EP0100711A2 - Halbwellenwandler unter Anwendung eines aktiven piezoelektrischen Polymerelements - Google Patents

Halbwellenwandler unter Anwendung eines aktiven piezoelektrischen Polymerelements Download PDF

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Publication number
EP0100711A2
EP0100711A2 EP83401485A EP83401485A EP0100711A2 EP 0100711 A2 EP0100711 A2 EP 0100711A2 EP 83401485 A EP83401485 A EP 83401485A EP 83401485 A EP83401485 A EP 83401485A EP 0100711 A2 EP0100711 A2 EP 0100711A2
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EP
European Patent Office
Prior art keywords
sheet
piezoelectric polymer
transducer according
polymer material
transducer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP83401485A
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English (en)
French (fr)
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EP0100711A3 (de
Inventor
Hoang Giang Nguyen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thomson CSF SA
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Filing date
Publication date
Application filed by Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0100711A2 publication Critical patent/EP0100711A2/de
Publication of EP0100711A3 publication Critical patent/EP0100711A3/de
Withdrawn legal-status Critical Current

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    • 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
    • B06B1/0688—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 with foil-type piezoelectric elements, e.g. PVDF
    • B06B1/0692—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 with foil-type piezoelectric elements, e.g. PVDF with a continuous electrode on one side and a plurality of electrodes on the other side
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S310/00—Electrical generator or motor structure
    • Y10S310/80—Piezoelectric polymers, e.g. PVDF

Definitions

  • the present invention relates to transducers of the half-wave type using as active element a sheet of piezoelectric polymer such as polyvinylidene fluoride.
  • Piezoelectric polymer materials offer the advantage of having an acoustic impedance of the same order of magnitude as that of the propagation media. These materials also lend themselves to easy implementation, because they can be molded, thermoformed and take advantage of their flexibility. On the other hand, these materials have relatively weak piezoelectric properties compared for example to those of piezoelectric ceramics and they pose technological problems in particular as regards the poor adhesion of the metal layers intended to materialize the electrodes of a transducer.
  • the half-wave operation makes it possible to approach more perfect reflection of the waves towards the external face of the transducer, since the medium charging the rear face of the transducer has an acoustic impedance typically equal to that of air , that is to say practically zero.
  • a non-dissipative medium does not constitute an appropriate support for depositing electrodes there and it is necessary to turn to another means to resolve the problem posed, that is to say the lack of adhesion of metal deposits on piezoelectric polymers.
  • Half-wave or full-wave configurations are more efficient with regard to bandwidth and sensitivity. They are usually constituted by a piezoelectric polymer sheet whose external face is coupled to the biological medium via a quarter-wave layer of impedance adapter and whose internal face is directly related to the air contained inside. a housing or with a similar medium with low impedance, for example a polymer foam. The distance between the external and internal faces is entirely occupied by the active material, the thickness of which most often corresponds to half a wavelength of the central operating frequency.
  • the invention suggests making the vibrating structure by combining several layers, one of which, active, provides the transducer effect, the others simply playing the role of electrode support.
  • These electrode-carrying layers are integral with the active layer, so that there is a laminated vibrating structure remaining half-wave as a whole although partially active.
  • the layers fixed by bonding on the active layer can have their electrodes in contact with the active layer, the problem of adhesion is resolved by keeping a small spacing of the electrodes and a perfect reflection of the waves at the rear face of the structure. composite, which is in direct relation with a reflective medium of very low acoustic impedance.
  • the subject of the invention is a half-wave type transducer with an active element of piezoelectric polymer comprising at least two electrodes framing a sheet of piezoelectric polymer material mounted on a support; said transducer having an external radiating face intended to be coupled to a medium having an acoustic impedance of the same order as that of said piezoelectric polymer material and an internal face in direct relation inside said support with a reflective medium of acoustic impedance very substantially lower, characterized in that at least the electrode situated on the side of said reflecting medium is formed on a sheet-shaped substrate integral with said sheet of material piezoelectric polymer; the free face of said substrate constituting said internal face.
  • the simplest comprises a single pair of electrodes defining a transducer with a single emissive surface; the other is provided with two sets of electrodes making it possible to define several elementary radiating zones arranged in a network.
  • These electromechanical transducers can be used reversibly either to emit acoustic waves in a medium from an external radiating face coupled to this medium, or to convert incident acoustic radiation from the same medium into electrical voltages.
  • the propagation medium considered is generally a biological medium comparable to a volume of water and, where appropriate, this medium is coupled to the external face of the transducer by a pocket of water.
  • the invention is not limited to the case of coupling with a biological medium, because it applies to any medium whose acoustic impedance is of the same order of magnitude as that of the active or passive materials constituting the vibrating structure .
  • Full-wave operation is similar to half-wave operation, since one of the faces carrying the electrodes is still free to vibrate and to reflect the waves towards the other face.
  • the transducers produced starting from a sheet coated on its two electrode faces the height H to be considered is of course the thickness of the sheet, while the width L is simply deduced from the width of the electrodes.
  • the volume framed by two electrodes represents within a sheet, the elementary volume mentioned above and such volumes can be delimited by electrodes in network to form an alignment of radiating sources.
  • the decoupling between elementary vibratory volumes does not require the presence of special cuts such as notches made in the piezoelectric material.
  • Polystyrene used as a quarter wave transformer is a material used to adapt the impedance of polyvinylidene fluoride to that of water.
  • Polyethylene terephthalate has an acoustic impedance close to that of polyvinylidene fluoride and it constitutes a suitable substrate for metallic deposits having good adhesion.
  • FIG. 1 an isometric view can be seen of an electromechanical transducer produced in accordance with the invention.
  • This transducer comprises a base 1 comprising a central recess 2.
  • a thin sheet 3 of polyethylene terephthalate is bonded by its periphery to the base 1.
  • Deposits of electrodes 4, 5, 7 and 8 are made on the upper face of the sheet 3.
  • These deposits form in the middle of sheet 3 a network of parallel conductive strips which overhang the recess 2.
  • These conductive strips are covered by a sheet 6 of piezoelectric polymer, for example polyvinylidene fluoride.
  • the sheet 6 is bonded to the sheet 3 and carries on its upper face a counter-electrode 9 which cooperates with each of the conductive strips in a network so as to delimit elementary volumes of piezoelectric polymer which represent elementary radiating sources.
  • the electrodes 4, 5, 7 and 8 are extended on the sheet 3 outside the rectangular area covered by the sheet 6, to allow more spaced connections for the application of excitation voltages between the common counter electrode 9 and the arrayed electrodes which extend along the interface between the sheet 6 and the sheet 3.
  • the system of axes 0, x i , x 2 , x 3 is located in the space which overhangs the radiating face of the transducer here constituted by the counter-electrode 9. This space is generally occupied by a propagation medium 12 having the acoustic impedance of the water.
  • FIG. 2 is a partial sectional view of the electromechanical transducer of Figure 1. It can be seen that the sheet 3 which is made of a passive polymer material, is fixed to the base 1 by a peripheral adhesive seal 10 and carries the conductive strips 4, 5, 8 and 7 which act as rear electrodes for the piezoelectric polymer sheet 6. A glue joint 11 secures these two sheets 3 and 6 in the part which overhangs the recess 2. Thus a vibrating structure mixed active and passive of total thickness h l + h 2 is interposed between the propagation medium 12 and the medium which fills the recess 2. The half-wave or full-wave operation of the arrangement of FIG.
  • the parameter h 2 / h 1 is plotted on the abscissa and the central operating frequency f R on the ordinate.
  • the measurement of the transducer conversion losses was also plotted on the ordinate on a decibel scale.
  • Curves 13, 14 and 15 relate to the half-wave operating mode, while curves 16, 17 and 18 in phantom relate to the full-wave operating mode.
  • Curve 13 shows that the central operating frequency of the transducer decreases with increasing the thickness of the sheet 3, which serves as a support for the electrodes. This effect is quite predictable, since the half-wave operation of the vibrating structure links the operating frequency to the choice of the thicknesses h l and h 2 taking into account the propagation speeds in the media 3 and 6 which make up this structure.
  • the vibrations originating in the active sheet 6 undergo little reflection when they enter the sheet 3 because the impedances of the two juxtaposed media are advantageously chosen close to one another. On the other hand, the vibrations undergo an almost perfect reflection at the level of the lower face of the sheet 3 from where they are returned towards the medium 12 in order to obtain maximum radiation.
  • the curve 15 which represents the conversion losses shows that the addition of the sheet 3 makes it possible to keep low losses not exceeding 15 dB for a thickness h 2 reaching 200 smokes
  • the curve 14 can be read on the frequency scale and gives the AF bandwidth of the transducer in absolute value. We see that this bandwidth varies little since it remains between 1, 2 and 0.8 MHz. The presence of the sheet 3 therefore makes it possible to obtain a good conversion yield and a good resolution while bringing a clear advantage as regards the production of metal deposits having good adhesion.
  • the curves in phantom which relate to the operation in whole wave indicate characteristics in general less favorable.
  • the curve 17 gives the operating frequency which is higher, since an entire wave must be established between the end faces of the vibrating structure.
  • Curve 18 gives the value of the conversion losses which are generally higher than in half-wave operation. However, when the thickness of the sheet 3 is of the same order as that of the sheet 6, it can be seen that the conversion loss is practically as low as with the sheet 6 alone in half-wave operation. The curve 16 which gives the bandwidth shows that it can be as good, or even better than with the half-wave operating mode.
  • the sheet 3 although it is passive, perfectly solves the problem of the adhesion of the electrodes 4, 5, 7, 8 while retaining the good operating qualities of the transducer both in sensitivity only in resolution.
  • FIG. 4 an alternative embodiment can be seen in which the electrode 9 is surmounted by a quarter wave layer 19 made of polystyrene which performs the impedance matching between the propagation medium 12 and the piezoelectric polymer material 6.
  • This impedance matching increases the relative bandwidth at 5 MHz which goes from 26% to 32% and the layer 19 can serve as a support for the deposition of the electrode 9 before being bonded to the polymer sheet 6 piezoelectric.
  • a metal deposit adheres much better on supports made of organic material having a carbon oxygen double bond and much less well on piezoelectric polymer materials such as polyvinylidene fluoride PVF 2 or PVF - TRFE copolymers.
  • the recess 2 in the base 1 can be completely or partially filled with a porous material of low density having an acoustic impedance low enough to ensure high reflectivity at the level of the lower face of the sheet 3.
  • the proposed technique consists in adding a layer of non-piezoelectric polymer whose acoustic impedance is close to that of the piezoelectric polymer and whose thickness varies between 3.04 and 0.5 wavelength.
  • the layers can be bonded using epoxy resin, preferably placing the electrodes against the faces of the piezoelectric polymer sheet.
  • FIG. 5 we can see a single probe transducer which differs from the transducer in FIG. 4 by the shape of a spherical cap given to its radiating face. This shape can be obtained by pressing all of the sheets 3, 6, 19 in a preform. The solidification of the adhesive can take place during the preforming operation, in order to ensure the conservation of the deformations imposed by the preform. It is also possible to bond together preformed parts separately by thermoforming.
  • the monoprobe device of FIG. 5 has the symmetry of revolution around the axis 22 and F is the center of curvature of the radiating face, the emitted E wave can be focused at point F.
  • FIG. 6 an alternative embodiment of the device in FIG. 4 can be seen, which consists in providing on each side of the active sheet 6 sheets 3 and 20 made of passive materials having an acoustic impedance close to the acoustic impedance of the active material of the sheet 6.
  • the vibrating structure obtained by bonding the sheets 20, 6 and 3 can function in half-wave or in whole wave between a quarter-wave adapter layer 19 and a medium with low impedance such as air filling the recess 2 of the base 1.
  • the acoustic impedance of the quarter adapter layer wave is chosen close to the geometric mean of the acoustic impedances of the propagation medium and of the active sheet 6.
  • transducer implements a radiating face of cylindrical shape having as its axis the line 21.
  • the radiation is focused in a plane perpendicular to the line 21.
  • the transducer comprises a network of sources.
  • Each source is a part of vibrating structure delimited by an active portion of the sheet 6 comprised between the counter-electrode 9 and an electrode 4, 5, 7 or 8.
  • the electrodes 4, 5, 7, 8 suitably delayed, the acoustic radiation can be made to converge at a point F on line 21.
  • the network arrangements of FIGS. 1 and 7 can be produced on a sheet of polyethylene terephthalate measuring 12.5 cm in length and 3.5 cm in width.
  • the central network of parallel conductive strips can occupy a rectangular range of 4 cm in length and 1.4 cm in width.
  • the network of conductive strips may have a width of 125 l um and a pitch of 250 smoke Such networking arrangement may operate at 3 MHz.
  • the electrodes are photo-etched or deposited through a mask on the sheet 3 of polyethylene terephthalate, after which a sheet 6 of polyvinylidene fluoride measuring 4 cm in length and 1.4 cm in width is brought back into the central part.
  • the assembly After bonding of the sheet 6 provided with its metallization 9 on the sheet 3 and after bonding of an adapter blade 19 of polystyrene on the electrode 9, the assembly is mounted on a base 1 in the form of a frame so that all of the active surface overhangs a central recess of the base 1.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transducers For Ultrasonic Waves (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Ultra Sonic Daignosis Equipment (AREA)
EP83401485A 1982-07-30 1983-07-19 Halbwellenwandler unter Anwendung eines aktiven piezoelektrischen Polymerelements Withdrawn EP0100711A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8213357 1982-07-30
FR8213357A FR2531298B1 (fr) 1982-07-30 1982-07-30 Transducteur du type demi-onde a element actif en polymere piezoelectrique

Publications (2)

Publication Number Publication Date
EP0100711A2 true EP0100711A2 (de) 1984-02-15
EP0100711A3 EP0100711A3 (de) 1984-11-14

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EP83401485A Withdrawn EP0100711A3 (de) 1982-07-30 1983-07-19 Halbwellenwandler unter Anwendung eines aktiven piezoelektrischen Polymerelements

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US (1) US4473769A (de)
EP (1) EP0100711A3 (de)
FR (1) FR2531298B1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0176030A3 (en) * 1984-09-26 1987-08-05 Terumo Kabushiki Kaisha Trading As Terumo Corporation Ultrasonic transducer and method of manufacturing same
EP0186096A3 (en) * 1984-12-18 1987-10-21 Kabushiki Kaisha Toshiba Polymeric piezoelectric ultrasonic probe

Families Citing this family (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5999900A (ja) * 1982-11-29 1984-06-08 Toshiba Corp 超音波探触子
JPS6086999A (ja) * 1983-10-19 1985-05-16 Hitachi Ltd 超音波探触子の製造方法
JPS60140153A (ja) * 1983-12-28 1985-07-25 Toshiba Corp 超音波探触子の製造方法
EP0166180B1 (de) * 1984-05-30 1989-02-01 Siemens Aktiengesellschaft Hydrophon
US4964302A (en) * 1984-09-25 1990-10-23 Grahn Allen R Tactile sensor
US4604543A (en) * 1984-11-29 1986-08-05 Hitachi, Ltd. Multi-element ultrasonic transducer
US4833659A (en) * 1984-12-27 1989-05-23 Westinghouse Electric Corp. Sonar apparatus
DE3611669A1 (de) * 1985-04-10 1986-10-16 Hitachi Medical Corp., Tokio/Tokyo Ultraschallwandler
JPS62150610A (ja) * 1985-12-25 1987-07-04 株式会社日立製作所 入力装置
US4908543A (en) * 1988-06-30 1990-03-13 Litton Systems, Inc. Acoustic transducer
US5160870A (en) * 1990-06-25 1992-11-03 Carson Paul L Ultrasonic image sensing array and method
NZ243294A (en) * 1991-06-25 1995-04-27 Commw Scient Ind Res Org Time of flight of acoustic wave packets through fluid: reduction of higher order acoustic mode effects
US6432050B1 (en) * 1997-12-30 2002-08-13 Remon Medical Technologies Ltd. Implantable acoustic bio-sensing system and method
WO2004025832A1 (en) * 2002-09-12 2004-03-25 Philips Intellectual Property & Standards Gmbh Bulk acoustic wave resonator with means for suppression of pass-band ripple in bulk acoustic wave filters
BE1015150A3 (nl) * 2002-10-21 2004-10-05 Sonitron Nv Verbeterde transducent
US8033173B2 (en) * 2005-12-12 2011-10-11 Kimberly-Clark Worldwide, Inc. Amplifying ultrasonic waveguides
US20070130771A1 (en) * 2005-12-12 2007-06-14 Kimberly-Clark Worldwide, Inc. Methods for producing ultrasonic waveguides having improved amplification
DE102005061343B4 (de) 2005-12-21 2010-11-25 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Ultraschallwandler mit selbsttragender Anpassschicht sowie Verfahren zur Herstellung
DE202012004305U1 (de) * 2012-04-27 2012-05-25 Texmag Gmbh Vertriebsgesellschaft Vorrichtung zum Detektieren einer Kante einer Materialbahn

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US3912830A (en) * 1971-10-13 1975-10-14 Kureha Chemical Ind Co Ltd Method of producing a piezoelectric or pyroelectric element
US4117074A (en) * 1976-08-30 1978-09-26 Tiersten Harry F Monolithic mosaic piezoelectric transducer utilizing trapped energy modes
JPS599000B2 (ja) * 1979-02-13 1984-02-28 東レ株式会社 超音波トランスデユ−サ
EP0015886A1 (de) * 1979-03-13 1980-09-17 Toray Industries, Inc. Verbessertes elektro-akustisches Wandler-Element
US4383194A (en) * 1979-05-01 1983-05-10 Toray Industries, Inc. Electro-acoustic transducer element
FR2503517A1 (fr) * 1981-04-06 1982-10-08 Thomson Csf Transducteur piezo-electrique

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0176030A3 (en) * 1984-09-26 1987-08-05 Terumo Kabushiki Kaisha Trading As Terumo Corporation Ultrasonic transducer and method of manufacturing same
EP0186096A3 (en) * 1984-12-18 1987-10-21 Kabushiki Kaisha Toshiba Polymeric piezoelectric ultrasonic probe

Also Published As

Publication number Publication date
EP0100711A3 (de) 1984-11-14
FR2531298B1 (fr) 1986-06-27
FR2531298A1 (fr) 1984-02-03
US4473769A (en) 1984-09-25

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