JP2014177099A - Piezoelectric actuator, piezoelectric actuator manufacturing method, droplet discharge head, and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric actuator capable of having sufficient stiffness and increasing displacement magnitude while suppressing drive power, with small size and low cost.SOLUTION: Multiple piezoelectric walls 8 and electrodes 3 are alternately disposed in a surface direction, the piezoelectric walls 8 formed to be sandwiched between grooves 7 provided in a piezoelectric thin layer 2 formed on a diaphragm 1, the electrodes 3 disposed to be buried in the grooves sandwiching the piezoelectric walls. Voltage is applied to the electrodes to generate displacement generated in each of the piezoelectric walls 8 to deform the thin layer in the surface direction, so that the diaphragm integrally provided to the thin layer is deflected.

Description

  The present invention relates to a piezoelectric actuator, a method for manufacturing the piezoelectric actuator, a droplet discharge head that discharges droplets using the piezoelectric actuator, and an image forming apparatus that employs the droplet discharge head.

  In general, a printer, a fax machine, a copier, a plotter, or an image forming apparatus that combines a plurality of these functions includes, for example, a droplet discharge head that discharges ink droplets (hereinafter referred to as ink droplets). Inkjet recording apparatus. In an ink jet recording apparatus, an image is formed by adhering ink droplets to a sheet by a droplet discharge head while conveying a medium. The medium here is also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, a recording paper, and the like are also used synonymously. Further, the ink jet recording apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics or the like. The image formation is not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium (simply ejecting a droplet). Also means. The ink is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected. For example, the ink is a generic term for liquids including DNA samples, resists, pattern materials, and the like. Use.

  In the liquid droplet ejection head, a piezoelectric actuator composed of a diaphragm and a piezoelectric element is provided in a liquid chamber communicating with the nozzle, and a pressure fluctuation is generated in the liquid chamber by a piezoelectric actuator, thereby ejecting liquid droplets from the nozzle. Are known. As a piezoelectric actuator, a piezoelectric element having a laminated structure in which a plurality of piezoelectric bodies and electrodes are alternately stacked is provided on a diaphragm, an electric field is applied in a direction perpendicular to the diaphragm, and a direction parallel to the electric field (d33 (Direction) is directly transmitted to the diaphragm to displace the diaphragm. In addition, a piezoelectric element made of a piezoelectric body sandwiched between two electrodes is provided on the diaphragm, an electric field is applied in a direction perpendicular to the diaphragm, and vibration is caused by deformation in a direction perpendicular to the electric field (d31 direction). A unimorph structure that bends the plate has been put into practical use.

  In Patent Document 1, a liquid droplet ejection head in which a piezoelectric actuator having a unimorph structure composed of a diaphragm and a piezoelectric thin film sandwiched between two electrodes is directly formed on a Si substrate forming a partition of a liquid chamber. Is described. Such a droplet discharge head has been evaluated to be small in size and low in cost, and in recent years, the number of examples employed in products is increasing.

  In recent years, high integration of a droplet discharge head has been demanded from the demand for high image quality and high speed of an ink jet recording apparatus. As a method of high integration, there are a method of increasing the integration degree in one row, while a method of increasing the integration degree in one row is a method of increasing the apparent integration degree by arranging in multiple rows, although the integration degree in one row is not different from the conventional one. The method of increasing the apparent degree of integration in multiple rows increases the area of the piezoelectric actuator compared to the method of increasing the degree of integration in one row. In the method of forming a plurality of piezoelectric actuators on a single Si substrate by MEMS (Micro Electro Mechanical Systems) technology and separating them into individual actuators, the number of piezoelectric actuators that can be made from a single Si substrate is reduced. . For this reason, a droplet discharge head having an apparent degree of integration in multiple rows is expensive, and a method of increasing the degree of integration in one row is preferable for reducing the cost.

  In order to increase the integration degree in one row, it is necessary to arrange the liquid chambers at a high density, and it is necessary to make the width in the arrangement direction small. However, in a droplet discharge head using a piezoelectric actuator having a unimorph structure utilizing deformation in the d31 direction, if the width of the liquid chamber is reduced, the displacement amount of the piezoelectric actuator is also reduced, resulting in a deterioration in discharge characteristics.

Patent Document 2 discloses an annular upper electrode disposed on an edge other than the central portion of the surface of the piezoelectric layer, a lower electrode disposed on the lower surface of the piezoelectric layer, and a central portion of the piezoelectric layer from the lower electrode. A piezoelectric actuator having a unimorph structure having a column portion penetrating through a central electrode and a central electrode having a surface portion spaced apart from an upper electrode is described.
Patent Document 3 describes a unimorph-structured piezoelectric actuator in which at least one planar shape of a lower electrode, a piezoelectric body, and an upper electrode is arranged in a comb shape.

  In order to increase the displacement amount of the piezoelectric actuator in the unimorph liquid droplet ejection head, a method of thinning the diaphragm can be considered. However, if the diaphragm is made thin, the rigidity of the diaphragm is lowered and ejection characteristics are deteriorated, resulting in problems such as a response frequency being lowered and ink having high viscosity cannot be ejected. Although a method of increasing the drive voltage is also conceivable, there is a problem that power consumption increases.

In the piezoelectric actuator of Patent Document 2, the displacement amount of the diaphragm is increased by the electric field generated between the center electrode and the upper electrode in addition to the electric field generated between the lower electrode and the upper electrode. However, this electric field is formed only on the surface layer portion of the piezoelectric layer, and a significant increase in the amount of displacement cannot be expected.
In the piezoelectric actuator of Patent Document 3, at least one planar shape among the lower electrode, the piezoelectric body, and the upper electrode is arranged in a comb shape, thereby reducing the rigidity in the liquid chamber width direction and increasing the amount of displacement. However, since the rigidity of the actuator becomes low, it is undeniable that a problem due to insufficient rigidity occurs as in the case where the rigidity of the diaphragm described above is lowered.
Thus, it is difficult for the conventional unimorph-structured piezoelectric actuator to ensure rigidity and suppress the drive voltage while increasing the amount of displacement.

  The present invention has been made in view of the above-described problems, and a purpose thereof is a compact and low-cost piezoelectric actuator capable of increasing rigidity while ensuring rigidity and suppressing driving power, and a method for manufacturing the piezoelectric actuator. And a droplet discharge head and an image forming apparatus.

  In order to achieve the above object, the invention of claim 1 is characterized in that a first layer portion in which a plurality of piezoelectric bodies and electrodes are alternately arranged in a surface direction and the first layer portion in the thickness direction so as to extend over the surface direction. And a second layer portion formed integrally with the layer portion, and the first layer portion is deformed in the surface direction by applying a voltage to the electrode of the first layer portion, and both layers are bent. This is a piezoelectric actuator.

  In the present invention, by applying a voltage to the electrode of the first layer portion, the individual piezoelectric bodies sandwiched between the electrodes are displaced, so that the entire first layer portion is deformed in the surface direction. Due to the deformation in the surface direction of the first layer portion, a new piezoelectric actuator in which both the first layer portion and the second layer portion integrally formed with the first layer portion in the thickness direction are bent. In this configuration, by providing the piezoelectric body and the electrodes of the first layer portion so as to increase the number of piezoelectric bodies sandwiched between the electrodes, the deformation in the surface direction of the entire first layer portion is increased, and the deflection of the whole of both layers is increased. The amount can be increased. For this reason, the amount of displacement can be increased without lowering the rigidity of the actuator itself or increasing the drive voltage as in a conventional unimorph piezoelectric actuator.

  According to the present invention, there is an excellent effect that it is possible to provide a small-sized and low-cost piezoelectric actuator that can ensure rigidity and increase the amount of displacement while suppressing drive power.

It is a schematic diagram of the piezoelectric actuator of an embodiment, (a) is a top view, (b) is a sectional view, (c) is an expanded sectional view. Explanatory drawing of an example of the manufacturing process of the piezoelectric actuator of FIG. The schematic diagram showing the cross section of the piezoelectric actuator of the other example of this embodiment. The schematic diagram showing the cross section of the piezoelectric actuator of the other example of this embodiment. The schematic diagram showing the cross section of the piezoelectric actuator of the other example of this embodiment. The schematic diagram showing the cross section of the piezoelectric actuator of the other example of this embodiment. The schematic diagram showing the upper surface of the piezoelectric actuator of the other example of this embodiment. The schematic diagram showing the upper surface of the piezoelectric actuator of the other example of this embodiment. The schematic diagram showing the upper surface of the piezoelectric actuator of the other example of this embodiment. FIG. 3 is a top view of a piezoelectric actuator in the droplet discharge head according to the present embodiment. It is sectional drawing of the piezoelectric actuator of FIG. 10, (a) is a liquid chamber row direction sectional view, (b) is a liquid chamber length direction sectional view. FIG. 12 is a cross-sectional view in which a support substrate is bonded onto the actuator substrate of FIG. 11, (a) is a liquid chamber arrangement direction AA cross-sectional view, and (b) is a liquid chamber length direction BB cross-sectional view. 1 is an overall perspective view of a droplet discharge head according to an embodiment. 1 is an overall cross-sectional view of a droplet discharge head according to an embodiment. Sectional drawing of the liquid chamber length direction of the droplet discharge head of this embodiment. The schematic diagram which used the IJP method as a manufacturing method of the piezoelectric actuator of this embodiment. An example of the drive waveform which drives the piezoelectric actuator of this embodiment. Explanatory drawing for preloading the piezoelectric actuator at the time of droplet discharge. The schematic diagram which used the MEMS technique as a manufacturing method of the piezoelectric actuator of this embodiment. 1 is a schematic diagram of a line-type inkjet printer equipped with a droplet discharge head according to an embodiment. (A), (b) The schematic diagram showing the cross section of the piezoelectric element of a unimorph structure.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating the piezoelectric actuator of the present embodiment, where (a) is a top view, (b) is a cross-sectional view, and (c) is an enlarged cross-sectional view. The piezoelectric actuator 37 in FIG. 1 is a piezoelectric actuator configured by a first layer portion in which a plurality of piezoelectric walls 8 and electrodes 3 are alternately arranged in a plane direction, and a second layer portion made of the diaphragm 1. .

FIG. 2 is an explanatory diagram of an example of a manufacturing process of the piezoelectric actuator of FIG.
The piezoelectric actuator 37 forms a piezoelectric thin film 2 represented by a piezo on one surface of a diaphragm 1 made of a metal plate, a silicon substrate, a glass plate, or the like (FIG. 2A). The piezoelectric thin film 2 is laminated on the vibration plate 1 by a film forming technique such as adhesion or sputtering. The diaphragm 1 is preferably formed of a material having a relatively high Young's modulus such as SiO ₂ , SiN, PS (polysilicon), or SiON. However, since the vibration plate 1 has a thickness of about several μm or less, the vibration plate 1 is formed on a substrate such as the liquid chamber substrate 15 of the droplet discharge head as described later, and the substrate of the active portion of the piezoelectric thin film 2 is formed. To be left as the partition wall 19 (see FIG. 2 (e)).

The grooves 7 are formed at a predetermined pitch in the piezoelectric thin film 2 by an edging method using photolithography (hereinafter referred to as a photolithography method) or the like, thereby forming the remaining piezoelectric wall 8 (FIG. 2). (B)). The electrode 3 is embedded in the groove 7 with Ti, SRO, Pt, Al, or a combination thereof (FIG. 2C), and then the surface of the piezoelectric thin film 2 is made of SiN, SiO ₂ , SiN, SiO ₂ or the like. A protective film 4 is formed (FIG. 2D).

  As shown in FIG. 1A, the electrode 3 is formed as a comb-like electrode whose polarity is alternately changed. The electrodes 3 having the same polarity are connected to the first electrode 5 or the second electrode 6, respectively, and the first electrode 5 and the second electrode 6 are connected to the power source 12. With such a configuration, an electric field can be formed on the wall 8 of the piezoelectric body sandwiched between the electrodes 3. Here, the electrode 3 of the groove 7 for applying an electric field to the wall 8 of the piezoelectric body is formed of Ti, SRO, Pt, and the first electrode 5 and the second electrode 6 used as the conductor are formed of Al. Is advantageous in terms of cost.

  In this piezoelectric actuator 37, by applying a voltage to the electrodes 3 on both sides of the walls 8 of the plurality of piezoelectric bodies, an electric field is formed in the direction parallel to the diaphragm 1 on the walls 8 of the plurality of piezoelectric bodies. Displacement (extension) in the direction parallel to the direction of the electric field (direction d33) occurs on the body wall 8 respectively. FIG.1 (c) is an expanded sectional view for demonstrating the displacement (elongation) of the wall 8 of a piezoelectric material. When such a displacement (elongation) is generated in the wall 8 of each piezoelectric body, as a whole, a displacement force that is a combination of the displacements (elongation) generated in the plurality of walls 8 is shown in the arc of FIG. The diaphragm 1 is bent. For this reason, the bending amount of the diaphragm 1 can be increased by forming the grooves 7 so as to increase the number of the walls 8 of the piezoelectric body. Further, since the displacement in the d33 direction, which can obtain a large amount of displacement compared to the d31 direction, is converted into the bending of the diaphragm, a strong displacement force can be obtained.

  The drawing schematically shows the arrangement of the piezoelectric wall 8 and the electrode 3, and the width of the electrode 3 and the width of the dielectric wall 8 in the present invention are not necessarily shown in the drawing. In the known technique, a groove 7 having a width and interval of 1 [μm] to submicron is formed in the piezoelectric thin layer 2, and an electrode 3 having a width of 1 [μm] to submicron is embedded in the groove 7. Is possible. Thus, as in a specific example described later, the piezoelectric body wall 8 having an arbitrary width of 1 [μm] to submicron and the electrode 3 having an arbitrary width of 1 [μm] to submicron are configured. Can do.

More specific description will be given below.
First, a unimorph piezoelectric actuator will be described as a comparative example. FIG. 21A is a sectional view of a piezoelectric actuator 137 having a conventional unimorph structure. A conventional piezoelectric actuator 137 having a unimorph structure has a piezoelectric element in which a lower electrode 102, a piezoelectric thin film 2, and an upper electrode 103 are sequentially laminated on a vibration plate 1. In this unimorph piezoelectric actuator 137, by applying a voltage to the lower electrode 102 or the upper electrode 103, an electric field in the direction perpendicular to the diaphragm 1 is formed in the piezoelectric thin film 2, and in the d31 direction perpendicular to the electric field direction. Displacement (shrinkage) occurs. Utilizing this, the diaphragm 1 is bent so as to be bent into the arc of FIG.

Here, when the width of the piezoelectric thin film 2 is L, the thickness is t, and the applied voltage is V, the displacement amount ΔL ₃₁ of the piezoelectric thin film 2 itself is ΔL ₃₁ = L × d ₃₁ × V / T (d31 is (Proportional coefficient in the d31 direction of the piezoelectric body). For example, when L = 60 [μm], t = 20 [μm], V = 30 [V] and d ₃₁ = −200 [pm / m], the piezoelectric thin film 2 itself has ΔL ₃₁ = −1.8. × 10 ⁻⁷ [m] Shrink.

On the other hand, in the piezoelectric actuator of FIG. 1, the displacement amount ΔL ₃₃ generated in the wall 8 of one piezoelectric body is expressed by ΔL ₃₃ = d ₃₃ × V (d33 is a proportional coefficient in the d33 direction of the piezoelectric body). For example, when the width Lk of the wall 8 is 2 [μm], when d ₃₃ = 400 [pm / m], the wall 8 of the piezoelectric body itself extends by ΔL ₃₃ = 1.2 × 10 ⁻⁸ [m]. Become. Assuming that the width We of the electrode 3 is 0 and the piezoelectric thin film 2 of L = 60 [μm] in which the wall 8 of the piezoelectric body of Lk = 2 [μm] is overlapped in the width direction is 60 ÷ 2 = 30, There will be 30 piezoelectric walls 8. ΔL _{33 of the} entire piezoelectric thin film 2 = displacement amount ΔL ₃₃ × (number of walls 8 of the piezoelectric body) generated in one piezoelectric body wall 8, and ΔL _{33 of the} entire piezoelectric thin film 2 = 1.2 × 10 An elongation of ⁻⁸ × 30 = 3.6 × 10 ⁻⁷ [m] is obtained. Taking the ratio of ΔL ₃₁ and ΔL ₃₃ as the piezoelectric thin film 2 of L = 60 [μm], ΔL ₃₁ / ΔL ₃₃ = (− 1.8 × 10 ⁻⁷ ) / (3.6 × 10 ⁻⁷ = This corresponds to a ratio of d ₃₁ = −200 [pm / m] and d ₃₃ = 400 [pm / m].

In the actual piezoelectric actuator of FIG. 1, the electrode 3 has a width We. When the groove 7 is formed in the piezoelectric thin film 2 with L = 60 [μm] so that the width Lk of the wall 8 is 2 [μm] and the electrode width We = 2 [μm], the number of walls 8 is fifteen. Become. At this time, ΔL ₃₃ = 1.2 × 10 ⁻⁸ × 15 = 1.8 × 10 ⁻⁷ [m] as the piezoelectric thin film 2 is obtained, and the displacement is the same as ΔL ₃₁ . If the grooves 7 are formed so that the width Lk = 1 [μm] of the wall 8 of the piezoelectric body and the width We = 1 [μm] of the electrode, the number of the walls 8 is 30. At this time, ΔL ₃₃ = 1.2 × 10 ⁻⁸ × 30 = 3.6 × 10 ⁻⁷ [m] as the piezoelectric thin film 2 is obtained, which is a displacement amount twice as large as ΔL ₃₁ . As described above, in this embodiment, the groove 7 is formed so as to increase the number of the walls 8 of the piezoelectric body and the electrode 3 is provided, so that the displacement amount of the piezoelectric thin film 2 as a whole is increased and vibration is generated. The amount of bending of the plate 1 can be increased.

  FIG. 3 is a schematic diagram showing a cross section of another example of the piezoelectric actuator of the present embodiment. The shape of the groove formed in the piezoelectric thin film 2 is preferably formed with an inclination angle 9 that becomes narrower toward the bottom. Thereby, embedding of the electrode 3 can be made easy. The inclination angle 9 is preferably 45 degrees or greater and 90 degrees or less. Moreover, by having such an inclination angle 9, the force due to the displacement is efficiently transmitted in the thickness direction of the wall 8 of the piezoelectric body.

FIG. 4 is a schematic diagram showing a cross section of another example of the piezoelectric actuator of the present embodiment. When the electrode 3 is formed by sputtering or the like, the upper portion of the groove 7 may be concave as shown in FIG. In such a case, it is preferable that the insulator 11 such as SiO ₂ is formed so as to fill the concave portion, and the planarity is improved by a flattening process or the like. When the flatness is good, it becomes easy to set a gap at the time of joining to the support substrate 21 when a droplet discharge head described later is formed. Conversely, when the electrode 3 is formed above the piezoelectric thin film 2, at least the electrode 3 above the piezoelectric wall 8 needs to be removed by etching or the like. Adjacent electrodes 3 need to maintain insulation. For this reason, after the electrode 3 is formed, it is important to secure a certain edge distance by removing the electrode 3 protruding from the groove 7 by etching or performing a flattening process as described above. Thereby, the reliability and yield of the piezoelectric actuator 37 can be improved.

FIG. 6 is a schematic diagram showing a cross section of another example of the piezoelectric actuator of the present embodiment. In this piezoelectric actuator, a piezoelectric body is left below the piezoelectric thin layer 2 and a plurality of grooves 7 are provided on the top, and the diaphragm 1 is not provided.
In the piezoelectric actuator of FIG. 6, the piezoelectric body is left below the piezoelectric thin layer 2, a plurality of grooves 7 are provided on the top, and the piezoelectric wall 8 sandwiched between the grooves 7 on the piezoelectric thin layer 2. A plurality of are formed. A voltage is applied to the electrodes 3 embedded in the grooves 7 on both sides of the wall 8. In this configuration, the lower portion 2 a of the piezoelectric thin layer 2 in which the groove 7 is not formed is almost an inactive region and has the function of the diaphragm 1. For this reason, as shown in FIG. 6, it is possible to use the lower portion 2 a of the piezoelectric thin layer 2 in which the groove 7 is not formed instead of the diaphragm 1 without providing the diaphragm 1. That is, in the piezoelectric actuator 37, the upper part of the piezoelectric thin film 2 is a first layer part, and the lower part 2a of the piezoelectric thin layer 2 is a second layer part. In this configuration, the lower portion 2a of the piezoelectric thin layer 2 and the wall 8 of the piezoelectric thin film are integrally formed, so that strength can be ensured. Furthermore, since the diaphragm manufacturing process can be omitted, the cost can be reduced.

  Further, as shown in FIG. 5, the piezoelectric body may be left in the lower portion 2 a of the piezoelectric thin layer 2 on the vibration plate 1 and a plurality of grooves 7 may be provided in the upper portion. In the piezoelectric actuator 37, the lower portion 2 a of the piezoelectric thin layer 2 in which the upper portion of the piezoelectric thin film 2 becomes the first layer portion and the intermediate layer portion and the vibration plate 1 constitute the second layer portion of the present invention. In the piezoelectric actuator of FIG. 5, by providing the groove 7 having the above-described shape, an effect of increasing the degree of freedom by adjusting the rigidity of the intermediate layer portion and adjusting the warp due to the residual stress due to heat at the time of forming the piezoelectric thin film 2 is achieved. Is obtained.

  7, 8, and 9 are schematic views showing the upper surface of another example of the piezoelectric actuator of the present embodiment. In FIGS. 7, 8, and 9, the protective film 4 is omitted. The electrode 3 in the piezoelectric actuator of this embodiment is not necessarily linear. For example, it may have an arc shape as shown in FIG. 7 or a wave shape as shown in FIG. Even if the shape of the actuator is atypical (ellipse, parallelogram, etc.), a high output piezoelectric actuator 37 with good area efficiency of the electrode 3 can be constructed by combining curves and straight lines. For example, in FIG. 9, in order to take out the 1st electrode 5 and the 2nd electrode 6 from an elliptical actuator, the lead-out lines 5a and 6a are formed in the right and left from the center part. The electrodes 3 having the same polarity as the lead wires 5a and 6a are connected to each other, and the electrodes 3 having different polarities are insulated from each other by the piezoelectric thin film 2 in which the grooves 7 are not formed. 7 and 8, the displacement direction of the wall 8 of the piezoelectric body is mainly the short side direction of the ellipse, but in the configuration of FIG. 9, it has an electrode shape that is displaced over the entire circumference. As described above, by arranging the electrodes 3 efficiently, the piezoelectric actuator 37 having a large displacement can be produced. Further, the electrode 3 can be taken out on both sides, which is a practical wiring.

  Next, a droplet discharge head 40 that employs the piezoelectric actuator 37 of the present embodiment will be described with reference to the drawings. FIG. 10 is a top view of the piezoelectric actuator in the liquid droplet ejection head of this embodiment. In addition, although the piezoelectric actuator 37 of the droplet discharge head 40 is configured symmetrically, only the right half of the piezoelectric actuator 37 is shown in FIG. FIG. 11A is a sectional view of the piezoelectric actuators in the liquid droplet ejection head according to the present embodiment, which is a sectional view taken along the line AA in FIG. FIG. 12B is a cross-sectional view in the liquid chamber length direction of the piezoelectric actuator in the liquid droplet ejection head of the present embodiment, and shows a cross-sectional view taken along line BB in FIG.

  As shown in FIGS. 11A and 11B, the droplet discharge head has one wall surface of the liquid chamber 18 on one side of the liquid chamber substrate 15 made of an Si substrate that forms the side wall portion of the individual liquid chamber 18. And a piezoelectric thin film 2 formed on the vibration plate 1 by sputtering, Solgel method, or the like. The piezoelectric thin film 2 is formed with a plurality of grooves 7, and the electrodes 3 are embedded in the grooves 7 by sputtering or the like to form a piezoelectric actuator 37. A nozzle plate 16 having nozzles is joined to the opposite side of the liquid chamber substrate 15 to the diaphragm 1 to form each liquid chamber 18 communicating with the nozzles.

  Wiring of the piezoelectric actuator 37 will be described with reference to FIG. The piezoelectric actuator 37 is disposed above each liquid chamber (not shown in FIG. 10) 18. The first electrode 5 of each piezoelectric actuator 37 is wired as an individual electrode, and the second electrode 6 is wired as a common electrode with other piezoelectric actuators 37. The first electrode 5 which is an individual electrode in each liquid chamber 18 is provided with bumps 14 formed of solder or gold for connecting the driving IC 23. The protective film 4, which is a part of the piezoelectric actuator 37, is removed from the projection portion of the liquid chamber 18 and the liquid inlet 13 together with the vibration plate 1 by etching or the like. In FIG. 10, C and D parts indicate notches and represent the lower part of the protective film 4.

  In the piezoelectric actuator 37 of the present embodiment, the first electrode (individual electrode) 5 and the second electrode (common electrode) are not configured to sandwich the piezoelectric thin film 2 in the vertical direction, and therefore the first electrode (individually) An electrode) 5 and a second electrode (common electrode) can be formed. This eliminates the need for an interlayer insulating film necessary for a conventional unimorph piezoelectric actuator in which the piezoelectric thin film 2 is sandwiched between upper and lower electrodes and a wiring member for connecting to the electrode through the interlayer insulating film. The process can be greatly simplified.

  As shown in the AA sectional view of FIG. 11A, the protective film 4 of the projection portion of the liquid chamber 18 is removed and formed on the piezoelectric body 2 corresponding to the partition wall 19 dividing each liquid chamber. The protective film 4 remains. In addition, as shown in the BB cross-sectional view of FIG. 11B, the liquid inlet 13 communicates with the liquid chamber 18 through the fluid resistance 20.

  12A and 12B are cross-sectional views of the actuator substrate 38, FIG. 12A is a cross-sectional view in the liquid chamber arrangement direction, and FIG. 12B is a cross-sectional view in the liquid chamber width direction. A substrate obtained by bonding the support substrate 21 to the liquid chamber substrate 15 on which the piezoelectric actuator 37 shown in FIGS. 11A and 11B is formed is referred to as an actuator substrate 38. A liquid supply port 22 communicating with the liquid introduction port 13 is formed in the support substrate 21. The support substrate 21 is bonded to the protective film 4 and has a gap corresponding to the thickness of the protective film 4 from the electrode 3. Although not shown, a thin insulating film is formed on the entire surface below the protective film 4, and the insulating film is removed from the upper and peripheral portions of the bumps 14 and the openings of the liquid inlets 13. May be configured with the insulating film left.

  Conventionally, when the support substrate 21 is bonded onto the liquid chamber substrate 15 on which the piezoelectric actuator is formed, as described in Japanese Patent No. 3690098, a backing having a partition wall that divides each piezoelectric element so as not to contact the piezoelectric element A method of adhering materials is used. When a highly integrated head of 300 dpi / row or more is required, parts accuracy and assembly accuracy are required, resulting in high costs and, in some cases, manufacture becomes difficult. In the liquid droplet ejection head of this embodiment, as shown in FIGS. 12A and 12B, a support substrate 21 is bonded to the protective film 4 formed on the piezoelectric thin film 2. For this reason, it is not necessary to provide a special high-accuracy adhesive portion on the support substrate 21, and there is no need for processing and parts for special adhesion to the piezoelectric actuator 37 side, and the protective film 4 that enhances the insulation of the electrode 3 is used. Just do it. As for the assembly accuracy, it is only necessary to align the liquid supply port 22 of the support substrate 21 and the liquid introduction port 13 of the liquid chamber substrate 15, and the assemblability is remarkably improved.

  FIG. 13 is an exploded perspective view of the droplet discharge head according to the present embodiment, and FIG. 14 is an assembled perspective view of the droplet discharge head according to the present embodiment. The droplet discharge head 40 includes a nozzle cover 39, a nozzle plate 16, an actuator substrate 38, a backing plate 26, a damper plate 29, a housing 31, and the like. In addition, an FPC (Flexible Printed Circuits) 41 that transmits an electrical signal from the control unit of the ink jet recording apparatus to the actuator substrate 38 in accordance with the recorded image is provided. In FIG. 13, the liquid chamber width direction and the liquid chamber arrangement direction of the droplet discharge head 40 are shown.

  FIG. 15 is a sectional view of the entire droplet discharge head 40. Note that the FPC 41 is not shown in FIG. A space 24 in which the drive IC 23 is disposed is formed at the center of the support substrate 21 bonded to the liquid chamber substrate 15. A stud bump (not shown) made of gold is formed on the bump 14 formed on the first electrode 5 of the piezoelectric actuator 37 at a position corresponding to the space 24, and the drive IC 23 is flip-chip bonded. For example, a first backing plate 25 and a second backing plate 26, which are SUS plates, are joined to the upper portion of the support substrate 21. Each of the first backing plate 25 and the second backing plate 26 has an opening for forming a common liquid chamber 27 and communicates with the liquid supply port 22 of the support substrate 21. On the second backing plate 26, a damper film 29 of a resin film and a damper plate 29 of an SUS plate are integrally bonded to absorb the shock wave of the liquid due to the displacement of the piezoelectric actuator 37. A predetermined hole is formed in a portion corresponding to the common liquid chamber 27 in the damper plate 29 to form an air chamber 30 so that the damper film 28 can be displaced. Furthermore, a housing 31 in which a passage (not shown) for supplying liquid to the common liquid chamber 27 is formed is joined to the upper part.

  FIG. 16 is a schematic diagram using IJP as a method of manufacturing a piezoelectric actuator. A preferred IJP (inkjet patterning) method will be described as a method for forming the piezoelectric thin film 2 and the electrode 3 of the piezoelectric actuator 37. The wall 8 is formed on the diaphragm 1 by using the IPJ method in which the ink in which the piezoelectric material is dispersed is ejected from the IJ head 32 as ink droplets 33, and the ink in which the electrode material is dispersed is formed as ink droplets 33 from the IJ head 32. The electrode 3 corresponding to the groove 7 is formed by discharging, and then dried and fired. By forming the wall 8 and the electrode 3 simply by the IJP method, low cost is realized.

  FIG. 17 shows an example of a drive waveform for driving the piezoelectric actuator of the droplet discharge head of this embodiment. FIG. 18 is an explanatory diagram for preloading the piezoelectric actuator during droplet discharge. When the piezoelectric body is displaced in the stacking direction, it is generally vibrated by applying a preload. In the piezoelectric actuator 37 according to the present embodiment, a driving method in which a voltage is applied in a direction in which the thickness corresponding to preload increases is important in securing reliability and durability. In order to preload, the diaphragm 1 needs to be convex upward. If it is concave downward, it is necessary to stand by beyond the neutral point (see FIG. 18). In the piezoelectric actuator of this embodiment, by applying the reference voltage Vb as shown in FIG. 17, the thickness of the wall 8 is increased and a predetermined preload can be set. The voltage is raised to Vt by the drive signal, and after a predetermined time, the voltage is lowered to Vc and discharged. Further, after a predetermined time, the voltage is returned to the reference voltage Vb. Note that Vb = Vc may be used.

  Such a waveform is a driving waveform that is generally used. However, when the waveform is employed in the piezoelectric actuator 37 of the present embodiment, the peeling of the interface between the electrode 3 and the piezoelectric wall 8 is reduced. In the piezoelectric actuator 37, there is a concern about peeling at the interface between the electrode 3 and the piezoelectric body from the viewpoint of reliability and durability. In this embodiment, when a preload voltage is applied, the piezoelectric wall 8 extends in the direction in which the electric field is formed, which is opposite to the direction away from the electrode 3 (FIG. 1 (c). )reference). By applying the preload voltage in this way, no force in the direction in which the wall 8 and the electrode 3 are separated from each other is generated, and thus a highly integrated piezoelectric actuator and droplet discharge head with excellent reliability and durability can be realized. .

FIG. 19 is a schematic view using the MEMS technology as a method for manufacturing the piezoelectric actuator of the present embodiment. This is manufactured by bonding the actuator substrate 38 of the droplet discharge head 40 at the wafer level of the liquid chamber substrate wafer 34 and the support substrate wafer 35, and is excellent as a mass production method and can be provided at low cost.
As the general overall process, the following process is preferable.
1. The diaphragm 1 is formed on the liquid chamber substrate wafer 34 by a film forming method such as sputtering using a material having a relatively high Young's modulus such as SiO ₂ , SiN, PS (polysilicon), or SiON.
2. A piezoelectric material is formed on the diaphragm 1 by sputtering, Solgel method or IJP method, and the groove 7 is formed by etching.
3. The electrode 3, the first electrode 5, and the second electrode 6 are formed in the groove 7 by sputtering or IJP method.
4). The electrode surface is smoothed, the protective film 4 is formed of SiO ₂ , SiN or the like, and unnecessary portions are removed by etching.
5. Bumps for bonding the drive IC 23 are formed by sputtering, and after the stud bumps are formed, the drive IC 23 is flip-chip bonded.
6). The liquid supply port 22 and the space 24 are formed in the support substrate wafer 35 polished to a predetermined thickness and bonded to the liquid chamber substrate wafer 34.
7). The liquid chamber substrate wafer 34 is polished to a predetermined thickness, and the liquid chamber, the fluid resistance, and the liquid inlet are formed by etching.
8). The head chip 36 is diced and the nozzle plate 16 is joined.

  In the present embodiment, as the liquid chamber 18 of the droplet discharge head is increased in density, the vibration of the vibration plate 1 cannot be obtained with the conventional piezoelectric actuator. It is bent. Since the increase in the density of the liquid chamber 18 and the decrease in the distance of the fixed end of the diaphragm 1 are proportional, it can be said that the diaphragm becomes a hard diaphragm by increasing the density. As described above, in the piezoelectric actuator 37 of the present embodiment, the amount of flexure of the diaphragm 1 can be increased by increasing the number of grooves 7 formed in the piezoelectric thin layer 2, and in particular, integration of 600 dpi or more. Is an essential technology. Further, in such a high density droplet discharge head 40, it is necessary to deform the hard diaphragm 1, and as a result, the natural frequency of the diaphragm increases. The improvement of the natural frequency improves the followability to a high-speed frequency, and as a result, the droplet discharge head 40 having a good frequency characteristic and a short natural frequency (Tc) can be achieved. Further, the shock wave applied to the ink is proportional to the impulse. Since the impulse in this case is a displacement amount per unit time, obtaining a constant displacement at a high frequency generates a large amount of energy. Accordingly, it is possible to discharge high viscosity ink or the like.

Next, an ink jet recording apparatus as an image forming apparatus on which the droplet discharge head 40 is mounted will be described.
FIG. 20 is a schematic diagram of a line type ink jet printer as an image forming apparatus equipped with a droplet discharge head. A conveyor belt 65 wound around a belt driving roller 64 and a belt driven roller 63 is driven by a motor (not shown). A platen 66 is installed inside the conveyor belt 65 as a guide for the conveyor belt. The recording paper 61 accumulated in the paper feed cassette 67 is separated by the paper feed roller 60 and fed along the guide plate 68.
50Bk, 50C, 50M, and 50Y of the respective colors (Bk, C, M, and Y) of the ink jet line head are disposed at positions facing the platen 66 so that the ink can be ejected toward the conveyance belt 65. These inkjet line heads 50 are usually configured to have a length equal to or greater than the paper width by accurately arranging several short inkjet heads, for example, the droplet discharge heads 40 shown in FIG. 15 of the present embodiment.

  Furthermore, a preprocessing unit 51 that performs preprocessing on the recording paper may be provided. The pretreatment unit 51 is, for example, a unit that applies a pretreatment liquid that can fix ink on the recording paper 61. Reference numeral 55 denotes a post-processing unit that dries the ink attached to the recording paper 61. The peeling claw 56 is installed so as to peel off the recording paper 61 from the conveying belt 65, and the recording paper 61 is sent to the pair of paper discharge rollers 57 and 58 and deposited on the paper discharge cassette 59. As described above, since the small, highly integrated, and low-cost heads are configured as an array, a low-cost and high-quality image forming apparatus can be provided.

  In addition, the piezoelectric actuator 37 of this embodiment can be used not only for the above-described droplet discharge head 40 but also for a buzzer, a speaker, a pump for transferring liquid, and the like. Since the piezoelectric actuator 37 of the present embodiment can increase the amount of displacement as described above, the piezoelectric actuator 37 can be driven with low power. For example, when used for a buzzer, the sound volume depends on the amount of displacement, so increasing the amount of displacement makes it possible to increase the sound volume with a low voltage, thereby reducing power consumption.

What has been described above is merely an example, and the present invention has specific effects for each of the following modes.
(Aspect A)
A first layer portion in which a plurality of piezoelectric walls 8 and electrodes 3 are alternately arranged in the surface direction, and a second layer portion integrally formed with the first layer portion in the thickness direction so as to extend over the surface direction The piezoelectric actuator is characterized in that when the voltage is applied to the electrode of the first layer portion, the first layer portion is deformed in the surface direction, and both layers are bent.
According to this configuration, as described in the above embodiment, when the voltage applied to the electrodes of the first layer portion is displaced, the individual piezoelectric bodies sandwiched between the electrodes are displaced, so that the entire first layer portion is in the surface direction. Deform. Due to the deformation in the surface direction of the first layer portion, a new piezoelectric actuator in which both the first layer portion and the second layer portion integrally formed with the first layer portion in the thickness direction are bent. In this configuration, by providing the piezoelectric body and the electrodes of the first layer portion so as to increase the number of piezoelectric bodies sandwiched between the electrodes, the deformation in the surface direction of the entire first layer portion is increased, and the deflection of the whole of both layers is increased. The amount can be increased. For this reason, the amount of displacement can be increased without lowering the rigidity of the actuator itself or increasing the drive voltage as in a conventional unimorph piezoelectric actuator.

(Aspect B)
In (Aspect A), the diaphragm 1 is provided as the second layer portion. According to this, the piezoelectric actuator 37 having the configuration shown in FIG. 1, 3, 4 or 5 is obtained.

(Aspect C)
In (Aspect B), the second layer portion is constituted by the diaphragm 1, and the electrode 3 of the first layer portion is disposed so as to be in contact with the second layer portion. According to this, the piezoelectric actuator 37 having the structure shown in FIG.

(Aspect D)
In (Aspect B), an intermediate layer portion such as a lower portion 2a of the piezoelectric thin film continuous with the piezoelectric wall 8 is provided between the first layer portion including the piezoelectric wall 8 and the electrode 3 and the diaphragm 1. And the second layer portion is constituted by the diaphragm 1 and the intermediate layer portion. According to this, the piezoelectric actuator 37 having the configuration shown in FIG. 5 is obtained. In this piezoelectric actuator, the intermediate layer portion is substantially an inactive region and can be used for adjustment of rigidity and warpage due to residual stress caused by heat during film formation. For this reason, the effect that the freedom degree of design increases is acquired.

(Aspect E)
(Aspect A) includes a first layer portion composed of the piezoelectric wall 8 and the electrode 3, and a piezoelectric layer portion such as a lower portion 2a of the piezoelectric thin film continuous with the piezoelectric member of the first layer portion. The two-layer portion is composed of the lower portion 2a of the piezoelectric thin film. According to this, the piezoelectric actuator 37 having the configuration shown in FIG. 6 is obtained. In this piezoelectric actuator, the lower portion 2 a of the piezoelectric thin layer 2 is substantially an inactive region and has the function of the diaphragm 1. For this reason, it is possible to use the lower part of the piezoelectric thin layer 2 as the second layer portion instead of the diaphragm 1 without providing the diaphragm 1. In this configuration, the lower portion 2a of the piezoelectric thin layer 2 and the piezoelectric wall 8 are integrally formed, so that strength can be ensured. Furthermore, since the diaphragm manufacturing process can be omitted, the cost can be reduced.

(Aspect F)
In any one of (Aspect A) to (Aspect E), the electrode 3 has an inclination angle 9 such that the length in the surface direction becomes narrower as it approaches the second layer portion such as the diaphragm 1. Is 45 degrees or more and 90 degrees or less. According to this, the displacement of the wall 8 of the piezoelectric body can be efficiently transmitted to the second layer portion such as the diaphragm 1.

(Aspect G)
In any one of (Aspect A) to (Aspect F), the surface of the electrode 3 is subjected to a planarization treatment. According to this, since the convex portion of the electrode surface is polished and the concave portion is filled to ensure insulation between the electrodes, the displacement of the piezoelectric body can be generated efficiently.

(Aspect H)
In any one of (Aspect A) to (Aspect G), a first electrode in which one electrode adjacent to each other among the plurality of electrodes 3 and the other electrode are arranged to face each other on the same plane as the piezoelectric thin film. 5 and the second electrode 6 form a comb-like electrode. According to this, the electrode which applies a voltage to the wall 8 of a piezoelectric material can be arrange | positioned efficiently.

(Aspect I)
In any one of (Aspect A) to (Aspect H), the wall 8 of the piezoelectric body and the electrode 3 are arranged in a curved shape such as an arc shape or a wave shape. According to this, the electrode area can be set large, the displacement force of the piezoelectric body can be increased, and the area efficiency can be increased even with an irregular laminate.

(Aspect J)
In any one of (Aspect A) to (Aspect I), the protective film 4 is formed on the surface of the first layer portion composed of the piezoelectric wall 8 and the electrode 3. According to this, the insulation between the electrodes can be improved and the oxidation of the electrodes can be prevented.

(Aspect K)
In any one of (Aspect A) to (Aspect I), a voltage is applied so that the piezoelectric wall 8 of the first layer portion extends in the plane direction. According to this, the displacement amount of the wall 8 of the piezoelectric body can be increased by using the displacement in the direction parallel to the direction in which the electric field is formed with good displacement efficiency.

(Aspect L)
As a method for manufacturing a piezoelectric actuator according to any one of (Aspect B) to (Aspect D) or (Aspect F) to (Aspect K), a piezoelectric thin film 2 is formed on a vibration plate 1, and the piezoelectric thin film is formed. A method is used in which a plurality of grooves 7 are formed in 2 and the electrodes 3 are embedded in the grooves to alternately arrange the piezoelectric bodies and the electrodes to form the first layer portion. According to this, it is possible to form a high-definition and high-density groove 7 in the piezoelectric thin layer 2 and embed the electrode 3 in the groove 7. For this reason, many wall 8 of a piezoelectric material can be formed easily, and low cost is realizable.

(Aspect M)
As a method of manufacturing the piezoelectric actuator described in (Aspect D) or (Aspect E), a plurality of grooves 7 are formed in the upper part of the piezoelectric thin film 2 and the electrodes 3 are embedded in the grooves, thereby alternately alternating the piezoelectric bodies and the electrodes. A method of forming the first layer portion by disposing the first layer portion is used. According to this, it is possible to form a high-definition and high-density groove 7 in the piezoelectric thin layer 2 and embed the electrode 3 in the groove 7. For this reason, many wall 8 of a piezoelectric material can be formed easily, and low cost is realizable.

(Aspect N)
(Aspect A) A method for manufacturing a piezoelectric actuator according to any one of (Aspect K), using an inkjet method in which an ink in which a piezoelectric material or an electrode material is dispersed is ejected by an inkjet head and applied onto a substrate. A first layer portion is formed. According to this, low cost can be realized by simply forming the wall and the electrode by the IJP method.

(Aspect O)
A piezoelectric actuator is provided on a substrate such as the liquid chamber substrate 15 that forms the liquid chamber 18 communicating with the nozzle 17, and a voltage is applied to the piezoelectric actuator to generate pressure in the liquid chamber, thereby discharging droplets from the nozzle. In the droplet discharge head, any one of the piezoelectric actuators of (Aspect A) to (Aspect K) is employed. According to this, as described in the above embodiment, it is possible to obtain a highly integrated liquid droplet ejection head having a stable ejection performance while ensuring rigidity and suppressing driving power.

(Aspect P)
In (Aspect O), the protective film 4 of the piezoelectric actuator is removed on the projection surface of the liquid introduction port communicating with the liquid chamber 18 and the liquid chamber, and the supporting substrate that supports the substrate is bonded using the remaining protective film. To do. According to this, the effect of reinforcing the substrate forming the liquid chamber and the space for protecting the piezoelectric body from the external environment can be formed by a simple film forming process.

(Aspect Q)
In (Aspect P), the liquid chamber has two liquid chamber rows arranged in a staggered manner as the liquid chamber, and a drive circuit for applying a voltage to the electrode is arranged at the center of the liquid chamber row, and the drive circuit has a gap between the drive circuits. And a liquid supply port communicating with the liquid introduction port. According to this, there is an effect that the extraction wiring from the first electrode 5 of the piezoelectric actuator can be simplified and the resistance of the extraction wiring can be reduced.

(Aspect R)
In (Aspect O), (Aspect P), or (Aspect Q), a first voltage Vb is applied to the piezoelectric actuator to maintain the thickness of the wall of the piezoelectric body increasing, and then the thickness of the wall is further increased. A voltage Vt of 2 is applied, and after a lapse of a predetermined time, a third voltage for returning the wall thickness is applied to discharge the droplet. According to this, since preload is applied in the stacking direction to vibrate, reliability and durability can be improved.

(Aspect S)
In (Aspect O), (Aspect P), (Aspect Q) or (Aspect R), a liquid chamber substrate wafer in which a plurality of piezoelectric actuators are formed on a substrate in which a liquid chamber is formed, and a support substrate wafer in which a plurality of support substrates are formed After bonding the wafers at the wafer level, individually cut head chips are mounted. According to this, the piezoelectric actuator can be manufactured at low cost by the MEMS technology.

(Aspect T)
In an image forming apparatus that forms an image by adhering droplets ejected by the droplet ejecting unit to the medium while transporting the medium, the liquid of any one of (Aspect O) to (Aspect S) is used as the droplet ejecting unit. Adopt a droplet discharge head. According to this, it is possible to provide an image forming apparatus capable of obtaining a high-density and high-quality image.

DESCRIPTION OF SYMBOLS 1 Diaphragm 2 Piezoelectric thin film 2a Lower part of piezoelectric thin film 3 Electrode 4 Protective film 5 First electrode 6 Second electrode 7 Groove 9 Inclination angle 8 Wall of piezoelectric body 12 Power supply 15 Liquid chamber substrate 16 Nozzle substrate 17 Nozzle 18 Liquid chamber 21 Support substrate 37 Piezoelectric actuator 40 Droplet discharge head

Japanese Patent No. 3882915 JP 2010-208300 A JP 2008-149662 A

Claims (20)

  A first layer portion in which a plurality of piezoelectric bodies and electrodes are alternately arranged in the surface direction; and a second layer portion integrally formed with the first layer portion in the thickness direction so as to extend over the surface direction. The piezoelectric actuator is characterized in that when the voltage is applied to the electrode of the first layer portion, the first layer portion is deformed in the surface direction, and both layers are bent.   2. The piezoelectric actuator according to claim 1, further comprising a diaphragm as the second layer portion.   3. The piezoelectric actuator according to claim 2, wherein the second layer portion is constituted by a diaphragm, and the electrode of the first layer portion is arranged in contact with the second layer portion.   3. The piezoelectric actuator according to claim 2, further comprising an intermediate layer portion formed of a piezoelectric body continuous with the piezoelectric body of the first layer portion between the first layer portion and the diaphragm, wherein the second layer portion is A piezoelectric actuator comprising the intermediate layer portion and the diaphragm.   2. The piezoelectric actuator according to claim 1, further comprising a piezoelectric layer portion continuous with the piezoelectric body of the first layer portion, wherein the second layer portion is constituted by a piezoelectric layer portion continuous with the piezoelectric body of the first layer portion. Piezoelectric actuator characterized by being made.   6. The piezoelectric actuator according to claim 1, wherein the electrode of the first layer portion is inclined so that the length in the surface direction becomes narrower as it approaches the second layer portion. 7. A piezoelectric actuator having an angle and having an inclination angle of 45 degrees or more and 90 degrees or less.   7. The piezoelectric actuator according to claim 1, wherein the surface of the electrode of the first layer portion is subjected to a planarization process. Piezoelectric actuator.   8. The piezoelectric actuator according to claim 1, wherein one of the plurality of electrodes of the first layer portion adjacent to each other, and the other electrode, Is a comb-like electrode facing the first layer portion on the same plane.   The piezoelectric actuator according to any one of claims 1 to 8, wherein the piezoelectric body and the electrode of the first layer portion are arranged in a curved shape.   10. The piezoelectric actuator according to claim 1, further comprising a protective film on a surface of the first layer portion. 11.   11. The piezoelectric actuator according to claim 1, wherein a voltage is applied so that the piezoelectric body of the first layer portion extends in a plane direction.   12. The method for manufacturing a piezoelectric actuator according to claim 2, 3, 4, 6, 7, 8, 9, 10 or 11, wherein a piezoelectric thin film is formed on a diaphragm and the piezoelectric actuator is manufactured. A plurality of grooves are formed in a thin film of a body, and the first layer portion is formed by alternately arranging the piezoelectric bodies and the electrodes by embedding electrodes in the grooves. Method.   6. The method of manufacturing a piezoelectric actuator according to claim 4, wherein a plurality of grooves are formed on an upper portion of the piezoelectric thin film, and an electrode is embedded in the groove portion to bury the piezoelectric on the upper portion of the piezoelectric thin film. A method of manufacturing a piezoelectric actuator, wherein the first layer portion is formed by alternately arranging a body and the electrode.   12. The method of manufacturing a piezoelectric actuator according to claim 1, wherein an ink jet method in which an ink in which a piezoelectric material or an electrode material is dispersed is ejected by an ink jet head and applied onto a substrate is used. A method for manufacturing a piezoelectric actuator, wherein a single layer portion is formed. In a liquid droplet ejection head, in which a piezoelectric actuator is provided on a substrate forming a liquid chamber communicating with a nozzle, and a voltage is applied to the piezoelectric actuator to generate pressure in the liquid chamber to eject liquid droplets from the nozzle ,
A liquid droplet ejection head, wherein the piezoelectric actuator according to any one of claims 1 to 11 is adopted as the piezoelectric actuator.   16. The liquid droplet ejection head according to claim 15, wherein the protective film of the piezoelectric actuator is removed on the projection surface of the liquid chamber and the liquid introduction port communicating with the liquid chamber, and the remaining protective film is used to support the substrate. A droplet discharge head characterized by bonding a supporting substrate to be bonded.   17. The liquid droplet ejection head according to claim 16, wherein the liquid chamber has two rows of liquid chambers arranged in a staggered manner, and a driving circuit for applying a voltage to the electrode is arranged at the center of the liquid chamber row, and the support is provided. A droplet discharge head, wherein the substrate is provided with a space in which the drive circuit is accommodated with a gap and a liquid supply port communicating with the liquid introduction port.   18. The droplet discharge head according to claim 15, wherein a first voltage that maintains the piezoelectric body of the first layer portion in a plane direction is applied to the piezoelectric actuator. And then applying a second voltage that further expands the piezoelectric body in the surface direction, and after a predetermined time has elapsed, applying a third voltage that returns the displacement in the surface direction causes the droplets to be ejected. A droplet discharge head characterized by that.   19. The liquid droplet ejection head according to claim 15, wherein a liquid chamber substrate wafer in which a plurality of the piezoelectric actuators are formed on a substrate on which the liquid chamber is formed, and a plurality of the support substrates are provided. A droplet discharge head comprising: a head chip that is cut individually after bonding the wafer to the formed support substrate wafer at a wafer level. In an image forming apparatus for forming an image by adhering droplets ejected by droplet ejecting means to the medium while conveying the medium,
20. An image forming apparatus using the droplet discharge head according to claim 15 as the droplet discharge unit.

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