant and improve the piezoelectric properties.

[0073] According to Fig. 3, it was understood that the piezoelectric constant increased as the blending ratio of the conductive material (C) increased, as shown in the case where the piezoelectric inorganic compound (A) was about 55.0% by volume and the conductive material (C) was not blended (Comparative Example 1), the case where 1.0% by volume of the conductive material (C) was blended (Example 1), and the case where 1.5% by volume of the conductive material (C) was blended (Example 4).

[0074] From these results, it was found that a resin composition obtained by blending a conductive material (C) with a piezoelectric inorganic compound (A) and a polymer (B) increases the piezoelectric constant of a polymer composite piezoelectric element produced from the resin composition and improves the piezoelectric properties. In particular, the piezoelectric constant d of the polymer composite piezoelectric element was increased by blending the conductive material (C) as compared with the case where the blending ratio of the piezoelectric inorganic compound (A) was substantially the same. 33 This was found (see Fig. 2). Also, it is presumed that increasing the blending ratio of the conductive material (C) increases the piezoelectric constant d of the polymer composite piezoelectric element. (See Fig. 3). 33 ​

Claims

1. A resin composition containing a piezoelectric inorganic compound (A), a polymer (B), and a conductive material (C).

2. The resin composition according to Claim 1, wherein the piezoelectric inorganic compound (A) is a metal oxide containing niobium.

3. The resin composition according to Claim 2, wherein the metal oxide containing niobium is a compound represented by the following (Formula 1). Na ｘ K １－ｘ NbO ３＋ｙ ... (Formula 1) (0 ≦ x < 1, -0.05 ≦ y ≦ 0.05)

4. The resin composition according to Claim 1, wherein the conductive material (C) contains at least one selected from the group consisting of a metal, a metal oxide, carbon, or a conductive resin.

5. The resin composition according to Claim 1, wherein the blending ratio of the conductive material (C) in the resin composition is 0.01 to 10% by volume based on the total solid content of the resin composition.

6. The resin composition according to Claim 1, wherein the blending ratio of the piezoelectric inorganic compound (A) in the resin composition is 20 to 95% by volume based on the total solid content of the resin composition.

7. The resin composition according to Claim 1, wherein the polymer (B) contains at least one resin selected from the group consisting of a polyimide resin, an epoxy resin, and an acrylic resin.

8. A polymer composite piezoelectric material containing the resin composition according to any one of Claims 1 to 7.

9. A polymer composite piezoelectric element obtained by polarizing the resin composition according to any one of Claims 1 to 7.

10. A sensor device using the polymer composite piezoelectric element according to Claim 9.

11. An ink containing the resin composition according to any one of Claims 1 to 7 and a solvent.

12. A method for improving the piezoelectric constant d by blending a conductive material (C) into a resin composition containing a piezoelectric inorganic compound (A) and a polymer (B). ３３ ​

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