JP5459216B2 - Organic piezoelectric materials, ultrasonic transducers and ultrasonic probes - Google Patents

Description

  The present invention relates to an organic piezoelectric material and an ultrasonic probe, and more particularly to an organic piezoelectric material containing a compound having a mesogenic group, an ultrasonic transducer using the organic piezoelectric material, and an ultrasonic probe.

  Conventionally, acoustic devices such as microphones and speaker diaphragms, various thermal sensors, pressure sensors, measuring devices such as infrared detectors, ultrasonic probe, vibration sensors that detect mutations such as genes and proteins with high sensitivity, etc. Organic piezoelectric materials having piezoelectricity and pyroelectricity that can be used to convert heat and mechanical stimulation into electrical energy are known.

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

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

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

  Although there is a report using a ferroelectric liquid crystal compound as a piezoelectric material (see, for example, Patent Document 4), in the previous reports, the types of polarization groups in the liquid crystal molecules are limited, and spontaneous polarization and piezoelectricity are sufficient. However, a material satisfying the performance required as a piezoelectric material has not yet been found.

JP-A-6-216422 JP-A-2-284485 Japanese Patent Laid-Open No. 5-31399 JP 7-115230 A

  The present invention has been made in view of the above-mentioned problems and circumstances, and the object thereof is an organic piezoelectric material having piezoelectricity and pyroelectricity that has excellent piezoelectric characteristics and can convert heat and mechanical stimulation into electrical energy. In particular, it is to provide an organic piezoelectric material ultrasonic transducer which is excellent in piezoelectric characteristics due to high orientation and is thermally stable, and an ultrasonic probe using the same.

  The above object of the present invention can be achieved by the following configuration.

  1. An organic piezoelectric material comprising a compound represented by the following general formula (1):

Formula _{(1) R 1 -Q-A} 1 -Y-Z
[Wherein, R ₁ represents an alkyl group having 1 to 20 carbon atoms . Q represents a single bond or an oxygen atom. A ₁ represents a mesogenic group. Y represents a urea group (—NHCONH—), a thiourea group (—NHCSNH—), or a urethane group (—NHCOO— ) . Z is a group selected from an aliphatic group having 1 to 25 carbon atoms, an aromatic group, and a heterocyclic group, and represents a substituent containing an asymmetric carbon . ]

2 . 2. The organic piezoelectric material as described in 1 above, further comprising a compound represented by the following general formula (2).

[In General Formula (2), R ₂₁ represents a hydrogen atom or a methyl group. p represents an integer of 5 or more. B ₁ represents an alkylene group or an oxyalkylene group, B ₂ represents a mesogenic group, and Z ₂ represents a group selected from an aliphatic group having 1 to 25 carbon atoms, an aromatic group, and a heterocyclic group. ]
3 . An ultrasonic vibrator having an organic piezoelectric film containing the organic piezoelectric material described in 1 or 2 above.

4 . 4. The ultrasonic transducer according to item 3 , wherein the ultrasonic transducer is an ultrasonic receiving transducer.

5 . An ultrasonic probe comprising: an ultrasonic transmission transducer; and the ultrasonic transducer described in 4 above.

  According to the present invention, it is possible to provide an organic piezoelectric material having piezoelectricity and pyroelectricity that is excellent in piezoelectric characteristics and capable of converting heat and mechanical stimulation into electrical energy. Particularly, the piezoelectric properties are excellent due to high orientation, In addition, a thermally stable organic piezoelectric material, an ultrasonic transducer using the same, and an ultrasonic probe could be provided.

It is a conceptual diagram which shows the structure of the principal part of the ultrasonic medical image diagnostic apparatus of embodiment of this invention.

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

  In the present invention, by using the compound represented by the general formula (1) for the organic piezoelectric material, the orientation is high, and not only the piezoelectricity and pyroelectricity are excellent, but also thermally stable. It can be effectively used as a highly versatile organic piezoelectric material.

<Compound represented by formula (1)>
In the general formula (1), R ₁ represents a group selected from an aliphatic group, an aromatic group, and a heterocyclic group. The “aliphatic group” in the present specification means an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, and an alkynyl group, which are substituted or unsubstituted, respectively.

Specific examples of the aliphatic group represented by R ₁ include an alkyl group (methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, Dodecyl group, octadecyl group, etc.), cycloalkyl group (cyclohexyl group, cyclopentyl group etc.), alkenyl group, cycloalkenyl group, alkynyl group (propargyl group etc.) can be mentioned.

  Specific examples of the aromatic group include phenyl group, naphthyl group, anthracenyl group and the like, and specific examples of the heterocyclic group include lysyl group, thiazolyl group, oxazolyl group, imidazolyl group, furyl group, pyrrolyl group, pyrazinyl. A group, a pyrimidinyl group, a pyridazinyl group, a selenazolyl group, a sriphoranyl group, a piperidinyl group, a pyrazolyl group, a tetrazolyl group, and the like. Further, these groups may be further substituted with these groups.

R ₁ is preferably an aliphatic group having 1 to 20 carbon atoms, more preferably an alkyl group having 3 to 20 carbon atoms, and still more preferably an alkyl group having 6 to 18 carbon atoms.

Q represents a single bond or an oxygen atom. In the present invention, the single bond means that R ₁ and A ₁ are directly bonded.

A ₁ represents a mesogenic group. The mesogenic group in the present invention is a rigid unit essential for a compound exhibiting liquid crystallinity, and refers to a group in which two or more ring structures are connected directly or with a bonding group.

The mesogen group represented by A ₁ is, for example, a group represented by the following formula (A-1) ~ (A -10).

  Preferable mesogenic groups are groups between Q and Y represented by the following formulas (a-1) to (a-20).

Y represents a urea group (—NHCONH—), a thiourea group (—NHCSNH—), a urethane group (—NHCOO—), a sulfamoyl group (—SO ₂ NH—), or a carbonate group (—OCOO—). Y is preferably a urea group, a thiourea group, or a urethane group.

  Examples of the substituent represented by Z include an alkyl group having 1 to 25 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, cyclohexyl group, etc.), halogen Alkyl group (trifluoromethyl group, perfluorooctyl group etc.), cycloalkyl group (cyclohexyl group, cyclopentyl group etc.), alkynyl group (propargyl group etc.), aromatic group (phenyl group, naphthyl group etc.), heterocyclic ring Groups (pyridyl group, thiazolyl group, oxazolyl group, imidazolyl group, furyl group, pyrrolyl group, pyrazinyl group, pyrimidinyl group, pyridazinyl group, selenazolyl group, triphoranyl group, piperidinyl group, pyrazolyl group, tetrazolyl group, etc.) it can. Further, these groups may be further substituted with these groups.

  Z is preferably a substituent containing an asymmetric carbon, and is not particularly limited as long as it is a substituent containing at least one asymmetric carbon, but is represented by the following general formula (4) or general formula (5). Are preferred.

In the general formula (4), * represents an asymmetric carbon atom. R ₄₁ , R ₄₂ and R ₄₃ each represent a hydrogen atom or a substituent, but each does not become the same group.

Examples of the substituent represented by R ₄₁ , R ₄₂ and R ₄₃ include an alkyl group having 1 to 25 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group). Cyclohexyl group, etc.), halogenated alkyl group (trifluoromethyl group, perfluorooctyl group, etc.), cycloalkyl group (cyclohexyl group, cyclopentyl group etc.), alkynyl group (propargyl group etc.), glycidyl group, acrylate group, methacrylate Group, aromatic group (phenyl group, etc.), heterocyclic group (pyridyl group, thiazolyl group, oxazolyl group, imidazolyl group, furyl group, pyrrolyl group, pyrazinyl group, pyrimidinyl group, pyridazinyl group, selenazolyl group, sriphoranyl group, piperidinyl group , Pyrazolyl group, tetrazolyl group, etc.), halogen source Child (chlorine atom, bromine atom, iodine atom, fluorine atom, etc.), alkoxy group (methoxy group, ethoxy group, propyloxy group, pentyloxy group, cyclopentyloxy group, hexyloxy group, cyclohexyloxy group, etc.), aryloxy group (Phenoxy group etc.), alkoxycarbonyl group (methyloxycarbonyl group, ethyloxycarbonyl group, butyloxycarbonyl group etc.), aryloxycarbonyl group (phenyloxycarbonyl group etc.), sulfonamide group (methanesulfonamide group, ethanesulfone) Amide group, butanesulfonamide group, hexanesulfonamide group, cyclohexanesulfonamide group, benzenesulfonamide group, etc.), sulfamoyl group (aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group) Butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, phenylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc., urethane group (methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, phenylureido group) 2-pyridylureido group), acyl group (acetyl group, propionyl group, butanoyl group, hexanoyl group, cyclohexanoyl group, benzoyl group, pyridinoyl group, etc.), carbamoyl group (aminocarbonyl group, methylaminocarbonyl group, dimethyl group) Aminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), Group (acetamide group, propionamide group, butanamide group, hexaneamide group, benzamide group, etc.), sulfonyl group (methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, phenylsulfonyl group, 2-pyridylsulfonyl group) Etc.), amino group (amino group, ethylamino group, dimethylamino group, butylamino group, cyclopentylamino group, anilino group, 2-pyridylamino group, etc.), cyano group, nitro group, sulfo group, carboxyl group, hydroxyl group, An oxamoyl group can be exemplified. Further, these groups may be further substituted with these groups.

R ₄₁ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, a trifluoromethyl group, or a halogen atom, and still more preferably a methyl group, a trifluoromethyl group, a fluorine atom. Is an atom. R ₄₂ is preferably a methyl group, ethyl group, isopropyl group, n-butyl group, tert-butyl group, hexyl group, octyl group, dodecyl group or the like. R ₄₃ is preferably a hydrogen atom.

In the general formula (5), * represents an asymmetric carbon atom. R ₅₁ , R ₅₂ , R ₅₃ , R ₅₄ , and R ₅₅ each represent a hydrogen atom or a substituent, but R ₅₁ and R ₅₃ , and R ₅₂ , R _54, and R ₅₅ are not the same group. Examples of the substituent represented by R ₅₁ , R ₅₂ , R ₅₃ , R ₅₄ , R ₅₅ are specific examples of the substituent represented by R ₄₁ , R ₄₂ , R ₄₃ in the general formula (4). The substituents mentioned are mentioned.

R ₅₁ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, a trifluoromethyl group, or a halogen atom, still more preferably a methyl group, a trifluoromethyl group, or fluorine. Is an atom. R ₅₃ is preferably a hydrogen atom. R ₅₂ is preferably an alkyl group having 1 to 12 carbon atoms. R ₅₄ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, a trifluoromethyl group, or a halogen atom, and still more preferably a methyl group, an ethyl group, or a trifluoro group. A methyl group and a fluorine atom. R ₅₅ is preferably a hydrogen atom or a fluorine atom.

  Although the specific example of a compound represented by General formula (1) below is given, this invention is not limited to these.

  The compound represented by the general formula (1) can be synthesized by a known method. For example, it can be synthesized by referring to the methods described in JP-A-61-47427, JP-A-5-119304 and the like.

<Compound represented by formula (2)>
In the general formula (2), R ₂₁ represents a hydrogen atom or a methyl group. B ₁ represents an alkylene group or an oxyalkylene group, and B ₂ represents a mesogenic group. The mesogenic group represented by B ₂ has the same meaning as the mesogenic group represented by A ₁ in the general formula (1). p represents an integer of 5 or more.

  p is preferably 5 to 5000, more preferably 5 to 2000, and particularly preferably 5 to 1000.

Specific examples of the substituent represented by Z ₂ include the examples given as specific examples of the substituent represented by Z in the general formula (1). Z ₂ preferably represents a group containing an asymmetric carbon. The group containing an asymmetric carbon represented by Z ₂ is not particularly limited as long as it is a group containing at least one asymmetric carbon, but is preferably represented by the following general formula (6) or general formula (7). It is a substituent represented.

In the general formula (6), * represents an asymmetric carbon atom. R ₆₁ , R ₆₂ and R ₆₃ each represent a hydrogen atom or a substituent, but each does not become the same group. Examples of the substituent represented by R ₆₁ , R ₆₂ and R ₆₃ include the examples given as examples of the substituent represented by R ₄₁ , R ₄₂ and R ₄₃ in the general formula (4).

R ₆₁ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, a trifluoromethyl group, or a halogen atom, and still more preferably a methyl group, a trifluoromethyl group, a fluorine atom. Is an atom. R ₆₂ is preferably a methyl group, ethyl group, isopropyl group, n-butyl group, tert-butyl group, hexyl group, octyl group, decyl group, dodecyl group, octadecyl group or the like. R ₆₃ is preferably a hydrogen atom.

In the general formula (7), * represents an asymmetric carbon atom. R ₇₁ , R ₇₂ , R ₇₃ , R ₇₄ and R ₇₅ each represent a hydrogen atom or a substituent, but R ₇₁ and R ₇₃ , and R ₇₂ , R ₇₄ and R ₇₅ are not the same group. Specific examples of the substituent represented by R ₇₁ , R ₇₂ , R ₇₃ , R ₇₄ and R ₇₅ include the substituents represented by R ₄₁ , R ₄₂ and R ₄₃ in the general formula (4). The substituents mentioned are mentioned.

R ₇₁ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, a trifluoromethyl group, or a halogen atom, still more preferably a methyl group, a trifluoromethyl group, or fluorine. Is an atom. R ₇₂ is preferably methyl, ethyl, isopropyl, n-butyl, tert-butyl, hexyl, octyl, decyl, dodecyl, octadecyl, or the like. R ₇₃ is preferably a hydrogen atom. R ₇₄ is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group, an ethyl group, a trifluoromethyl group, or a halogen atom, and still more preferably a methyl group, an ethyl group, or a trifluoro group. A methyl group and a fluorine atom. R ₇₅ is preferably a hydrogen atom or a fluorine atom.

  The compound represented by the general formula (2) can be synthesized by a known method. Specific examples of the synthesis can be synthesized by referring to the methods described in JP-A-2-124995, JP-A-2-232208, JP-A-5-132558, and the like. Although the specific example of a compound represented by General formula (2) below is given, this invention is not limited to these.

  In the present invention, the mixing ratio of the compound represented by the general formula (1) and the compound represented by the general formula (2) is preferably a general formula for the compound represented by the general formula (1). The proportion of the compound represented by (2) is 0 to 50%, more preferably 0 to 30% from the viewpoint of film forming properties and heat resistance.

<Organic piezoelectric material>
The organic piezoelectric material of the present invention is represented by forming a film containing the compound represented by the general formula (1), or represented by the compound represented by the general formula (1) and the general formula (2). An organic piezoelectric film is formed by forming a film containing a compound or by subjecting the film to further polarization treatment, and is used for an ultrasonic transducer.

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

  On the other hand, when energy (heat) is applied to the piezoelectric film, the magnitude of spontaneous polarization in the piezoelectric film changes accordingly. At this time, the surface charge existing on the surface of the piezoelectric film so as to neutralize the spontaneous polarization cannot respond to the energy change as quickly as the spontaneous polarization. There is a charge corresponding to the change in spontaneous polarization. The generation of electricity associated with this energy change is called pyroelectricity. In particular, in the organic piezoelectric film made of the organic piezoelectric material of the present invention, polarization by freezing orientation of the dipole moment of the main chain or side chain of the polymer Results in greater pyroelectric performance.

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

  In the present invention, preferably, the compound represented by the general formula (1) is applied or formed in a temperature range in which the liquid crystal phase is exhibited or the compound represented by the general formula (2) is in a temperature range in which the liquid crystal phase is exhibited. It is preferable that the formed film may be further subjected to a polarization treatment described later.

  When the compound represented by the general formula (1) is formed on the organic piezoelectric film, an arbitrary non-liquid crystal polymer compound may be mixed to improve the film forming property. Specifically, a thermoplastic resin, a thermosetting resin, or a photocurable resin having a number average molecular weight of 1500 or more is used as the non-liquid crystal polymer compound.

  As the thermoplastic resin, any resin having a number average molecular weight of 1500 or more, preferably 1500 to 100,000 can be used without particular limitation. If the number average molecular weight of the thermoplastic resin is less than 1500, the glass transition temperature is too low, and the mechanical stability of the organic piezoelectric film may be lowered.

  Specific examples of the thermoplastic resin include polyvinyl chloride, polyvinyl bromide, polyvinyl fluoride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride- Vinylidene chloride copolymer, vinyl chloride-butadiene copolymer, vinyl chloride-acrylic acid ester copolymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-styrene-acrylonitrile terpolymer, vinyl chloride-vinylidene chloride- Vinyl acetate copolymers, vinyl halide polymers or copolymers such as polyvinylidene chloride, polytetrafluoroethylene, polytetrafluorochloroethylene, polyvinylidene fluoride; polyvinyl alcohol, polyallyl alcohol, polyvinyl ether, polyallyl ether, etc. Unsaturated alcohol young Or a polymer or copolymer of an ether; a polymer or copolymer of an unsaturated carboxylic acid such as acrylic acid or methacrylic acid; an alcohol residue such as a polyvinyl ester such as polyvinyl acetate or a polyallyl ester such as polyphthalic acid. Polymer or copolymer having an unsaturated bond in the group; in acid residue or acid residue and alcohol residue of polyacrylic acid ester, polymethacrylic acid ester, maleic acid ester or fumaric acid ester polymer, etc. Polymers or copolymers having an unsaturated bond in them; Unsaturated nitrile polymers or copolymers such as acrylonitrile or methacrylonitrile polymers or copolymers, polycyanide vinylidene, malononitrile or fumaronitrile polymers or copolymers Coalescence: polystyrene, poly-α-methylstyrene, poly-p-me Polymers or copolymers of aromatic vinyl compounds such as styrene styrene, styrene-α-methylstyrene copolymer, styrene-p-methylstyrene copolymer, polyvinylbenzene, polyhalogenated styrene; polyvinylpyridine, poly-N- Polymers or copolymers of heterocyclic compounds such as vinylpyrrolidine and poly-N-vinylpyrrolidone; polyester condensates such as polycarbonate, polyamide condensates such as nylon 6, nylon 6,6; maleic anhydride, fumaric anhydride And polymers or copolymers containing an imidized product thereof; heat-resistant organic polymers such as polyamideimide, polyetherimide, polyimide, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyethersulfone, and polyarylate. Of these, polycarbonate, polystyrene, polyacrylate, polymethacrylate, nylon and the like are preferably used.

  As a thermosetting resin, various things including what is marketed, such as an epoxy adhesive and an acrylic adhesive, can be used. As the photo-curable resin, various kinds of resins including those that are commercially available such as an adhesive that is cured by visible light, UV light, electron beam, or the like can be used. These non-liquid crystalline polymer substances may be appropriately selected from the manufacturing method of the organic piezoelectric film and the required durability.

  Specific examples of the heat or photo-curable resin include, for example, epoxy adhesives, acrylic adhesives, unsaturated polyester adhesives, polyurethane adhesives, hot melt adhesives, and elastomer adhesives. .

  As an example of the epoxy adhesive, a bisphenol A type is preferable as the main agent. A main agent in which the bisphenol A portion is a bisphenol compound as shown below can also be used.

  Examples of polyurethane adhesives include methylene bis (p-phenylene diisocyanate), tolylene diisocyanate, hexamethylene diisocyanate, 1-chlorophenyl diisocyanate, 1,5-naphthylene diisocyanate, thiodipropyl diisocyanate, ethylbenzene-α- as an isocyanate component. Examples include 2-di-isocyanate, 4,4,4-triphenylmethane triisocyanate, and the components that react with them include ethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, glycerol, hexanetriol, and xylylene diene. All, lauric acid monoglyceride, stearic acid monoglyceride, oleic acid monoglyceride, polyethylene glycol, polypro Glycol, polyesters, polyamides, and the like.

  The amount of the non-liquid crystalline polymer substance is 2 to 40% by mass, preferably 2 to 20% by mass with respect to the compound represented by the general formula (1). When the amount of the non-liquid crystalline polymer substance is less than 2% by mass, the film forming property of the liquid crystal layer may be deteriorated and the mechanical strength may be insufficient. On the other hand, if it exceeds 40% by mass, unnecessary light scattering may occur, and the performance of the organic piezoelectric film may be deteriorated.

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

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

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

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

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

  The organic piezoelectric film is preferably used together with the substrate to constitute an ultrasonic transducer and an ultrasonic probe.

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

PZT is preferably within the range of the formula of Pb (Zr _1-X Ti _X ) O ₃ (0.47 ≦ X ≦ 1). As deleading, natural or artificial quartz, lithium niobate (LiNbO ₃ ), potassium niobium tantalate [K (Ta, Nb) O ₃ ], barium titanate (BaTiO ₃ ), lithium tantalate (LiTaO ₃ ), or strontium titanate (SrTiO ₃ ). The composition of various ceramic materials can be selected as appropriate in terms of performance.

<Ultrasonic transducer>
The ultrasonic transducer of the present invention has an organic piezoelectric film formed using the organic piezoelectric material of the present invention.

  There are two types of ultrasonic transducers for transmission and reception, but the ultrasonic transducer of the present invention is preferably an ultrasonic reception transducer for reception, together with an ultrasonic transmission transducer, For example, it is preferably used for a probe for an ultrasonic medical image diagnostic apparatus.

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

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

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

<Ultrasound receiving transducer>
The transducer for ultrasonic reception according to the present invention is a transducer that is preferably used for a probe for an ultrasonic medical diagnostic imaging apparatus, and uses the organic piezoelectric material of the present invention as a piezoelectric film constituting the transducer. The formed organic piezoelectric film is used.

The organic piezoelectric material or the organic piezoelectric film used for the ultrasonic receiving vibrator preferably has a relative dielectric constant of 10 to 50 at the thickness resonance frequency. The relative dielectric constant is adjusted by adjusting the number, composition, degree of polymerization, etc. of polar functional groups such as the substituent R, CF ₂ group, and CN group of the compound constituting the organic piezoelectric film, and the polarization described above. It can be done by processing.

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

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

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

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

<electrode>
The ultrasonic transducer of the present invention is preferably produced by forming electrodes on both sides or one side of a piezoelectric film (layer) and polarizing the piezoelectric film. The electrode is formed using an electrode material mainly composed of gold (Au), platinum (Pt), silver (Ag), palladium (Pd), copper (Cu), nickel (Ni), tin (Sn), or the like. .

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

  Furthermore, an ultrasonic transducer can be obtained by supplying a predetermined voltage between the electrodes formed on both surfaces of the piezoelectric film to polarize the piezoelectric film.

(Ultrasonic probe)
An ultrasonic probe of the present invention is a probe for an ultrasonic diagnostic imaging apparatus that includes an ultrasonic transmission transducer and an ultrasonic reception transducer. The ultrasonic receiving transducer according to the invention is used.

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

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

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

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

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

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

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

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

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

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

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

Example 1
Production of Organic Piezoelectric Film A compound represented by the general formula (1) shown in Table 1 or a polymer compound and a general formula (2) is formed on a 25 μm polyimide film whose surface has been subjected to aluminum vapor deposition in advance. The compound was applied so that the dry film pressure was 7 μm and dried to obtain organic piezoelectric film-1 to organic piezoelectric film-18.

  In the same manner, Comparative Piezoelectric Films A to C were produced using Comparative-A, Comparative-B, and Comparative-C shown in Table 2 instead of the compound represented by the general formula (1).

Evaluation of Organic Piezoelectric Film The obtained organic piezoelectric film was evaluated for piezoelectric characteristics while being heated to room temperature and 100 ° C. by a resonance method. The results are shown in Table 1. The piezoelectric characteristics are shown as relative values with respect to the PVDF film measured at room temperature as 100%.

  As is clear from the results shown in Table 1, it can be seen that the piezoelectric properties of the organic piezoelectric film formed from the compound of the present invention are superior to those of the comparative examples and are thermally stable.

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

<Production of laminated resonator for reception>
After attaching an aluminum electrode to the surface of the substrate of the organic piezoelectric film-1 produced in Example 1 by vapor deposition, using a high voltage power supply HARB-20R60 (manufactured by Matsusada Precision Co., Ltd.), 100 MV / m While applying an electric field, the temperature was raised to 200 ° C. at a rate of 5 ° C./min, held at 200 ° C. for 15 minutes, and then slowly cooled to room temperature while applying a voltage to perform poling treatment. A laminated resonator for reception was produced by bonding an organic piezoelectric film-1 subjected to polarization treatment and a polyester film having a thickness of 50 μm with an epoxy adhesive.

  Next, in accordance with an ordinary method, the above-described multi-layer resonator for reception was laminated on the above-mentioned piezoelectric material for transmission, and a backing layer and an acoustic matching layer were installed to produce an ultrasonic probe.

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

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

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

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

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

Claims (5)

An organic piezoelectric material comprising a compound represented by the following general formula (1):
Formula _{(1) R 1 -Q-A} 1 -Y-Z
[Wherein, R ₁ represents an alkyl group having 1 to 20 carbon atoms . Q represents a single bond or an oxygen atom. A ₁ represents a mesogenic group. Y represents a urea group (—NHCONH—), a thiourea group (—NHCSNH—), or a urethane group (—NHCOO— ) . Z is a group selected from an aliphatic group having 1 to 25 carbon atoms, an aromatic group, and a heterocyclic group, and represents a substituent containing an asymmetric carbon . ] The organic piezoelectric material according to claim 1, further comprising a compound represented by the following general formula (2).
[In General Formula (2), R ₂₁ represents a hydrogen atom or a methyl group. p represents an integer of 5 or more. B ₁ represents an alkylene group or an oxyalkylene group, B ₂ represents a mesogenic group, and Z ₂ represents a group selected from an aliphatic group having 1 to 25 carbon atoms, an aromatic group, and a heterocyclic group. ] Ultrasonic transducer, characterized in that it has an organic piezoelectric film containing an organic piezoelectric material according to claim 1 or 2. The ultrasonic transducer according to claim 3 , wherein the ultrasonic transducer is an ultrasonic receiving transducer. An ultrasonic probe comprising an ultrasonic transmission transducer and the ultrasonic transducer according to claim 4 .