JP6460450B2 - Electromechanical conversion element, droplet discharge head, image forming apparatus, and droplet discharge device - Google Patents

Description

The present invention relates to an electromechanical conversion element including an electromechanical conversion film made of a piezoelectric body, a droplet discharge head including the electromechanical conversion element , an image forming apparatus, and a droplet discharge apparatus .

  2. Description of the Related Art Conventionally, as an image forming apparatus such as a printer, a facsimile machine, and a copying apparatus, a liquid droplet ejecting apparatus including a liquid droplet ejecting head that ejects ink droplets that are liquids for image formation is known. The droplet discharge head includes a nozzle that discharges a droplet, a liquid chamber that communicates with the nozzle, and a pressure generation unit that generates pressure in the liquid in the liquid chamber. As this pressure generating means, for example, there is known one in which a piezo-type electromechanical conversion element having an electromechanical conversion film made of a piezoelectric body is provided on a diaphragm constituting a part of a wall surface of a liquid chamber. When the electromechanical conversion element is deformed by application of a voltage, the surface of the diaphragm provided with the electromechanical conversion element on the liquid chamber side is displaced, and pressure can be generated in the liquid in the liquid chamber.

  As the electromechanical conversion element, a configuration in which a lower electrode, an electromechanical conversion film, an upper electrode, and the like are stacked is known. As a material for this electromechanical conversion film, a material having a perovskite crystal structure such as lead zirconate titanate (PZT) is generally used. An electromechanical conversion film having a perovskite crystal structure is a ferroelectric material having spontaneous polarization. In a ferromagnetic material, when the direction of the spontaneous polarization axis coincides with the direction of the electric field, strain displacement (strain displacement due to the piezoelectric effect) extending in the direction of the spontaneous polarization axis is obtained.

  In Patent Document 1, in an electromechanical conversion film having such a perovskite crystal structure, the crystallographic orientation of the (100) plane is made high (crystal orientation ratio of 80 [%] or more) to align the spontaneous polarization axis direction, and in that direction It is described that the strain displacement due to the piezoelectric effect of the electromechanical transducer can be increased by forming an electric field. Further, it is described that in this electromechanical conversion film, the strain displacement of the electromechanical conversion element can be further increased by utilizing the effect of domain rotation that rotates the polarization domain. The polarization domain is a region in the electromechanical conversion film where the spontaneous polarization axis directions are aligned.

  Further, in order to increase the strain displacement, in the electromechanical conversion film having the perovskite crystal structure, the peak shape of the diffraction intensity obtained on the plane parallel to the plane preferentially oriented by the measurement by the θ-2θ method is expressed. Experience has shown that making it asymmetric is effective. In addition, the peak of diffraction intensity means the convex part of the diffraction intensity curve obtained by measurement.

However, in the electromechanical conversion film having the perovskite crystal structure, even if the peak shape of the diffraction intensity obtained on the plane parallel to the plane preferentially measured by the θ-2θ method is an asymmetric shape, the strain displacement is reduced. It turns out that it cannot be large enough.
In the analysis of the crystal structure of the electromechanical conversion film having the perovskite crystal structure, in order to evaluate how much the crystal plane is inclined with respect to the substrate surface, the position where the diffraction intensity is maximum at the peak of the diffraction intensity (2θ) In some cases, the tilt angle is measured. The present inventors have found that the shape of the peak of the diffraction intensity obtained by measuring with the tilt angle (χ) is an important criterion for increasing the strain displacement.

The present invention has been made in view of the above background, and an object of the present invention is to provide an electromechanical conversion element , an image forming apparatus, and a droplet discharge apparatus that can obtain sufficient strain displacement by an electromechanical conversion film having a perovskite crystal structure. Is to provide.

The present invention relates to an electromechanical conversion comprising a lower electrode formed directly or indirectly on a substrate or a base film, and a piezoelectric body formed on the lower electrode and having a perovskite crystal structure preferentially oriented in a {100} plane. In the electromechanical conversion element including a film and an upper electrode formed on the electromechanical conversion film, the electromechanical conversion film corresponds to a {100} plane as measured by a θ-2θ method of X-ray diffraction. The diffraction intensity peak shape obtained when the tilt angle (χ) is swung in the range of ± 15 [°] at the position (2θ) at which the diffraction intensity is maximum in the diffraction intensity peak is bent at two locations. Of the bent points, | χ_max−χ_2nd | is 2 [°] or more when the position of the point with the higher diffraction intensity is χ_max and the position of the other point is χ_2nd 10 [°] or less It is characterized by being.

  According to the present invention, sufficient strain displacement can be obtained by the electromechanical conversion film having a perovskite crystal structure.

FIG. 3 is a cross-sectional view illustrating an example of a schematic configuration of a droplet discharge head according to the present embodiment. An example of a peak of diffraction intensity on the {200} plane obtained by measurement by X-ray diffraction θ-2θ method in a PZT film preferentially oriented on the {100} plane. The graph explaining the degree of asymmetry of the peak shape of the diffraction intensity obtained by the X-ray diffraction measurement by the θ-2θ method in the PZT film preferentially oriented in the {100} plane. Explanatory drawing about 90 [degree] domain rotation. An example of a diffraction intensity curve obtained by measuring the tilt angle of a PZT film preferentially oriented in the {100} plane. The schematic diagram of the crystal structure of the PZT film | membrane at the time of using PbTiO3 for a 1st oxide layer. Sectional drawing which shows an example of schematic structure of the electromechanical conversion element of the droplet discharge head. The perspective view which shows an example of schematic structure of a polarization processing apparatus. The graph which shows a PE hysteresis curve. Explanatory drawing of the principle of polarization processing. FIG. 3 is a cross-sectional view showing a configuration example in which a plurality of the liquid discharge heads are arranged. FIG. 3 is a perspective view showing an example of an ink jet recording apparatus using the droplet discharge head. Explanatory drawing which looked at the mechanism part of the same inkjet recording device from the side.

  Hereinafter, an embodiment in which the present invention is applied to an electromechanical transducer that is a constituent element of a droplet discharge head used in an inkjet recording apparatus as an image forming apparatus (droplet discharge apparatus) will be described.

  In the following description, the {hkl} plane represents the (hkl) plane and a plurality of crystal planes equivalent to the (hkl) plane from the symmetry that does not consider the direction of spontaneous polarization in the piezoelectric crystal. Represents. The {hkl} plane may be any one of the (hkl) plane and a plurality of crystal planes equivalent to the (hkl) plane, or the (hkl) plane and the (hkl) plane. It may be a plurality of crystal planes selected from a plurality of equivalent crystal planes. For example, in the electromechanical conversion film having the perovskite crystal structure, the {100} plane is any one of a plurality of crystal planes including a (100) plane and other five crystal planes equivalent to the (100) plane. One or more. In the present specification, the peak of diffraction intensity refers to a convex portion of a diffraction intensity curve obtained by X-ray diffraction measurement and does not indicate the maximum value of diffraction intensity.

  The ink jet recording apparatus has many advantages such as extremely low noise and high-speed printing, and further, the degree of freedom of ink as a liquid for image formation, and the use of inexpensive plain paper. For this reason, the ink jet recording apparatus is widely deployed as an image forming apparatus such as a printer, a facsimile machine, and a copying apparatus.

  A droplet discharge head used in an inkjet recording apparatus includes a nozzle for discharging a droplet (ink droplet) for image formation, a pressure liquid chamber communicating with the nozzle, and a pressure for discharging ink in the pressure liquid chamber. Pressure generating means for generating The pressure generating means in the present embodiment includes a vibration plate that forms part of the wall surface of the pressurized liquid chamber, and an electromechanical conversion element having a thin film electromechanical conversion film made of a piezoelectric body that deforms the vibration plate. A piezo-type pressure generating means provided. The electromechanical conversion element deforms itself when a predetermined voltage is applied, and generates pressure on the liquid in the pressurized liquid chamber by displacing the surface of the diaphragm with respect to the pressurized liquid chamber. With this pressure, it is possible to eject droplets (ink droplets) from a nozzle communicating with the pressurized liquid chamber.

The piezoelectric body constituting the electromechanical conversion film is a material having a piezoelectric characteristic that is deformed by application of a voltage. In this embodiment, lead zirconate titanate (PZT: Pb (Zr _x , Ti _1-x ) O ₃ ), which is a ternary metal oxide having a perovskite crystal structure, is used as the piezoelectric body. As described above, there are a plurality of types of vibration modes when a drive voltage is applied to an electromechanical conversion element having an electromechanical conversion film (hereinafter referred to as “PZT film”) made of PZT. For example, there are a longitudinal vibration mode (push mode) accompanied by deformation in the film thickness direction by the piezoelectric constant d33 and a transverse vibration mode (bend mode) accompanied by deflection deformation by the piezoelectric constant d31. Furthermore, there is a shear mode using the shear deformation of the film.

  As will be described later, the electromechanical transducer having the PZT film can directly form a pressurized liquid chamber and an electromechanical transducer in a Si substrate by using a semiconductor process or a MEMS (Micro Electro Mechanical Systems) technique. it can. Thus, the electromechanical transducer can be formed as a thin film piezoelectric actuator that generates pressure in the pressurized liquid chamber.

Next, an example of the structure of a droplet discharge head including a piezoelectric actuator 400 as an electromechanical transducer according to an embodiment of the present invention will be described.
FIG. 1 is a cross-sectional view showing an example of a schematic configuration of a droplet discharge head according to the present embodiment. The droplet discharge head of this embodiment includes a substrate 401, a vibration plate 402, a nozzle plate 403, a pressurized liquid chamber (pressure chamber) 404, a first electrode 405 as a lower electrode, a PZT film 406 as an electromechanical conversion film, A second electrode 407 as an upper electrode is provided. The pressurized liquid chamber 404 is formed so as to be surrounded by a partition wall 401 a formed on the substrate 401, the vibration plate 402, and the nozzle plate 403, and communicates with the nozzle 403 a of the nozzle plate 403.

  As a material of the substrate 401, it is preferable to use a silicon single crystal substrate, and it is preferable to have a thickness in the range of 100 [μm] to 600 [μm]. There are three types of surfaces of the substrate 401, {100} plane, {110} plane, and {111} plane, but the {100} plane and {111} plane are generally widely used in the semiconductor industry. In the embodiment, a single crystal substrate whose surface is mainly a {100} plane is mainly used.

When the pressurized liquid chamber 404 as shown in FIG. 1 is manufactured, the silicon single crystal substrate is processed using etching. In this case, anisotropic etching is used as an etching method. It is common. Anisotropic etching utilizes the property that etching rates are different from each other for a plurality of types of surfaces of a crystal structure. For example, in anisotropic etching immersed in an alkaline solution such as KOH, the {111} plane has an etching rate of about 1/400 compared to the {100} plane. Accordingly, a structure having an inclination of about 54 [°] can be produced on the {100} plane, whereas a deep groove can be removed on the {110} plane, so that the arrangement density is increased while maintaining rigidity. I know you can. In this embodiment, it is also possible to use a single crystal substrate whose surface is a {110} plane. However, in this case, SiO ₂ that is a mask material is also etched, and this point is also used with attention.

The diaphragm 402 receives the force generated by the PZT film 406 and is deformed to displace the surface, thereby generating pressure on the liquid in the pressurized liquid chamber 404 and discharging droplets from the nozzle 403a. It is preferable that it has strength. Examples of the material of the diaphragm 402 include those made of Si, SiO ₂ , and Si ₃ N ₄ by a CVD (Chemical Vapor Deposition) method.

Furthermore, it is preferable to select a material close to the linear expansion coefficient of the first electrode 405 and the PZT film 406 as the material of the diaphragm 402. In particular, the PZT film 406 generally uses PZT as a material. Therefore, the diaphragm 402 has a linear expansion coefficient close to a linear expansion coefficient of 8 × 10 ⁻⁶ [1 / K], that is, a line of 5 × 10 ⁻⁶ [1 / K] to 10 × 10 ⁻⁶ [1 / K]. A material having an expansion coefficient is preferred. Further, the diaphragm 402 is more preferably a material having a linear expansion coefficient of 7 × 10 ⁻⁶ [1 / K] or more and 9 × 10 ⁻⁶ [1 / K] or less.

  Specific materials for the diaphragm 402 include aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds thereof. These can be produced by a spin coater using a sputtering method or a sol-gel method. The film thickness is preferably from 0.1 [μm] to 10 [μm], and more preferably from 0.5 [μm] to 3 [μm]. If it is smaller than this range, it will be difficult to process the pressurized liquid chamber 404, and if it is larger than this range, the base will be difficult to deform and displace, and ink droplet ejection will become unstable.

  In addition, the diaphragm 402 is preferably constructed by laminating a plurality of films having tensile stress or compressive stress by low pressure (LP) CVD. The reason is as follows. In the case of the single-layer film diaphragm 402, an example of the material is an SOI wafer. In this case, the cost of the wafer is very high, and it is not possible to set an arbitrary film stress when trying to make the bending rigidity uniform. On the other hand, in the case of the laminated diaphragm 402, the degree of freedom of setting the rigidity and film stress of the diaphragm 402 to desired values can be obtained by optimizing the laminated configuration. Therefore, overall rigidity and stress control of the diaphragm 402 can be realized by a combination of lamination, film thickness, and lamination configuration.

  Therefore, the material and film thickness of the electrode layer and the ferroelectric layer constituting the piezoelectric actuator (piezoelectric element) can be dealt with in a timely manner. Further, since the diaphragm 402 can be obtained with a stable vibration plate 402 with less variation in rigidity and stress due to the firing temperature of the piezoelectric actuator (piezoelectric element), the droplet ejection characteristics can be made highly accurate and stable droplet ejection. A head can be realized.

The first electrode 405 as a lower electrode is a layer of a metal material. Conventionally, platinum (Pt) having high heat resistance and low reactivity has been used as a metal material, but it may not be said that it has sufficient barrier properties against lead, and iridium or platinum-rhodium. Platinum group elements such as these, and these alloy films are also included. When platinum (Pt) is used, Ti, TiO ₂ , Ta, Ta ₂ O ₅ , Ta ₃ N _5, etc. should be laminated first because of poor adhesion to the base (particularly SiO ₂ ). Is preferred. As a manufacturing method of the first electrode 405, vacuum film formation such as sputtering or vacuum deposition is generally used. The film thickness of the first electrode 405 is preferably 0.02 [μm] or more and 0.1 [μm] or less, and more preferably 0.05 [μm] or more and 0.1 [μm] or less. Further, in consideration of the fatigue characteristics over time of deformation of the PZT film 406, a first oxide layer 408 made of a conductive oxide such as strontium ruthenate is stacked between the first electrode 405 and the PZT film 406. Is preferred.

The first oxide layer 408 also affects the orientation of the PZT film 406 formed thereon. For this reason, it is necessary to appropriately select the material of the first oxide layer 408 in accordance with the plane orientation of the PZT film 406 to be preferentially oriented. In this embodiment, LaNiO ₃ , TiO ₂ , lead titanate (PbTiO ₃ ), or the like is selected as the material of the first oxide layer 408 in order to preferentially align the {100} plane of the PZT film 406. The film thickness of the first oxide layer 408 is preferably 20 [nm] or more and 80 [nm] or less, and more preferably 30 [nm] or more and 50 [nm] or less. If the thickness is smaller than this range, sufficient characteristics cannot be obtained in the initial displacement and displacement deterioration. In addition, if it exceeds this range, the withstand voltage of the PZT film 406 to be formed after that becomes very bad, and leakage tends to occur.

  Similarly to the first electrode 405, the second electrode 407 as the upper electrode is made of a metal material such as platinum (Pt). The second oxide 407 is used for the purpose of ensuring adhesion between the platinum film and the PZT film 406. A physical layer 409 may be provided. The second oxide layer 409 is formed by stacking a conductive oxide such as strontium ruthenate.

The PZT film 406 is a piezoelectric body having a perovskite crystal structure, and is a solid solution of lead zirconate (PbZrO ₃ ) and PbTiO ₃ , and has different characteristics depending on the ratio. In general, the composition exhibiting excellent piezoelectric characteristics has a ratio of PbZrO ₃ and PbTiO ₃ of 53:47. When expressed by a chemical formula, Pb (Zr _0.53 Ti _0.47 ) O ₃ , general PZT (53/47 ). Examples of composite oxides other than PZT include barium titanate. In this case, it is also possible to prepare a barium titanate precursor solution by dissolving barium alkoxide and a titanium alkoxide compound in a common solvent. is there.

These materials are described by the general formula ABO ₃ and correspond to composite oxides containing A = Pb, Ba, Sr, B = Ti, Zr, Sn, Ni, Zn, Mg, and Nb as main components. Specifically, (Pb _1-x , Ba _x ) (Zr, Ti) O ₃ , (Pb) (Zr _x , Ti _y , Nb _1-xy ) O ₃ , which is the Pb of the A site This is a case where a part of Ba is substituted and a case where Zr and Ti of the B site are partly substituted by Nb. Such substitution is possible with a divalent element, and is performed by material modification for application of deformation characteristics (displacement characteristics) of PZT. The effect is to reduce the characteristic deterioration due to the evaporation of lead during the heat treatment. As a manufacturing method, it can be manufactured by a spin coater using a sputtering method or a sol-gel method. In this case, since patterning is required, a desired pattern is obtained by photolithography etching or the like.

  When the PZT film 406 is produced by the sol-gel method, for example, lead acetate, zirconium alkoxide, and titanium alkoxide compound are used as starting materials, and dissolved in methoxyethanol as a common solvent to obtain a uniform solution, thereby producing a PZT precursor solution. it can. Since the metal alkoxide compound is easily hydrolyzed by moisture in the atmosphere, an appropriate amount of acetylacetone, acetic acid, diethanolamine or the like may be added to the precursor solution as a stabilizer. When a PZT film is obtained on the entire surface of the base substrate, it is obtained by forming a coating film by a solution coating method such as spin coating, and performing heat treatments such as solvent drying, thermal decomposition, and crystallization. Since the transformation from the coating film to the crystallized film involves volume shrinkage, it is necessary to adjust the precursor concentration so that a film thickness of 100 nm or less can be obtained in one step in order to obtain a crack-free film. Become.

  The thickness of the PZT film 406 is preferably 0.5 [μm] or more and 5 [μm] or less, and more preferably 1 [μm] or more and 2 [μm] or less. If the thickness of the PZT film 406 is smaller than the preferred range, it becomes difficult to process the pressurized liquid chamber 404 as shown in FIG. On the other hand, if the thickness of the PZT film 406 is larger than the preferable range, the underlying diaphragm 402 is difficult to be deformed and displaced, and the ejection of droplets becomes unstable and sufficient displacement cannot be generated. On the other hand, if the thickness of the PZT film 406 is larger than the above preferred range, many layers are stacked, so that the number of steps increases and the process time becomes longer.

The shape of the unit cell of the PZT crystal having the ABO ₃ type perovskite structure varies depending on the ratio of Ti and Zr as atoms entering the B site. When the Ti ratio is increased, the PZT crystal lattice becomes tetragonal, and when the Zr ratio is increased, the PZT crystal lattice becomes rhombohedral. When the composition ratio of Zr and Ti is adjusted, diffraction is performed at the diffraction intensity peak corresponding to the {200} plane of the PZT film 406 among the diffraction intensity peaks obtained by the X-ray diffraction measurement by the θ-2θ method. The position (2θ) where the intensity is maximum changes.

  The θ-2θ method is one of measurement methods often used as X-ray diffraction. In the θ-2θ method, X-rays are incident on the sample substrate surface to be measured at an angle of θ, and X-rays having an angle of 2θ with respect to the incident X-ray direction are detected among the X-rays reflected from the sample. , Θ is examined for changes in diffraction intensity when θ is changed. In X-ray diffraction, the diffraction intensity increases when the Bragg condition (2 dsin θ = nλ (λ: wavelength of X-ray, d: crystal plane spacing, n: integer)) is satisfied. (Lattice constant) and the above 2θ are in a correspondence relationship. Therefore, based on the value of 2θ at which the diffraction intensity increases, the crystal structure of the sample on which the X-rays are incident can be grasped.

  FIG. 2 is a graph showing an example of a diffraction intensity peak corresponding to the {200} plane of the PZT film 406 among the diffraction intensity peaks obtained by the X-ray diffraction measurement by the θ-2θ method. When the back surface of the substrate 401 is dug by etching or the like, the range of 2θ should be 44.45 [°] or more and 44.75 [°] or less in a state where there is no restraint in the excavated portion. preferable. In the PZT film 406, when preferentially orienting the {100} plane, in order to make 2θ within this range, the composition ratio of Zr and Ti represented by Ti / (Zr + Ti) is 0.45 or more and 0.55. The following is preferable. More preferably, the composition ratio of Zr and Ti is 0.48 or more and 0.52 or less.

  If the composition ratio of Zr and Ti is smaller than the lower limit (0.45), the effect of domain rotation described later is not sufficient, so that sufficient strain displacement of the electromechanical transducer cannot be ensured. In addition, when the composition ratio of Zr and Ti is larger than the upper limit (0.55), the piezoelectric effect is not sufficient, so that sufficient strain displacement of the electromechanical transducer cannot be ensured.

  Further, depending on the composition ratio of Zr and Ti, the asymmetry increases or decreases in the shape of the diffraction intensity peak obtained by the X-ray diffraction measurement by the θ-2θ method. FIG. 3 is a graph illustrating the degree of asymmetry of the peak shape of the diffraction intensity obtained by the X-ray diffraction measurement by the θ-2θ method in the PZT film preferentially oriented in the {100} plane.

  FIG. 3A is an example in which the asymmetry of the diffraction intensity peak shape (G in the figure) is large. In this case, the crystal structure of the PZT film belongs to three structures: a tetragonal a-axis domain structure, a c-axis domain structure, and a rhombohedral, orthorhombic, or pseudocubic structure. The diffraction intensity peak indicated by G in the figure has a tetragonal a-axis domain structure indicated by H in the figure, a tetragonal c-axis domain structure indicated by J in the figure, and a rhombohedral shown by I in the figure. It is a combination of crystals, orthorhombic crystals, or pseudocubic structures. The reason why the peak position of the diffraction intensity of the tetragonal a-axis domain structure is far away from the peak position of the diffraction intensity of the tetragonal c-axis domain structure is that the difference in length between the a-axis and the c-axis is large. It is. The maximum value of the diffraction intensity peak of the tetragonal c-axis domain structure is smaller than the maximum value of the diffraction intensity peak of the tetragonal a-axis domain structure in the film thickness direction of the PZT film. This is because the ratio of the tetragonal a-axis domain structure is large.

  On the other hand, FIG. 3B is an example when the asymmetry of the diffraction peak shape (K in the figure) is small. In this case, the crystal structure of the PZT film belongs to two of a tetragonal a domain and a c-axis domain structure. The peak of diffraction intensity indicated by G in the figure is a combination of the tetragonal a-axis domain structure indicated by K and the tetragonal c-axis domain structure indicated by L in the figure. The reason why the peak position of the diffraction intensity of the tetragonal a-axis domain structure is close to the peak position of the diffraction intensity of the tetragonal c-axis domain structure is that the difference in length between the a-axis and the c-axis is small. It is. The maximum value of the diffraction intensity peak of the tetragonal a-axis domain structure and the maximum value of the diffraction intensity peak of the tetragonal c-axis domain structure are substantially the same. This is because the ratio of the tetragonal a-axis domain structure to the tetragonal c-axis domain structure is substantially the same.

  FIG. 4 is a diagram schematically showing an example of the crystal structure of the PZT film. The arrow in the figure indicates the direction of polarization. As shown in FIG. 4A, an actual crystal is composed of regions having different polarizations. In the figure, if an electric field is formed in the vertical direction in the figure, the region in which the polarization direction is the vertical direction in the figure is a tetragonal a-axis domain, and the region in the horizontal direction is a tetragonal c-axis domain. It is. In tetragonal crystals, the lengths of the a-axis and b-axis are equal and only the c-axis is different. In a tetragonal crystal, the a-axis direction and the b-axis direction are equivalent, and the domain composed of the spontaneous polarization in the [100] direction and the [010] direction and its opposite direction is called the a-axis domain, and the [001] direction and its opposite direction. A domain consisting of the spontaneous polarization is called a c-axis domain.

  The boundary between domains is called a domain wall. The domain wall includes a 180 [°] domain wall having a boundary in which c-axis domains are separated from each other by a domain wall, and a 90 [°] having a boundary in which the a-axis domain and the c-axis domain are separated by a domain wall. There is a domain wall. In FIG. 4A, a region indicated by a dotted line S in the drawing has a 180 [°] domain wall structure. In addition, the region indicated by the dotted line R in the figure has a 90 [°] domain wall structure. In the region of the 180 [°] domain wall structure, when a voltage is applied to form an electric field, the polarization direction of the a-axis domain is reversed (180 [°] domain rotation).

  FIG. 4B is an enlarged view of the region indicated by the dotted line R in FIG. 4A. In the region of 90 [°] domain wall structure, when an electric field is formed in the a-axis direction with respect to the tetragonal c-axis domain, the polarization direction of the c-axis domain changes to the a-axis direction, and the domain direction rotates by 90 °. The phenomenon (90 [°] domain rotation) occurs. Since the c-axis domain rotates 90 ° to become the a-axis domain, the domain wall that is the boundary between the a-axis domain and the c-axis domain moves.

  The 90 [°] domain rotation from the c-axis direction to the a-axis direction does not occur unless the c-axis domain is a region of a 90 [°] domain wall structure in contact with the a-axis domain. That is, even if an electric field is formed in the a-axis direction with respect to a region where the c-axis domains are in contact with each other, 90 [°] domain rotation does not occur. This is because, when an electric field is formed by applying a voltage, first, the a-axis domain is distorted by the piezoelectric effect, and this distortion is transmitted to the adjacent c-axis domain via the 90 [°] domain wall. This is because the domain polarization direction rotates in the direction of electric field formation.

  Compared with the distortion caused by the piezoelectric effect, the distortion caused by non-180 [°] domain rotation such as 90 ° domain rotation becomes larger. That is, if the non-180 [°] domain rotation can be efficiently generated in the electromechanical transducer, the strain displacement of the electromechanical transducer can be improved. In this specification, the term “domain rotation effect” simply refers to a non-180 [°] domain rotation effect.

  When a PZT film having a large asymmetry of the diffraction intensity peak shape as shown in FIG. 3A is used, compared with a case where a PZT film having a small asymmetry as shown in FIG. Thus, it is known that the strain displacement of the electromechanical transducer is increased. This is because by mixing different crystal structures of tetragonal and rhombohedral crystals, the density of non-180 [°] domain walls can be increased and non-180 [°] domain rotation can be efficiently generated. It is considered.

  The θ-2θ method is used to determine how the crystal plane spacing is distributed in the film thickness direction at a certain point on the substrate surface of the film to be measured. For this reason, it is impossible to determine how the crystal plane intervals are distributed in the film thickness direction at a point that is slightly moved in the horizontal direction of the substrate surface from a certain point on the substrate surface. In order to judge this, it is necessary to further perform measurement by the rocking curve method. In the rocking curve method, the incident angle of the X-ray and the detector angle (2θ) are fixed at a position where the diffraction intensity is maximum as measured by the θ-2θ method, and the angle between the sample substrate surface and the incident X-ray (ω ) Is slightly changed in the vicinity of θ to measure the diffraction intensity.

  Further, the crystal growth direction of the film to be measured is not necessarily perpendicular to the substrate surface of the film. When the crystal growth direction of the film is not perpendicular to the substrate surface of the film, the crystal surface is inclined with respect to the substrate surface. In order to determine the degree of this inclination, it is necessary to perform measurement with a further tilt angle (χ) at a position (2θ) where the diffraction intensity is maximized in the measurement by the θ-2θ method. The “tilt angle” means that the (lmn) (l, m, n is 0 or 1) plane of the crystal contained in the electromechanical conversion film is inclined with respect to a plane parallel to the (lmn) plane. In this case, the angle formed between the (lmn) plane and the inclined plane is assumed.

  In a PZT film preferentially oriented in the {100} plane, asymmetry of the peak shape of the diffraction intensity obtained by the X-ray diffraction measurement by the θ-2θ method is increased as shown in FIG. Further, the measurement was performed with the tilt angle changed. FIG. 5 is an example of a diffraction intensity curve when the tilt angle (χ) is continuously changed in a range of ± 15 [°] in such a PZT film. Of the diffraction intensity peaks obtained by the measurement by the θ-2θ method, the tilt angle was swung at the position (2θ) where the diffraction intensity peak corresponding to the {100} plane was maximum. In the figure, the tilt angle (χ) is on the horizontal axis and the diffraction intensity of the diffracted X-rays reflected from the measurement surface is on the vertical axis.

  The diffraction intensity curve shown in FIG. 5A is an example in which the peak shape of the diffraction intensity has a shape like a “normal distribution”. The diffraction intensity curve shown in FIG. 5B is an example in which the peak shape of the diffraction intensity has a shape having two or more bending points. As shown in FIG. 5B, the peak shape of the diffraction intensity is bent at points A and B. Further, the diffraction intensity curve shown in FIG. 5C is an example in which the shape of the peak of the diffraction intensity has a shape having a maximum point of 2 or more. As shown in FIG. 5 (c), the peak shape of the diffraction intensity is maximized at points C and D, and is minimized at point E sandwiched between points C and D.

  Furthermore, in the electromechanical transducer using the PZT film having the characteristics shown in FIGS. 5A to 5C, strain displacement was measured. As a result, when the PZT film having the characteristics shown in FIGS. 5B and 5C is used, the strain displacement is larger than when the PZT film having the characteristics shown in FIG. 5A is used. I understood.

  FIG. 6 is a diagram schematically showing the crystal structure of the PZT film 406. FIG. 6A shows a case where the tilt of the crystal plane is small with respect to the substrate surface of the PZT film 406. FIG. 6B shows a case where the crystal plane has a large inclination with respect to the substrate surface of the PZT film 406. In the PZT film having the characteristics shown in FIG. 5A, the tilt of the crystal plane with respect to the substrate surface of the PZT film 406 is considered to be small as shown in FIG. On the other hand, in the PZT film having the characteristics shown in FIGS. 5B and 5C, the inclination of the crystal plane with respect to the substrate surface of the PZT film 406 is considered to be large as shown in FIG. 6B.

  When the inclination of the crystal plane with respect to the substrate surface of the PZT film 406 increases, it is considered that the crystal lattice is distorted. Although the details of the reason are not well understood, it is considered that when such distortion occurs in the crystal lattice, the density of non-180 [°] domain walls increases and the effect of domain rotation can be enhanced. When a PZT film having the characteristics shown in FIGS. 5B and 5C is used, the strain displacement of the electromechanical transducer becomes larger than when a film having the characteristics shown in FIG. 5A is used. This is probably due to the effect of domain rotation.

  In FIG. 5B, the angle between the film surface and the incident X-ray at the point where the diffraction intensity is larger (point A in the figure) of the two bending points is χ_max, and the other point (point B in the figure). | Χ_max−χ_2nd | is preferably 2 [°] or more and 10 [°] or less, preferably 4 [°] or more and 8 [°] or less, where χ_2nd is the angle between the film surface and incident X-ray. More preferably.

In FIG. 5 (c), the diffraction intensity at the point where the diffraction intensity is larger (point C in the figure) out of the two local maximum points is I {100} _max_2, and the local minimum point (see FIG. When the diffraction intensity at the middle point E) is I {100} _min_2, I {100} _min_2 / I {100} _max_2 is preferably 0.5 or more, and more preferably 0.7 or more. preferable.
Also, when the angle between the sample substrate surface and the incident X-ray at the point where the diffraction intensity is larger among the two maximum points is χ_max, and the angle between the sample substrate surface and the incident X-ray at the other point is χ_2nd. , | Χ_max_2−χ_2nd_2 | is preferably 2 [°] or more and 8 [°] or less, and more preferably 4 [°] or more and 6 [°] or less.

  When I {100} _min_2 / I {100} _max_2 is smaller than the lower limit value (0.5) defined above, strain displacement locally increases. For this reason, when the electromechanical conversion element is continuously driven as a piezoelectric actuator, there is a high possibility that defects such as cracks occur in the PZT film 406. When such a defect occurs due to continuous driving, the strain displacement after driving decreases with respect to the initial strain displacement.

  Also, if | χ_max−χ_2nd | and | χ_max_2−χ_2nd_2 | are smaller than the lower limit values defined above (both 2 [°]), the distortion of the crystal structure of the PZT film is reduced, so that the effect of domain rotation is reduced. Becomes small and sufficient strain displacement cannot be obtained in the electromechanical transducer. When | ω_max−ω_2nd | and | ω_max_2−ω_2nd_2 | are larger than the upper limit values defined above (10 [°] and 8 [°], respectively), the distortion of the crystal structure of the PZT film increases. The strain displacement can be increased. However, when the electromechanical transducer is continuously driven as a piezoelectric actuator, there is a high possibility that a defect such as a crack occurs in the PZT film 406, and the strain displacement after driving is reduced with respect to the initial strain displacement.

  When having the characteristics shown in FIGS. 5B and 5C, the full width at half maximum (FWHM) is preferably 6 [°] or more and 16 [°] or less, and more preferably 8 ° or more and 12 ° or less. Become. When the full width at half maximum is smaller than the lower limit (6 [°]), the distortion of the crystal structure of the PZT film is reduced, so that the effect of domain rotation is reduced and sufficient strain displacement cannot be obtained in the electromechanical transducer. Further, when the half width is larger than the upper limit value (16 [°]), the distortion of the crystal structure of the PZT film increases, so that the strain displacement due to the domain rotation can be increased. However, when the electromechanical transducer is continuously driven as a piezoelectric actuator, there is a high possibility that a defect such as a crack occurs in the PZT film 406, and the strain displacement after driving is reduced with respect to the initial strain displacement. Here, the half width refers to the width of χ at which the diffraction intensity is half the maximum value at the peak of the diffraction intensity obtained when the tilt angle (χ) is swung.

  Let I {hkl} be a value obtained by integrating the diffraction intensity at the peak of the diffraction intensity corresponding to a certain {hkl} plane, where h, k, and l are arbitrary positive integers. Also, ΣI {hkl} is the sum of I {hkl}. The ratio ρ {hkl} (= I {hkl} / ΣI {hkl}) of I {hkl} to ΣI {hkl} indicates the degree of orientation in the {hkl} plane. ρ {hkl} is preferably 0.75 or more, and more preferably 0.85 or more. If ρ {hkl} is smaller than 0.75, a sufficient strain displacement due to the piezoelectric effect cannot be obtained, so that a sufficient amount of displacement of the electromechanical transducer cannot be secured.

Here, the detailed structure of the electromechanical conversion element including the insulating protective film and the lead wiring will be described.
FIG. 7 is a diagram showing a schematic configuration of an element configuration including an insulating protective film and a lead wiring. The first insulating protective film 500 has a contact hole in a region indicated by a dotted line F in the figure, and the first electrode 405 and the first oxide layer 408 include a fifth electrode (common electrode wiring) 501 and a second electrode 407. The second oxide layer 409 is electrically connected to the sixth electrode (individual electrode wiring) 502. A second insulating protective film 503 that protects the fifth electrode 501 and the sixth electrode 502 is formed. A part of the second insulating protective film 503 is opened, and an electrode pad is provided in the opening. An electrode pad manufactured for the fifth electrode is referred to as a fifth electrode pad 504, and an electrode pad manufactured for the sixth electrode is referred to as a sixth electrode pad 505.

  The first insulating protective film 500 serves as a protective film for preventing damage to the electromechanical conversion element due to the film formation / etching process, and also serves to prevent moisture in the atmosphere from permeating. The film thickness of the first insulating protective film 500 needs to be reduced, but this is because if the film thickness is increased, the vibration displacement of the diaphragm is significantly hindered, resulting in a droplet discharge head having a low discharge performance. For this reason, it is preferable to select a dense inorganic material such as oxide, nitride, or carbide for the first insulating protective film 500. An organic material is not suitable as a material for the first insulating protective film 500 because sufficient protection performance cannot be obtained unless the film thickness is increased.

In addition, as the material of the first insulating protective film 500, it is necessary to select a material having high adhesion to the electrode material, the electromechanical conversion film material, and the diaphragm material as a base. As the film formation method of the first insulating protective film 500, the plasma CVD method and the sputtering method are not preferable because they may damage the electromechanical conversion element, and vapor deposition, atomic layer deposition method (ALD method), and the like are preferable. The ALD method is more preferable because of the wide range of materials that can be used. For example, Al ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , Ta ₂ O ₃ , TiO _{2 and the} like used for ceramic materials can be used. By using these materials to form a film by the ALD method, it is possible to produce a thin film having a very high film density and capable of satisfactorily suppressing damage during the film formation / etching process.

  The thickness of the first insulating protective film 500 is preferably in the range of 20 [nm] to 100 [nm]. When the film thickness of the first insulating protective film 500 is greater than 100 [nm], as described above, a droplet discharge head with low discharge performance is obtained. On the other hand, when the thickness of the first insulating protective film 500 is made thinner than 20 [nm], the function as the protective layer is insufficient and the performance of the electromechanical conversion element is degraded.

A configuration in which the first insulating protective film 500 has two layers is also possible. For example, when the first insulating protective film is made thinner and the second insulating protective film is made thicker, two layers are formed in the vicinity of the first oxide layer 408 so that the vibration displacement of the diaphragm 402 is not hindered. Open the insulating protective film of the eye. At this time, any oxide, nitride, carbide, or a composite compound thereof can be used as the second insulating protective film, and therefore, SiO ₂ generally used in semiconductor devices can be used. For film formation, any film formation method such as CVD or sputtering can be used. However, in consideration of the necessity of step coverage at the pattern formation part such as the electrode formation part, CVD that can be formed isotropically is possible. The method is preferably used.

  The film thickness of the second insulating protective film needs to be in a range that does not cause dielectric breakdown by an electric field formed by the voltage applied to the fifth electrode 501 and the sixth electrode 502. In consideration of the surface state of the base of the first insulating protective film 500, pinholes, and the like, the film thickness needs to be 200 [nm] or more, and more preferably 500 [nm] or more.

  For the fifth electrode 501 and the sixth electrode 502, it is preferable to use a metal electrode material made of any one of an Ag alloy, Cu, Al, Au, Pt, and Ir. As a manufacturing method, for example, after forming a film using a sputtering method or a spin coating method, a desired pattern is obtained by photolithography etching or the like. The film thickness is preferably from 0.1 [μm] to 20 [μm], and more preferably from 0.2 [μm] to 10 [μm]. When the film thickness is smaller than 0.2 [μm], the resistance of the film increases, and a sufficient current cannot flow through the electrode, so that the discharge of the droplet discharge head becomes unstable. On the other hand, when the film thickness is larger than 10 [μm], the process time for producing the electrode becomes long.

  The contact resistance of the fifth electrode 501 and the sixth electrode 502 at the contact hole portion (10 [μm] × 10 [μm]) is 10 [Ω] or less for the fifth electrode 501 and 1 [Ω for the sixth electrode 502. The following is preferable. Further, it is more preferable that the fifth electrode 501 is 5 [Ω] or less, and the sixth electrode 502 is 0.5 [Ω] or less. When the contact resistance between the fifth electrode 501 and the sixth electrode 502 exceeds the above-described upper limit values (10 [Ω] and 1 [Ω], respectively), it becomes impossible to supply sufficient current to the electrodes, and droplet discharge The ejection performance of the head decreases.

The second insulating protective film 503 serves as a protective layer for protecting the sixth electrode 502 and the fifth electrode 501. As the material of the second insulating protective film 503, any inorganic material or organic material can be used. However, it is better to select a material having low moisture permeability. For example, in the case of an inorganic material, an oxide, a nitride, or a carbide, and in the case of an organic material, polyimide, an acrylic resin, or a urethane resin can be used. However, it is preferable to select an inorganic material because the organic material needs to be thick and is not suitable for patterning described later. Among inorganic materials, it is preferable to use Si ₃ N _4, which has a proven track record for forming on Al wiring in semiconductor devices. The thickness of the second insulating protective film 503 is preferably 200 [nm] or more, and more preferably 500 [nm] or more. When the film thickness is reduced, a sufficient passivation function cannot be exhibited, and disconnection due to corrosion of the sixth electrode 502 and the fifth electrode 501 is likely to occur, leading to a decrease in the reliability of the droplet discharge head.

  It is preferable to provide an opening on the electromechanical transducer and on the surrounding diaphragm 402. This is the same reason that the individual liquid chamber region is thinned in the first insulating protective film 500 described above. Thereby, it becomes possible to improve the discharge performance and reliability of the droplet discharge head. Since the piezoelectric element is protected by the first insulating protective film 500 and the second insulating protective film 503, photolithography and dry etching can be used to form the opening.

The area of the fifth electrode pad 504 and the sixth electrode pad 505 is preferably 50 × 50 [μm ² ] or more, and more preferably 100 × 300 [μm ² ] or more. When the area of the fifth electrode pad 504 and the sixth electrode pad 505 is smaller than 50 × 50 [μm ² ], sufficient polarization processing cannot be performed. Therefore, when the electromechanical transducer is continuously driven as a piezoelectric actuator. There is a problem in durability, such as the strain displacement after driving gradually decreases with respect to the initial strain displacement.

  Polarization processing was performed on the manufactured piezoelectric element using a polarization processing apparatus. FIG. 8 is a diagram showing a schematic configuration of the polarization processing apparatus. The polarization processing apparatus includes a corona electrode 600, a grid electrode 601, a stage 602 for setting a sample, and the like. A corona power source 603 is connected to the corona electrode 600, and a grid electrode power source 604 is connected to the grid electrode 601. A temperature control function is added to the stage 602. By this temperature control function, polarization treatment can be performed while applying a temperature up to about 350 [° C.]. The stage 602 is grounded. The grid electrode 601 is meshed so that, when a high voltage is applied to the corona electrode 600, ions, charges, and the like generated by the corona discharge 600 are efficiently poured onto the sample placed below. By changing the voltage applied to the corona electrode 600 and the grid electrode 601 and the distance between the sample and each electrode, it is possible to adjust the strength of the corona discharge.

  The state of polarization by the polarization process is determined from the PE hysteresis loop shown in FIG. A hysteresis loop is measured by applying an electric field strength of ± 150 [kV / cm] to the electromechanical conversion film. In FIG. 9, the first polarization at 0 [kV / cm] is defined as Pind, and the polarization at 0 [kV / cm] when the voltage is returned to 0 [kV / cm] after applying a voltage of +150 [kV / cm]. Let it be Pr. A value obtained by subtracting Pin from Pr (Pr−Pind) is defined as a polarizability, and whether the polarization state is good or bad is determined from this polarizability.

As shown in FIG. 9 (a), the polarization rate is about 15 [μC / cm ² ] before the polarization process is performed, but after the polarization process is performed as shown in FIG. 9 (b), The polarizability is about 2 [μC / cm ² ]. The polarizability is preferably 10 [μC / cm ² ] or less, and more preferably 5 [μC / cm ² ] or less. When the polarizability is 10 [μC / cm ² ] or more, when the electromechanical transducer is continuously driven as a piezoelectric actuator, the strain displacement after driving gradually decreases with respect to the initial strain displacement. There is a problem in terms of durability. A desired polarizability can be obtained by adjusting the intensity of corona discharge by the method described above.

  As shown in FIG. 10, when corona discharge is performed using the corona electrode 600, molecules in the atmosphere are ionized to generate cations. This cation flows into the electromechanical transducer 400 through the fifth electrode pad 504 (see FIG. 7) of the electrode, and charges are accumulated. In the electromechanical transducer 400 shown in FIG. 7, a potential difference is generated above and below the electromechanical transducer due to the difference in the amount of charge accumulated in the second electrode 407 that is the upper electrode and the first electrode 405 that is the lower electrode. It is believed that polarization processing is performed. The amount of charge Q required for the polarization treatment is preferably 1E-8 [C] or more, and more preferably 4E-8 [C] or more. If the charge amount Q is less than 1E-8 [C], the polarization process is not sufficiently performed. Therefore, when the electromechanical transducer is continuously driven as an actuator, sufficient strain displacement characteristics cannot be obtained.

  Next, more specific examples in the embodiment according to the present invention will be described together with comparative examples.

[Example 1]
An SiO ₂ film (film thickness: about 1.0 [μm]) was formed as a vibration plate on a 6-inch silicon wafer as a substrate. On this SiO ₂ film, a Ti film (film thickness: about 20 [nm]) was formed at 350 [° C.] by sputtering, and thermally oxidized at 750 [° C.] by RTA (rapid heat treatment). Subsequently, a Pt film (film thickness: about 160 [nm]) was formed as a first electrode (lower electrode) at about 300 [° C.] by sputtering. The TiO ₂ film obtained by thermally oxidizing the Ti film serves as an adhesion layer between the SiO ₂ film and the Pt film.

Next, a PT coating solution prepared at a composition ratio of Pb: Ti = 1: 1 was prepared as a material for the PbTiO ₃ (PT) layer, which is the first oxide layer serving as the underlayer of the PZT film. Further, a PZT precursor coating solution, which was a solution prepared at a composition ratio of Pb: Zr: Ti = 115: 49: 51, was prepared as a material for the PZT film. A specific PZT precursor coating solution was synthesized as follows. First, lead acetate trihydrate, isopropoxide titanium and isopropoxide zirconium were used as starting materials. Crystal water of lead acetate was dissolved in methoxyethanol and then dehydrated. The lead amount is excessive with respect to the stoichiometric composition. This is to prevent crystallinity deterioration due to so-called lead loss during heat treatment. PZT precursor coating solution was synthesized by dissolving isopropoxide titanium and isopropoxide zirconium in methoxyethanol, proceeding with alcohol exchange reaction and esterification reaction, and mixing with the above methoxyethanol solution in which lead acetate was dissolved. . The PZT concentration was 0.5 [mol / l]. The PT coating solution was synthesized in the same manner as the PZT precursor coating solution.

  Using these coating solutions, a PT layer was first formed by spin coating, and then dried at 120 [° C.] by a hot plate. Then, a PZT film was formed by spin coating, and dried (120 [° C.]) and pyrolyzed (400 [° C.]) using a hot plate. The coating, drying and thermal decomposition treatment of this PZT precursor solution was repeated three times to form three layers. After the thermal decomposition treatment of the third layer, heat treatment for crystallization (temperature 730 [° C.]) was performed by RTA (rapid heat treatment). The thickness of the PZT film when the heat treatment for crystallization was completed was 240 [nm]. The PZT precursor solution coating, drying, thermal decomposition and crystallization heat treatment steps were carried out a total of 8 times (24 layers) to obtain a PZT film having a thickness of about 2.0 [μm].

Next, an SrRuO ₃ film (film thickness: 40 [nm]) as a second oxide layer and a Pt film (film thickness: 125 [nm]) as a second electrode (upper electrode) are sputtered on the PZT film, respectively. The film was formed by the method. Then, a photoresist (TSMR8800) manufactured by Tokyo Ohka Co., Ltd. was formed by a spin coat method, and then a pattern as shown in FIG. 10 was formed by photolithography and etching. Note that an ICP etching apparatus manufactured by Samco was used for the etching.

Following pattern formation, an AL ₂ O ₃ film (film thickness: 50 [nm]) as a first insulating protective film was formed by ALD. As raw materials of the AL ₂ O ₃ film, TMA produced by Sigma Aldrich was used for AL, and O ₃ generated by an ozone generator was used for O ₃ . Then, AL ₂ O ₃ films were formed by alternately laminating AL and O ₃ . A contact hole was formed in the first insulating protective film by etching. Then, an AL layer as a fifth electrode and a sixth electrode is formed by sputtering, and a pattern is formed by photolithography and etching, and then an Si ₃ N ₄ layer (film) as a second insulating protective film is formed by plasma CVD. Thickness: 500 [nm]) was formed. Finally, a pressurized liquid chamber was formed on the substrate by anisotropic wet etching using an alkaline solution (KOH solution or TMHA solution). From the above, a droplet discharge head provided with a piezoelectric actuator (thin film PZT actuator) as an electromechanical piezoelectric element was produced.

  Thereafter, polarization treatment was performed by corona charging treatment. For corona charging treatment, a tungsten wire of φ50 [μm] is used. The polarization treatment conditions include a treatment temperature of 80 [° C.], a corona voltage of 9 [kV], a grid voltage of 2.5 [kV], a treatment time of 30 [s], and a distance of 4 [mm] between the corona electrode and the grid electrode. The distance between the grid electrode and the stage was 4 [mm]. The distance between the two sixth electrode pads was 80 [μm].

[Example 2]
The same as Example 1 except that the thickness of the Ti film formed on the SiO ₂ film as the vibration plate was about 50 [nm], and the thermal decomposition temperature after the formation of the PZT film was 350 ° C. A droplet discharge head was produced by this method.

[Example 3]
The Ti film formed on the SiO ₂ film as the vibration plate had a thickness of about 50 [nm], the film formation temperature was 500 ° C., and the thermal decomposition temperature after the formation of the PZT film was 350 ° C. A droplet discharge head was manufactured in the same manner as in Example 1 except that.

[Example 4]
Except that the Ti film formed on the SiO ₂ film as the vibration plate has a film forming temperature of 500 [° C.], the drying temperature after the PZT film is 140 [° C.], and the thermal decomposition temperature is 350 ° C. Prepared a droplet discharge head by the same method as in Example 1.

[Example 5]
A droplet discharge head was produced in the same manner as in Example 1 except that the Ti film formed on the SiO ₂ film as the vibration plate had a film thickness of about 50 [nm] and the film formation temperature was 500 ° C. .
[Example 6]
The liquid was formed in the same manner as in Example 1 except that the Ti film formed on the SiO ₂ film as the vibration plate had a film forming temperature of 500 [° C.] and the drying temperature after forming the PZT film was 140 [° C.]. A droplet discharge head was produced.

[Comparative Example 1]
After the formation of the Ti film formed on the SiO ₂ film as the vibration plate, a TiO ₂ layer serving as an underlayer is formed by sputtering to a thickness of 5 [nm] instead of the PbTiO ₃ layer as the first oxide layer. A droplet discharge head was produced in the same manner as in Example 1 except that.

  Strain displacement (piezoelectric constant) in the initial state of the electromechanical transducer and the state immediately after the durability test in the state where the back side of the substrate was dug into the droplet discharge heads of Examples 1 to 6 and Comparative Example 1 Evaluation was performed. In the durability test, voltage application is repeated 1010 times after evaluation of the initial piezoelectric constant. The piezoelectric constant is measured by a laser Doppler vibrometer from the back side of the substrate when an electric field of 150 [kV / cm] is formed by applying a voltage, and is adjusted by simulation. Calculated by performing. Further, the PZT films of Examples 1 to 6 and Comparative Example 1 were evaluated for crystallinity using X-ray diffraction in a state where the back surface side of the substrate was dug.

  In Examples 1 to 6 and Comparative Example 1, all of the orientation ratios in the {100} plane were 80 [%] or more as measured by the θ-2θ method of X-ray diffraction. That is, it was confirmed that any of the PZT films of Examples 1 to 6 and Comparative Example 1 were preferentially oriented in the {100} plane.

  Table 1 shows the analysis results of the diffraction intensities obtained by measuring the tilt angles of the PZT films of the electromechanical transducers of Examples 1 to 6 and Comparative Example 1. The shape of the peak of the diffraction intensity is shown as to which of the shapes shown in FIGS. Further, the piezoelectric constants of the electromechanical transducers of Examples 1 to 6 and Comparative Example 1 were also measured and are shown in Table 1.

  The shape of the peak of the diffraction intensity obtained by measuring the tilt angle is as shown in FIG. 5 (b) for Examples 1-3 and FIG. 5 (c) for Examples 4-6. It was. In Examples 1 to 3, | χ_max−χ_2nd | was 2 [°] or more and 10 [°] or less. In Examples 4 to 6, | χ_max_2−χ_2nd_2 | was 2 [°] or more and 8 [°] or less, and I {100} _min_2 / I {100} _max_2 was 0.5 or more. Moreover, the piezoelectric constant after the initial stage and durability test in Examples 1-6 is in the range of -120 to -160 [pm / V], respectively, and a piezoelectric constant equivalent to a general ceramic sintered body is obtained. It was confirmed.

  On the other hand, with respect to Comparative Example 1, the shape of the peak of the diffraction intensity obtained by measuring the tilt angle was as shown in FIG. The initial piezoelectric constant of Comparative Example 1 is lower than that of Examples 1-6. In the electromechanical transducer using the PZT film having the diffraction intensity peak shape shown in FIG. 5A, the effect of domain rotation cannot be sufficiently obtained as described above, so that the strain displacement is considered to be low. It is done.

  In the third embodiment, | χ_max−χ_2nd | is larger than the first and second embodiments. In the fourth embodiment, | χ_max_2−χ_2nd_2 | is larger than the fifth and sixth embodiments. Regarding the piezoelectric constant, in Examples 3 and 4, the initial piezoelectric constant is larger than that in the other examples. On the other hand, in Examples 3 and 4, the ratio of the decrease in the piezoelectric constant immediately after the durability test with respect to the initial piezoelectric constant ((initial piezoelectric constant−piezoelectric constant immediately after the durability test) / initial piezoelectric constant) It is slightly higher than in the example. It was confirmed that the durability of the electromechanical conversion element gradually decreased as | χ_max−χ_2nd | and | χ_max_2−χ_2nd_2 | were increased.

  However, in Examples 3 and 4, the piezoelectric constant immediately after the durability test is almost the same value in Examples 1 to 6. That is, if | χ_max−χ_2nd | of the PZT film is in the range of 2 [°] to 10 [°] and | χ_max_2−χ_2nd_2 | is in the range of 2 [°] to 8 [°], the initial piezoelectric constant is sufficiently large. It was confirmed that a good piezoelectric constant could be maintained even after the electromechanical transducer was operated continuously as an actuator.

  Here, a configuration example in which a plurality of liquid ejection heads each including a piezoelectric actuator having a PZT film are arranged will be described. FIG. 11 is a cross-sectional view showing a configuration example in which a plurality of liquid discharge heads including a piezoelectric actuator having the PZT film 406 shown in FIG. 1 are arranged. According to the configuration example of FIG. 11, a piezoelectric actuator as an electromechanical transducer can be formed with a performance equivalent to that of bulk ceramics by a simple manufacturing process. Furthermore, a plurality of liquid discharge heads can be collectively formed by performing etching removal from the back surface for forming a pressurized liquid chamber and joining a nozzle plate having nozzle holes. In FIG. 11, the liquid supply means, the flow path, and the fluid resistance are not shown.

  A liquid discharge head having the configuration shown in FIG. 11 was prepared using the electromechanical transducers prepared in Examples 1 to 6, and ink discharge was evaluated. In this evaluation, ink whose viscosity was adjusted to 5 [cp] was used, and an applied voltage of −10 to −30 [V] was applied with a simple Push waveform, and the state of ink ejection from the nozzle holes was confirmed. As a result, in any of Examples 1 to 6, it was confirmed that ink was successfully discharged from all the nozzle holes.

  Next, an ink jet recording apparatus as an image forming apparatus (droplet discharge apparatus) equipped with a droplet discharge head according to an embodiment of the present invention will be described.

  FIG. 12 is a perspective view showing an example of the ink jet recording apparatus according to the present embodiment, and FIG. 13 is an explanatory view of the mechanism portion of the ink jet recording apparatus as viewed from the side. The ink jet recording apparatus of this embodiment houses a printing mechanism 82 and the like inside a recording apparatus main body 81. The print mechanism unit 82 includes a carriage movable in the main scanning direction, an ink cartridge 95 as a liquid cartridge for supplying ink, which is a liquid for image formation, to a droplet discharge head 94 mounted on the carriage, and the like. . Further, a paper feed cassette (or a paper feed tray) 84 on which a large number of sheets 83 as recording media can be loaded from the front side can be detachably attached to the lower part of the apparatus main body 81. Further, the manual feed tray 85 for manually feeding the paper 83 can be turned over. Then, the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and after a required image is recorded by the printing mechanism unit 82, the paper is discharged to a paper discharge tray 86 mounted on the rear side.

  The printing mechanism 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown). A plurality of droplet discharge heads 94 are mounted on the carriage 93 such that a plurality of nozzles as ink discharge ports are arranged in a direction crossing the main scanning direction and the droplet discharge direction is directed downward. The plurality of droplet discharge heads 94 are heads (inkjet heads) that discharge droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). In addition, each ink cartridge 95 for supplying liquid (ink) of each color to the droplet discharge head 94 is replaceably mounted on the carriage 93.

  The ink cartridge 95 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside. The liquid (ink) supplied to the droplet discharge head 94 is maintained at a slight negative pressure by the capillary force of the porous body. Further, in this embodiment, four droplet discharge heads 94 are used corresponding to each color, but one droplet discharge head having a plurality of nozzles that discharge droplets of each color may be used.

  Here, the carriage 93 is slidably fitted to the main guide rod 91 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 92 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is stretched between a driving pulley 98 and a driven pulley 99 that are rotationally driven by a main scanning motor 97. The timing belt 100 is fixed to the carriage 93, and the carriage 93 is reciprocated by forward and reverse rotation of the main scanning motor 97.

  On the other hand, in order to convey the sheet 83 set in the sheet feeding cassette 84 to the lower side of the head 94, a sheet feeding roller 101, a friction pad 102, a guide member 103, a conveying roller 104, and a leading end roller 106 are provided. Yes. The paper feed roller 101 and the friction pad 102 separate and feed the paper 83 from the paper feed cassette 84, and the guide member 103 guides the paper 83. Further, the conveyance roller 104 inverts and conveys the fed paper 83. The leading end roller 106 defines the feeding roller 105 pressed against the circumferential surface of the conveying roller 104 and the feed angle of the sheet 83 from the conveying roller 104. The transport roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

  A printing receiving member 109, which is a paper guide member for guiding the paper 83 sent out from the transport roller 104 corresponding to the movement range of the carriage 93 in the main scanning direction, is provided below the droplet discharge head 94. Yes. On the downstream side of the printing receiving member 109 in the sheet conveyance direction, a conveyance roller 111 and a spur 112 that are rotationally driven to send the sheet 83 in the sheet discharge direction are provided. Further, a paper discharge roller 113 and a spur 114 for sending the paper 83 to the paper discharge tray 86, and guide members 115 and 116 for forming a paper discharge path are provided.

  During recording, the droplet discharge head 94 is driven according to the image signal while moving the carriage 93, thereby ejecting ink onto the stopped paper 83 to record one line, and transporting the paper 83 by a predetermined amount. After that, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

  Further, a recovery device 117 for recovering the ejection failure of the droplet ejection head 94 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 93. The recovery device 117 includes a cap unit, a suction unit, and a cleaning unit. While waiting for printing, the carriage 93 is moved to the recovery device 117 side, and the droplet discharge head 94 is capped by the capping means, and the nozzle as the discharge port is kept in a wet state to prevent discharge failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  When a discharge failure occurs, the discharge port (nozzle) of the head 94 is sealed by the capping unit, and bubbles and the like are sucked out from the discharge port by the suction unit through the tube. As a result, the ink, dust, etc. adhering to the ejection port surface are removed by the cleaning means, and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  As described above, this ink jet recording apparatus is equipped with the droplet discharge head manufactured in the above-described embodiment and Examples 1 to 6 of the present invention. Therefore, there is no ink droplet ejection failure due to the diaphragm drive failure, stable ink droplet ejection characteristics are obtained, and image quality is improved.

  In the present embodiment, in the PZT film preferentially oriented on the {100} plane, the diffraction intensity peak corresponding to the {100} plane out of the diffraction intensity peaks obtained by measurement by the θ-2θ method is The measurement was performed by swinging the tilt angle at the maximum position (2θ). Using the diffraction intensity curve obtained as an example, it has been described that the strain displacement of the electromechanical transducer element can be increased when the peak shape has the above-described characteristics. However, this is not limited to this example. The same applies to an electromechanical conversion film having a perovskite crystal structure preferentially oriented in the {n00} plane (n is a positive integer). In other words, the tilt angle is measured at a position (2θ) at which the diffraction intensity peak corresponding to the {N00} plane (N is a positive integer) parallel to the {n00} plane of this film is maximum. If the peak shape of the diffraction intensity obtained in step 1 has the above-described characteristics, the strain displacement of the electromechanical transducer can be increased.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A lower electrode such as the first electrode 405 formed directly or indirectly on the substrate or the base film, and a PZT film 406 formed on the lower electrode and preferentially oriented on the {n00} plane, where n is a positive integer. In an electromechanical conversion element comprising an electromechanical conversion film made of a piezoelectric material having a perovskite crystal structure, such as a second electrode 407 formed on the electromechanical conversion film, the electromechanical conversion film comprises: The position where the diffraction intensity is maximum at the diffraction intensity peak corresponding to the {N00} plane, where N is a positive integer among the diffraction intensity peaks obtained by the X-ray diffraction measurement by the θ-2θ method (2θ) Thus, the peak shape of the diffraction intensity obtained by the measurement by swinging the tilt angle (χ) in the range of ± 15 [°] is a shape having two or more bent points.
When the inclination of the crystal plane was large with respect to the substrate surface of the electromechanical conversion film, a shape having a peak of the diffraction intensity having two or more bent points was obtained. On the other hand, when the inclination of the crystal plane is small with respect to the substrate surface of the electromechanical conversion film, a shape having two or more bent points in the diffraction intensity peak was not obtained. Therefore, in the electromechanical conversion film in which the shape of the peak of the diffraction intensity has two or more bent points, it is considered that the inclination of the crystal plane is large with respect to the substrate surface of the film. When the inclination of the crystal plane with respect to the substrate surface of the electromechanical conversion film is large, slight distortion occurs in the crystal structure of the electromechanical conversion film. It has been empirically known that when this distortion occurs, the effect of domain rotation is enhanced in the electromechanical conversion film. By enhancing the effect on the domain rotation, the strain displacement of the electromechanical transducer using the electromechanical transducer film can be increased.

(Aspect B)
A lower electrode such as a first electrode 405 formed directly or indirectly on a substrate or a base film, and a perovskite crystal structure such as a PZT film 406 formed on the lower electrode and preferentially oriented in the {100} plane In an electromechanical conversion element comprising an electromechanical conversion film made of a piezoelectric body and an upper electrode such as the second electrode 407 formed on the electromechanical conversion film, the electromechanical conversion film has an X-ray diffraction θ−. Obtained when the tilt angle (χ) is swung in the range of ± 15 [°] at the position (2θ) where the diffraction intensity is maximum at the diffraction intensity peak corresponding to the {100} plane in the measurement by the 2θ method. When the peak shape of the diffraction intensity is a shape having two bent points, of the bent points, the position of the point with the higher diffraction intensity is χ_max and the position of the other point is χ_2nd , | Χ_m x-χ_2nd | is 2 [°] or more and 10 [°] or less When | χ_max-χ_2nd | is smaller than the lower limit value (2 [°]) defined above, the electromechanical conversion is performed. The distortion of the crystal structure in the film is reduced. For this reason, the effect of domain rotation becomes small, and sufficient strain displacement cannot be obtained in the electromechanical transducer. Further, when | χ_max−χ_2nd | is larger than the upper limit value (10 [°]) defined above, distortion of the crystal structure of the electromechanical conversion film is increased, and strain displacement due to domain rotation can be greatly increased. However, if the distortion of the crystal structure of the electromechanical conversion film becomes very large, there is a high possibility that defects such as cracks will occur in the electromechanical conversion film, and the electromechanical conversion element is continuously driven as a piezoelectric actuator. Sometimes, the strain displacement after driving decreases with respect to the initial strain displacement. By setting | χ_max−χ_2nd | within the above range, the initial strain displacement of the electromechanical transducer can be sufficiently increased, and the strain displacement can be prevented from greatly decreasing even after continuous driving.

(Aspect C)
An electromechanical conversion film comprising a lower electrode such as a first electrode 405 formed directly or indirectly on a substrate or a base film, and a piezoelectric material having a perovskite crystal structure such as a PZT film 406 formed on the lower electrode. And an upper electrode such as the second electrode 407 formed on the electromechanical conversion film, in which the electromechanical conversion film is measured by {100 The shape of the diffraction intensity peak obtained when the tilt angle (χ) is swung in the range of ± 15 [°] at the position (2θ) where the diffraction intensity is maximum at the diffraction intensity peak corresponding to the plane is two. The shape has the above maximum points.
In the electromechanical conversion film in which the peak shape of the diffraction intensity has two or more maximum points, it is considered that the inclination of the crystal plane is large with respect to the substrate surface of the film. When the inclination of the crystal plane with respect to the substrate surface of the electromechanical conversion film is large, slight distortion occurs in the crystal structure of the electromechanical conversion film. It has been empirically known that when this distortion occurs, the effect of domain rotation is enhanced in the electromechanical conversion film. By enhancing the effect on the domain rotation, the strain displacement of the electromechanical transducer using the electromechanical transducer film can be increased.

(Aspect D)
In aspect C, the electromechanical conversion film has two local maximum points, and the tilt angle at the point where the diffraction intensity is larger among the two local maximum points is χ_max, and the tilt angle at the other point Is χ_2nd, | χ_max_2−χ_2nd_2 | is 2 [°] or more and 8 [°] or less.
When | χ_max_2−χ_2nd_2 | is smaller than the lower limit value (2 [°]) defined above, the distortion of the crystal structure in the electromechanical conversion film is reduced. For this reason, the effect of domain rotation becomes small, and sufficient strain displacement cannot be obtained in the electromechanical transducer. Further, when | χ_max_2−χ_2nd_2 | is larger than the upper limit value (20 [°]) defined above, the distortion of the crystal structure of the electromechanical conversion film is increased, and the strain displacement due to domain rotation can be greatly increased. However, if the distortion of the crystal structure of the electromechanical conversion film becomes very large, there is a high possibility that defects such as cracks will occur in the electromechanical conversion film, and the electromechanical conversion element is continuously driven as a piezoelectric actuator. Sometimes, the strain displacement after driving decreases with respect to the initial strain displacement. By setting | χ_max_2−χ_2nd_2 | within the above range, the initial strain displacement of the electromechanical transducer can be sufficiently increased, and the strain displacement can be prevented from greatly decreasing even after continuous driving.

(Aspect E)
In aspect E, the electromechanical conversion film has I {100} _max_2, a local minimum point sandwiched between the local maximum points at the point where the diffraction intensity is larger among the local maximum points at two locations. I {100} _min_2 / I {100} _max_2 is 0.5 or more, where I {100} _min_2 / I {100} _max_2 is I {100} _min_2 / I {100} _max_2 When the value is smaller than the lower limit (0.3) defined above, the crystal structure of the electromechanical conversion film is locally distorted. When the crystal lattice is locally distorted, the strain displacement of the electromechanical transducer using the electromechanical transducer film is locally increased due to the effect of domain rotation. For this reason, when the electromechanical conversion element is continuously driven as a piezoelectric actuator, there is a high possibility that defects such as cracks occur in the electromechanical conversion film. When such a defect occurs due to continuous driving, the strain displacement after driving decreases with respect to the initial strain displacement. By setting I {100} _min_2 / I {100} _max_2 in the above range, it is possible to prevent the strain displacement from greatly decreasing even after continuous driving.

(Aspect F)
In any one of the aspects B to E, the half width of the peak of diffraction intensity obtained when the electromechanical conversion film swings the tilt angle (χ) in a range of ± 15 [°] is 6 [°]. The angle is 16 [°] or less.
When the full width at half maximum is smaller than the lower limit (6 [°]), the distortion of the crystal structure of the PZT film is reduced, so that the effect of 90 [°] domain rotation is reduced and sufficient strain displacement is obtained in the electromechanical transducer. I can't. Further, when the half width is larger than the upper limit (16 [°]), the distortion of the crystal structure of the electromechanical conversion film becomes very large. Therefore, the initial distortion of the electromechanical conversion element is caused by the effect of domain rotation. The displacement becomes very large. However, when the electromechanical conversion element is continuously driven as a piezoelectric actuator, if the distortion of the crystal structure of the electromechanical conversion film is very large, a defect such as a crack is likely to occur. In this case, the strain displacement after driving is reduced with respect to the initial strain displacement. By setting the full width at half maximum in the above range, the initial strain displacement of the electromechanical transducer can be sufficiently increased, and the strain displacement can be prevented from greatly decreasing even after continuous driving.

(Aspect G)
In any one of the aspects A to F, the electromechanical conversion film is made of lead zirconate titanate (PZT), and the composition ratio of titanium (Ti) to zinc (Zr) in the electromechanical conversion film (Ti / (Zr + Ti )) Is 0.45 or more and 0.55 or less.
If the composition ratio of Zr and Ti is smaller than the lower limit (0.45), the effect of domain rotation described later is not sufficient, so that sufficient strain displacement of the electromechanical transducer cannot be ensured. In addition, when the composition ratio of Zr and Ti is larger than the upper limit (0.55), the piezoelectric effect is not sufficient, so that sufficient strain displacement of the electromechanical transducer cannot be ensured. By setting the composition ratio of Zr and Ti within the above range, the initial strain displacement of the electromechanical transducer can be sufficiently increased.

(Aspect H)
In a droplet discharge head comprising a nozzle that discharges a droplet, a pressure chamber that communicates with the nozzle, and a pressure generation means that generates a pressure in the liquid in the pressure chamber, the pressure generation means may include an aspect A The electromechanical transducer of any one of -G was provided.

(Aspect I)
A droplet discharge head of aspect H was provided.

94 Liquid droplet ejection head 401 Substrate 402 Vibration plate 403 Nozzle plate 404 Pressurized liquid chamber 405 First electrode 406 PZT film 407 Second electrode 408 First oxide layer 409 Second oxide layer

JP 2008-192868 A

Claims (9)

A lower electrode directly or indirectly formed on the base plate or base film,
An electromechanical conversion film made of a piezoelectric material formed on the lower electrode and having a perovskite crystal structure preferentially oriented in the {100} plane;
In an electromechanical conversion element comprising an upper electrode formed on the electromechanical conversion film,
When the electromechanical conversion film is measured by the X-ray diffraction θ-2θ method, the tilt angle (χ) is ±± at the position (2θ) where the diffraction intensity is maximum at the peak of the diffraction intensity corresponding to the {100} plane. The position of the peak of the diffraction intensity obtained when shaken in the range of 15 [°] has a shape having two bent points, and the position of the point having the larger diffraction intensity among the bent points. Χ_max, and the position of the other point is χ_2nd, | χ_max−χ_2nd | is 2 [°] or more and 10 [°] or less. A lower electrode formed directly or indirectly on a substrate or a base film;
An electromechanical conversion film made of a piezoelectric material having a perovskite crystal structure formed on the lower electrode;
In an electromechanical conversion element comprising an upper electrode formed on the electromechanical conversion film,
When the electromechanical conversion film is measured by the X-ray diffraction θ-2θ method, the tilt angle (χ) is ±± at the position (2θ) where the diffraction intensity is maximum at the peak of the diffraction intensity corresponding to the {100} plane. 15 [°] der a peak shape of the diffraction intensity obtained is in the shape having a local maximum point of the two positions when shaken in the range is,
Of the two local maximum points, when the tilt angle at the point with the higher diffraction intensity is χ_max and the tilt angle at the other point is χ_2nd, | χ_max_2−χ_2nd_2 | is 2 [°] or more and 8 [ °] An electromechanical transducer having the following characteristics. The electromechanical transducer according to claim 2 ,
The electromechanical conversion film has I {100} _max_2 as the diffraction intensity at the point where the diffraction intensity is larger among the two maximum points, and the diffraction intensity at the minimum point sandwiched between the two maximum points. I {100} _min_2 / I {100} _max_2 is 0.5 or more, where I {100} _min_2 is an electromechanical conversion element. In the electromechanical transducer according to any one of claims 1 to 3 ,
In the electromechanical conversion film, the half width of the peak of diffraction intensity obtained when the tilt angle (χ) is swung in the range of ± 15 [°] is 6 [°] or more and 16 [°] or less. An electromechanical conversion element characterized by being a thing.   A lower electrode formed directly or indirectly on a substrate or a base film;
An electromechanical conversion film made of a piezoelectric material having a perovskite crystal structure formed on the lower electrode;
In an electromechanical conversion element comprising an upper electrode formed on the electromechanical conversion film,
When the electromechanical conversion film is measured by the X-ray diffraction θ-2θ method, the tilt angle (χ) is ±± at the position (2θ) where the diffraction intensity is maximum at the peak of the diffraction intensity corresponding to the {100} plane. The peak shape of the diffraction intensity obtained when shaken in the range of 15 [°] is a shape having two local maximum points,
In the electromechanical conversion film, the half width of the peak of diffraction intensity obtained when the tilt angle (χ) is swung in the range of ± 15 [°] is 6 [°] or more and 16 [°] or less. An electromechanical conversion element characterized by being a thing. The electromechanical transducer according to any one of claims 1 to 5 ,
The electromechanical conversion film is made of lead zirconate titanate (PZT), and the composition ratio (Ti / (Zr + Ti)) of titanium (Ti) to zinc (Zr) in the electromechanical conversion film is 0.45 or more and 0.55. An electromechanical transducer having the following characteristics. A nozzle for discharging droplets;
A pressurizing chamber communicating with the nozzle;
In a droplet discharge head comprising pressure generating means for generating pressure in the liquid in the pressurizing chamber,
Wherein the pressure generating means, the droplet discharge head is characterized by comprising any one of the electromechanical transducer of claims 1 to 6. An image forming apparatus comprising the droplet discharge head according to claim 7 .   A droplet discharge apparatus comprising the droplet discharge head according to claim 7.

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