JP2004342630A - Piezoelectric ceramic and its manufacturing method, actuator, and print head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric ceramic having a small flatness and a small in-plane variation in a piezoelectric constant and a method of manufacturing the same, and to provide an actuator and a print head. <P>SOLUTION: The piezoelectric ceramic is characterised by having a thickness of 100 μm or less, a surface flatness of 20 μm or less, the maximum value of the unevenness of an arbitrary surface region of 2 mm × 2 mm of 3 μm or less, and an in-plane variation of dielectric constant of 5% or less of a mean dielectric constant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００９８】
【表２】

【００９９】
本発明の試料Ｎｏ．１〜４、６〜９、１１〜４４及び４６〜５９は、圧電磁気としてＰｂＺｒＴｉＯ_３（ＰＺＴ）を主成分としたもので、ｄ_３１のバラツキが１０％以下、変位量が７０ｎｍ以上であった。
【０１００】
一方、支持体の気孔率が６．５％と大きい焼成治具を使用したため、誘電率のばらつきが７％と大きい本発明の範囲外の試料Ｎｏ．５は、ｄ_３１のバラツキが１２％と大きかった。
【０１０１】
また、支持体の平坦度が３０μｍと大きい焼成治具を使用したため、誘電率のばらつきが８％と大きい本発明の範囲外の試料Ｎｏ．１０は、ｄ_３１のバラツキが１４％と大きかった。
【０１０２】
さらに、全体の厚みが１０００μｍ（１ｍｍ）と大きい本発明の範囲外の試料Ｎｏ．４５は、変位が２０ｎｍと小さく圧電特性が非常に低いものであった。
【０１０３】
【発明の効果】
本発明は、表面部の気孔率を５％以下に制御した支持体に、成形体を接触するように配置し、特に一対の支持体で成形体を挟持するように配置し、成形体を焼成することにより、厚み１００μｍ以下の薄層の試料でも平坦度が２０μｍ以下にするとともに、表面粗さ及び誘電体の面内バラツキを制御することができ、特に、密閉空間内に成形体支持体と重量体を載置して焼成することにより、特性の均一な圧電磁気を得ることができる。
【０１０４】
そして、圧電磁気を接合した際に発生する残留応力を低減し、圧電体の変形を防止するとともに、同一基板内に設けられた複数の圧電素子の変位バラツキを容易に制御でき、インクジェットプリンタの印刷ヘッドとして好適に用いることができる。
【図面の簡単な説明】
【図１】本発明の圧電磁気の製造方法を説明するための概略断面図である。
【図２】本発明の圧電磁気の他の製造方法を説明するための概略断面図である。
【図３】本発明のアクチュエータを示すもので、（ａ）は概略断面図、（ｂ）は概略平面図、（ｃ）は支持基板を接合した時の概略断面図である。
【図４】実施例で用いたアクチュエータを示すもので、支持基板を接合した時の概略断面図である。
【符号の説明】
１・・・アクチュエータ
２・・・圧電基板
３・・・支持基板
３ａ・・・インク流路
３ｂ・・・隔壁
４・・・圧電振動層
５・・・内部電極
６・・・表面電極
７・・・変位素子
８・・・インクノズル
Ｔ・・・アクチュエータの厚み
１０１、１１１・・・支持体
１０１ａ・・・下部支持体
１０１ｂ・・・上部支持体
１０２、１１２・・・成形体
１０４・・・支持体の主面
１０４ａ、１１４ａ・・・支持体の主面
１０４ｂ、１１４ｂ・・・天板の主面
１０５、１１５・・・スペーサ
１０６・・・天板
１０７、１１７・・・密封空間
１１８・・・支持天板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric ceramic, a method of manufacturing the same, an actuator, and a print head, for example, a piezoelectric sensor such as an acceleration sensor, a knocking sensor, and an AE sensor, a fuel injection injector, a print head for an inkjet printer, a piezoelectric resonator, an oscillator, and an ultrasonic wave. The present invention relates to a piezoelectric ceramic suitable for a motor, an ultrasonic vibrator, a filter, and the like, and particularly to a piezoelectric ceramic suitably used as a print head utilizing spread vibration, elongation vibration, and vertical vibration, a manufacturing method thereof, an actuator and a print head.
[0002]
[Prior art]
Conventionally, products using piezoelectric ceramics include, for example, piezoelectric actuators, filters, piezoelectric resonators (including oscillators), ultrasonic oscillators, ultrasonic motors, and piezoelectric sensors.
[0003]
Among these, for example, a piezoelectric actuator has a response speed of 10^-6Because of the extremely high speed of the order of seconds, it is applied to a piezoelectric actuator for positioning an XY stage of a semiconductor manufacturing apparatus, a piezoelectric actuator used for a print head of an ink jet printer, and the like.
[0004]
Conventionally, piezoelectric ceramics used in such applications have been manufactured by arranging and firing ceramic green sheets having a thickness of several hundred μm directly between a pair of setters made of a porous sintered body. .
[0005]
In addition, a spacer is arranged on a setter base made of a porous body, and a green sheet is arranged in a space formed by placing a setter lid made of a porous body on the spacer, and the green sheet and the setter are placed. It has been proposed to adjust the flatness of the sintered body to 30 to 100 μm by firing in a state where a space is provided so that the gap between the lids is 30 to 100 μm (for example, Patent Document 1).
[0006]
When the ceramic body obtained in this way is applied to a piezoelectric body, the smoothness of the porcelain can be kept below a certain value, so that the breakage when fixing the actuator on a flat surface such as a metal plate to fix it in the printer can be avoided. It has a feature that it can be avoided, and is suitably used as a printer head for an inkjet printer, an XY stage positioning actuator, or the like.
[0007]
[Patent Document 1]
JP 2000-281453 A (FIG. 3)
[0008]
[Problems to be solved by the invention]
However, in the method of Patent Document 1 in which a green sheet is sandwiched and fired by a porous body, a component that easily evaporates through pores is volatilized. As the in-plane variation increases and the surface condition of the porous body is difficult to control, the flatness of the obtained piezoelectric ceramic increases, and the flatness and surface The roughness has increased.
[0009]
Further, in the method of firing a thin green sheet described in Patent Document 1, the gap between the setter and the green sheet is at least 30 μm, and when obtaining an actuator having a thickness of 100 μm or less, the flatness of the porcelain is large with respect to the thickness. became.
[0010]
When the flatness is large as described above, when the actuator is fixed to the support substrate, the piezoelectric ceramic is stretched so as to correct the curved surface state of the piezoelectric ceramic to a flat state, so that uneven residual stress is generated in the piezoelectric substrate. Occurs. In particular, in the case of an actuator having a plurality of displacement elements provided on a piezoelectric substrate and having a thickness of 100 μm or less, there is a problem that the piezoelectric constant greatly varies depending on the displacement elements.
[0011]
Accordingly, an object of the present invention is to provide a piezoelectric ceramic having a small flatness and a small in-plane variation of a piezoelectric constant, a method of manufacturing the same, an actuator, and a print head.
[0012]
[Means for Solving the Problems]
The present invention can suppress deformation of the green sheet by baking while bringing the green sheet into contact with a support having a dense and flat surface, particularly, while sandwiching the green sheet with the support, and This method is based on the finding that evaporation from water can be suppressed, and by this method, a piezoelectric ceramic having a small flatness and a small variation in the dielectric constant can be manufactured, and as a result, the in-plane variation in the piezoelectric constant can be reduced. Can be.
[0013]
That is, the piezoelectric ceramic of the present invention has an overall thickness of 100 μm or less, a surface flatness of 20 μm or less, a maximum value of surface irregularities of 3 μm or less, and an in-plane variation in dielectric constant of 5% or less of the average dielectric constant. It is characterized by the following. If this piezoelectric ceramic is applied as an actuator, it is possible to suppress variation in displacement due to deformation of the piezoelectric ceramic, and as a result, it is possible to suppress variation in ink ejection amount as a print head of an inkjet printer.
[0014]
In particular, the surface roughness Ra of the main surface of the piezoelectric ceramic is preferably 3 μm or less. As a result, when the piezoelectric ceramic is fixed to a metal plate or the like as an actuator, the amount of deformation of the actuator due to correction can be further reduced, so that the residual stress generated inside the actuator can be further suppressed, and as a result, the Even in this case, the in-plane variation of the d constant of the actuator can be effectively reduced.
[0015]
It is preferable that the piezoelectric ceramic is a perovskite compound containing at least Pb. As a result, an actuator having a large displacement and capable of being driven at a low voltage can be manufactured. As a result, further contribution can be expected to higher speed, higher accuracy, and lower cost of the printer.
[0016]
Further, it is preferable that carbon contained in the piezoelectric ceramic is 0.1% by mass or less. As a result, the insulating properties of the piezoelectric ceramic can be ensured, and poor polarization during polarization processing can be prevented, and defective displacement can be prevented.
[0017]
Furthermore, d of the piezoelectric ceramic₃₁Is 150 pm / V or more,₃₁Is preferably 10% or less of the average value. This makes it possible to obtain a large displacement when used as an actuator, and can be suitably used for a print head of an inkjet printer.
[0018]
Further, in the method for manufacturing a piezoelectric ceramic according to the present invention, a molded body made of piezoelectric ceramic powder is brought into contact with a main surface of a support having a main surface with a porosity of 5% or less and a flatness of 20 μm or less on the surface. It is characterized by firing while heating. Thereby, the above-described piezoelectric ceramic can be manufactured.
[0019]
In particular, the surface roughness Ra of the main surface of the support is preferably 3 μm or less. This can further improve the flatness of the piezoelectric ceramic after firing, reduce residual stress, and suppress composition variation.
[0020]
In addition, it is preferable that the molded body is disposed so as to be sandwiched between the pair of the supports, and is fired. This makes it possible to easily obtain a flatness of 20 μm or less even with a thin piezoelectric ceramic having a thickness of 100 μm or less.
[0021]
Further, the support may be made of alumina, beryllia, zirconia, magnesia, mullite, spinel-type structure, bismuth layered compound, tungsten bronze structure compound, Pb-based perovskite structure compound, niobium-based perovskite structure compound, and tantalum-based perovskite structure compound It is preferable to contain at least one kind. Thereby, the reactivity with the green sheet can be suppressed.
[0022]
Furthermore, the support is CaO, MgO, Y₂O₃And zirconia containing any one of rare earths. Thereby, phase transformation of zirconia is suppressed, and cracking, deformation, and change in surface roughness of the jig due to heating and cooling during firing can be suppressed.
[0023]
Further, it is preferable that the average particle size of the crystals is 5 to 30 μm. Thereby, suppression of deformation and breakage during heating and cooling can be expected.
[0024]
Further, it is preferable that the compact is made of a raw material powder composed of a perovskite compound containing Pb, and the compact is inserted into a closed space and fired. This makes it easy to obtain a piezoelectric ceramic with less characteristic variation even with a molded body containing Pb, which is a volatile component.
[0025]
Volume V₃Having a larger area on the molded body than the molded body, having a surface roughness Ra of 1 μm or less, a flatness of 20 μm or less, and a volume V₂And the weight of the volume V₁In the enclosed space of
1.0001 × (V₂+ V₃) ≦ V₁≦ 4.0000 × (V₂+ V₃)
0.02 × V₃≤V₂≦ 50 × V₃
It is preferable to satisfy the following relationship. Evaporation of volatile components from the object to be fired can be suppressed, and variations in piezoelectric characteristics can be more effectively suppressed.
[0026]
An actuator of the present invention includes a piezoelectric substrate including the piezoelectric ceramic described above, a plurality of surface electrodes provided on a main surface of the piezoelectric substrate, and an internal electrode provided inside the piezoelectric substrate. And Accordingly, an actuator having a small flatness and a small in-plane variation of the piezoelectric constant even when bonded to a supporting substrate can be realized.
[0027]
In particular, it is preferable that the piezoelectric ceramic contains Pb and the internal electrode contains Ag. This makes it possible to lower the firing temperature especially in the case of a piezoelectric body containing Pb.
[0028]
The print head of the present invention is characterized in that the above-mentioned actuator is provided on a support substrate via an adhesive layer, and an ink flow path is provided inside the support substrate. As a result, a print head that enables stable printing can be realized, and this can be suitably used for an inkjet printer.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
It is important that the piezoelectric ceramic of the present invention has a thickness of 100 μm or less. By setting the thickness to 100 μm or less, a piezoelectric ceramic having a large displacement can be obtained. In order to further increase the displacement, the thickness of the porcelain is preferably 80 μm or less, more preferably 65 μm or less, more preferably 50 μm or less.
[0030]
On the other hand, the lower limit of the thickness of the piezoelectric ceramic is preferably 3 μm, particularly 5 μm, more preferably 10 μm, and more preferably 20 μm, in order to have sufficient mechanical strength and prevent breakage during handling and operation. .
[0031]
According to the present invention, it is also important that the surface flatness is 20 μm or less. By setting the flatness of the surface of the porcelain to 20 μm or less, variation in the porcelain characteristics can be suppressed. In order to further improve the uniformity of the characteristics, the thickness is particularly preferably 15 μm or less, more preferably 10 μm or less.
[0032]
According to the present invention, it is important that the maximum value of the irregularities on the surface of the piezoelectric ceramic is 3 μm or less. When the irregularities on the surface are small, it is easy to prevent minute deformation of the actuator when the piezoelectric body is fixed to a metal substrate or the like as an actuator, and the effect of reducing residual stress can be enhanced. Further, there is an effect that the evaporation component is suppressed from volatilizing through the surface unevenness, and the composition variation is further reduced.
[0033]
The range of the surface roughness Ra in the present invention is 100 μm, which indicates the unevenness of the surface, and the flatness is used to measure a large swell including warpage of the piezoelectric ceramic, and the surface unevenness is an intermediate between the two. Evaluation in the range, such evaluation in the intermediate range indicates the magnitude of partial undulation, and it is easy to improve the characteristic variation by reducing the partial undulation. .
[0034]
The specific measuring method is as follows. A device combining a laser focus displacement meter manufactured by KEYENCE CORPORATION and an XY stage scans 2 to 10 mm square, maps the surface height, and sets the maximum and minimum heights. The distance between them is the maximum value of the unevenness.
[0035]
According to the present invention, it is also important that the in-plane variation of the dielectric constant is 5% or less of the average dielectric constant. In this way, the average value is calculated by measuring the dielectric constant in the surface of the porcelain, and the maximum value of the variation from the average value is within 5% of the average value, thereby suppressing the variation of the piezoelectric characteristics in the substrate of the actuator. can do.
[0036]
The surface roughness Ra of the main surface of the piezoelectric ceramic is preferably 3 μm or less, particularly 2.5 μm or less, and more preferably 2 μm or less. When the surface roughness Ra is small, it is easy to effectively prevent minute deformation of the actuator when the piezoelectric body is fixed to the metal substrate or the like as an actuator, and the effect of reducing the residual stress can be enhanced. Further, there is an effect that the evaporation component is suppressed from volatilizing through the surface unevenness, and the composition variation is further reduced.
[0037]
The surface roughness Ra in the present invention is obtained by scanning an area of 100 μm × 100 μm using an atomic force microscope, measuring the unevenness of the surface, calculating the maximum value, and measuring the value of any five points in the plane. The average value was calculated.
[0038]
Piezoelectric ceramics can be used for the piezoelectric ceramic, and specifically, Bi layered compound, tungsten bronze structure material, perovskite structure compound of alkali Nb acid compound, lead magnesium niobate (PMN system), nickel niobate Examples of the material include lead (PNN), lead zirconate titanate containing Pb (PZT), and lead titanate.
[0039]
Among them, a perovskite compound containing at least Pb is particularly preferable. For example, a substance containing lead magnesium niobate (PMN-based), lead nickel niobate (PNN-based), lead zirconate titanate containing Pb (PZT), lead titanate, or the like is preferable. With such a composition, the piezoelectric vibration layer 4 having a high piezoelectric constant can be obtained. Among these, lead zirconate titanate and lead titanate containing Pb are preferable for obtaining a larger displacement.
[0040]
As an example of the perovskite-type crystal, PbZrTiO, which is a crystal containing Pb as an A-site constituent element and containing Zr and Ti as a B-site constituent element,₃Can be suitably used. Further, other oxides may be mixed, and as an auxiliary component, other elements may be substituted for the A site and / or the B site as long as the characteristics do not adversely affect the characteristics. For example, Zn, Sb, Ni and Te are added as sub-components, and Pb (Zn_1/3Sb_2/3) O₃And Pb (Ni_1/2Te_1/2) O₃May be a solid solution.
[0041]
According to the present invention, it is desirable that the perovskite-type crystal further contains an alkaline earth element as an A-site constituent element. Examples of the alkaline earth element include Ba, Sr, and Ca, and Ba and Sr are particularly preferable in that a high displacement can be obtained. As a result, the relative dielectric constant is improved, so that a higher piezoelectric constant can be obtained.
[0042]
Specifically, Pb_{1-x ― y}Sr_xBa_y(Zn_1/3Sb_2/3)_a(Ni_1/2Te_1/2)_bZr_1-abcTi_cO₃+ Α mass% Pb_1/2NbO₃(0 ≦ x ≦ 0.14, 0 ≦ y ≦ 0.14, 0.05 ≦ a ≦ 0.1, 0.002 ≦ b ≦ 0.01, 0.44 ≦ c ≦ 0.50, α = 0 .1 to 1.0).
[0043]
The piezoelectric ceramic preferably contains 0.1% by mass or less of carbon, particularly preferably 0.07% by mass or less. Since carbon contributes to the insulating properties of the piezoelectric material and causes insulation failure during polarization, it is possible to suppress current flow during polarization by suppressing the above range, and to polarize to a saturated polarization state. Displacement failure due to failure can be prevented.
[0044]
The porosity of the piezoelectric ceramic is preferably 5% or less, particularly 1% or less, and more preferably 0.5% or less. By reducing the porosity, the strength of the piezoelectric porcelain can be increased, and even if the thickness is small, destruction can be suppressed. In addition, when used as an inkjet print head, ink leakage due to ink seepage into porcelain is effective. It is possible to suppress it.
[0045]
When the piezoelectric ceramic of the present invention is used as an actuator for a print head of an ink jet printer, a piezoelectric strain constant, for example, d₃₁Modes are available. In order to demonstrate sufficient ejection capacity as a print head of an ink jet printer and realize high-speed and fine printing, d₃₁Is preferably 150 pm / V or more, particularly preferably 200 pm / V or more, and more preferably 250 pm / V or more.
[0046]
Next, a method for manufacturing a piezoelectric ceramic according to the present invention will be described by taking a piezoelectric ceramic applied to an actuator used in a print head as an example. Further, a case where PZT is used as the piezoelectric ceramic will be described as an example.
[0047]
First, a PZT powder having a purity of 99% and an average particle diameter of 1 μm or less is prepared as a piezoelectric powder used as a raw material.
[0048]
An appropriate organic binder is added to the PZT powder to form a tape, an Ag-Pd paste is applied to a desired portion of the tape as an internal electrode, and a via hole is formed at a desired portion and the inside of the via hole is formed. An electrode was formed. Next, the obtained green sheets are laminated to form a molded body. Also, if desired, it is cut into a specific shape.
[0049]
In order to fire the compact obtained by lamination, the compact is mounted on a jig and placed in a firing furnace. An example of the arrangement is shown in FIG. That is, the compact 102 is placed on the lower support 101a. Here, it is important that the porosity of the main surface 104a of the lower support 101a is 5% or less and the flatness is 20 μm or less, and that the main surface 104a is in contact with the molded body 102.
[0050]
Also, as shown in FIG. 1B, the spacer 105 is placed on the lower support 101a, and the top plate 106 is further placed on the spacer 105, and the lower support 101a, the spacer 105, The sealed space 107 may be formed by a firing jig made of the top plate 106, and the molded body 102 may be inserted into the sealed space 107 and fired. By providing such a sealed space 107, volatilization can be suppressed even in the case of a molded body containing a volatile component, so that firing can be performed without placing a common material around as in the related art. .
[0051]
Note that the sealed space 107 in the present invention is not simply provided as a set of the above-mentioned firing jigs to provide a space inside, but a support, a spacer, It refers to a device that can reduce the gap between the abutment portions by the top plate and suppress the scattering of volatile components. For example, there may be mentioned one whose surface is processed to have predetermined parallelism and surface roughness.
When the molded body is inserted into such a sealed space and fired, it is particularly preferable to satisfy the following conditions. That is, the volume of the closed space 107 is V₁, The volume of the upper support 101b is V₂, The volume V of the molded body 102₃When
1.0001 × (V₂+ V₃) ≦ V₁≦ 4.0000 × (V₂+ V₃)
0.02 × V₃≤V₂≦ 50 × V₃
It is preferable to satisfy the following relationship.
[0052]
The reason specified in the above range is that V₁Is 1.0001 × (V₂+ V₃If the ratio is smaller than (), the clearance between the upper support 101b and the spacer 105 becomes small, and the entrapment occurs due to expansion and contraction caused by heating and cooling during firing, and the workability tends to be significantly reduced. Also, V₁Is 4.0000 × (V₂+ V₃If the ratio is larger than the above, the amount of evaporation of the volatile component from the molded body increases, causing a change in composition, which tends to increase the variation in piezoelectric characteristics in the substrate. Also, V₂Is 0.02 × V₃If it is smaller, the sintered body tends to have irregularities, and 50 × V₃If it is larger, the contraction rate of the porcelain varies, and the dispersion of the piezoelectric characteristics in the substrate may be increased.
[0053]
In the present invention, as long as the molded body 102 is placed on the lower support 101a, anything may be placed on the molded body 102. For example, a porous body may be placed on the molded body 102. Placing the upper support 101b having the same main surface as the support 101a and arranging the molded body 102 so as to be sandwiched between the pair of lower supports 101a and 101b can effectively suppress the variation in composition, Further, it is preferable in that a flatness of 20 μm or less can be easily obtained.
[0054]
According to the present invention, it is important that the flatness of the main surface 104 where the lower supports 101a and 101b are in contact with the molded body 102 is 20 μm or less. Since the support body 101 comes into contact with the molded body 102, by flattening the main surface 104b in contact with the molded body 102, the flatness of the surface of the sintered body obtained by firing the molded body 102 can be reduced, and the surface becomes flat. A compact piezoelectric ceramic can be obtained. In particular, in order to obtain a sintered body with a smaller flatness, the flatness of the main surface of the support 101 is preferably 15 μm or less, more preferably 10 μm or less.
[0055]
According to the present invention, the porosity of the surface of the main surface 104 where the support 101 contacts the molded body 102 may be 5% or less, further 1% or less, and further 0.5% or less. is important. When the main surface 104 of the support 101 having such a small porosity is dense, the degranulation is small, the number of particles attached to the surface of the compact is reduced, and the flatness and surface roughness of the piezoelectric ceramic obtained by sintering are reduced. Can be improved.
[0056]
The surface portion means the surface of the main surface 104 which forms the contact surface with the molded body 102. However, in order to measure the porosity, polishing is required. A thickness, for example, a thickness of several μm is required, and this is substantially called a surface portion.
[0057]
In a conventional support made of a porous body, components volatilized from the molded body 102 during firing are scattered outside through continuous pores of the support, while at least the surface portion of the main surface 104 is scattered. Uses the dense support 101a, so that the scattering of volatile components can be significantly suppressed. As described above, by suppressing the evaporation of the volatile components from the molded body 102, the in-plane variation of the piezoelectric characteristics can be further improved.
[0058]
The support 101 is preferably dense as a whole. Such a dense body can be regenerated at low cost by processing the surface. Alternatively, a sintered body having a dense surface and a relatively high porosity inside can be used. For example, when sintering proceeds more easily on the surface than on the inside during sintering, the porosity of the surface layer of at least 0.1 mm, particularly 0.3 mm, and further 0.5 mm from the surface is 5% or less, particularly 1%. Hereinafter, it is better to be 0.5% or less.
[0059]
If desired, only the surface can be made dense. For example, the main surface 104 of the support 101 is made to have a porosity of 0.1% or less by polishing the surface of the ceramic sintered body having a porosity of about 2 to 8% and coating the ceramic layer. Can be. In particular, it is formed to a thickness of several tens μm or more, more preferably 50 μm or more, and more preferably 100 μm or more by CVD (chemical vapor deposition), and is subjected to mirror polishing to have a porosity of 1% or less and a flatness of 20 μm. It can be: This is when the cost for manufacturing the entire large support with a dense sintered body is high, or when it is difficult to synthesize a dense sintered body, or when the molded body and the support are likely to react. It is especially effective for
[0060]
The surface roughness Ra of the main surface 104 of the support 101 is preferably 3 μm or less, particularly 2.5 μm or less, and more preferably 2 μm or less. By setting the surface roughness Ra of the support 101 as described above, the flatness of the piezoelectric ceramic can be further improved. In addition, the gap between the molded body and the support serves as a diffusion path to evaporate volatile components from the molded body, thereby suppressing in-plane variation in composition.
[0061]
The support 101 used in the present invention is made of alumina, beryllia, zirconia, magnesia, mullite, spinel structure, bismuth layered compound, tungsten bronze structure compound, Pb-based perovskite structure compound, niobium-based perovskite structure compound, and tantalum-based perovskite structure compound It is preferable to contain at least one of these. These are all substances of the same quality or poor in reactivity of the piezoelectric body. By using such a substance for the support, the characteristics of the piezoelectric body can be stabilized.
[0062]
When the support 101 is made of zirconia, CaO, MgO, Y₂O₃And rare earth elements. This suppresses the phase transformation of zirconia during heating and cooling during firing, and suppresses breakage such as cracking and chipping, deformation, and change in surface roughness.
[0063]
Further, the average particle size of the crystals constituting the support 101 is 5 to 30 μm, particularly 10 to 25 μm, and furthermore, in order to reduce deformation due to heating and cooling, and to prevent cracks and chips from being significantly generated. Is preferably 15 to 20 μm.
[0064]
When firing a plurality of compacts, a plurality of compacts may be placed on the support plate 101 having a large width, or a plurality of firing jigs shown in FIG. You may use it repeatedly. Further, as shown in FIG. 2, a plurality of hermetically sealed spaces 117 are formed by alternately stacking spacers 115 and support top plates 118 which also serve as a support and a top plate on the support 111a. The molded body 112 may be placed inside the space, and the upper support 111b may be further placed thereon.
[0065]
Prior to firing of the molded body 102, a degreasing treatment may be performed at a temperature of about 400 ° C. to 900 ° C., if desired.
[0066]
An actuator can be manufactured by forming a surface electrode on the surface of the obtained sintered body and polarizing it.
[0067]
As described above, when the piezoelectric ceramic manufacturing method of the present invention is employed, even when an actuator formed of a thin layer having a thickness of 100 μm or less can be manufactured, deformation of the piezoelectric ceramic caused by uneven shrinkage during firing can be reduced. Residual stress generated when fixing to a support such as a road member can be reduced, d constants of a large number of displacement elements constituting the actuator become uniform, and variation in displacement amount can be significantly reduced. In addition, by applying such an actuator to a print head of an inkjet printer, high-speed and high-accuracy characteristics can be improved.
[0068]
Further, in the above-described embodiment, the piezoelectric actuator is described as an example. However, the piezoelectric displacement element of the present invention is not limited to the piezoelectric actuator, but may be, for example, an acceleration sensor, a knocking sensor, a piezoelectric sensor such as an AE sensor, an injector for fuel injection, The present invention can be applied to a print head for an inkjet printer, a piezoelectric resonator, an oscillator, an ultrasonic motor, an ultrasonic oscillator, a filter, and the like.
[0069]
An actuator of the present invention includes a piezoelectric substrate including the piezoelectric ceramic described above, a plurality of surface electrodes provided on a main surface of the piezoelectric substrate, and an internal electrode provided inside the piezoelectric substrate. It is assumed that.
[0070]
For example, as shown in FIG. 3A, a piezoelectric substrate 2 made of a piezoelectric ceramic, an internal electrode 5 provided inside the piezoelectric substrate 2, and a surface provided on a part of the main surface of the piezoelectric substrate 2 An electrode 6 is provided, and a displacement element 7 is constituted by the piezoelectric vibration layer 4, the internal electrode 5, and the surface electrode 6 formed on the surface of the piezoelectric substrate 2.
[0071]
In the actuator, for example, as shown in FIG. 3B, the surface electrodes 6 are two-dimensionally arranged at regular intervals, each is independently connected to an external electronic control circuit, and a voltage is applied between the electrodes. Is applied, the piezoelectric vibration layer 4 at the portion sandwiched between the internal electrode 5 and the surface electrode 6 to which the voltage is applied can be displaced. As described above, by applying each displacement element 7 to a print head that is independently controlled, it is possible to contribute to an increase in speed and accuracy of an inkjet printer.
[0072]
By setting the flatness of the surface of the piezoelectric substrate 2, that is, the flatness of the main surface of the piezoelectric vibrating layer 4 to 20 μm or less, the groove 3 a is formed by the partition wall 3 b, for example, as shown in FIG. Even when the actuator 1 of the present invention having a flat surface is joined to the support substrate 3, the deformation of the actuator 1 due to the joining is small and the residual stress can be reduced, so that the variation in characteristics of each displacement element can be reduced.
[0073]
The material of the internal electrode 5 may be any material containing at least Ag and having conductivity, for example, Au, Ag, Pd, Pt, Cu, Al, or an alloy thereof. Among them, Ag is preferable in that it enhances sinterability, has excellent conductivity, and is low in cost, and Pd is preferable in terms of conductivity and heat resistance. When the piezoelectric ceramic contains Pb, it is preferable to use Ag as the internal electrode 5 in order to promote a lower firing temperature.
[0074]
The thicknesses of the internal electrode 5 and the surface electrode 6 need to be such that they have conductivity and do not hinder the displacement, and are 0.1 to 5 μm, particularly 0.1 to 3 μm for the internal electrode. 2 to 0.5 μm is preferred.
[0075]
As shown in FIG. 3C, the print head of the present invention has the above-described actuator 1 bonded to the surface of the support substrate 3. The support substrate 3 has a plurality of ink channels 3a formed therein by partition walls 3b. The ink can be ejected from the ink nozzles 8 by pressurizing the ink by the displacement of the displacement element.
[0076]
According to the present invention, even in a print head in which several hundred displacement elements are densely arranged, it is possible to provide a print head with little displacement variation and as a result, uniform ink ejection characteristics.
[0077]
【Example】
First, a piezoelectric ceramic powder containing lead zirconate titanate having a purity of 99% or more was prepared as a raw material.
[0078]
The green sheet is obtained by adding butyl methacrylate as a water-based binder, ammonium polycarbonate as a dispersant, and isopropyl alcohol and pure water as a solvent to a ceramic powder for piezoelectric material containing lead zirconate titanate as a main component. After mixing, this slurry was formed on a carrier film by a doctor blade method in a sheet shape having a thickness of about 30 μm.
[0079]
Also, green sheets were prepared in the same manner using various types of piezoelectric ceramic powders. Further, an internal electrode paste was prepared. The obtained internal electrode paste was printed at a thickness of 4 μm on the surface of the green sheet to form internal electrodes. Further, one green sheet on which the internal electrode paste was not printed was laminated between two green sheets with the surface on which the internal electrodes were printed facing upward, and pressed to obtain a molded product.
[0080]
After the molded body is degreased, as shown in FIG. 1, the molded body is arranged to be sandwiched between a pair of supports, and a frame is arranged around the molded body to form a closed space. Thus, it was arranged in the firing furnace.
[0081]
The degree of stabilization when the support is zirconia is represented by the ratio of cubic crystals in the entire crystal phase. Specifically, the peak intensity by X-ray diffraction (XRD) is measured, and the degree of stabilization is determined. It was calculated from the following equation.
Stability = 100 x Vm / Vc
Here, Vm and Vc are volume fractions of a monoclinic crystal and a cubic crystal, respectively.
Vm = (lm (111) + lm (11-1)) / (lm (111) + lm (11-1) + lt (111) + lc (111))
Vc = lc (400) / (lc (400) + lt (400) + lt (004))
Is represented by Here, 1 indicates the integrated intensity (peak intensity) of each reflecting surface, and the subscripts m, t, and c indicate monoclinic, tetragonal, and cubic, respectively.
[0082]
The porosity of the support was measured by image analysis from a micrograph (× 200) of the mirror-polished surface. The flatness was evaluated by scanning the jig in the major axis direction and the vertical direction thereof using an apparatus combining a Keyence laser focus displacement meter and an XY stage, and evaluated using the larger value of the maximum value-minimum value. The average particle size G was determined by the relational expression G = 1.5 × L from the average section length L in the SEM photograph after mirror polishing and etching with boiling phosphoric acid.
[0083]
Also, V₁, V₂, V₃About V₁, V₂Was determined by the Archimedes method. V₃Was determined from the external dimensions of the molded body.
[0084]
Ra on the surface of the support was measured by scanning an area of 100 μm × 100 μm using an AFM, and determined from an average value of measured values at arbitrary five points in the plane.
[0085]
Whether or not Pb was contained on the surface of the support was confirmed by qualitative analysis using energy dispersive X-ray microanalysis (EDS / EPMA), and described as presence or absence.
[0086]
This is referred to as Sample No. Nos. 1 to 54 are 1000 ° C. No. 55 is 1130 ° C .; Nos. 56 to 58 were held for 2 hours in an atmosphere of 1200 ° C. and 99% or more of oxygen to obtain a piezoelectric ceramic comprising a piezoelectric vibrating layer and internal electrodes.
[0087]
The sample No. 59, a spacer having a thickness of 600 μm is placed on the porous support, another porous support is placed thereon, and the laminated molded product is placed between the upper and lower supports, and the Placed.
[0088]
The obtained piezoelectric ceramic was evaluated as follows.
[0089]
The thickness of the actuator was measured with a micrometer, and the surface roughness Ra of the actuator was measured with a stylus type surface roughness meter.
[0090]
The surface unevenness was calculated from the maximum value-minimum value by scanning a range of 2 mm in length and 2 mm in width by a combination device of a Keyence laser focus displacement meter and an XY stage.
[0091]
The flatness of the piezoelectric ceramic was determined from a change in height by scanning between one end and the other end of the sample using a combination device of a Keyence laser focus displacement meter and an XY stage.
[0092]
Whether or not Ag was present on the surface layer of the piezoelectric ceramic was confirmed by qualitative analysis of EDS / EPMA, and the presence or absence was confirmed.
[0093]
Next, a surface electrode was formed on one side of the surface of the obtained piezoelectric ceramic. Au electrodes were applied by screen printing to form 600 surface electrodes per substrate. This was baked in the air at 600 to 800 ° C.
[0094]
The dielectric constant ε was measured by measuring the capacitance at 1 kHz using an impedance analyzer (4194A manufactured by Agilent Technologies) and calculating from the thickness of the porcelain measured from the cross section.
[0095]
The piezoelectric constant is d₃₁Was measured at 10 points by a resonance method using an impedance analyzer (4194A manufactured by Agilent Technologies), and the average value was calculated. And d₃₁Is calculated, and the maximum value is calculated as d.₃₁Variations are shown as percentages.
[0096]
The displacement amount was measured in consideration of use as a print head for an ink jet printer. As shown in FIG. 4, the actuator 11 produced above was bonded to a support 13 having a groove 13a and a partition 13b. The displacement element 17 was manufactured such that the structure 14 was sandwiched between the internal electrode 15 and the surface electrode 16. Then, the actuator is irradiated with a laser beam through the groove 13a from the support 13 side by a laser Doppler displacement meter, and the center and peripheral portions of the actuator in contact with the groove 13a of the support 13 are measured to measure the displacement. Then, the average value was calculated. The results are shown in Tables 1 and 2.
[0097]
[Table 1]

[0098]
[Table 2]

[0099]
Sample No. of the present invention 1-4, 6-9, 11-44 and 46-59 are PbZrTiO as piezoelectric magnetism.₃(PZT) as the main component, d₃₁Was 10% or less, and the displacement was 70 nm or more.
[0100]
On the other hand, since a sintering jig having a porosity of the support of as large as 6.5% was used, the variation of the dielectric constant was as large as 7%, and the sample No. was out of the range of the present invention. 5 is d₃₁Was as large as 12%.
[0101]
Further, since a firing jig having a large flatness of the support of 30 μm was used, the variation of the dielectric constant was as large as 8%. 10 is d₃₁Was as large as 14%.
[0102]
Further, the sample No. having a large overall thickness of 1000 μm (1 mm), which is out of the range of the present invention. In No. 45, the displacement was as small as 20 nm and the piezoelectric characteristics were very low.
[0103]
【The invention's effect】
According to the present invention, the molded body is disposed so as to be in contact with a support having a porosity of 5% or less at the surface portion, and particularly, the molded body is disposed so as to be sandwiched between a pair of supports, and the molded body is fired. By doing so, even with a thin layer sample having a thickness of 100 μm or less, the flatness can be reduced to 20 μm or less, and the surface roughness and the in-plane variation of the dielectric can be controlled. By mounting and firing the weight body, it is possible to obtain piezoelectric magnetism having uniform characteristics.
[0104]
In addition to reducing the residual stress generated when joining the piezoelectric magnetism, preventing the deformation of the piezoelectric body, the displacement variation of a plurality of piezoelectric elements provided on the same substrate can be easily controlled, and the printing of the ink jet printer can be performed. It can be suitably used as a head.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view for explaining a method of manufacturing a piezoelectric magnet according to the present invention.
FIG. 2 is a schematic cross-sectional view for explaining another method of manufacturing the piezoelectric magnetism of the present invention.
3 (a) is a schematic sectional view, FIG. 3 (b) is a schematic plan view, and FIG. 3 (c) is a schematic sectional view when a supporting substrate is joined.
FIG. 4 is a schematic cross-sectional view showing an actuator used in an example, when a supporting substrate is joined.
[Explanation of symbols]
1 ... actuator
2 ... Piezoelectric substrate
3 ... Support substrate
3a: ink flow path
3b ... partition wall
4 ... Piezoelectric vibration layer
5 ... Internal electrode
6 ... Surface electrode
7 ... displacement element
8 ... Ink nozzle
T: Actuator thickness
101, 111 ... support
101a: Lower support
101b: Upper support
102, 112: molded body
104: Main surface of support
104a, 114a... Main surface of the support
104b, 114b ... main surface of the top plate
105, 115 ... spacer
106 ・ ・ ・ Top plate
107, 117 ... sealed space
118 ・ ・ ・ Support top plate

Claims (16)

A piezoelectric ceramic having a thickness of 100 μm or less, a surface flatness of 20 μm or less, a maximum value of surface irregularities of 3 μm or less, and an in-plane variation in dielectric constant of 5% or less of an average dielectric constant. 2. The piezoelectric ceramic according to claim 1, wherein the surface roughness Ra of the main surface of the piezoelectric ceramic is 3 [mu] m or less. The piezoelectric ceramic according to claim 1, wherein the piezoelectric ceramic is a perovskite compound containing Pb. The piezoelectric ceramic according to any one of claims 1 to 3, wherein carbon contained in the piezoelectric ceramic is 0.1% by mass or less. The average value of d ₃₁ of the piezoelectric ceramic is 150 pm / V or more, the piezoelectric according to claim 1, in-plane variation of the d ₃₁ is equal to or less than 10% of the mean value porcelain. A method for producing a piezoelectric ceramic, comprising: sintering a molded body made of piezoelectric ceramic powder while contacting a main surface of a support having a main surface with a porosity of 5% or less and a flatness of 20 μm or less on the surface. Method. 7. The method according to claim 6, wherein the surface roughness Ra of the main surface of the support is 3 μm or less. The method of manufacturing a piezoelectric ceramic according to claim 6, wherein the molded body is disposed so as to be sandwiched between a pair of the support members and fired. The support may be at least one of alumina, beryllia, zirconia, magnesia, mullite, a spinel structure, a bismuth layered compound, a tungsten bronze structure compound, a Pb-based perovskite structure compound, a niobium-based perovskite structure compound, and a tantalum-based perovskite structure compound. The method for producing a piezoelectric ceramic according to any one of claims 6 to 8, comprising a seed crystal. Said _{support, CaO, MgO, Y 2 O} 3, the manufacturing method of the piezoelectric ceramic according to any one of claims 6-9, characterized in that the zirconia containing any one of rare earth. The method of manufacturing a piezoelectric ceramic according to any one of claims 6 to 10, wherein an average particle diameter of the crystal constituting the support is 5 to 30 m. The piezoelectric ceramic according to any one of claims 6 to 11, wherein the compact is made of a raw material powder made of a perovskite-type compound containing Pb, and the compact is inserted into a closed space and fired. Manufacturing method. A forming body having a volume V _3, on the molded product, the surface roughness Ra is 1μm or less, is 20μm or less flatness, by placing the weight of the volume V ₂ in the sealed space volume V ₁ 1 0.0001 × (V ₂ + V ₃ ) ≦ V ₁ ≦ 4.0000 × (V ₂ + V ₃ )
0.02 × V ₃ ≦ V ₂ ≦ 50 × V ₃
13. The method according to claim 12, wherein the following relationship is satisfied. A piezoelectric substrate comprising the piezoelectric ceramic according to claim 1, a plurality of surface electrodes provided on a main surface of the piezoelectric substrate, and an internal electrode provided inside the piezoelectric substrate. An actuator, characterized in that: 14. The actuator according to claim 13, wherein the piezoelectric ceramic includes Pb, and the internal electrode includes Ag. 16. A print head, wherein the actuator according to claim 14 or 15 is provided on a support substrate via an adhesive layer, and an ink flow path is provided inside the support substrate.

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