JPH0766467A - Macromolecular piezoelectric film and manufacture thereof - Google Patents
Macromolecular piezoelectric film and manufacture thereofInfo
- Publication number
- JPH0766467A JPH0766467A JP23588193A JP23588193A JPH0766467A JP H0766467 A JPH0766467 A JP H0766467A JP 23588193 A JP23588193 A JP 23588193A JP 23588193 A JP23588193 A JP 23588193A JP H0766467 A JPH0766467 A JP H0766467A
- Authority
- JP
- Japan
- Prior art keywords
- film
- polarization
- piezoelectric film
- frequency
- 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.)
- Granted
Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 14
- 230000010287 polarization Effects 0.000 claims abstract description 49
- 230000005684 electric field Effects 0.000 claims abstract description 9
- 229920000642 polymer Polymers 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 8
- 229920006254 polymer film Polymers 0.000 claims description 3
- 239000010408 film Substances 0.000 description 67
- 239000000463 material Substances 0.000 description 8
- 239000012528 membrane Substances 0.000 description 8
- BQCIDUSAKPWEOX-UHFFFAOYSA-N 1,1-Difluoroethene Chemical compound FC(F)=C BQCIDUSAKPWEOX-UHFFFAOYSA-N 0.000 description 5
- 238000009826 distribution Methods 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 239000002033 PVDF binder Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 230000002269 spontaneous effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- MIZLGWKEZAPEFJ-UHFFFAOYSA-N 1,1,2-trifluoroethene Chemical compound FC=C(F)F MIZLGWKEZAPEFJ-UHFFFAOYSA-N 0.000 description 1
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000007334 copolymerization reaction Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000013081 microcrystal Substances 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Landscapes
- Transducers For Ultrasonic Waves (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、高分子圧電膜、その製
造方法およびそれを用いた超音波トランスジューサに関
する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric polymer film, a method for producing the same, and an ultrasonic transducer using the same.
【０００２】[0002]
【従来の技術】従来から、ポリフッ化ビニリデン（ＰＶ
ＤＦ）を延伸して得られるβ型と呼ばれる圧電性微結晶
からなる膜をポーリングして圧電膜が得られることはよ
く知られている。また、フッ化ビニリデンと三フッ化エ
チレンとの共重合体［Ｐ（ＶＤＦ−ＴｒＦＥ）］、およ
びフッ化ビニリデンと四フッ化エチレンとの共重合体
［Ｐ（ＶＤＦ−ＴｅＦＥ）］は共重合比が適切な範囲の
場合にはβ型結晶が得られ、未延伸膜でもポーリングに
よって大きな圧電性を発現できることが知られている。
この圧電効果は結晶中の分子鎖の双極子がポーリング電
場で協同的に分子鎖の回転を通して配向し、膜がその厚
さ方向に関して分極することによっている。Ｐ（ＶＤＦ
−ＴｒＦＥ）やＰ（ＶＤＦ−ＴｅＦＥ）あるいはＰＶＤ
Ｆにおいては、強誘電体に特有なＤ−Ｅ（電気変位−電
界強度）ヒステリシス曲線が見られるのはその証拠の一
つである。2. Description of the Related Art Conventionally, polyvinylidene fluoride (PV
It is well known that a film made of β-type piezoelectric microcrystals obtained by stretching DF) is poled to obtain a piezoelectric film. Further, a copolymer of vinylidene fluoride and ethylene trifluoride [P (VDF-TrFE)] and a copolymer of vinylidene fluoride and tetrafluoroethylene [P (VDF-TeFE)] are copolymerization ratios. It is known that a β-type crystal can be obtained in a suitable range, and a large piezoelectricity can be exhibited by poling even in an unstretched film.
This piezoelectric effect is due to the fact that the dipoles of the molecular chains in the crystal are oriented cooperatively through the rotation of the molecular chains in the Pauling electric field, and the film is polarized in the thickness direction. P (VDF
-TrFE), P (VDF-TeFE) or PVD
One of the proofs is that in F, a D-E (electrical displacement-electric field strength) hysteresis curve peculiar to a ferroelectric substance is seen.
【０００３】一方、ポーリングにより分極化された高分
子圧電材料は低い音響インピーダンスと優れた柔軟性、
良好な膜形成性をもつので、これを用いて、無機圧電材
料では実現の困難な特徴をもつ超音波トランスジューサ
が製造されている。たとえば、パルス応答特性のよい広
周波数帯域で作動するトランスジューサや、大口径を持
つ凹面トランスジューサ、高周波で作動するトランスジ
ューサ、あるいは連続した圧電膜からなるアニュラアレ
イまたはリニアアレイ型トランスジューサなどである。On the other hand, a polymer piezoelectric material polarized by poling has low acoustic impedance and excellent flexibility,
Since it has a good film forming property, it is used to manufacture an ultrasonic transducer having a characteristic that is difficult to realize with an inorganic piezoelectric material. For example, a transducer which operates in a wide frequency band having a good pulse response characteristic, a concave transducer having a large diameter, a transducer which operates at high frequency, or an annular array or linear array type transducer composed of continuous piezoelectric films.
【０００４】従来これらに用いられている高分子圧電材
料は、膜厚方向に沿っては均一に、つまり同一方向に分
極化されたものであった。従って、これらの厚み伸縮振
動子では、膜中の音波波長の１／２と膜の厚さｔとが等
しくなる周波数ｆで自由共振がおこる。すなわちｆ＝ｖ
／２ｔである（ｖは音速）。また、このような膜の場合
には、膜の背面を金属電極など音響インピーダンスの十
分大きい材料でバッキングすると、ｆ＝ｖ／４ｔで共振
するトランスジューサが得られる。Conventionally, the polymeric piezoelectric materials used in these materials are polarized uniformly in the film thickness direction, that is, in the same direction. Therefore, in these thickness stretching oscillators, free resonance occurs at the frequency f at which 1/2 of the acoustic wave wavelength in the film and the film thickness t are equal. That is, f = v
/ 2t (v is the speed of sound). Further, in the case of such a film, when the back surface of the film is backed with a material having a sufficiently large acoustic impedance such as a metal electrode, a transducer that resonates at f = v / 4t can be obtained.
【０００５】近年、超音波顕微鏡など高周波数（数１０
ＭＨｚあるいは数１００ＭＨｚ）の超音波を用いる機器
が発達し、その需要が増大している。そして、このよう
な高周波トランスジューサには高分子圧電材料がきわめ
て好ましく用いられる。In recent years, high frequencies (several 10
Equipment using ultrasonic waves of MHz or several 100 MHz) has been developed and its demand is increasing. A polymer piezoelectric material is very preferably used for such a high frequency transducer.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、上記の
ように膜厚方向に均一に分極化された従来の高分子圧電
膜にあっては、動作周波数と圧電材料の厚さとは反比例
するため、高周波数になる程薄膜が必要となり、製作上
困難な点が多くあった。However, in the conventional polymer piezoelectric film uniformly polarized in the film thickness direction as described above, since the operating frequency and the thickness of the piezoelectric material are inversely proportional, As the frequency increased, a thin film was needed, and there were many difficulties in manufacturing.
【０００７】本発明は、従来のものと同一厚みの膜を用
いた場合、分極方向が一方向のみの圧電膜よりも２倍ま
たは３倍の周波数で駆動できる高分子圧電膜およびその
製造方法を提供し、さらに、それを用いた超音波トラン
スジューサを提供することを目的とする。The present invention provides a polymer piezoelectric film which can be driven at a frequency twice or three times that of a piezoelectric film having a polarization direction of only one direction when a film having the same thickness as that of a conventional one is used, and a manufacturing method thereof. The present invention further provides an ultrasonic transducer using the same.
【０００８】[0008]
【課題を解決するための手段】この目的に沿う本発明の
高分子圧電膜は、分極が反転した２領域を膜厚方向にお
いて有することを特徴とするものから成る。この高分子
圧電膜においては、膜厚方向ほぼ中央部に領域の境界を
有することが好ましい。The polymer piezoelectric film of the present invention for this purpose is characterized by having two regions in which the polarization is inverted in the film thickness direction. In this polymer piezoelectric film, it is preferable to have a region boundary in the substantially central portion in the film thickness direction.
【０００９】また、本発明に係る高分子圧電膜の製造方
法は、ポーリングにより圧電性を付与する高分子圧電膜
の製造方法において、分極が反転した２領域が膜厚方向
において形成されるまで、ポーリング電場の方向を繰り
返し反転することを特徴とする方法から成る。The method for producing a polymeric piezoelectric film according to the present invention is the method for producing a polymeric piezoelectric film in which piezoelectricity is imparted by poling, until two regions in which polarization is inverted are formed in the film thickness direction. The method comprises repeatedly reversing the direction of the poling electric field.
【００１０】さらに、本発明に係る超音波トランスジュ
ーサは、上記の高分子圧電膜を用いたことを特徴とする
ものから成る。Further, an ultrasonic transducer according to the present invention is characterized by using the above polymer piezoelectric film.
【００１１】すなわち、本発明の骨子は、厚み方向にお
いて逆方向に分極化した領域を有する高分子圧電膜、該
圧電膜を分極反転を繰り返すことを特徴とする方法で製
造すること、およびこの膜を用いることにより、一方向
のみに分極した膜が発生する超音波の周波数の２倍ない
し３倍の、またはさらに高次の周波数で作動する超音波
トランスジューサ、を提供することにある。That is, the gist of the present invention is to provide a polymer piezoelectric film having regions polarized in opposite directions in the thickness direction, a method for producing the piezoelectric film by repeating polarization inversion, and this film. Is to provide an ultrasonic transducer which operates at a frequency that is two to three times the frequency of ultrasonic waves generated by a film polarized in only one direction, or a higher frequency.
【００１２】本発明者らは、高い効率をもつ、高周波数
で駆動するトランスジューサを比較的厚い膜で実現する
ことを目的に、膜の分極の状態を深く研究した結果、膜
厚方向の中央部を境界にして分極方向が逆転した２つの
分極領域をもつ圧電膜を用いることが極めて有効である
ことを見出し、その作製に成功した。そしてこの高分子
圧電膜は、分極反転が起こるのに必要なポーリング電場
を、方向を繰り返し反転させて印加することによって得
られる。The inventors of the present invention have deeply studied the polarization state of the film for the purpose of realizing a transducer having a high efficiency and driven at a high frequency with a relatively thick film. It was found that it is extremely effective to use a piezoelectric film having two polarization regions in which the polarization directions are reversed at the boundary of, and succeeded in its fabrication. This polymer piezoelectric film can be obtained by applying the poling electric field necessary for polarization reversal by repeatedly reversing the direction.
【００１３】このような分極分布状態の形成が完成する
のに必要な反転回数は温度によって異なるが、Ｐ（ＶＤ
Ｆ−ＴｒＦＥ）の場合、強誘電体に特有なＤ−Ｅヒステ
リシス曲線が見られなくなる回数、すなわち、分極反転
が見かけ上起こらなくなる回数で完成し、常温では数万
回〜数十万回、８０℃以上の高温では数回〜数十回であ
る。しかし、このような分極反転領域は、反転回数とと
もに連続的に成長するため、より少ない反転回数を選ん
でも本発明が目的とする圧電膜を得ることができる。よ
り少ない反転回数とは、具体的には、分極反転が見かけ
上起こらなくなる回数の２／３以上、より好ましくは３
／４以上が適している。The number of inversions required to complete the formation of such a polarization distribution state depends on the temperature, but P (VD
In the case of (F-TrFE), the D-E hysteresis curve peculiar to a ferroelectric substance is no longer seen, that is, the number of times when polarization inversion does not seem to occur apparently, and it is tens of thousands to hundreds of thousands of times at room temperature. It is several times to several tens times at a high temperature of ℃ or more. However, since such a domain-inverted region continuously grows with the number of times of inversion, the piezoelectric film intended by the present invention can be obtained even if the number of times of inversion is selected. The smaller number of times of inversion means, specifically, 2/3 or more of the number of times in which polarization inversion apparently does not occur, and more preferably 3
/ 4 or more is suitable.
【００１４】高分子圧電膜の厚み方向をｚとしたとき、
上記のような分極反転を繰り返し行うことによって得ら
れる分極Ｐ（ｚ）は、表面（ｚ＝０）からｔ0 まで自発
分極Ｐ0 をもち、ｔ0 ＜ｚ＜ｔでは−Ｐ0 の自発分極を
もつこと、また０．３＜ｔ0／ｔ＜０．７であることが
実験的に明らかになった。When the thickness direction of the polymer piezoelectric film is z,
The polarization P (z) obtained by repeatedly performing the above-mentioned polarization inversion has a spontaneous polarization P 0 from the surface (z = 0) to t 0 , and when t 0 <z <t, the spontaneous polarization of −P 0 . It has been experimentally revealed that, and that 0.3 <t 0 /t<0.7.
【００１５】このような不均一分極が形成される原因は
未だ明らかではないが、イオン電流が大きくなる温度
で、反転分極が見かけ上起こらなくなるのに必要なポー
リング反転回数が急激に小さくなることから、膜表面と
電極との界面付近でのイオンの蓄積（空間電荷）による
電場が強く影響しているものと考えられる。The cause of the formation of such non-uniform polarization is not yet clear, but the number of poling inversions required to apparently prevent inversion polarization from occurring at a temperature at which the ionic current becomes large rapidly decreases. It is considered that the electric field due to the accumulation of ions (space charge) near the interface between the film surface and the electrode has a strong influence.
【００１６】従来、直流電場でポーリングした圧電膜の
分極は厚み方向に必ずしも均一ではなく、分極方向は一
定であるが、その強度分布に不均一が存在することが報
告されている。特にＰ（ＶＤＦ−ＴｒＦＥ）では数１０
℃の温度でポーリングすると、分極が零の領域と、一方
向に一定の大きさに分極した領域とをもつ、不均一分極
膜が生成する（Ｍ．Ｓｕｚｕｋｉ，Ｔ．Ｎａｋａｎｉｓ
ｉ，Ｈ．Ｏｈｉｇａｓｈｉ；Ｒｅｐｔ．Ｐｒｏｇｒ．Ｐ
ｏｌｙｍ．Ｐｈｙｓ．Ｊｐｎ．２５（１９８２）５０
５）。後者の場合、膜の厚み共振はｆ＝ｖ／２ｔの他に
ｆ＝ｖ／ｔとその整数倍の周波数で起こる。しかし、こ
の膜をトランジューサに利用した場合、超音波トランス
ジューサとしての効率は低い。Conventionally, it has been reported that the polarization of a piezoelectric film poled by a DC electric field is not always uniform in the thickness direction and the polarization direction is constant, but the intensity distribution is non-uniform. Especially in P (VDF-TrFE)
When it is poled at a temperature of ° C, a non-uniformly polarized film having a region of zero polarization and a region polarized in one direction to a certain size is formed (M. Suzuki, T. Nakanis).
i, H. Ohashi; Rept. Progr. P
olym. Phys. Jpn. 25 (1982) 50
5). In the latter case, the thickness resonance of the film occurs not only at f = v / 2t but also at f = v / t and its integral multiple frequencies. However, when this membrane is used for a transducer, the efficiency as an ultrasonic transducer is low.
【００１７】また、従来から、Ｐ（ＶＤＦ−ＴｒＦＥ）
あるいはＰ（ＶＤＦ−ＴｅＦＥ）をポーリングするの
に、繰り返し反転分極方法が常用されている。しかし、
この場合の繰り返し分極反転回数は常温で高々数回ない
し数１０回であり、膜厚方向に沿って逆転した分極領域
が形成されるには余りにも少なく、現実には均一な分
極、つまり一方向のみの分極状態となっている。本発明
の方法は、より多くの反転を繰り返すことによって、顕
著な逆転分極域が形成されるもので、従来の方法とは全
く異なるものである。Further, conventionally, P (VDF-TrFE)
Alternatively, the reversal polarization method is commonly used to poll P (VDF-TeFE). But,
In this case, the number of repetitive polarization inversions is at most several to several tens at normal temperature, which is too small to form a reversed polarization region along the film thickness direction, and in reality, uniform polarization, that is, one direction. It is only in the polarized state. The method of the present invention is a completely different method from the conventional method in that a remarkable inversion polarization region is formed by repeating more inversions.
【００１８】本発明で得られた膜を自由振動子として動
作させると、膜厚方向ほぼ中央部で分極の方向が逆転し
ている場合には、同じ厚さの均一分極分布膜（一方向の
みに分極された膜）の２倍の周波数で作動する。また、
膜の音響インピーダンスよりも十分大きい材料でバッキ
ングした場合には、均一分極膜の３倍の周波数を基本と
する共振挙動を示す。さらに、分極方向の逆転位置を膜
厚方向中央部以外に設定することによって、トランスジ
ューサの動作周波数を調節することができる。従って、
均一分極膜に比較して高い周波数で作動し、特に高周波
数の超音波トランスジューサへの適用に適している。When the film obtained according to the present invention is operated as a free oscillator, if the polarization direction is reversed at the substantially central portion in the film thickness direction, a uniform polarization distribution film of the same thickness (only in one direction) Of the membrane (polarized to.) Operates at twice the frequency. Also,
When backing with a material sufficiently larger than the acoustic impedance of the film, it exhibits a resonance behavior based on a frequency three times that of a uniformly polarized film. Further, the operating frequency of the transducer can be adjusted by setting the reverse position of the polarization direction to a position other than the central portion in the film thickness direction. Therefore,
It operates at a higher frequency than a uniformly polarized film and is particularly suitable for application to high frequency ultrasonic transducers.
【００１９】本発明が適用できるのは分極反転が外部電
場で可能な強誘電性高分子であるが、Ｐ（ＶＤＦ−Ｔｒ
ＦＥ）、Ｐ（ＶＤＦ−ＴｅＦＥ）および高圧結晶化した
ＰＶＤＦにはとくに好ましく適用できる。The present invention can be applied to a ferroelectric polymer in which polarization reversal is possible by an external electric field, but P (VDF-Tr
FE), P (VDF-TeFE) and high-pressure crystallized PVDF are particularly preferably applicable.
【００２０】[0020]
【実施例】実施例１ Ｐ（ＶＤＦ−ＴｒＦＥ）（組成モル比：ＶＤＦ／ＴｒＦ
Ｅ＝７５／２５）膜をＤＭＦ（ジメチルホルムアミド）
溶液から流延して厚さ１０μｍの膜を作製し、さらにこ
れを１４０℃で結晶化を行なった。これに金属蒸着して
電極を両面に設けた。この膜に±９００Ｖのピーク値を
もつ１Ｈｚの交流電圧（三角波）を印加して６０℃で分
極反転を繰り返した。繰り返し分極反転の初期の抗電場
は３５ＭＶ／ｍであった。分極反転電荷量（２Ｐｒ：残
留分極Ｐｒの２倍の電荷量）は分極反転回数（Ｎ）とと
もに次第に減少し、約３万回で急激に減少して、分極反
転は起こらなくなった。EXAMPLES Example 1 P (VDF-TrFE) (composition molar ratio: VDF / TrF
E = 75/25) DMF (dimethylformamide)
A film having a thickness of 10 μm was formed by casting from the solution, and the film was further crystallized at 140 ° C. Metal was vapor-deposited on this to provide electrodes on both sides. An alternating voltage (triangular wave) of 1 Hz having a peak value of ± 900 V was applied to this film, and polarization reversal was repeated at 60 ° C. The initial coercive field of repeated polarization reversal was 35 MV / m. The polarization inversion charge amount (2Pr: charge amount twice as much as the residual polarization Pr) gradually decreased with the number of polarization inversions (N), and rapidly decreased at about 30,000 times, and the polarization inversion did not occur.
【００２１】この高分子圧電膜における、Ｎ＝４×１０
4 回の膜の自由振動子の共振挙動を図１に示す。図１
は、本発明の方法で作製した厚み１０μｍのＰ（ＶＤＦ
−ＴｒＦＥ）膜の共振アドミッタンスの絶対値｜Ｙ｜お
よび位相Φと周波数の関係を示している。図１に示すよ
うに、均一に（一方向のみに）分極された場合に期待さ
れる共振周波数１２０ＭＨｚ、３６０ＭＨｚには弱い共
振しか示さず、本来共振がみられないはずの２４０ＭＨ
ｚに強い共振を示した。このような共振は、膜の表面か
らほぼ４．３μｍの深さで分極方向が逆転した分極分布
をもつ場合に出現することが解析の結果わかった。In this polymer piezoelectric film, N = 4 × 10
Figure 1 shows the resonance behavior of the free oscillator of the film four times. Figure 1
Is a P (VDF having a thickness of 10 μm manufactured by the method of the present invention.
-TrFE) shows the relationship between the absolute value | Y | of the resonance admittance of the film, the phase Φ, and the frequency. As shown in FIG. 1, only weak resonance is shown at the resonance frequencies of 120 MHz and 360 MHz expected when uniformly polarized (only in one direction), and 240 MHz, which should not have any resonance, should be observed.
It showed a strong resonance in z. As a result of analysis, it was found that such a resonance appears when the polarization distribution has a polarization direction reversed at a depth of approximately 4.3 μm from the surface of the film.
【００２２】なお、８０℃で分極反転を行った場合には
Ｎ＝２０で分極反転が見かけ上起こらなくなった。その
Ｎ＝１００の膜の分極分布はｔ0 ／ｔ＝０．４であっ
た。When polarization reversal was performed at 80 ° C., polarization reversal apparently did not occur at N = 20. The polarization distribution of the N = 100 film was t 0 /t=0.4.
【００２３】均一な分極方向の圧電膜では２４０ＭＨｚ
の共振周波数をもつには５μｍの膜を製作する必要があ
った。しかし、５μｍの膜は現実には製作が容易でな
く、超音波素子など音響変換子への加工は難しい。本発
明によって得られた１０μｍの膜では取扱いが容易にな
るばかりでなく、トランスジューサの面積によっては電
源との電気インピーダンス整合などが容易となる。240 MHz for a piezoelectric film having a uniform polarization direction
It was necessary to fabricate a film of 5 μm in order to have a resonance frequency of However, a film of 5 μm is not easy to manufacture in reality, and it is difficult to process it into an acoustic transducer such as an ultrasonic element. The 10 μm film obtained by the present invention not only facilitates handling, but also facilitates electrical impedance matching with a power source depending on the area of the transducer.
【００２４】実施例２ 厚さ１１４μｍのＰ（ＶＤＦ−ＴｒＦＥ）（７５／２
５）を７０℃で分極反転を繰り返して圧電膜を得た。そ
の自由振動子の共振アドミッタンスの周波数特性の解析
によれば、電気機械結合係数ｋｔ＝０．２８、、ｔ0 ／
ｔ＝０．４５であった。この膜を凹面に加工したシリン
ダー状の銅電極（面積４．０ｃｍ2 ）に分極の逆転層
（ｚ＝５１、μｍ）が銅電極に近くなるように接着して
超音波トランスジューサを作製した。銅電極と膜表面の
電極との間に高周波電場を加えて水中に超音波を放射
し、トランスジューサの挿入損失ＣＬおよびＴＬ（その
定義についてはＨ．Ｏｈｉｇａｓｈｉ．ｅｔ ａｌ．；
Ｊ．Ａｐｐｌ．Ｐｈｙｓ．Ｊｐｎ．２７（１９８８）３
５４を参照、ＣＬ：非同調変換損失＝変換損失、ＴＬ：
電気音響変換損失＝トランスジューサ損失）を測定し
た。Example 2 P (VDF-TrFE) (75/2 with a thickness of 114 μm)
The polarization inversion of 5) was repeated at 70 ° C. to obtain a piezoelectric film. According to the analysis of the frequency characteristic of the resonance admittance of the free oscillator, the electromechanical coupling coefficient kt = 0.28, t 0 /
It was t = 0.45. This film was bonded to a cylindrical copper electrode (area: 4.0 cm 2 ) processed into a concave surface so that the polarization reversal layer (z = 51, μm) was close to the copper electrode to produce an ultrasonic transducer. A high-frequency electric field is applied between the copper electrode and the electrode on the membrane surface to radiate ultrasonic waves into the water, and the insertion losses CL and TL of the transducer (for the definition, see H. Ohishi. Et al .;
J. Appl. Phys. Jpn. 27 (1988) 3
54, CL: Asynchronous conversion loss = Conversion loss, TL:
The electroacoustic conversion loss = transducer loss) was measured.
【００２５】図２にこの銅ブロックでバッキングした超
音波トランスジューサの水中での動作周波数特性（ＴＬ
およびＣＬ）の実測値（○）と計算値（実線）を示す。
損失の周波数特性の実測値とＭａｓｏｎの等価回路に基
づく計算値はよく一致し、１６ＭＨｚで効率よく動作す
ることがわかった。均一に分極した同じ厚さの膜を用い
た場合５．２ＭＨｚに動作周波数をもつが、本発明の膜
ではその３倍の周波数で作動することがわかる。また、
図２から明らかなように、本発明による膜を用いたトラ
ンスジューサの場合、５ＭＨｚから１６ＭＨｚまで高い
効率で作動する特徴を有しており、この点でも本発明の
膜を用いたトランスジューサは優れた特徴を示してい
る。FIG. 2 shows the operating frequency characteristics (TL) of the ultrasonic transducer backed by the copper block in water.
And CL) shows the measured value (◯) and the calculated value (solid line).
It was found that the actually measured value of the frequency characteristic of loss and the calculated value based on the Mason's equivalent circuit were in good agreement, and operated efficiently at 16 MHz. It can be seen that when a uniformly polarized membrane of the same thickness is used, it has an operating frequency of 5.2 MHz, whereas the membrane of the invention operates at three times that frequency. Also,
As is apparent from FIG. 2, the transducer using the membrane according to the present invention has a characteristic that it operates with high efficiency from 5 MHz to 16 MHz, and in this respect also, the transducer using the membrane of the present invention has an excellent characteristic. Is shown.
【００２６】以上ではｔ0 ／ｔがほぼ０．５の例を示し
たが、ｔ0 ／ｔ＝０．３３に近い場合にはｆ＝３ｖ／４
ｔ（Ｈｚ）の周波数での効率がより高くなることが理論
からも示される。In the above, an example in which t 0 / t is approximately 0.5 has been shown, but when it is close to t 0 /t=0.33, f = 3v / 4
The theory also shows that the efficiency at the frequency of t (Hz) is higher.
【００２７】なお、本実施例では本発明による膜の基本
的な特徴を明らかにするために、単純な構造のトランス
ジューサについて示したが、より複雑な積層構造と多素
子構造（アレイ型構造など）をもつトランスジューサに
本発明の膜が応用可能であることは云うまでもない。In this embodiment, a transducer having a simple structure is shown in order to clarify the basic characteristics of the film according to the present invention. However, a more complicated laminated structure and multi-element structure (array type structure) It goes without saying that the membrane of the present invention can be applied to a transducer having
【００２８】[0028]
【発明の効果】以上説明したように、本発明によれば、
膜厚方向のほぼ中央部で分極の方向が逆転した高分子圧
電膜構造としたので、従来の同一厚みの、一方向のみに
分極された高分子圧電膜に比べ、２倍ないし３倍の周波
数で駆動することが可能となった。したがって、膜厚を
極端に薄くすることなく、従来の製膜法で十分に製造可
能な膜厚にて、高周波数で作動可能な超音波トランスジ
ューサを実現することができる。As described above, according to the present invention,
Since the polymer piezoelectric film structure in which the polarization direction is reversed at approximately the center of the film thickness direction is used, the frequency is 2 to 3 times that of the conventional polymer piezoelectric film having the same thickness and polarized in only one direction. It became possible to drive with. Therefore, it is possible to realize an ultrasonic transducer capable of operating at a high frequency with a film thickness that can be sufficiently manufactured by a conventional film forming method without making the film thickness extremely thin.
【図１】本発明に係る高分子圧電膜の共振アドミッタン
ス、位相、周波数の関係図である。FIG. 1 is a relationship diagram of resonance admittance, phase, and frequency of a piezoelectric polymer film according to the present invention.
【図２】本発明に係る超音波トランスジューサの水中で
の動作周波数特性図である。FIG. 2 is an operating frequency characteristic diagram of the ultrasonic transducer according to the present invention in water.
Claims (4)
て有することを特徴とする高分子圧電膜。1. A polymer piezoelectric film having two regions in which the polarization is inverted in the film thickness direction.
ることを特徴とする請求項１の高分子圧電膜。2. The polymer piezoelectric film according to claim 1, wherein the polymer piezoelectric film has a boundary between regions substantially in the center in the film thickness direction.
子圧電膜の製造方法において、分極が反転した２領域が
膜厚方向において形成されるまで、ポーリング電場の方
向を繰り返し反転することを特徴とする、高分子圧電膜
の製造方法。3. A method for producing a polymeric piezoelectric film which imparts piezoelectricity by poling, wherein the direction of the poling electric field is repeatedly reversed until two regions whose polarizations are reversed are formed in the film thickness direction. , A method for manufacturing a piezoelectric polymer film.
たことを特徴とする超音波トランスジューサ。4. An ultrasonic transducer comprising the polymer piezoelectric film according to claim 1 or 2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23588193A JP3486929B2 (en) | 1993-08-30 | 1993-08-30 | Polymer piezoelectric film and method of manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP23588193A JP3486929B2 (en) | 1993-08-30 | 1993-08-30 | Polymer piezoelectric film and method of manufacturing the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0766467A true JPH0766467A (en) | 1995-03-10 |
| JP3486929B2 JP3486929B2 (en) | 2004-01-13 |
Family
ID=16992630
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP23588193A Expired - Lifetime JP3486929B2 (en) | 1993-08-30 | 1993-08-30 | Polymer piezoelectric film and method of manufacturing the same |
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| Country | Link |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007208799A (en) * | 2006-02-03 | 2007-08-16 | Toray Eng Co Ltd | Needle type hydrophone |
| JP2018119087A (en) * | 2017-01-26 | 2018-08-02 | 株式会社イデアルスター | Piezoelectric film and method for manufacturing the same |
-
1993
- 1993-08-30 JP JP23588193A patent/JP3486929B2/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007208799A (en) * | 2006-02-03 | 2007-08-16 | Toray Eng Co Ltd | Needle type hydrophone |
| JP2018119087A (en) * | 2017-01-26 | 2018-08-02 | 株式会社イデアルスター | Piezoelectric film and method for manufacturing the same |
| WO2018139190A1 (en) * | 2017-01-26 | 2018-08-02 | 株式会社イデアルスター | Piezoelectric film and method for producing same |
| KR20190105100A (en) * | 2017-01-26 | 2019-09-11 | 가부시키가이샤 이디알 스타 | Piezoelectric Film, and Manufacturing Method Thereof |
| US11469366B2 (en) | 2017-01-26 | 2022-10-11 | Ideal Star Inc. | Piezoelectric film and method for producing same |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3486929B2 (en) | 2004-01-13 |
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