JP7351106B2 - Electromechanical transducer element, liquid ejection head, liquid ejection unit, liquid ejection device, and piezoelectric device - Google Patents

Description

The present invention relates to an electromechanical transducer, a liquid ejection head, a liquid ejection unit, a liquid ejection device, and a piezoelectric device.

Inkjet recording devices and liquid ejection heads used in image recording devices or image forming devices such as printers, facsimiles, and copiers have a nozzle that ejects ink droplets and a pressure chamber (ink flow path, (also referred to as a pressurized liquid chamber, pressure chamber, discharge chamber, liquid chamber, etc.) and an energy generating means (for example, a piezoelectric element as an electromechanical transducer) for pressurizing the ink in the pressurized chamber. It has been known. Then, ink droplets are ejected from the nozzle by pressurizing the ink in the pressurizing chamber with the energy generated by the energy generating means.

As liquid ejection heads, there are known ones that use an actuator in a longitudinal vibration mode that expands and contracts in the axial direction of an electromechanical transducer (piezoelectric element), and those that use an actuator in a flexural vibration mode.
For a flexural vibration mode actuator, for example, a uniform electromechanical transducer film (also referred to as a piezoelectric film, piezoelectric material layer, etc.) is formed over the entire surface of the diaphragm using a film-forming technique, and this electromechanical transducer film is formed using a lithography method. It is known that the electromechanical transducer is cut into shapes corresponding to the pressure generating chambers, and an electromechanical transducer is formed independently in each pressure generating chamber.

It is known that conventional electromechanical transducers have reliability problems in high humidity environments. This is because the electromechanical conversion layer deteriorates due to moisture in the environment, and leakage current increases and dielectric breakdown occurs, leading to a decline in the conversion characteristics of the electromechanical conversion element and even failure. It may lead to.

To address these problems, Patent Document 1 discloses a method for reducing stress concentration near the boundary of the pressure generating chamber to prevent damage to the upper electrode, and also for preventing leakage current between the upper and lower electrodes that sandwich the piezoelectric material layer. The inkjet recording head is equipped with a piezoelectric vibrator consisting of a lower electrode, a piezoelectric layer, and an upper electrode. , the upper electrode is formed independently in a region facing the pressure generation chamber, and only the region from the peripheral edge of the surface of the upper electrode to the side surface of the piezoelectric layer is an insulator so that the area other than the peripheral surface of the upper electrode is exposed. Inkjet recording heads have been proposed that are covered with layers.

Further, Patent Document 2 discloses a technique for improving the insulation reliability of a piezoelectric element, which includes a piezoelectric body sandwiched between first and second electrodes and containing a lead compound, and a piezoelectric body that is sandwiched between first and second electrodes, and that It consists of an aggregate composed of a plurality of columnar crystals facing each other, and zirconium oxide exists at the grain boundaries between the crystals, and the composition ratio of the zirconium element at the grain boundaries is higher than that of the lead element at the grain boundaries. Piezoelectric elements larger than

However, in the technique of Patent Document 1, the displacement of the piezoelectric layer covered with the insulating layer is limited by the rigidity of the insulating layer, and the characteristics of the piezoelectric element may deteriorate. Furthermore, in the technique of Patent Document 2, the presence of zirconium oxide, which is a non-piezoelectric substance, at the grain boundaries corresponding to the leak path of the piezoelectric element may deteriorate the characteristics of the piezoelectric element.

By the way, Patent Document 2 describes the principle by which dielectric breakdown occurs when a high voltage is applied in a humid environment, stating that lead oxide present at the grain boundaries in a piezoelectric material undergoes an electrochemical reaction with moisture. It has been stated that the main cause is that the deterioration occurs due to deterioration.

Furthermore, in order to suppress the occurrence of dielectric breakdown, it is important to control the amount of leakage current, and it is effective to control the content of components that become leak sources.
Furthermore, in a high humidity environment, it is important to control the current flowing outside the electromechanical transducer membrane to prevent short circuits between the upper and lower electrodes.

Therefore, an object of the present invention is to provide a highly reliable electromechanical transducer that maintains electromechanical conversion characteristics even in a high humidity environment, can continue driving without failure, and has high reliability.

In order to solve the above problems, the electromechanical transducer of the present invention is made of a composite oxide having a perovskite structure containing at least Pb, Zr, and Ti , and has a film thickness of 1.0 μm to 3.0 μm. a mechanical transducer film, a pair of electrodes disposed with the electromechanical transducer film in between, and an insulating protective film covering the electromechanical transducer film and the pair of electrodes, In an environment where the Pb content is approximately uniform in the film thickness direction and the water vapor pressure is 300 kPa, the leakage current density at a DC voltage of 40 V measured between terminals electrically connected from the pair of electrodes is 4.2. ×10 ⁻⁶ A/cm ² or less.

According to the present invention, the present invention can provide a highly reliable electromechanical transducer that maintains electromechanical conversion characteristics even in a high humidity environment, and can continue driving without failure. .

1 is a cross-sectional view schematically showing an example of the configuration of an electromechanical transducer according to the present invention. 1 is a cross-sectional view (A) and a top view (B) showing an example of the configuration of an electromechanical transducer according to the present invention. 1 is a schematic diagram showing an example of the configuration of a polarization processing apparatus used for manufacturing an electromechanical transducer according to the present invention. It is a graph showing a PE hysteresis loop after polarization processing. 1 is a cross-sectional TEM image of an electromechanical transducer film of an electromechanical transducer according to the present invention. FIG. 2 is a schematic diagram showing a configuration example of a liquid ejection head. FIG. 2 is a schematic diagram showing a configuration example of a liquid ejection head. FIG. 1 is a schematic diagram showing an example of a liquid ejection unit according to the present invention. FIG. 7 is a schematic diagram showing another example of the liquid ejection unit according to the present invention. FIG. 7 is a schematic diagram showing another example of the liquid ejection unit according to the present invention. FIG. 7 is a schematic diagram showing another example of the liquid ejection unit according to the present invention. FIG. 1 is a schematic perspective view showing an example of a device that discharges liquid. FIG. 1 is a schematic cross-sectional view showing an example of a device for discharging liquid. 2 is a graph showing the Pb content in the thickness direction of the electromechanical conversion films in the electromechanical conversion elements of Examples 1 to 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An electromechanical transducer, a liquid ejection head, a liquid ejection unit, and a liquid ejecting device according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to the embodiments shown below, and may be modified within the scope of those skilled in the art, such as other embodiments, additions, modifications, deletions, etc. These are also included within the scope of the present invention as long as they exhibit the functions and effects of the present invention.

The electromechanical transducer according to the present invention can be applied to devices having a thin electromechanical transducer film made of a piezoelectric material, such as liquid ejection heads, motors, ultrasonic vibrators, piezoelectric sensors, ferroelectric memories, and power generation devices. It can be used for piezoelectric devices such as devices and speakers.

The piezoelectric body that constitutes the electromechanical transducer film is a material that has piezoelectric properties that deforms when voltage is applied.
The electromechanical transducer film of this embodiment is made of a composite oxide (for example, lead zirconate titanate (PZT)) having a perovskite structure containing at least Pb, Zr, and Ti.
When a driving voltage is applied to an electromechanical transducer having an electromechanical transducer film made of PZT, the vibration modes include, for example, a longitudinal vibration mode (push mode) accompanied by deformation in the film thickness direction due to the piezoelectric constant d33, and a piezoelectric constant d33. There is a transverse vibration mode (bend mode) accompanied by deflection deformation due to d31. Furthermore, there is also a shear mode that utilizes shear deformation of the membrane.

The electromechanical transducer having the electromechanical transducer film can be formed by directly manufacturing a pressurized liquid chamber and an electromechanical transducer on a Si substrate using, for example, a semiconductor process or MEMS (Micro Electro Mechanical Systems) technology. .
Thereby, the electromechanical transducer can be formed, for example, as a thin film piezoelectric actuator that generates pressure in a pressurizing chamber in a liquid ejection head.

FIG. 1 is a cross-sectional view showing an example of a schematic configuration of an electromechanical transducer.
In the example of FIG. 1, a substrate 13, a diaphragm 14, and an electromechanical transducer 20 are stacked, and the electromechanical transducer 20 is composed of a first electrode 15, an electromechanical transducer film 16, and a second electrode 17. There is.

FIG. 2 is a diagram showing an example of a configuration when the electromechanical transducer 20 of this embodiment is used as a piezoelectric actuator for a liquid ejection head or the like.
FIG. 2(A) is a cross-sectional view showing a schematic configuration example of an electromechanical transducer provided in a liquid ejection head, and FIG. 2(B) is a top view of the electromechanical transducer. FIG. 2(A) is a sectional view taken along line II in FIG. 2(B).

As shown in FIG. 2(B), a plurality of electromechanical transducers 20 are provided so as to be arranged in a predetermined direction. A plurality of electromechanical transducers 20 are formed on a substrate 13 with a diaphragm 14 in between.

A first insulating protective film 21 as an interlayer insulating film is provided in a predetermined area on the electromechanical conversion film 16 and the pair of electrodes (first electrode 15, second electrode 17).
A contact hole 25 is formed in the first insulating protective film 21 so that the first electrode 15 and the second electrode 17 can be electrically connected to other electrodes.
In FIG. 2, the first electrode 15 is electrically connected to a third electrode (common lead wiring) 27, and the second electrode 17 is electrically connected to a fourth electrode (common lead wiring) 28. At this time, the first electrode 15 and the third electrode 27 are used as common electrodes, the second electrode 17 and the fourth electrode 28 are used as individual electrodes, and a second insulating protective film 22 is formed to protect them. .

A portion of the second insulating protective film 22 has an opening, a portion of the individual electrode is configured as an individual electrode pad 24, and a portion of the common electrode is configured as a common electrode pad 23.
Note that the first insulating protective film 21 and the second insulating protective film 22 are omitted in FIG. 2(B).

The first insulating protective film 21 and the second insulating protective film 22 can be made of inorganic compounds such as aluminum oxide, silicon oxide, aluminum nitride, and silicon nitride.

In the examples of FIGS. 1 and 2, the first electrode (lower electrode) 15 is a common electrode and the second electrode (upper electrode) 17 is an individual electrode, but the upper electrode and the lower electrode will be described later. As shown in the configuration of FIG. 6, either can be a common electrode or an individual electrode, and can be changed as appropriate depending on the purpose of the electrode.

[substrate]
Although the substrate 13 is not particularly limited, it is preferable to use a silicon single crystal substrate, and the thickness is preferably 100 to 600 μm. Three types of plane orientations can be used: (100), (110), and (111).Generally, (100) and (111) are used, and in the present invention, (100) is used. A single crystal substrate with a plane orientation is preferable.

Furthermore, when forming a pressurizing chamber 18 in a liquid ejection head (see FIG. 6) described later, a silicon single crystal substrate is processed using etching, and anisotropic etching is used as the etching method in this case. This is common. Anisotropic etching utilizes the property that the etching rate differs depending on the plane orientation of the crystal structure. For example, in anisotropic etching performed by immersion in an alkaline solution such as KOH, the etching rate for the (111) plane is about 1/400 of that for the (100) plane. Therefore, in the plane orientation (100), it is possible to fabricate a structure with an inclination of about 54°, while in the plane orientation (110), deep grooves can be cut, which allows for a higher arrangement density while maintaining more rigidity. can do.
In the present invention, it is also possible to use a single crystal substrate with a (110) plane orientation, but in this case it should be noted that SiO ₂ that can be used as a mask material will also be etched.

Note that the width (length in the short direction) of the pressurizing chamber 18 is preferably 50 μm or more and 70 μm or less. Within this range, ejection performance at high frequencies can be ensured.

[Vibration plate]
The diaphragm 14 is deformed and displaced by the force generated by the electromechanical transducer film 16 in a liquid ejection head to be described later, and causes the ink droplets in the pressurized chamber 18 to be ejected. Therefore, it is preferable that the diaphragm 14 has a predetermined strength.

In particular, in order to ensure ejection performance at high frequencies, it is necessary to increase the rigidity of the diaphragm 14 together with the electromechanical conversion film 16 and the insulating protective film _. , SiN (Si ₃ N ₄ ), and poly-Si, the film thickness is preferably 1 μm to 3 μm, and the Young's modulus is preferably 75 GPa to 95 GPa.

Examples of the material for the diaphragm 14 include Si, SiO ₂ , and Si ₃ N ₄ made by a CVD (Chemical Vapor Deposition) method, and it is preferable that the diaphragm 14 is made of a plurality of layers as described above.

Further, it is preferable to select a material having a coefficient of linear expansion close to that of the first electrode 15 and the electromechanical conversion film 16. In particular, since the electromechanical transducer membrane 16 uses PZT (lead zirconate titanate) as a general material, the material of the diaphragm 14 has a linear expansion coefficient close to 8×10 ^-6 (1/K). A material having a linear expansion coefficient of 5×10 ⁻⁶ to 10×10 ⁻⁶ is preferable, and a material having a linear expansion coefficient of 7×10 ⁻⁶ to 9×10 ⁻⁶ is more preferable.
Specific materials include aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds thereof. It can be produced using a spin coater or the like using a sol-gel method.

As mentioned above, the thickness of the diaphragm 14 is preferably 1 μm to 3 μm, more preferably 1.5 μm to 2.5 μm. This facilitates processing of the pressurizing chamber 18 and further facilitates deformation of the diaphragm.

[electrode]
The first electrode 15 and the second electrode 17 (lower electrode and upper electrode) can be composed of a metal film or an oxide electrode film, and in particular can be composed of a laminate of a metal film and an oxide electrode film. Good too.

The first electrode 15 and the second electrode 17 (lower electrode and upper electrode) may each have a metal layer with sufficiently low electrical resistance.
Platinum, which has high heat resistance and low reactivity, can be used as the metal material for the metal layer. However, since it may not have sufficient barrier properties against lead, platinum group elements such as iridium or platinum-rhodium, or films of alloys thereof may be used.

Furthermore, when platinum is used, it has poor adhesion to the base (particularly SiO ₂ ), so it is necessary to first laminate Ti, TiO ₂ , Ta, Ta ₂ O ₅ , Ta ₃ N ₅ , etc. as an intermediate layer. is preferred. As a manufacturing method, a sputtering method, a vacuum evaporation method, or the like can be used.
The film thickness is preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm.

Furthermore, the first electrode 15 and the second electrode 17 (lower electrode and upper electrode) may have a conductive oxide electrode layer at the interface with the electromechanical conversion film 16.
As a material for the oxide electrode layer, for example, SrRuO ₃ or LaNiO ₃ can be used. The method for forming the oxide electrode film is not particularly limited either, but it can be formed by, for example, a sputtering method.

Since the oxide electrode layer constituting the lower electrode also influences the orientation control of the electromechanical conversion film 16 formed thereon, the material selected differs depending on the direction in which the orientation is desired to be prioritized.

In this embodiment, in order to preferentially orient the electromechanical transducer film 16 in the (100) plane, a seed layer made of LaNiO ₃ , TiO ₂ or PbTiO ₃ is formed on the first electrode 15 as an oxide electrode layer. However, after that, the electromechanical conversion film 16 may be formed.

SrRuO ₃ can be used as the oxide electrode layer constituting the upper electrode.
The thickness of the oxide electrode layer is preferably 20 nm to 80 nm, more preferably 30 nm to 50 nm. As a result, good characteristics can be obtained regarding the amount of initial deformation (amount of surface displacement), the amount of deformation over time (amount of surface displacement), and the amount of current leakage.

The material of the electromechanical conversion film 16 can be an oxide containing Pb (for example, PZT). PZT is a solid solution of lead zirconate (PbZrO ₃ ) and titanic acid (PbTiO ₃ ), and its properties vary depending on their ratio.
The composition that generally exhibits excellent piezoelectric properties is a ratio of PbZrO ₃ and PbTiO ₃ of 53:47, and the chemical formula is Pb(Zr _0.53 , Ti _0.47 )O ₃ , which is generally PZT. (53/47) is also indicated.

In this embodiment, it is preferable to use PZT as the electromechanical transducer film 16 and to preferentially align the (100) plane of PZT.
In this case, the composition ratio of Zr/Ti: Ti/(Zr+Ti) is preferably from 0.45 (45%) to 0.55 (55%), and from 0.48 (48%) to 0.52 (52%). ) The following are more preferable.

The crystal orientation degree ρ(hkl) of the (hkl) plane of the electromechanical conversion film 16 is
ρ(hkl)=I(hkl)/ΣI(hkl)
[However, ρ(hkl): degree of orientation of (hkl) plane orientation, I(hkl): peak intensity of arbitrary orientation, ΣI(hkl): sum of each peak intensity].
I(hkl) is calculated based on the ratio of the peak intensity of each orientation when the sum of the peak intensities obtained by θ-2θ measurement of the electromechanical transducer film 16 using X-ray diffraction is set to 1 (100 ) The degree of orientation is preferably 0.75 or more, more preferably 0.85 or more. When the degree of orientation of the (100) orientation is 0.75 or more, sufficient piezoelectric strain can be obtained and a sufficient amount of deformation can be ensured.

When these materials are expressed as a general formula, they are described by ABO ₃ , and include composite oxides whose main components are A=Pb, Ba, Sr, B=Ti, Zr, Sn, Ni, Zn, Mg, and Nb.
Specific descriptions include (Pb _1-x ,Bax)(Zr,Ti)O ₃ , (Pb _1-x ,Sr _x )(Zr,Ti)O ₃ , etc., which is the Pb of the A site. This is an example where part of is replaced with Ba or Sr. Such substitution is possible as long as it is a divalent element, and its effect is to reduce property deterioration due to lead evaporation during heat treatment.

The electromechanical transducer film 16 may be fabricated using, for example, a sputtering method or a sol-gel method using a spin coater or the like. In that case, patterning is required, so a desired pattern is obtained by photolithography etching or the like.

In addition, when producing PZT by the sol-gel method, the PZT precursor solution is prepared by using lead acetate, zirconium alkoxide, and titanium alkoxide compounds as starting materials and dissolving them in methoxyethanol as a common solvent to obtain a uniform solution. It can be made. Since metal alkoxide compounds are easily hydrolyzed by moisture in the atmosphere, an appropriate amount of a stabilizer such as acetylacetone, acetic acid, or diethanolamine may be added to the precursor solution as a stabilizer.

Further, when obtaining a PZT film on the entire surface of the diaphragm 14, it can be 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. The transformation from a coating film to a crystallized film is accompanied by volumetric shrinkage, so in order to obtain a crack-free film, the precursor concentration is adjusted so that a film thickness of 100 nm or less can be obtained in one step, and the PZT film is produced. It is preferable to do so.

The thickness of the electromechanical conversion film 16 is preferably 1.0 μm to 3.0 μm, more preferably 1.5 μm to 2.5 μm. This provides sufficient deformation.

Next, a method of polarizing the electromechanical transducer film 16 in the manufacturing process of the electromechanical transducer 20 having the above structure will be described.
FIG. 3(A) is a perspective view showing a schematic configuration example of a polarization processing apparatus 40 used for polarization processing of an electromechanical transducer film in the manufacturing process of the electromechanical transducer element according to the embodiment, and FIG. 3(B) is FIG.

As shown in FIGS. 3(A) and 3(B), the polarization processing device 40 includes a corona electrode 41, a grid electrode 42, and a stage 43 having a counter electrode.
Further, the stage 43 may be provided with a temperature control function so that the electromechanical transducer 20 can be heated. Although the heating temperature at this time is not particularly limited, it may be configured such that it can be heated up to a maximum of 350°C. Further, a ground wire 44 is connected to the stage 43 on which the sample is placed so that electric charges can easily flow to the sample (electromechanical transducer 20) to be subjected to discharge treatment.

The corona electrode 41 and the grid electrode 42 are connected to a corona electrode power source 411 and a grid electrode power source 421, respectively.
The corona electrode 41 may have a wire shape, for example.
The grid electrode 42 may be configured to be mesh-processed so that when a high voltage is applied to the corona electrode 41, ions, charges, etc. generated by corona discharge efficiently fall onto the sample stage below.

The magnitude of the voltage applied to each of the corona electrode 41 and the grid electrode 42 and the distance between the sample and each electrode are not particularly limited. For example, in order to sufficiently polarize the sample, the magnitude of the voltage applied to each of the corona electrode 41 and the grid electrode 42 and the distance between the sample and each electrode are adjusted depending on the sample, and the corona discharge It is also possible to set the strength of the character.

The state of the polarization process can be determined from the PE hysteresis loop.
As shown in Figure 4, the hysteresis loop was measured by applying an electric field strength of ±150 kV/cm. The amount of polarization at cm is defined as residual polarization Pr. The value of Pr-Pini is defined as the polarizability, and it is judged that the smaller the polarizability, the more advanced the polarization is.
By performing the polarization process, Pini increases as shown in FIG. 4, and as the polarization process progresses, the value of the polarization amount difference Pr-Pini decreases.

The polarizability is preferably 10 μC/cm ² or less, more preferably 5 μC/cm ² or less, and when this is satisfied, it can be said that the polarization treatment has been sufficiently performed.

A desired polarizability Pr-Pini can be achieved by adjusting the voltages of the corona and grid electrodes, the distances between the sample stage and the corona and grid electrodes, etc. in the apparatus shown in FIG.

As described above, the electromechanical transducer 20 according to the present embodiment includes the electromechanical transducer 16 made of a composite oxide having a perovskite structure containing at least Pb, Zr, and Ti; Insulating protection that covers a pair of electrodes (first electrode 15 and second electrode 17) arranged on both sides, and electromechanical conversion film 16 and a pair of electrodes (first electrode 15 and second electrode 17). It has a membrane.

In order for the electromechanical conversion element 20 to maintain its electromechanical conversion characteristics even in a high humidity environment and to be able to continue driving without failure, the amount of leakage current must be set to a predetermined amount or less to suppress the occurrence of dielectric breakdown. It is necessary to.
In controlling the amount of leakage current in the electromechanical transducer 20, it is most important to control the amount of leakage current of the electromechanical conversion film 16 itself flowing into the electromechanical conversion film 16. It is effective to adjust the amount of Pb. In addition, particularly in a high humidity environment, controlling the amount of current flowing outside the electromechanical transducer membrane 16 is also important in order to prevent short circuits between the pair of electrodes (first electrode 15 and second electrode 17).

In order to solve these problems, the electromechanical transducer 20 of the present embodiment has an electromechanical transducer film 16 that has a substantially uniform Pb content in the film thickness direction, and can be used in an environment where the water vapor pressure (also referred to as water vapor partial pressure) is 300 kPa. In this case, the leakage current density measured between terminals electrically connected from a pair of electrodes (first electrode 15 and second electrode 17) is 4.2 × 10 ^-6 A/cm ² or less. The electromechanical conversion characteristics are maintained even in high humidity environments, and the drive can continue without failure.

In this embodiment, "the Pb content is substantially uniform in the film thickness direction" in the electromechanical conversion film means that the Pb content measured in the film thickness direction is within ±4% of the average value. (This means that the difference in measured values is within 8%).
Here, "Pb content" is the ratio of Pb to the total amount of other components measured by compositional analysis, and in the case of a PZT film, the ratio of Pb content to the sum of Zr and Ti contents (atomic numerical ratio).
Specifically, the amount of Pb, Zr, and Ti measured at any location on the electromechanical conversion film 16 is a value calculated by the amount of Pb/(the amount of Zr+the amount of Ti).

Note that the average Pb content in the electromechanical conversion film 16 is preferably 100 to 110% of the sum of the Zr and Ti contents. When the amount of Pb in the electromechanical conversion film 16 is within the above range, leakage current can be made sufficiently small.
Here, the "average Pb content" is calculated as the average Pb amount/(average Zr amount + average Ti amount) for the amounts of Pb, Zr, and Ti obtained at multiple measurement points of the electromechanical conversion film 16. is the value to be used.

Further, the electromechanical conversion film 16 has a plurality of particles and grain boundaries existing between the plurality of particles, and the Pb content in the region including the crystal grain boundaries is smaller than the Pb content inside the plurality of particles. is preferably 105% or less. That is, it is preferable that the Pb content in the crystal particles and the Pb content in the amorphous particles are at the same level.

For compositional analysis of PZT, for example, the average Pb content can be analyzed by ICP (Inductively Coupled Plasma) emission spectrometry, and the crystal grains and grain boundaries can be analyzed by TEM-EDS (Transmission Electron Microscopy-Energy Dispersive X-ray Spectroscopy). can be analyzed for Pb content.

In addition, in the electromechanical transducer 20 of this embodiment, the value of the leakage current density measured between terminals electrically connected from a pair of electrodes (the first electrode 15 and the second electrode 17) is defined as La. It is preferable that the relationship Lb/La≧0.30 be satisfied, where Lb is the bulk leak current density flowing through the electromechanical conversion film 16.
That is, it is preferable that the electromechanical transducer 20 of this embodiment has a sufficiently small non-bulk leakage current, and that the structure and layout of the electromechanical transducer 20 itself are configured so that no leakage current flows.

The bulk leak current flowing through the electromechanical transducer membrane 16 can be generated by, for example, changing the peripheral length of the third electrode 27 and the fourth electrode 28 while keeping the electrode areas substantially the same in the configuration shown in FIG. The leakage current flowing through the bulk is quantified, and based on the sheet resistance values of the second electrode 17, third electrode 27, fourth electrode 28, and second insulating protective film 22, the electromechanical transducer 20 and its It can be measured by distinguishing current from other currents.

It is preferable that the dielectric strength voltage of the electromechanical transducer 20 of this embodiment is 100V or more.
This makes it possible to maintain electromechanical conversion characteristics and continue driving without failure, thereby achieving high reliability.
The dielectric strength can be evaluated by TZDB (Time Zero Dielectric Breakdown) evaluation based on the leakage current measurement results when voltage is applied in 1V steps from 0 to 200V, for example.
The failure rate is the failure rate when driven for a specified time (for example, 1 x 10 ⁶ seconds) at a specified voltage (for example, DC voltage 50 V) as a TDDB (Time Dependence Dielectric Breakdown) evaluation. It can be evaluated by calculating.

The electromechanical transducer film 16 is a crystal film preferentially oriented in the (100) plane, and the crystal grains of the electromechanical transducer film 16 are preferably columnar crystal grains grown in the film thickness direction.
FIG. 5 shows a cross-sectional TEM image of an example of the electromechanical transducer film of this embodiment.
In FIG. 5, the lower right portion is an electrode, and columnar crystal grains grown in the film thickness direction D can be observed in the electromechanical conversion film 16.

[Liquid ejection head]
An embodiment will be described in which the electromechanical transducer 20 of this embodiment is applied to a liquid ejection head used in an inkjet recording apparatus, which is a device that ejects liquid.
As shown in FIGS. 6(A) and 6(B), a liquid ejecting head used in an inkjet recording apparatus includes a nozzle plate 12 on which nozzles 11 for ejecting liquid (ink) for image formation are formed, and nozzles 11. The pressurizing chamber 18 communicates with the pressurizing chamber 18, and an electromechanical transducer 20 as a pressure generating means for generating pressure for ejecting ink within the pressurizing chamber 18.
The electromechanical transducer 20 deforms itself when a predetermined voltage is applied, and generates pressure in the liquid in the pressurizing chamber 18 by displacing the surface of the diaphragm 14 with respect to the pressurizing chamber 18. . This pressure allows liquid (ink droplets) to be ejected from the nozzle 11 communicating with the pressurizing chamber 18 .

For example, the liquid ejection head etches the first electrode 15, electromechanical conversion film 16, and second electrode 17 into a desired shape for the electromechanical transducer shown in FIG. 1, and then provides an insulating protective film. , by etching from the substrate 13 side to form the pressurized chamber 18 for ejecting ink.

In FIG. 6(A), the first electrode 15 (lower electrode) is a common electrode and the second electrode 17 (upper electrode) is an individual electrode, whereas in FIG. 6(B), The first electrode 15 (lower electrode) is an individual electrode, and the second electrode 17 (upper electrode) is a common electrode.
Note that the liquid supply means, flow path, fluid resistance, etc. are omitted in the figure.

Further, a plurality of liquid ejection heads may be arranged as in the example shown in FIG. 7 .
FIG. 7(A) shows an example in which a plurality of heads shown in FIG. 6(A) are arranged, and like FIGS. 1 and 2, the first electrode 15 (lower electrode) is a common electrode. , the second electrode 17 (upper electrode) is an individual electrode. On the other hand, FIG. 7B shows an example in which a plurality of heads shown in FIG. 6B are arranged, in which the first electrode 15 (lower electrode) is an individual electrode, and the second electrode 17 (upper electrode) serves as a common electrode.

[Liquid discharge unit and device for discharging liquid]
The liquid ejection unit of this embodiment includes the liquid ejection head of this embodiment.
The liquid ejection unit of the present embodiment also includes a head tank that stores liquid to be supplied to the liquid ejection head, a carriage that mounts the liquid ejection head, a supply mechanism that supplies liquid to the liquid ejection head, and the liquid ejection head. The liquid ejection head is integrated with at least one of a maintenance and recovery mechanism that maintains and recovers the liquid ejection head, and a main scanning movement mechanism that moves the liquid ejection head in the main scanning direction.

The apparatus for ejecting liquid according to this embodiment includes the liquid ejection head according to this embodiment or the liquid ejection unit according to this embodiment.

Next, an example of a device for discharging liquid according to the present invention will be described with reference to FIGS. 8 and 9. FIG. 8 is an explanatory plan view of the main part of the apparatus, and FIG. 9 is a side view of the main part of the apparatus.

This device is a serial type device, and a carriage 403 is reciprocated in the main scanning direction by a main scanning movement mechanism 493. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, and the like. The guide member 401 spans between the left and right side plates 491A and 491B, and movably holds the carriage 403. Then, the carriage 403 is reciprocated in the main scanning direction by the main scanning motor 405 via a timing belt 408 stretched between a driving pulley 406 and a driven pulley 407 .

This carriage 403 is equipped with a liquid ejection unit 440 that integrates a liquid ejection head 404 and a head tank 441 according to the present invention. The liquid ejection head 404 of the liquid ejection unit 440 ejects liquid of each color, for example, yellow (Y), cyan (C), magenta (M), and black (K). Further, the liquid ejection head 404 has a nozzle array made up of a plurality of nozzles 11 arranged in a sub-scanning direction perpendicular to the main scanning direction, and is mounted with the ejection direction facing downward.

A supply mechanism 494 for supplying liquid stored outside the liquid ejection head 404 to the liquid ejection head 404 supplies the liquid stored in the liquid cartridge 450 to the head tank 441 .

The supply mechanism 494 includes a cartridge holder 451, which is a filling section into which the liquid cartridge 450 is mounted, a tube 456, a liquid feeding unit 452 including a liquid feeding pump, and the like. Liquid cartridge 450 is removably attached to cartridge holder 451. Liquid is fed from the liquid cartridge 450 to the head tank 441 by a liquid feeding unit 452 via a tube 456 .

This device includes a transport mechanism 495 for transporting paper 410. The conveyance mechanism 495 includes a conveyance belt 412 that is a conveyance means, and a sub-scanning motor 416 for driving the conveyance belt 412.

The conveyance belt 412 attracts the paper 410 and conveys it to a position facing the liquid ejection head 404 . This conveyance belt 412 is an endless belt, and is stretched between a conveyance roller 413 and a tension roller 414. Adsorption can be performed by electrostatic adsorption, air suction, or the like.

The conveyance belt 412 rotates in the sub-scanning direction by rotationally driving the conveyance roller 413 via the timing belt 417 and timing pulley 418 by the sub-scanning motor 416.

Further, a maintenance and recovery mechanism 420 that maintains and recovers the liquid ejection head 404 is arranged on one side of the carriage 403 in the main scanning direction and on the side of the conveyor belt 412.

The maintenance and recovery mechanism 420 includes, for example, a cap member 421 that caps the nozzle surface (the surface on which the nozzles 11 are formed) of the liquid ejection head 404, a wiper member 422 that wipes the nozzle surface, and the like.

The main scanning movement mechanism 493, the supply mechanism 494, the maintenance and recovery mechanism 420, and the transport mechanism 495 are attached to a housing including side plates 491A, 491B and a back plate 491C.

In this apparatus configured in this manner, the paper 410 is fed onto the conveyor belt 412 and adsorbed, and the paper 410 is conveyed in the sub-scanning direction by the rotational movement of the conveyor belt 412.

Therefore, by driving the liquid ejection head 404 according to the image signal while moving the carriage 403 in the main scanning direction, liquid is ejected onto the stationary paper 410 to form an image.

In this manner, since this apparatus includes the liquid ejection head according to the present invention, it is possible to stably form high-quality images.

Next, another example of the liquid ejection unit according to the present invention will be described with reference to FIG. 10. FIG. 10 is an explanatory plan view of the main parts of the unit.

This liquid ejection unit includes, among the members constituting the liquid ejecting device, a housing portion composed of side plates 491A, 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and a liquid ejection unit. It is composed of a discharge head 404.

Note that it is also possible to configure a liquid ejection unit in which at least one of the above-mentioned maintenance and recovery mechanism 420 and supply mechanism 494 is further attached to, for example, the side plate 491B of this liquid ejection unit.

Next, still another example of the liquid ejection unit according to the present invention will be described with reference to FIG. 11. FIG. 11 is an explanatory front view of the unit.

This liquid ejection unit includes a liquid ejection head 404 to which a channel component 444 is attached, and a tube 456 connected to the channel component 444.

Note that the channel component 444 is arranged inside the cover 442. A head tank 441 can also be included instead of the flow path component 444. Further, a connector 443 for electrically connecting with the liquid ejection head 404 is provided on the upper part of the flow path component 444.

In the present application, a "device for ejecting liquid" is a device that includes a liquid ejection head or a liquid ejection unit and drives the liquid ejection head to eject liquid. Devices that eject liquid include not only devices that are capable of ejecting liquid onto objects to which liquid can adhere, but also devices that eject liquid into air or into liquid.

The "device for discharging liquid" may include means for feeding, transporting, and discharging objects to which liquid can adhere, as well as pre-processing devices, post-processing devices, and the like.

For example, an image forming device is a device that ejects ink to form an image on paper as a “device that ejects liquid,” and an image forming device that forms layers of powder to form three-dimensional objects (three-dimensional objects). There is a three-dimensional modeling device (three-dimensional modeling device) that discharges a modeling liquid onto a powder layer.

Further, the "device for ejecting liquid" is not limited to a device that can visualize significant images such as characters and figures using ejected liquid. For example, it includes those that form patterns that have no meaning in themselves, and those that form three-dimensional images.

The above-mentioned "something to which a liquid can adhere" refers to something to which a liquid can adhere at least temporarily, such as something that adheres and sticks, something that adheres and penetrates. Specific examples include recording media such as paper, recording paper, recording paper, film, and cloth, electronic components such as electronic boards, piezoelectric elements, powder layers, organ models, and test cells. Unless otherwise specified, it includes everything to which liquid adheres.

The above-mentioned "materials to which liquids can adhere" include paper, thread, fibers, fabrics, leather, metals, plastics, glass, wood, ceramics, building materials such as wallpaper and flooring, and textiles for clothing. However, it is fine as long as it can be attached.

Furthermore, "liquid" includes ink, processing liquid, DNA sample, resist, pattern material, binder, modeling liquid, and solutions and dispersions containing amino acids, proteins, and calcium.

Further, the "device for discharging liquid" includes a device in which a liquid discharging head and an object to which liquid can be attached move relative to each other, but the present invention is not limited to this. Specific examples include a serial type device that moves a liquid ejection head, a line type device that does not move a liquid ejection head, and the like.

In addition, "devices that discharge liquid" include processing liquid coating devices that discharge processing liquid onto paper in order to apply processing liquid to the surface of paper for purposes such as modifying the surface of the paper, and raw materials. There is an injection granulation device that granulates fine particles of a raw material by injecting a composition liquid dispersed in a solution through a nozzle.

A "liquid ejection unit" is a liquid ejection head with functional parts and mechanisms integrated, and is an assembly of parts related to liquid ejection. For example, the "liquid ejection unit" includes a combination of a liquid ejection head and at least one of the following structures: a head tank, a carriage, a supply mechanism, a maintenance recovery mechanism, and a main scanning movement mechanism.

Here, integration refers to, for example, a liquid ejection head, a functional component, or a mechanism fixed to each other by fastening, adhesion, engagement, etc., or one in which one is held movably relative to the other. include. Further, the liquid ejection head, the functional parts, and the mechanism may be configured to be detachable from each other.

For example, as a liquid ejection unit, there is a liquid ejection unit such as a liquid ejection unit 440 shown in FIG. 9 in which a liquid ejection head and a head tank are integrated. In addition, there are devices in which a liquid ejection head and a head tank are integrated by being connected to each other with a tube or the like. Here, a unit including a filter may be added between the head tank and the liquid ejection head of these liquid ejection units.

Further, some liquid ejection units have a liquid ejection head and a carriage integrated.

Further, some liquid ejection units have the liquid ejection head movably held by a guide member that constitutes a part of the scanning movement mechanism, so that the liquid ejection head and the scanning movement mechanism are integrated. Further, as shown in FIG. 10, there is a liquid ejection unit in which a liquid ejection head, a carriage, and a main scanning movement mechanism are integrated.

Furthermore, some liquid ejection units have a cap member, which is part of the maintenance recovery mechanism, fixed to the carriage to which the liquid ejection head is attached, so that the liquid ejection head, the carriage, and the maintenance recovery mechanism are integrated. .

Furthermore, as shown in FIG. 11, some liquid ejection units have a tube connected to a liquid ejection head to which a head tank or flow path components are attached, so that the liquid ejection head and supply mechanism are integrated. .

The main scanning movement mechanism also includes a single guide member. Further, the supply mechanism includes a single tube and a single loading section.

Furthermore, the pressure generating means used in the "liquid ejection head" is not limited. For example, in addition to the piezoelectric actuator (which may use a laminated piezoelectric element) as explained in the above embodiment, there is also a thermal actuator that uses an electrothermal transducer such as a heating resistor, and a thermal actuator that uses a diaphragm and a counter electrode. An electrostatic actuator or the like may also be used.

Further, in the terms of this application, image formation, recording, printing, imprinting, printing, modeling, etc. are all synonymous.

The liquid ejecting device of this embodiment is a liquid ejecting device that includes a liquid ejecting head that ejects liquid from a nozzle based on a drive signal. A liquid ejection head equipped with 20 is used.

An image forming apparatus as an example of a liquid ejecting apparatus according to the present embodiment is shown in FIGS. 12 and 13.
FIG. 12 is a perspective view of the image forming apparatus, and FIG. 13 is a side view of a mechanical section of the image forming apparatus.

The liquid ejecting apparatus (image forming apparatus) of this embodiment includes a carriage movable in the main scanning direction inside the apparatus main body 81, a liquid ejection head mounted on the carriage, and an ink supplying ink to the liquid ejection head. A printing mechanism section 82 and the like made up of a cartridge and the like is housed.

A paper feed cassette (or paper feed tray) 84 that can load a large number of sheets of paper 83 from the front side can be removably attached to the lower part of the main body 81 of the apparatus, and the paper 83 can also be manually fed. The manual feed tray 85 can be opened and folded. Then, the paper 83 fed from the paper cassette 84 or the manual feed tray 85 is taken in, the desired image is recorded by the printing mechanism section 82, and then the paper 83 is ejected to the paper ejection tray 86 attached to the rear side. It is papered.
A carriage 93 is held in the printing mechanism section 82 so as to be slidable in the main scanning direction by a main guide rod 91 and a sub guide rod 92, which are guide members extending horizontally between left and right side plates.

The carriage 93 has a head 94, which is a liquid ejection head according to the present invention that ejects ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk), and has a plurality of ink ejection ports ( The liquid ejection head is mounted with the nozzles (nozzles) arranged in a direction intersecting the main scanning direction, and the ink droplet ejection direction facing downward. Further, each ink cartridge 95 for supplying ink of each color to the head 94 is attached to the carriage 93 in a replaceable manner.

The ink cartridge 95 is provided with an air port communicating with the atmosphere above, a supply port below that supplies ink to the liquid ejection head, and a porous body filled with ink inside. The capillary force of this porous body maintains the ink supplied to the liquid ejection head at a slight negative pressure. Further, although heads 94 of each color are used as the liquid ejection head here, it may be one head having nozzles that eject ink droplets of each color.

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

The image forming apparatus also includes a paper feed roller 101 and a friction pad 102 that separate and feed the paper 83 from the paper feed cassette 84 in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the head 94. It is provided. Furthermore, a guide member 103 that guides the paper 83, a transport roller 104 that reverses and transports the fed paper 83, a transport roller 105 that is pressed against the circumferential surface of the transport roller 104, and the paper 83 from the transport roller 104. A tip roller 106 is provided to define the feeding angle of the roller. The conveyance roller 104 is rotationally driven by a sub-scanning motor 107 via a gear train.

An impression receiving member 109 is a paper guide member that guides the paper 83 sent out from the transport roller 104 on the lower side of the liquid ejection head (recording head) 94 in accordance with the movement range of the carriage 93 in the main scanning direction. It is provided. On the downstream side of the print receiving member 109 in the paper transport direction, there are provided a transport roller 111 and a spur 112 that are rotationally driven to send the paper 83 in the paper ejection direction. Further, the image forming apparatus is provided with a paper ejection roller 113 and a spur 114 that send out the paper 83 to the paper ejection tray 86, and guide members 115 and 116 that form a paper ejection path.

During recording, while the carriage 93 is moving, a liquid ejection head (recording head) 94 is driven in accordance with an image signal to eject ink onto the stationary paper 83 to record one line. After being conveyed by a predetermined amount, the next line is recorded. By receiving a recording end signal or a signal indicating that the trailing edge of the paper 83 has reached the recording area, the recording operation is completed and the paper 83 is ejected.

Further, a recovery device 117 for recovering ejection failure of the head 94 is arranged at a position outside the recording area on the right end side in the moving direction of the carriage 93, and the recovery device 117 includes a cap means, a suction means, and a cleaning means. have.
During printing standby, the carriage 93 is moved to the recovery device 117 side and the head 94 is capped by a capping means, and by keeping the ejection opening in a moist state, it is possible to prevent ejection failure due to ink drying. Furthermore, by ejecting ink unrelated to printing during recording, the ink viscosity of all the ejection ports can be made constant and stable ejection performance can be maintained.

If an ejection failure occurs, the ejection port (nozzle) of the head 94 is sealed with a capping means, and air bubbles, etc., are sucked out together with the ink from the ejection port by a suction means through a tube, and ink, dust, etc. attached to the ejection port surface are removed. can be removed by cleaning means, and ejection failures can be recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the bottom of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.

In the liquid ejecting device (image forming apparatus) of this embodiment, the mounted liquid ejecting head maintains electromechanical conversion characteristics even in a high humidity environment and can continue to drive without failure. Since it includes a highly reliable electromechanical transducer, stable ink droplet ejection characteristics can be obtained and high image quality can be maintained.

In addition to the above-mentioned liquid ejection head and liquid ejection device (image forming apparatus), examples of the piezoelectric device including the electromechanical transducer according to the present invention include a motor, an ultrasonic vibrator, a piezoelectric sensor, a ferroelectric memory, Examples include power generators and speakers.

[Example]
More specific examples of the electromechanical transducer (piezoelectric actuator) according to this embodiment and a liquid ejection head including the same will be described together with comparative examples.

(Example 1)
<Production of electromechanical transducer (piezoelectric actuator)>
A 6-inch silicon wafer is prepared as the substrate 13, and the substrate 13 is coated with SiO ₂ (film thickness 600 nm), Si (film thickness 200 nm), SiO ₂ (film thickness 100 nm), SiN (film thickness 150 nm), SiO ₂ (film thickness 130 nm). ), SiN (150 nm), SiO ₂ (thickness 100 nm), Si (200 nm), and SiO ₂ (thickness 600 nm) were sequentially formed to produce the diaphragm 14.

Thereafter, a lower electrode (first electrode 15 in this embodiment) was formed on the portion that would become the diaphragm 14.
The lower electrode has a structure in which an adhesive layer and a metal electrode film are laminated. The adhesion layer was formed by forming a titanium film (film thickness 20 nm) using a sputtering device at a film formation temperature of 350°C, and then thermally oxidizing it at 750°C using rapid thermal annealing (RTA). . Subsequently, a platinum film (thickness: 160 nm) was formed as a metal electrode film using a sputtering device at a film formation temperature of 400°C.

Next, a solution (hereinafter referred to as "PT solution") adjusted to Pb:Ti=1:1 was formed as a PbTiO ₃ layer (hereinafter referred to as "PT layer") as a base layer by spin coating, and the film was heated at 120°C. was dried to form a layer with a thickness of 7 nm.

Next, prepare PZT precursor solutions 1 to 3 adjusted to the following three ratios as an electromechanical conversion film, and spin coat in the order of PZT precursor solution 1, PZT precursor solution 2, and PZT precursor solution 3. The film was formed by the method.
[PZT precursor solution 1] Pb:Zr:Ti=115:58:42
[PZT precursor solution 2] Pb:Zr:Ti=115:53:47
[PZT precursor solution 3] Pb:Zr:Ti=110:48:52

Regarding the synthesis of a specific precursor coating liquid, lead acetate trihydrate, titanium isopropoxide, and zirconium isopropoxide were used as starting materials. Crystal water of lead acetate was dissolved in methoxyethanol and then dehydrated. The amount of lead is excessive compared to the stoichiometric composition. This is to prevent a decrease in crystallinity due to so-called lead removal during heat treatment. A PZT precursor solution was synthesized by dissolving titanium isopropoxide and zirconium isopropoxide in methoxyethanol, proceeding with alcohol exchange reaction and esterification reaction, and mixing with the methoxyethanol solution in which lead acetate was dissolved.
At this time, the PZT concentration in the PZT precursor solution was set to 0.5 mol/L. The PT solution was also prepared in the same manner as the PZT precursor solution.

Next, a PT layer was first formed by spin coating using a PT solution, and after the film was formed, it was dried at 120°C. Thereafter, a PZT precursor solution was formed into a film by spin coating, and after the film formation, it was dried at 120°C and thermally decomposed at 400°C. Then, the steps of film formation, drying, and thermal decomposition were repeated to form a laminated film.

After the thermal decomposition treatment of the third layer, a crystallization heat treatment (temperature 700° C., 10 minutes) was performed by RTA (rapid thermal treatment). At this time, the film thickness of PZT was 240 nm.
This step was repeated 8 times in total, and a total of 24 layers were laminated to obtain an electromechanical transducer film that was a PZT film with a film thickness of approximately 2 μm.

Next, an upper electrode (second electrode 17 in this embodiment) was formed. First, a SrRuO ₃ film (40 nm thick) was formed as an oxide electrode film, and then a platinum (Pt) film (125 nm thick) was sputtered as a metal electrode film. Thereafter, a film of photoresist (TSMR8800) manufactured by Tokyo Ohka Co., Ltd. was formed by spin coating, and a resist pattern was formed by ordinary photolithography, and then a pattern as shown in Figure 2 was formed using an ICP etching device (manufactured by Samco). Created.

At this time, a pattern was formed to ensure a distance of 4 μm between the edge of the upper electrode (platinum) and the edge of the electromechanical conversion film 16. The edge of the upper electrode refers to the edge of the patterned upper electrode, and the end of the electromechanical conversion film 16 refers to the edge of the outermost surface of the patterned electromechanical conversion film 16. By ensuring the distance between the edges, the main Surface leakage can be suppressed.

Next, as the first insulating protective film 21, an Al ₂ O ₃ film was formed to a thickness of 80 nm using an ALD (atomic layer deposition) method. At this time, as raw materials for Al, TMA (trimethylaluminum, manufactured by Sigma-Aldrich) was alternately supplied, and for O, O ₃ generated by an ozone generator was alternately supplied and laminated to proceed with film formation.

Thereafter, as shown in FIG. 2, contact holes 25 were formed by etching.
Then, as common/individual electrode lead wiring (third electrode 27, fourth electrode 28), an Al--Cu film was formed by sputtering and patterned by etching.

Next, a Si ₃ N ₄ film was formed as a second insulating protective film 22 to a thickness of 500 nm by plasma CVD.
Openings were provided in the second insulating protective film, and common electrode pads 23 and individual electrode pads 24 for connection to common/individual electrode lead wiring (third electrode 27, fourth electrode 28) were formed. The distance between individual electrode pads 24 was 80 μm.

The electromechanical transducers 20 were laid out so that 300 electromechanical transducers were lined up in one row within one chip.

Furthermore, in the liquid ejection head of this embodiment, a bonding step for bonding the holding substrate to the electromechanical transducer 20 shown in FIG. 2 was formed.
The bonding surface level difference is provided at a position corresponding to the partition wall of the pressurizing chamber 18, and includes the first insulating protective film 21, the common/individual electrode lead wiring (third electrode 27, fourth electrode 28), and the second Although it is composed of laminated layers that are the same as each layer of the insulating protective film, it is not provided on the active part of the electromechanical transducer element or on the outside of the partition wall of the pressurizing chamber 18, so that the diaphragm 14 may be deformed. It has no effect on the area.

Thereafter, polarization treatment was performed by corona charging using the polarization treatment apparatus shown in FIG.
A tungsten wire with a diameter of 50 μm was used as the corona electrode used in the corona charging process, and a stainless steel grid electrode with an aperture ratio of 60% was used as the grid electrode.
The polarization treatment conditions were a treatment temperature of 80°C, a corona electrode voltage of 9 kV, a grid electrode voltage of 1.5 kV, a treatment time of 30 seconds, a distance of 4 mm between the corona electrode and the grid electrode, and a distance of 4 mm between the grid electrode and the stage. Ta.

<Fabrication of liquid ejection head>
Thereafter, the back surface of the substrate 13 is etched to form a pressurizing chamber 18 (length (width) in the short direction is 60 μm) as shown in FIG. A discharge head was manufactured.
Etching of the substrate 13 was performed after the holding substrate was bonded to hold the pressurizing chamber 18. Note that the width of the opening of the holding substrate was 75 μm.

<Composition analysis>
(1) Average Pb Content As a composition analysis of the electromechanical conversion film (PZT film), the contents of Pb, Zr, and Ti were measured by ICP emission spectrometry. As for the composition ratio, the sum of the Zr and Ti contents contained in the film was taken as 100%, and the Pb content ratio with respect to this was calculated as the average Pb content.
(2) Content ratio of grain boundary Pb and grain Pb In addition, the Pb content inside the grain and the Pb content in the region including the grain boundary were analyzed by TEM-EDS at four arbitrary points. The ratio of Pb content at grain boundaries to Pb content (average value of four measured points) was calculated.
The results are shown in Table 1.

<Pb content distribution in film thickness direction>
The Pb content contained in the electromechanical transducer film (PZT film) described above was measured approximately every 10 μm in the film thickness direction up to 1000 μm.
The measurement results are shown in the graph of FIG.
The vertical axis of the graph in FIG. 14 indicates the content ratio (unit: %) of Pb/(Zr+Ti), and the horizontal axis indicates the position from the film surface in the film thickness direction (unit: μm).
In addition, as an evaluation of the Pb content distribution, a film in which the Pb content measured in the film thickness direction is within ±4% of the average value (difference in measured value is within 8%) is considered to be "approximately uniform". (○)” is shown in Table 1.

<Evaluation of electromechanical conversion characteristics>
(1) Evaluation of dielectric strength voltage and failure rate For dielectric strength voltage and TZDB evaluation, leakage current was measured when voltage was applied from 0 to 200 V in 1 V steps.
As for the failure rate, the failure rate when driven for 1×10 ⁶ seconds at a DC voltage of 50 V was calculated as a TDDB evaluation.
The results are shown in Table 1.
In addition, the evaluation of the failure rate is as follows: less than 0.5% is "excellent (◎)", 0.5 or more and less than 1.0% is "good (○)", and 1.0% or more is "poor (x)". ”, and those rated “Good (○)” or higher are considered suitable for practical use.

(2) Measurement of leak current density and bulk leak current density Measurement was performed in a high humidity environment with a water vapor pressure of 300 kPa using a constant temperature bath (manufactured by ESPEC).
The water vapor pressure was derived by multiplying the relative humidity by the saturated water vapor pressure derived from the Wagner equation below.

However, Pc=22120kPa: critical pressure, Tc=647.3K: critical temperature, T=absolute temperature (K)
A=-7.76451, B=1.45838, C=-2.7758, D=-1.23303

Under the above environment, the leakage current density at a DC voltage of 40 V was measured.
Regarding the leakage current density, in order to distinguish between the electromechanical transducer 20 and the others, the third electrode 27 and the fourth electrode 28 can be reduced in bulk by changing the peripheral length of the electrodes while keeping the electrode areas approximately the same. The electric machine It was measured by distinguishing the current outside the conversion element.
Furthermore, the value of the leakage current density measured between the terminals was taken as La, the bulk leakage current density flowing in the electromechanical transducer film was taken as Lb, and the value of Lb/La was calculated.
The results are shown in Table 1.

(3) Piezoelectric constant d31
Regarding the piezoelectric constant d31, the amount of displacement at an electric field strength of 150 kV/cm was measured using a laser Doppler vibrometer, and the amount of displacement was calculated by simulation based on the obtained amount of displacement.
The results are shown in Table 1.

(Example 2)
The PZT precursor solution was deposited by spin coating to form a laminated film, and the crystallization heat treatment conditions performed after the third layer thermal decomposition treatment were performed in the same manner as in Example 1, except that the temperature was 730 ° C. for 10 minutes. An electromechanical transducer element and a liquid ejection head were manufactured.
Further, in the same manner as in Example 1, compositional analysis, measurement of Pb content distribution in the film thickness direction, and evaluation of electromechanical conversion characteristics were performed.
The results are shown in Table 1. Further, the measurement results of the Pb content distribution in the film thickness direction are shown in FIG.

(Example 3)
An electromechanical transducer and a liquid ejection head were manufactured in the same manner as in Example 1 except that the first insulating protective film was an AlN film.
Further, in the same manner as in Example 1, compositional analysis, measurement of Pb content distribution in the film thickness direction, and evaluation of electromechanical conversion characteristics were performed.
The results are shown in Table 1. Further, the measurement results of the Pb content distribution in the film thickness direction are shown in FIG.

(Example 4)
Same as Example 1 except that the pattern was formed to ensure a distance of 1 μm between the edge of the common/individual electrode lead wiring (third electrode 27, fourth electrode 28) and the edge of the electromechanical conversion film 16. An electromechanical transducer and a liquid ejection head were manufactured using the following methods.
Further, in the same manner as in Example 1, compositional analysis, evaluation of Pb content distribution in the film thickness direction, and evaluation of electromechanical conversion characteristics were performed.
The results are shown in Table 1.

(Comparative example 1)
A film was formed by spin coating using PZT precursor solution 2 (Pb:Zr:Ti=115:53:47) as the PZT precursor solution, and after drying and thermal decomposition steps, crystallization heat treatment was performed at a temperature of 700°C. An electromechanical transducer and a liquid ejection head were produced in the same manner as in Example 1, except that the test was carried out for 3 minutes.
In addition, compositional analysis and electromechanical conversion characteristics were evaluated in the same manner as in Example 1.
The results are shown in Table 1.

(Comparative example 2)
A film was formed by spin coating using PZT precursor solution 2 (Pb:Zr:Ti=115:53:47) as the PZT precursor solution, and after drying and thermal decomposition steps, crystallization heat treatment was performed at a temperature of 730°C. An electromechanical transducer and a liquid ejection head were produced in the same manner as in Example 1, except that the test was carried out for 3 minutes.
In addition, compositional analysis and electromechanical conversion characteristics were evaluated in the same manner as in Example 1.
The results are shown in Table 1.

なお、表中※１（Ｐｂ含有率分布）の「○」は略均一であることを示し、「－」は評価を行っていないか、均一ではないことを示す。
また、表中※２（故障発生率）の「◎」は優良、「○」は良、「×」は不良を示し、「○」以上が実用に適していることを意味する。

In addition, "○" in *1 (Pb content distribution) in the table indicates that it is approximately uniform, and "-" indicates that no evaluation has been performed or it is not uniform.
In addition, in the table *2 (failure incidence), "◎" indicates excellent, "○" indicates good, and "x" indicates poor, and "○" or higher means suitable for practical use.

As shown in Table 1, the electromechanical transducers of Examples 1 to 4 have leakage current densities measured between terminals electrically connected from the pair of electrodes in an environment where the water vapor pressure is 300 kPa. It is 4.2×10 ⁻⁶ A/cm ² or less, and the Pb content contained in the electromechanical conversion film (PZT film) is approximately uniform in the film thickness direction.

Further, it can be seen that the value of the bulk leak current density (Lb) and the value of the leak current density (La) satisfy the relationship of Lb/La≧0.30, and the leak current is extremely small. This is achieved by satisfying the conditions that the average Pb content is 100 to 110% and the ratio of the Pb content at the grain boundaries to the Pb content inside the grains is 105% or less, thereby reducing bulk leak. This is probably due to what happened. It is considered that these values can be achieved by setting conditions in which lead titanate and lead zirconate of PZT are sufficiently dissolved in solid solution during the firing process.

Further, the dielectric strength values of the electromechanical transducers of Examples 1 to 4 are sufficiently high, the failure rate is less than 1.0%, and the piezoelectric constant d31 is also good.

As described above, the electromechanical conversion elements of Examples 1 to 4 maintain electromechanical conversion characteristics even in a high humidity environment, can continue driving without failure, and are highly reliable. was confirmed.

On the other hand, in Comparative Examples 1 and 2, the value of leakage current density was very large, and the failure rate was also 1.0% or more. It should be noted that a failure occurred approximately 5 hours after the start of operation.

11 nozzle 12 nozzle plate 13 substrate 14 diaphragm 15 first electrode 16 electromechanical conversion film 17 second electrode 18 pressure chamber 20 electromechanical conversion element 21 first insulating protective film 22 second insulating protective film 23 common electrode Pad 24 Individual electrode pad 27 Third electrode (common lead wiring)
28 Fourth electrode (individual extraction wiring)
40 Polarization processing device

Patent No. 3552013 Patent No. 4463766

Claims (12)

An electromechanical transducer film made of a complex oxide having a perovskite structure containing at least Pb, Zr, and Ti, and having a film thickness of 1.0 μm to 3.0 μm ;
a pair of electrodes disposed with the electromechanical conversion membrane in between;
an insulating protective film covering the electromechanical conversion film and the pair of electrodes,
The Pb content in the electromechanical conversion film is substantially uniform in the film thickness direction,
In an environment where the water vapor pressure is 300 kPa, the leakage current density at a DC voltage of 40 V measured between the terminals electrically connected from the pair of electrodes is 4.2 × 10 ^-6 A/cm ² or less. Characteristic electromechanical transducer. When the value of the leakage current density measured between the terminals electrically connected from the pair of electrodes is La, and the bulk leakage current density flowing in the electromechanical conversion film is Lb, 0.32≦Lb/La The electromechanical transducer according to claim 1, wherein the electromechanical transducer satisfies the relationship: ≦0.38 . 3. The electromechanical transducer according to claim 1, wherein the electromechanical transducer has a dielectric strength of 100V or more. 4. The electromechanical transducer according to claim 1, wherein the average Pb content in the electromechanical conversion film is 106.1 to 108.2% with respect to the sum of Zr and Ti contents. Electromechanical conversion element. The electromechanical conversion film has a plurality of particles and grain boundaries existing between the plurality of particles,
5. The Pb content according to claim 1, wherein the Pb content in the region including the grain boundaries is 102.2 to 103.6% with respect to the Pb content inside the plurality of grains. Electromechanical conversion element. 6. The electromechanical transducer according to claim 1, wherein the insulating protective film is made of any one of aluminum oxide, silicon oxide, aluminum nitride, and silicon nitride. The electromechanical conversion film is a crystal film preferentially oriented in the (100) plane,
7. The electromechanical transducer element according to claim 1, wherein the crystal grains of the electromechanical transducer film are columnar crystal grains grown in the film thickness direction. A liquid ejection head comprising the electromechanical transducer according to claim 1. A liquid ejection unit comprising the liquid ejection head according to claim 8. A head tank that stores liquid to be supplied to the liquid ejection head, a carriage that mounts the liquid ejection head, a supply mechanism that supplies liquid to the liquid ejection head, a maintenance and recovery mechanism that maintains and recovers the liquid ejection head, and the liquid. 10. The liquid ejection unit according to claim 9, wherein the liquid ejection head is integrated with at least one of a main scanning movement mechanism that moves the ejection head in the main scanning direction. An apparatus for ejecting liquid, comprising the liquid ejection head according to claim 8 or the liquid ejection unit according to claim 9 or 10. A piezoelectric device comprising the electromechanical transducer according to claim 1.

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