JP4497850B2 - Piezoelectric actuator and ink jet recording head having the same - Google Patents

Description

【００９０】
表１から、本発明の範囲外であるランド部間凹部９ｃ及び個別電極間凹部１７のない試料Ｎｏ．１は、駆動変位量ばらつきが、２０％となり、変位量低下率が、３２％となり接続不良率が５０％となった。この接続不良率は非常に高く、ほとんど良品が作製できないレベルである。
【００９１】
一方、ランド部間凹部９ｃのみを設けた本発明の範囲の試料Ｎｏ．２では、駆動変位量ばらつきが、１２％となり、また、変位量低下率が、１５％となり、接続不良率が７％となった。試料Ｎｏ．１と比較すると全ての項目で改善が見られるが、特に、接続不良率の改善が著しい。
【００９２】
また、個別電極間凹部１７を設けた試料Ｎｏ．３は、駆動変位量ばらつきが、１７％となり、また、変位量低下率が、１７％となり、接続不良率が２％となった。さらに、個別電極間凹部１７と、凸部２３を設けた試料Ｎｏ．４は、駆動変位量ばらつきが、１７％となり、また、変位量低下率が、１４％となり、接続不良率が１％となった。個別電極間凹部１７を設けることで、接続不良率が格段に低くなった。
【００９３】
また、さらに、ランド部間凹部９ｃと個別電極間凹部１７と凸部２３とを具備する試料Ｎｏ．５〜２８では駆動変位量ばらつきが、１３％以下となり、また、変位量低下率が、２０％以下となり、接続不良率が１％以下となった。
【００９４】
【発明の効果】
本発明の圧電アクチュエータによれば、振動板上に、共通電極、圧電セラミック層および個別電極がこの順に積層され、前記個別電極が、圧電駆動に寄与する駆動部とこの駆動部の一端に接続されている駆動電圧印加用のランド部とを備えているとともに、前記圧電セラミック層の表面に複数配列されている圧電アクチュエータであって、前記圧電セラミック層の前記個別電極が設けられている主面の前記ランド部に接続されている前記駆動部の一端と該駆動部の他の部分との間の位置に前記圧電セラミック層を切り欠いてランド部間凹部が形成されているか、前記圧電セラミック層の前記個別電極が設けられている主面の前記個別電極間に前記圧電セラミック層を切り欠いて個別電極間凹部が形成されていることで、仮に、ランド部上に形成された端子電極が溶融するなどして、ランド部から流れ出したとしても、ランド部間凹部または個別電極間凹部でその流れを食い止めることができるため、溶融した金属が隣接する個別電極と接触し、電気的に短絡することを抑制することができる。また、駆動部直下の圧電セラミックス層の振動が、隣接する駆動部へ与える影響を抑制することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態にかかる圧電アクチュエータを備えたインクジェット記録ヘッドを示す断面図である。
【図２】本発明の圧電アクチュエータにおいて、ランド部間凹部、個別電極間凹部の形成状態を示す平面図である。
【図３】個別電極間凹部の形状を示す断面図である。
【図４】（ａ）〜（ｄ）は、本発明における圧電アクチュエータの製造工程を示す断面図である。
【図５】本発明の圧電アクチュエータにおいて、個別電極の外側にランド部間凹部を設けた本発明の他の形態のランド部間凹部の形成状態を示す平面図である。
【図６】従来の圧電アクチュエータを備えたインクジェット記録ヘッドを示す断面図である。
【図７】従来の圧電アクチュエータを示す平面図である。
【符号の説明】
１・・・圧電アクチュエータ
３・・・振動板
５・・・共通電極
７・・・圧電セラミック層
９・・・個別電極
９ａ・・・駆動部
９ｂ・・・ランド部
９ｃ・・・ランド部間凹部
１１・・・導体層
１３、１５・・・セラミック層
１７・・・個別電極間凹部
２１・・・端子電極
２３・・・凸部
２４・・・インク吐出口
２５・・・インク流路
２７・・・流路部材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin layered piezoelectric actuator and an ink jet recording head which are used for a piezoelectric actuator, particularly an ink jet recording head.
[0002]
[Prior art]
In recent years, with the spread of personal computers and the development of multimedia, the use of ink jet printers as recording apparatuses that output information to recording media is rapidly expanding. Such a printer is equipped with an ink jet recording head. As the ink jet recording head, a piezoelectric method is widely used in that the head can be easily reduced in size and thickness and high-precision printing is possible (see Patent Document 1).
[0003]
FIG. 6 is a sectional view showing an ink jet recording head provided with a conventional piezoelectric actuator. As shown in FIG. 6, generally, an ink jet recording head is obtained by laminating and bonding a piezoelectric actuator 41 on a flow path member 43.
[0004]
The piezoelectric actuator 41 is configured such that a common electrode 52, a piezoelectric ceramic layer 53, and individual electrodes 54 are laminated in this order on a diaphragm 51, and a plurality of individual electrodes 54 are arranged on the surface of the piezoelectric ceramic layer 53. The flow path member 43 is configured by disposing a substrate 62 having an ink discharge port 63 on the lower surface of the partition wall 60 forming the ink flow path 61. The diaphragm 51 is a laminate of a pair of ceramic layers 56 and 57 with a conductor layer 55 interposed therebetween. The individual electrode 54 includes a driving unit 54a that contributes to piezoelectric driving, and a land portion 54b for applying a driving voltage connected to one end of the driving unit 54a. Each drive unit 54 a is disposed at a position corresponding to the ink flow path 61. A flexible wiring board 64 is disposed above the piezoelectric actuator 41 and is connected to the land portion 54 b of the individual electrode 54 via the terminal electrode 65.
[0005]
In such an ink jet recording head, a piezoelectric ceramic layer immediately below the drive unit 54a is applied by energizing the land portion 54b from the flexible wiring board 64 and applying a voltage between the drive unit 54a of the individual electrode 54 and the common electrode 52. Piezoelectric vibration can be generated in the nozzle 53 so that a predetermined amount of ink can be discharged from the ink discharge port 63.
[0006]
These individual electrodes 54 are two-dimensionally arranged on the piezoelectric ceramic layer 53 as shown in FIG.
[0007]
[Patent Document 1]
JP 2002-292860 A
[0008]
[Problems to be solved by the invention]
In the piezoelectric actuator 41 as described above, the electrical connection between the flexible wiring board 64 and the piezoelectric actuator 41 is provided, for example, with solder paste, solder balls or the like serving as the terminal electrodes 65 provided on the flexible wiring board 64 and the piezoelectric actuator 41. It is arranged between the land portions 54b and is formed by heating or the like. At that time, the molten solder flows out and spreads to the individual electrodes 54, changes the characteristics of the drive unit 54a, There was a problem of electrical shorting.
[0009]
When the land portion 54b is energized, not only the piezoelectric ceramic layer 53 above the ink flow path 61a vibrates but also slightly vibrates the piezoelectric ceramic layer 53 above the adjacent ink flow path 61b. Therefore, the piezoelectric vibration in the piezoelectric ceramic layer 53 below the adjacent individual electrode 54 may be affected, and desired piezoelectric vibration may be hindered. As a result, the amount of displacement of the piezoelectric ceramic layer 53 becomes smaller than a predetermined value, causing variations in the amount of displacement, resulting in variations in the ink discharge amount.
[0010]
Particularly, in recent years, as the density of the ink jet recording head is increased, the individual electrodes 54 are highly integrated, and the interval between the adjacent individual electrodes 54 is reduced. Therefore, the above problem tends to become more prominent.
[0011]
Accordingly, an object of the present invention is to provide a piezoelectric actuator capable of reducing variation in displacement even when the degree of integration is high, and an ink jet recording head including the piezoelectric actuator.
[0012]
[Means for Solving the Problems]
In the piezoelectric actuator of the present invention, a common electrode, a piezoelectric ceramic layer, and an individual electrode are laminated in this order on a diaphragm, and the individual electrode is connected to a drive unit that contributes to piezoelectric drive and one end of the drive unit.ingWith land for driving voltage applicationHaveAnd a plurality of arrays are arranged on the surface of the piezoelectric ceramic layer.ingA piezoelectric actuator, wherein the individual electrodes of the piezoelectric ceramic layer are provided.ingBetween the land parts on the main surfaceThe piezoelectric ceramic layer is cut out at a position between one end of the driving unit connected to the other part and the other part of the driving unit.Concavity between landsButFormationHas beenIt is characterized by that.
[0013]
  thisIt is formed by cutting out the piezoelectric ceramic layer.The recess between the land parts, ExampleFor example, it has a function like a dam, and even if the terminal electrode formed on the land part melts and flows out from the land part, the flow can be stopped at the recessed part, It can be suppressed that the molten metal spreads on the individual electrodes and inhibits the piezoelectric vibration of the drive unit. Moreover, it can suppress that the molten metal contacts with the adjacent individual electrode and is electrically short-circuited.Further, it is possible to suppress the vibration of the piezoelectric ceramic layer provided under the individual electrode from affecting the piezoelectric ceramic layer provided under the adjacent individual electrode.
[0014]
  In the piezoelectric actuator of the present invention, a common electrode, a piezoelectric ceramic layer, and an individual electrode are laminated in this order on a vibration plate, and the individual electrode is connected to a driving unit that contributes to piezoelectric driving and one end of the driving unit.ingWith land for driving voltage applicationHaveAnd a plurality of arrays are arranged on the surface of the piezoelectric ceramic layer.ingA piezoelectric actuator, wherein the individual electrodes of the piezoelectric ceramic layer are provided.IsBetween the individual electrodes on the main surfaceCut out the piezoelectric ceramic layerRecesses between individual electrodesButFormationHas beenIt is characterized by that.
[0015]
The recesses between the individual electrodes are formed by cutting out the piezoelectric ceramic layer, for example, and have a dam-like function. If the terminal electrodes formed on the land portions are melted, Even if it flows out, the flow can be stopped by the recesses between the individual electrodes, so that an electrical short circuit between adjacent individual electrodes can be suppressed, and vibration of the piezoelectric ceramic layer provided under the individual electrodes can be transmitted. Can be blocked by the recesses between the individual electrodes, so that the influence on the piezoelectric ceramic layer provided under the adjacent individual electrodes can be suppressed.
[0016]
  In addition, the individual powerExtremeBetween the land partsThe drive part is cut out in the drive part of the secondConcavity between landsButFormationHas beenIt is characterized by that.
[0017]
  In such a piezoelectric actuator,SecondThe recess between the land portions has a function of preventing the molten metal from spreading on the individual electrodes and inhibiting the piezoelectric vibration of the drive unit. The recess between the individual electrodes is between the adjacent individual electrodes. In addition to being able to suppress the electrical short circuit, the transmission of vibration of the drive unit is blocked by the recesses between the individual electrodes, so that it has the function of suppressing the influence on the adjacent drive unit, By providing these two types of recesses, it is possible to suppress variation in the amount of drive displacement of the drive unit, reduction in the amount of drive displacement during adjacent drive, and electrical shorting between the individual electrodes.
[0018]
In the piezoelectric actuator of the present invention, it is desirable that at least two interelectrode recesses are formed between adjacent individual electrodes. By setting it as such a shape, even if it supplies with electricity simultaneously to the adjacent individual electrode, the influence on the piezoelectric ceramic layer provided under the adjacent individual electrode can be suppressed more effectively.
[0019]
In addition, even if adjacent terminal electrodes melt at the same time and flow out of the land portion, it is possible to stop each flow at the recesses between the individual electrodes. Can be more effectively suppressed.
[0020]
  In the piezoelectric actuator of the present invention, it is desirable that a recess between the individual electrodes is formed surrounding the individual electrode. By forming the recesses between the individual electrodes in this way, it is possible to suppress the influence on the piezoelectric ceramic layer provided under all the adjacent individual electrodes.
[0021]
In addition, even if the adjacent terminal electrode melts and flows out from the land portion, the molten metal always reaches the recess between the individual electrodes before reaching the adjacent individual electrode, so that the flow should be stopped. Thus, an electrical short circuit between adjacent individual electrodes can be more effectively suppressed.
[0022]
In the piezoelectric actuator of the present invention, it is desirable that the maximum depth of the recesses between the individual electrodes is 3 μm or more. Thus, by setting the maximum depth of the recesses between the individual electrodes to 3 μm or more, it is possible to more effectively suppress the influence on the piezoelectric ceramic layer provided under the adjacent individual electrodes.
[0023]
Further, even if the adjacent terminal electrode melts and flows out from the land portion, the molten metal is once stored in the space in the recess between the individual electrodes, and it becomes difficult to go out of the recess between the individual electrodes again. Therefore, an electrical short circuit between adjacent individual electrodes can be further effectively suppressed.
[0024]
In the piezoelectric actuator of the present invention, it is desirable that the maximum depth of the recesses between the individual electrodes is 30% or more of the thickness of the piezoelectric ceramic layer. Thus, by setting the maximum depth of the recesses between the individual electrodes to 30% or more of the thickness of the piezoelectric ceramic layer, the influence on the piezoelectric ceramic layer provided under the adjacent individual electrode can be sufficiently suppressed. it can.
[0025]
  Further, in the piezoelectric actuator of the present invention, the convex portion around the concave portion between the individual electrodes.ButFormationHas beenIt is desirable. By providing a protrusion around the recess between the individual electrodes in this way, even if the adjacent terminal electrode melts and flows out from the land portion, the molten metal will flow before flowing into the recess between the individual electrodes. Since the protrusion is temporarily stopped by the convex portion, a double barrier is provided by the concave portion between the individual electrodes and the convex portion, and an electrical short circuit between adjacent individual electrodes can be more effectively suppressed.
[0026]
In the piezoelectric actuator of the present invention, it is desirable that the height of the convex portion is 3 μm or more. By setting the height of the convex portion to 3 μm or more, even if the adjacent terminal electrode melts and flows out from the land portion, the convex portion can stop, and the amount of metal that can be stopped by the convex portion Can be sufficient, and an electrical short circuit between adjacent individual electrodes can be more effectively suppressed.
[0027]
In the piezoelectric actuator of the present invention, it is desirable that the height difference between the convex portion and the concave portion between the individual electrodes is 6 μm or more. By making the height difference between the convex part and the concave part between the individual electrodes 6 μm or more, it becomes difficult for the molten metal to overcome the double barrier composed of the convex part and the concave part between the individual electrodes, and it is more effective. It is possible to suppress an electrical short circuit between the individual electrodes adjacent to each other.
[0028]
In the piezoelectric actuator of the present invention, it is desirable that the maximum width of the recesses between the individual electrodes is 20 μm or more. By setting the maximum width of the recesses between the individual electrodes to 20 μm or more, for example, even when the melted metal has a high viscosity and the surface tension is large, the melted metal can be stored in the recesses between the individual electrodes. It is possible to suppress an electrical short circuit between the individual electrodes adjacent to each other.
[0029]
Further, in the piezoelectric actuator of the present invention, the volume of the space formed by the recesses between the individual electrodes corresponding to the individual electrodes or the recesses and the protrusions between the individual electrodes is a distance connecting the diameter or diagonal of the land portion. It is desirable that it is 8-30% of the provisional terminal electrode volume obtained by the third power.
[0030]
The volume calculated by squaring the area of the land portion is considered to be substantially equal to the volume of the terminal electrode provided on the land portion. Therefore, even if the adjacent electrode electrodes are melted and flowed out from the land portion by setting the volume of the space formed by the recesses between the individual electrodes or the recesses and the protrusions between the individual electrodes within the above range, Since the flow can be completely stopped, an electrical short circuit between adjacent individual electrodes can be more effectively prevented.
[0031]
  In addition, the ink jet recording head of the present invention includes the piezoelectric actuator described above, in which a plurality of ink flow paths having ink discharge ports are arranged.ingOn the flow path member, the ink flow path and the individual electrode are aligned at the same position.Has beenIt is characterized by that.
[0032]
Such an ink jet recording head can suppress interference between piezoelectric ceramic layers provided under adjacent individual electrodes even when a piezoelectric actuator is driven, so that a fine image can be drawn. In addition, even if excessive heat is applied to the ink jet recording head and the terminal electrode provided on the land portion melts, the electrical short circuit between adjacent individual electrodes is suppressed. Therefore, the ink jet recording head is excellent in reliability.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a piezoelectric actuator according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an ink jet recording head provided with the piezoelectric actuator of the present embodiment.
[0034]
As shown in FIG. 1, in the piezoelectric actuator 1, a common electrode 5, a piezoelectric ceramic layer 7, and individual electrodes 9 are laminated in this order on a diaphragm 3, and the individual electrodes 9 are two-dimensionally formed on the surface of the piezoelectric ceramic layer 7. And a plurality of them are regularly arranged. In this way, the individual electrodes 9 are two-dimensionally and regularly arranged, so that the ink jet printer can be increased in speed and definition. The individual electrode 9 includes a drive unit 9a that contributes to piezoelectric driving, and a drive voltage application land unit 9b connected to one end of the drive unit 9a. A land-to-land recess 9c is formed around the land 9b. The piezoelectric actuator 1 can generate a piezoelectric vibration in the piezoelectric ceramic layer 7 immediately below the drive unit 9a by applying a voltage between the drive unit 9a of the individual electrode 9 and the common electrode 5.
[0035]
The diaphragm 3 is formed by laminating a pair of ceramic layers 13 and 15 via a conductor layer 11, and is integrated with the common electrode 5, the piezoelectric ceramic layer 7 and the like by simultaneous firing. The diaphragm 3 also plays a role of correcting warp deformation generated in the piezoelectric ceramic layer 7. It is desirable that the common electrode 5 and the conductor layer 11 are electrically connected. Thereby, it is possible to reduce power loss due to piezoelectric vibration of the diaphragm 3 that is induced and generated when the piezoelectric ceramic layer 7 is displaced.
[0036]
And in the piezoelectric actuator 1 of this invention, the recessed part 17 between individual electrodes is provided in the surface of the piezoelectric ceramic layer 7 between the individual electrodes 9. FIG.
[0037]
FIG. 2 is a plan view showing a formation state of the land-to-land recesses 9 c formed around the land 9 b and the individual-electrode recesses 17 provided on the surface of the piezoelectric ceramic layer 7 between the individual electrodes 9.
[0038]
As shown in FIGS. 1 and 2, the land-to-land recess 9c formed around the land 9b is formed so as to cut out the individual electrodes 9 around the land 9b.
[0039]
For example, when the solder paste or solder ball is disposed on the land portion 9b and heated to provide the terminal electrode 21, the land-to-land recess portion 9c is excessively heated, misaligned with the solder paste or solder ball, or excessive. Even if the metal that becomes the molten terminal electrode 21 flows out of the land portion 9b due to supply of an appropriate amount, the metal flows into the inter-land-portion concave portion 9c. It has a function of preventing the change of the characteristics of 19c.
[0040]
It should be noted that such a function is not effective only for the molten metal, and is effective even when, for example, a conductive resin composed of metal particles and a resin is used as the terminal electrode 21. Not too long.
[0041]
  Further, in FIG. 1, a land-to-land recess (second land-to-land recess) 9 c is formed through the individual electrode 9, and is formed at the bottom of the land-to-land recess (second land-to-land recess) 9 c. The individual electrode 9 is not formed, but the land-to-land recess (second land-to-land recess) 9c only needs to be a recess, so the land-to-land recess (second land) does not pass through the individual electrode 9. It is desirable that the individual electrodes 9 are formed at the bottom of the inter-part recesses 9c because the electrical resistance of the individual electrodes 9 can be reduced. Further, the piezoelectric ceramic layer 7 positioned further below the individual electrode 9 may be further cut away in order to increase the volume of the land-to-land recess (second land-to-land recess) 9c.
[0042]
The inter-individual electrode recess 17 provided on the surface of the piezoelectric ceramic layer 7 between the individual electrodes 9 is formed so as to surround each individual electrode 9 so as to cut out the surface of the piezoelectric ceramic layer 7. 9, even if the drive unit 19 a composed of the piezoelectric ceramic layer 7 and the common electrode 5 is energized and piezoelectrically vibrates, it has a function of suppressing or blocking the influence on the adjacent drive units 19 b and 19 c. .
[0043]
The inter-individual electrode recesses 17 are, for example, when a solder paste or solder ball is disposed on the land portion 9b and heated to provide the terminal electrode 21. Even if the metal that becomes the melted terminal electrode 21 flows out of the land portion 9b due to misalignment or supply of an excessive amount, the metal flows into the recesses 17 between the individual electrodes. It also has a function of suppressing the individual electrodes 9 from being electrically short-circuited.
[0044]
Such a function does not work effectively only for the molten metal, and it goes without saying that, for example, a conductive resin made of metal particles and resin or the like is used as the terminal electrode 21. Absent.
[0045]
Furthermore, it also has a function of suppressing the flux component contained in the solder paste or the like from reaching the individual electrode 9.
[0046]
The maximum depth of the recesses 17 between the individual electrodes is set so that the metal once flowing into the recesses 17 between the individual electrodes does not reach the adjacent individual electrodes 9 beyond the adjacent recesses 17 between the individual electrodes. From the viewpoint of suppressing the influence on the adjacent drive units 19b and 19c, it is preferably 3 μm or more, and more preferably 5 μm or more.
[0047]
Further, it is desirable that the maximum depth (FIG. 1 t <b> 2) of the recesses 17 between the individual electrodes is in a range of 30 to 90% of the thickness (FIG. 1 t <b> 1) of the piezoelectric ceramic layer 7.
[0048]
Thus, by setting it as 30% or more, the influence on the adjacent drive part 19 can be suppressed, and by setting it as 90% or less, it is in the part which provided the recessed part 17 between the individual electrodes of the piezoelectric ceramic layer 7. Even if stress is applied, destruction can be prevented.
[0049]
Further, by setting the ratio in the range of 50 to 80%, the balance between the suppression of the influence on the adjacent drive unit 19 and the strength of the piezoelectric ceramic layer 7 provided with the individual interelectrode recesses 17 is improved.
[0050]
Further, by setting the maximum width w1 of the recesses 17 between the individual electrodes shown in FIG. 3A to 20 μm or more, even if the molten metal has a high viscosity and a high surface tension, the metal is not recessed. 17 can be made to flow in favorably, and the effect of the recesses 17 between the individual electrodes can be further increased.
[0051]
Further, as shown in FIGS. 3A and 3B, it is desirable that a convex portion 23 be provided around the concave portion 17 between the individual electrodes. The convex portion 23 functions like a bank. For example, even if the molten metal moves from the right side of FIG. 3B, the molten metal is individually separated as long as it does not exceed the height t3 of the convex portion 23a. It does not flow into the interelectrode recess 17.
[0052]
Therefore, the height t3 of the convex portion 23 is desirably 3 μm or more, and further desirably 5 μm or more.
[0053]
Further, even if the molten metal flows into the inter-electrode recess 17 beyond the height t3 of the protrusion 23a, the metal once flowing into the inter-electrode recess 17 exceeds the protrusion 23b. Since it is necessary to exceed the height t3 of the convex portion 23b in addition to the maximum depth t2 of the inter-concave portion 17, it is desirable that t2 + t3 is 6 μm or more. Further, it is desirable that the thickness is 10 μm or more.
[0054]
Further, the volume of the space formed by the individual electrode recesses 17 or the individual electrode recesses 17 and the projections 23 formed in this way is multiplied by the cube of the land 9b diameter or diagonal distance. By setting the volume of the provisional terminal electrode 21 to be 8-30%, even if most of the terminal electrode 21 formed on the land portion flows out, an electrical short circuit with the adjacent individual electrode 9 is prevented. Can be prevented.
[0055]
In addition, the thickness of the piezoelectric actuator 1 is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 50 μm or less in terms of increasing the amount of displacement. On the other hand, the lower limit value of the thickness of the piezoelectric actuator 1 is preferably 20 μm or more in order to have a mechanical strength that does not break during handling or operation and to withstand the applied voltage. Is 25 μm or more, more preferably 30 μm or more.
[0056]
In addition, the thickness of the piezoelectric ceramic layer 7 and the thickness of each of the ceramic layers 13 and 15 are preferably 30 μm or less from the viewpoint of miniaturization and thinning, and have a mechanical strength that does not break during handling or operation. In order to withstand the applied voltage, the thickness is more preferably in the range of 10 to 20 μm.
[0057]
The thicknesses of the common electrode 5 and the conductor layer 11 are 0.5 μm or more, preferably 1 μm or more. Thereby, the rigidity of the piezoelectric actuator 1 can be improved and the effect of suppressing warpage deformation can be enhanced. The difference between the thickness of the common electrode 5 and the thickness of the conductor layer 15 is 5 μm or less, preferably 2 μm or less, more preferably 1 μm or less. The drive part 9a thickness of the individual electrode 9 is 2 μm or less, preferably 1 μm or less, and the land part 9b is 15 μm or less, preferably 10 μm or less.
[0058]
The piezoelectric ceramic layer 7 includes, for example, a lead zirconate titanate compound (PbZrTiO).₃Perovskite crystal structure type piezoelectric materials (piezoelectric ceramics) such as lead compounds (PZT system)), lead titanate compounds, barium titanate compounds, etc. are preferably used. Of these, it is preferable to use the PZT system in that a large displacement can be obtained. The ceramic layers 13 and 15 can be made of the same material as the piezoelectric ceramic layer 7. Each of the piezoelectric ceramic layer 7 and the ceramic layers 13 and 15 may be composed of one layer or a plurality of layers.
[0059]
As the drive part 9a and the land part 9b of the individual electrode 9, it is preferable to use, for example, a metal such as Au, Ag, Cu, Cr, Pd, Pt, or an alloy containing at least one of these as a main component. In particular, it is more preferable to use Au in that high conductivity can be obtained even when layered.
[0060]
The common electrode 5 and the conductor layer 11 are preferably formed of the same material. As the common electrode 5 and the conductor layer 11, for example, a metal such as Au, Ag, Cu, Cr, Pd, or Pt or an alloy containing at least one of these as a main component is preferably used, which increases adhesion strength. In terms of this point, it is more preferable to add a small amount of the same material as the piezoelectric ceramic layer 7 (for example, a perovskite crystal structure type piezoelectric ceramic) to the Ag—Pd alloy.
[0061]
Next, a method for manufacturing the piezoelectric actuator 1 of the present invention will be described. 4A to 4D are schematic cross-sectional views showing the manufacturing process of the piezoelectric actuator 1.
[0062]
First, a piezoelectric ceramic powder whose main component is the aforementioned lead zirconate titanate compound, lead titanate compound, barium titanate compound or the like is prepared. The average particle size of the piezoelectric ceramic powder is preferably 1 μm or less, particularly 0.7 μm or less, more preferably 0.5 μm or less. By setting the average particle size of the piezoelectric ceramic powder to 1 μm or less, uniform firing shrinkage at the time of sintering can be obtained, and the homogeneous piezoelectric ceramic layer 7 and ceramic layers 13 and 15 can be obtained. This piezoelectric ceramic powder and an organic binder component are mixed to prepare a slurry for sheet forming. Next, a green sheet is produced by a general sheet forming method such as a roll coater method, a slit coater method, or a doctor blade method using this forming slurry (FIG. 4 (a): forming step).
[0063]
Next, the green sheet obtained in the molding process is pressurized (pressurizing process). A known method can be adopted as the pressurizing method, but a roll pressurizing method, a plane pressurizing method, a hydrostatic pressurizing method, etc. can be used for pressurization because it is easy to obtain a uniform thickness. . Thus, by performing the pressure treatment of the green sheet after forming the sheet, it is possible to increase the density of the sheet and reduce thickness variation and density variation.
[0064]
The pressurizing pressure varies depending on the material composition, the amount of the organic binder, the thickness of the green sheet, and the like, but it is preferable to pressurize at a pressure of 10 to 100 MPa, particularly 20 to 50 MPa, and further 30 to 40 MPa. Here, the thickness variation of each green sheet obtained by the pressurizing step is 5% or less, particularly 2% or less. The thickness variations of the piezoelectric ceramic layer 7 and the ceramic layers 13 and 15 formed after firing, and those It is easy to reduce the thickness variation of the piezoelectric actuator 1 formed by laminating and prevent warp deformation.
[0065]
Next, the metal pattern which becomes the common electrode 5 and the conductor layer 11 after baking is formed by screen printing on one surface of the green sheet obtained by the pressurization process using the conductor paste made of the electrode material described above. In this case, the thickness is desirably adjusted to 2 to 5 μm, and the thickness variation (difference between the maximum value and the minimum value of the thickness) is adjusted to 1 to 2 μm. FIG. 4B is a cross-sectional view showing a state in which a metal pattern to be the common electrode 5 after firing is formed on the green sheet.
[0066]
Next, the obtained green sheet is laminated | stacked by the structure shown, for example in FIG. 1, and it is made to contact | adhere, and a laminated molded object is obtained (FIG.4 (c): lamination | stacking process). In addition, as a method of performing adhesion, a method using an adhesion liquid containing an adhesive component, a method of adhering to an organic binder component in a green sheet by heating, a method of adhering only by pressing, etc. It can be illustrated (pressure process). As conditions for pressurization, for example, a temperature of about 60 to 100 ° C. and a pressure of about 3 to 10 MPa are suitable.
[0067]
The laminated molded body obtained in the laminating step is subjected to removal of organic components in the laminated molded body by a desired degreasing treatment, and then fired at 900 to 1200 ° C. in an oxygen atmosphere to produce a laminated sintered body. (Baking process). In the firing step for producing the laminated sintered body, the laminated molded body obtained in the laminating process is stacked in multiple stages via a sample base plate made of zirconia or magnesia, and this stacked laminated molded body is further stacked. It is desirable to place a weight on top and fire. By adopting the manufacturing method including such steps, the warp deformation of the piezoelectric actuator 1 is suppressed, and the piezoelectric actuator 1 made of a thin sintered body having a thickness of 100 μm or less can be provided.
[0068]
Next, the metal pattern which becomes the drive part 9a and the land part 9b of the individual electrode 14 is formed by screen printing on one surface of the laminated sintered body obtained in the firing step. In this case, it is desirable to adjust the thickness so that the thickness is 2 to 3 μm and the thickness variation (difference between the maximum value and the minimum value) is 0.5 to 1 μm. After printing this metal paste, the drive part 9a and the land part 9b are formed by performing a baking process at 600-800 degreeC (FIG.4 (d)). At this time, the printing conditions and the solid-liquid ratio of the metal paste can be adjusted so that the thickness of the drive portion 9a is 2 μm or less, preferably 1 μm or less, and the land portion 9b is 15 μm or less, preferably 10 μm or less. desirable.
[0069]
In particular, the land portion 9b eliminates bonding failure in the process of connecting a flexible wiring board that inputs a driving voltage signal by soldering or wire bonding, which will be described later, and does not hinder displacement of the piezoelectric actuator 1. It is necessary to make it somewhat higher than the height of the drive unit 9a. Therefore, for example, it is desirable to perform the printing and baking process of the metal paste a plurality of times to form the land portion 9b higher than the drive portion 9a.
[0070]
Next, an ink jet recording head provided with the piezoelectric actuator 1 of the present invention will be described. In the ink jet recording head shown in FIG. 1, the piezoelectric actuator 1 is placed on a flow path member 27 in which a plurality of ink flow paths 25 having ink discharge ports 24 are arranged. Are aligned and bonded by epoxy resin or the like. The flow path member 27 is configured by arranging a substrate 31 having an ink discharge port 24 on the lower surface of a partition wall 29 that forms the ink flow path 25.
[0071]
The flow path member 27 is made of a laminate composed of a plurality of metal foils having a thickness of about 30 to 100 μm. The ink flow path 25, the ink discharge ports 24, the partition walls 29, Substrate 31 and the like are formed respectively. Examples of the metal foil used include stainless steel foil, aluminum foil, and molybdenum foil. The channel member 27 can also be formed of silicon or the like.
[0072]
A flexible wiring substrate 33 is disposed on the piezoelectric actuator 1 and is connected to the land portion 9 b of the individual electrode 9 via the terminal electrode 21. Such an ink jet head includes the piezoelectric actuator 1 in which the warp deformation is corrected even if it is thin, so that variations in the ink discharge amount can be reduced.
[0073]
Note that the land-to-land recesses 9c and / or the individual-electrode recesses 17 as shown in FIG. 4E can be formed by various methods. The green sheets in which the recesses are formed may be laminated to form the recesses 9c between the land portions and / or the recesses 17 between the individual electrodes. In this case, the recesses 9c between the land portions and / or more easily. A recess 17 between the individual electrodes can be formed.
[0074]
Further, before the firing step, the inter-land concave portions 9c and / or the individual inter-electrode concave portions 17 are formed by pressing a mold or irradiating a laser beam to the green sheet to be the piezoelectric ceramic layer 7. May be. In this case, the green sheet used as the piezoelectric ceramic layer 7 has plasticity, and there is an advantage that workability is improved. In particular, when the land-to-land recesses 9c and / or the individual electrode-to-electrode recesses 17 are formed by a mold, the green sheet to be the piezoelectric ceramic layer 7 extruded by the mold is formed between the land-to-land recesses 9c and / or individual Since a convex part is formed around the concave part 17 between electrodes, it is more desirable.
[0075]
Moreover, you may form the metal pattern used as the recessed part 9c between land parts by screen printing with the drive part 9a of the individual electrode 14, and the land part 9b on one surface of the laminated sintered body obtained at the baking process.
[0076]
Further, even when the piezoelectric ceramic layer 7 of the laminated sintered body in which the drive portion 9 a and the land portion 9 b of the individual electrode 14 are formed is irradiated with laser light, the interelectrode recess 17 is formed in the piezoelectric ceramic layer 7. Good. At this time, the laser light may be irradiated under different conditions on the land-to-land recesses 9c in accordance with the purpose of further increasing the depth of the land-to-land recesses 9c or adjusting the shape.
[0077]
As mentioned above, although embodiment of this invention was shown, it cannot be overemphasized that this invention is applicable not only to embodiment mentioned above but what was changed and improved in the range which does not deviate from the summary of this invention.
[0078]
For example, in order to increase the volume of the land-to-land recess 9c, the land-to-land recess 9c may be disposed outside the individual electrode 9 as shown in FIG. May be formed by cutting out the piezoelectric ceramic layer 7.
[0079]
Further, for example, as shown in FIG. 3C, it goes without saying that there may be no protrusion 23 around the inter-land recess 9 c and the individual inter-electrode recess 17.
[0080]
Further, for example, the piezoelectric actuator 1 of the present invention includes, in addition to the above-described ink jet recording head, piezoelectric sensors such as an acceleration sensor, a knocking sensor, and an AE sensor, a fuel ejecting ink injector, a piezoelectric resonator, an oscillator, an ultrasonic motor, It can be applied to sound wave vibrators, filters, and the like.
[0081]
【Example】
First, PbZrTiO having an average particle size of 0.5 μm₃A slurry of a piezoelectric material was prepared by mixing a predetermined amount of a system powder, a binder, and an organic solvent that dissolves the binder, and a green sheet having a thickness of 25 μm was prepared using this slurry by a roll coater method. On the other hand, a predetermined amount of Ag—Pd (mixing ratio is Ag: pd = 7: 3) powder, organic binder and solvent was mixed to prepare a conductive paste.
[0082]
Next, a conductive paste was printed on the surface of the obtained green sheet by screen printing to form respective metal patterns to be the common electrode 5 and the conductor layer 11 after firing. Next, a predetermined total number of green sheets printed with conductive paste are laminated and heated and pressed to form a mother laminate, and this mother laminate is cut to form a laminate. Individual electrodes 9 as shown in FIG. The recesses that form the inter-individual electrode recesses 17 that surround the mold are adjusted so that the width and depth of the inter-electrode inter-electrode recesses 17 and the height of the inter-electrode protrusions are the dimensions shown in Table 1. The piezoelectric actuator 1 was formed by firing at 1000 ° C. for 2 hours in an oxygen atmosphere.
[0083]
Next, a metal paste containing Au as a main component is printed on one surface of the piezoelectric actuator 1 and baked at 730 ° C. to form individual electrodes 9, irradiated with excimer laser light, and inter-land recesses 9 c. In each sample, the width and depth of the land-to-land recess 9c were adjusted to the dimensions shown in Table 1 to produce a piezoelectric actuator 1 as shown in FIG. The thickness of the obtained piezoelectric actuator 1 was 20 μm, the thickness of the drive unit 9a and the land 9b was 1 μm, and the thickness of the common electrode 5 and the conductor layer 11 was 2 μm. The sample area was 30 mm × 30 mm. The interval between the individual electrodes 9 was 500 μm. In addition, 10 samples were prepared for each condition.
[0084]
Thereafter, a 3 kV / mm direct current electric field was applied between the common electrode 5 and the individual electrode 9 for 15 minutes to perform polarization treatment. The displacement amount of the piezoelectric actuator 1 is such that a DC voltage of 20 V is applied between the common electrode 5 and the individual electrode 9, and a sin waveform of 0 to +20 V is applied to the piezoelectric actuator 1 at room temperature at a frequency of 20 kHz. Apply 1 × 10⁹The average displacement amount when driving to the cycle is measured, and the displacement amount when the piezoelectric ceramic layer 7 below the adjacent individual electrode is driven, that is, when the adjacent eight piezoelectric ceramic layers 7 are simultaneously driven is measured. A value obtained by dividing the average displacement amount at this time by the average displacement amount at the time of single drive was defined as a displacement amount reduction rate, and the value is shown in Table 1.
[0085]
Further, the variation in the amount of drive displacement of each individual electrode 9 was measured and shown in Table 1. In addition, the ratio of the volume of the space formed by the concave and convex portions between the individual electrodes to the temporary volume of the terminal electrode 21 was calculated and shown in Table 1.
[0086]
Next, the flexible wiring substrate 33 was instantaneously heated at 300 ° C. above the land portion 9 b of the individual electrode 9 to connect the terminal electrode 21 of the flexible wiring substrate 33 and the land portion 9 b of the individual electrode 9.
[0087]
Table 1 shows the result of the connection failure rate between the terminal electrode 21 of the flexible wiring board 33 and the land portion 9b of the individual electrode 9 at this time. The connection failure rate is obtained by dividing the number of individual electrodes formed in one sample by the total number of individual electrodes.
[0088]
In addition, sample No. outside the scope of the present invention. No. 1 was irradiated with an excimer laser beam, except that the inter-land recess 9c and the individual inter-electrode recess 17 were not formed. The piezoelectric actuator 1 was produced in the same manner as in Nos. 2 to 28 and evaluated in the same manner. The results are shown in Table 1.
[0089]
[Table 1]

[0090]
From Table 1, the sample No. 1 having no inter-land recess 9c and individual inter-electrode recess 17 outside the scope of the present invention was obtained. For No. 1, the drive displacement variation was 20%, the displacement decrease rate was 32%, and the connection failure rate was 50%. This connection failure rate is very high, and is a level at which almost no good products can be produced.
[0091]
On the other hand, the sample No. in the range of the present invention in which only the recess 9c between the land portions is provided. In No. 2, the drive displacement variation was 12%, the displacement reduction rate was 15%, and the connection failure rate was 7%. Sample No. Compared with 1, improvement can be seen in all items, but the connection failure rate is particularly improved.
[0092]
In addition, the sample No. provided with the recesses 17 between the individual electrodes was used. For No. 3, the variation in drive displacement amount was 17%, the displacement amount reduction rate was 17%, and the connection failure rate was 2%. Furthermore, the sample No. 1 provided with the recesses 17 between the individual electrodes and the projections 23 is provided. In No. 4, the drive displacement variation was 17%, the displacement decrease rate was 14%, and the connection failure rate was 1%. By providing the recesses 17 between the individual electrodes, the connection failure rate was remarkably reduced.
[0093]
In addition, the sample No. 1 including the inter-land recess 9c, the individual inter-electrode recess 17 and the protrusion 23 is provided. In 5 to 28, the drive displacement variation was 13% or less, the displacement decrease rate was 20% or less, and the connection failure rate was 1% or less.
[0094]
【The invention's effect】
The present inventionPiezoelectric actuatorAccording toA common electrode, a piezoelectric ceramic layer, and an individual electrode are laminated in this order on the diaphragm, and the individual electrode contributes to piezoelectric driving and a land portion for applying a driving voltage connected to one end of the driving unit. And a plurality of piezoelectric actuators arranged on the surface of the piezoelectric ceramic layer, wherein the piezoelectric actuator is connected to the land portion of the main surface on which the individual electrodes of the piezoelectric ceramic layer are provided. The piezoelectric ceramic layer is cut out at a position between one end of the drive unit and the other part of the drive unit to form a recess between land portions, or the individual electrode of the piezoelectric ceramic layer is provided. A recess between the individual electrodes is formed by cutting out the piezoelectric ceramic layer between the individual electrodes on the surface.Therefore, even if the terminal electrode formed on the land part melts and flows out from the land part, the concave part between the land partsOr recess between individual electrodesCan stop the flow, MeltIt can suppress that the fuse | melted metal contacts with the adjacent separate electrode and is electrically short-circuited.Moreover, the influence which the vibration of the piezoelectric ceramic layer just under a drive part has on an adjacent drive part can be suppressed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an ink jet recording head including a piezoelectric actuator according to an embodiment of the present invention.
FIG. 2 is a plan view showing a formation state of a land-to-land recess and an individual-electrode recess in the piezoelectric actuator of the present invention.
FIG. 3 is a cross-sectional view showing the shape of a recess between individual electrodes.
FIGS. 4A to 4D are cross-sectional views showing a manufacturing process of a piezoelectric actuator according to the present invention. FIGS.
FIG. 5 is a plan view showing a formation state of a land-to-land recess according to another embodiment of the present invention in which a land-to-land recess is provided outside an individual electrode in the piezoelectric actuator of the present invention.
FIG. 6 is a cross-sectional view showing an ink jet recording head provided with a conventional piezoelectric actuator.
FIG. 7 is a plan view showing a conventional piezoelectric actuator.
[Explanation of symbols]
1 ... Piezoelectric actuator
3 ... Diaphragm
5 ... Common electrode
7 ... Piezoceramic layer
9 ... Individual electrode
9a ... Drive unit
9b ... Land
9c: Land-to-land recess
11: Conductor layer
13, 15 ... Ceramic layer
17: Recesses between individual electrodes
21 ... Terminal electrode
23 ... convex part
24: Ink discharge port
25 ... Ink flow path
27 ... Channel member

Claims (15)

  A common electrode, a piezoelectric ceramic layer, and an individual electrode are stacked in this order on the diaphragm, and the individual electrode contributes to piezoelectric driving and a land portion for applying a driving voltage connected to one end of the driving unit. And a plurality of piezoelectric actuators arranged on the surface of the piezoelectric ceramic layer, wherein the piezoelectric actuator is connected to the land portion of the main surface on which the individual electrodes of the piezoelectric ceramic layer are provided. A piezoelectric actuator characterized in that a recess between land portions is formed by notching the piezoelectric ceramic layer at a position between one end of the drive portion and another portion of the drive portion.   A common electrode, a piezoelectric ceramic layer, and an individual electrode are stacked in this order on the diaphragm, and the individual electrode contributes to piezoelectric driving and a land portion for applying a driving voltage connected to one end of the driving unit. And a plurality of piezoelectric actuators arranged on the surface of the piezoelectric ceramic layer, wherein the piezoelectric ceramic layer is disposed between the individual electrodes on a main surface of the piezoelectric ceramic layer on which the individual electrodes are provided. A piezoelectric actuator characterized in that a recess between the individual electrodes is formed by cutting out the electrode.   3. The piezoelectric actuator according to claim 2, wherein a second inter-land concave portion is formed by notching the driving portion in the driving portion between the land portions of the individual electrodes.   4. The piezoelectric actuator according to claim 3, wherein the recess between the second land portions does not penetrate the drive unit. 5.   5. The piezoelectric actuator according to claim 3, wherein the recess between the second land portions is formed on an outer peripheral portion of the driving portion on a side to which the land portion is connected. The piezoelectric actuator according to any one of claims 2 to 5, characterized in that the individual electrodes between wells is formed surrounding the individual electrodes. The piezoelectric actuator according to any one of claims 2 to 6, characterized in that at least two of the individual inter-electrode recess is formed between adjacent said individual electrodes. The piezoelectric actuator according to any one of claims 2 to 7 , wherein the maximum depth of the recesses between the individual electrodes is 3 µm or more. The piezoelectric actuator according to any one of claims 2 to 8 , wherein the maximum depth of the recesses between the individual electrodes is 30% or more of the thickness of the piezoelectric ceramic layer. The piezoelectric actuator according to any one of claims 2 to 9, wherein a convex portion is formed around the individual electrodes between wells. The piezoelectric actuator according to claim 1 0, wherein the height of the convex portion is 3μm or more. The piezoelectric actuator according to claim 1 0 or 1 1 height difference of the individual electrode between the recess and the protrusion is equal to or is 6μm or more. The piezoelectric actuator according to any one of claims 2 to 1 2 the maximum width of the individual electrode between the recesses, characterized in that at 20μm or more. The volume between the recesses between the individual electrodes corresponding to the individual electrodes or the space formed by the recesses between the individual electrodes and the projections is the cube of the diameter or diagonal distance of the land part. the piezoelectric actuator according to any one of claims 2 to 1 3, characterized in that 8 to 30% of the temporary terminal electrode volume sought. The piezoelectric actuator according to any one of claims 1 to 1 4, on the flow path member having a plurality of ink passages having ink discharge ports are arranged, aligned positions of the individual electrodes and the ink flow path An ink jet recording head characterized by being attached.

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