WO2010061726A1 - Organic piezoelectric material, ultrasonic transducer and ultrasonic probe - Google Patents
Organic piezoelectric material, ultrasonic transducer and ultrasonic probe Download PDFInfo
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- WO2010061726A1 WO2010061726A1 PCT/JP2009/069175 JP2009069175W WO2010061726A1 WO 2010061726 A1 WO2010061726 A1 WO 2010061726A1 JP 2009069175 W JP2009069175 W JP 2009069175W WO 2010061726 A1 WO2010061726 A1 WO 2010061726A1
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- piezoelectric material
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
- H10N30/857—Macromolecular compositions
-
- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/09—Forming piezoelectric or electrostrictive materials
- H10N30/098—Forming organic materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/06—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction
- B06B1/0607—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements
- B06B1/0622—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements on one surface
- B06B1/064—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with piezoelectric effect or with electrostriction using multiple elements on one surface with multiple active layers
Definitions
- the present invention relates to an organic piezoelectric material, an ultrasonic transducer, and an ultrasonic probe using the same.
- Ultrasound is generally referred to as a sound wave of 16000 Hz or higher, and can be examined non-destructively and harmlessly, so that it is applied to various fields such as defect inspection and disease diagnosis.
- harmonic imaging that forms an image of the internal state in the subject using the harmonic frequency component, not the frequency (fundamental frequency) component of the ultrasound transmitted from the ultrasound probe into the subject ( Harmonic Imaging technology is being researched and developed.
- This harmonic imaging technology has (1) a low sidelobe level compared to the level of the fundamental frequency component, an improved S / N ratio (signal to noise ratio) and improved contrast resolution, and (2) frequency Increasing the beam width narrows and the lateral resolution is improved.
- Ultrasonic transducers for detecting received waves containing harmonic frequency components in ultrasonic probes for harmonic imaging require wider bandwidth sensitivity, and are organic polymer materials such as polyvinylidene fluoride (A organic piezoelectric material having PVDF as a main component is known. This organic piezoelectric material has a higher flexibility, thinner film, larger area, longer length, and can be made in any shape and form compared to inorganic piezoelectric materials, etc. Has characteristics.
- organic piezoelectric materials mainly composed of polyvinylidene fluoride are known to have very weak adhesion to electrode metals, and the electrodes may be peeled off due to friction during operation of the ultrasonic probe. There was a problem that peeling was caused even by weak friction during the process, making it difficult to process.
- Patent Documents 1 and 2 As a method for solving these problems, it is known that a monomer having an acrylic group is copolymerized or mixed in a copolymer with PVDF polymer and trifluoroethylene (for example, see Patent Documents 1 and 2). Also known is a method of improving the adhesion by surface processing the surface of an organic piezoelectric material by plasma discharge treatment or the like (see, for example, Patent Document 3).
- an organic binder layer is provided on the electrode, the surface of the organic binder layer is roughened, and a solution containing a fluororesin and a solvent is applied on the roughened organic binder layer to form an organic piezoelectric element.
- a solution containing a fluororesin and a solvent is applied on the roughened organic binder layer to form an organic piezoelectric element.
- Copolymerization or mixing of monomers having an acrylic group as described in Patent Document 1 and Patent Document 2 is due to the brittleness inherent in a highly crystalline PVDF polymer and a copolymer of trifluoroethylene. Further worsening is not necessarily desirable for application to an ultrasonic probe applied to a subject.
- the method of chemically changing the surface may promote the brittleness of the organic piezoelectric material, and even if physical etching is performed. In some cases, sufficient adhesion could not be obtained. In particular, when used for a long time as an ultrasonic vibration probe that oscillates and receives vibrations of several MHz, the adhesiveness may be significantly reduced.
- the present invention has been made in view of the above problems, and an object of the present invention is to provide an optimum condition for surface treatment for improving the electrode adhesion of an organic piezoelectric material, and to have excellent adhesion to an electrode metal. , Excellent resistance to electrode peeling due to friction during operation, excellent suppression of delamination even with weak friction during processing, organic to form an ultrasonic transducer with excellent piezoelectricity suitable for high frequency and wide band
- An object is to provide a piezoelectric material, an ultrasonic transducer, and an ultrasonic probe using the piezoelectric material.
- An organic piezoelectric material for forming an ultrasonic transducer wherein an arithmetic average roughness (Ra) of at least one surface is 0.01 ⁇ m or more and 0.9 ⁇ m or less.
- organic piezoelectric material according to 1, wherein the organic piezoelectric material has a copolymer of vinylidene fluoride and trifluoroethylene containing 60 to 95 mol% of vinylidene fluoride.
- An ultrasonic vibrator having an electrode bonded to the one surface of the organic piezoelectric material described in 3.1 or 2.
- An ultrasonic probe comprising the ultrasonic transducer according to 5.3 or 4.
- An ultrasonic transducer for transmission that transmits an ultrasonic wave toward a subject by an input electric signal, and the ultrasonic transducer converts an ultrasonic wave received from the subject into an electric signal and outputs the electric signal 5.
- the arithmetic average roughness (Ra) of at least one surface of the organic piezoelectric material is 0.01 ⁇ m or more and 0.9 ⁇ m or less, so that the adhesive property with the electrode metal is excellent, and the ultrasonic probe.
- Excellent resistance to electrode peeling due to friction during operation, excellent suppression of delamination generation even with weak friction during processing, excellent workability, adhesive strength that can withstand ultrasonic vibration, and piezoelectricity It is possible to provide an organic piezoelectric material, an ultrasonic transducer, and an ultrasonic probe using the same for forming an ultrasonic transducer suitable for high frequency and wide band.
- FIG. 1 is an external view illustrating an ultrasonic diagnostic apparatus according to an embodiment. It is a block diagram which shows the electrical structure of the ultrasound diagnosing device in this embodiment. It is typical sectional drawing which shows the structure of the ultrasound probe in the ultrasound diagnosing device of this embodiment.
- the arithmetic average roughness (Ra) of at least one surface of the organic piezoelectric material is 0.01 ⁇ m or more and 0.9 ⁇ m, so that the adhesion to the electrode metal is excellent. Excellent resistance to electrode peeling due to friction during operation, excellent suppression of delamination due to weak friction during processing, excellent workability, adhesive strength that can withstand ultrasonic vibration, and piezoelectricity And an organic piezoelectric material for forming an ultrasonic transducer suitable for high frequency and wide band.
- the unevenness of the organic piezoelectric material is defined as the arithmetic average roughness (Ra).
- the adhesiveness of the organic piezoelectric material is relatively unaffected by specific scratches that occur in minute regions, and the electrodes are joined. This is due to the influence of the unevenness of the entire joint surface. If the Ra value is less than 0.01 ⁇ m, the anchor effect cannot be obtained, so that the adhesiveness is not improved. If the Ra value exceeds 0.9 ⁇ m, the surface uniformity is not good, and the improvement in the adhesiveness is not observed.
- the arithmetic average roughness (Ra) of the surface means a value obtained by extracting only the reference length in the direction of the average line from the roughness curve and averaging the absolute ground of the deviation from the average line to the measurement curve.
- the arithmetic average roughness can be measured and determined according to JIS B 0601 using an atomic force microscope (AFM).
- Organic piezoelectric material as the constituent material of the piezoelectric material constituting the ultrasonic vibrator of the present invention can be adopted regardless of whether it is a low molecular material or a high molecular material.
- a high molecular organic piezoelectric material for example, polyvinylidene fluoride, a polyvinylidene fluoride copolymer, a polyvinylidene cyanide or a vinylidene cyanide copolymer, an odd-numbered nylon such as nylon 9 or nylon 11, or an aromatic Aromatic nylon, alicyclic nylon, polylactic acid, polyhydroxycarboxylic acids such as polyhydroxybutyrate, cellulose derivatives, polyurea and the like.
- a polymer organic piezoelectric material particularly a polymer material mainly composed of vinylidene fluoride is preferable.
- it is preferably a homopolymer of polyvinylidene fluoride having a CF 2 group having a large dipole moment or a copolymer having vinylidene fluoride as a main component.
- tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorofluoroethylene, etc. can be used as the second component in the copolymer.
- the electromechanical coupling constant (piezoelectric effect) in the thickness direction varies depending on the copolymerization ratio.
- the copolymerization ratio of vinylidene fluoride is 60 to 99 mol%, and furthermore, 85 to 99 mol. % Is preferred.
- the copolymerization ratio of vinylidene fluoride is 60 mol% or more and 95% or less, and the copolymerization ratio of trifluoroethylene is 5 mol. % To 40 mol% is more preferable.
- An organic piezoelectric material containing 85 to 99 mol% of vinylidene fluoride and 1 to 15 mol% of perfluoroalkyl vinyl ether, perfluoroalkoxyethylene, perfluorohexaethylene, etc. was applied to an ultrasonic probe. In some cases, it is possible to suppress the transmission fundamental wave and increase the sensitivity of harmonic reception.
- the organic piezoelectric material can be made thinner than an inorganic piezoelectric material made of ceramics, the organic piezoelectric material is characterized in that it can be used as a vibrator corresponding to transmission and reception of higher frequencies.
- the organic piezoelectric material according to the present embodiment preferably has a relative dielectric constant of 10 to 50 at the thickness resonance frequency.
- the relative dielectric constant can be adjusted by adjusting the number, composition, polymerization degree, etc. of polar functional groups such as CF 2 groups and CN groups contained in the compound constituting the organic piezoelectric material, and polarization treatment described later. .
- an ultrasonic vibrator in which the organic piezoelectric material according to the present embodiment and a plurality of polymer materials are laminated can also be configured.
- the polymer material to be laminated the following polymer material having a relatively low relative dielectric constant can be used in addition to the above polymer material.
- the numerical value in parentheses indicates the relative dielectric constant of the polymer material (resin).
- the polymer material having a low relative dielectric constant is preferably selected in accordance with various purposes such as adjusting the piezoelectric characteristics or imparting the physical strength of the organic piezoelectric film. .
- the organic piezoelectric material according to the present embodiment can be manufactured by various methods using the polymer material as a main constituent.
- a general method such as a melting method or a casting method can be used.
- a polyvinylidene fluoride-trifluoroethylene copolymer it is known that it has a crystalline form with spontaneous polarization only when it is made into a film, but in order to further improve the characteristics, a process for aligning the molecular arrangement should be added. Is useful. Examples of means include stretching film formation and polarization treatment.
- the stretching film forming method various known methods can be employed. For example, a solution obtained by dissolving the above polymer material in an organic solvent such as ethyl methyl ketone (MEK) is cast on a substrate such as a glass plate, and the solvent is dried at room temperature to obtain a film having a desired thickness. The film is stretched to a predetermined length at room temperature. The stretching can be performed in uniaxial and biaxial directions so that the organic piezoelectric film having a predetermined shape is not broken.
- the draw ratio is 2 to 10 times, preferably 2 to 6 times.
- the melt flow rate at 230 ° C. is 0.03 g / min or less. More preferably, a high-sensitivity piezoelectric thin film can be obtained by using a polymer piezoelectric body of 0.02 g / min or less, more preferably 0.01 g / min.
- Relaxing treatment can be applied to the stretched organic piezoelectric material.
- the flexibility, weakening, flatness, etc. of the organic piezoelectric material can be improved.
- the relaxation treatment is a process in which the stress at both ends of the organic piezoelectric material is changed while following the contraction or expansion force applied to the film-like organic piezoelectric material in the process of cooling to room temperature after the heat treatment. is there.
- Relaxation treatment does not stretch in the direction in which tension is applied even if it is shrunk so as to relieve stress unless the organic piezoelectric material relaxes and flatness cannot be maintained or the stress increases and breaks. It may be spread over.
- the amount of relaxation treatment in the present invention is about 10% in length when the stretched direction is determined to be positive, and about 15% in order to follow slack when the film stretches during cooling. It is preferred to do so.
- the end is supported by a chuck, a clip, etc., and the temperature is 10 ° C. lower than the melting point of the organic piezoelectric material. It is preferable to place it near the temperature with the upper limit being.
- the melting point is 150 ° C. to 180 ° C., and therefore, it is preferable to perform heat treatment at a temperature of 100 ° C. or more and 140 ° C. or less.
- the longer the time is, the longer the effect is expressed and the longer the effect is exhibited, the longer the crystal growth is promoted. However, since the saturation occurs with time, it is practically about 10 hours and at most about day and night.
- Ra surface processing of organic piezoelectric material front and back Various known methods can be employed for the surface treatment of setting the Ra on the front and back surfaces of the organic piezoelectric material according to the present embodiment to 0.01 to 0.9 ⁇ m.
- rough surface processing can be performed by atmospheric pressure plasma treatment, reduced pressure plasma treatment, corona discharge treatment, precision polishing, and the like.
- the surface processing is not limited to these, but is preferably performed in an inert gas atmosphere that does not cause a chemical change on the surface of the organic piezoelectric material.
- Ra can be made desired by appropriately selecting the treatment time, the voltage to be applied, the particle size of the abrasive, and the like.
- the organic piezoelectric material according to the present embodiment can be subjected to polarization treatment.
- polarization processing method a conventionally known method such as DC voltage application processing, AC voltage application processing, or corona discharge processing can be applied.
- the corona discharge treatment can be performed by using a commercially available apparatus comprising a high voltage power source and electrodes.
- the voltage of the high voltage power source is preferably ⁇ 1 to ⁇ 20 kV, the current is 1 to 80 mA, the distance between the electrodes is preferably 1 to 10 cm, and the applied voltage is preferably 0.5 to 2.0 MV / m. .
- the discharge electrode a needle electrode, a wire electrode (wire electrode), and a mesh electrode that have been conventionally used are preferable, but the present invention is not limited thereto.
- the polarization treatment may be performed after forming the electrodes placed on either the front or back surface of the organic piezoelectric material.
- the ultrasonic transducer is configured by arranging a pair of electrodes with a film-like organic piezoelectric material interposed therebetween, and an ultrasonic probe is configured by arranging a plurality of transducers, for example, one-dimensionally.
- the ultrasonic transducer having the organic piezoelectric material according to the present embodiment is manufactured by forming electrodes on both sides or one side of the organic piezoelectric material 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. .
- a base metal such as titanium (Ti) or chromium (Cr) is formed to a thickness of 0.02 to 1.0 ⁇ m by 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.
- a piezoelectric element can be obtained by supplying a predetermined voltage between the electrodes formed on both surfaces of the piezoelectric film to polarize the piezoelectric film.
- the thickness of the organic piezoelectric material can be made uniform so that the direction in which the organic piezoelectric material is relaxed and the long side direction of the rectangular ultrasonic transducer are parallel to each other. This is preferable in that stable piezoelectric performance can be obtained.
- FIG. 1 is an external view of the ultrasonic diagnostic apparatus according to the present embodiment
- FIG. 2 is a block diagram illustrating an electrical configuration of the ultrasonic diagnostic apparatus according to the present embodiment.
- the ultrasonic diagnostic apparatus S transmits an ultrasonic wave to a subject (not shown) and receives an ultrasonic wave reflected from the subject, an ultrasonic probe 2, and a cable. 3, and by transmitting a transmission signal of an electrical signal to the ultrasonic probe 2 via the cable 3, the ultrasonic probe 2 transmits ultrasonic waves to the subject, Based on the received signal of the electric signal generated by the ultrasonic probe 2 in accordance with the reflected wave of the ultrasonic wave from the inside of the subject received by the probe 2, the internal state in the subject is converted into an ultrasonic image. And an ultrasonic diagnostic apparatus main body 1 for imaging.
- the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11 for inputting data such as a command for starting diagnosis and personal information of a subject, and a cable 3 to the ultrasonic probe 2.
- a transmission circuit 12 for supplying a transmission signal of an electrical signal via the transmitter and generating an ultrasonic wave in the ultrasonic probe 2 and reception for receiving a reception signal of the electrical signal from the ultrasonic probe 2 via the cable 3
- the circuit 13 an image processing unit 14 that generates an image (ultrasonic image) of the internal state in the subject based on the reception signal received by the receiving circuit 13, and the internal part in the subject generated by the image processing unit 14
- the ultrasonic diagnostic apparatus S as a whole is controlled by controlling the display unit 15 that displays the state image and the operation input unit 11, the transmission circuit 12, the reception circuit 13, the image processing unit 14, and the display unit 15 according to the function.
- Control unit 16 that performs control Equipped with a.
- the ultrasonic probe 2 includes a plurality of inorganic piezoelectric elements and a plurality of organic piezoelectric elements.
- Each of the inorganic piezoelectric elements includes an inorganic piezoelectric material, and a plurality of inorganic piezoelectric elements capable of mutually converting signals between an electric signal and an ultrasonic signal by using a piezoelectric phenomenon, and the present embodiment
- An organic piezoelectric element that is an ultrasonic vibrator including an organic piezoelectric material according to a form includes an organic piezoelectric element that can mutually convert a signal between an electrical signal and an ultrasonic signal by using a piezoelectric phenomenon. It has.
- FIG. 3 is a schematic cross-sectional view showing the configuration of the ultrasonic probe in the ultrasonic diagnostic apparatus of the present embodiment.
- the ultrasonic probe 2 ⁇ / b> A is laminated on the flat acoustic braking member 23, the plurality of inorganic piezoelectric elements 22 stacked on one main surface of the acoustic braking member 23, and the plurality of inorganic piezoelectric elements 22.
- the intermediate layer 26, the plurality of organic piezoelectric elements 21 stacked on the intermediate layer 26, the acoustic matching layer 27 stacked on the organic piezoelectric element 21, the plurality of inorganic piezoelectric elements 22 and the plurality of organic layers And an acoustic absorber 24 filled in a gap in the piezoelectric element 21.
- the acoustic braking member 23 is made of a material that absorbs ultrasonic waves, and absorbs ultrasonic waves radiated from the plurality of inorganic piezoelectric elements 22 toward the acoustic absorbing member 23.
- Each inorganic piezoelectric element 22 in the plurality of inorganic piezoelectric elements 22 includes electrodes 2021 and 2031 on opposite surfaces of a piezoelectric body 2011 made of an inorganic piezoelectric material.
- the plurality of inorganic piezoelectric elements 22 are arranged on the acoustic braking member 23 in a two-dimensional array in plan view with a predetermined interval therebetween.
- the plurality of inorganic piezoelectric elements 22 may be configured to receive reflected ultrasonic waves, but the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment transmit ultrasonic waves. It is configured. That is, the inorganic piezoelectric element 22 functions as an ultrasonic transducer for transmission.
- an electrical signal is input to the plurality of inorganic piezoelectric elements 22 from the transmission circuit 12 via the cable 3.
- This electrical signal is input to the electrodes 2021 and 2031 of the inorganic piezoelectric element 22.
- the plurality of inorganic piezoelectric elements 22 transmit this ultrasonic signal by converting this electric signal into an ultrasonic signal.
- the acoustic absorber 24 is made of a material that absorbs ultrasonic waves, and is for reducing mutual interference between the plurality of inorganic piezoelectric elements 22 and organic piezoelectric elements 21.
- the acoustic absorber 24 can reduce crosstalk between the inorganic piezoelectric elements 22 and the organic piezoelectric elements 21.
- the intermediate layer 26 is a member for laminating the plurality of inorganic piezoelectric elements 22 and the organic piezoelectric elements 21, and matches the acoustic impedance between the plurality of inorganic piezoelectric elements 22 and the organic piezoelectric elements 21.
- the organic piezoelectric element 21 includes a piezoelectric body 101 made of an organic piezoelectric material according to the present embodiment, and electrodes 102 and 103 on both surfaces of the piezoelectric body 101 facing each other. Similar to the inorganic piezoelectric element 22, the plurality of organic piezoelectric elements 21 are arranged on the intermediate layer 26 in a two-dimensional array in plan view at a predetermined interval.
- the plurality of organic piezoelectric elements 21 are laminated on the plurality of inorganic piezoelectric elements 22 on the acoustic braking member 23 by vapor-depositing a metal serving as an electrode on the front and back surfaces of an integral sheet-like organic piezoelectric material by a known method. After bonding on the intermediate layer 26, they are separated individually by cutting together with the intermediate layer 26 so as to form the same two-dimensional array as the plurality of inorganic piezoelectric elements 22 with a dicing saw.
- the organic piezoelectric element 21 may be configured to transmit ultrasonic waves, but the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment are configured to receive ultrasonic reflected waves. ing. More specifically, the organic piezoelectric element 21 receives an ultrasonic signal of a reflected wave, and outputs the electric signal by converting the ultrasonic signal into an electric signal. This electrical signal is output from the electrode 102 and the electrode 103 in the organic piezoelectric element 21. This electrical signal is output to the receiving circuit 13 via the cable 3.
- the acoustic matching layer 27 is a member that matches the acoustic impedance of the inorganic piezoelectric element 22 and the acoustic impedance of the subject and matches the acoustic impedance of the organic piezoelectric element 21 and the acoustic impedance of the subject.
- the acoustic matching layer 27 includes an acoustic lens that converges an ultrasonic wave that is transmitted toward the subject, and has an arcuate shape.
- the organic piezoelectric element 21 is stacked on the subject side (in the direction indicated by the arrow X) of the inorganic piezoelectric element 22, so that the ultrasonic wave transmitted from the inorganic piezoelectric element 22 is transmitted. You will receive sound waves at close range. Therefore, the piezoelectric body 101 and the electrodes 102 and 103 tend to be exfoliated by ultrasonic waves transmitted from the inorganic piezoelectric element 21.
- the organic piezoelectric material according to the present embodiment to the organic piezoelectric element 21, the adhesive strength between the piezoelectric body 101 and the electrodes 102 and 103 is maintained even during long-term use, and no peeling occurs. It becomes.
- the transmission circuit 12 When a diagnosis start instruction is input from the operation input unit 11, the transmission circuit 12 generates an electric signal transmission signal under the control of the control unit 16.
- the generated electrical signal transmission signal is supplied to the ultrasonic probe 2 via the cable 3. More specifically, this electrical signal transmission signal is supplied to each of the plurality of inorganic piezoelectric elements 22 in the ultrasonic probe 2.
- the electric signal transmission signal is, for example, a voltage pulse repeated at a predetermined cycle.
- Each of the plurality of inorganic piezoelectric elements 22 expands and contracts in the thickness direction when supplied with the transmission signal of the electric signal, and ultrasonically vibrates according to the transmission signal of the electric signal.
- the plurality of inorganic piezoelectric elements 22 radiate ultrasonic waves through the intermediate layer 26, the organic piezoelectric element 21 and the acoustic matching layer 27.
- ultrasonic waves are transmitted from the ultrasonic probe 2 to the subject.
- the ultrasound probe 2 may be used in contact with the surface of the subject, or may be used by being inserted into the subject, for example, being inserted into a body cavity of a living body. .
- the ultrasonic wave transmitted to the subject is reflected at one or a plurality of boundary surfaces having different acoustic impedances inside the subject, and becomes a reflected wave of the ultrasonic wave.
- This reflected wave includes not only the frequency component of the transmitted ultrasonic wave (fundamental fundamental frequency) but also the frequency component of a harmonic that is an integral multiple of the fundamental frequency. For example, second harmonic components such as twice, three times, and four times the fundamental frequency, third harmonic components, and fourth harmonic components are also included.
- the ultrasonic wave of the reflected wave is received by the ultrasonic probe 2.
- the ultrasonic wave of the reflected wave is received by the organic piezoelectric element 21 through the acoustic matching layer 27, and mechanical vibration is converted into an electric signal by the organic piezoelectric element 21 and is extracted as a received signal.
- the extracted reception signal of the electrical signal is received by the receiving circuit 13 controlled by the control unit 16 via the cable 3.
- ultrasonic waves are sequentially transmitted from the inorganic piezoelectric elements 22 toward the subject, and the ultrasonic waves reflected by the subject are received by the organic piezoelectric elements 21.
- the image processing unit 14 controls the image of the internal state in the subject (ultrasonic image) based on the reception signal received by the receiving circuit 13 based on the reception signal received by the reception circuit 13 based on the time from transmission to reception and the reception intensity.
- the display unit 15 displays the image of the internal state in the subject generated by the image processing unit 14 under the control of the control unit 16.
- the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment since the harmonics of the fundamental wave are received as described above, an ultrasonic image can be formed by the harmonic imaging technique. For this reason, the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment can provide a more accurate ultrasonic image. Since the second and third harmonics having relatively high power are received, a clearer ultrasonic image can be provided.
- the plurality of inorganic piezoelectric elements 22 are configured to transmit ultrasonic waves. Since the ultrasonic signal is transmitted by the inorganic piezoelectric element 22 capable of increasing the transmission power in this way, the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S increase the transmission power with a relatively simple structure. can do. Therefore, the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment transmit the fundamental wave with a sound pressure sufficient to obtain the echo of the harmonic generated in the subject with the ultrasonic probe 2A. This is suitable for the harmonic imaging technique that needs to be performed, and it is possible to provide a more accurate ultrasonic image.
- the organic piezoelectric element 21 is configured to receive an ultrasonic reflected wave.
- a piezoelectric element made of an inorganic piezoelectric material can receive only an ultrasonic wave having a frequency about twice the frequency of the fundamental wave, but a piezoelectric element made of an organic piezoelectric material is about 4 to 5 times the frequency of the fundamental wave, for example. It is possible to receive an ultrasonic wave having a frequency of 5 and is suitable for widening the reception frequency band.
- the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment are compared.
- the frequency band can be widened with a simple structure.
- the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment are suitable for harmonic imaging technology that needs to receive the third and higher harmonics of the fundamental wave, and more accurate ultrasonic waves. Images can be provided.
- the ultrasonic diagnostic apparatus 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, particularly durability, can be obtained.
- Example 1 Production of organic piezoelectric film material >> A polyvinylidene fluoride copolymer having a molar ratio of vinylidene fluoride (hereinafter referred to as VDF) and trifluoroethylene (hereinafter referred to as 3FE) of 75:25 prepared according to the method described in European Patent No. 626,396 is prepared at 50 ° C. A solution of methyl ethyl ketone (hereinafter referred to as MEK) and N, N-dimethylformamide (hereinafter referred to as DMF) in a 9: 1 mixed solvent was cast on a glass plate. Thereafter, the solvent was dried at 55 ° C. to obtain a film (organic piezoelectric material) having a thickness of about 120 ⁇ m.
- VDF vinylidene fluoride
- 3FE trifluoroethylene
- the film was stretched 4 times in a uniaxial direction at room temperature, then heat-treated at 135 ° C. for 1 hour while maintaining the stretched length, and then naturally cooled.
- the film thickness of the obtained film 1 after the heat treatment was 43 ⁇ m.
- the electrode was subjected to polarization treatment while applying an AC voltage of 0.1 Hz at room temperature to obtain an organic piezoelectric material sample 1 having electrodes on the front and back surfaces.
- the polarization process was performed from a low voltage, and the voltage was gradually applied until the electric field between the electrodes finally reached 100 MV / m.
- the organic piezoelectric material sample 2 is the same as the organic piezoelectric material sample 1 except that the arithmetic mean roughness (Ra) is changed to 0.05 ⁇ m, 0.1 ⁇ m, and 0.9 ⁇ m by changing the processing time of the atmospheric pressure plasma processing. ⁇ 4 were obtained.
- An organic piezoelectric material sample 5 was obtained by directly depositing gold on the film 1 without performing plasma treatment to produce an electrode, and subsequently performing a polarization treatment in the same manner as the organic piezoelectric material sample 1. .
- organic piezoelectric material body samples 6 and 7 were prepared in the same manner as the organic piezoelectric material sample 1 except that the arithmetic mean roughness (Ra) was changed to 0.005 ⁇ m and 1.5 ⁇ m by changing the processing time of the atmospheric pressure plasma processing. Obtained.
- the organic piezoelectric material is the same as the organic piezoelectric material samples 1 to 4, 6, and 7 except that the organic piezoelectric material is a PVDF homopolymer organic piezoelectric film (manufactured by Atchem).
- the film manufactured by Atchem was subjected to atmospheric pressure plasma treatment to obtain an organic piezoelectric material sample 8.
- the arithmetic average roughness (Ra) was 0.1 ⁇ m.
- Adhesiveness immediately after deposition electrode production Adhesion was measured by a 90 degree peel test. Specifically, adhesive was applied to the surface of the electrode deposited on Samples 1 to 8, and Kapton Silicone tape (trade name: Kapton Tape (P221), manufactured by Permacel), manufacturer name: Permacel, specification thickness 25 ⁇ m, silicone The maximum force required for peeling when the silicone-made Kapton tape was peeled in the normal direction of the adhesive surface was measured after the heat treatment by pressure bonding, and evaluated as adhesiveness according to the following evaluation criteria.
- AS ONE product name US CLLEANER model number US-5R an ultrasonic cleaning machine
- Electrode durability [Method for evaluating organic piezoelectric material]
- Lead electrodes are attached to the electrodes on both sides of the organic piezoelectric material body samples 1 to 8 with electrodes obtained as described above, and an impedance analyzer 4294A manufactured by Agilent Technologies is used, and an atmosphere of 25 ° C., from 40 Hz to 110 MHz. The frequency was swept at 600 points at equal intervals. The value of the relative dielectric constant at the thickness resonance frequency was obtained. Similarly, when the peak frequency P of the resistance value near the thickness resonance frequency and the peak frequency S of the conductance were obtained, the electromechanical coupling constant kt was obtained by the following equation.
- the piezoelectricity was evaluated according to the following evaluation criteria. Evaluation criteria ⁇ : 0.2 or more ⁇ : less than 0.2 The results are shown in Table 1.
- the adhesiveness was improved by setting the arithmetic average roughness (Ra) to 0.01 to 0.9 ⁇ m. In addition, there was no decrease in piezoelectricity due to the surface treatment.
- the sample using the polyvinylidene fluoride copolymer having a molar ratio of VDF and 3FE of 75:25 is higher than the sample 8 which is a PVDF homopolymer, in addition to the higher adhesion immediately after the deposition, It is also seen that there is little decrease in adhesion due to ultrasonic irradiation.
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Abstract
The optimum surface processing conditions required for having excellent adhesion of an organic piezoelectric material to an electrode are provided. An organic piezoelectric material, which has excellent adhesion to an electrode metal and excellent resistance characteristics to electrode peeling due to friction during operation, excellently suppresses peeling due to even weak friction generated during processing, and is suitable to be used in high-frequency and wide band with excellent piezoelectric characteristics, an ultrasonic transducer, and an ultrasonic probe using the ultrasonic transducer are also provided. The organic piezoelectric material for forming the ultrasonic transducer is characterized in that the arithmetic average roughness (Ra) of at least one surface is 0.01 μm or more but not more than 0.9 μm.
Description
本発明は、有機圧電材料、超音波振動子、およびそれを用いた超音波探触子に関する。
The present invention relates to an organic piezoelectric material, an ultrasonic transducer, and an ultrasonic probe using the same.
超音波は、通常、１６０００Ｈｚ以上の音波を総称して言われ、非破壊および無害でその内部を調べることが可能なことから、欠陥の検査や疾患の診断などの様々な分野に応用されている。そして、近年では、超音波探触子から被検体内へ送信された超音波の周波数（基本周波数）成分ではなく、その高調波周波数成分によって被検体内の内部状態の画像を形成するハーモニックイメージング（Ｈａｒｍｏｎｉｃ Ｉｍａｇｉｎｇ）技術が研究、開発されている。このハーモニックイメージング技術は、（１）基本周波数成分のレベルに比較してサイドローブレベルが小さく、Ｓ／Ｎ比（ｓｉｇｎａｌ ｔｏ ｎｏｉｓｅ ｒａｔｉｏ）が良くなってコントラスト分解能が向上すること、（２）周波数が高くなることによってビーム幅が細くなって横方向分解能が向上すること、（３）近距離では音圧が小さくて音圧の変動が少ないために多重反射が抑制されること、および（４）焦点以遠の減衰が基本波並みであり高周波を基本波とする場合に較べて深速度を大きく取れることなどの様々な利点を有している。
Ultrasound is generally referred to as a sound wave of 16000 Hz or higher, and can be examined non-destructively and harmlessly, so that it is applied to various fields such as defect inspection and disease diagnosis. . In recent years, harmonic imaging that forms an image of the internal state in the subject using the harmonic frequency component, not the frequency (fundamental frequency) component of the ultrasound transmitted from the ultrasound probe into the subject ( Harmonic Imaging technology is being researched and developed. This harmonic imaging technology has (1) a low sidelobe level compared to the level of the fundamental frequency component, an improved S / N ratio (signal to noise ratio) and improved contrast resolution, and (2) frequency Increasing the beam width narrows and the lateral resolution is improved. (3) Since the sound pressure is small and the fluctuation of the sound pressure is small at a short distance, multiple reflections are suppressed. (4) Focus It has various advantages such as a greater depth speed compared to the case where the further attenuation is the same as the fundamental wave and the high frequency is the fundamental wave.
ハーモニックイメージング用の超音波探触子における、高調波周波数成分を含む受信波を検知する超音波振動子には、より広い帯域巾の感度が必要で、有機系高分子材料であるポリフッ化ビニリデン（ＰＶＤＦ）を主成分とする有機圧電材料が知られている。この有機圧電材料は、無機圧電体と比較して、可撓性が大きい、薄膜化、大面積化、長尺化が容易である、任意の形状、形態のものを作ることができる、等の特性を有する。
Ultrasonic transducers for detecting received waves containing harmonic frequency components in ultrasonic probes for harmonic imaging require wider bandwidth sensitivity, and are organic polymer materials such as polyvinylidene fluoride ( An organic piezoelectric material having PVDF as a main component is known. This organic piezoelectric material has a higher flexibility, thinner film, larger area, longer length, and can be made in any shape and form compared to inorganic piezoelectric materials, etc. Has characteristics.
しかしながら、ポリフッ化ビニリデンを主成分とする有機圧電材料は、電極金属との接着が非常に弱いことが知られており、超音波探触子の操作中に摩擦などで電極はがれを起こし、加工を行う際に弱い摩擦でも剥離が起きてしまい加工がしにくいなどの問題があった。
However, organic piezoelectric materials mainly composed of polyvinylidene fluoride are known to have very weak adhesion to electrode metals, and the electrodes may be peeled off due to friction during operation of the ultrasonic probe. There was a problem that peeling was caused even by weak friction during the process, making it difficult to process.
これらの問題を解決する方法としてＰＶＤＦ重合体及びトリフルオロエチレンとの共重合体中にアクリル基を有するモノマーを共重合、あるいは混合させることが知られている（例えば特許文献１、２参照）。また、有機圧電材料の表面をプラズマ放電処理などにより表面加工し接着性を改善させる方法も知られている（例えば特許文献３参照）。
As a method for solving these problems, it is known that a monomer having an acrylic group is copolymerized or mixed in a copolymer with PVDF polymer and trifluoroethylene (for example, see Patent Documents 1 and 2). Also known is a method of improving the adhesion by surface processing the surface of an organic piezoelectric material by plasma discharge treatment or the like (see, for example, Patent Document 3).
また、電極の上に有機結合材層を設け、有機結合材層の表面を粗面化し、粗面化した有機結合材層の上にフッ素系樹脂と溶剤を含む溶液を塗布して有機圧電素子を作製することが提案されている（例えば特許文献４参照）。特許文献４に記載の方法によれば、溶剤の作用により有機結合材層と有機圧電素子の結合強度が増強されるものである。
In addition, an organic binder layer is provided on the electrode, the surface of the organic binder layer is roughened, and a solution containing a fluororesin and a solvent is applied on the roughened organic binder layer to form an organic piezoelectric element. Has been proposed (see, for example, Patent Document 4). According to the method described in Patent Document 4, the bond strength between the organic binder layer and the organic piezoelectric element is enhanced by the action of a solvent.
特許文献１及び特許文献２に記載の如くアクリル基を有するモノマーを共重合、あるいは混合させるのは、結晶性が高いＰＶＤＦ重合体及びトリフルオロエチレンとの共重合体がもともと有している脆性をさらに悪化させるものであり、被検体にあてがう超音波探触子に適用するには必ずしも好ましくなかった。
Copolymerization or mixing of monomers having an acrylic group as described in Patent Document 1 and Patent Document 2 is due to the brittleness inherent in a highly crystalline PVDF polymer and a copolymer of trifluoroethylene. Further worsening is not necessarily desirable for application to an ultrasonic probe applied to a subject.
また、特許文献３に１記載の如くプラズマ放電処理などにより表面加工する場合、化学的に表面を変化させる手法では有機圧電材料の脆性を助長してしまう場合があり、物理的エッチングを行っても十分な接着性を得られない場合があった。特に数ＭＨｚの振動を発振し受信する超音波振動探触子として長時間使用した場合に接着性が著しく低下する場合があった。
Further, when surface processing is performed by plasma discharge treatment or the like as described in Patent Document 3, the method of chemically changing the surface may promote the brittleness of the organic piezoelectric material, and even if physical etching is performed. In some cases, sufficient adhesion could not be obtained. In particular, when used for a long time as an ultrasonic vibration probe that oscillates and receives vibrations of several MHz, the adhesiveness may be significantly reduced.
一方、特許文献４の如く有機結合材層を設けることで見かけ上の接着性を向上させることはできるが、有機結合材層により超音波の受信可能帯域が狭くなり、超音波探触子として長時間使用した場合には接着性が低下する場合もあった。
On the other hand, it is possible to improve the apparent adhesiveness by providing an organic binder layer as in Patent Document 4, but the organic binder layer narrows the receivable band of ultrasonic waves, which makes it long as an ultrasonic probe. When used for a long time, the adhesiveness sometimes deteriorated.
本発明は、上記課題に鑑みなされたものであり、本発明の目的は、有機圧電材料の電極接着性を良好なものとする表面処理の最適条件を提供し、電極金属との接着性に優れ、操作中の摩擦などでの電極はがれ耐性に優れ、加工を行う際の弱い摩擦でも剥離生成の抑制に優れ、圧電性に優れた高周波・広帯域に適した超音波振動子を形成するための有機圧電材料、超音波振動子、それを用いた超音波探触子を提供することにある。
The present invention has been made in view of the above problems, and an object of the present invention is to provide an optimum condition for surface treatment for improving the electrode adhesion of an organic piezoelectric material, and to have excellent adhesion to an electrode metal. , Excellent resistance to electrode peeling due to friction during operation, excellent suppression of delamination even with weak friction during processing, organic to form an ultrasonic transducer with excellent piezoelectricity suitable for high frequency and wide band An object is to provide a piezoelectric material, an ultrasonic transducer, and an ultrasonic probe using the piezoelectric material.
本発明の上記目的は、下記の構成により達成される。
The above object of the present invention is achieved by the following configuration.
１．超音波振動子を形成するための有機圧電材料において、少なくとも一方の表面の算術平均粗さ（Ｒａ）が０．０１μｍ以上０．９μｍ以下であることを特徴とする有機圧電材料。
1. An organic piezoelectric material for forming an ultrasonic transducer, wherein an arithmetic average roughness (Ra) of at least one surface is 0.01 μm or more and 0.9 μm or less.
２．前記有機圧電材料は、フッ化ビニリデンを６０モル％以上９５モル％以下含有する、フッ化ビニリデンとトリフルオロエチレンの共重合体を有することを特徴とする１に記載の有機圧電材料。
2. 2. The organic piezoelectric material according to 1, wherein the organic piezoelectric material has a copolymer of vinylidene fluoride and trifluoroethylene containing 60 to 95 mol% of vinylidene fluoride.
３．１又は２に記載の有機圧電材料の前記一方の表面に接合された電極を有することを特徴とする超音波振動子。
3. An ultrasonic vibrator having an electrode bonded to the one surface of the organic piezoelectric material described in 3.1 or 2.
４．前記電極は、前記有機圧電材料に蒸着されていることを特徴とする３に記載の超音波振動子。
4. 4. The ultrasonic transducer according to 3, wherein the electrode is deposited on the organic piezoelectric material.
５．３又は４に記載の超音波振動子を有することを特徴とする超音波探触子。
An ultrasonic probe comprising the ultrasonic transducer according to 5.3 or 4.
６．入力された電気信号により超音波を被検体に向けて送信する送信用超音波振動子を有し、前記超音波振動子は、前記被検体から受信した超音波を電気信号に変換して出力することを特徴とする５に記載の超音波探触子。
6. An ultrasonic transducer for transmission that transmits an ultrasonic wave toward a subject by an input electric signal, and the ultrasonic transducer converts an ultrasonic wave received from the subject into an electric signal and outputs the electric signal 5. The ultrasonic probe according to 5, wherein
７．前記超音波振動子は、前記送信用超音波振動子の前記被検体側に積層されていることを特徴とする６に記載の超音波探触子。
7. 7. The ultrasonic probe according to claim 6, wherein the ultrasonic transducer is laminated on the subject side of the transmitting ultrasonic transducer.
本発明によれば、有機圧電材料の少なくとも一方の表面の算術平均粗さ（Ｒａ）が０．０１μｍ以上０．９μｍ以下とすることにより、電極金属との接着性に優れ、超音波探触子の操作中の摩擦などでの電極はがれ耐性に優れ、加工を行う際の弱い摩擦でもの剥離生成の抑制に優れ、加工性に優れ、超音波の振動にも耐えうる接着強度を持ち、圧電性に優れた高周波・広帯域に適した超音波振動子を形成するための有機圧電材料、超音波振動子、それを用いた超音波探触子を提供することができる。
According to the present invention, the arithmetic average roughness (Ra) of at least one surface of the organic piezoelectric material is 0.01 μm or more and 0.9 μm or less, so that the adhesive property with the electrode metal is excellent, and the ultrasonic probe. Excellent resistance to electrode peeling due to friction during operation, excellent suppression of delamination generation even with weak friction during processing, excellent workability, adhesive strength that can withstand ultrasonic vibration, and piezoelectricity It is possible to provide an organic piezoelectric material, an ultrasonic transducer, and an ultrasonic probe using the same for forming an ultrasonic transducer suitable for high frequency and wide band.
以下、本発明を実施するための最良の形態について説明するが、本発明はこれらに限定されない。
Hereinafter, the best mode for carrying out the present invention will be described, but the present invention is not limited thereto.
本実施の形態においては、有機圧電材料の少なくとも一方の表面の、好ましくは表裏面の、算術平均粗さ（Ｒａ）が０．０１μｍ以上０．９μｍであることで、電極金属との接着に優れ、操作中の摩擦などでの電極はがれ耐性に優れ、加工を行う際の弱い摩擦での剥離生成の抑制に優れ、加工性に優れ、超音波の振動にも耐えうる接着強度を持ち、圧電性に優れた、高周波・広帯域に適した超音波振動子を形成するための有機圧電材料が得られる。
In the present embodiment, the arithmetic average roughness (Ra) of at least one surface of the organic piezoelectric material, preferably the front and back surfaces, is 0.01 μm or more and 0.9 μm, so that the adhesion to the electrode metal is excellent. Excellent resistance to electrode peeling due to friction during operation, excellent suppression of delamination due to weak friction during processing, excellent workability, adhesive strength that can withstand ultrasonic vibration, and piezoelectricity And an organic piezoelectric material for forming an ultrasonic transducer suitable for high frequency and wide band.
有機圧電材料（フィルム）の表裏面に微細な凹凸を作ることにより、アンカー効果が生じ電極金属との接着性が向上する。
作 る By creating fine irregularities on the front and back surfaces of the organic piezoelectric material (film), an anchor effect is produced and the adhesion to the electrode metal is improved.
なお、有機圧電材料の凹凸を算術平均粗さ（Ｒａ）とするのは、有機圧電材料の接着性は、微小な領域で発生する特異的なキズの影響は比較的受けにくく、電極が接合される接合面全体の凹凸の影響を受けることに起因する。Ｒａ値が０．０１μｍ未満であるとアンカー効果が得られないため接着性が向上せず、０．９μｍを超えると面均一性がよくないため接着性の向上が見られなくなる。
Note that the unevenness of the organic piezoelectric material is defined as the arithmetic average roughness (Ra). The adhesiveness of the organic piezoelectric material is relatively unaffected by specific scratches that occur in minute regions, and the electrodes are joined. This is due to the influence of the unevenness of the entire joint surface. If the Ra value is less than 0.01 μm, the anchor effect cannot be obtained, so that the adhesiveness is not improved. If the Ra value exceeds 0.9 μm, the surface uniformity is not good, and the improvement in the adhesiveness is not observed.
ここで、表面の算術平均粗さ（Ｒａ）とは、粗さ曲線からその平均線の方向にある基準長さだけを抜き取って平均線から測定曲線までの偏差の絶対地を平均した値を意味し、算術平均粗さの測定法はＪＩＳ Ｂ ０６０１に従い、原子間力顕微鏡（ＡＦＭ）を用いて測定し求めることができる。
Here, the arithmetic average roughness (Ra) of the surface means a value obtained by extracting only the reference length in the direction of the average line from the roughness curve and averaging the absolute ground of the deviation from the average line to the measurement curve. The arithmetic average roughness can be measured and determined according to JIS B 0601 using an atomic force microscope (AFM).
（有機圧電材料）
本発明の超音波振動子を構成する圧電材料の構成材料としての有機圧電材料としては低分子材料、高分子材料を問わず採用でき、低分子の有機圧電材料であれば、例えば、フタル酸エステル系化合物、スルフェンアミド系化合物、フェノール骨格を有する有機化合物などが挙げられる。高分子の有機圧電材料であれば、例えば、ポリフッ化ビニリデン、あるいはポリフッ化ビニリデン系共重合体、ポリシアン化ビニリデンあるいはシアン化ビニリデン系共重合体あるはナイロン９、ナイロン１１などの奇数ナイロンや、芳香族ナイロン、脂環族ナイロン、あるいはポリ乳酸や、ポリヒドロキシブチレートなどのポリヒドロキシカルボン酸、セルロース系誘導体、ポリウレアなどが挙げられる。良好な圧電特性、加工性、入手容易性等の観点から、高分子の有機圧電材料、特にフッ化ビニリデンを主成分とする高分子材料であることが好ましい。 (Organic piezoelectric material)
The organic piezoelectric material as the constituent material of the piezoelectric material constituting the ultrasonic vibrator of the present invention can be adopted regardless of whether it is a low molecular material or a high molecular material. Compounds, sulfenamide compounds, organic compounds having a phenol skeleton, and the like. In the case of a high molecular organic piezoelectric material, for example, polyvinylidene fluoride, a polyvinylidene fluoride copolymer, a polyvinylidene cyanide or a vinylidene cyanide copolymer, an odd-numbered nylon such as nylon 9 ornylon 11, or an aromatic Aromatic nylon, alicyclic nylon, polylactic acid, polyhydroxycarboxylic acids such as polyhydroxybutyrate, cellulose derivatives, polyurea and the like. From the viewpoint of good piezoelectric properties, processability, availability, and the like, a polymer organic piezoelectric material, particularly a polymer material mainly composed of vinylidene fluoride is preferable.
本発明の超音波振動子を構成する圧電材料の構成材料としての有機圧電材料としては低分子材料、高分子材料を問わず採用でき、低分子の有機圧電材料であれば、例えば、フタル酸エステル系化合物、スルフェンアミド系化合物、フェノール骨格を有する有機化合物などが挙げられる。高分子の有機圧電材料であれば、例えば、ポリフッ化ビニリデン、あるいはポリフッ化ビニリデン系共重合体、ポリシアン化ビニリデンあるいはシアン化ビニリデン系共重合体あるはナイロン９、ナイロン１１などの奇数ナイロンや、芳香族ナイロン、脂環族ナイロン、あるいはポリ乳酸や、ポリヒドロキシブチレートなどのポリヒドロキシカルボン酸、セルロース系誘導体、ポリウレアなどが挙げられる。良好な圧電特性、加工性、入手容易性等の観点から、高分子の有機圧電材料、特にフッ化ビニリデンを主成分とする高分子材料であることが好ましい。 (Organic piezoelectric material)
The organic piezoelectric material as the constituent material of the piezoelectric material constituting the ultrasonic vibrator of the present invention can be adopted regardless of whether it is a low molecular material or a high molecular material. Compounds, sulfenamide compounds, organic compounds having a phenol skeleton, and the like. In the case of a high molecular organic piezoelectric material, for example, polyvinylidene fluoride, a polyvinylidene fluoride copolymer, a polyvinylidene cyanide or a vinylidene cyanide copolymer, an odd-numbered nylon such as nylon 9 or
具体的には、大きい双極子モーメントをもつＣＦ２基を有する、ポリフッ化ビニリデンの単独重合体又はフッ化ビニリデンを主成分とする共重合体であることが好ましい。なお、共重合体における第二組成分としては、テトラフルオロエチレン、トリフルオロエチレン、ヘキサフルオロプロペン、クロロフルオロエチレン等を用いることができる。
Specifically, it is preferably a homopolymer of polyvinylidene fluoride having a CF 2 group having a large dipole moment or a copolymer having vinylidene fluoride as a main component. In addition, tetrafluoroethylene, trifluoroethylene, hexafluoropropene, chlorofluoroethylene, etc. can be used as the second component in the copolymer.
例えば、フッ化ビニリデン／トリフルオロエチレン共重合体の場合、共重合比によって厚さ方向の電気機械結合定数（圧電効果）が変化する。高周波成分の送受信に好適となる電気機械結合定数が０．２以上の有機圧電材料とするには、フッ化ビニリデンの共重合比が６０～９９モル％であること、更には、８５～９９モル％であることが好ましい。また、超音波振動子として長期に亘って電極の接着強度が低下しないようにするには、フッ化ビニリデンの共重合比が６０モル％以上９５％以下、トリフルオロエチレンの共重合比が５モル％以上４０モル％以下であることがより好ましい。
For example, in the case of vinylidene fluoride / trifluoroethylene copolymer, the electromechanical coupling constant (piezoelectric effect) in the thickness direction varies depending on the copolymerization ratio. In order to obtain an organic piezoelectric material having an electromechanical coupling constant of 0.2 or more that is suitable for transmission and reception of high-frequency components, the copolymerization ratio of vinylidene fluoride is 60 to 99 mol%, and furthermore, 85 to 99 mol. % Is preferred. Also, in order to prevent the adhesive strength of the electrode from decreasing for a long period of time as an ultrasonic vibrator, the copolymerization ratio of vinylidene fluoride is 60 mol% or more and 95% or less, and the copolymerization ratio of trifluoroethylene is 5 mol. % To 40 mol% is more preferable.
なお、フッ化ビニリデンを８５～９９モル％にして、パーフルオロアルキルビニルエーテル、パーフルオロアルコキシエチレン、パーフルオロヘキサエチレン等を１～１５モル％にした有機圧電材料は、超音波探触子に適用した場合において、送信基本波を抑制して、高調波受信の感度を高めることができる。
An organic piezoelectric material containing 85 to 99 mol% of vinylidene fluoride and 1 to 15 mol% of perfluoroalkyl vinyl ether, perfluoroalkoxyethylene, perfluorohexaethylene, etc. was applied to an ultrasonic probe. In some cases, it is possible to suppress the transmission fundamental wave and increase the sensitivity of harmonic reception.
上記有機圧電材料は、セラミックスからなる無機圧電材料に比べ、薄膜化できることからより高周波の送受信に対応した振動子にすることができる点が特徴である。
Since the organic piezoelectric material can be made thinner than an inorganic piezoelectric material made of ceramics, the organic piezoelectric material is characterized in that it can be used as a vibrator corresponding to transmission and reception of higher frequencies.
本実施の形態に係る有機圧電材料は、厚み共振周波数における比誘電率が１０～５０であることが好ましい。比誘電率の調整は、当該有機圧電材料を構成する化合物が有するＣＦ２基やＣＮ基のような極性官能基の数量、組成、重合度等の調整、及び後述する分極処理によって行うことができる。
The organic piezoelectric material according to the present embodiment preferably has a relative dielectric constant of 10 to 50 at the thickness resonance frequency. The relative dielectric constant can be adjusted by adjusting the number, composition, polymerization degree, etc. of polar functional groups such as CF 2 groups and CN groups contained in the compound constituting the organic piezoelectric material, and polarization treatment described later. .
なお、本実施の形態に係る有機圧電材料と、複数の高分子材料を積層させた超音波振動子を構成することもできる。この場合、積層する高分子材料としては、上記の高分子材料の他に下記の比誘電率の比較的低い高分子材料を併用することができる。
Note that an ultrasonic vibrator in which the organic piezoelectric material according to the present embodiment and a plurality of polymer materials are laminated can also be configured. In this case, as the polymer material to be laminated, the following polymer material having a relatively low relative dielectric constant can be used in addition to the above polymer material.
なお、下記の例示において、括弧内の数値は、高分子材料（樹脂）の比誘電率を示す。例えば、メタクリル酸メチル樹脂（３．０）、アクリルニトリル樹脂（４．０）、アセテート樹脂（３．４）、アニリン樹脂（３．５）、アニリンホルムアルデヒド樹脂（４．０）、アミノアルキル樹脂（４．０）、アルキッド樹脂（５．０）、ナイロン－６－６（３．４）、エチレン樹脂（２．２）、エポキシ樹脂（２．５）、塩化ビニル樹脂（３．３）、塩化ビニリデン樹脂（３．０）、尿素ホルムアルデヒド樹脂（７．０）、ポリアセタール樹脂（３．６）、ポリウレタン（５．０）、ポリエステル樹脂（２．８）、ポリエチレン（低圧）（２．３）、ポリエチレンテレフタレート（２．９）、ポリカーポネート樹脂（２．９）、メラミン樹脂（５．１）、メラミンホルムアルデヒド樹脂（８．０）、酢酸セルロース（３．２）、酢酸ビニル樹脂（２．７）、スチレン樹脂（２．３）、スチレンブタジエンゴム（３．０）、スチロール樹脂（２．４）、フッ化エチレン樹脂（２．０）等を用いることができる。
In the following examples, the numerical value in parentheses indicates the relative dielectric constant of the polymer material (resin). For example, methyl methacrylate resin (3.0), acrylonitrile resin (4.0), acetate resin (3.4), aniline resin (3.5), aniline formaldehyde resin (4.0), aminoalkyl resin ( 4.0), alkyd resin (5.0), nylon-6-6 (3.4), ethylene resin (2.2), epoxy resin (2.5), vinyl chloride resin (3.3), chloride Vinylidene resin (3.0), urea formaldehyde resin (7.0), polyacetal resin (3.6), polyurethane (5.0), polyester resin (2.8), polyethylene (low pressure) (2.3), Polyethylene terephthalate (2.9), polycarbonate resin (2.9), melamine resin (5.1), melamine formaldehyde resin (8.0), cellulose acetate (3.2), acetic acid Sulfonyl resin (2.7), styrene resins (2.3), styrene-butadiene rubber (3.0), styrene resin (2.4), it can be used polytetrafluoroethylene (2.0) or the like.
なお、上記比誘電率の低い高分子材料は、圧電特性を調整するため、或いは有機圧電体膜の物理的強度を付与するため等の種々の目的に応じて適切なものを選択することが好ましい。
The polymer material having a low relative dielectric constant is preferably selected in accordance with various purposes such as adjusting the piezoelectric characteristics or imparting the physical strength of the organic piezoelectric film. .
（有機圧電材料の作製方法）
本実施の形態に係る有機圧電材料は、上記高分子材料を主たる構成成分として種々の方法で作製することができる。 (Production method of organic piezoelectric material)
The organic piezoelectric material according to the present embodiment can be manufactured by various methods using the polymer material as a main constituent.
本実施の形態に係る有機圧電材料は、上記高分子材料を主たる構成成分として種々の方法で作製することができる。 (Production method of organic piezoelectric material)
The organic piezoelectric material according to the present embodiment can be manufactured by various methods using the polymer material as a main constituent.
有機圧電材料の作製方法としては、溶融法、流延法など一般的な方法を用いることができる。ポリフッ化ビニリデン－トリフルオロエチレン共重合体の場合、フィルム状にしたのみで自発分極をもつ結晶型を有することが知られているが、さらに特性を上げるには、分子配列を揃える処理を加えることが有用である。手段としては、延伸製膜、分極処理などが挙げられる。
As a method for producing the organic piezoelectric material, a general method such as a melting method or a casting method can be used. In the case of a polyvinylidene fluoride-trifluoroethylene copolymer, it is known that it has a crystalline form with spontaneous polarization only when it is made into a film, but in order to further improve the characteristics, a process for aligning the molecular arrangement should be added. Is useful. Examples of means include stretching film formation and polarization treatment.
延伸製膜の方法については、種々の公知の方法を採用することができる。例えば、上記高分子材料をエチルメチルケトン（ＭＥＫ）などの有機溶媒に溶解した液をガラス板などの基板上に流延し、常温にて溶媒を乾燥させ、所望の厚さのフィルムを得て、このフィルムを室温で所定の倍率の長さに延伸する。当該延伸は、所定形状の有機圧電体膜が破壊されない程度に一軸・二軸方向に延伸することができる。延伸倍率は２～１０倍、好ましくは２～６倍である。
As the stretching film forming method, various known methods can be employed. For example, a solution obtained by dissolving the above polymer material in an organic solvent such as ethyl methyl ketone (MEK) is cast on a substrate such as a glass plate, and the solvent is dried at room temperature to obtain a film having a desired thickness. The film is stretched to a predetermined length at room temperature. The stretching can be performed in uniaxial and biaxial directions so that the organic piezoelectric film having a predetermined shape is not broken. The draw ratio is 2 to 10 times, preferably 2 to 6 times.
なお、フッ化ビニリデン－トリフルオロエチレン共重合体および／またはフッ化ビニリデン－テトラフルオロエチレン共重合体において、２３０℃における溶融流動速度（Ｍｅｌｔ Ｆｌｏｗ Ｒａｔｅ）が０．０３ｇ／ｍｉｎ以下である。より好ましくは、０．０２ｇ／ｍｉｎ以下、更に好ましくは、０．０１ｇ／ｍｉｎである高分子圧電体を使用すると高感度な圧電体の薄膜が得られる。
Incidentally, in the vinylidene fluoride-trifluoroethylene copolymer and / or the vinylidene fluoride-tetrafluoroethylene copolymer, the melt flow rate at 230 ° C. (Melt Flow Rate) is 0.03 g / min or less. More preferably, a high-sensitivity piezoelectric thin film can be obtained by using a polymer piezoelectric body of 0.02 g / min or less, more preferably 0.01 g / min.
延伸製膜された有機圧電体材料に対しては、弛緩処理を施すことができる。弛緩処理により有機圧電体材料の可撓性、脆弱化、平面性、等を改善することができる。
Relaxing treatment can be applied to the stretched organic piezoelectric material. By the relaxation treatment, the flexibility, weakening, flatness, etc. of the organic piezoelectric material can be improved.
弛緩処理とは、熱処理およびその終了後室温まで冷却される過程でフィルム状の有機圧電体材料にかかる収縮ないしは膨張しようとする力に追従しながら、有機圧電体材料両端の応力を変化させることである。弛緩処理は、有機圧電体材料が弛むことで平面性が保てなくなったり、応力が大きくなって破断したりしない限り、応力を緩和させるように縮めても、さらに張力をかける方向に延伸しない程度に広げても良い。本発明における弛緩処理量は、延伸した方向をプラスと定めた場合、長さにして１０％程度、フィルムが冷却中に伸びる場合は、たるみに追従するように１５％程度、負の弛緩処理を行うのが好ましい。
The relaxation treatment is a process in which the stress at both ends of the organic piezoelectric material is changed while following the contraction or expansion force applied to the film-like organic piezoelectric material in the process of cooling to room temperature after the heat treatment. is there. Relaxation treatment does not stretch in the direction in which tension is applied even if it is shrunk so as to relieve stress unless the organic piezoelectric material relaxes and flatness cannot be maintained or the stress increases and breaks. It may be spread over. The amount of relaxation treatment in the present invention is about 10% in length when the stretched direction is determined to be positive, and about 15% in order to follow slack when the film stretches during cooling. It is preferred to do so.
弛緩処理の方法としては、有機圧電体材料のフィルム面内に効率的かつ均一に熱を与えるためにチャック、クリップなどで端部を支持して、有機圧電体材料の融点よりも１０℃低い温度を上限とした温度付近下に置くことが好ましい。ポリフッ化ビニリデンを主成分とする有機圧電材料の場合、融点が１５０℃～１８０℃にあることから、１００℃以上、１４０℃以下の温度で熱処理をすることが好ましい。またその時間は、３０分以上行うことで効果が発現し長ければ長いほど結晶成長が促進するが時間とともに飽和することから、現実的には１０時間程度、長くとも一昼夜程度である。
As a relaxation treatment method, in order to efficiently and uniformly heat the film surface of the organic piezoelectric material, the end is supported by a chuck, a clip, etc., and the temperature is 10 ° C. lower than the melting point of the organic piezoelectric material. It is preferable to place it near the temperature with the upper limit being. In the case of an organic piezoelectric material mainly composed of polyvinylidene fluoride, the melting point is 150 ° C. to 180 ° C., and therefore, it is preferable to perform heat treatment at a temperature of 100 ° C. or more and 140 ° C. or less. In addition, the longer the time is, the longer the effect is expressed and the longer the effect is exhibited, the longer the crystal growth is promoted. However, since the saturation occurs with time, it is practically about 10 hours and at most about day and night.
（有機圧電材料表裏面の粗面加工）
本実施の形態に係る有機圧電材料の表裏面のＲａを０．０１～０．９μｍとする表面処理については、種々の公知の方法を採用することができる。例えば、大気圧プラズマ処理、減圧プラズマ処理、コロナ放電処理、精密研磨などにより粗面加工することができる。表面加工処理はこれらに限定されるものではないが、有機圧電材料表面に化学的変化を起こさない不活性ガス雰囲気下で行われるのがより好ましい。上記の表面処理において、処理時間、印加する電圧、研磨材の粒径等を適宜選択することでＲａを所望のものとすることができる。 (Rough surface processing of organic piezoelectric material front and back)
Various known methods can be employed for the surface treatment of setting the Ra on the front and back surfaces of the organic piezoelectric material according to the present embodiment to 0.01 to 0.9 μm. For example, rough surface processing can be performed by atmospheric pressure plasma treatment, reduced pressure plasma treatment, corona discharge treatment, precision polishing, and the like. The surface processing is not limited to these, but is preferably performed in an inert gas atmosphere that does not cause a chemical change on the surface of the organic piezoelectric material. In the above surface treatment, Ra can be made desired by appropriately selecting the treatment time, the voltage to be applied, the particle size of the abrasive, and the like.
本実施の形態に係る有機圧電材料の表裏面のＲａを０．０１～０．９μｍとする表面処理については、種々の公知の方法を採用することができる。例えば、大気圧プラズマ処理、減圧プラズマ処理、コロナ放電処理、精密研磨などにより粗面加工することができる。表面加工処理はこれらに限定されるものではないが、有機圧電材料表面に化学的変化を起こさない不活性ガス雰囲気下で行われるのがより好ましい。上記の表面処理において、処理時間、印加する電圧、研磨材の粒径等を適宜選択することでＲａを所望のものとすることができる。 (Rough surface processing of organic piezoelectric material front and back)
Various known methods can be employed for the surface treatment of setting the Ra on the front and back surfaces of the organic piezoelectric material according to the present embodiment to 0.01 to 0.9 μm. For example, rough surface processing can be performed by atmospheric pressure plasma treatment, reduced pressure plasma treatment, corona discharge treatment, precision polishing, and the like. The surface processing is not limited to these, but is preferably performed in an inert gas atmosphere that does not cause a chemical change on the surface of the organic piezoelectric material. In the above surface treatment, Ra can be made desired by appropriately selecting the treatment time, the voltage to be applied, the particle size of the abrasive, and the like.
（分極処理）
本実施の形態に係る有機圧電材料に対しては、分極処理を施すことができる。分極処理方法としては、従来公知の直流電圧印加処理、交流電圧印加処理又はコロナ放電処理等の方法が適用され得る。 (Polarization treatment)
The organic piezoelectric material according to the present embodiment can be subjected to polarization treatment. As the polarization processing method, a conventionally known method such as DC voltage application processing, AC voltage application processing, or corona discharge processing can be applied.
本実施の形態に係る有機圧電材料に対しては、分極処理を施すことができる。分極処理方法としては、従来公知の直流電圧印加処理、交流電圧印加処理又はコロナ放電処理等の方法が適用され得る。 (Polarization treatment)
The organic piezoelectric material according to the present embodiment can be subjected to polarization treatment. As the polarization processing method, a conventionally known method such as DC voltage application processing, AC voltage application processing, or corona discharge processing can be applied.
例えば、コロナ放電処理法による場合には、コロナ放電処理は、市販の高電圧電源と電極からなる装置を使用して処理することができる。
For example, in the case of the corona discharge treatment method, the corona discharge treatment can be performed by using a commercially available apparatus comprising a high voltage power source and electrodes.
放電条件は、機器や処理環境により異なるので適宜条件を選択することが好ましい。高電圧電源の電圧としては－１～－２０ｋＶ、電流としては１～８０ｍＡ、電極間距離としては、１～１０ｃｍが好ましく、印加電圧は、０．５～２．０ＭＶ／ｍであることが好ましい。
Since the discharge conditions vary depending on the equipment and the processing environment, it is preferable to select the conditions appropriately. The voltage of the high voltage power source is preferably −1 to −20 kV, the current is 1 to 80 mA, the distance between the electrodes is preferably 1 to 10 cm, and the applied voltage is preferably 0.5 to 2.0 MV / m. .
放電電極としては、従来から用いられている針状電極、線状電極（ワイヤー電極）、網状電極が好ましいが、本発明ではこれらに限定されるものではない。
As the discharge electrode, a needle electrode, a wire electrode (wire electrode), and a mesh electrode that have been conventionally used are preferable, but the present invention is not limited thereto.
なお、後述する超音波振動子の製造工程において、有機圧電材料の表裏面いずれか一方に設置される電極の形成後に分極処理するようにしてもよい。
In addition, in the manufacturing process of the ultrasonic vibrator to be described later, the polarization treatment may be performed after forming the electrodes placed on either the front or back surface of the organic piezoelectric material.
（超音波振動子）
本実施の形態に係る有機圧電材料を適用した超音波振動子について説明する。 (Ultrasonic transducer)
An ultrasonic transducer to which the organic piezoelectric material according to the present embodiment is applied will be described.
本実施の形態に係る有機圧電材料を適用した超音波振動子について説明する。 (Ultrasonic transducer)
An ultrasonic transducer to which the organic piezoelectric material according to the present embodiment is applied will be described.
超音波振動子は、フィルム状の有機圧電材料を挟んで一対の電極を配設して構成され、複数の振動子を例えば１次元配列して超音波探触子が構成される。
The ultrasonic transducer is configured by arranging a pair of electrodes with a film-like organic piezoelectric material interposed therebetween, and an ultrasonic probe is configured by arranging a plurality of transducers, for example, one-dimensionally.
本実施の形態に係る有機圧電材料を有する超音波振動子は、有機圧電材料の両面上又は片面上に電極を形成し、その圧電体膜を分極処理することによって作製されるものである。当該電極は、金（Ａｕ）、白金（Ｐｔ）、銀（Ａｇ）、パラジウム（Ｐｄ）、銅（Ｃｕ）、ニッケル（Ｎｉ）、スズ（Ｓｎ）などを主体とした電極材料を用いて形成する。
The ultrasonic transducer having the organic piezoelectric material according to the present embodiment is manufactured by forming electrodes on both sides or one side of the organic piezoelectric material 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. .
電極の形成に際しては、まず、チタン（Ｔｉ）やクロム（Ｃｒ）などの下地金属をスパッタ法により０．０２～１．０μｍの厚さに形成する。その後、上記金属元素を主体とする金属及びそれらの合金からなる金属材料、さらには必要に応じ一部絶縁材料をスパッタ法、その他の適当な方法で１～１０μｍの厚さに形成する。これらの電極形成はスパッタ法以外でも微粉末の金属粉末と低融点ガラスを混合した導電ペーストをスクリーン印刷やディッピング法、溶射法で形成することもできる。
When forming the electrode, 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. Thereafter, a metal material mainly composed of the above metal element and a metal material thereof, 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.
さらに、圧電体膜の両面に形成した電極間に、所定の電圧を供給し、圧電体膜を分極することで圧電素子が得られる。
Furthermore, a piezoelectric element can be obtained by supplying a predetermined voltage between the electrodes formed on both surfaces of the piezoelectric film to polarize the piezoelectric film.
なお、有機圧電材料が弛緩処理をされた方向と矩形状の超音波振動子の長辺方向とが平行になるように超音波振動子が作製されることが、有機圧電材料の膜厚を均一にでき、安定した圧電性能が得られる点で好ましい。
It should be noted that the thickness of the organic piezoelectric material can be made uniform so that the direction in which the organic piezoelectric material is relaxed and the long side direction of the rectangular ultrasonic transducer are parallel to each other. This is preferable in that stable piezoelectric performance can be obtained.
（超音波診断装置）
本実施の形態に係る有機圧電材料を適用した超音波探触子及び超音波診断装置について説明する。 (Ultrasonic diagnostic equipment)
An ultrasonic probe and an ultrasonic diagnostic apparatus to which the organic piezoelectric material according to the present embodiment is applied will be described.
本実施の形態に係る有機圧電材料を適用した超音波探触子及び超音波診断装置について説明する。 (Ultrasonic diagnostic equipment)
An ultrasonic probe and an ultrasonic diagnostic apparatus to which the organic piezoelectric material according to the present embodiment is applied will be described.
図１は、本実施形態における超音波診断装置の外観図であり、図２は、本実施形態における超音波診断装置の電気的な構成を示すブロック図である。
FIG. 1 is an external view of the ultrasonic diagnostic apparatus according to the present embodiment, and FIG. 2 is a block diagram illustrating an electrical configuration of the ultrasonic diagnostic apparatus according to the present embodiment.
超音波診断装置Ｓは、図示しない被検体に対して超音波を送信すると共に、被検体で反射した超音波の反射波を受信する超音波探触子２と、超音波探触子２とケーブル３を介して接続され、超音波探触子２へケーブル３を介して電気信号の送信信号を送信することによって超音波探触子２に被検体に対して超音波を送信させると共に、超音波探触子２で受信された被検体内からの超音波の反射波に応じて超音波探触子２で生成された電気信号の受信信号に基づいて被検体内の内部状態を超音波画像として画像化する超音波診断装置本体１とを備える。
The ultrasonic diagnostic apparatus S transmits an ultrasonic wave to a subject (not shown) and receives an ultrasonic wave reflected from the subject, an ultrasonic probe 2, and a cable. 3, and by transmitting a transmission signal of an electrical signal to the ultrasonic probe 2 via the cable 3, the ultrasonic probe 2 transmits ultrasonic waves to the subject, Based on the received signal of the electric signal generated by the ultrasonic probe 2 in accordance with the reflected wave of the ultrasonic wave from the inside of the subject received by the probe 2, the internal state in the subject is converted into an ultrasonic image. And an ultrasonic diagnostic apparatus main body 1 for imaging.
超音波診断装置本体１は、例えば、図２に示すように、診断開始を指示するコマンドや被検体の個人情報等のデータを入力する操作入力部１１と、超音波探触子２へケーブル３を介して電気信号の送信信号を供給して超音波探触子２に超音波を発生させる送信回路１２と、超音波探触子２からケーブル３を介して電気信号の受信信号を受信する受信回路１３と、受信回路１３で受信した受信信号に基づいて被検体内の内部状態の画像（超音波画像）を生成する画像処理部１４と、画像処理部１４で生成された被検体内の内部状態の画像を表示する表示部１５と、これら操作入力部１１、送信回路１２、受信回路１３、画像処理部１４および表示部１５を当該機能に応じて制御することによって超音波診断装置Ｓの全体制御を行う制御部１６とを備える。
For example, as shown in FIG. 2, the ultrasonic diagnostic apparatus main body 1 includes an operation input unit 11 for inputting data such as a command for starting diagnosis and personal information of a subject, and a cable 3 to the ultrasonic probe 2. A transmission circuit 12 for supplying a transmission signal of an electrical signal via the transmitter and generating an ultrasonic wave in the ultrasonic probe 2 and reception for receiving a reception signal of the electrical signal from the ultrasonic probe 2 via the cable 3 The circuit 13, an image processing unit 14 that generates an image (ultrasonic image) of the internal state in the subject based on the reception signal received by the receiving circuit 13, and the internal part in the subject generated by the image processing unit 14 The ultrasonic diagnostic apparatus S as a whole is controlled by controlling the display unit 15 that displays the state image and the operation input unit 11, the transmission circuit 12, the reception circuit 13, the image processing unit 14, and the display unit 15 according to the function. Control unit 16 that performs control Equipped with a.
超音波探触子２は、複数の無機圧電素子と複数の有機圧電素子とを備えている。無機圧電素子はそれぞれ、無機圧電材料を備えて成り、圧電現象を利用することによって電気信号と超音波信号との間で相互に信号を変換することができる複数の無機圧電素子と、本実施の形態に係る有機圧電材料を備えた超音波振動子である有機圧電素子は、圧電現象を利用することによって電気信号と超音波信号との間で相互に信号を変換することができる有機圧電素子とを備えている。
The ultrasonic probe 2 includes a plurality of inorganic piezoelectric elements and a plurality of organic piezoelectric elements. Each of the inorganic piezoelectric elements includes an inorganic piezoelectric material, and a plurality of inorganic piezoelectric elements capable of mutually converting signals between an electric signal and an ultrasonic signal by using a piezoelectric phenomenon, and the present embodiment An organic piezoelectric element that is an ultrasonic vibrator including an organic piezoelectric material according to a form includes an organic piezoelectric element that can mutually convert a signal between an electrical signal and an ultrasonic signal by using a piezoelectric phenomenon. It has.
図３は、本実施形態の超音波診断装置における超音波探触子の構成を示す模式的な断面図である。
FIG. 3 is a schematic cross-sectional view showing the configuration of the ultrasonic probe in the ultrasonic diagnostic apparatus of the present embodiment.
超音波探触子２Ａは、平板状の音響制動部材２３と、この音響制動部材２３の一方主面上に積層された複数の無機圧電素子２２と、これら複数の無機圧電素子２２上に積層された中間層２６と、この中間層２６上に積層される複数の有機圧電素子２１と、この有機圧電素子２１上に積層される音響整合層２７と、これら複数の無機圧電素子２２及び複数の有機圧電素子２１における隙間に充填される音響吸収材２４とを備える。
The ultrasonic probe 2 </ b> A is laminated on the flat acoustic braking member 23, the plurality of inorganic piezoelectric elements 22 stacked on one main surface of the acoustic braking member 23, and the plurality of inorganic piezoelectric elements 22. The intermediate layer 26, the plurality of organic piezoelectric elements 21 stacked on the intermediate layer 26, the acoustic matching layer 27 stacked on the organic piezoelectric element 21, the plurality of inorganic piezoelectric elements 22 and the plurality of organic layers And an acoustic absorber 24 filled in a gap in the piezoelectric element 21.
音響制動部材２３は、超音波を吸収する材料から構成され、複数の無機圧電素子２２から音響吸収部材２３方向へ放射される超音波を吸収するものである。
The acoustic braking member 23 is made of a material that absorbs ultrasonic waves, and absorbs ultrasonic waves radiated from the plurality of inorganic piezoelectric elements 22 toward the acoustic absorbing member 23.
複数の無機圧電素子２２における各無機圧電素子２２は、無機圧電材料から構成される圧電体２０１１における互いに対向する両面にそれぞれ電極２０２１、２０３１を備えて構成される。複数の無機圧電素子２２は、互いに所定の間隔を空けて平面視にて２次元アレイ状に音響制動部材２３上に配列されている。複数の無機圧電素子２２は、超音波の反射波を受信するように構成されてもよいが、本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓでは、超音波を送信するように構成されている。すなわち、無機圧電素子２２は送信用超音波振動子として機能するものである。より具体的には、複数の無機圧電素子２２には、送信回路１２からケーブル３を介して電気信号が入力される。この電気信号は、無機圧電素子２２の電極２０２１と電極２０３１とに入力される。複数の無機圧電素子２２は、この電気信号を超音波信号に変換することによってこの超音波信号を送信する。
Each inorganic piezoelectric element 22 in the plurality of inorganic piezoelectric elements 22 includes electrodes 2021 and 2031 on opposite surfaces of a piezoelectric body 2011 made of an inorganic piezoelectric material. The plurality of inorganic piezoelectric elements 22 are arranged on the acoustic braking member 23 in a two-dimensional array in plan view with a predetermined interval therebetween. The plurality of inorganic piezoelectric elements 22 may be configured to receive reflected ultrasonic waves, but the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment transmit ultrasonic waves. It is configured. That is, the inorganic piezoelectric element 22 functions as an ultrasonic transducer for transmission. More specifically, an electrical signal is input to the plurality of inorganic piezoelectric elements 22 from the transmission circuit 12 via the cable 3. This electrical signal is input to the electrodes 2021 and 2031 of the inorganic piezoelectric element 22. The plurality of inorganic piezoelectric elements 22 transmit this ultrasonic signal by converting this electric signal into an ultrasonic signal.
音響吸収材２４は、超音波を吸収する材料から構成され、これら複数の無機圧電素子２２及び有機圧電素子２１の相互干渉を低減するためのものである。音響吸収材２４によって各無機圧電素子２２及び有機圧電素子２１間におけるクロストークの低減が可能となる。
The acoustic absorber 24 is made of a material that absorbs ultrasonic waves, and is for reducing mutual interference between the plurality of inorganic piezoelectric elements 22 and organic piezoelectric elements 21. The acoustic absorber 24 can reduce crosstalk between the inorganic piezoelectric elements 22 and the organic piezoelectric elements 21.
中間層２６は、複数の無機圧電素子２２と有機圧電素子２１とを積層するための部材であり、複数の無機圧電素子２２と有機圧電素子２１との音響インピーダンスを整合させるものである。
The intermediate layer 26 is a member for laminating the plurality of inorganic piezoelectric elements 22 and the organic piezoelectric elements 21, and matches the acoustic impedance between the plurality of inorganic piezoelectric elements 22 and the organic piezoelectric elements 21.
有機圧電素子２１は、本実施の形態に係る有機圧電材料から成る圧電体１０１と、この圧電体１０１における互いに対向する両面にそれぞれ電極１０２、１０３を備える。複数の有機圧電素子２１は、無機圧電素子２２と同様に、互いに所定の間隔を空けて平面視にて２次元アレイ状に中間層２６上に配列されている。
The organic piezoelectric element 21 includes a piezoelectric body 101 made of an organic piezoelectric material according to the present embodiment, and electrodes 102 and 103 on both surfaces of the piezoelectric body 101 facing each other. Similar to the inorganic piezoelectric element 22, the plurality of organic piezoelectric elements 21 are arranged on the intermediate layer 26 in a two-dimensional array in plan view at a predetermined interval.
複数の有機圧電素子２１は、一体的なシート状の有機圧電材料の表裏面に公知の方法で電極となる金属を蒸着して、音響制動部材２３上の複数の無機圧電素子２２に積層された中間層２６上に接着した後、ダイシングソーで複数の無機圧電素子２２と同じ２次元アレイ状になるように、中間層２６とともに切断されることで個々に分離される。
The plurality of organic piezoelectric elements 21 are laminated on the plurality of inorganic piezoelectric elements 22 on the acoustic braking member 23 by vapor-depositing a metal serving as an electrode on the front and back surfaces of an integral sheet-like organic piezoelectric material by a known method. After bonding on the intermediate layer 26, they are separated individually by cutting together with the intermediate layer 26 so as to form the same two-dimensional array as the plurality of inorganic piezoelectric elements 22 with a dicing saw.
有機圧電素子２１は、超音波を送信するように構成されてもよいが、本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓでは、超音波の反射波を受信するように構成されている。より具体的には、有機圧電素子２１は、反射波の超音波信号が受信され、この超音波信号を電気信号に変換することによってこの電気信号を出力する。この電気信号は、有機圧電素子２１における電極１０２と電極１０３とから出力される。この電気信号は、ケーブル３を介して受信回路１３へ出力される。
The organic piezoelectric element 21 may be configured to transmit ultrasonic waves, but the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment are configured to receive ultrasonic reflected waves. ing. More specifically, the organic piezoelectric element 21 receives an ultrasonic signal of a reflected wave, and outputs the electric signal by converting the ultrasonic signal into an electric signal. This electrical signal is output from the electrode 102 and the electrode 103 in the organic piezoelectric element 21. This electrical signal is output to the receiving circuit 13 via the cable 3.
音響整合層２７は、無機圧電素子２２の音響インピーダンスと被検体の音響インピーダンスとの整合をとると共に、有機圧電素子２１の音響インピーダンスと被検体の音響インピーダンスとの整合をとる部材である。そして、音響整合層２７は、円弧状に膨出した形状とされる、被検体に向けて送信される超音波を収束する音響レンズを含んでいる。
The acoustic matching layer 27 is a member that matches the acoustic impedance of the inorganic piezoelectric element 22 and the acoustic impedance of the subject and matches the acoustic impedance of the organic piezoelectric element 21 and the acoustic impedance of the subject. The acoustic matching layer 27 includes an acoustic lens that converges an ultrasonic wave that is transmitted toward the subject, and has an arcuate shape.
本実施の形態に係る超音波探触子２Ａにおいては、有機圧電素子２１は無機圧電素子２２の被検体側（矢示Ｘ方向）に積層されているため、無機圧電素子２２から送信される超音波を至近距離で受けることになる。そのため、圧電体１０１と電極１０２、１０３が、無機圧電素子２１から送信される超音波により剥離が助長される傾向があった。ここで、有機圧電素子２１に本実施の形態に係る有機圧電材料を適用することにより、長期に亘る使用においても、圧電体１０１と電極１０２、１０３の接着強度は維持され、剥離は発生しないものとなる。
In the ultrasonic probe 2A according to the present embodiment, the organic piezoelectric element 21 is stacked on the subject side (in the direction indicated by the arrow X) of the inorganic piezoelectric element 22, so that the ultrasonic wave transmitted from the inorganic piezoelectric element 22 is transmitted. You will receive sound waves at close range. Therefore, the piezoelectric body 101 and the electrodes 102 and 103 tend to be exfoliated by ultrasonic waves transmitted from the inorganic piezoelectric element 21. Here, by applying the organic piezoelectric material according to the present embodiment to the organic piezoelectric element 21, the adhesive strength between the piezoelectric body 101 and the electrodes 102 and 103 is maintained even during long-term use, and no peeling occurs. It becomes.
超音波診断装置Ｓの動作について説明する。
The operation of the ultrasonic diagnostic apparatus S will be described.
操作入力部１１から診断開始の指示が入力されると、制御部１６の制御によって送信回路１２で電気信号の送信信号が生成される。この生成された電気信号の送信信号は、ケーブル３を介して超音波探触子２へ供給される。より具体的には、この電気信号の送信信号は、超音波探触子２における複数の無機圧電素子２２へそれぞれ供給される。この電気信号の送信信号は、例えば、所定の周期で繰り返される電圧パルスである。複数の無機圧電素子２２は、それぞれ、この電気信号の送信信号が供給されることによってその厚み方向に伸縮し、この電気信号の送信信号に応じて超音波振動する。この超音波振動によって、複数の無機圧電素子２２は、中間層２６、有機圧電素子２１および音響整合層２７を介して超音波を放射する。超音波探触子２が被検体に例えば当接されていると、これによって超音波探触子２から被検体に対して超音波が送信される。
When a diagnosis start instruction is input from the operation input unit 11, the transmission circuit 12 generates an electric signal transmission signal under the control of the control unit 16. The generated electrical signal transmission signal is supplied to the ultrasonic probe 2 via the cable 3. More specifically, this electrical signal transmission signal is supplied to each of the plurality of inorganic piezoelectric elements 22 in the ultrasonic probe 2. The electric signal transmission signal is, for example, a voltage pulse repeated at a predetermined cycle. Each of the plurality of inorganic piezoelectric elements 22 expands and contracts in the thickness direction when supplied with the transmission signal of the electric signal, and ultrasonically vibrates according to the transmission signal of the electric signal. Due to this ultrasonic vibration, the plurality of inorganic piezoelectric elements 22 radiate ultrasonic waves through the intermediate layer 26, the organic piezoelectric element 21 and the acoustic matching layer 27. When the ultrasonic probe 2 is in contact with the subject, for example, ultrasonic waves are transmitted from the ultrasonic probe 2 to the subject.
なお、超音波探触子２は、被検体の表面上に当接して用いられてもよいし、被検体の内部に挿入して、例えば、生体の体腔内に挿入して用いられてもよい。
Note that the ultrasound probe 2 may be used in contact with the surface of the subject, or may be used by being inserted into the subject, for example, being inserted into a body cavity of a living body. .
この被検体に対して送信された超音波は、被検体内部における音響インピーダンスが異なる１または複数の境界面で反射され、超音波の反射波となる。この反射波には、送信された超音波の周波数（基本波の基本周波数）成分だけでなく、基本周波数の整数倍の高調波の周波数成分も含まれる。例えば、基本周波数の２倍、３倍および４倍などの第２高調波成分、第３高調波成分および第４高調波成分なども含まれる。この反射波の超音波は、超音波探触子２で受信される。より具体的には、この反射波の超音波は、音響整合層２７を介して有機圧電素子２１で受信され、有機圧電素子２１で機械的な振動が電気信号に変換されて受信信号として取り出される。この取り出された電気信号の受信信号は、ケーブル３を介して制御部１６で制御される受信回路１３で受信される。
The ultrasonic wave transmitted to the subject is reflected at one or a plurality of boundary surfaces having different acoustic impedances inside the subject, and becomes a reflected wave of the ultrasonic wave. This reflected wave includes not only the frequency component of the transmitted ultrasonic wave (fundamental fundamental frequency) but also the frequency component of a harmonic that is an integral multiple of the fundamental frequency. For example, second harmonic components such as twice, three times, and four times the fundamental frequency, third harmonic components, and fourth harmonic components are also included. The ultrasonic wave of the reflected wave is received by the ultrasonic probe 2. More specifically, the ultrasonic wave of the reflected wave is received by the organic piezoelectric element 21 through the acoustic matching layer 27, and mechanical vibration is converted into an electric signal by the organic piezoelectric element 21 and is extracted as a received signal. . The extracted reception signal of the electrical signal is received by the receiving circuit 13 controlled by the control unit 16 via the cable 3.
ここで、上述において、各無機圧電素子２２から順次に超音波が被検体に向けて送信され、被検体で反射した超音波が有機圧電素子２１で受信される。
Here, in the above description, ultrasonic waves are sequentially transmitted from the inorganic piezoelectric elements 22 toward the subject, and the ultrasonic waves reflected by the subject are received by the organic piezoelectric elements 21.
そして、画像処理部１４は、制御部１６の制御によって、受信回路１３で受信した受信信号に基づいて、送信から受信までの時間や受信強度などから被検体内の内部状態の画像（超音波画像）を生成し、表示部１５は、制御部１６の制御によって、画像処理部１４で生成された被検体内の内部状態の画像を表示する。本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓでは、上述したように基本波の高調波が受信されるので、ハーモニックイメージング技術によって超音波画像を形成することが可能となる。このため、本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓは、より高精度な超音波画像の提供が可能となる。そして、比較的パワーの大きい第２および第３高調波が受信されるので、より鮮明な超音波画像の提供が可能となる。
Then, the image processing unit 14 controls the image of the internal state in the subject (ultrasonic image) based on the reception signal received by the receiving circuit 13 based on the reception signal received by the reception circuit 13 based on the time from transmission to reception and the reception intensity. The display unit 15 displays the image of the internal state in the subject generated by the image processing unit 14 under the control of the control unit 16. In the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment, since the harmonics of the fundamental wave are received as described above, an ultrasonic image can be formed by the harmonic imaging technique. For this reason, the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment can provide a more accurate ultrasonic image. Since the second and third harmonics having relatively high power are received, a clearer ultrasonic image can be provided.
また、本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓでは、複数の無機圧電素子２２は、超音波を送信するように構成されている。このように送信パワーを大きくすることが可能な無機圧電素子２２によって超音波信号が送信されるので、超音波探触子２Ａおよび超音波診断装置Ｓは、比較的簡単な構造で送信パワーを大きくすることができる。したがって、本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓは、被検体内で発生する高調波のエコーを超音波探触子２Ａで得るのに十分な音圧で基本波を送信することが必要なハーモニックイメージング技術に好適であり、より高精度な超音波画像の提供が可能となる。
Moreover, in the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment, the plurality of inorganic piezoelectric elements 22 are configured to transmit ultrasonic waves. Since the ultrasonic signal is transmitted by the inorganic piezoelectric element 22 capable of increasing the transmission power in this way, the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S increase the transmission power with a relatively simple structure. can do. Therefore, the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment transmit the fundamental wave with a sound pressure sufficient to obtain the echo of the harmonic generated in the subject with the ultrasonic probe 2A. This is suitable for the harmonic imaging technique that needs to be performed, and it is possible to provide a more accurate ultrasonic image.
また、本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓでは、有機圧電素子２１は、超音波の反射波を受信するように構成されている。一般に、無機圧電材料の圧電素子は、基本波の周波数に対する２倍程度の周波数の超音波しか受信することができないが、有機圧電材料の圧電素子は、基本波の周波数に対する例えば４～５倍程度の周波数の超音波を受信することができ、受信周波数帯域の広帯域化に適している。このような超音波を広い周波数に亘って受信可能な特性を持つ有機圧電素子２１によって超音波信号が受信されるので、本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓは、比較的簡単な構造で周波数帯域を広帯域にすることができる。このため、本実施形態における超音波探触子２Ａおよび超音波診断装置Ｓは、基本波の三次以上の高調波を受信することが必要なハーモニックイメージング技術に好適であり、より高精度な超音波画像の提供が可能となる。
In the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment, the organic piezoelectric element 21 is configured to receive an ultrasonic reflected wave. In general, a piezoelectric element made of an inorganic piezoelectric material can receive only an ultrasonic wave having a frequency about twice the frequency of the fundamental wave, but a piezoelectric element made of an organic piezoelectric material is about 4 to 5 times the frequency of the fundamental wave, for example. It is possible to receive an ultrasonic wave having a frequency of 5 and is suitable for widening the reception frequency band. Since the ultrasonic signal is received by the organic piezoelectric element 21 having a characteristic capable of receiving such ultrasonic waves over a wide frequency, the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment are compared. The frequency band can be widened with a simple structure. For this reason, the ultrasonic probe 2A and the ultrasonic diagnostic apparatus S in the present embodiment are suitable for harmonic imaging technology that needs to receive the third and higher harmonics of the fundamental wave, and more accurate ultrasonic waves. Images can be provided.
上記のような超音波診断装置によれば、本発明の圧電特性及び耐熱性に優れかつ高周波・広帯域に適した超音波受信用振動子の特徴を生かして、従来技術と比較して画質とその再現・安定性、特に耐久性が向上した超音波像を得ることができる。
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, particularly durability, can be obtained.
以下、実施例を挙げて本発明を詳細に説明するが、本発明はこれらに限定されない。尚、特に断りない限り、実施例中の「部」あるいは「％」の表示は、「質量部」あるいは「質量％」を表す。
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “part” or “%” in the examples represents “part by mass” or “% by mass”.
実施例１
《有機圧電体膜材料の作製》
欧州特許第６２６，３９６号に記載の方法に従って作製したフッ化ビニリデン（以下、ＶＤＦ）とトリフルオロエチレン（以下、３ＦＥ）のモル比率が７５：２５であるポリフッ化ビニリデン共重合体を、５０℃に加熱したメチルエチルケトン（以下、ＭＥＫ）、Ｎ，Ｎ－ジメチルホルムアミド（以下、ＤＭＦ）の９：１の混合溶媒に溶解した液をガラス板上に流延した。その後、５５℃にて溶媒を乾燥させ、厚さ約１２０μｍのフィルム（有機圧電材料）を得た。 Example 1
<< Production of organic piezoelectric film material >>
A polyvinylidene fluoride copolymer having a molar ratio of vinylidene fluoride (hereinafter referred to as VDF) and trifluoroethylene (hereinafter referred to as 3FE) of 75:25 prepared according to the method described in European Patent No. 626,396 is prepared at 50 ° C. A solution of methyl ethyl ketone (hereinafter referred to as MEK) and N, N-dimethylformamide (hereinafter referred to as DMF) in a 9: 1 mixed solvent was cast on a glass plate. Thereafter, the solvent was dried at 55 ° C. to obtain a film (organic piezoelectric material) having a thickness of about 120 μm.
《有機圧電体膜材料の作製》
欧州特許第６２６，３９６号に記載の方法に従って作製したフッ化ビニリデン（以下、ＶＤＦ）とトリフルオロエチレン（以下、３ＦＥ）のモル比率が７５：２５であるポリフッ化ビニリデン共重合体を、５０℃に加熱したメチルエチルケトン（以下、ＭＥＫ）、Ｎ，Ｎ－ジメチルホルムアミド（以下、ＤＭＦ）の９：１の混合溶媒に溶解した液をガラス板上に流延した。その後、５５℃にて溶媒を乾燥させ、厚さ約１２０μｍのフィルム（有機圧電材料）を得た。 Example 1
<< Production of organic piezoelectric film material >>
A polyvinylidene fluoride copolymer having a molar ratio of vinylidene fluoride (hereinafter referred to as VDF) and trifluoroethylene (hereinafter referred to as 3FE) of 75:25 prepared according to the method described in European Patent No. 626,396 is prepared at 50 ° C. A solution of methyl ethyl ketone (hereinafter referred to as MEK) and N, N-dimethylformamide (hereinafter referred to as DMF) in a 9: 1 mixed solvent was cast on a glass plate. Thereafter, the solvent was dried at 55 ° C. to obtain a film (organic piezoelectric material) having a thickness of about 120 μm.
このフィルムを、室温で一軸方向に４倍の長さで延伸した後、延伸した長さを保ったまま１３５℃で１時間熱処理した後、自然冷却させた。得られた熱処理後のフィルム１の膜厚は４３μｍであった。
The film was stretched 4 times in a uniaxial direction at room temperature, then heat-treated at 135 ° C. for 1 hour while maintaining the stretched length, and then naturally cooled. The film thickness of the obtained film 1 after the heat treatment was 43 μm.
《有機圧電材料体試料１の作製》
〈プラズマ処理〉
上記にて得られたフィルム１に表裏面が算術平均粗さ（Ｒａ）０．０１μｍになるように大気圧プラズマ処理を、特開２００６－２９９０００号公報に記載の処理装置を用いて、５秒間不活性ガス（アルゴン）を使用して、施した。なお、算術平均粗さの測定法はＪＩＳ Ｂ ０６０１に従い、原子間力顕微鏡（ＡＦＭ）を用いて、平均線からの絶対標準差を測定し、下式に代入して求めた。 << Preparation of OrganicPiezoelectric Material Sample 1 >>
<Plasma treatment>
Thefilm 1 obtained above is subjected to atmospheric pressure plasma treatment so that the front and back surfaces have an arithmetic average roughness (Ra) of 0.01 μm, using a treatment apparatus described in JP-A-2006-299000 for 5 seconds. It was applied using an inert gas (argon). The arithmetic average roughness was measured according to JIS B 0601 by measuring the absolute standard difference from the average line using an atomic force microscope (AFM) and substituting it into the following equation.
〈プラズマ処理〉
上記にて得られたフィルム１に表裏面が算術平均粗さ（Ｒａ）０．０１μｍになるように大気圧プラズマ処理を、特開２００６－２９９０００号公報に記載の処理装置を用いて、５秒間不活性ガス（アルゴン）を使用して、施した。なお、算術平均粗さの測定法はＪＩＳ Ｂ ０６０１に従い、原子間力顕微鏡（ＡＦＭ）を用いて、平均線からの絶対標準差を測定し、下式に代入して求めた。 << Preparation of Organic
<Plasma treatment>
The
〈電極有機圧電体の作製〉
プラズマ処理後、プラズマ処理を施したフィルム１の両面に表面抵抗が１Ω以下になるように真空蒸着装置ＪＥＥ－４２０（日本電子データム（株）製）で金、膜厚：５０ｎｍを蒸着して膜厚５０ｎｍの電極を作製した。 <Production of electrode organic piezoelectric material>
After plasma treatment, gold and film thickness: 50 nm are vapor-deposited with a vacuum vapor deposition device JEE-420 (manufactured by JEOL Datum Co., Ltd.) so that the surface resistance is 1Ω or less on both surfaces of the plasma-treatedfilm 1. An electrode having a thickness of 50 nm was produced.
プラズマ処理後、プラズマ処理を施したフィルム１の両面に表面抵抗が１Ω以下になるように真空蒸着装置ＪＥＥ－４２０（日本電子データム（株）製）で金、膜厚：５０ｎｍを蒸着して膜厚５０ｎｍの電極を作製した。 <Production of electrode organic piezoelectric material>
After plasma treatment, gold and film thickness: 50 nm are vapor-deposited with a vacuum vapor deposition device JEE-420 (manufactured by JEOL Datum Co., Ltd.) so that the surface resistance is 1Ω or less on both surfaces of the plasma-treated
つづいて、この電極に室温にて０．１Ｈｚの交流電圧を印可しながら分極処理を行い表裏面に電極を有する有機圧電材料体試料１を得た。
Subsequently, the electrode was subjected to polarization treatment while applying an AC voltage of 0.1 Hz at room temperature to obtain an organic piezoelectric material sample 1 having electrodes on the front and back surfaces.
尚、分極処理は低電圧から行い、最終的に電極間電場が１００ＭＶ／ｍになるまで徐々に電圧をかけていった。
In addition, the polarization process was performed from a low voltage, and the voltage was gradually applied until the electric field between the electrodes finally reached 100 MV / m.
《有機圧電材料体試料２～４の作製》
大気圧プラズマ処理の処理時間を変えて算術平均粗さ（Ｒａ）を０．０５μｍ、０．１μｍ、０．９μｍに変更した以外は有機圧電材料体試料１と同様に行い有機圧電材料体試料２～４を得た。 << Production of organic piezoelectricmaterial body samples 2 to 4 >>
The organicpiezoelectric material sample 2 is the same as the organic piezoelectric material sample 1 except that the arithmetic mean roughness (Ra) is changed to 0.05 μm, 0.1 μm, and 0.9 μm by changing the processing time of the atmospheric pressure plasma processing. ~ 4 were obtained.
大気圧プラズマ処理の処理時間を変えて算術平均粗さ（Ｒａ）を０．０５μｍ、０．１μｍ、０．９μｍに変更した以外は有機圧電材料体試料１と同様に行い有機圧電材料体試料２～４を得た。 << Production of organic piezoelectric
The organic
《有機圧電材料体試料５の作製》
上記フィルム１にプラズマ処理を行わずに、直接、金を蒸着して電極を作製し、続いて分極処理を有機圧電材料体試料１と同様にして行うことにより有機圧電材料体試料５を得た。 << Production of Organic Piezoelectric Material Sample 5 >>
An organic piezoelectric material sample 5 was obtained by directly depositing gold on thefilm 1 without performing plasma treatment to produce an electrode, and subsequently performing a polarization treatment in the same manner as the organic piezoelectric material sample 1. .
上記フィルム１にプラズマ処理を行わずに、直接、金を蒸着して電極を作製し、続いて分極処理を有機圧電材料体試料１と同様にして行うことにより有機圧電材料体試料５を得た。 << Production of Organic Piezoelectric Material Sample 5 >>
An organic piezoelectric material sample 5 was obtained by directly depositing gold on the
《有機圧電材料体試料６、７の作製》
大気圧プラズマ処理の処理時間を代変えて算術平均粗さ（Ｒａ）を０．００５μｍ、１．５μｍに代えた以外は有機圧電材料体試料１と同様に行い有機圧電材料体試料６、７を得た。 << Preparation of organic piezoelectric material body samples 6 and 7 >>
The organic piezoelectric material samples 6 and 7 were prepared in the same manner as the organicpiezoelectric material sample 1 except that the arithmetic mean roughness (Ra) was changed to 0.005 μm and 1.5 μm by changing the processing time of the atmospheric pressure plasma processing. Obtained.
大気圧プラズマ処理の処理時間を代変えて算術平均粗さ（Ｒａ）を０．００５μｍ、１．５μｍに代えた以外は有機圧電材料体試料１と同様に行い有機圧電材料体試料６、７を得た。 << Preparation of organic piezoelectric material body samples 6 and 7 >>
The organic piezoelectric material samples 6 and 7 were prepared in the same manner as the organic
《有機圧電材料体試料８の作製》
有機圧電材料をＰＶＤＦの単重合体の有機圧電フィルム（アトケム社製）とした以外は、有機圧電材料体試料１～４、６、７と同様にして、但し、ＰＶＤＦの単重合体の有機圧電フィルム（アトケム社製）に大気圧プラズマ処理を施し、有機圧電材料体試料８を得た。算術平均粗さ（Ｒａ）は０．１μｍであった。 << Production of Organic Piezoelectric Material Sample 8 >>
The organic piezoelectric material is the same as the organicpiezoelectric material samples 1 to 4, 6, and 7 except that the organic piezoelectric material is a PVDF homopolymer organic piezoelectric film (manufactured by Atchem). The film (manufactured by Atchem) was subjected to atmospheric pressure plasma treatment to obtain an organic piezoelectric material sample 8. The arithmetic average roughness (Ra) was 0.1 μm.
有機圧電材料をＰＶＤＦの単重合体の有機圧電フィルム（アトケム社製）とした以外は、有機圧電材料体試料１～４、６、７と同様にして、但し、ＰＶＤＦの単重合体の有機圧電フィルム（アトケム社製）に大気圧プラズマ処理を施し、有機圧電材料体試料８を得た。算術平均粗さ（Ｒａ）は０．１μｍであった。 << Production of Organic Piezoelectric Material Sample 8 >>
The organic piezoelectric material is the same as the organic
《評価》
電極蒸着作製直後の接着性と、超音波洗浄機に浸して超音波を当てた後の接着性を測定した。 <Evaluation>
The adhesiveness immediately after electrode deposition production and the adhesiveness after immersing in an ultrasonic cleaner and applying ultrasonic waves were measured.
電極蒸着作製直後の接着性と、超音波洗浄機に浸して超音波を当てた後の接着性を測定した。 <Evaluation>
The adhesiveness immediately after electrode deposition production and the adhesiveness after immersing in an ultrasonic cleaner and applying ultrasonic waves were measured.
（蒸着電極作製直後の接着性）
接着性は９０度剥離試験で測定を行った。具体的には試料１～８について蒸着した、電極上表面に接着剤を塗布し、カプトンシリコン製テープ（パーマセル社製商品名：カプトンテープ（Ｐ２２１）、メーカー名：パーマセル、仕様厚さ２５μｍ、シリコーン系）を圧着させして熱処理後、シリコーン製カプトンテープを接着面の法線方向に剥離させた時の剥離に必要な最大力を測定し、下記評価基準に則り接着性として評価した。
評価基準
Ａ：２．０Ｎ／ｃｍ以上
Ｂ：１．５Ｎ／ｃｍ以上～２．０Ｎ／ｃｍ未満
Ｃ：１．０Ｎ／ｃｍ以上～１．５Ｎ／ｃｍ未満
Ｄ：０．５Ｎ／ｃｍ以上～１．０Ｎ／ｃｍ未満
（超音波照射後の接着性）
試料１～８を超音波洗浄機（ＡＳ ＯＮＥ製 品名ＵＳ ＣＬＬＥＡＮＥＲ 型番ＵＳ－５Ｒ）を利用して水中で二時間超音波を当てた後、上記の９０度剥離試験を行い上記同評価基準に則り評価した。 (Adhesiveness immediately after deposition electrode production)
Adhesion was measured by a 90 degree peel test. Specifically, adhesive was applied to the surface of the electrode deposited onSamples 1 to 8, and Kapton Silicone tape (trade name: Kapton Tape (P221), manufactured by Permacel), manufacturer name: Permacel, specification thickness 25 μm, silicone The maximum force required for peeling when the silicone-made Kapton tape was peeled in the normal direction of the adhesive surface was measured after the heat treatment by pressure bonding, and evaluated as adhesiveness according to the following evaluation criteria.
Evaluation criteria A: 2.0 N / cm or more B: 1.5 N / cm or more to less than 2.0 N / cm C: 1.0 N / cm or more to less than 1.5 N / cm D: 0.5 N / cm or more to 1 Less than 0 N / cm (Adhesiveness after ultrasonic irradiation)
Samples 1 to 8 were subjected to ultrasonic cleaning in water for 2 hours using an ultrasonic cleaning machine (AS ONE product name US CLLEANER model number US-5R) and then subjected to the above 90-degree peel test and in accordance with the same evaluation criteria. evaluated.
接着性は９０度剥離試験で測定を行った。具体的には試料１～８について蒸着した、電極上表面に接着剤を塗布し、カプトンシリコン製テープ（パーマセル社製商品名：カプトンテープ（Ｐ２２１）、メーカー名：パーマセル、仕様厚さ２５μｍ、シリコーン系）を圧着させして熱処理後、シリコーン製カプトンテープを接着面の法線方向に剥離させた時の剥離に必要な最大力を測定し、下記評価基準に則り接着性として評価した。
評価基準
Ａ：２．０Ｎ／ｃｍ以上
Ｂ：１．５Ｎ／ｃｍ以上～２．０Ｎ／ｃｍ未満
Ｃ：１．０Ｎ／ｃｍ以上～１．５Ｎ／ｃｍ未満
Ｄ：０．５Ｎ／ｃｍ以上～１．０Ｎ／ｃｍ未満
（超音波照射後の接着性）
試料１～８を超音波洗浄機（ＡＳ ＯＮＥ製 品名ＵＳ ＣＬＬＥＡＮＥＲ 型番ＵＳ－５Ｒ）を利用して水中で二時間超音波を当てた後、上記の９０度剥離試験を行い上記同評価基準に則り評価した。 (Adhesiveness immediately after deposition electrode production)
Adhesion was measured by a 90 degree peel test. Specifically, adhesive was applied to the surface of the electrode deposited on
Evaluation criteria A: 2.0 N / cm or more B: 1.5 N / cm or more to less than 2.0 N / cm C: 1.0 N / cm or more to less than 1.5 N / cm D: 0.5 N / cm or more to 1 Less than 0 N / cm (Adhesiveness after ultrasonic irradiation)
（圧電性）
［電極耐久性］
［有機圧電材料体の評価方法］
上記のようにして得られた電極付の有機圧電材料体試料１～８の両面の電極にリード線を付け、アジレントテクノロジー社製インピーダンスアナライザ４２９４Ａを用いて、２５℃雰囲気下において、４０Ｈｚから１１０ＭＨｚまで等間隔で６００点周波数掃引した。厚み共振周波数における比誘電率の値を求めた。同様に、厚み共振周波数付近の抵抗値のピーク周波数Ｐ、コンダクタンスのピーク周波数Ｓをそれぞれ求めたとき、下記式にて電気機械結合定数ｋｔを求めた。 (Piezoelectric)
[Electrode durability]
[Method for evaluating organic piezoelectric material]
Lead electrodes are attached to the electrodes on both sides of the organic piezoelectricmaterial body samples 1 to 8 with electrodes obtained as described above, and an impedance analyzer 4294A manufactured by Agilent Technologies is used, and an atmosphere of 25 ° C., from 40 Hz to 110 MHz. The frequency was swept at 600 points at equal intervals. The value of the relative dielectric constant at the thickness resonance frequency was obtained. Similarly, when the peak frequency P of the resistance value near the thickness resonance frequency and the peak frequency S of the conductance were obtained, the electromechanical coupling constant kt was obtained by the following equation.
［電極耐久性］
［有機圧電材料体の評価方法］
上記のようにして得られた電極付の有機圧電材料体試料１～８の両面の電極にリード線を付け、アジレントテクノロジー社製インピーダンスアナライザ４２９４Ａを用いて、２５℃雰囲気下において、４０Ｈｚから１１０ＭＨｚまで等間隔で６００点周波数掃引した。厚み共振周波数における比誘電率の値を求めた。同様に、厚み共振周波数付近の抵抗値のピーク周波数Ｐ、コンダクタンスのピーク周波数Ｓをそれぞれ求めたとき、下記式にて電気機械結合定数ｋｔを求めた。 (Piezoelectric)
[Electrode durability]
[Method for evaluating organic piezoelectric material]
Lead electrodes are attached to the electrodes on both sides of the organic piezoelectric
ｋｔ＝（α／ｔａｎ（α））１／２ ただし、α＝（π／２）×（Ｓ／Ｐ）
インピーダンスアナライザを用いて厚み共振周波数から電気機械結合定数を求める方法としては、電子情報技術産業協会規格ＪＥＩＴＡ ＥＭ－４５０１（旧ＥＭＡＳ－６１００）圧電セラミック振動子の電気的試験方法に記載の円盤状振動子の厚みたて振動４．２．６項に準拠している。 kt = (α / tan (α)) 1/2 where α = (π / 2) × (S / P)
As a method for obtaining an electromechanical coupling constant from a thickness resonance frequency using an impedance analyzer, a disk-like vibration described in the electrical information testing method of the JEITA EM-4501 (formerly EMAS-6100) piezoelectric ceramic vibrator of the Japan Electronics and Information Technology Industries Association The thickness of the child is in accordance with the section 4.2.6.
インピーダンスアナライザを用いて厚み共振周波数から電気機械結合定数を求める方法としては、電子情報技術産業協会規格ＪＥＩＴＡ ＥＭ－４５０１（旧ＥＭＡＳ－６１００）圧電セラミック振動子の電気的試験方法に記載の円盤状振動子の厚みたて振動４．２．６項に準拠している。 kt = (α / tan (α)) 1/2 where α = (π / 2) × (S / P)
As a method for obtaining an electromechanical coupling constant from a thickness resonance frequency using an impedance analyzer, a disk-like vibration described in the electrical information testing method of the JEITA EM-4501 (formerly EMAS-6100) piezoelectric ceramic vibrator of the Japan Electronics and Information Technology Industries Association The thickness of the child is in accordance with the section 4.2.6.
下記評価基準に則り圧電性として評価した。
評価基準
○：０．２以上
×：０．２未満
結果を表１に示す。 The piezoelectricity was evaluated according to the following evaluation criteria.
Evaluation criteria ○: 0.2 or more ×: less than 0.2 The results are shown in Table 1.
評価基準
○：０．２以上
×：０．２未満
結果を表１に示す。 The piezoelectricity was evaluated according to the following evaluation criteria.
Evaluation criteria ○: 0.2 or more ×: less than 0.2 The results are shown in Table 1.
表１から明らかなように、本発明の場合、算術平均粗さ（Ｒａ）を０．０１～０．９μｍにすることにより接着性は向上した。また、表面処理による圧電性の低下も見られなかった。
As is clear from Table 1, in the case of the present invention, the adhesiveness was improved by setting the arithmetic average roughness (Ra) to 0.01 to 0.9 μm. In addition, there was no decrease in piezoelectricity due to the surface treatment.
これに対し比較の場合、試料７のように算術平均粗さ（Ｒａ）が０．９μｍよりも大きい場合には面内均一性が崩れ接着性の低下及び圧電性の低下が見られることがわかる。
On the other hand, in the case of comparison, when the arithmetic average roughness (Ra) is larger than 0.9 μm as in Sample 7, it is understood that the in-plane uniformity is lost and the adhesiveness and piezoelectricity are reduced. .
またＰＶＤＦの単重合体である試料８よりも、ＶＤＦと３ＦＥのモル比率が７５：２５であるポリフッ化ビニリデン共重合体を使用した試料の方が、蒸着直後の接着性が高いのに加え、超音波照射による接着性の低下が少ないことも見られる。
In addition, the sample using the polyvinylidene fluoride copolymer having a molar ratio of VDF and 3FE of 75:25 is higher than the sample 8 which is a PVDF homopolymer, in addition to the higher adhesion immediately after the deposition, It is also seen that there is little decrease in adhesion due to ultrasonic irradiation.
１ 超音波診断装置本体
２、２Ａ 超音波探触子
３ ケーブル
１１ 操作入力部
１２ 送信回路
１３ 受信回路
１４ 画像処理部
１５ 表示部
１６ 制御部
Ｓ 超音波診断装置
２１ 有機圧電素子
２２ 無機圧電素子
２３ 音響制動部材
２４ 音響吸収材
２６ 中間層
２７ 音響整合層
１０１ 圧電体
１０２ 電極
１０３ 電極
２０１１ 圧電体
２０２１ 電極
２０３１ 電極 DESCRIPTION OFSYMBOLS 1 Ultrasonic diagnostic apparatus main body 2, 2A Ultrasonic probe 3 Cable 11 Operation input part 12 Transmission circuit 13 Reception circuit 14 Image processing part 15 Display part 16 Control part S Ultrasonic diagnostic apparatus 21 Organic piezoelectric element 22 Inorganic piezoelectric element 23 Acoustic braking member 24 Acoustic absorber 26 Intermediate layer 27 Acoustic matching layer 101 Piezoelectric body 102 Electrode 103 Electrode 2011 Piezoelectric body 2021 Electrode 2031 Electrode
２、２Ａ 超音波探触子
３ ケーブル
１１ 操作入力部
１２ 送信回路
１３ 受信回路
１４ 画像処理部
１５ 表示部
１６ 制御部
Ｓ 超音波診断装置
２１ 有機圧電素子
２２ 無機圧電素子
２３ 音響制動部材
２４ 音響吸収材
２６ 中間層
２７ 音響整合層
１０１ 圧電体
１０２ 電極
１０３ 電極
２０１１ 圧電体
２０２１ 電極
２０３１ 電極 DESCRIPTION OF
Claims (7)
- 超音波振動子を形成するための有機圧電材料において、少なくとも一方の表面の算術平均粗さ（Ｒａ）が０．０１μｍ以上０．９μｍ以下であることを特徴とする有機圧電材料。 An organic piezoelectric material for forming an ultrasonic transducer, wherein an arithmetic average roughness (Ra) of at least one surface is 0.01 μm or more and 0.9 μm or less.
- 前記有機圧電材料は、フッ化ビニリデンを６０モル％以上９５モル％以下含有する、フッ化ビニリデンとトリフルオロエチレンの共重合体を有することを特徴とする請求項１に記載の有機圧電材料。 2. The organic piezoelectric material according to claim 1, wherein the organic piezoelectric material has a copolymer of vinylidene fluoride and trifluoroethylene containing 60 to 95 mol% of vinylidene fluoride.
- 請求項１又は２に記載の有機圧電材料の前記一方の表面に接合された電極を有することを特徴とする超音波振動子。 An ultrasonic transducer comprising an electrode bonded to the one surface of the organic piezoelectric material according to claim 1.
- 前記電極は、前記有機圧電材料に蒸着されていることを特徴とする請求項３に記載の超音波振動子。 The ultrasonic transducer according to claim 3, wherein the electrode is deposited on the organic piezoelectric material.
- 請求項３又は４に記載の超音波振動子を有することを特徴とする超音波探触子。 An ultrasonic probe comprising the ultrasonic transducer according to claim 3.
- 入力された電気信号により超音波を被検体に向けて送信する送信用超音波振動子を有し、前記超音波振動子は、前記被検体から受信した超音波を電気信号に変換して出力することを特徴とする請求項５に記載の超音波探触子。 An ultrasonic transducer for transmission that transmits an ultrasonic wave toward a subject by an input electric signal, and the ultrasonic transducer converts an ultrasonic wave received from the subject into an electric signal and outputs the electric signal The ultrasonic probe according to claim 5.
- 前記超音波振動子は、前記送信用超音波振動子の前記被検体側に積層されていることを特徴とする請求項６に記載の超音波探触子。 The ultrasonic probe according to claim 6, wherein the ultrasonic transducer is stacked on the subject side of the ultrasonic transducer for transmission.
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| JP2008-299242 | 2008-11-25 |
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| JP2019067908A (en) * | 2017-09-29 | 2019-04-25 | 株式会社クレハ | Piezoelectric film and method of manufacturing film |
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