JP6226679B2

JP6226679B2 - Polarization direction inspection method, polarization direction inspection device, and piezoelectric element manufacturing method

Info

Publication number: JP6226679B2
Application number: JP2013209681A
Authority: JP
Inventors: 大西　孝生; 孝生大西; 政之植谷; 浩紀濱田
Original assignee: NGK Insulators Ltd; NGK Ceramic Device Co Ltd
Current assignee: NGK Insulators Ltd; NGK Ceramic Device Co Ltd
Priority date: 2013-10-04
Filing date: 2013-10-04
Publication date: 2017-11-08
Anticipated expiration: 2033-10-04
Also published as: JP2015076420A

Description

本発明は、圧電効果（逆圧電効果）を有する素子の分極方向を判別する分極方向検査方法及び分極方向検査装置、並びに圧電素子の製造方法に関する。 The present invention relates to a polarization direction inspection method, a polarization direction inspection apparatus, and a method for manufacturing a piezoelectric element that determine the polarization direction of an element having a piezoelectric effect (reverse piezoelectric effect).

従来、圧電効果（逆圧電効果）を有する素子の分極方向を判別する方法として、以下の方法が採用されてきた。 Conventionally, the following method has been adopted as a method for determining the polarization direction of an element having a piezoelectric effect (reverse piezoelectric effect).

一般に、圧電効果（逆圧電効果）を有する素子である、分極処理された圧電素子に分極方向と同じ方向に電界を印加すると、圧電素子のｄ３１方向（電界の方向と直交する方向）は逆圧電効果によって収縮し、逆方向に電界を印加すると、ｄ３１方向は伸張する。そこで、分極処理された圧電素子に対して、任意の方向に矩形あるいはサイン波等の交流電界を印加し、その電界の方向に対する圧電素子の歪み状態を測定することで、分極方向を判別するようにしている。なお、圧電トランスの分極方向を検査する方法として、特許文献１に記載がある。 In general, when an electric field is applied to a polarized piezoelectric element, which is an element having a piezoelectric effect (reverse piezoelectric effect), in the same direction as the polarization direction, the d31 direction of the piezoelectric element (direction perpendicular to the direction of the electric field) is reverse piezoelectric. When contracted by the effect and an electric field is applied in the opposite direction, the d31 direction expands. Therefore, it is possible to determine the polarization direction by applying an alternating electric field such as a rectangle or a sine wave to the piezoelectric element subjected to the polarization treatment and measuring the strain state of the piezoelectric element with respect to the direction of the electric field. I have to. Patent Document 1 describes a method for inspecting the polarization direction of a piezoelectric transformer.

特開２００３−０５１６２８号公報JP 2003-051628 A

しかしながら、従来の方法は、その前提として、圧電効果（逆圧電効果）を有する素子の歪量を測定するために、レーザードップラー振動計等の大掛かりな装置が必要になる。また、正確に歪量を測定するために、素子を基台等に接着剤で固定する必要があり、結果的に破壊検査になる。破壊検査の場合は、抜取り検査方式を採用するしかなく、全数保証を確保できないという問題がある。 However, the conventional method requires a large-scale apparatus such as a laser Doppler vibrometer in order to measure the strain amount of an element having a piezoelectric effect (inverse piezoelectric effect). Further, in order to accurately measure the amount of strain, it is necessary to fix the element to the base with an adhesive, resulting in a destructive inspection. In the case of destructive inspection, the sampling inspection method can only be adopted, and there is a problem that it is impossible to ensure the total guarantee.

本発明はこのような課題を考慮してなされたものであり、精度向上のために破壊検査を行う必要がなく、圧電効果（逆圧電効果）を有する素子の分極方向を容易に判別することができ、全数保証を確保することができる分極方向検査方法及び分極方向検査装置を提供することを目的とする。 The present invention has been made in view of such problems, and it is not necessary to perform a destructive inspection for improving accuracy, and the polarization direction of an element having a piezoelectric effect (reverse piezoelectric effect) can be easily determined. An object of the present invention is to provide a polarization direction inspection method and a polarization direction inspection apparatus capable of ensuring all the guarantees.

また、本発明の他の目的は、分極方向が判明した圧電効果（逆圧電効果）を有する素子、あるいは分極方向がそれぞれ同じ方向とされた圧電効果（逆圧電効果）を有する素子を製造することができ、分極方向が保証された圧電効果（逆圧電効果）を有する素子を市場に供給することができる圧電効果（逆圧電効果）を有する素子の製造方法を提供することができる。 Another object of the present invention is to produce an element having a piezoelectric effect (reverse piezoelectric effect) whose polarization direction is known, or an element having a piezoelectric effect (reverse piezoelectric effect) in which the polarization directions are the same. Therefore, it is possible to provide a method for manufacturing an element having a piezoelectric effect (inverse piezoelectric effect) that can supply an element having a piezoelectric effect (inverse piezoelectric effect) with a guaranteed polarization direction to the market.

［１］第１の本発明に係る分極方向検査方法は、素子の分極方向を判別する分極方向検査方法であって、前記素子の電気的特性を少なくとも２条件で測定する測定ステップと、得られた少なくとも２つの測定値を比較して前記素子の分極方向を判別する判別ステップとを有することを特徴とする。 [1] A polarization direction inspection method according to the first aspect of the present invention is a polarization direction inspection method for determining the polarization direction of an element, and includes a measurement step for measuring electrical characteristics of the element under at least two conditions. And a determination step of comparing the polarization direction of the element by comparing at least two measured values.

これにより、精度向上のために破壊検査を行う必要がなく、圧電効果（逆圧電効果）を有する素子の分極方向を容易に判別することができ、全数保証を確保することができる。 Thereby, it is not necessary to perform a destructive inspection for improving accuracy, the polarization direction of the element having the piezoelectric effect (reverse piezoelectric effect) can be easily determined, and the total guarantee can be ensured.

［２］第１の本発明において、前記測定ステップは、少なくとも２条件での前記測定を連続して行ってもよい。 [2] In the first aspect of the present invention, the measurement step may continuously perform the measurement under at least two conditions.

［３］第１の本発明において、少なくとも前記測定ステップは、１０℃以上の温度変化がない環境で行うことが好ましい。 [3] In the first aspect of the present invention, at least the measurement step is preferably performed in an environment where there is no temperature change of 10 ° C. or more.

［４］第１の本発明において、前記素子は、分極処理された圧電素子であってもよい。 [4] In the first aspect of the present invention, the element may be a polarized piezoelectric element.

［５］［４］において、前記測定ステップは、前記圧電素子をバイアス電界０ｋＶ／ｍｍの状態で、前記圧電素子の静電容量を測定する第１ステップと、前記圧電素子にバイアス電界０．１〜１ｋＶ／ｍｍを印加した状態で、前記圧電素子の静電容量を測定する第２ステップと、を有し、前記判別ステップは、前記第１ステップで得られた第１測定値と、前記第２ステップで得られた第２測定値とを比較し、前記第１測定値に対する前記第２測定値の高低とバイアス電界方向とに基づいて、前記圧電素子の分極方向を判別することを特徴とする。 [5] In [4], the measurement step includes a first step of measuring a capacitance of the piezoelectric element in a state where the piezoelectric element has a bias electric field of 0 kV / mm, and a bias electric field of 0.1 on the piezoelectric element. A second step of measuring a capacitance of the piezoelectric element in a state where ˜1 kV / mm is applied, wherein the determining step includes the first measured value obtained in the first step, The second measurement value obtained in two steps is compared, and the polarization direction of the piezoelectric element is determined based on the level of the second measurement value with respect to the first measurement value and the direction of the bias electric field. To do.

これにより、精度向上のために破壊検査を行う必要がなく、分極処理された圧電素子の分極方向を容易に判別することができ、全数保証を確保することができる。しかも、実質的にバイアス電界を１回だけ印加した静電容量測定を追加するだけであるため、短時間で判定することができる。 Thereby, it is not necessary to perform a destructive inspection for improving accuracy, the polarization direction of the piezoelectric element subjected to the polarization treatment can be easily determined, and the guarantee of the total number can be ensured. In addition, since it is only necessary to add capacitance measurement in which the bias electric field is applied only once, it can be determined in a short time.

［６］この場合、前記第２ステップで前記圧電素子に印加する前記バイアス電界は、前記圧電素子の抗電界の８０％以下であることが好ましい。圧電素子の分極状態に影響を与えることがなく、バイアス電界の印加を止めた段階で、バイアス電界が０ｋＶ／ｍｍの時点の分極状態に戻る。圧電素子に抗電界の８０％以上のバイアス電界を印加すると、圧電素子が再分極あるいは脱分極する等して、バイアス電界が０ｋＶ／ｍｍで測定した時の分極状態から大きく変化するため、バイアス電界方向に対する分極方向を判別することができない。 [6] In this case, it is preferable that the bias electric field applied to the piezoelectric element in the second step is 80% or less of a coercive electric field of the piezoelectric element. The polarization state of the piezoelectric element is not affected, and when the application of the bias electric field is stopped, the polarization state returns to the polarization state at the time when the bias electric field is 0 kV / mm. When a bias electric field of 80% or more of the coercive electric field is applied to the piezoelectric element, the piezoelectric element repolarizes or depolarizes, and the bias electric field greatly changes from the polarization state when measured at 0 kV / mm. The polarization direction relative to the direction cannot be determined.

［７］また、前記測定ステップは、前記第１ステップを行った後に前記第２ステップを行うようにしている。従来、第１ステップのみで圧電素子が分極処理されたかどうかを判定していた工程で、連続して第２測定値を確認することができるため、大掛かりな工程変更を必要としない。 [7] Further, in the measurement step, the second step is performed after the first step. Conventionally, since the second measurement value can be confirmed continuously in the process of determining whether or not the piezoelectric element has been subjected to the polarization process only in the first step, no major process change is required.

［８］［５］において、前記測定ステップは、前記圧電素子を分極処理した後に、前記圧電素子が分極処理されたかどうかを判定するための静電容量測定装置を兼用して行ってもよい。 [8] In [5], the measurement step may be performed also using a capacitance measuring device for determining whether the piezoelectric element has been polarized after the piezoelectric element has been polarized.

［９］第２の本発明に係る分極方向検査装置は、分極処理された圧電素子の分極方向を判別する分極方向検査装置であって、前記圧電素子の電気的特性を少なくとも２条件で測定する測定部と、得られた少なくとも２つの測定値を比較して前記圧電素子の分極方向を判別する判別部とを有することを特徴とする。 [9] A polarization direction inspection apparatus according to the second aspect of the present invention is a polarization direction inspection apparatus for determining the polarization direction of a piezoelectric element subjected to polarization processing, and measures the electrical characteristics of the piezoelectric element under at least two conditions. It has a measuring part and a discriminating part for discriminating the polarization direction of the piezoelectric element by comparing at least two obtained measurement values.

［１０］この場合、さらに、静電容量測定手段と、電界印加手段とを有し、前記測定部は、前記静電容量測定手段及び前記電界印加手段を制御して、前記圧電素子をバイアス電界０ｋＶ／ｍｍの状態で、前記圧電素子の静電容量を測定する第１静電容量測定部と、前記静電容量測定手段及び前記電界印加手段を制御して、前記圧電素子にバイアス電界０．１〜１ｋＶ／ｍｍを印加した状態で、前記圧電素子の静電容量を測定する第２静電容量測定部と、を有し、前記判別部は、前記第１静電容量測定部にて得られた第１測定値と、前記第２静電容量測定部で得られた第２測定値とを比較し、前記第１測定値に対する前記第２測定値の高低とバイアス電界方向とに基づいて、前記圧電素子の分極方向を判別してもよい。 [10] In this case, it further includes a capacitance measuring unit and an electric field applying unit, and the measuring unit controls the capacitance measuring unit and the electric field applying unit so as to make the piezoelectric element a bias electric field. In the state of 0 kV / mm, the first electrostatic capacity measuring unit for measuring the electrostatic capacity of the piezoelectric element, the electrostatic capacity measuring means, and the electric field applying means are controlled to apply a bias electric field of 0. A second capacitance measuring unit that measures the capacitance of the piezoelectric element in a state in which 1-1 kV / mm is applied, and the determination unit is obtained by the first capacitance measuring unit. The obtained first measurement value is compared with the second measurement value obtained by the second capacitance measuring unit, and based on the level of the second measurement value with respect to the first measurement value and the bias electric field direction. The polarization direction of the piezoelectric element may be determined.

［１１］さらに、前記圧電素子の一対の電極のうち、特定の電極を検出する電極検出部を有し、前記第２静電容量測定部は、前記特定の電極を基準に、前記一対の電極間に一定方向の前記バイアス電界を印加してもよい。 [11] Further, an electrode detection unit that detects a specific electrode of the pair of electrodes of the piezoelectric element is provided, and the second capacitance measurement unit is configured to use the pair of electrodes based on the specific electrode. The bias electric field in a certain direction may be applied between them.

［１２］この場合、前記一対の電極のうち、一方の電極に方向識別マークが施され、前記電極検出部は、前記方向識別マークを画像認識し、認識した前記方向識別マークに対応した電極を前記特定の電極として検出してもよい。 [12] In this case, one of the pair of electrodes is provided with a direction identification mark, and the electrode detection unit recognizes the direction identification mark as an image, and detects an electrode corresponding to the recognized direction identification mark. The specific electrode may be detected.

［１３］あるいは、前記圧電素子の上面に形成された電極と、前記圧電素子の下面に形成された電極とで前記一対の電極とされ、前記電極検出部は、検査工程に投入された前記圧電素子の上面に位置する電極を、前記特定の電極として検出してもよい。 [13] Alternatively, the electrode formed on the upper surface of the piezoelectric element and the electrode formed on the lower surface of the piezoelectric element are used as the pair of electrodes, and the electrode detection unit is the piezoelectric element that has been put into an inspection process. An electrode located on the upper surface of the element may be detected as the specific electrode.

［１４］第３の本発明に係る圧電素子の製造方法は、圧電素子を作製する工程と、前記圧電素子を分極処理する工程と、分極処理された前記圧電素子の分極方向を判別する分極方向検査工程とを有する圧電素子の製造方法であって、前記分極方向検査工程は、前記圧電素子の電気的特性を少なくとも２条件で測定する測定ステップと、得られた少なくとも２つの測定値を比較して前記圧電素子の分極方向を判別する判別ステップとを有することを特徴とする。 [14] A method for manufacturing a piezoelectric element according to a third aspect of the present invention includes a step of manufacturing a piezoelectric element, a step of polarizing the piezoelectric element, and a polarization direction for determining a polarization direction of the piezoelectric element subjected to polarization processing. A method of manufacturing a piezoelectric element comprising: an inspection step, wherein the polarization direction inspection step compares a measurement step of measuring electrical characteristics of the piezoelectric element under at least two conditions and at least two obtained measurement values. And a discriminating step for discriminating the polarization direction of the piezoelectric element.

これにより、圧電効果（逆圧電効果）を有する素子、あるいは分極方向がそれぞれ同じ方向とされた圧電効果（逆圧電効果）を有する素子を製造することができ、分極方向が保証された圧電効果（逆圧電効果）を有する素子を市場に供給することができる。 As a result, an element having a piezoelectric effect (reverse piezoelectric effect) or an element having a piezoelectric effect (reverse piezoelectric effect) in which the polarization directions are the same can be manufactured. An element having a reverse piezoelectric effect) can be supplied to the market.

［１５］第３の本発明において、前記測定ステップは、前記圧電素子をバイアス電界０ｋＶ／ｍｍの状態で、前記圧電素子の静電容量を測定する第１ステップと、前記圧電素子にバイアス電界０．１〜１ｋＶ／ｍｍを印加した状態で、前記圧電素子の静電容量を測定する第２ステップと、を有し、前記判別ステップは、前記第１ステップで得られた第１測定値と、前記第２ステップで得られた第２測定値とを比較し、前記第１測定値に対する前記第２測定値の高低とバイアス電界方向とに基づいて、前記圧電素子の分極方向を判別してもよい。 [15] In the third aspect of the present invention, the measuring step includes a first step of measuring a capacitance of the piezoelectric element in a state where the piezoelectric element has a bias electric field of 0 kV / mm, and a bias electric field of 0 on the piezoelectric element. A second step of measuring the capacitance of the piezoelectric element in a state where a voltage of 1 to 1 kV / mm is applied, and the determination step includes a first measurement value obtained in the first step; The second measurement value obtained in the second step is compared, and the polarization direction of the piezoelectric element is determined based on the level of the second measurement value with respect to the first measurement value and the bias electric field direction. Good.

上述したように、本発明に係る分極方向検査方法及び分極方向検査装置によれば、精度向上のために破壊検査を行う必要がなく、圧電効果（逆圧電効果）を有する素子の分極方向を容易に判別することができ、全数保証を確保することができる。 As described above, according to the polarization direction inspection method and the polarization direction inspection apparatus according to the present invention, it is not necessary to perform a destructive inspection for improving accuracy, and the polarization direction of an element having a piezoelectric effect (reverse piezoelectric effect) can be easily performed. Therefore, it is possible to ensure the whole number guarantee.

また、本発明に係る圧電素子の製造方法によれば、圧電効果（逆圧電効果）を有する素子、あるいは分極方向がそれぞれ同じ方向とされた圧電効果（逆圧電効果）を有する素子を製造することができ、分極方向が保証された圧電効果（逆圧電効果）を有する素子を市場に供給することができる。 In addition, according to the method for manufacturing a piezoelectric element according to the present invention, an element having a piezoelectric effect (reverse piezoelectric effect) or an element having a piezoelectric effect (reverse piezoelectric effect) in which the polarization directions are the same direction is manufactured. Therefore, an element having a piezoelectric effect (inverse piezoelectric effect) with a guaranteed polarization direction can be supplied to the market.

図１Ａは円盤状の圧電素子を示す斜視図であり、図１Ｂは矩形状の圧電素子を示す斜視図であり、図１Ｃは、一方の電極に方向識別マークを形成した圧電素子を示す斜視図である。1A is a perspective view showing a disk-shaped piezoelectric element, FIG. 1B is a perspective view showing a rectangular piezoelectric element, and FIG. 1C is a perspective view showing a piezoelectric element in which a direction identification mark is formed on one electrode. It is. 図２Ａはセラミックス強誘電体で代表的な結晶構造であるペロブスカイト構造を有する結晶の単位格子（結晶格子）を模式的に示す斜視図であり、図２Ｂは図２Ａの結晶格子を正面からみた図である。2A is a perspective view schematically showing a unit cell (crystal lattice) of a crystal having a perovskite structure which is a typical crystal structure of a ceramic ferroelectric, and FIG. 2B is a view of the crystal lattice of FIG. 2A as viewed from the front. It is. 図３Ａは分極処理されていない圧電素子を示す模式図であり、図３Ｂは分極処理された圧電素子の分極方向を示す模式図であり、図３Ｃは分極方向と同方向にバイアス電界を印加した状態を示す模式図であり、図３Ｄは分極方向と逆方向にバイアス電界を印加した状態を示す模式図である。3A is a schematic diagram illustrating a piezoelectric element that has not been subjected to polarization treatment, FIG. 3B is a schematic diagram illustrating a polarization direction of the piezoelectric element that has been polarized, and FIG. 3C is a bias electric field applied in the same direction as the polarization direction. FIG. 3D is a schematic diagram illustrating a state in which a bias electric field is applied in a direction opposite to the polarization direction. 本実施の形態に係る分極方向検査方法を示すフローチャートである。It is a flowchart which shows the polarization direction inspection method which concerns on this Embodiment. 圧電素子に印加するバイアス電界に対する静電容量値の変化を示すグラフである。It is a graph which shows the change of the electrostatic capacitance value with respect to the bias electric field applied to a piezoelectric element. 本実施の形態に係る分極方向検査装置を示すブロック図である。It is a block diagram which shows the polarization direction inspection apparatus which concerns on this Embodiment. 分極方向検査装置の処理動作を示すフローチャートである。It is a flowchart which shows the processing operation of a polarization direction inspection apparatus. 分極方向検査装置の変形例を示すブロック図である。It is a block diagram which shows the modification of a polarization direction inspection apparatus. 図１Ａ及び図１Ｂに示す圧電素子の分極方向を判別する場合の使用例を示す説明図である。It is explanatory drawing which shows the usage example when discriminating the polarization direction of the piezoelectric element shown to FIG. 1A and FIG. 1B. 本実施の形態に係る圧電素子の製造方法を示すフローチャートである。It is a flowchart which shows the manufacturing method of the piezoelectric element which concerns on this Embodiment.

以下、本発明に係る分極方向検査方法、分極方向検査装置及び圧電素子の製造方法の実施の形態例を図１Ａ〜図１０を参照しながら説明する。なお、本明細書において数値範囲を示す「〜」は、その前後に記載される数値を下限値及び上限値として含む意味として使用される。 Hereinafter, embodiments of a polarization direction inspection method, a polarization direction inspection apparatus, and a piezoelectric element manufacturing method according to the present invention will be described with reference to FIGS. 1A to 10. In the present specification, “˜” indicating a numerical range is used as a meaning including numerical values described before and after the numerical value as a lower limit value and an upper limit value.

本実施の形態に係る分極方向検査方法は、分極処理された圧電素子の分極方向を判別する。 The polarization direction inspection method according to the present embodiment discriminates the polarization direction of the piezoelectric element subjected to polarization processing.

先ず、図１Ａ〜図１Ｃに示すように、圧電素子１０は、ペロブスカイト構造等から構成された素子本体１２と、素子本体１２の例えば上面及び下面に形成された一対の電極１４ａ及び１４ｂとを有する。形状としては、図１Ａに示す円盤形状や図１Ｂに示す矩形形状等が挙げられる。もちろん、図１Ｃに示すように、素子本体１２を積層構造にして、一対の電極１４ａ及び１４ｂをくし歯状に形成してもよい。この場合、素子本体１２の上面に一対の電極１４ａ及び１４ｂが現れるように形成し、そのうちの一方の電極１４ａに方向識別マーク１６を形成してもよい。 First, as shown in FIGS. 1A to 1C, the piezoelectric element 10 includes an element body 12 having a perovskite structure or the like, and a pair of electrodes 14 a and 14 b formed on, for example, the upper surface and the lower surface of the element body 12. . Examples of the shape include a disk shape shown in FIG. 1A and a rectangular shape shown in FIG. 1B. Of course, as shown in FIG. 1C, the element body 12 may have a laminated structure, and the pair of electrodes 14a and 14b may be formed in a comb shape. In this case, the pair of electrodes 14a and 14b may be formed on the upper surface of the element body 12, and the direction identification mark 16 may be formed on one of the electrodes 14a.

素子本体１２を構成するペロブスカイト構造は、一般に、ＡＢＸ₃という組成式で表され、ＢａＴｉＯ₃等の酸化物が挙げられる。 The perovskite structure constituting the element body 12 is generally represented by a composition formula of ABX ₃ , and examples thereof include oxides such as BaTiO ₃ .

ペロブスカイト構造を有する結晶の単位格子（以下、単に結晶格子１８という）は、図２Ａ及び図２Ｂに示すように、立方晶系の単位構造を持ち、８つの頂点にＡサイトの陽イオン（Ａサイトイオン１００と記す）が存在し、６つの面の中心にＸサイトの陰イオン（Ｘサイトイオン１０２と記す）が存在し、結晶格子１８のほぼ中心にＢサイトの陽イオン（Ｂサイトイオン１０４と記す）が存在する。Ａサイトイオン１００とＸサイトイオン１０２は同程度の大きさを有し、Ｂサイトイオン１０４はＡサイトイオン１００よりも小さなサイズを有する。ＢａＴｉＯ₃を例にすると、Ａサイトイオン１００がＢａ²⁺イオンであり、Ｘサイトイオン１０２がＯ^2-イオンであり、Ｂサイトイオン１０４がＴｉ⁴⁺イオンである。そして、Ｂサイトイオン１０４は、Ａサイトイオン１００よりもサイズが小さいため、温度や電界の影響を受けて、中心１０６からずれた位置に存在し得ることになる。そして、結晶格子１８のうち、Ｂサイトイオン１０４（陽イオン）が存在する側（図２Ｂでは上側）の電荷が“＋”リッチ側となり、反対側（図２Ｂでは下側）の電荷が“−”リッチ側となる。図２Ａに示すように、結晶格子１８の長軸方向がｃ軸、短軸方向がａ軸と称されている。以下の説明では、ｃ軸の長さとａ軸の長さの比をｃ／ａと記す。 As shown in FIGS. 2A and 2B, the unit cell of a crystal having a perovskite structure has a cubic unit structure, and has an A-site cation (A-site) at eight vertices. There are X-site anions (denoted as X-site ions 102) in the center of the six planes, and B-site cations (in the center of the crystal lattice 18 are denoted as B-site ions 104). There are). The A site ion 100 and the X site ion 102 have the same size, and the B site ion 104 has a smaller size than the A site ion 100. Taking BaTiO ₃ as an example, the A site ion 100 is a Ba ²⁺ ion, the X site ion 102 is an O ²⁻ ion, and the B site ion 104 is a Ti ⁴⁺ ion. Since the B site ion 104 is smaller in size than the A site ion 100, the B site ion 104 can be present at a position shifted from the center 106 due to the influence of temperature and electric field. In the crystal lattice 18, the charge on the side where the B site ions 104 (positive ions) are present (upper side in FIG. 2B) is “+” rich side, and the charge on the opposite side (lower side in FIG. 2B) is “−”. “Become rich. As shown in FIG. 2A, the major axis direction of the crystal lattice 18 is referred to as the c axis, and the minor axis direction is referred to as the a axis. In the following description, the ratio of the c-axis length to the a-axis length is denoted as c / a.

ここで、本実施の形態に係る分極方向検査方法について図３Ａ〜図５を参照しながら説明する。なお、図３Ａ〜図３Ｄにおいて、結晶格子１８中の「＋」は“＋”リッチ側を示し、「−」は“−”リッチ側を示す。 Here, the polarization direction inspection method according to the present embodiment will be described with reference to FIGS. 3A to 5. 3A to 3D, “+” in the crystal lattice 18 indicates the “+” rich side, and “−” indicates the “−” rich side.

先ず、図３Ａに模式的に示すように、分極処理されていない圧電素子１０は、各結晶格子１８の例えば“＋”リッチ側の向きがばらばらとなっている。この状態から、図３Ｂに示すように、圧電素子１０の例えば一方の電極１４ａに正電位、他方の電極１４ｂに負電位を印加して圧電素子１０を分極処理すると、各結晶格子１８は一方の電極１４ａ側に“−”リッチ側が揃い、他方の電極１４ｂ側に “＋”リッチ側が揃うこととなる。このときの分極方向は他方の電極１４ｂから一方の電極１４ａに向かう方向である。 First, as schematically shown in FIG. 3A, the piezoelectric elements 10 that have not been subjected to the polarization treatment have different orientations on the “+” rich side of each crystal lattice 18, for example. From this state, as shown in FIG. 3B, when the piezoelectric element 10 is polarized by applying a positive potential to the one electrode 14a and a negative potential to the other electrode 14b of the piezoelectric element 10, for example, The “−” rich side is aligned on the electrode 14a side, and the “+” rich side is aligned on the other electrode 14b side. The polarization direction at this time is a direction from the other electrode 14b toward the one electrode 14a.

そして、図４のステップＳ１において、圧電素子１０にバイアス電界Ｅｂを印加しない状態で、圧電素子１０の静電容量を測定して静電容量値Ｃ１を得る。つまり、分極処理した状態での圧電素子１０の静電容量が測定される。この測定では、圧電素子１０を分極処理した後に、圧電素子１０が設計どおり分極処理されたかどうかを判定するための静電容量測定装置を使用（兼用）して行うようにしてもよい。 Then, in step S1 of FIG. 4, the capacitance of the piezoelectric element 10 is measured to obtain a capacitance value C1 without applying the bias electric field Eb to the piezoelectric element 10. That is, the capacitance of the piezoelectric element 10 in a state where the polarization treatment is performed is measured. In this measurement, after the piezoelectric element 10 is polarized, a capacitance measuring device for determining whether the piezoelectric element 10 is polarized as designed may be used (also used).

その後、ステップＳ２において、圧電素子１０にバイアス電界Ｅｂを印加した状態で、圧電素子１０の静電容量を測定して静電容量値Ｃ２を得る。このとき、図３Ｃに示すように、一方の電極１４ａに正電位が印加され、他方の電極１４ｂに負電位が印加されることになる。つまり、方向が分極方向と同じ方向（上向き）のバイアス電界Ｅｂが印加される。この場合、結晶格子１８中のＢサイトイオン１０４が、結晶格子１８の中心１０６からさらに離れる方向に、バイアス電界Ｅｂの強さに応じた分だけ歪む（逆圧電効果）ことから、結晶格子１８内の格子間距離が変化し、ｃ／ａが大きくなって、見かけ上、誘電率が下がり、静電容量値が低くなると考えられる。結果的にステップＳ１で得られた静電容量値Ｃ１よりも低い静電容量値Ｃ２を得る。このステップＳ２において、圧電素子１０に印加するバイアス電界Ｅｂは、圧電素子１０の分極状態に影響を与えない程度のバイアス電界Ｅｂを印加することが好ましい。従って、バイアス電界Ｅｂとしては、圧電素子１０の抗電界の８０％以下であることが好ましく、例えば０．１〜１ｋＶ／ｍｍが挙げられる。 Thereafter, in step S2, with the bias electric field Eb applied to the piezoelectric element 10, the capacitance of the piezoelectric element 10 is measured to obtain a capacitance value C2. At this time, as shown in FIG. 3C, a positive potential is applied to one electrode 14a, and a negative potential is applied to the other electrode 14b. That is, the bias electric field Eb whose direction is the same as the polarization direction (upward) is applied. In this case, the B site ions 104 in the crystal lattice 18 are distorted in a direction further away from the center 106 of the crystal lattice 18 by an amount corresponding to the intensity of the bias electric field Eb (reverse piezoelectric effect). It is considered that the interstitial distance of the layer changes, c / a increases, the apparent dielectric constant decreases, and the capacitance value decreases. As a result, a capacitance value C2 lower than the capacitance value C1 obtained in step S1 is obtained. In step S 2, it is preferable that the bias electric field Eb applied to the piezoelectric element 10 is a bias electric field Eb that does not affect the polarization state of the piezoelectric element 10. Therefore, the bias electric field Eb is preferably 80% or less of the coercive electric field of the piezoelectric element 10, and may be 0.1 to 1 kV / mm, for example.

その後、図４のステップＳ３において、ステップＳ１で得られた静電容量値Ｃ１と、ステップＳ２で得られた静電容量値Ｃ２とを比較し、静電容量値Ｃ１に対する静電容量値Ｃ２の高低とバイアス電界方向とに基づいて、圧電素子１０の分極方向を判別する。この例では、静電容量値Ｃ２が静電容量値Ｃ１よりも低いことから、分極方向が電界の方向と同じ上向きであるとして判別される。 Thereafter, in step S3 of FIG. 4, the capacitance value C1 obtained in step S1 is compared with the capacitance value C2 obtained in step S2, and the capacitance value C2 relative to the capacitance value C1 is compared. The polarization direction of the piezoelectric element 10 is determined based on the height and the bias electric field direction. In this example, since the electrostatic capacitance value C2 is lower than the electrostatic capacitance value C1, it is determined that the polarization direction is the same upward as the electric field direction.

上述したステップＳ２において、図３Ｄに示すように、一方の電極１４ａに負電位を印加し、他方の電極１４ｂに正電位を印加した場合、つまり、方向が分極方向と反対方向（下向き）のバイアス電界Ｅｂを印加した場合は、結晶格子１８中のＢサイトイオン１０４が、結晶格子１８の中心１０６に向かってバイアス電界Ｅｂの強さに応じた分だけ歪む（逆圧電効果）ことから、結晶格子１８内の格子間距離が変化し、ｃ／ａが小さくなって、見かけ上、誘電率が大きくなり、静電容量値が高くなると考えられる。結果的にステップＳ１で得られた静電容量値Ｃ１よりも高い静電容量値Ｃ２を得る。 In step S2 described above, as shown in FIG. 3D, when a negative potential is applied to one electrode 14a and a positive potential is applied to the other electrode 14b, that is, a bias whose direction is opposite to the polarization direction (downward). When the electric field Eb is applied, the B site ions 104 in the crystal lattice 18 are distorted by the amount corresponding to the strength of the bias electric field Eb toward the center 106 of the crystal lattice 18 (reverse piezoelectric effect). It is considered that the interstitial distance in 18 changes, c / a decreases, the dielectric constant increases, and the capacitance value increases. As a result, a capacitance value C2 higher than the capacitance value C1 obtained in step S1 is obtained.

従って、次のステップＳ３では、静電容量値Ｃ２が静電容量値Ｃ１よりも高いことから、分極方向が電界の方向とは反対方向の下向きであるとして判別される。 Therefore, in the next step S3, since the capacitance value C2 is higher than the capacitance value C1, it is determined that the polarization direction is downward in the direction opposite to the direction of the electric field.

このように、本実施の形態に係る分極方向検査方法においては、精度向上のために破壊検査を行う必要がなく、分極処理された圧電素子１０の分極方向を容易に判別することができ、全数保証を確保することができる。 As described above, in the polarization direction inspection method according to the present embodiment, it is not necessary to perform a destructive inspection to improve accuracy, and the polarization direction of the piezoelectric element 10 subjected to the polarization treatment can be easily determined. Guarantee can be secured.

実質的にバイアス電界Ｅｂを１回だけ印加した静電容量測定を追加するだけであるため、短時間で判定することができる。しかも、バイアス電界Ｅｂは、圧電素子１０の抗電界の８０％以下であるため、圧電素子１０の分極状態に影響を与えることがなく、バイアス電界Ｅｂの印加を止めた段階で、分極処理された時点の分極状態に戻る。また、ステップＳ１を行った後にステップＳ２を行うようにしたので、ステップＳ１において、圧電素子１０が設計どおり分極処理されたかどうかを判定する際に、同時に静電容量値Ｃ１を確認することができ、工程の簡略化を図ることができる。 Since the capacitance measurement in which the bias electric field Eb is applied only once is substantially added, the determination can be made in a short time. In addition, since the bias electric field Eb is 80% or less of the coercive electric field of the piezoelectric element 10, the polarization process is not performed on the polarization state of the piezoelectric element 10, and the polarization process is performed when the application of the bias electric field Eb is stopped. Return to the current polarization state. Since step S2 is performed after performing step S1, the capacitance value C1 can be confirmed at the same time when determining whether or not the piezoelectric element 10 has been polarized as designed in step S1. The process can be simplified.

さらに、少なくともステップＳ１及びステップＳ２において、１０℃以上の温度変化がない環境で行うことで、正確に分極方向を判別することができ、好ましい。 Furthermore, it is preferable that at least step S1 and step S2 be performed in an environment in which there is no temperature change of 10 ° C. or more, the polarization direction can be accurately determined.

［実験例］
ここで、１つの実験例を示す。この実験例では、圧電素子１０として、図１Ｃに示す圧電素子１０を用い、この圧電素子１０に対して分極方向が他方の電極１４ｂから一方の電極１４ａに向かう方向の分極処理を行った。その後、分極方向検査装置２０を使用して、バイアス電界Ｅｂを以下の［１］、［２］及び［３］の順番で印加したときの静電容量の変化（静電容量値の変化量）を確認した。静電容量の測定結果を図５に示す。
［１］：０．０ｋＶ／ｍｍ→０．１ｋＶ／ｍｍ→０．２ｋＶ／ｍｍ→０．３ｋＶ／ｍｍ
［２］：０．３ｋＶ／ｍｍ→０．２ｋＶ／ｍｍ→０．１ｋＶ／ｍｍ→０．０ｋＶ／ｍｍ→−０．１ｋＶ／ｍｍ→−０．２ｋＶ／ｍｍ→−０．３ｋＶ／ｍｍ
［３］：−０．３ｋＶ／ｍｍ→−０．２ｋＶ／ｍｍ→−０．１ｋＶ／ｍｍ→０．０ｋＶ／ｍｍ [Experimental example]
Here, one experimental example is shown. In this experimental example, the piezoelectric element 10 shown in FIG. 1C was used as the piezoelectric element 10, and the piezoelectric element 10 was subjected to a polarization process in which the polarization direction was from the other electrode 14b toward the one electrode 14a. Thereafter, using the polarization direction inspection device 20, a change in capacitance when the bias electric field Eb is applied in the following order [1], [2] and [3] (amount of change in capacitance value) It was confirmed. The measurement results of the capacitance are shown in FIG.
[1]: 0.0 kV / mm → 0.1 kV / mm → 0.2 kV / mm → 0.3 kV / mm
[2]: 0.3 kV / mm → 0.2 kV / mm → 0.1 kV / mm → 0.0 kV / mm → −0.1 kV / mm → −0.2 kV / mm → −0.3 kV / mm
[3]: −0.3 kV / mm → −0.2 kV / mm → −0.1 kV / mm → 0.0 kV / mm

図５から、バイアス電界Ｅｂがプラスの領域の静電容量値Ｃ２は、バイアス電界Ｅｂが０．０ｋＶ／ｍｍでの静電容量値Ｃ１よりも低く、バイアス電界Ｅｂがマイナスの領域の静電容量値Ｃ２は、バイアス電界Ｅｂが０．０ｋＶ／ｍｍでの静電容量値Ｃ１よりも高くなっている。図５の例では、−０．３ｋＶ／ｍｍ〜＋０．３ｋＶ／ｍｍの範囲で、Ｃ２＝（１００％＋４％〜１００％−４％）×Ｃ１が成り立ち、分極方向の判別が可能である。 From FIG. 5, the electrostatic capacitance value C2 in the region where the bias electric field Eb is positive is lower than the electrostatic capacitance value C1 when the bias electric field Eb is 0.0 kV / mm, and the electrostatic capacitance value in the region where the bias electric field Eb is negative. The value C2 is higher than the capacitance value C1 when the bias electric field Eb is 0.0 kV / mm. In the example of FIG. 5, C2 = (100% + 4% to 100% -4%) × C1 holds in the range of −0.3 kV / mm to +0.3 kV / mm, and the polarization direction can be determined.

このように、バイアス電界Ｅｂを印加しない状態（バイアス電界Ｅｂ＝０．０ｋＶ／ｍｍ）での圧電素子１０の静電容量値Ｃ１と、圧電素子１０にバイアス電界Ｅｂを印加した状態での圧電素子１０の静電容量値Ｃ２との高低を比較することで、容易に分極方向を測定することができることがわかる。 Thus, the electrostatic capacitance value C1 of the piezoelectric element 10 without applying the bias electric field Eb (bias electric field Eb = 0.0 kV / mm) and the piezoelectric element with the bias electric field Eb applied to the piezoelectric element 10 It can be seen that the polarization direction can be easily measured by comparing the level with the capacitance value C2 of 10.

次に、上述した本実施の形態に係る分極方向検査方法を実現する分極方向検査装置２０について図６を参照しながら説明する。なお、圧電素子１０として、例えば図１Ｃに示すように、素子本体１２の上面に一対の電極（一方の電極１４ａ及び他方の電極１４ｂ）が現れるように形成され、そのうちの一方の電極１４ａに方向識別マーク１６が形成された圧電素子１０を使用する場合を想定する。また、圧電素子１０に対する分極処理において、正常な分極処理であれば、分極方向が他方の電極１４ｂから一方の電極１４ａに向かう方向としている。 Next, a polarization direction inspection apparatus 20 that realizes the polarization direction inspection method according to the present embodiment described above will be described with reference to FIG. As shown in FIG. 1C, for example, the piezoelectric element 10 is formed so that a pair of electrodes (one electrode 14a and the other electrode 14b) appear on the upper surface of the element body 12, and the direction is directed to one of the electrodes 14a. Assume that the piezoelectric element 10 on which the identification mark 16 is formed is used. In the polarization process for the piezoelectric element 10, if the polarization process is normal, the polarization direction is the direction from the other electrode 14b to the one electrode 14a.

先ず、分極方向検査装置２０は、図６に示すように、図示しない検査台あるいはトレイに載置された圧電素子１０を撮像するカメラ２２と、圧電素子１０の静電容量を測定する静電容量測定装置２４（ＬＣＲメータ）と、圧電素子１０に対してバイアス電界Ｅｂを印加するＤＣ電源２６と、少なくともカメラ２２、静電容量測定装置２４及びＤＣ電源２６を制御する制御部２８とを有する。 First, as shown in FIG. 6, the polarization direction inspection device 20 includes a camera 22 that images the piezoelectric element 10 placed on an inspection table or tray (not shown), and an electrostatic capacity that measures the electrostatic capacity of the piezoelectric element 10. It has a measuring device 24 (LCR meter), a DC power source 26 that applies a bias electric field Eb to the piezoelectric element 10, and a controller 28 that controls at least the camera 22, the capacitance measuring device 24, and the DC power source 26.

制御部２８は、圧電素子１０の一対の電極１４ａ及び１４ｂのうち、特定の電極を検出する電極検出部３０と、圧電素子１０の電気的特性を少なくとも２条件で測定する測定部３２と、得られた少なくとも２つの測定値を比較して圧電素子１０の分極方向を判別する判別部３４とを有する。 The control unit 28 includes an electrode detection unit 30 that detects a specific electrode of the pair of electrodes 14a and 14b of the piezoelectric element 10, a measurement unit 32 that measures the electrical characteristics of the piezoelectric element 10 under at least two conditions, and And a discriminator 34 that discriminates the polarization direction of the piezoelectric element 10 by comparing at least two measured values.

電極検出部３０は、方向識別マーク１６（図１Ｃ参照）を画像認識し、認識した方向識別マーク１６に対応した電極（この例では、一方の電極１４ａ）を特定の電極として検出する。 The electrode detection unit 30 recognizes an image of the direction identification mark 16 (see FIG. 1C), and detects an electrode (in this example, one electrode 14a) corresponding to the recognized direction identification mark 16 as a specific electrode.

測定部３２は、圧電素子１０をバイアス電界Ｅｂ＝０ｋＶ／ｍｍの状態、すなわち、バイアス電界Ｅｂを印加しない状態で、圧電素子１０の静電容量を測定する第１静電容量測定部３６Ａと、圧電素子１０にバイアス電界Ｅｂ＝０．１〜１ｋＶ／ｍｍを印加した状態で、圧電素子１０の静電容量を測定する第２静電容量測定部３６Ｂと、第１静電容量測定部３６Ａ及び第２静電容量測定部３６Ｂでの測定値を一時的に記憶するメモリ３８とを有する。 The measurement unit 32 includes a first capacitance measurement unit 36A that measures the capacitance of the piezoelectric element 10 while the piezoelectric element 10 is in a bias electric field Eb = 0 kV / mm, that is, in a state where no bias electric field Eb is applied. In a state where a bias electric field Eb = 0.1 to 1 kV / mm is applied to the piezoelectric element 10, a second capacitance measuring unit 36B that measures the capacitance of the piezoelectric element 10, a first capacitance measuring unit 36A, And a memory 38 that temporarily stores measurement values obtained by the second capacitance measuring unit 36B.

判別部３４は、第１静電容量測定部３６Ａにて得られた静電容量値Ｃ１と、第２静電容量測定部３６Ｂで得られた静電容量値Ｃ２とを比較し、静電容量値Ｃ１に対する静電容量値Ｃ２の高低とバイアス電界方向とに基づいて、圧電素子１０の分極方向を判別する。 The determination unit 34 compares the capacitance value C1 obtained by the first capacitance measurement unit 36A with the capacitance value C2 obtained by the second capacitance measurement unit 36B, and determines the capacitance. The polarization direction of the piezoelectric element 10 is determined based on the level of the capacitance value C2 with respect to the value C1 and the bias electric field direction.

ここで、分極方向検査装置２０での処理動作を図７のフローチャートを参照しながら説明する。 Here, the processing operation in the polarization direction inspection apparatus 20 will be described with reference to the flowchart of FIG.

先ず、図７のステップＳ１０１において、電極検出部３０は、カメラ２２を駆動制御して、図示しない検査台あるいはトレイに載置された圧電素子１０を撮像し、方向識別マーク１６（図１Ｃ参照）の位置を画像認識する。電極検出部３０は、画像認識した方向識別マーク１６に対応した電極（一方の電極１４ａ）を特定の電極として検出する。画像認識は、オペレータが表示装置の画面に表示される画像を見ながら、カメラ２２を操作して方向識別マーク１６の位置を検出（手動）してもよいし、撮像画像のうち、方向識別マーク１６の画像と一致する画像をパターンマッチングを用いて自動的に検出してもよい。 First, in step S101 of FIG. 7, the electrode detection unit 30 drives and controls the camera 22, images the piezoelectric element 10 placed on an inspection table or tray (not shown), and the direction identification mark 16 (see FIG. 1C). Recognize the position of the image. The electrode detection unit 30 detects an electrode (one electrode 14a) corresponding to the direction identification mark 16 whose image has been recognized as a specific electrode. In the image recognition, the operator may detect (manually) the position of the direction identification mark 16 by operating the camera 22 while viewing the image displayed on the screen of the display device. Images that match the 16 images may be automatically detected using pattern matching.

ステップＳ１０２において、第１静電容量測定部３６Ａは、圧電素子１０にバイアス電界Ｅｂを印加していない状態で、圧電素子１０の静電容量を測定する。具体的には、第１静電容量測定部３６Ａは、静電容量測定装置２４を制御して、一対のプローブピン４０ａ及び４０ｂ（図６参照）を、圧電素子１０の一対の電極１４ａ及び１４ｂに接触させて、圧電素子１０の静電容量を測定する。第１静電容量測定部３６Ａは、このときの静電容量値を静電容量値Ｃ１としてメモリ３８に記憶する。 In step S 102, the first capacitance measuring unit 36 A measures the capacitance of the piezoelectric element 10 without applying the bias electric field Eb to the piezoelectric element 10. Specifically, the first capacitance measuring unit 36A controls the capacitance measuring device 24 to replace the pair of probe pins 40a and 40b (see FIG. 6) with the pair of electrodes 14a and 14b of the piezoelectric element 10. And the capacitance of the piezoelectric element 10 is measured. The first capacitance measuring unit 36A stores the capacitance value at this time in the memory 38 as the capacitance value C1.

ステップＳ１０３において、第２静電容量測定部３６Ｂは、圧電素子１０にバイアス電界Ｅｂを印加した状態で、圧電素子１０の静電容量を測定する。具体的には、第２静電容量測定部３６Ｂは、ＤＣ電源２６を駆動制御して、圧電素子１０の一対の電極１４ａ及び１４ｂ間にバイアス電界Ｅｂを印加する。このとき、例えば方向識別マーク１６に対応する一方の電極１４ａが正電位、他方の電極１４ｂが負電位となるように印加する。そして、第２静電容量測定部３６Ｂは、圧電素子１０にバイアス電界Ｅｂが印加されている状態で、ステップＳ１０２と同様にして、静電容量測定装置２４を使用して圧電素子１０の静電容量を測定し、このときの静電容量値を静電容量値Ｃ２としてメモリ３８に記憶する。 In step S 103, the second capacitance measuring unit 36 B measures the capacitance of the piezoelectric element 10 with the bias electric field Eb applied to the piezoelectric element 10. Specifically, the second capacitance measuring unit 36 B drives and controls the DC power supply 26 and applies a bias electric field Eb between the pair of electrodes 14 a and 14 b of the piezoelectric element 10. At this time, for example, application is performed so that one electrode 14a corresponding to the direction identification mark 16 has a positive potential and the other electrode 14b has a negative potential. Then, the second capacitance measuring unit 36B uses the capacitance measuring device 24 in the state where the bias electric field Eb is applied to the piezoelectric element 10 and uses the capacitance measuring device 24 to detect the electrostatic capacitance of the piezoelectric element 10. The capacitance is measured, and the capacitance value at this time is stored in the memory 38 as the capacitance value C2.

ステップＳ１０４において、判別部３４は、メモリ３８から静電容量値Ｃ１及び静電容量値Ｃ２を読み出して、これら静電容量値Ｃ１と静電容量値Ｃ２とを比較し、静電容量値Ｃ１に対する静電容量値Ｃ２の高低とバイアス電界方向とに基づいて、圧電素子１０の分極方向を判別する。判別部３４は、上述したように、静電容量値Ｃ２が静電容量値Ｃ１よりも低ければ、分極方向が他方の電極１４ｂから一方の電極１４ａに向かう方向として判別し、正常に分極処理がされているものと判定する。 In step S104, the determination unit 34 reads the capacitance value C1 and the capacitance value C2 from the memory 38, compares the capacitance value C1 and the capacitance value C2, and compares the capacitance value C1 with the capacitance value C1. The polarization direction of the piezoelectric element 10 is determined based on the level of the capacitance value C2 and the bias electric field direction. As described above, when the capacitance value C2 is lower than the capacitance value C1, the determination unit 34 determines that the polarization direction is the direction from the other electrode 14b toward the one electrode 14a, and the polarization process is normally performed. It is determined that

上述した分極方向検査装置２０では、静電容量測定装置２４及びＤＣ電源２６を用いた例を示したが、その他、図８の変形例に係る分極方向検査装置２０ａに示すように、静電容量測定装置２４及びＤＣ電源２６に代えて、バイアス電界印加手段と静電容量測定手段とを兼ね備えたインピーダンスアナライザ４２を用いてもよい。この場合、分極方向検査装置２０の装置構成の簡単化と静電容量以外の電気特性、例えば共振周波数での判別もできる。 In the polarization direction inspection device 20 described above, an example using the capacitance measuring device 24 and the DC power source 26 has been shown. However, as shown in the polarization direction inspection device 20a according to the modified example of FIG. Instead of the measuring device 24 and the DC power source 26, an impedance analyzer 42 having both a bias electric field applying unit and a capacitance measuring unit may be used. In this case, the device configuration of the polarization direction inspection device 20 can be simplified, and electrical characteristics other than capacitance, for example, discrimination based on resonance frequency can be performed.

また、圧電素子１０として、図１Ａ及び図１Ｂに示す圧電素子１０を使用する場合は、電極検出部３０は、検査工程に投入された圧電素子１０の上面に位置する一方の電極１４ａを、特定の電極として検出してもよい。この場合、図９に示すように、上面に共通電極４４が形成された基台４６を使用することが好ましい。すなわち、圧電素子１０の検査工程への投入の際に、基台４６の共通電極４４上に、圧電素子１０を載置して、圧電素子１０の他方の電極１４ｂと共通電極４４とを接触させ、共通電極４４からＤＣ電源２６の例えばマイナス側端子とを配線接続する。また、圧電素子１０の静電容量を測定するときは、静電容量測定装置２４の一方のプローブピン４０ａを圧電素子１０の一方の電極１４ａに接触させ、他方のプローブピン４０ｂを共通電極４４に接触させればよい。 In addition, when the piezoelectric element 10 shown in FIGS. 1A and 1B is used as the piezoelectric element 10, the electrode detection unit 30 specifies one electrode 14a located on the upper surface of the piezoelectric element 10 put into the inspection process. It may be detected as an electrode. In this case, as shown in FIG. 9, it is preferable to use a base 46 having a common electrode 44 formed on the upper surface. That is, when the piezoelectric element 10 is put into the inspection process, the piezoelectric element 10 is placed on the common electrode 44 of the base 46 and the other electrode 14b of the piezoelectric element 10 and the common electrode 44 are brought into contact with each other. The common electrode 44 is connected to the negative terminal of the DC power source 26 by wiring. When measuring the capacitance of the piezoelectric element 10, one probe pin 40 a of the capacitance measuring device 24 is brought into contact with one electrode 14 a of the piezoelectric element 10, and the other probe pin 40 b is connected to the common electrode 44. What is necessary is just to contact.

次に、本実施の形態に係る圧電素子の製造方法について図１０を参照しながら説明する。 Next, a method for manufacturing a piezoelectric element according to the present embodiment will be described with reference to FIG.

先ず、図１０のステップＳ２０１において、素子本体１２に一対の電極１４ａ及び１４ｂを形成して圧電素子１０を作製する。その後、ステップＳ２０２において、一対の電極１４ａ及び１４ｂのうち、例えば一方の電極１４ａに例えばレーザ等を用いて孔を形成して方向識別マーク１６としても良く、上述の一対の電極１４ａ及び１４ｂを形成する際に、スクリーン印刷法を用いる等して、方向識別マーク１６を予め形成しても良い。このステップＳ２０２は、圧電素子１０が図１Ａや図１Ｂのタイプであれば、省略してもよい。 First, in step S 201 of FIG. 10, the pair of electrodes 14 a and 14 b are formed on the element body 12 to manufacture the piezoelectric element 10. Thereafter, in step S202, of the pair of electrodes 14a and 14b, for example, a hole may be formed in one electrode 14a using, for example, a laser to form the direction identification mark 16, and the above-described pair of electrodes 14a and 14b is formed. In this case, the direction identification mark 16 may be formed in advance by using a screen printing method or the like. This step S202 may be omitted if the piezoelectric element 10 is of the type shown in FIGS. 1A and 1B.

ステップＳ２０３において、圧電素子１０を分極処理する。この場合、正常な分極処理の分極方向を例えば他方の電極１４ｂから一方の電極１４ａに向かう方向とする。そして、ステップ２０４において、上述した本実施の形態に係る分極方向検査方法を用いて分極処理済みの圧電素子１０の分極方向を判別する。 In step S203, the piezoelectric element 10 is polarized. In this case, the polarization direction of normal polarization processing is, for example, the direction from the other electrode 14b toward the one electrode 14a. In step 204, the polarization direction of the piezoelectric element 10 that has been subjected to polarization processing is determined using the polarization direction inspection method according to the present embodiment described above.

その後、ステップＳ２０５において、分極方向が正常な圧電素子と正常でない圧電素子を振り分ける。正常でない圧電素子は、ステップＳ２０６において、不良品として一旦回収される。そして、不良品として回収された圧電素子を、再度ステップＳ２０３において正しい方向で再分極処理した後、ステップＳ２０４以降の処理を繰り返す。 Thereafter, in step S205, the piezoelectric elements having normal polarization directions and the non-normal piezoelectric elements are sorted. The abnormal piezoelectric element is once recovered as a defective product in step S206. Then, after the piezoelectric element recovered as a defective product is repolarized in the correct direction again in step S203, the processes in and after step S204 are repeated.

このように、本実施の形態に係る圧電素子の製造方法においては、分極方向が判明した圧電素子１０、あるいは分極方向がそれぞれ同じ方向とされた圧電素子１０を製造することができ、分極方向が保証された圧電素子１０を市場に供給することができる。しかも、一旦、ＮＧとされた圧電素子１０に対して再度分極処理を行った後、分極方向検査を行うようにしたので、歩留まりの向上も図ることができ、圧電素子１０の生産性を上げることができる。 As described above, in the piezoelectric element manufacturing method according to the present embodiment, the piezoelectric element 10 whose polarization direction is known, or the piezoelectric element 10 having the same polarization direction can be manufactured. A guaranteed piezoelectric element 10 can be supplied to the market. Moreover, since the polarization direction is inspected after the NG piezoelectric element 10 is once again subjected to the polarization treatment, the yield can be improved and the productivity of the piezoelectric element 10 is increased. Can do.

上述の例では、主に圧電素子１０の静電容量を２条件で測定し、得られた２つの測定値を比較して圧電素子１０の分極方向を判別したが、その他、圧電素子１０に限らず、素子の共振周波数を２条件で測定し、得られた２つの測定値を比較して素子の分極方向を判別してもよい。 In the above example, the capacitance of the piezoelectric element 10 is mainly measured under two conditions, and the two measured values obtained are compared to determine the polarization direction of the piezoelectric element 10. Alternatively, the resonance frequency of the element may be measured under two conditions, and the two measured values obtained may be compared to determine the polarization direction of the element.

なお、本発明に係る分極方向検査方法、分極方向検査装置及び圧電素子の製造方法は、上述の実施の形態に限らず、本発明の要旨を逸脱することなく、種々の構成を採り得ることはもちろんである。 The polarization direction inspection method, the polarization direction inspection apparatus, and the piezoelectric element manufacturing method according to the present invention are not limited to the above-described embodiments, and various configurations can be adopted without departing from the gist of the present invention. Of course.

１０…圧電素子１２…素子本体
１４ａ、１４ｂ…一対の電極１４ａ…一方の電極
１４ｂ…他方の電極１６…方向識別マーク
１８…単位格子２０…分極方向検査装置
２２…カメラ２４…静電容量測定装置
２６…ＤＣ電源２８…制御部
３０…電極検出部３２…測定部
３４…判別部３６Ａ…第１静電容量測定部
３６Ｂ…第２静電容量測定部４２…インピーダンスアナライザ
Ｃ１、Ｃ２…静電容量値Ｅｂ…バイアス電界 DESCRIPTION OF SYMBOLS 10 ... Piezoelectric element 12 ... Element main body 14a, 14b ... A pair of electrode 14a ... One electrode 14b ... The other electrode 16 ... Direction identification mark 18 ... Unit lattice 20 ... Polarization direction inspection apparatus 22 ... Camera 24 ... Capacitance measuring apparatus DESCRIPTION OF SYMBOLS 26 ... DC power supply 28 ... Control part 30 ... Electrode detection part 32 ... Measurement part 34 ... Discrimination part 36A ... 1st electrostatic capacitance measurement part 36B ... 2nd electrostatic capacitance measurement part 42 ... Impedance analyzer C1, C2 ... Electrostatic capacity Value Eb: Bias electric field

Claims

A polarization direction inspection method for determining the polarization direction of an element,
A measuring step for measuring the electrical characteristics of the element under at least two conditions;
Obtained by comparing at least two measured values have a a determination step of determining the polarization direction of the element,
The element is a polarized piezoelectric element;
The measuring step includes
A first step of measuring the capacitance of the piezoelectric element in a state where the piezoelectric element has a bias electric field of 0 kV / mm;
A second step of measuring a capacitance of the piezoelectric element in a state where a bias electric field of 0.1 to 1 kV / mm is applied to the piezoelectric element;
The determination step includes
The first measurement value obtained in the first step is compared with the second measurement value obtained in the second step, and the level of the second measurement value with respect to the first measurement value and the bias electric field direction are compared. A polarization direction inspection method , comprising: discriminating a polarization direction of the piezoelectric element on the basis of the polarization direction .

In the polarization direction inspection method according to claim 1 ,
The polarization direction inspection method, wherein the bias electric field applied to the piezoelectric element in the second step is 80% or less of a coercive electric field of the piezoelectric element.

In the polarization direction inspection method according to claim 1 or 2 ,
The measuring step includes performing the second step after performing the first step.

In the polarization direction inspection method according to any one of claims 1 to 3 ,
The polarization direction inspection method, wherein the measuring step is performed by using a capacitance measuring device for determining whether or not the piezoelectric element is polarized after the piezoelectric element is polarized.

In the polarization direction inspection method according to any one of claims 1 to 4 ,
At least the measurement step is performed in an environment where there is no temperature change of 10 ° C. or more.

A polarization direction inspection device for determining a polarization direction of a piezoelectric element subjected to polarization treatment,
A measurement unit for measuring electrical characteristics of the piezoelectric element under at least two conditions;
A discriminator for discriminating the polarization direction of the piezoelectric element by comparing at least two obtained measurement values ;
Capacitance measuring means;
Electric field applying means,
The measuring unit is
A first capacitance measuring unit that controls the capacitance measuring means and the electric field applying means, and measures the capacitance of the piezoelectric element in a state where the piezoelectric element has a bias electric field of 0 kV / mm;
A second capacitance that controls the capacitance measuring means and the electric field applying means to measure the capacitance of the piezoelectric element in a state where a bias electric field of 0.1 to 1 kV / mm is applied to the piezoelectric element. A measurement unit,
The discrimination unit
The first measurement value obtained by the first capacitance measurement unit is compared with the second measurement value obtained by the second capacitance measurement unit, and the second measurement with respect to the first measurement value is performed. A polarization direction inspection apparatus characterized by discriminating a polarization direction of the piezoelectric element based on a value level and a bias electric field direction .

The polarization direction inspection apparatus according to claim 6 , wherein
Furthermore, it has an electrode detection unit for detecting a specific electrode among the pair of electrodes of the piezoelectric element,
The polarization direction inspection apparatus, wherein the second capacitance measuring unit applies the bias electric field in a fixed direction between the pair of electrodes with the specific electrode as a reference.

In the polarization direction inspection device according to claim 7 ,
One of the pair of electrodes is provided with a direction identification mark,
The polarization detecting device, wherein the electrode detection unit recognizes an image of the direction identification mark and detects an electrode corresponding to the recognized direction identification mark as the specific electrode.

In the polarization direction inspection device according to claim 7 ,
The electrode formed on the upper surface of the piezoelectric element and the electrode formed on the lower surface of the piezoelectric element constitute the pair of electrodes,
The polarization direction inspection apparatus, wherein the electrode detection unit detects an electrode located on an upper surface of the piezoelectric element input in an inspection process as the specific electrode.

Producing a piezoelectric element;
A step of polarizing the piezoelectric element;
A method of manufacturing a piezoelectric element having a polarization direction inspection step of determining a polarization direction of the piezoelectric element subjected to polarization treatment,
The polarization direction inspection step includes
A measurement step of measuring electrical characteristics of the piezoelectric element under at least two conditions;
Obtained by comparing at least two measured values have a a determination step of determining the direction of polarization of the piezoelectric element,
The measuring step includes
A first step of measuring the capacitance of the piezoelectric element in a state where the piezoelectric element has a bias electric field of 0 kV / mm;
A second step of measuring a capacitance of the piezoelectric element in a state where a bias electric field of 0.1 to 1 kV / mm is applied to the piezoelectric element;
The determination step compares the first measurement value obtained in the first step with the second measurement value obtained in the second step, and determines whether the second measurement value is higher or lower than the first measurement value. A method for manufacturing a piezoelectric element , comprising: discriminating a polarization direction of the piezoelectric element based on a bias electric field direction .