JP2008010529A

JP2008010529A - Laminated piezoelectric element

Info

Publication number: JP2008010529A
Application number: JP2006177679A
Authority: JP
Inventors: Tomonobu Eguchi; 知宣江口
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2006-06-28
Filing date: 2006-06-28
Publication date: 2008-01-17
Anticipated expiration: 2026-06-28
Also published as: JP5153093B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated piezoelectric element in which polarization can be reduced in an insulating region between an end of an inner electrode which is not connected to an outer electrode and a side of a piezoelectric main body, and deterioration of a polarization rate and displacement in an active part are suppressed; and which has high displacement and is superior in durability. <P>SOLUTION: In a laminated body 10 where piezoelectric layers 1 and first and second inner electrodes 7a and 7b are laminated, insulators 14 whose dielectric constant is lower than the piezoelectric layer 1 are installed in the insulating regions 13 between an end of the first inner electrode 7a and a side 3b, and between an end of the second inner electrode 7b and a first side 3a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、加圧により電圧を生じさせたり、電圧を加えて変位または力を生じさせたりする圧電センサや圧電アクチュエータ、圧電トランス、圧電バイモルフ等の積層型圧電素子に関するものであり、特に、駆動耐久性に優れた積層型圧電素子の構造に関するものである。 The present invention relates to a laminated piezoelectric element such as a piezoelectric sensor, a piezoelectric actuator, a piezoelectric transformer, or a piezoelectric bimorph that generates a voltage by pressurization or generates a displacement or a force by applying a voltage. The present invention relates to a structure of a laminated piezoelectric element having excellent durability.

従来より、積層型圧電素子としては、圧電体層と内部電極を交互に積層した積層型圧電素子の代表例として積層型圧電アクチュエータが知られている。積層型圧電アクチュエータは同時焼成タイプと、圧電磁器と内部電極とを交互に積層したスタックタイプとの２種類に分類されており、低電圧化、製造コスト低減の面から考慮すると、同時焼成タイプの積層型圧電アクチュエータが薄層化に対して有利であるといわれている。 Conventionally, as a multilayer piezoelectric element, a multilayer piezoelectric actuator is known as a representative example of a multilayer piezoelectric element in which piezoelectric layers and internal electrodes are alternately stacked. Multilayer piezoelectric actuators are classified into two types: the simultaneous firing type and the stack type in which piezoelectric ceramics and internal electrodes are alternately stacked. Considering low voltage and manufacturing cost reduction, the simultaneous firing type It is said that the laminated piezoelectric actuator is advantageous for thinning.

図１１は、従来の積層型圧電アクチュエータを示す断面図である。この積層型圧電アクチュエータでは、複数の圧電体層２０１が積層された圧電体２０３の内部に内部電極２０５が圧電体層２０１を介して重なり合うように積層されて圧電駆動に寄与する活性部２０６を有する積層体２０７が形成されている。内部電極２０５は、その一方の端部が積層体２０７の側面に左右交互に露出しており、この内部電極２０５の端部が露出した積層体２０７の側面に外部電極２０９が形成されており、圧電体２０３の表面に露出しない方の内部電極２０５の端部と外部電極２０９との間には絶縁領域２１０が形成されている。 FIG. 11 is a cross-sectional view showing a conventional multilayer piezoelectric actuator. This multilayer piezoelectric actuator has an active portion 206 that contributes to piezoelectric driving by laminating an internal electrode 205 so as to overlap through a piezoelectric layer 201 inside a piezoelectric body 203 in which a plurality of piezoelectric layers 201 are laminated. A stacked body 207 is formed. One end portion of the internal electrode 205 is alternately exposed on the side surface of the multilayer body 207, and an external electrode 209 is formed on the side surface of the multilayer body 207 where the end portion of the internal electrode 205 is exposed, An insulating region 210 is formed between the end of the internal electrode 205 that is not exposed on the surface of the piezoelectric body 203 and the external electrode 209.

また、近年に至り、下記の特許文献１に開示されたような構造の積層型圧電素子が提案されている（図１２）。この特許文献１に開示された積層型圧電素子では、複数の圧電体層３０１が積層され、対向する第１側面３０３ａおよび第２側面３０３ｂを有する圧電体３０５内に、圧電体層３０１を介して重なり合うように厚み方向に交互に配置された第１内部電極３０７ａ、第２内部電極３０７ｂが備えられており、第１内部電極３０７ａが圧電体３０５の第１側面３０３ａに、一方、第２内部電極３０７ｂが圧電体３０５の第２側面３０３ｂに引き出されている。また、これら第１側面３０３ａ、第２側面３０３ｂにはそれぞれ第１外部電極３０９ａ、第２外部電極３０９ｂがさらに備えられている。 In recent years, a multilayer piezoelectric element having a structure as disclosed in Patent Document 1 below has been proposed (FIG. 12). In the multilayer piezoelectric element disclosed in Patent Document 1, a plurality of piezoelectric layers 301 are stacked, and the piezoelectric layer 305 having the first side surface 303 a and the second side surface 303 b facing each other is interposed via the piezoelectric layer 301. A first internal electrode 307a and a second internal electrode 307b are arranged alternately in the thickness direction so as to overlap each other, and the first internal electrode 307a is provided on the first side surface 303a of the piezoelectric body 305, while the second internal electrode. 307 b is drawn out to the second side surface 303 b of the piezoelectric body 305. The first side surface 303a and the second side surface 303b are further provided with a first external electrode 309a and a second external electrode 309b, respectively.

この場合、圧電体３０５において、第１内部電極３０７ａと第２内部電極３０７ｂとが重なり合っている部分が活性部３１１であり、また、活性部３１１と第１側面３０３ａ、第２側面３０３ｂとの間が、それぞれ第１不活性部３１３ａ、第２不活性部３１３ｂとされている。 In this case, in the piezoelectric body 305, the portion where the first internal electrode 307a and the second internal electrode 307b overlap is the active portion 311, and between the active portion 311 and the first side surface 303a and the second side surface 303b. Are a first inactive part 313a and a second inactive part 313b, respectively.

また、第１不活性部３１３ａおよび第２不活性部３１３ｂのうち、第１外部電極３０９ａに接続されていない第２内部電極３０７ｂの端部３０７ｂｂと第１側面３０３ａとの間、および、第２外部電極３０９ｂに接続されていない第１内部電極３０７ａの端部３０７ａａと第２側面３０３ｂとの間における第１内部電極３０７ａおよび第２内部電極３０７ｂの同一平面上の延長した領域に絶縁領域３１４ａ、３１４ｂを設けてそれぞれ第１ダミー電極３１５ａ、第２ダミー電極３１５ｂがそれぞれ形成されている。 In addition, between the first inactive portion 313a and the second inactive portion 313b, between the end portion 307bb of the second internal electrode 307b not connected to the first external electrode 309a and the first side surface 303a, and the second Insulating region 314a in an extended region on the same plane of first internal electrode 307a and second internal electrode 307b between end 307aa of first internal electrode 307a and second side surface 303b not connected to external electrode 309b, 314b is provided, and a first dummy electrode 315a and a second dummy electrode 315b are formed respectively.

このような積層型圧電素子では第１外部電極３０９ａおよび第２外部電極３０９ｂが、それぞれ第１内部電極３０７ａおよび第２内部電極３０７ｂのみならず第１ダミー電極３１５ａ、第２ダミー電極３１５ｂとも接続されているために、積層型圧電素子の第１側面３０３ａ、第２側面３０３ｂのそれぞれにおいて、第１外部電極３０９ａ、第２外部電極３０９ｂと第１内部電極３０７ａ、第２内部電極３０７ｂとの接続部における接点不良の発生を低減できるとされている。
特開２００５−２８５８１７号公報 In such a multilayer piezoelectric element, the first external electrode 309a and the second external electrode 309b are connected not only to the first internal electrode 307a and the second internal electrode 307b but also to the first dummy electrode 315a and the second dummy electrode 315b, respectively. Therefore, in each of the first side surface 303a and the second side surface 303b of the multilayer piezoelectric element, the connection portion between the first external electrode 309a, the second external electrode 309b, the first internal electrode 307a, and the second internal electrode 307b. It is said that the occurrence of contact failure in can be reduced.
JP 2005-285817 A

しかしながら、上記の図９に示された従来の積層型圧電アクチュエータでは、積層型圧電素子に電圧を印加して分極を発生させたり、また、実際に交流電場を印加して駆動させたときに、圧電体層２０１間に積層された内部電極２０５によって形成される活性部２０６の変位とともに、内部電極２０５の端部と外部電極２０９との間の絶縁領域２１０もまた分極されている状態にある。つまり、この絶縁領域２１０の分極方向は、内部電極２０５の端部と外部電極２０９との間の同一平面の延長線の方向であり、積層方向に分極して駆動する活性部２０６とは角度にして約９０°方向が違うために、絶縁領域２１０における異方的な分極によって活性部２０６における分極率や変位が低下するという問題があった。 However, in the conventional multilayer piezoelectric actuator shown in FIG. 9 described above, when voltage is applied to the multilayer piezoelectric element to generate polarization, or when an AC electric field is actually applied and driven, Along with the displacement of the active portion 206 formed by the internal electrodes 205 stacked between the piezoelectric layers 201, the insulating region 210 between the end portions of the internal electrodes 205 and the external electrodes 209 is also polarized. That is, the polarization direction of the insulating region 210 is the direction of the extension line on the same plane between the end of the internal electrode 205 and the external electrode 209, and is at an angle with respect to the active portion 206 that is driven by polarization in the stacking direction. Therefore, there is a problem that the polarizability and displacement in the active portion 206 are reduced due to anisotropic polarization in the insulating region 210.

また、図１０に示した従来の積層型圧電素子においては、圧電体層３０１間に積層された第１内部電極３０７ａ、第２内部電極３０７ｂによって形成される活性部３１１の変位とともに、第１内部電極３０７ａの端部３０７ａａと第２ダミー電極３１５ｂとの間、第２内部電極３０７ｂの端部３０７ｂｂと第１ダミー電極３１５ａとの間のそれぞれの絶縁領域３１４ａ、３１４ｂもまた分極が起こっていた。 In the conventional multilayer piezoelectric element shown in FIG. 10, the first internal electrode 307a and the second internal electrode 307b formed between the piezoelectric layers 301 are displaced along with the displacement of the active portion 311. Insulation regions 314a and 314b between the end portion 307aa of the electrode 307a and the second dummy electrode 315b and between the end portion 307bb of the second internal electrode 307b and the first dummy electrode 315a were also polarized.

この図１０に示した絶縁領域３１４ａ、３１４ｂの分極方向は、第１内部電極３０７ａの端部３０７ａａと第２側面３０３ａ、第２内部電極３０７ｂの端部３０７ｂｂと第１側面３０３ｂとの間の同一平面の延長線の方向であり、この場合も積層方向に分極して駆動する活性部３１１とは角度にして約９０°方向が違うために、絶縁領域３１４ａ、３１４ｂにおける異方的な分極によって活性部３１１における分極率や変位が低下するという問題があった。 The polarization directions of the insulating regions 314a and 314b shown in FIG. 10 are the same between the end portion 307aa and the second side surface 303a of the first internal electrode 307a, and the end portion 307bb and the first side surface 303b of the second internal electrode 307b. In this case, since the direction of the active portion 311 that is polarized and driven in the stacking direction is about 90 ° different from that of the active portion 311 that is driven in the laminating direction, it is activated by anisotropic polarization in the insulating regions 314a and 314b. There was a problem that the polarizability and displacement in the portion 311 were lowered.

従って、本発明は、外部電極に接続されない内部電極の端部と圧電体本体の側面との間の絶縁領域における分極を低減でき、これにより活性部における分極率や変位の低下を抑え高変位かつ耐久性に優れた積層型圧電素子を提供することを目的とする。 Therefore, the present invention can reduce the polarization in the insulating region between the end of the internal electrode that is not connected to the external electrode and the side surface of the piezoelectric body, thereby suppressing the decrease in the polarizability and displacement in the active portion and high displacement. An object of the present invention is to provide a laminated piezoelectric element having excellent durability.

本発明の積層型圧電素子は、（１）複数の圧電体層が積層され、対向する第１側面および第２側面を有する圧電体の内部に、第１内部電極が前記第１側面に、第２内部電極が前記第２側面にそれぞれ引き出されて配置されており、前記第１側面および前記第２側面にはそれぞれ前記第１内部電極に接続された第１外部電極、および前記第２内部電極に接続された第２外部電極を備えた積層型圧電素子であって、前記第１内部電極の端部と前記第２側面との間の前記第１内部電極の延長上の領域、および前記第２内部電極の端部と前記第１側面との間の前記第２内部電極の延長上の領域に、前記圧電体層よりも比誘電率の低い絶縁部を設けたことを特徴とする。 In the multilayer piezoelectric element of the present invention, (1) a plurality of piezoelectric layers are laminated, a piezoelectric body having a first side surface and a second side surface facing each other, a first internal electrode on the first side surface, 2 internal electrodes are respectively drawn out and arranged on the second side surface, and the first side electrode and the second side surface are respectively connected to the first external electrode and the second internal electrode. A laminated piezoelectric element including a second external electrode connected to the first external electrode, and a region on an extension of the first internal electrode between an end of the first internal electrode and the second side surface; 2. An insulating portion having a relative dielectric constant lower than that of the piezoelectric layer is provided in a region on the extension of the second internal electrode between the end portion of the two internal electrodes and the first side surface.

また、本発明の積層型圧電素子は、（２）複数の圧電体層が積層され、対向する第１側面および第２側面を有する圧電体の内部に配置された第１内部電極および第２内部電極を備え、前記第１内部電極が前記圧電体の前記第１側面に、前記第２内部電極が前記圧電体の前記第２側面に引き出されて配置されており、前記第１側面および前記第２側面にはそれぞれ前記第１内部電極に接続された第１外部電極、および前記第２内部電極に接続された第２外部電極を備え、前記第１内部電極の端部と前記第２側面との間の前記第１内部電極の延長上の領域に、前記第２外部電極に接続された第２ダミー電極が前記第１内部電極の端部との間に絶縁部を介して形成され、前記第２内部電極の端部と前記第１側面との間の前記第２内部電極の延長上の領域に、前記第１外部電極に接続された第１ダミー電極が前記第２内部電極の端部との間に絶縁部を介して形成されている積層型圧電素子であって、前記絶縁部の比誘電率を前記圧電体層よりも低くしたことを特徴とする。 In the multilayer piezoelectric element of the present invention, (2) a plurality of piezoelectric layers are stacked, and a first internal electrode and a second internal disposed inside a piezoelectric body having first and second side surfaces facing each other. The first internal electrode is disposed on the first side surface of the piezoelectric body, and the second internal electrode is disposed on the second side surface of the piezoelectric body. The first side surface and the first side surface Two side surfaces each include a first external electrode connected to the first internal electrode and a second external electrode connected to the second internal electrode, and an end of the first internal electrode, the second side surface, A second dummy electrode connected to the second external electrode is formed between the end portion of the first internal electrode in an area on the extension of the first internal electrode between the first internal electrode and the second internal electrode, On the extension of the second internal electrode between the end of the second internal electrode and the first side surface A laminated piezoelectric element in which a first dummy electrode connected to the first external electrode is formed between the end portion of the second internal electrode and an insulating portion between the first external electrode and the insulating portion; The relative dielectric constant is lower than that of the piezoelectric layer.

上記積層型圧電素子では、（３）前記圧電体層がチタン酸ジルコン酸鉛によって形成されており、前記絶縁部がチタン酸鉛、チタン酸ビスマス酸ストロンチウムおよびチタン酸ビスマス酸バリウムから選ばれる１種によって形成されていること、（４）前記第１ダミー電極と前記第１内部電極との間の前記圧電体層中に前記第１外部電極に接続された第３ダミー電極が設けられ、前記第２ダミー電極と前記第２内部電極との間の前記圧電体層中に、前記第２外部電極に接続された第４ダミー電極が設けられたことが望ましい。 In the multilayer piezoelectric element, (3) the piezoelectric layer is formed of lead zirconate titanate, and the insulating portion is selected from lead titanate, strontium bismuthate titanate, and barium bismuthate titanate. (4) a third dummy electrode connected to the first external electrode is provided in the piezoelectric layer between the first dummy electrode and the first internal electrode, and the first dummy electrode is provided. Preferably, a fourth dummy electrode connected to the second external electrode is provided in the piezoelectric layer between the second dummy electrode and the second internal electrode.

本発明の積層型圧電素子によれば、上記の第１内部電極の端部と第２外部電極との間、および第２内部電極の端部と第１外部電極との間、あるいは、上記の第１内部電極の端部と第２ダミー電極との間、および第２内部電極の端部と第１ダミー電極との間の圧電体層上の絶縁部の比誘電率よりも低くしたことにより、上記した絶縁部における分極を小さくできる。このため絶縁部から活性部への異方的な分極の影響が小さくなり、活性部における分極および変位の低下が抑えられ、高変位かつ耐久性に優れた積層型圧電素子を得ることができる。 According to the multilayer piezoelectric element of the present invention, between the end portion of the first internal electrode and the second external electrode, between the end portion of the second internal electrode and the first external electrode, or the above-described By making it lower than the relative dielectric constant of the insulating portion on the piezoelectric layer between the end portion of the first internal electrode and the second dummy electrode and between the end portion of the second internal electrode and the first dummy electrode The polarization in the insulating part can be reduced. For this reason, the influence of anisotropic polarization from the insulating portion to the active portion is reduced, the decrease in polarization and displacement in the active portion is suppressed, and a multilayer piezoelectric element having high displacement and excellent durability can be obtained.

図１は本発明の積層型圧電素子を示す斜視図である。図２は、図１のＡ−Ａ‘における縦断面図である。図３は図２の拡大図であり、第１内部電極、第２内部電極とから形成される活性部、不活性部（比誘電率の低い絶縁領域）を説明するための模式図である。 FIG. 1 is a perspective view showing a multilayer piezoelectric element of the present invention. FIG. 2 is a longitudinal sectional view taken along line A-A ′ in FIG. 1. FIG. 3 is an enlarged view of FIG. 2, and is a schematic diagram for explaining an active portion and an inactive portion (insulating region having a low relative dielectric constant) formed by the first internal electrode and the second internal electrode.

本発明の積層型圧電素子は、複数の圧電体層１が積層され、対向する第１側面３ａ、第２側面３ｂを有する圧電体５の内部に、圧電体層１を介して重なり合うように厚み方向に交互に配置された第１内部電極７ａ、第２内部電極７ｂが備えられて積層体１０が形成されている。この場合、第１内部電極７ａは圧電体５の第１側面３ａに、一方、第２内部電極７ｂは圧電体５の第２側面３ｂに引き出されている。また、第１側面３ａ、第２側面３ｂには、それぞれ第１外部電極８ａ、第２外部電極８ｂが備えられている。さらに、この第１外部電極８ａおよび第２の外部電極８ｂにはリード線８ａａ、８ｂｂがそれぞれ接続固定されている。 The multilayer piezoelectric element of the present invention has a thickness such that a plurality of piezoelectric layers 1 are stacked and overlap each other through the piezoelectric layer 1 inside a piezoelectric body 5 having a first side surface 3a and a second side surface 3b facing each other. A laminated body 10 is formed by providing first internal electrodes 7 a and second internal electrodes 7 b that are alternately arranged in the direction. In this case, the first internal electrode 7 a is drawn to the first side surface 3 a of the piezoelectric body 5, while the second internal electrode 7 b is drawn to the second side surface 3 b of the piezoelectric body 5. The first side surface 3a and the second side surface 3b are provided with a first external electrode 8a and a second external electrode 8b, respectively. Further, lead wires 8aa and 8bb are connected and fixed to the first external electrode 8a and the second external electrode 8b, respectively.

この積層型圧電素子では、第１内部電極７ａ、第２内部電極７ｂが圧電体層１を介して重なり合っている部分が活性部９であり、活性部９と、第１側面３ａ、第２側面３ｂとの間が、それぞれ第１不活性部１１ａ、第２不活性部１１ｂとされている。 In this multilayer piezoelectric element, a portion where the first internal electrode 7a and the second internal electrode 7b overlap with each other through the piezoelectric layer 1 is the active portion 9, and the active portion 9, the first side surface 3a, and the second side surface. The space between 3b is a first inactive portion 11a and a second inactive portion 11b.

また、第１不活性部１１ａ、第２不活性部１１ｂのうち、第１外部電極８ａに接続されているが第２外部電極８ｂに接続されていない第１内部電極７ａの端部７ａａと第２側面３ｂとの間の圧電体層１上の第１内部電極７ａの延長上の領域、および第２外部電極８ｂに接続されているが第１外部電極８ａに接続されていない第２内部電極７ｂの端部７ｂｂと第１側面３ａとの間の圧電体層１上の第２内部電極７ｂの延長上の領域（第１不活性部１１ａ、第２不活性部１１ｂ内）にそれぞれ絶縁部１４が形成されている。 Of the first inactive part 11a and the second inactive part 11b, the end part 7aa of the first internal electrode 7a connected to the first external electrode 8a but not connected to the second external electrode 8b A region on the extension of the first internal electrode 7a on the piezoelectric layer 1 between the two side surfaces 3b, and a second internal electrode connected to the second external electrode 8b but not connected to the first external electrode 8a Insulating portions in the regions (in the first inactive portion 11a and the second inactive portion 11b) on the extension of the second internal electrode 7b on the piezoelectric layer 1 between the end portion 7bb of the 7b and the first side surface 3a 14 is formed.

なお、圧電体層１は、例えば、チタン酸ジルコン酸鉛Ｐｂ（Ｚｒ，Ｔｉ）Ｏ_３（以下ＰＺＴと略す）を主成分とする圧電セラミックス材料等で形成されている。上記成分の圧電セラミックスは、その圧電特性を示す圧電歪み定数ｄ_３３が高いという利点がある。また、圧電セラミックスとしては、コスト面から、Ｐｄ比率の低いＡｇ／Ｐｄ合金を用いることが望ましいが、このためには９８０℃〜１１００℃程度で焼成可能な圧電セラミックスを用いることが望ましい。 The piezoelectric layer 1 is made of, for example, a piezoelectric ceramic material mainly composed of lead zirconate titanate Pb (Zr, Ti) O ₃ (hereinafter abbreviated as PZT). The piezoelectric ceramic of the components has the advantage of a high piezoelectric strain constant d ₃₃ indicating the piezoelectric characteristic. As the piezoelectric ceramic, it is desirable to use an Ag / Pd alloy having a low Pd ratio from the viewpoint of cost. For this purpose, it is desirable to use a piezoelectric ceramic that can be fired at about 980 ° C. to 1100 ° C.

そして本発明の積層型圧電素子においては、絶縁部１４の比誘電率を圧電体層１の主成分であるチタン酸ジルコン酸鉛よりも低くしたことが重要である。この場合、絶縁部１４の厚みが第１内部電極７ａ、第２内部電極７ｂと同一厚みであると異種材料による活性部９への影響を低減できるという利点がある。 In the multilayer piezoelectric element of the present invention, it is important that the dielectric constant of the insulating portion 14 is lower than that of lead zirconate titanate, which is the main component of the piezoelectric layer 1. In this case, if the thickness of the insulating portion 14 is the same as that of the first internal electrode 7a and the second internal electrode 7b, there is an advantage that the influence on the active portion 9 due to the different material can be reduced.

そして、本発明の積層型圧電素子では圧電体層１がチタン酸ジルコン酸鉛によって形成され、また絶縁部１４となる材料としてチタン酸鉛(ＰｂＴｉＯ_３)、チタン酸ビスマス酸ストロンチウム（ＳｒＴｉ_４Ｂｉ_４Ｏ_１５）およびチタン酸ビスマス酸バリウム（ＢａＴｉ_４Ｂｉ_４Ｏ_１５）から選ばれる１種であることが望ましい。これらの材料の比誘電率は、室温において、チタン酸鉛が２２０、チタン酸ビスマス酸ストロンチウムおよびチタン酸ビスマス酸バリウムがいずれも１５０であり、本発明の積層型圧電素子を構成する圧電体層１の主成分であるチタン酸ジルコン酸鉛の２３００に対して、いずれも比誘電率が１／１０以下であり、これにより第１内部電極７ａの端部と第２外部電極８ｂとの間、第２内部電極７ｂの端部と第１外部電極８ａとの間の圧電体層１上の絶縁領域１３における分極を低減でき、活性部９における分極率や変位への影響を低減できる。この場合、同時焼成しても活性部９を構成するチタン酸ジルコン酸鉛へ拡散しても影響の少ないという点および耐電圧がチタン酸ジルコン酸鉛よりも高いという点でチタン酸鉛が特に好ましい。 In the multilayer piezoelectric element of the present invention, the piezoelectric layer 1 is formed of lead zirconate titanate, and lead titanate (PbTiO ₃ ) and strontium titanate (SrTi ₄ Bi ₄ ) are used as the insulating portion 14. O ₁₅ ) and barium bismuth titanate (BaTi ₄ Bi ₄ O ₁₅ ) are desirable. The relative dielectric constants of these materials are 220 for lead titanate, 150 for strontium bismuth titanate and 150 for bismuth titanate at room temperature, and the piezoelectric layer 1 constituting the multilayer piezoelectric element of the present invention. The relative dielectric constant of each of lead zirconate titanate 2300, which is the main component, is 1/10 or less, so that the end portion of the first internal electrode 7a and the second external electrode 8b 2 The polarization in the insulating region 13 on the piezoelectric layer 1 between the end portion of the internal electrode 7b and the first external electrode 8a can be reduced, and the influence on the polarizability and displacement in the active portion 9 can be reduced. In this case, lead titanate is particularly preferable in that it is less affected even if co-fired and diffused into lead zirconate titanate constituting the active part 9 and that the withstand voltage is higher than lead zirconate titanate. .

一方、絶縁領域１３を低誘電率化せずに圧電体層１の主成分であるチタン酸ジルコン酸鉛で構成したものは絶縁領域１３に大きな分極が発生するため、その影響により活性部９１の分極率や変位が低下する恐れがある。 On the other hand, when the insulating region 13 is made of lead zirconate titanate which is the main component of the piezoelectric layer 1 without reducing the dielectric constant, a large polarization is generated in the insulating region 13. There is a risk that the polarizability and displacement will decrease.

次に、本発明の他の形態について説明する。 Next, another embodiment of the present invention will be described.

図４は、ダミー電極を有する本発明の積層型圧電素子を示す斜視図である。図５は、図４のＡ−Ａ‘における縦断面図である。図６は、図５の拡大図であり、第１内部電極、第２内部電極、第１ダミー電極および第２ダミー電極とから形成される活性部、不活性部および比誘電率の低い絶縁領域を説明するための模式図である。 FIG. 4 is a perspective view showing the multilayer piezoelectric element of the present invention having a dummy electrode. FIG. 5 is a longitudinal sectional view taken along line A-A ′ in FIG. 4. FIG. 6 is an enlarged view of FIG. 5, and shows an active portion, an inactive portion, and an insulating region having a low relative dielectric constant formed by the first internal electrode, the second internal electrode, the first dummy electrode, and the second dummy electrode. It is a schematic diagram for demonstrating.

本発明の積層型圧電素子は、複数の圧電体層５１が積層され、対向する第１側面５３ａ、第２側面５３ｂを有する圧電体５５の内部に、圧電体層５１を介して重なり合うように厚み方向に交互に配置された第１内部電極５７ａ、第２内部電極５７ｂが備えられて積層体６０が形成されている。この場合、第１内部電極５７ａは圧電体５５の第１側面５３ａに、一方、第２内部電極５７ｂは圧電体５５の第２側面５３ｂに引き出されている。また、第１側面５３ａ、第２側面５３ｂには、それぞれ第１外部電極５８ａ、第２外部電極５８ｂが備えられている。さらに、この第１外部電極５８ａおよび第２外部電極５８ｂにはリード線５８ａａ、５８ｂｂがそれぞれ接続固定されている。 The multilayer piezoelectric element of the present invention has a thickness such that a plurality of piezoelectric layers 51 are stacked and overlap each other through the piezoelectric layer 51 inside a piezoelectric body 55 having a first side surface 53a and a second side surface 53b facing each other. A laminated body 60 is formed by providing first internal electrodes 57a and second internal electrodes 57b alternately arranged in the direction. In this case, the first internal electrode 57 a is drawn to the first side surface 53 a of the piezoelectric body 55, while the second internal electrode 57 b is drawn to the second side surface 53 b of the piezoelectric body 55. The first side surface 53a and the second side surface 53b are provided with a first external electrode 58a and a second external electrode 58b, respectively. Further, lead wires 58aa and 58bb are connected and fixed to the first external electrode 58a and the second external electrode 58b, respectively.

この積層型圧電素子では、第１内部電極５７ａ、第２内部電極５７ｂが重なり合っている部分が活性部５９であり、活性部５９と、第１側面５３ａ、第２側面５３ｂとの間が、それぞれ第１不活性部６１ａ、第２不活性部６１ｂとされている。 In this multilayer piezoelectric element, the portion where the first internal electrode 57a and the second internal electrode 57b overlap is the active portion 59, and the space between the active portion 59 and the first side surface 53a and the second side surface 53b is respectively The first inactive portion 61a and the second inactive portion 61b are provided.

また、第１不活性部６１ａ、第２不活性部６１ｂのうち、第１外部電極５８ａに接続されているが第２外部電極５８ｂに接続されていない第１内部電極５７ａの端部５７ａａと第２側面５３ｂとの間の圧電体層５１上の第１内部電極５７ａの延長上の領域、および第２外部電極５８ｂに接続されているが第１外部電極５８ａに接続されていない第２内部電極５７ｂの端部５７ｂｂと第１側面５３ａとの間の第２内部電極５７ｂの延長上の領域にそれぞれ絶縁部６４を設けて第１ダミー電極６５ａ、第２ダミー電極６５ｂが形成されている。 Of the first inactive part 61a and the second inactive part 61b, the end 57aa of the first internal electrode 57a connected to the first external electrode 58a but not connected to the second external electrode 58b and the first The region on the extension of the first internal electrode 57a on the piezoelectric layer 51 between the two side surfaces 53b and the second internal electrode connected to the second external electrode 58b but not connected to the first external electrode 58a An insulating portion 64 is provided in a region on the extension of the second internal electrode 57b between the end portion 57bb of the 57b and the first side surface 53a to form a first dummy electrode 65a and a second dummy electrode 65b.

本発明の積層型圧電素子では、上述のように、圧電体５５の第１側面５３ａおよび第２側面５３ｂに、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａおよび第２ダミー電極６５ｂが圧電体層５１を介して交互に現れる構造体とすることで、第１外部電極５８ａと第１内部電極５７ａとの間、および、第２外部電極５８ｂと第２内部電極５７ｂとの間で相互拡散による接続ポイントが増し、接続ポイントの間隔を短くできるため、圧電体５５と第１内部電極５７ａ、第２内部電極５７ｂとの間の接続強度を高めることができる。この場合、第１内部電極５７ａ、第２内部電極５７ｂの全層において第１ダミー電極６５ａ、第２ダミー電極６５ｂが形成されていることが活性部５９における圧電変位のばらつきを小さくできるという点で望ましい。 In the multilayer piezoelectric element of the present invention, as described above, the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, and the second dummy are formed on the first side surface 53a and the second side surface 53b of the piezoelectric body 55. By adopting a structure in which the electrodes 65b alternately appear via the piezoelectric layers 51, the first external electrode 58a and the first internal electrode 57a, and the second external electrode 58b and the second internal electrode 57b Since the connection points due to mutual diffusion increase and the interval between the connection points can be shortened, the connection strength between the piezoelectric body 55 and the first internal electrode 57a and the second internal electrode 57b can be increased. In this case, the fact that the first dummy electrode 65a and the second dummy electrode 65b are formed in all layers of the first internal electrode 57a and the second internal electrode 57b can reduce variations in piezoelectric displacement in the active portion 59. desirable.

ここで、上記第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂおよび絶縁部６４のそれぞれの幅は、圧電体５５における第１側面５３ａ、第２側面５３ｂ間の幅をｗとし、同方向の第１内部電極５７ａ、第２内部電極５７ｂの幅をｗ１、第１側面５３ａ、第２側面５３ｂからの第１ダミー電極６５ａ、第２ダミー電極６５ｂの幅をｗ２、第１内部電極５７ａの端部５７ａａと第２ダミー電極６５ｂとの間、第２内部電極５７ｂの端部５７ｂｂと第１ダミー電極６５ａとの間の絶縁部６４の幅をｗ３、第１内部電極５７ａ、第２内部電極５７ｂの重なる活性部５９の幅をｗ４とすると、ｗ１、ｗ４が大きいと圧電性に寄与する有効面積が大きくなり圧電特性を高められるという利点がある。 Here, the widths of the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, the second dummy electrode 65b, and the insulating portion 64 are determined by the first side surface 53a and the second side surface 53b in the piezoelectric body 55, respectively. The width of the first internal electrode 57a and the second internal electrode 57b in the same direction is w1, the width of the first dummy electrode 65a and the second dummy electrode 65b from the first side surface 53a and the second side surface 53b. W2, the width of the insulating portion 64 between the end portion 57aa of the first internal electrode 57a and the second dummy electrode 65b, and the width of the insulating portion 64 between the end portion 57bb of the second internal electrode 57b and the first dummy electrode 65a, w3, Assuming that the width of the active portion 59 where the first internal electrode 57a and the second internal electrode 57b overlap is w4, if w1 and w4 are large, there is an advantage that the effective area contributing to piezoelectricity increases and the piezoelectric characteristics can be improved.

また、第１ダミー電極６５ａおよび第２ダミー電極６５ｂのそれぞれの幅ｗ２が大きいと圧電体５５へのアンカー効果により第１外部電極５８ａおよび第２外部電極５８ｂの圧電体５５への接着力を高められるという利点がある。 Further, when the width w2 of each of the first dummy electrode 65a and the second dummy electrode 65b is large, the adhesion force of the first external electrode 58a and the second external electrode 58b to the piezoelectric body 55 is enhanced by the anchor effect on the piezoelectric body 55. There is an advantage that

また、第１内部電極５７ａの端部と第２ダミー電極６５ｂとの間、第２内部電極５７ｂの端部と第１ダミー電極６５ａとの間のそれぞれの絶縁部６４の幅ｗ３が大きい場合には、異なる電位である第１内部電極５７ａと第２ダミー電極６５ｂとの間、第２内部電極５７ｂと第１ダミー電極６５ａとの間の絶縁性を確保でき、電圧印加時のスパークを抑制できるという利点がある。このため本発明の積層型圧電素子を構成する絶縁部６４は緻密化したものが望ましく、密度が９５％以上であればさらに好ましい。 Further, when the width w3 of each insulating portion 64 between the end portion of the first internal electrode 57a and the second dummy electrode 65b and between the end portion of the second internal electrode 57b and the first dummy electrode 65a is large. Can ensure insulation between the first internal electrode 57a and the second dummy electrode 65b, which are at different potentials, and between the second internal electrode 57b and the first dummy electrode 65a, and can suppress sparks during voltage application. There is an advantage. For this reason, it is desirable that the insulating portion 64 constituting the multilayer piezoelectric element of the present invention is densified, and it is more preferable if the density is 95% or more.

なお、この積層型圧電素子の場合、圧電体５５と、第１内部電極５７ａ、第２内部電極５７ｂとの間の上記の構成により接続ポイント間の第１外部電極５８ａ、第２外部電極５８ｂの繰り返し疲労による断線を抑制し、電力供給パスが確実強固なものとなり、高電界で連続駆動させた場合においても第１外部電極５８ａと第１内部電極５７ａ、第２外部電極５８ｂと第２内部電極５７ｂとの接続部が剥離したりするといった問題が生じるのを防ぐことができる。 In the case of this multilayer piezoelectric element, the first external electrode 58a and the second external electrode 58b between the connection points are formed by the above configuration between the piezoelectric body 55 and the first internal electrode 57a and the second internal electrode 57b. The disconnection due to repeated fatigue is suppressed, the power supply path is surely strong, and the first external electrode 58a, the first internal electrode 57a, the second external electrode 58b, and the second internal electrode even when continuously driven with a high electric field. It is possible to prevent the problem that the connecting portion with 57b is peeled off.

さらに本発明の積層型圧電素子においても、上記した第１ダミー電極６５ａ、第２ダミー電極６５ｂを有しない積層型圧電素子の場合と同様、絶縁部６４の比誘電率を圧電体層５１よりも低くしたことが重要であり、この場合も、絶縁部１４の厚みが第１内部電極５７ａ、第２内部電極５７ｂと同一厚みであると異種材料による活性部５９への影響を低減できるという利点がある。 Furthermore, also in the multilayer piezoelectric element of the present invention, the dielectric constant of the insulating portion 64 is made to be higher than that of the piezoelectric layer 51 as in the multilayer piezoelectric element not having the first dummy electrode 65 a and the second dummy electrode 65 b described above. In this case, if the thickness of the insulating portion 14 is the same as that of the first internal electrode 57a and the second internal electrode 57b, there is an advantage that the influence on the active portion 59 by a different material can be reduced. is there.

なお、この積層型圧電素子においても、上記したダミー電極６５ａ、６５ｂを有しない積層型圧電素子の場合と同様、圧電体層５１がチタン酸ジルコン酸鉛によって形成された場合、また絶縁部１４となる材料としてチタン酸鉛(ＰｂＴｉＯ_３)、チタン酸ビスマス酸ストロンチウム（ＳｒＴｉ_４Ｂｉ_４Ｏ_１５）およびチタン酸ビスマス酸バリウム（ＢａＴｉ_４Ｂｉ_４Ｏ_１５）から選ばれる１種が好適であり、図１の積層型圧電素子の場合と同様、上述した効果が得られる。一方、絶縁領域６３を低誘電率化せずに圧電体層１の主成分であるチタン酸ジルコン酸鉛で構成したものは絶縁部６４に大きな分極が発生するため、その影響により活性部９１の分極率や変位が低下する恐れがある。 In the multilayer piezoelectric element, as in the multilayer piezoelectric element not having the dummy electrodes 65a and 65b, when the piezoelectric layer 51 is formed of lead zirconate titanate, One material selected from lead titanate (PbTiO ₃ ), strontium titanate bistrontate (SrTi ₄ Bi ₄ O ₁₅ ), and barium titanate titanate (BaTi ₄ Bi ₄ O ₁₅ ) is preferable as the material to be formed. As in the case of the multilayer piezoelectric element, the above-described effects can be obtained. On the other hand, when the insulating region 63 is made of lead zirconate titanate that is the main component of the piezoelectric layer 1 without reducing the dielectric constant, a large polarization is generated in the insulating portion 64. There is a risk that the polarizability and displacement will decrease.

図７は、本発明のもう一つの積層型圧電素子を示す部分的断面模式図である。この積層型圧電素子では、第１ダミー電極１１５ａと第１内部電極１１７ａとの間の圧電体層１１１中に第１外部電極１１８ａに接続するように、また、第２ダミー電極１１５ｂと第２内部電極１１７ｂとの間の圧電体層１１１中に第２外部電極１１８ｂに接続するように第４ダミー電極１１５ｄが形成されている。 FIG. 7 is a partial cross-sectional schematic view showing another multilayer piezoelectric element of the present invention. In this multilayer piezoelectric element, the piezoelectric layer 111 between the first dummy electrode 115a and the first internal electrode 117a is connected to the first external electrode 118a, and the second dummy electrode 115b and the second internal electrode are connected. A fourth dummy electrode 115d is formed in the piezoelectric layer 111 between the electrode 117b so as to be connected to the second external electrode 118b.

本発明では、第３ダミー電極１１５ｃおよび第４ダミー電極１１５ｄを上記のような構成で設けることにより、第１外部電極１１８ａと第１内部電極１１７ａ、第２外部電極１１８ｂと第２内部電極１１７ｂとの間の接続部が増え、接続強度が増すため耐久性が高くなり、変位のサイクル数を増すことができる。このため変位のサイクル数が増加しても変位量の低下を小さくできるという利点がある。これは圧電体１１５の第１側面１１３ａ、第２側面１１３ｂにおける第１不活性部１１１ａおよび第２不活性部１１１ｂが厚み方向への変位を緩和する領域となるため、接続ポイント間の変位量を低下させることで、第１内部電極１１７ａと第１外部電極１１８ａ、および第２内部電極１１７ｂと第２外部電極１１８ｂにおけるそれぞれの接続点での疲労による断線を抑制できるためである。 In the present invention, by providing the third dummy electrode 115c and the fourth dummy electrode 115d with the above-described configuration, the first external electrode 118a and the first internal electrode 117a, the second external electrode 118b and the second internal electrode 117b, The number of connection portions between the two increases, and the connection strength increases, so that the durability becomes high and the cycle number of displacement can be increased. For this reason, even if the number of cycles of displacement increases, there is an advantage that a decrease in displacement can be reduced. This is a region in which the first inactive portion 111a and the second inactive portion 111b on the first side surface 113a and the second side surface 113b of the piezoelectric body 115 relax the displacement in the thickness direction. This is because it is possible to suppress disconnection due to fatigue at the connection points of the first internal electrode 117a and the first external electrode 118a, and the second internal electrode 117b and the second external electrode 118b.

また、第１外部電極１１８ａ、第２外部電極１１８ｂの幅を０．５〜２ｍｍの範囲にまで狭くすることができ、積層型圧電素子の小型化にも適する。 In addition, the width of the first external electrode 118a and the second external electrode 118b can be reduced to a range of 0.5 to 2 mm, which is suitable for miniaturization of the multilayer piezoelectric element.

なお、この構造においても、第１内部電極１１７ａ、第２内部電極１１７ｂと同一厚みで、圧電体層１１１の主成分であるチタン酸ジルコン酸鉛よりも比誘電率の低い絶縁部１２４が設けられる。 Also in this structure, the insulating portion 124 having the same thickness as the first internal electrode 117a and the second internal electrode 117b and having a relative dielectric constant lower than that of lead zirconate titanate, which is the main component of the piezoelectric layer 111, is provided. .

次に、本発明の積層型圧電素子の構造に基いた駆動について図４〜図６に示した積層型圧電素子をもとに説明する。上記したように本発明の積層型圧電素子における圧電体層５１の間に形成された第１内部電極５７ａ、第２内部電極５７ｂは変位に寄与する駆動電極となるものであり、一方、ダミー電極６５ａ、６５ｂは、この駆動電極である第１内部電極５７ａ、第２内部電極５７ｂとは独立して逆の電位となるように第１外部電極５８ａ、第２外部電極５８ｂと接続されている。こうして第１外部電極５８ａ、第２外部電極５８ｂから印加された電圧は、第１内部電極５７ａ、第２内部電極５７ｂに供給され、活性部５９の圧電体層５１に逆圧電効果による変位を起こさせる。 Next, driving based on the structure of the multilayer piezoelectric element of the present invention will be described based on the multilayer piezoelectric element shown in FIGS. As described above, the first internal electrode 57a and the second internal electrode 57b formed between the piezoelectric layers 51 in the multilayer piezoelectric element of the present invention serve as drive electrodes that contribute to displacement, while dummy electrodes 65a and 65b are connected to the first external electrode 58a and the second external electrode 58b so as to have opposite potentials independently of the first internal electrode 57a and the second internal electrode 57b which are the drive electrodes. Thus, the voltages applied from the first external electrode 58a and the second external electrode 58b are supplied to the first internal electrode 57a and the second internal electrode 57b, and the piezoelectric layer 51 of the active portion 59 is displaced by the reverse piezoelectric effect. Let

次に、上述した本発明の積層型圧電素子を構成する電極材料について、これも図４〜図６の積層型圧電素子を元に説明する。この積層型圧電素子では、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂ、および第１外部電極５８ａ、第２外部電極５８ｂがＡｇ−Ｐｄの合金からなることが好ましい。 Next, the electrode material constituting the multilayer piezoelectric element of the present invention described above will also be described based on the multilayer piezoelectric element of FIGS. In this multilayer piezoelectric element, the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, the second dummy electrode 65b, the first external electrode 58a, and the second external electrode 58b are made of an Ag—Pd alloy. It is preferable to become.

このように第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂ、および第１外部電極５８ａ、第２外部電極５８ｂをともにＡｇおよびＰｄの合金とすることで、第１外部電極５８ａと第１内部電極５７ａとの間、第１外部電極５８ａと第１ダミー電極６５ａの間の接続部、第２外部電極５８ｂと第２内部電極５７ｂとの間、第２外部電極５８ｂと第２ダミー電極６５ｂとの間の接続部で、それぞれおこるＡｇおよびＰｄの相互拡散による接合を強固なものにできる。 In this way, the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, the second dummy electrode 65b, and the first external electrode 58a and the second external electrode 58b are all made of an alloy of Ag and Pd. , Between the first external electrode 58a and the first internal electrode 57a, between the first external electrode 58a and the first dummy electrode 65a, between the second external electrode 58b and the second internal electrode 57b, the second At the connecting portion between the external electrode 58b and the second dummy electrode 65b, the bonding caused by the mutual diffusion of Ag and Pd can be strengthened.

これは、例えば、第１外部電極５８ａ、第２外部電極５８ｂ、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａおよび第２ダミー電極６５ｂをそれぞれ構成する導電材中のＡｇの濃度と第１外部電極６５ａ、第２外部電極６５ｂ中のＡｇの濃度とが拡散により接合部およびその近傍においてほぼ等しくなるように作用するためであり、高電界、高圧力下で長時間連続駆動させる場合においても、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂと、第１外部電極５８ａ、第２外部電極５８ｂとを断線することなく優れた耐久性を有することができる。 For example, the first external electrode 58a, the second external electrode 58b, the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, and the second dummy electrode 65b are made of Ag in the conductive material. This is because the concentration and the concentration of Ag in the first external electrode 65a and the second external electrode 65b act so as to be substantially equal at the junction and its vicinity by diffusion, and are continuously driven for a long time under a high electric field and high pressure. Even in this case, the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, the second dummy electrode 65b, the first external electrode 58a, and the second external electrode 58b have excellent durability without being disconnected. Can have sex.

特に、本発明では、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂについてＰｄ量をＡ、Ａｇ量をＢとしたときに、質量比で、０＜Ａ／（Ａ＋Ｂ）≦０．４の関係であり、第１外部電極５８ａ、第２外部電極５８ｂについて、質量比で、０＜Ａ／（Ａ＋Ｂ）≦０．０５の関係を満足することが望ましい。 In particular, in the present invention, when the Pd amount is A and the Ag amount is B for the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, and the second dummy electrode 65b, the mass ratio is 0 < The relationship is A / (A + B) ≦ 0.4, and it is desirable that the first external electrode 58a and the second external electrode 58b satisfy the relationship 0 <A / (A + B) ≦ 0.05 in terms of mass ratio. .

本発明では、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂを０＜Ａ／（Ａ＋Ｂ）≦０．４とすることで、第１内部電極５７ａ、第２内部電極５７ｂ、ダミー電極６５ａ、６５ｂを圧電体層１の焼結温度に近づけることができるとともに、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂに含まれるＡｇの圧電体層５１への固溶を抑制し、これによる圧電特性の低下を抑えることができるという利点がある。また第１外部電極５８ａ、第２外部電極５８ｂにもＰｄを含ませることにより第１外部電極５８ａ、第２外部電極５８ｂのマイグレーションを抑制できるという利点がある。なお、リード線は導電性が高いという理由から銅線が用いられる。 In the present invention, by setting the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, and the second dummy electrode 65b to 0 <A / (A + B) ≦ 0.4, the first internal electrode 57a, The second internal electrode 57b and the dummy electrodes 65a and 65b can be brought close to the sintering temperature of the piezoelectric layer 1, and the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, and the second dummy electrode 65b. There is an advantage that the solid solution of Ag contained in the piezoelectric layer 51 can be suppressed and the deterioration of the piezoelectric characteristics due to this can be suppressed. Moreover, there is an advantage that migration of the first external electrode 58a and the second external electrode 58b can be suppressed by including Pd also in the first external electrode 58a and the second external electrode 58b. Note that a copper wire is used as the lead wire because of its high conductivity.

次に、本発明の積層型圧電素子の製法を説明する。図８は、ダミー電極を有する本発明の積層型圧電素子の製法を示す模式図である。この模式図ではダミー電極を内部電極と同一面に形成する場合である。 Next, a method for producing the multilayer piezoelectric element of the present invention will be described. FIG. 8 is a schematic view showing a method for producing the laminated piezoelectric element of the present invention having a dummy electrode. In this schematic diagram, the dummy electrode is formed on the same surface as the internal electrode.

本発明の積層型圧電素子は、先ず、ＰＺＴ等の圧電セラミックスの合成粉末と、アクリル系、ブチラール系等の有機高分子から成るバインダーと、ＤＢＰ（フタル酸ジオチル）、ＤＯＰ（フタル酸ジブチル）等の可塑剤とを混合してスラリーを作製し、このスラリーを周知のドクターブレード法等のテープ成形法により圧電体層１となるグリーンシート１５１を作製する。グリーンシート１５１の厚みは１０〜３００μｍであることが望ましい。グリーンシート１５１の厚みは１０μｍ以上であると絶縁性が高まり、かつ導体パターン１５７ａ、１５７ｂを形成したときに段差をグリーンシート１５１側に吸収できるという利点がある。一方、グリーンシート１５１の厚みが３００μｍ以下であると、積層数を増やしても薄型の圧電素子を形成でき、小型化に有利となる。また、圧電体層５１の薄層化は変位量を大きくできるという利点がある。 The laminated piezoelectric element of the present invention is first composed of a synthetic powder of piezoelectric ceramics such as PZT, a binder made of an organic polymer such as acrylic or butyral, DBP (diethyl phthalate), DOP (dibutyl phthalate), etc. A plastic sheet is mixed to produce a slurry, and this slurry is used to produce a green sheet 151 to be the piezoelectric layer 1 by a tape forming method such as a known doctor blade method. The thickness of the green sheet 151 is desirably 10 to 300 μm. When the thickness of the green sheet 151 is 10 μm or more, there is an advantage that the insulating property is enhanced and the step can be absorbed on the green sheet 151 side when the conductor patterns 157a and 157b are formed. On the other hand, when the thickness of the green sheet 151 is 300 μm or less, a thin piezoelectric element can be formed even if the number of stacked layers is increased, which is advantageous for downsizing. Further, thinning the piezoelectric layer 51 has an advantage that the amount of displacement can be increased.

次に、グリーンシート１５１上に、焼成後において、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂをなす第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、および第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂを形成する。これら第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、第１ダミー電極パターン１６５ａおよび第２ダミー電極パターン１６５ｂ用の導電性ペーストはＡｇ−Ｐｄ粉末に対して、バインダ、可塑剤、および必要に応じて圧電セラミックスの合成粉末であるＰＺＴ粉末等を添加混合し混合して得られる。これをグリーンシート１５１の上面にスクリーン印刷等のパターン形成法により形成する。その厚みは１〜４０μｍであることが望ましい。第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、および第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂの厚みが１μｍ以上であると印刷パターンのかすれや空隙などを低減でき有効面積を大きく確保できるという利点がある。第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、および第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂの厚みが４０μｍ以下であるとグリーンシート１５１上において第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂと第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂによる段差を小さくでき、製造コストを低減できるという利点がある。 Next, after firing on the green sheet 151, a first internal electrode pattern 157a and a second internal electrode pattern that form the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, and the second dummy electrode 65b. 157b, a first dummy electrode pattern 165a, and a second dummy electrode pattern 165b are formed. The conductive paste for the first internal electrode pattern 157a, the second internal electrode pattern 157b, the first dummy electrode pattern 165a, and the second dummy electrode pattern 165b has a binder, a plasticizer, and a necessity for the Ag-Pd powder. Accordingly, PZT powder or the like, which is a synthetic powder of piezoelectric ceramic, is added and mixed and mixed. This is formed on the upper surface of the green sheet 151 by a pattern forming method such as screen printing. The thickness is desirably 1 to 40 μm. When the thicknesses of the first internal electrode pattern 157a, the second internal electrode pattern 157b, the first dummy electrode pattern 165a, and the second dummy electrode pattern 165b are 1 μm or more, it is possible to reduce blurring or voids in the printed pattern and increase the effective area. There is an advantage that it can be secured. When the thickness of the first internal electrode pattern 157a, the second internal electrode pattern 157b, the first dummy electrode pattern 165a, and the second dummy electrode pattern 165b is 40 μm or less, the first internal electrode pattern 157a and the second internal electrode pattern 157a are formed on the green sheet 151. There is an advantage that the step due to the internal electrode pattern 157b, the first dummy electrode pattern 165a, and the second dummy electrode pattern 165b can be reduced, and the manufacturing cost can be reduced.

次に、グリーンシート１５１上に形成した第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、および第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂの中で、図８におけるＡ部分である第１内部電極パターン１５７ａの端部と第２ダミー電極パターン１６５ｂ、第２内部電極パターン１５７ｂの端部１５７ｂｂと第１ダミー電極パターン１６５ａとの間の領域にグリーンシート１５１の主成分である圧電セラミックスよりも低誘電率のセラミック粉末を含むセラミックペーストを印刷して低誘電率パターン１６３を形成する。この場合、Ａ部分の導体パターンの段差を低減することもできる。 Next, among the first internal electrode pattern 157a, the second internal electrode pattern 157b, the first dummy electrode pattern 165a, and the second dummy electrode pattern 165b formed on the green sheet 151, the A portion in FIG. Piezoelectric ceramics as a main component of the green sheet 151 in the region between the end portion of the first internal electrode pattern 157a and the second dummy electrode pattern 165b and the region between the end portion 157bb of the second internal electrode pattern 157b and the first dummy electrode pattern 165a. Also, a low dielectric constant pattern 163 is formed by printing a ceramic paste containing a low dielectric constant ceramic powder. In this case, the step of the conductor pattern of the A part can be reduced.

そして、上面に第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂおよび低誘電率パターン１６３が形成されたグリーンシート１５１を複数枚積層し、この積層体成形体とし、これを所定の温度で脱脂を行った後、９８０〜１１００℃で焼成することによって積層体６０を作製する。 Then, a plurality of green sheets 151 having a first internal electrode pattern 157a, a second internal electrode pattern 157b, a first dummy electrode pattern 165a, a second dummy electrode pattern 165b, and a low dielectric constant pattern 163 formed on the upper surface are laminated, After making this laminated body molded body degreased at a predetermined temperature, the laminated body 60 is produced by firing at 980 to 1100 ° C.

図９は、ダミー電極を有しない図１の構成の積層型圧電素子の製法を示す模式図である。図９に示すように第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂを形成しないで、その領域にまで低誘電率パターン１６３を広げて形成することで、上記図１の構成の積層型圧電素子を得ることができる。 FIG. 9 is a schematic diagram showing a method of manufacturing the multilayer piezoelectric element having the configuration of FIG. 1 having no dummy electrode. As shown in FIG. 9, without forming the first dummy electrode pattern 165a and the second dummy electrode pattern 165b, the low-dielectric constant pattern 163 is formed so as to extend to the region, so that the laminated piezoelectric element having the configuration shown in FIG. An element can be obtained.

図１０は、第３ダミー電極および第４ダミー電極を有する図７に示す構成の積層型圧電素子の製法を示す模式図である。例えば、第４ダミー電極パターン１６５ｄのみ印刷したグリーンシート１５１を形成して、その上面側に第１内部電極パターン１５７ａと第２ダミー電極パターン１６５ｂおよび低誘電率パターン１６３を形成したグリーンシート１５１を貼り合わせるように配置し、一方で、第３ダミー電極パターン１６５ｃのみ印刷したグリーンシート１５１を形成して、その上面側に第２内部電極パターン１５７ｂと第１ダミー電極パターン１６５ａおよび低誘電率パターン１６３を形成したグリーンシート１５１を貼り合わせるように配置し、これらを図１０のように交互に積層する。 FIG. 10 is a schematic view showing a method of manufacturing the multilayer piezoelectric element having the configuration shown in FIG. 7 having the third dummy electrode and the fourth dummy electrode. For example, a green sheet 151 on which only the fourth dummy electrode pattern 165d is printed is formed, and a green sheet 151 on which the first internal electrode pattern 157a, the second dummy electrode pattern 165b, and the low dielectric constant pattern 163 are formed is pasted on the upper surface. On the other hand, the green sheet 151 printed only with the third dummy electrode pattern 165c is formed, and the second internal electrode pattern 157b, the first dummy electrode pattern 165a, and the low dielectric constant pattern 163 are formed on the upper surface side thereof. The formed green sheets 151 are arranged so as to be bonded, and these are alternately stacked as shown in FIG.

ここで、コスト面から、第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂ、第３ダミー電極パターン１６５ｃ、第４ダミー電極パターン１６５ｄを形成するＡｇ−Ｐｄ粉末およびこの粉末の合金としてはＰｄ比率の低いものが望ましく、特に、Ｐｄ比率が３０質量％以下のものがより好ましい。このためには圧電体層１が１０５０℃以下で焼成できる材料であることが望ましく、例えば、ＰｂＺｒＯ_３−ＰｂＴｉＯ_３を主成分とし、副成分としてＰｂ（Ｙｂ_１／２Ｎｂ_１／２）Ｏ_３、Ｐｂ（Ｃｏ_１／３Ｎｂ_２／３）Ｏ_３などを含有させた材料を圧電体磁器に用いることが好ましい。変位特性に応じて、ＰｂサイトをＢａやＳｒ等のアルカリ土類金属元素で置換してもよい。また、第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、および第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂ、第３ダミー電極パターン１６５ｃ、第４ダミー電極パターン１６５ｄを構成するＡｇ−ＰｄはＡｇとＰｄの合金粉末を用いても、Ａｇ粉末とＰｄ粉末の混合物を用いても良い。なお、Ａｇ粉末とＰｄ粉末の混合物を用いた場合においても、焼成時にＡｇ−Ｐｄの合金が形成される。ＡｇとＰｄの合金粉末を用いるとＡｇのマイグレーションを抑制できるという利点がある。 Here, in terms of cost, the first internal electrode pattern 157a, the second internal electrode pattern 157b, the first dummy electrode pattern 165a, the second dummy electrode pattern 165b, the third dummy electrode pattern 165c, and the fourth dummy electrode pattern 165d are formed. As the Ag-Pd powder and the alloy of this powder, those having a low Pd ratio are desirable, and those having a Pd ratio of 30% by mass or less are particularly preferable. For this purpose, it is desirable that the piezoelectric layer 1 be a material that can be fired at 1050 ° C. or lower. For example, PbZrO ₃ —PbTiO ₃ is a main component and Pb (Yb _1/2 Nb _1/2 ) O _{3 is used} as a subcomponent. It is preferable to use a material containing Pb (Co _1/3 Nb _2/3 ) O ₃ or the like for the piezoelectric ceramic. Depending on the displacement characteristics, the Pb site may be replaced with an alkaline earth metal element such as Ba or Sr. Further, Ag-Pd constituting the first internal electrode pattern 157a, the second internal electrode pattern 157b, the first dummy electrode pattern 165a, the second dummy electrode pattern 165b, the third dummy electrode pattern 165c, and the fourth dummy electrode pattern 165d. May use an alloy powder of Ag and Pd or a mixture of Ag powder and Pd powder. Even when a mixture of Ag powder and Pd powder is used, an Ag—Pd alloy is formed during firing. The use of Ag and Pd alloy powder has an advantage that Ag migration can be suppressed.

また、第１内部電極パターン１５７ａ、第２内部電極パターン１５７ｂ、および第１ダミー電極パターン１６５ａ、第２ダミー電極パターン１６５ｂ、第３ダミー電極パターン１６５ｃ、第４ダミー電極パターン１６５ｄを形成するための導電性ペーストに添加する圧電材（圧電セラミックスの合成粉末）の比率は、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂと圧電体層５１との接合強度、ならびに第１内部電極５７ａ、第２内部電極５７ｂの抵抗値を低くするという理由から、焼成後における第１内部電極５７ａ、第２内部電極５７ｂ、または第１ダミー電極６５ａ、第２ダミー電極６５ｂ中に金属成分が７５〜９３質量％、残部として圧電材が７〜２５質量％含まれることが望ましい。 In addition, the first internal electrode pattern 157a, the second internal electrode pattern 157b, and the conductive for forming the first dummy electrode pattern 165a, the second dummy electrode pattern 165b, the third dummy electrode pattern 165c, and the fourth dummy electrode pattern 165d. The ratio of the piezoelectric material (piezoelectric ceramic synthetic powder) added to the conductive paste is determined by the bonding strength between the first internal electrode 57a, the second internal electrode 57b, the first dummy electrode 65a, the second dummy electrode 65b, and the piezoelectric layer 51. In addition, the first internal electrode 57a, the second internal electrode 57b, or the first dummy electrode 65a, the second dummy electrode 65b after firing are fired because the resistance values of the first internal electrode 57a and the second internal electrode 57b are lowered. It is desirable that the metal component is contained in an amount of 75 to 93% by mass and the balance is 7 to 25% by mass of the piezoelectric material.

次に、第１外部電極５８ａおよび第２外部電極５８ｂの形成方法を説明する。例えば、まず、粒径０．１〜１０μｍのＡｇ−Ｐｄの合金粉末からなる混合物にバインダを加えて外部電極ペーストを調製する。 Next, a method for forming the first external electrode 58a and the second external electrode 58b will be described. For example, first, an external electrode paste is prepared by adding a binder to a mixture made of an Ag—Pd alloy powder having a particle size of 0.1 to 10 μm.

調製した外部電極ペーストを積層体６０の第１側面５３ａおよび第２側面５３ｂの外部電極の形成面に印刷し、Ａｇ−Ｐｄ合金の融点以下の温度で焼き付けを行い、積層体６０の側面５３ａ、５３ｂにそれぞれ第１外部電極５８ａ、第２外部電極５８ｂを形成する。 The prepared external electrode paste is printed on the external electrode forming surfaces of the first side surface 53a and the second side surface 53b of the multilayer body 60, and baked at a temperature not higher than the melting point of the Ag—Pd alloy. A first external electrode 58a and a second external electrode 58b are formed on 53b, respectively.

この第１外部電極５８ａ、第２外部電極５８ｂの厚みは積層体６０の伸縮に追従できるという理由から５０μｍ以下が好ましく、積層体６０から剥離を防止するという点で５μｍ以上が好ましい。 The thickness of the first external electrode 58a and the second external electrode 58b is preferably 50 μm or less because it can follow the expansion and contraction of the laminate 60, and preferably 5 μm or more in terms of preventing peeling from the laminate 60.

外部電極ペースト中のＡｇ−Ｐｄ合金粉末中のＰｄ比率を質量比で０＜Ａ／（Ａ＋Ｂ）≦０．０５としたのは、第１外部電極５８ａおよび第２外部電極５８ｂにおけるＡｇのマイグレーションを抑制するとともに、これら第１外部電極５８ａ、第２外部電極５８ｂと、第１内部電極５７ａ、第２内部電極５７ｂ、第１ダミー電極６５ａ、第２ダミー電極６５ｂとの間のＰｄ濃度差を小さくすることで、相互拡散による接合強度を高められるという理由からである。 The reason why the Pd ratio in the Ag—Pd alloy powder in the external electrode paste is 0 <A / (A + B) ≦ 0.05 in terms of mass ratio is that Ag migration in the first external electrode 58a and the second external electrode 58b is performed. While suppressing, the Pd density | concentration difference between these 1st external electrodes 58a and 2nd external electrodes 58b, and 1st internal electrode 57a, 2nd internal electrode 57b, 1st dummy electrode 65a, and 2nd dummy electrode 65b is made small. This is because the bonding strength by mutual diffusion can be increased.

また、上記外部電極ペーストには半田との濡れ性を低下させない程度のガラスフリットを含有してもよい。ガラスフリットの含有量が多いと、半田濡れ性が悪くリード線５８ａａ、５８ｂｂの第１外部電極５８ａ、第２外部電極５８ｂへの接合強度が低下し、駆動中にリード線５８ａａ、５８ｂｂが外れてしまう恐れがあるからである。 Further, the external electrode paste may contain a glass frit that does not reduce the wettability with the solder. If the glass frit content is large, the solder wettability is poor and the bonding strength of the lead wires 58aa and 58bb to the first external electrode 58a and the second external electrode 58b is reduced, and the lead wires 58aa and 58bb are disconnected during driving. This is because there is a risk of it.

その後、第１外部電極５８ａ、第２外部電極５８ｂのそれぞれにリード線５８ａａ、５８ｂｂを半田等で接続し、リード線５８ａａ、５８ｂｂを介して一対の第１外部電極５８ａおよび第２外部電極５８ｂに１〜３ｋＶ／ｍｍの直流電圧を印加し、積層体６０を分極処理することによって、製品としての積層型圧電素子が完成する。 Thereafter, the lead wires 58aa and 58bb are connected to the first external electrode 58a and the second external electrode 58b with solder or the like, respectively, and the pair of first external electrodes 58a and second external electrodes 58b are connected via the lead wires 58aa and 58bb. A laminated piezoelectric element as a product is completed by applying a DC voltage of 1 to 3 kV / mm to polarize the laminated body 60.

次に、得られた積層型圧電素子はリード線５８ａａ、５８ｂｂを外部の電圧供給装置に接続してリード線５８ａａ、５８ｂｂおよび第１外部電極５８ａ、第２外部電極５８ｂを介して第１内部電極５７ａ、第２内部電極５７ｂに電圧を印加することにより各圧電体層１に逆圧電効果を生じさせることができ、これにより大きな変位が得られ、例えば、エンジンに燃料を噴射供給する自動車用燃料噴射弁として機能させることができる。 Next, the obtained multilayer piezoelectric element has the lead wires 58aa and 58bb connected to an external voltage supply device, and the first internal electrode is connected via the lead wires 58aa and 58bb, the first external electrode 58a and the second external electrode 58b. By applying a voltage to the second internal electrode 57b, a reverse piezoelectric effect can be generated in each piezoelectric layer 1, thereby obtaining a large displacement. For example, a fuel for an automobile that injects and supplies fuel to the engine It can function as an injection valve.

本発明の積層型圧電素子を以下のようにして作製した。圧電体層となる圧電セラミックスとして、下記式で表されるチタン酸ジルコン酸鉛を主成分とする組成物を用いた。 The multilayer piezoelectric element of the present invention was produced as follows. As the piezoelectric ceramic used as the piezoelectric layer, a composition mainly composed of lead zirconate titanate represented by the following formula was used.

組成物はＰｂ_３Ｏ_４、ＺｒＯ_２、ＴｉＯ_２、ＢａＣＯ_３、ＳｒＣＯ_３、ＷＯ_３およびＹｂ_２Ｏ_３を用いて、Ｐｂ_{０．９８３}（Ｂａ，Ｓｒ）_０．０５Ｗ_０．０１Ｙｂ_{０．００７}（Ｚｒ_{０．５１５}Ｔｉ_{０．４８５}）_{０．９８３}Ｏ_３＋αとなるように組成を調製した。 The composition is Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , BaCO ₃ , SrCO ₃ , WO ₃ and Yb ₂ O ₃ , and Pb _0.983 (Ba, Sr) _0.05 W _0.01 Yb _{0. The} composition was adjusted to ₀₀₇ (Zr _0.515 Ti _0.485 ) _0.983 O _{3 + α} .

次に、上記組成の圧電セラミックスの仮焼粉末、バインダ、および可塑剤を混合したスラリを調製し、ドクターブレード法により厚み１００μｍのグリーンシートを作製した。 Next, a slurry in which the calcined powder of piezoelectric ceramic having the above composition, a binder, and a plasticizer were mixed was prepared, and a green sheet having a thickness of 100 μm was prepared by a doctor blade method.

次に、このグリーンシートの片面に導電性ペーストを印刷して、所望の構成に応じて第１内部電極パターン、第２内部電極パターン、第１ダミー電極パターン、第２ダミー電極パターンを形成した。 Next, a conductive paste was printed on one side of the green sheet to form a first internal electrode pattern, a second internal electrode pattern, a first dummy electrode pattern, and a second dummy electrode pattern according to a desired configuration.

なお、図７の積層型圧電素子を作製する場合には、厚み５０μｍのグリーンシートを用意し、第３ダミー電極パターンのみ、もしくは第４ダミー電極パターンのみを形成したグリーンシートを予め作製しておき、このグリーンシートの第３ダミー電極パターン、もしくは第４ダミー電極パターン側に印刷パターンのない厚み５０μｍのグリーンシートを重ねたものを作製し、この第３ダミー電極パターンのみ、もしくは第４ダミー電極パターンのみ有するグリーンシートの表面に第１内部電極パターン、第２内部電極パターン、第１ダミー電極パターンおよび第２ダミー電極パターンを形成した。 7 is prepared, a green sheet having a thickness of 50 μm is prepared, and a green sheet on which only the third dummy electrode pattern or only the fourth dummy electrode pattern is formed is prepared in advance. Then, a third dummy electrode pattern of this green sheet or a green sheet having a thickness of 50 μm without a printed pattern is superimposed on the fourth dummy electrode pattern side, and only this third dummy electrode pattern or the fourth dummy electrode pattern A first internal electrode pattern, a second internal electrode pattern, a first dummy electrode pattern, and a second dummy electrode pattern were formed on the surface of the green sheet having only the green sheet.

導電性ペーストの組成はＡｇ：Ｐｄ＝７０：３０（質量％）およびＡｇ：Ｐｄ＝９０：１０（質量％）を調製し、この金属成分８５質量％に対してグリーンシートに用いた圧電セラミックスの仮焼粉末１５質量％を加えた。また、第１内部電極パターンおよび第２内部電極パターン、第１ダミー電極パターンおよび第２ダミー電極パターンの厚みはいずれも３μｍとした。積層型圧電素子の試料を作製する場合の内部電極パターン、第１ダミー電極、第２ダミー電極、第３ダミー電極および第４ダミー電極の組成は同じにした。 The composition of the conductive paste was prepared as Ag: Pd = 70: 30 (mass%) and Ag: Pd = 90: 10 (mass%), and the piezoelectric ceramic used for the green sheet with respect to 85 mass% of the metal component. 15% by mass of calcined powder was added. The thicknesses of the first internal electrode pattern, the second internal electrode pattern, the first dummy electrode pattern, and the second dummy electrode pattern were all 3 μm. The composition of the internal electrode pattern, the first dummy electrode, the second dummy electrode, the third dummy electrode, and the fourth dummy electrode when producing a sample of the multilayer piezoelectric element was made the same.

次に、図１の積層型圧電素子を作製する場合には、グリーンシート上に形成した第１内部電極パターン、第２内部電極パターンの端部側に低誘電率パターンを形成した。 Next, when the multilayer piezoelectric element of FIG. 1 was produced, a low dielectric constant pattern was formed on the end side of the first internal electrode pattern and the second internal electrode pattern formed on the green sheet.

図４および図７の積層型圧電素子を作製する場合には、グリーンシート上に形成した第１内部電極パターン、第２内部電極パターンの端部と第１ダミー電極パターン、第２ダミー電極パターンとのそれぞれの間（図４の積層体６０における絶縁部６４）に少なくとも内部電極パターンと同一厚みで、圧電体層の主成分であるチタン酸ジルコン酸鉛よりも比誘電率の低いセラミックス粉末（チタン酸鉛、チタンビスマス酸ストロンチウム、チタンビスマス酸バリウム）をそれぞれ含有するセラミックペーストを印刷して低誘電率パターンを形成した。 4 and 7, the first internal electrode pattern formed on the green sheet, the end of the second internal electrode pattern, the first dummy electrode pattern, the second dummy electrode pattern, Ceramic powder (titanium) having a relative dielectric constant lower than that of lead zirconate titanate, which is the main component of the piezoelectric layer, at least in the same thickness as the internal electrode pattern (in the insulating portion 64 in the laminate 60 in FIG. 4). A ceramic paste containing lead acid, strontium titanium bismuth, and barium titanium bismuthate was printed to form a low dielectric constant pattern.

次に、上記第１内部電極パターン、第２内部電極パターン、第１ダミー電極パターン、第２ダミー電極パターンおよび低誘電率パターンを形成したグリーンシートをそれぞれの７０枚積層し、１０７５℃で焼成して図１に示す積層体を得た。作製した積層体の寸法は外辺が７×７ｍｍ、第１内部電極、第２内部電極は第１ダミー電極、第２ダミー電極および絶縁領域（低誘電率パターン）の長辺に平行な方向の幅を６ｍｍとし、ダミー電極および絶縁領域（低誘電率パターン）を設けない各電極パターンに長辺に垂直な方向の幅は６．５ｍｍとした。第１〜４ダミー電極および絶縁領域（低誘電率パターン）の幅は０．５ｍｍとした。 Next, 70 green sheets on which the first internal electrode pattern, the second internal electrode pattern, the first dummy electrode pattern, the second dummy electrode pattern, and the low dielectric constant pattern are formed are stacked and fired at 1075 ° C. Thus, the laminate shown in FIG. 1 was obtained. The dimensions of the produced laminate are 7 × 7 mm on the outer side, the first internal electrode and the second internal electrode are in the direction parallel to the first dummy electrode, the second dummy electrode, and the long side of the insulating region (low dielectric constant pattern). The width was 6 mm, and the width in the direction perpendicular to the long side of each electrode pattern without the dummy electrode and the insulating region (low dielectric constant pattern) was 6.5 mm. The widths of the first to fourth dummy electrodes and the insulating region (low dielectric constant pattern) were 0.5 mm.

次に、Ａｇ１００質量％、Ａｇ：Ｐｄ＝９８：２およびＡｇ：Ｐｄ＝９５：５の比率の合金粉末のそれぞれにバインダを混合して３種類の外部電極ペーストを調製した。次に、調製した外部電極ペーストを積層体の側面の所定の領域にスクリーン印刷により印刷を行い、乾燥した後８００℃で３０分の焼き付けを行い第１、第２外部電極を形成した。第１、第２外部電極の厚みは平均で２５μｍ、幅は平均で２ｍｍとした。 Next, a binder was mixed with each of the alloy powders in a ratio of Ag 100 mass%, Ag: Pd = 98: 2 and Ag: Pd = 95: 5 to prepare three types of external electrode pastes. Next, the prepared external electrode paste was printed on a predetermined region on the side surface of the laminate by screen printing, dried, and baked at 800 ° C. for 30 minutes to form first and second external electrodes. The first and second external electrodes had an average thickness of 25 μm and an average width of 2 mm.

その後、第１、第２外部電極にリード線を接続し３ｋＶ／ｍｍの直流電界を１５分間印加して分極処理を行い、図１、４、７に示すような積層型圧電素子である積層型圧電アクチュエータを作製した。これらの積層型圧電アクチュエータを室温で０〜＋１８５Ｖの交流電界を１５０Ｈｚの周波数で印加して１．５億サイクルまで駆動試験を行った。 Thereafter, lead wires are connected to the first and second external electrodes, a 3 kV / mm DC electric field is applied for 15 minutes to perform polarization treatment, and the multilayer piezoelectric element as shown in FIGS. A piezoelectric actuator was fabricated. These laminated piezoelectric actuators were subjected to a driving test up to 150 million cycles by applying an AC electric field of 0 to +185 V at a frequency of 150 Hz at room temperature.

比較例として積層体中に低誘電率パターンを形成しないものを作製し、これも同様の評価を行った。試料数は各１０個とし変位量は平均値を求めた。

As a comparative example, a laminate in which a low dielectric constant pattern was not formed was produced, and the same evaluation was performed. The number of samples was 10 for each, and the average amount of displacement was determined.

表１の結果から明らかなように、上記のようにして得られた積層型圧電素子アクチュエータに対して１８５Ｖの直流電圧を印加したところ、本発明の積層型圧電アクチュエータである試料Ｎｏ．１〜７、９、１０では初期の積層方向の最大変位量が９．１μｍ以上であり、１億サイクルまでの駆動試験後においても積層方向の最大変位量は８．９μｍ以上であった。 As is clear from the results in Table 1, when a DC voltage of 185 V was applied to the multilayer piezoelectric element actuator obtained as described above, sample No. 1 which is the multilayer piezoelectric actuator of the present invention was obtained. In 1 to 7, 9, and 10, the initial maximum displacement amount in the stacking direction was 9.1 μm or more, and the maximum displacement amount in the stacking direction was 8.9 μm or more even after the driving test up to 100 million cycles.

特に、外部電極をＡｇ：Ｐｄ＝９５：５（質量％）とし、第２のダミー電極を設けた試料Ｎｏ．５では、外部電極にスパークや断線等の異常が見られず、１．５億サイクル後においても最大変位量が９．１μｍであった。 In particular, the external electrode is Ag: Pd = 95: 5 (mass%), and the sample No. 2 is provided with the second dummy electrode. In No. 5, no abnormality such as spark or disconnection was observed in the external electrode, and the maximum displacement was 9.1 μm even after 150 million cycles.

一方、比較例として積層体中に低誘電率パターンを形成しなかった試料Ｎｏ．８、１１では、１８５Ｖの直流電圧を印加した初期の積層方向の変位量が８．５μｍおよび８．６μｍであった。これは、第１内部電極および第２内部電極のそれぞれの端部と、第１ダミー電極、第２ダミー電極とのそれぞれの間の絶縁領域の圧電体層が第１内部電極および第２内部電極のそれぞれの面内の方向に沿って分極したために活性部の変位が小さくなったためである。 On the other hand, as a comparative example, a sample No. 1 in which a low dielectric constant pattern was not formed in the laminate. 8 and 11, the initial displacement amounts in the stacking direction when a DC voltage of 185 V was applied were 8.5 μm and 8.6 μm. This is because the piezoelectric layers in the insulating regions between the end portions of the first internal electrode and the second internal electrode and the first dummy electrode and the second dummy electrode are the first internal electrode and the second internal electrode, respectively. This is because the displacement of the active portion is reduced because of polarization along the in-plane directions.

本発明の積層型圧電素子を示す斜視図である。It is a perspective view which shows the lamination type piezoelectric element of this invention. 図１のＡ−Ａ’における縦断面図である。It is a longitudinal cross-sectional view in A-A 'of FIG. 図２の拡大図であり、第１内部電極、第２内部電極とから形成される活性部、不活性部（比誘電率の低い絶縁部）を説明するための模式図である。FIG. 3 is an enlarged view of FIG. 2, and is a schematic diagram for explaining an active portion and an inactive portion (insulating portion having a low relative dielectric constant) formed from a first internal electrode and a second internal electrode. ダミー電極を有する本発明の積層型圧電素子を示す斜視図である。It is a perspective view which shows the lamination type piezoelectric element of this invention which has a dummy electrode. 図４のＡ−Ａ’における縦断面図である。It is a longitudinal cross-sectional view in A-A 'of FIG. 図５の拡大図であり、第１内部電極、第２内部電極、第１ダミー電極および第２ダミー電極とから形成される活性部、不活性部および比誘電率の低い絶縁部を説明するための模式図である。FIG. 6 is an enlarged view of FIG. 5 for explaining an active portion, an inactive portion, and an insulating portion having a low relative dielectric constant formed by the first internal electrode, the second internal electrode, the first dummy electrode, and the second dummy electrode. FIG. 本発明のもう一つの積層型圧電素子を示す部分的断面模式図である。It is a partial cross-sectional schematic diagram which shows another laminated piezoelectric element of this invention. ダミー電極を有する本発明の積層型圧電素子の製法を示す模式図である。It is a schematic diagram which shows the manufacturing method of the lamination type piezoelectric element of this invention which has a dummy electrode. ダミー電極を有しない図１の構成の積層型圧電素子の製法を示す模式図である。It is a schematic diagram which shows the manufacturing method of the lamination type piezoelectric element of the structure of FIG. 1 which does not have a dummy electrode. 第３ダミー電極および第４ダミー電極を有する図７に示す構成の積層型圧電素子の製法を示す模式図である。It is a schematic diagram which shows the manufacturing method of the laminated piezoelectric element of the structure shown in FIG. 7 which has a 3rd dummy electrode and a 4th dummy electrode. 従来の積層型圧電アクチュエータを示す断面模式図である。It is a cross-sectional schematic diagram showing a conventional multilayer piezoelectric actuator. ダミー電極を有する従来の積層型圧電アクチュエータを示す部分的断面模式図である。It is a partial cross-sectional schematic diagram which shows the conventional laminated piezoelectric actuator which has a dummy electrode.

符号の説明Explanation of symbols

１、５１、１１１・・・・・・・圧電体層
３ａ、５３ａ・・・・・・・・・第１側面
３ｂ、５３ｂ・・・・・・・・・第２側面
５、５５・・・・・・・・・・・圧電体
７ａ、５７ａ、１１７ａ・・・・第１内部電極
７ｂ、５７ｂ、１１７ｂ・・・・第２内部電極
８ａ、５８ａ、１１８ａ・・・・第１外部電極
８ｂ、５８ｂ、１１８ｂ・・・・第２外部電極
１４、６４、１２４・・・・・・絶縁部
６５ａ、１１５ａ・・・・・・・第１ダミー電極
６５ｂ、１１５ｂ・・・・・・・第２ダミー電極
１１５ｃ・・・・・・・・・・・第３ダミー電極
１１５ｄ・・・・・・・・・・・第４ダミー電極 1, 51, 111 ········· Piezoelectric layer 3a, 53a ·········· First side surface 3b, 53b ··········· Second side surface 5, 55 ··· ········ Piezoelectric body 7a, 57a, 117a ··· First internal electrode 7b, 57b, 117b ··· Second internal electrode 8a, 58a, 118a ··· First external electrode 8b, 58b, 118b... Second external electrode 14, 64, 124... Insulating part 65a, 115a .. .. First dummy electrode 65b, 115b. 2nd dummy electrode 115c ... 3rd dummy electrode 115d ... 4th dummy electrode

Claims

複数の圧電体層が積層され、対向する第１側面および第２側面を有する圧電体の内部に、第１内部電極が前記第１側面に、第２内部電極が前記第２側面にそれぞれ引き出されて配置されており、前記第１側面および前記第２側面にはそれぞれ前記第１内部電極に接続された第１外部電極、および前記第２内部電極に接続された第２外部電極を備えた積層型圧電素子であって、前記第１内部電極の端部と前記第２側面との間の前記第１内部電極の延長上の領域、および前記第２内部電極の端部と前記第１側面との間の前記第２内部電極の延長上の領域に、前記圧電体層よりも比誘電率の低い絶縁部を設けたことを特徴とする積層型圧電素子。 A plurality of piezoelectric layers are stacked, and a first internal electrode is drawn out to the first side face and a second internal electrode is drawn out to the second side face inside a piezoelectric body having first and second side faces facing each other. And a first external electrode connected to the first internal electrode and a second external electrode connected to the second internal electrode on the first side surface and the second side surface, respectively. A region on the extension of the first internal electrode between the end portion of the first internal electrode and the second side surface, and the end portion of the second internal electrode and the first side surface. An insulating part having a relative dielectric constant lower than that of the piezoelectric layer is provided in a region on the extension of the second internal electrode between the stacked piezoelectric elements.

複数の圧電体層が積層され、対向する第１側面および第２側面を有する圧電体の内部に配置された第１内部電極および第２内部電極を備え、前記第１内部電極が前記圧電体の前記第１側面に、前記第２内部電極が前記圧電体の前記第２側面に引き出されて配置されており、前記第１側面および前記第２側面にはそれぞれ前記第１内部電極に接続された第１外部電極、および前記第２内部電極に接続された第２外部電極を備え、前記第１内部電極の端部と前記第２側面との間の前記第１内部電極の延長上の領域に、前記第２外部電極に接続された第２ダミー電極が前記第１内部電極の端部との間に絶縁部を介して形成され、前記第２内部電極の端部と前記第１側面との間の前記第２内部電極の延長上の領域に、前記第１外部電極に接続された第１ダミー電極が前記第２内部電極の端部との間に絶縁部を介して形成されている積層型圧電素子であって、前記絶縁部の比誘電率を前記圧電体層よりも低くしたことを特徴とする積層型圧電素子。 A plurality of piezoelectric layers are stacked, and each includes a first internal electrode and a second internal electrode disposed inside a piezoelectric body having a first side surface and a second side surface facing each other, wherein the first internal electrode is formed of the piezoelectric body. The second internal electrode is arranged on the first side surface so as to be drawn out to the second side surface of the piezoelectric body, and the first side surface and the second side surface are connected to the first internal electrode, respectively. A first external electrode, and a second external electrode connected to the second internal electrode, in a region on the extension of the first internal electrode between the end of the first internal electrode and the second side surface A second dummy electrode connected to the second external electrode is formed between the end portion of the first internal electrode and an end portion of the first internal electrode, and an end portion of the second internal electrode and the first side surface In the region on the extension of the second internal electrode between, the first external electrode connected to the first external electrode A laminated piezoelectric element in which a dummy electrode is formed between an end portion of the second internal electrode via an insulating portion, wherein a relative dielectric constant of the insulating portion is lower than that of the piezoelectric layer. A multilayer piezoelectric element that is characterized.

前記圧電体層がチタン酸ジルコン酸鉛によって形成されており、前記絶縁部がチタン酸鉛、チタン酸ビスマス酸ストロンチウムおよびチタン酸ビスマス酸バリウムから選ばれる１種によって形成されている請求項１または２に記載の積層型圧電素子。 3. The piezoelectric layer is formed of lead zirconate titanate, and the insulating portion is formed of one selected from lead titanate, strontium bismuth titanate and barium bismuthate titanate. The laminated piezoelectric element according to 1.

前記第１ダミー電極と前記第１内部電極との間の前記圧電体層中に前記第１外部電極に接続された第３ダミー電極が設けられ、前記第２ダミー電極と前記第２内部電極との間の前記圧電体層中に、前記第２外部電極に接続された第４ダミー電極が設けられた請求項２に記載の積層型圧電素子。 A third dummy electrode connected to the first external electrode is provided in the piezoelectric layer between the first dummy electrode and the first internal electrode, and the second dummy electrode, the second internal electrode, The multilayer piezoelectric element according to claim 2, wherein a fourth dummy electrode connected to the second external electrode is provided in the piezoelectric layer between the layers.