JP5652203B2 - Organic piezoelectric material and ultrasonic probe - Google Patents

Description

The present invention relates to organic piezoelectric material you containing a polymer having a condensed ring structure. Specifically, for example, acoustic devices such as microphones and diaphragms for speakers, measuring devices such as various pressure sensors, ultrasonic probe, vibration sensors that detect mutations such as genes and proteins with high sensitivity, etc. The present invention relates to an organic piezoelectric material having piezoelectricity that can be used to convert electrical energy.

As the pyroelectric material, a so-called inorganic material in which a single crystal such as quartz, LiNbO ₃ , LiTaO ₃ , KNbO ₃ , a thin film such as ZnO or AlN, or a sintered body such as Pb (Zr, Ti) O ₃ is subjected to polarization treatment. Piezoelectric materials are widely used. However, these inorganic piezoelectric materials have characteristics such as high elastic stiffness, high mechanical loss coefficient, high density and high dielectric constant.

  Meanwhile, organic piezoelectric materials such as polyvinylidene fluoride (hereinafter abbreviated as “PVDF”) and polycyanovinylidene (hereinafter abbreviated as “PVDCN”) have also been developed (see Patent Document 1). This organic piezoelectric material is excellent in workability such as thin film and large area, can be made in any shape and shape, and has features such as low elastic modulus and low dielectric constant, so it can be used as a sensor. When considering the use of, it has a feature that enables highly sensitive detection. On the other hand, organic piezoelectric materials have low heat resistance and lose their pyroelectric properties at high temperatures, and the physical properties such as elastic stiffness are greatly reduced.

  In contrast to these limitations, polyurea resin compositions composed of urea bonds have a large dipole moment of urea bonds and are excellent in temperature characteristics as resins. Therefore, various studies have been made as organic piezoelectric materials. . For example, there is a so-called vapor deposition polymerization method in which a polyisocyanate film is formed by simultaneously evaporating a diisocyanate compound such as 4,4′-diphenylmethane diisocyanate (MDI) and a diamine compound such as 4,4′-diaminodiphenylmethane (MDA). (See Patent Document 2 and Patent Document 3). However, the polyurea resin composition prepared by the vapor deposition polymerization method described in these documents has a non-uniform molecular weight of the oligomer or high molecular weight product. In this state, the polyurea resin composition is formed. For this reason, the dipole moment of the urea bond cannot be fully utilized, and further improvement has been demanded as an organic piezoelectric material.

  On the other hand, there have been few reports on a method for producing a polyurea resin composition having high orientation in solution polymerization, and a technique for producing a polyurea having a controllable molecular weight and high orientation is not known.

JP-A-6-216422 JP-A-2-284485 Japanese Patent Laid-Open No. 5-31399

  The present invention has been made in view of the above-described problems and situations, and the problem to be solved is as an organic piezoelectric material having piezoelectricity that is excellent in piezoelectric characteristics and capable of converting mechanical stimulation into electrical energy, and particularly oriented. It is an object to provide an organic piezoelectric material having high performance and being thermally stable.

  The above-mentioned problem according to the present invention is solved by the following means.

1. An organic piezoelectric material comprising a polymer containing at least one repeating unit represented by the following general formula (1).
General formula (1)
-X-A-
[In General Formula (1), X represents a divalent linking group composed of one group selected from a urea group and a urethane group or a combination of two or more thereof, and A represents a condensed ring containing at least one aromatic ring. (However, fullerene and fullerene derivatives are excluded) . ]

2. The weight average molecular weight of the polymer containing at least one repeating unit represented by the general formula (1) is 1,000 to 500,000,
In the general formula (1), A is naphthalene, anthracene, phenanthrene, fluorene, triphenylene, naphthacene, indole, benzofuran, benzothiophene, isobenzofuran, quinolidine, quinoline, phthalazine, naphthyridine, quinoxaline, quinoxazoline, carbazole, phenanthridine. , Acridine, phenanthroline, thianthrene, chromene, xanthene, phenoxathiin, phenothiazine, phenazine, pyrene, chrysene, perylene, pentacene, picene, quinazoline, dibenzofuran, indolizine, purine, pteridine 2. The organic piezoelectric material according to 1 above.
3 . An organic piezoelectric material comprising a polymer containing at least one repeating unit represented by the following general formula (1).
General formula (1)
-X-A-
In [Formula (1), X represents a divalent linking group, A represents a fused ring consisting of three rings containing three aromatic rings. ]

4 . 4. The organic piezoelectric material as described in 3 above, wherein the polymer comprising at least one repeating unit represented by the general formula (1) has a weight average molecular weight of 1,000 to 500,000.

5 . An ultrasonic probe including an ultrasonic transmission transducer and an ultrasonic reception transducer, wherein the ultrasonic transducer using the organic piezoelectric material according to any one of 1 to 4 is ultrasonicated. An ultrasonic probe comprising a receiving transducer.

  According to the present invention, an organic piezoelectric material having high orientation and being thermally stable and excellent in piezoelectric characteristics can be provided.

Conceptual diagram showing the configuration of the main part of an ultrasonic medical diagnostic imaging apparatus

  Next, the best mode for carrying out the present invention will be described, but the present invention is not limited thereto.

  The present invention can provide an organic piezoelectric material having excellent piezoelectricity and improved conventional problems by using a polymer containing at least one repeating unit represented by the general formula (1). In addition, the resin composition of the present invention, which contains a polymer containing at least one repeating unit represented by the general formula (2), has not only high orientation and excellent piezoelectricity, but also heat In terms of stability, it can be effectively used as a highly versatile resin.

<Polymer containing at least one repeating unit represented by formula (1)>
In the general formula (1), X represents a divalent linking group.

  Specific examples of X include alkylene group, phenylene group, amino group, sulfonyl group, urea group, urethane group, ester group, amide group, sulfonamide group, carbonate group, ether group, thioether. Groups, carbonyl groups and the like, and these linking groups may be further combined to form a composite group. In addition, n linking groups represented by X may be linked to form (X) n. At this time, n is an integer of 1 to 4.

  X is preferably one group selected from a urea group, a urethane group, an ester group, an amide group, a sulfonamide group, a carbonate group, an ether group, a thioether group, and a carbonyl group, or two of them. It is a divalent linking group comprising the above combination, more preferably a urea group, a urethane group, an ester group, an amide group, an ether group, and still more preferably a urea group, a urethane group, or an amide group.

  Specific examples of the group represented by X are given below, but the present invention is not limited thereto.

  In the general formula (1), A represents a condensed ring.

  A fused ring refers to a cyclic structure formed by a carbocycle, a heterocycle, or the like in which two or more of the atoms constituting the ring are bonded together with another ring.

  The condensed ring represented by A is preferably a condensed ring containing one aromatic ring, more preferably three rings selected from the group consisting of an aromatic ring, a heterocyclic ring and an aliphatic ring. It is a condensed ring.

  Specific examples include naphthalene, anthracene, phenanthrene, fluorene, triphenylene, naphthacene, indole, benzofuran, benzothiophene, isobenzofuran, quinolidine, quinoline, phthalazine, naphthyridine, quinoxaline, quinoxazoline, carbazole, phenanthridine, acridine, phenanthroline, thianthrene. , Chromene, xanthene, phenoxathiin, phenothiazine, phenazine, pyrene, chrysene, perylene, pentacene, picene, quinazoline, dibenzofuran, indolizine, purine, pteridine, bicyclohexane, etc., but are not limited thereto. .

  The condensed ring structure described above may further have a substituent well known in the art.

  The condensed ring represented by A is preferably naphthalene, anthracene, phenanthrene, fluorene, triphenylene, indole, benzofuran, benzothiophene, carbazole, phenanthridine, acridine, phenanthroline, phenothiazine, dibenzofuran, and more preferably anthracene, phenanthrene. Fluorene, carbazole, phenanthridine, acridine, and more preferably anthracene, phenanthrene, fluorene, and acridine.

  Specific examples of the condensed ring represented by A are given below, but the present invention is not limited to these.

  The polymer containing at least one repeating unit represented by the general formula (1) can be synthesized by a known method. For example, JP-A-61-203130, JP-A-2002-265553, JP-A-2003-238648, JP-A-2005-231064 or 5th edition Experimental Chemistry Course Vol. 26 Polymer Chemistry; page 123 ˜124 pages (Maruzen) and the like can be synthesized by referring to the method.

  Specific examples of the polymer containing at least one repeating unit represented by the general formula (1) are given below, but the present invention is not limited to these.

<Organic piezoelectric material>
The organic piezoelectric material of the present invention is formed by forming a film using a resin composition containing a polymer containing at least one repeating unit represented by the general formula (1), or on the resin composition film. On the other hand, an organic piezoelectric film can be formed by further performing a polarization treatment.

  In the organic piezoelectric film, when a stress is applied to the piezoelectric film, charges of opposite signs appear in proportion to both ends of the piezoelectric film, that is, an electric polarization phenomenon occurs, and conversely, the piezoelectric material is transmitted. It has the property (piezoelectric performance) that a distortion proportional to the occurrence of the electric field (applying an electric field) is generated. In particular, in the organic piezoelectric film made of the organic piezoelectric material of the present invention, a large piezoelectric effect is generated by polarization due to orientation freezing of the dipole moment of the polymer main chain or side chain.

(Method of forming organic piezoelectric film)
The organic piezoelectric film is preferably formed by coating. Examples of the coating method include spin coating, solvent casting, melt casting, roll coating, flow coating, printing, dip coating, and bar coating.

  In the method of forming a film by coating, a polymerized resin composition may be used, or after applying polyurea and a macromonomer, polymerization by heating may be performed.

  In the film formed on the substrate by coating, the solvent may be completely distilled off under heating or reduced pressure conditions. When polyurea and macromonomer are applied, the temperature is further increased after removing a predetermined amount of the solvent. The solvent may be distilled off and polymerization may be performed simultaneously.

  In the present invention, a method of performing polarization treatment described later on the formed film is preferable. When polyurea and macromonomer are applied, the polarization treatment may be performed after polymerization, or the polarization treatment is performed simultaneously with polymerization. May be. Particularly preferred is a method in which polymerization by heating and polarization treatment are performed simultaneously.

  The temperature when the polymerization by heating and the polarization treatment are simultaneously performed is preferably -50 to 250 ° C, more preferably -50 to 200 ° C. A method of changing the temperature in the above temperature range is also preferable.

(Polarization treatment)
As a polarization processing method in the polarization processing according to the present invention, various conventionally known methods can be applied.

  For example, in the case of the corona discharge treatment method, the corona discharge treatment can be performed by using a commercially available device comprising a high voltage power source and electrodes.

  Since the discharge conditions vary depending on the equipment and processing environment, it is preferable to select the conditions as appropriate. However, the voltage of the high voltage power source is −1 to −20 kV, the current is 1 to 80 mA, and the distance between the electrodes is 1 to 10 cm. The applied voltage is preferably 0.5 to 2.0 MV / m.

  As the electrodes, needle-like electrodes, linear electrodes (wire electrodes), and mesh-like electrodes that have been conventionally used are preferable, but the invention is not limited thereto.

  In addition, since heating is performed during corona discharge, it is necessary to install a heater via an insulator under the electrode in contact with the substrate manufactured according to the present invention.

  In the present invention, when the corona discharge treatment is performed as the polarization treatment in the state where the solvent of the raw material solution remains, the volatile components of the solvent are removed in order to avoid the danger of flammable explosion. It is necessary for safety to carry out with sufficient ventilation.

(substrate)
As the substrate, the selection of the substrate differs depending on the application and use method of the organic piezoelectric film of the present invention. It may be a plastic plate or film such as polyimide, polyamide, polyimide amide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polycarbonate resin, cycloolefin polymer. The surface may be covered with aluminum, gold, copper, magnesium, silicon or the like. Alternatively, a single crystal plate or film of aluminum, gold, copper, magnesium, silicon alone, or a rare earth halide may be used.

Further, it may be formed on a multilayer piezoelectric element. In a method of using a multilayer in which piezoelectric elements are laminated, there is a method in which the organic piezoelectric film of the present invention is superposed on a ceramic piezoelectric element via an electrode. PZT is used as the ceramic piezoelectric element, but in recent years, one containing no lead has been recommended. PZT is preferably within the range of the formula of Pb (Zr _1-X Ti _X ) O ₃ (0.47 ≦ X ≦ 1). As deleading, natural or artificial quartz, lithium niobate (LiNbO ₃ ), potassium niobium tantalate [K (Ta, Nb) O ₃ ], barium titanate (BaTiO ₃ ), lithium tantalate (LiTaO ₃ ), or strontium titanate (SrTiO ₃ ). The composition of various ceramic materials can be selected as appropriate in terms of performance.

<Ultrasonic transducer>
The ultrasonic transducer according to the present invention is characterized by using an organic piezoelectric film formed using the organic piezoelectric material of the present invention. The ultrasonic transducer is preferably an ultrasonic receiving transducer used in an ultrasonic medical diagnostic imaging device probe including an ultrasonic transmitting transducer and an ultrasonic transmitting transducer. .

  In general, an ultrasonic vibrator has a pair of electrodes sandwiched between layers (or films) made of a film-like piezoelectric material (also referred to as “piezoelectric film”, “piezoelectric film”, or “piezoelectric layer”). An ultrasonic probe is configured by arranging a plurality of transducers, for example, one-dimensionally.

  Then, a predetermined number of transducers in the major axis direction in which a plurality of transducers are arranged is set as the aperture, and the plurality of transducers belonging to the aperture are driven to converge the ultrasonic beam on the measurement site in the subject. And has a function of receiving reflected echoes of ultrasonic waves emitted from the subject by a plurality of transducers belonging to the aperture and converting them into electrical signals.

  Hereinafter, each of the ultrasonic wave receiving transducer and the ultrasonic wave transmitting transducer according to the present invention will be described in detail.

<Ultrasound receiving transducer>
An ultrasonic receiving transducer according to the present invention is a transducer used in a probe for an ultrasonic medical image diagnostic apparatus, and is formed using the organic piezoelectric material of the present invention as a piezoelectric material constituting the transducer. An organic piezoelectric film is used.

The organic piezoelectric material or the organic piezoelectric film used for the ultrasonic receiving vibrator preferably has a relative dielectric constant of 10 to 50 at the thickness resonance frequency. The adjustment of the relative dielectric constant is carried out by adjusting the number, composition, polymerization degree, etc. of polar functional groups such as CF ₃ groups and CN groups of the substituent R contained in the compound constituting the organic piezoelectric material, and the polarization treatment described above Can be done by.

<Transmitter for ultrasonic transmission>
The ultrasonic transmission vibrator according to the present invention is preferably made of a piezoelectric material having an appropriate relative dielectric constant in relation to the reception vibrator. Moreover, it is preferable to use a piezoelectric material excellent in heat resistance and voltage resistance.

  Various known organic piezoelectric materials and inorganic piezoelectric materials can be used as the ultrasonic transmitting vibrator constituent material.

  As the organic piezoelectric material, a polymer material similar to the above-described organic piezoelectric material for constituting an ultrasonic receiving vibrator can be used.

Inorganic materials include quartz, lithium niobate (LiNbO ₃ ), potassium tantalate niobate [K (Ta, Nb) O ₃ ], barium titanate (BaTiO ₃ ), lithium tantalate (LiTaO ₃ ), or titanate Lead zirconate (PZT), strontium titanate (SrTiO ₃ ), barium strontium titanate (BST), or the like can be used. PZT is preferably Pb (Zr _1-n Ti _n ) O ₃ (0.47 ≦ n ≦ 1).

<electrode>
The piezoelectric (body) vibrator according to the present invention is manufactured by forming electrodes on both surfaces or one surface of a piezoelectric film (layer) and polarizing the piezoelectric film. The electrode is formed using an electrode material mainly composed of gold (Au), platinum (Pt), silver (Ag), palladium (Pd), copper (Cu), nickel (Ni), tin (Sn), or the like. .

  In forming the electrodes, first, a base metal such as titanium (Ti) or chromium (Cr) is formed to a thickness of 0.02 to 1.0 μm by sputtering, and then the metal mainly composed of the above metal elements and those A metal material made of the above alloy, and further, if necessary, a part of insulating material is formed to a thickness of 1 to 10 μm by sputtering or other suitable methods. In addition to sputtering, these electrodes can be formed by screen printing, dipping, or thermal spraying using a conductive paste in which fine metal powder and low-melting glass are mixed.

  Furthermore, a piezoelectric element is obtained by supplying a predetermined voltage between the electrodes formed on both surfaces of the piezoelectric film to polarize the piezoelectric film.

(Ultrasonic probe)
The ultrasonic probe according to the present invention is a probe for an ultrasonic diagnostic imaging apparatus including an ultrasonic transmission transducer and an ultrasonic reception transducer. The ultrasonic receiving vibrator according to the above is used.

  In the present invention, both transmission and reception of ultrasonic waves may be performed by a single transducer, but more preferably, the transducers are configured separately for transmission and reception in the probe.

  The piezoelectric material constituting the transmitting vibrator may be a conventionally known ceramic inorganic piezoelectric material or an organic piezoelectric material.

  In the ultrasonic probe according to the present invention, the ultrasonic receiving transducer of the present invention can be arranged on or in parallel with the transmitting transducer.

  As a more preferred embodiment, the structure for laminating the ultrasonic receiving transducer of the present invention on the ultrasonic transmitting transducer is good, and in this case, the ultrasonic receiving transducer of the present invention is another high-frequency transducer. You may laminate | stack on the vibrator | oscillator for transmission in the form joined together on the molecular material (The polymer (resin) film, for example, polyester film) whose relative dielectric constant is comparatively low as a support body. In this case, it is preferable that the film thickness of the receiving vibrator and the other polymer material be matched to a preferable receiving frequency band in terms of probe design. Considering a practical ultrasonic medical diagnostic imaging apparatus and biological information collection from a practical frequency band, the film thickness is preferably 40 to 150 μm.

  The probe may be provided with a backing layer, an acoustic matching layer, an acoustic lens, and the like. Also, a probe in which vibrators having a large number of piezoelectric materials are two-dimensionally arranged can be used. A plurality of two-dimensionally arranged probes can be sequentially scanned to form a scanner.

(Ultrasonic medical diagnostic imaging equipment)
The ultrasonic probe according to the present invention can be used for various types of ultrasonic diagnostic apparatuses. For example, it can be suitably used in an ultrasonic medical image diagnostic apparatus as shown in FIG.

  FIG. 1 is a conceptual diagram showing a configuration of a main part of an ultrasonic medical image diagnostic apparatus according to an embodiment of the present invention. This ultrasonic medical diagnostic imaging apparatus transmits an ultrasonic wave to a subject such as a patient, and an ultrasonic probe in which piezoelectric vibrators that receive ultrasonic waves reflected by the subject as echo signals are arranged. (Probe). In addition, an electric signal is supplied to the ultrasonic probe to generate an ultrasonic wave, and a transmission / reception circuit that receives an echo signal received by each piezoelectric vibrator of the ultrasonic probe, and transmission / reception control of the transmission / reception circuit A transmission / reception control circuit is provided.

  Furthermore, an image data conversion circuit that converts echo signals received by the transmission / reception circuit into ultrasonic image data of the subject is provided. Further, a display control circuit for controlling and displaying the monitor with the ultrasonic image data converted by the image data conversion circuit and a control circuit for controlling the entire ultrasonic medical image diagnostic apparatus are provided.

  A transmission / reception control circuit, an image data conversion circuit, and a display control circuit are connected to the control circuit, and the control circuit controls operations of these units. Then, an electrical signal is applied to each piezoelectric vibrator of the ultrasonic probe to transmit an ultrasonic wave to the subject, and the reflected wave caused by acoustic impedance mismatch inside the subject is detected by the ultrasonic probe. Receive at.

  The transmission / reception circuit corresponds to “means for generating an electrical signal”, and the image data conversion circuit corresponds to “image processing means”.

  According to the ultrasonic diagnostic apparatus as described above, by utilizing the characteristics of the ultrasonic wave receiving vibrator excellent in piezoelectric characteristics and heat resistance of the present invention and suitable for high frequency and wide band, the image quality and its An ultrasonic image with improved reproduction and stability can be obtained.

<Polymer containing at least one repeating unit represented by formula (2)>
Next, the polymer containing at least one repeating unit represented by the general formula (2) will be described. In the general formula (2), X ₂ represents one group selected from a urea group, a urethane group, an ester group, and an amide group or a divalent linking group composed of a combination of two or more thereof, and A ₂ represents three groups. A condensed ring composed of the above rings is represented.

Specific examples of the condensed ring represented by A ₂ include a condensed ring composed of three or more rings among the examples given as specific examples of the condensed ring represented by A in the general formula (1). . A ₂ is preferably anthracene, phenanthrene, fluorene, triphenylene, carbazole, phenanthridine, acridine, phenanthroline, or phenothiazine.

  Specific examples of the polymer containing at least one repeating unit represented by the general formula (2) include P-1, P-2, P-7 to P-10, and P-12 to P- 16, P-18 to P-20, P-22, P-26 to P-31, P-34 to P-38, P-40, P-41, P-43 to P-51, P-54, P-59, P-60, etc. are mentioned.

  The resin composition characterized by containing a polymer containing at least one repeating unit represented by the general formula (2) in the present invention is used in a field where a piezoelectric polymer or pyroelectric polymer has been used. Although it can be used and is not particularly limited, for example, it is utilized in the acoustic field, ultrasonic field, medical / industrial field, taking advantage of characteristics such as piezoelectricity, workability, and film forming property. Specifically, it can be used for speakers, ultrasonic transducers, infrared sensors, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited to these.

(Synthesis Example 1: Synthesis of P-1 (polyurea))
In a 300 ml four-necked flask, 2,7-diaminofluorene (3.0 g, 15.3 mmol) and 100 ml of pyridine were added and stirred. Ammonium carbonate (1.2 g, 15.3 mmol) and triphenylphosphine (8.0 g, 30.6 mmol) were added and heated to 70 ° C. Hexachloroethane (7.2 g, 30.6 mmol) was added thereto, and the mixture was stirred at 70 ° C. for 3 hours. After cooling to room temperature, it was poured into 300 ml of methanol, and the precipitated polymer was filtered off, washed with water, dilute hydrochloric acid and ethyl acetate, and dried (yield 92%). The molecular weight was 32,000.

(Synthesis Example 2: Synthesis of P-2 (polyurethane))
1,5-pentanediol (2.7 g, 30 mmol) and 100 ml of chlorobenzene were dissolved in a 300 ml four-necked flask. The solution was heated to reflux, and a chlorobenzene solution (50 ml) of 2,7-diisocyanate fluorene (7.4 g, 30 mmol) was added dropwise thereto. After completion of the dropwise addition, the mixture was stirred for 1 hour under reflux and then cooled to room temperature. The precipitated polymer was filtered off, washed with methanol and dried (yield 86%). The molecular weight was 25,000.

(Synthesis Example 3: Synthesis of P-3 (polyamide))
In a 500 ml four-necked flask, bis (4-aminophenyl) ether (1.0 g, 5.0 mmol), naphthalene-2,7-dicarboxylic acid (1.1 g, 5.0 mmol), triphenyl phosphite (3 0.1 g, 5.0 mmol), lithium chloride (0.5 g), NMP (N-methylpyrrolidone) (10 ml), and pyridine (2.5 ml) were added. The mixture was stirred at 100 ° C. for 3 hours under nitrogen. The solution was poured into methanol (350 ml), the polymer was filtered off and dried under reduced pressure (88% yield). The molecular weight was 18,000.

  Other polymers of the present invention can be synthesized using the same method.

[Preparation of resin composition film]
(Production of Resin Composition Films-1 to 10)
The polymer represented by the general formula (1) was applied to a 25 μm polyimide film on which aluminum had been deposited in advance so that the dry film thickness was 7 μm and dried. Next, an aluminum electrode is attached by vapor deposition to the surface of the substrate on which the polymer film is formed, and then an electric field of 100 MV / m is applied using a high voltage power supply device HARB-20R60 (manufactured by Matsusada Precision Co., Ltd.). Then, the temperature was raised to 200 ° C. at a rate of 5 ° C./min, held at 200 ° C. for 15 minutes, then slowly cooled to room temperature while applying a voltage, and subjected to poling treatment, and the resin composition film-1 of the present invention To 10 were produced.

(Preparation of Comparative Resin Composition Film-A to C)
Comparative resin composition films A to C were produced in the same manner as in Example 4 except that the following comparative polymers A to C were used instead of the polymer represented by the general formula (1).

[Evaluation of resin composition film]
The obtained resin composition film was evaluated for piezoelectric characteristics while being heated to room temperature and 100 ° C. by a resonance method. The piezoelectric characteristics were measured using an impedance analyzer (Precision Impedance Analyzer 4294A manufactured by Agilent).

  The evaluation results are shown in Table 1. In addition, a piezoelectric characteristic is shown as a relative value with respect to Comparative-C (PVDF film) measured at room temperature as 100%.

  As is clear from the results shown in Table 1, it can be seen that the piezoelectric characteristics of the organic piezoelectric film formed of the polymer of the present invention are superior to those of the comparative example.

[Production and evaluation of ultrasonic probe]
<Production of piezoelectric material for transmission>
Component raw materials CaCO ₃ , La ₂ O ₃ , Bi ₂ O ₃ and TiO ₂ , and subcomponent raw materials MnO are prepared, and for the component raw materials, the final composition of the components is (Ca _0.97 La _0.03 ) Weighed to be Bi _4.01 Ti ₄ O ₁₅ . Next, pure water was added, mixed in a ball mill containing zirconia media in pure water for 8 hours, and sufficiently dried to obtain a mixed powder. The obtained mixed powder was temporarily molded and calcined in air at 800 ° C. for 2 hours to prepare a calcined product. Next, pure water was added to the obtained calcined material, finely pulverized in a ball mill containing zirconia media in pure water, and dried to prepare a piezoelectric ceramic raw material powder. In the fine pulverization, the piezoelectric ceramic raw material powder having a particle diameter of 100 nm was obtained by changing the pulverization time and pulverization conditions. 6% by mass of pure water as a binder is added to each piezoelectric ceramic raw material powder having a different particle diameter, press-molded to form a plate-shaped temporary molded body having a thickness of 100 μm, and this plate-shaped temporary molded body is vacuum-packed and then 235 MPa. It shape | molded by the press with the pressure of. Next, the molded body was fired. The final sintered body had a thickness of 20 μm. The firing temperature was 1100 ° C. An electric field of 1.5 × Ec (MV / m) or more was applied for 1 minute to perform polarization treatment. Ec (coercive electric field strength) was determined by DE hysteresis.

<Production of laminated resonator for reception>
A laminated vibrator was produced in which the organic piezoelectric film produced in Example 1 and a polyester film having a thickness of 50 μm were bonded together with an epoxy adhesive. Thereafter, polarization treatment was performed in the same manner as described above.

  Next, according to a conventional method, an ultrasonic probe was prototyped by laminating a laminated receiver for reception on the above-described piezoelectric material for transmission and installing a backing layer and an acoustic matching layer.

  As a comparative example, a probe similar to the above-described ultrasonic probe was produced using the comparative resin composition film-A instead of the above-described laminated resonator for reception.

  Next, the above two types of ultrasonic probes were evaluated by measuring the reception sensitivity and the dielectric breakdown strength.

Incidentally, the reception sensitivity is originating the fundamental frequency _{f 1} of 5 MHz, to determine the received relative sensitivity of 20MHz as 15 MHz, 4 harmonics as received second harmonic wave _{f 2} as 10 MHz, 3 harmonic. For the relative sensitivity of reception, a sound intensity measurement system Model 805 (1 to 50 MHz) manufactured by Sonora Medical System, Inc. (2021 Miller Drive Longmont, Colorado (0501 USA)) was used.

  The dielectric breakdown strength was measured by multiplying the load power P by 5 times, testing for 10 hours, and then returning the load power to the reference to evaluate the relative reception sensitivity. The sensitivity was evaluated as good when the decrease in sensitivity was within 1% before the load test, more than 1% and less than 10%, and 10% or more as bad.

  In the above evaluation, the ultrasonic probe including the receiving piezoelectric (body) laminated vibrator according to the present invention has a relative receiving sensitivity about 1.3 times that of the comparative example, and has a dielectric breakdown. It was confirmed that the strength was good. That is, it was confirmed that the ultrasonic wave receiving transducer of the present invention can be suitably used for a probe used in an ultrasonic medical image diagnostic apparatus as shown in FIG.

1 Receiving piezoelectric material (film)
2 Support 3 Piezoelectric material for transmission (film)
4 Backing layer 5 Electrode 6 Acoustic lens

Claims (5)

An organic piezoelectric material comprising a polymer containing at least one repeating unit represented by the following general formula (1).
General formula (1)
-X-A-
[In General Formula (1), X represents a divalent linking group composed of one group selected from a urea group and a urethane group or a combination of two or more thereof, and A represents a condensed ring containing at least one aromatic ring. (However, fullerene and fullerene derivatives are excluded) . ] The weight average molecular weight of the polymer containing at least one repeating unit represented by the general formula (1) is 1,000 to 500,000,
In the general formula (1), A is naphthalene, anthracene, phenanthrene, fluorene, triphenylene, naphthacene, indole, benzofuran, benzothiophene, isobenzofuran, quinolidine, quinoline, phthalazine, naphthyridine, quinoxaline, quinoxazoline, carbazole, phenanthridine. , Acridine, phenanthroline, thianthrene, chromene, xanthene, phenoxathiin, phenothiazine, phenazine, pyrene, chrysene, perylene, pentacene, picene, quinazoline, dibenzofuran, indolizine, purine, pteridine The organic piezoelectric material according to claim 1. An organic piezoelectric material comprising a polymer containing at least one repeating unit represented by the following general formula (1).
General formula (1)
-X-A-
In [Formula (1), X represents a divalent linking group, A represents a fused ring consisting of three rings containing three aromatic rings. ] 4. The organic piezoelectric material according to claim 3 , wherein the polymer including at least one type of repeating unit represented by the general formula (1) has a weight average molecular weight of 1,000 to 500,000. An ultrasonic probe comprising an ultrasonic transmission transducer and an ultrasonic reception transducer, wherein the ultrasonic transducer using the organic piezoelectric material according to any one of claims 1 to 4 is used. An ultrasonic probe comprising a transducer for receiving a sound wave.