JP2020053620A - Solution for forming ferroelectric thin film, ferroelectric thin film, piezoelectric element, liquid discharge head, liquid discharge unit, liquid discharge device, and piezoelectric device - Google Patents

Abstract

To provide a solution for forming a ferroelectric thin film, which can obtain a ferroelectric thin film having good piezoelectric characteristics without variation.SOLUTION: A solution for forming a ferroelectric thin film includes lead, zirconium, and titanium, and in a case in which degreasing treatment and crystallization treatment are performed sequentially, when the mass of a processed material 1 after the degreasing treatment is mass A, and the mass of the processed material 2 after the crystallization treatment is mass B, the reduction rate defined by the following equation (1) is 5.0% or more and 6.5% or less. The reduction rate={(mass A-mass B)/mass A}×100(%) (1)SELECTED DRAWING: Figure 15

Description

  The present invention relates to a solution for forming a ferroelectric thin film, a ferroelectric thin film, a piezoelectric element, a liquid ejection head, a liquid ejection unit, a liquid ejection device, and a piezoelectric device.

  A part of a pressure generating chamber communicating with a nozzle opening for discharging ink is constituted by a diaphragm, and the diaphragm is deformed by a piezoelectric element to pressurize ink in the pressure generating chamber to discharge ink from the nozzle opening. In the recording head, a bulk-shaped piezoelectric element is expanded and contracted in the direction of the applied electric field, and the diaphragm is deformed by pressing the diaphragm back and forth. Two types of piezoelectric actuators of a type that expands and contracts and deforms a diaphragm by bending it are already known.

  As a piezoelectric material used as the above-described piezoelectric actuator, a lead zirconate titanate (PZT) material which is a perovskite-type ferroelectric substance is well known. This PZT material has extremely good piezoelectricity and ferroelectricity as compared with other materials, and has a feature that the usable temperature range is wide, so not only the piezoelectric actuator but also the ferroelectricity was utilized. It is applied to a wide range of fields such as electronic devices.

  Using the PZT material described above, particularly when manufacturing a piezoelectric actuator in the form of a thin film, various methods such as a sol-gel method, a sputtering method, and a CVD method are formed on a silicon wafer on which a lower electrode is formed. After a PZT film having a thickness of 1 to 3 μm is formed, a piezoelectric actuator is manufactured by applying a Si-MEMS process, for which a number of known techniques are known, to the PZT film. Then, by being combined with other components, it is used for various applications such as an ink jet head.

  Among the film forming methods, among them, the sol-gel method is to apply a precursor solution obtained by mixing a metal alkoxide solution to be a PZT precursor solution on a silicon wafer by spin coating or dip coating, and then dry, degrease, and crystallize. This is a method of forming a PZT film through a heating process (see, for example, Patent Document 1). In this method, since the metal alkoxide can be dispersed at the atomic level, there are advantages in that non-uniform composition hardly occurs and sintering at a low temperature of 1000 ° C. or less is possible. On the other hand, during the heating process such as drying, degreasing, and crystallization, various phenomena such as solvent removal, residual organic matter removal, crystallization, and lead loss occur, and various factors such as liquid, heating temperature, and atmosphere cause PZT. It is closely related to the crystallinity, orientation, electrical characteristics, etc. of the film. If crystallization is performed in a state where the steps up to degreasing are insufficient, elimination of organic components occurs during the crystallization step, which leads to generation of pores and cracks. It is also affected by the crystallization temperature, and the occurrence of a pyrochlore phase that does not exhibit piezoelectricity at a low crystallization temperature has been confirmed. At higher crystallization temperatures, effects on crystallinity such as a change in the tetragonal ratio (c / a) depending on the temperature have been reported.

In addition, lead loss during the heating process causes a composition deviation of the PZT film after film formation. In general, it is known that PZT exhibits the highest piezoelectric characteristics at a composition ratio represented by PbZr _0.53 Ti _0.47 O ₃ called MPB composition (Morphotropic Phase Boundary). However, lead has a high vapor pressure and volatilizes during the heating process (called lead loss), so that a composition deviation tends to occur in the finally formed film. Therefore, in general, the composition deviation is prevented by including Pb in the composition more than the MPB composition.

In general, as a method for managing a PZT film, a method using X-ray diffraction, elemental analysis, electric characteristics, and the like as indexes is known.
For example, Patent Document 2 discloses an X-ray diffraction intensity profile of a PZT film crystal exhibiting preferable actuator performance. Patent Document 2 is disclosed by the present applicant. At least a first electrode, a piezoelectric body, and a second electrode are sequentially laminated, and a voltage corresponding to a drive signal is applied between the first electrode and the second electrode. In the electromechanical conversion element that deforms the piezoelectric body by applying a pressure to the piezoelectric element, the piezoelectric body is made of a composite oxide having a perovskite structure preferentially oriented in the (100) plane and / or the (001) plane; The (200) plane measured at the position (2θ) where the diffraction intensity is the maximum in the peak of the diffraction intensity corresponding to the (200) plane among the peaks of the diffraction intensity obtained by the measurement by the θ-2θ method of the line diffraction. And / or an electromechanical transducer characterized in that a rocking curve corresponding to the (002) plane has a portion where the diffraction intensity falls. It has been confirmed that such an element can increase the deformation (strain displacement) of the piezoelectric body due to the piezoelectric effect, and can displace the displacement plate to be driven more largely.
Patent Document 3 discloses a lower electrode configuration / structure for forming and manufacturing the above-mentioned crystalline PZT film crystal.

  However, in the method for confirming the characteristics of the PZT film such as the X-ray diffraction and the electrical characteristics evaluation described above, while the performance of the PZT film can be directly evaluated, the film formation and the formation of the electrodes are repeatedly performed until the evaluation is performed. There is a problem that many steps are required. On the other hand, if a defect occurs, it is necessary to investigate various factors such as temperature, atmosphere, and time during the heating process, and even if there is a cause in the precursor solution, excessive It needed trial and error.

  On the other hand, in order to obtain a PZT film having a crystalline property disclosed in Patent Document 2, a sol-gel method is adopted as a film forming technique, conditions of each film forming process are set, and a desired crystal property and film quality are obtained. After confirming that the PZT film was obtained, it was found that if the film formation operation was further repeated under the conditions, the piezoelectric characteristics of the obtained PZT film fluctuated. The present inventors conducted detailed investigations on the problem of the quality variation, and as a result, it was confirmed that there was no difference in the atmosphere, temperature, and composition in the precursor solution during the heating process. On the other hand, when PZT films with good piezoelectric properties and those without them were analyzed by secondary ion mass spectrometry (SIMS) or differential thermogravimetric analysis (Tg-DTA) It was found that there was a difference in the amount of Pb contained in the PZT film. From these results, it was found that the variation in the amount of Pb remaining in the PZT film was the cause of the variation in the piezoelectric characteristics.

  However, a PZT film management method of repeatedly performing the film formation process and the analysis by SIMS is practically impossible from the viewpoints of cost, time, and advanced analysis.

  Therefore, an object of the present invention is to provide a solution for forming a ferroelectric thin film, which can obtain a ferroelectric thin film having good piezoelectric characteristics without variation.

The above problem is solved by the following configuration 1).
1) A solution for forming a ferroelectric thin film for forming a ferroelectric thin film,
The ferroelectric thin film forming solution contains lead, zirconium and titanium,
When heating the solution for forming a ferroelectric thin film and sequentially performing a degreasing process and a crystallization process,
When the mass of the treated material 1 after the degreasing treatment is represented by mass A and the mass of the treated material 2 after the crystallization treatment is represented by mass B, the reduction rate defined by the following formula (1) is 5 0.0% or more and 6.5% or less,
A solution for forming a ferroelectric thin film, comprising:
Reduction rate = {(mass A−mass B) / mass A} × 100 (%) Formula (1)

  According to the present invention, there is provided a solution for forming a ferroelectric thin film, which can obtain a ferroelectric thin film having good piezoelectric characteristics without variation.

FIG. 2 is an exploded perspective view schematically illustrating an example of the liquid ejection head according to the invention. It is a cross section of an example of a piezoelectric element concerning the present invention. FIG. 2 is a schematic cross-sectional view of an example of a liquid ejection head according to the present invention. FIG. 2 is a schematic view illustrating an example of an apparatus for discharging a liquid according to the present invention. It is a schematic diagram which shows the other example of the apparatus which discharges the liquid which concerns on this invention. FIG. 3 is a schematic diagram illustrating an example of a liquid ejection unit according to the present invention. FIG. 9 is a schematic view illustrating another example of the liquid ejection unit according to the present invention. FIG. 3 is a flowchart for explaining a procedure for preparing a solution (precursor solution) for forming a ferroelectric thin film of the present invention. FIG. 3 is a schematic cross-sectional view for explaining a liquid ejection head used in an example. It is the result of analyzing the amount of Pb in the PZT film in the example by SIMS. 5 is a result of analyzing the amount of Zr in the PZT film in Example by SIMS. 4 is a result of analyzing the amount of Ti in the PZT film in the example by SIMS. FIG. 3 is a view showing the result of Tg-DTA analysis of a precursor solution in an example. It is a figure which shows the result of FT-IR analysis when the precursor solution in an Example is processed at different temperature. 6 is a graph showing the relationship between the reduction rate of the precursor solution and the displacement of the diaphragm in non-defective products and non-defective products of Examples.

Hereinafter, embodiments of the present invention will be described.
In the following embodiments, a case where a PZT film is used as a ferroelectric thin film will be described.
First, a series of chemical reaction formulas shown in the following description will be described.

(1) Dehydration of lead acetate
Pb (OOCCH ₃ ) ₂・ 3H ₂ O → Pb (OOCCH ₃ ) ₂ + 3H ₂ O ↑
(Lead acetate trihydrate) (lead acetate) ((desorption) water of crystallization)

(2) Substitution reaction between lead acetate acetate group and (alcohol group of) 2-methoxyethanol
Pb (OOCCH ₃ ) ₂ + 2CH ₃ O-CH ₂ CH ₂ OH
(2-methoxyethanol)
→ CH ₃ -COO-Pb-OCH ₂ CH ₂ OCH ₃ + CH ₃ CO-OCH ₂ CH ₂ -OCH ₃ + H ₂ O
(Lead-2-methoxyethyl acetate) (2-methoxyethyl acetate)

(3) Alcohol exchange reaction between zirconium propoxide and 2-methoxyethanol
Zr [O- (CH ₂ ) ₂ CH ₃ ] ₄ + 4CH ₃ O-CH ₂ CH ₂ OH
(Zirconium n-propoxide)
→ Zr [-OCH ₂ CH ₂ OCH ₃ ] ₄ + 4CH ₃ (CH ₂ ) ₂ OH
(Zirconium 2-methoxyethoxide) (n-propanol)

(4) Alcohol exchange reaction between titanium i-propoxide and 2-methoxyethanol
Ti [O- (CH ₂ ) ₂ CH ₃ ] ₄ + 4CH ₃ O-CH ₂ CH ₂ OH
(Titanium i-propoxide)
→ Zr [-OCH ₂ CH ₂ OCH ₃ ] ₄ + 4 (CH ₃ ) ₂ CHOH
(Titanium 2-methoxyethoxide) (i-propanol)

(5) ester reaction to form n-propyl acetate
CH ₃ COOH + CH ₃ (CH ₂ ) ₂ OH → CH ₃ COO (CH ₂ ) ₂ CH ₃ + H ₂ O
(N-propyl acetate)

(6) Ester reaction to form i-propyl acetate
CH ₃ COOH + CH ₃ (CH ₂ ) ₂ OH → CH ₃ COOCH (CH ₃ ) ₂ + H ₂ O
(I-propyl acetate)

A known method for obtaining a ferroelectric thin film forming solution (hereinafter sometimes referred to as a precursor solution) used for obtaining a PZT film by a conventional sol-gel method is to use lead acetate trihydrate as a starting material. , Zirconium propoxide, titanium isopropoxide, and 2-methoxyethanol as a common solvent (for example, Non-Patent Document 1: M. Sayer, G Yi, M Sedlar “Comparative Sol-Gel Processing of PZT Thin Films”) , Integrated Ferroelectrics, 7, 1995, pp. 247-258).
In the above method, first, the crystalline powder of lead acetate trihydrate was weighed in accordance with the target stoichiometric ratio, dissolved in 2-methoxyethanol as a common solvent, and further heated to desorb water of crystallization. After (dehydration step), a solution obtained by adding zirconium propoxide and titanium isopropoxide weighed in accordance with a target stoichiometric ratio and further heating for a predetermined time is cooled to room temperature, weighed, and weighed. A common solvent is added so as to have a concentration, and a predetermined stabilizer is added to obtain a precursor solution having a desired PZT composition.

  In the precursor solution synthesis process described above, in the first half dehydration step, water of crystallization of lead acetate trihydrate is desorbed and taken out of the reaction system together with the common solvent (chemical reaction formula (1)) together with "dehydration" As shown in chemical reaction formula (2), one of the two acetic acid groups bonded to the lead element is replaced with the alcohol group of 2-methoxyethanol as the solvent, and at the same time, the acetic acid group separated from the lead element is 2-methoxyethanol and ester. (Non-Patent Document 2: Sangeeta D. Ramamurithi and David A. Payne “Structural Investigations of Prehydrolyzed Precursors Used in the Sol-Gel Processing of Lead Titanate”, J. Am. Ceram. Soc., 73 (8 ), 1990, pp. 2547-51).

  In the latter half of the precursor solution synthesis reaction to which zirconium propoxide and titanium isopropoxide were added, the (lower) alcohol group originally bonded to zirconium and titanium was replaced with 2-methoxyethanol (higher boiling point) solvent. (The so-called “alcohol exchange reaction”), taking out the lower alcohols away from zirconium and titanium together with the common solvent to the outside of the reaction system, and lower alcohols away from zirconium and titanium and the acetic acid groups away from lead element. And an ester reaction occurs (chemical reaction formulas (3) to (6)).

As described above, PZT films with good piezoelectric properties and those with poor piezoelectric properties were analyzed by secondary ion mass spectrometry (SIMS) and differential thermogravimetric analysis (Tg-DTA). As a result, it was found that there was a difference in the amount of Pb contained in the PZT film. The present inventors further studied and found that the heating during the crystallization treatment changed the bonding state and coordination state of the molecules in the liquid, resulting in a difference in the ease with which lead could escape, and as a result, the PZT film It was presumed that the composition ratio in the composition had fluctuated. Therefore, the present inventors performed detailed analysis (NMR measurement) on a large number of precursor solution synthesis batches in the precursor solution synthesis process, and as a result, the chemical reaction formulas (1) to (6). ), Especially the reaction progress in which one of the two acetic acid groups bonded to the lead element is replaced with the alcohol group of 2-methoxyethanol as the solvent shown in chemical reaction formula (2). It was found that the fluctuations were relatively large. In addition, the precursor solution in which the degree of progress of the chemical reaction formula (2) is recognized to be low is relatively high in the ratio of the lead element remaining in the form of lead acetate. According to the analysis, the weight loss ratio during the analysis was small, and further, in the PZT film formed using such a precursor solution, an excessive amount of lead element remained, and its crystallinity and film characteristics were It was confirmed that it was inferior to the desired quality.
From the above, when the precursor solution was heated and the degreasing process and the crystallization process were sequentially performed, by measuring the rate of decrease in the mass of the processed product before and after the crystallization process, the ease with which lead as a precursor solution escaped was measured. As a result, according to the present invention, a ferroelectric thin film having good piezoelectric characteristics can be obtained without variation.

From the above knowledge, the solution for forming a ferroelectric thin film of the present invention (precursor solution) contains lead, zirconium and titanium, and when the precursor solution is heated to sequentially perform a degreasing treatment and a crystallization treatment, When the mass of the treated material 1 after the degreasing treatment is represented by mass A and the mass of the treated material 2 after the crystallization treatment is represented by mass B, the reduction rate defined by the following formula (1) is 5 0.0% or more and 6.5% or less.
Reduction rate = {(mass A−mass B) / mass A} × 100 (%) Formula (1)

Typically, the degreasing treatment is performed at 300 ° C., and the degreasing treatment is terminated when the variation rate of the mass reduction of the precursor solution becomes 0.05% or less over 30 minutes, and the temperature rising rate is changed from the state. The temperature is raised to 700 ° C. at a rate of 10 ° C./min to perform a crystallization treatment, and the reduction rate of the obtained precursor solution defined by the formula (1) is 5.0% or more and 6.5% or less. Is preferred.
That is, the degreasing treatment is performed at 300 ° C. until the fluctuation rate of the mass decrease of the precursor solution reaches a constant value, and the temperature is increased at a rate of 10 ° C./min for the crystallization treatment simultaneously with the completion of the degreasing treatment. Then, when the precursor solution reaches 700 ° C. (at this point, the precursor solution is in the form of a powder), the crystallization process ends.

Further, according to the study of the present inventors, in order to obtain a ferroelectric thin film having good piezoelectric properties as a precursor solution that can be obtained without variation, the relationship between the amount of lead added excessively and the reduction rate is considered. Has been found to be effective. Specifically, it is preferable to satisfy the following expression (2).
{17.86 / (207.2 × α + 323.5)} × 100 ≦ reduction rate (%) ≦ {22.32 / (207.2 × α + 323.5)} × 100 Equation (2)
In the formula (2), α is the amount of lead (mol%) added excessively to the desired amount of lead in the ferroelectric thin film.

FIG. 8 is a flow chart for explaining a procedure for preparing a solution (precursor solution) for forming a ferroelectric thin film of the present invention.
First, as described above, the crystal powder of lead acetate trihydrate is weighed in accordance with a target stoichiometric ratio, and 2-methoxyethanol as a common solvent is added to dissolve lead acetate trihydrate (S1). ).

  The precursor solution contains Pb having a composition equal to or higher than the MPB composition to prevent composition deviation. For example, Pb is added to the precursor solution in excess of, for example, 5 to 25 mol%, preferably 10 to 11 mol%, relative to a target stoichiometric ratio.

  Next, the obtained solution is heated while controlling the reaction atmosphere, the solution temperature (for example, 125 ° C. to 135 ° C.) and the reaction time (for example, 8 hours to 24 hours) to remove water of crystallization, and lead acetate is added. At the same time as dehydration of the trihydrate, a substitution reaction between a lead acetate acetate group and (alcohol group of) 2-methoxyethanol is performed (S2). At this time, the solution is refluxed, and a distillate (solvent, water of crystallization, ester) is recovered.

  Next, zirconium propoxide and titanium isopropoxide are weighed in accordance with a target stoichiometric ratio, and are added to the solution (S3).

  Subsequently, the mixture is heated while controlling the reaction atmosphere, the solution temperature (for example, 125 ° C. to 132 ° C.) and the reaction time (for example, 6 hours to 16 hours), and the alcohol exchange reaction between zirconium propoxide and 2-methoxyethanol and titanium An alcohol exchange reaction between i-propoxide and 2-methoxyethanol is performed (S4). At this time, the solution is refluxed, and a distillate (solvent, water of crystallization, ester) is recovered.

  Next, 2-methoxyethanol and acetic acid are added as a stabilizer to obtain a precursor solution having a desired PZT composition (S5). The obtained precursor solution is subjected to filtering and sealing as necessary.

Subsequently, the precursor solution is applied on an underlayer such as an orientation control layer described below, and then subjected to a degreasing treatment and a crystallization treatment. The coating may be performed once, but the coating, the degreasing treatment and the crystallization treatment may be repeated plural times.
As the degreasing treatment conditions, the heating temperature is, for example, 80 to 160 ° C, preferably 110 to 130 ° C, and the degreasing time is, for example, 1 minute to 10 minutes, preferably 2 minutes to 4 minutes.
As the crystallization conditions, the heating temperature is, for example, 650 to 750 ° C, preferably 680 to 710 ° C, and the crystallization time is, for example, 1 minute to 10 minutes, preferably 2 minutes to 4 minutes.

  Subsequently, the reduction rate is calculated from the mass of the precursor solution before and after the crystallization treatment based on the above formula (1). If the reduction rate defined by the equation (1) is 5.0% or more and 6.5% or less, the above-mentioned MPB composition or a PZT film close to the MPB composition can be obtained without variation.

The PZT film is preferably a ferroelectric thin film of a perovskite crystal represented by PbZr _X Ti _(1-X) O ₃ (0.40 <x ≦ 0.60), and has an MPB composition represented by PbZr _0.53 Ti _0.47 O ₃ Is optimal.

Next, the ferroelectric thin film, the piezoelectric element, the liquid discharge head, the liquid discharge unit, the liquid discharge device, and the piezoelectric device of the present invention will be described.
The ferroelectric thin film of the present invention is formed using a solution for forming a ferroelectric thin film.
The piezoelectric element of the present invention is provided with electrodes on the upper and lower surfaces of the ferroelectric thin film of the present invention, respectively.
The liquid discharge head according to the present invention includes a nozzle substrate having a nozzle hole for discharging liquid, a flow path forming substrate having a pressurized liquid chamber communicating with the nozzle hole, and at least one wall of the pressurized liquid chamber. And a piezoelectric element of the present invention on the diaphragm.
A liquid discharge unit according to the present invention includes the liquid discharge head according to the present invention.
A liquid discharge apparatus according to the present invention includes the liquid discharge head or the liquid discharge unit according to the present invention.
The piezoelectric element of the present invention includes the piezoelectric element of the present invention.

First, FIG. 1 shows an exploded perspective view of an embodiment of a liquid ejection head according to the present invention.
FIG. 1 shows a nozzle hole 79, a nozzle substrate 80, a pressurized liquid chamber 70 (also referred to as a cavity), a flow path forming substrate 71, a common liquid chamber 72, and a vibration plate 11 (also referred to as a film forming vibration plate or the like). ), And the piezoelectric thin film element 73 is shown. Also, a subframe 76 having an actuator part escape 74A is shown.

  The liquid discharge head of the present embodiment has a plurality of piezoelectric thin film elements 73 mounted thereon and a plurality of pressurized liquid chambers 70. In addition, the liquid ejection head of the present embodiment is provided with a common liquid chamber 72 that communicates with each of the plurality of pressurized liquid chambers 70.

  A pressurized liquid chamber 70 and a common liquid chamber 72 are formed in the flow path forming substrate 71, and a sub-frame 76 having an actuator escape 74A provided so that the piezoelectric thin film element 73 can enter and be driven is joined. You. In addition, an ink flow path 74B is provided in the sub frame 76, and the ink flow path 74B is connected to the common liquid chamber 72 when the sub frame 76 is joined to the flow path forming substrate 71.

  A nozzle substrate 80 having a plurality of nozzle holes 79 is joined to the flow path forming substrate 71. When the nozzle substrate 80 and the flow path forming substrate 71 are joined, each nozzle hole 79 is They are arranged at corresponding positions. The pressure is generated in the pressurized liquid chamber 70 by the piezoelectric thin film element 73 having the ferroelectric thin film (hereinafter, referred to as a PZT film laminated structure) of the present invention, and the liquid is discharged from the nozzle hole 79.

One embodiment of the PZT film laminated structure according to the present invention will be described with reference to FIG. Further, a liquid ejection head having the PZT film laminated structure of the present embodiment will be described with reference to FIG. 2 and 3 schematically show cross sections.
FIG. 2 shows a substrate 10, a vibration plate 11, a base film 20 (adhesion layer 21, lower electrode 22, orientation control layer 23), piezoelectric film 30 (PZT film), upper electrode 40 (conductive oxide layer 41, The upper electrode layer 42) and the protective layer 50 are illustrated. FIG. 3 shows a nozzle hole 79, a nozzle substrate 80, and a pressurized liquid chamber 70. Each configuration will be described.

<Substrate>
As the substrate 10, a silicon single crystal substrate is preferably used, and preferably has a thickness of 100 to 600 μm. As the plane orientation, there are three kinds, (100), (110), and (111), and (100) and (111) are widely used in the semiconductor industry. In this embodiment, a single crystal substrate having a (100) plane orientation is mainly used.

  When the pressurized liquid chamber 70 as shown in FIG. 3 is formed, a silicon single crystal substrate is processed by using etching. In this case, anisotropic etching is generally used. It is.

Anisotropic etching utilizes the property that the etching rate varies with the plane orientation of the 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 54.74 ° can be manufactured in the plane orientation (100), while a deep groove can be formed in the plane orientation (110). Can be higher. In the present embodiment, it is also possible to use a single crystal substrate having a (110) plane orientation. However, in this case, since it is mentioned that SiO ₂ as a mask material is also etched, it is preferable to use this area with care.

<Vibration plate>
As shown in FIG. 3, the diaphragm 11 is deformed and displaced by the force generated by the piezoelectric film 30 as shown in FIG. Therefore, it is preferable that the diaphragm 11 has a predetermined strength.
The diaphragm 11 may be formed of a single material, or may be formed by stacking a plurality of films of a plurality of materials.

  Examples of the method for forming the vibration plate 11 include a sputtering method, a combination of a sputtering method and a thermal oxidation method, and a MOCVD (Metal Organic Chemical Vapor Deposition) method. In the present embodiment, when the layers are stacked, those manufactured by the LPCVD (Low Pressure CVD) method are used. A diaphragm made of a film formed by the LPCVD method is a film generally applied to semiconductors and MEMS devices from the past, and is easy to process. Therefore, it is preferable because it does not introduce a new process problem. . Further, a stable diaphragm can be obtained without using an expensive substrate such as an SOI (Silicon on Insulator).

The surface roughness of the diaphragm 11 is preferably 4 nm or less in arithmetic average roughness. If it exceeds this range, the PZT film formed thereafter has a very poor dielectric breakdown voltage, and may easily leak.
Examples of the material of the diaphragm 11 include polysilicon, a silicon oxide film, a silicon nitride film, and a combination thereof.

An example of the diaphragm 11 will be described.
First, a silicon oxide film (for example, with a thickness of 200 nm) is formed on a silicon single crystal substrate having a (100) plane orientation as a diaphragm constituting film by, for example, an LPCVD method (or a heat treatment film forming method), and then a polysilicon film is formed. A film (for example, 500 nm thick) is formed. It is desirable that the thickness of the polysilicon layer is 0.1 to 3 μm and the surface roughness is 5 nm or less in arithmetic average roughness. Next, a silicon nitride film is formed as a diaphragm constituent film by an LPCVD method.

<Undercoat>
Next, the base film 20 formed on the diaphragm 11 will be described. As shown, the adhesion layer 21, the lower electrode 22, and the orientation control layer 23 form a base film 20, and the orientation control layer 23 is particularly important because it affects the crystallinity of the piezoelectric film 30. .

The adhesion layer 21 does not necessarily need to be laminated, but when platinum (Pt) or the like is used for the lower electrode 22, the adhesion to the diaphragm 11 is taken into consideration, and Ti, TiO ₂ , Ta, It is preferable to laminate an adhesion layer 21 made of Ta ₂ O ₅ , Ta ₃ N ₅ or the like. As a method for forming the adhesion layer 21, a vacuum film formation such as a sputtering method or a vacuum deposition is generally used.

The thickness of the base film 20 is preferably 20 to 500 nm, more preferably 100 to 300 nm.
The thickness of the adhesion layer 21 is preferably 50 to 90 nm.
The thickness of the lower electrode 22 is preferably 140 to 200 nm.
The thickness of the orientation control layer 23 is preferably 5 to 10 nm.

  As a material of the lower electrode 22, Pt having a high (111) orientation is preferable, and a Pt film having a high peak intensity can be obtained when the crystallinity of the Pt is evaluated by X-ray diffraction.

  An orientation control layer 23 is formed on the lower electrode 22. As the orientation control layer, titanium oxide or lead titanate is preferable. The titanium oxide film is preferable because it can react with PZT of the sol-gel liquid laminated thereon and generate a Ti-rich PZT film. The Ti-rich film serves as a crystal source of PZT (100), and can form a (100) or (001) main orientation of the PZT film to be laminated.

  The orientation control layer 23 may not be a titanium oxide film but may be a direct lead titanate. Lead titanate is preferable because it directly functions as a crystal source of PZT (100) and can form the (100) or (001) main orientation of the stacked PZT film.

<PZT film>
Next, the piezoelectric film 30 (PZT film) according to the present embodiment will be described.
The piezoelectric film 30 can be made from the solution for forming a ferroelectric thin film of the present invention.

  The piezoelectric film 30 can be manufactured by a spin coater using a sputtering method or a sol-gel method. In that case, patterning is required, so that a desired pattern is obtained by photolithographic etching or the like.

  In the present invention, a sol-gel method is particularly preferable. When a PZT film is formed by a sol-gel method, a PZT film precursor solution is applied to the orientation control layer 23 and baked. The PZT film may be a single layer, but is preferably formed by repeating coating and firing. That is, a step of repeating the application and baking of the precursor solution a plurality of times is performed to form a PZT film. In this case, it is preferable to perform a step of repeating the application and baking of the precursor solution a plurality of times, and after this step, further heat to form a PZT film.

  This is also referred to as two-stage firing. As the firing after the spin coating of the sol-gel liquid, it is preferable to perform a two-stage firing of heating for releasing organic components (first stage) and heating at a higher temperature for crystallizing the film (second stage). . The first-stage heating is performed for each spin coating. After the first-stage heating similar to the second-layer and third-layer heating, the three-layer baking is performed at the second-stage higher temperature.

When PZT is prepared by a sol-gel method, a PZT precursor solution can be prepared by using a lead acetate, zirconium alkoxide, or titanium alkoxide compound as a starting material and dissolving it in methoxyethanol as a common solvent to obtain a homogeneous solution.
Since the metal alkoxide compound is easily hydrolyzed by atmospheric moisture, an appropriate amount of a stabilizer such as acetylacetone, acetic acid, or diethanolamine may be added to the precursor solution.
The alkoxide is preferably methoxy ethoxide, and the precursor solution preferably contains lead acetate, methoxy ethoxide of Ti, and methoxy ethoxide of Zr.

  When a PZT film is obtained over the entire surface of the base, a PZT film is obtained by forming a coating film by a solution coating method such as spin coating, and performing each heat treatment of solvent drying, thermal decomposition, and crystallization. Since the transformation from a coating film to a crystallized film involves volume shrinkage, it is preferable to adjust the concentration of the precursor solution so as to obtain a film thickness of 100 nm or less in a single step in order to obtain a crack-free film. .

  The thickness of the PZT film is preferably 0.5 to 5 μm, and more preferably 1 to 2 μm. If it is smaller than the above range, a sufficient displacement cannot be generated, and if it is larger than the above range, when multiple layers are stacked, the number of steps increases and the process time becomes longer.

<Upper electrode>
The upper electrode 40 of the present embodiment includes a conductive oxide layer 41 and an upper electrode layer 42. The upper electrode is not particularly limited, and examples thereof include materials generally used in a semiconductor process, such as Al and Cu, and combinations thereof. The conductive oxide layer 41 and the upper electrode layer 42 are not particularly limited. However, the conductive oxide layer 41 has good adhesion to PZT and has the same perovskite structure as SRO (SrRuO3). ) Is preferable, and Pt is preferable as the upper electrode layer 42.
The thickness of the conductive oxide layer 41 is preferably 35 to 50 nm.
The thickness of the upper electrode layer 42 is preferably 100 to 150 nm.

<Protective layer>
Examples of the material of the protective layer 50 include aluminum oxide and tantalum oxide.
The thickness of the protective layer 50 is preferably 40 to 70 nm.
The protective layer 50 can be formed by, for example, an ALD (Atomic Layer Deposition) method.

(Liquid discharge device, liquid discharge unit)
Next, an example of the liquid ejection apparatus according to the present invention will be described with reference to FIGS. FIG. 4 is an explanatory plan view of an essential part of the device, and FIG. 5 is an explanatory side view of an essential part of the device.

  This device is a serial type device, and the carriage 403 reciprocates in the main scanning direction by the main scanning moving 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 is bridged between the left and right side plates 491A and 491B, and movably holds the carriage 403. The carriage 403 is reciprocated in the main scanning direction by the main scanning motor 405 via a timing belt 408 spanned between the driving pulley 406 and the driven pulley 407.

  On the carriage 403, a liquid discharge unit 440 in which the liquid discharge head 404 and the head tank 441 according to the present invention are integrated is mounted. The liquid discharge head 404 of the liquid discharge unit 440 discharges, for example, liquid of each color of yellow (Y), cyan (C), magenta (M), and black (K). The liquid ejection head 404 has a nozzle row composed of a plurality of nozzles 11 arranged in a sub-scanning direction orthogonal to the main scanning direction, and is mounted with the ejection direction facing downward.

  The liquid stored in the liquid cartridge 450 is supplied to the head tank 441 by a supply mechanism 494 for supplying the liquid stored outside the liquid discharge head 404 to the liquid discharge head 404.

  The supply mechanism 494 includes a cartridge holder 451, which is a filling section for mounting the liquid cartridge 450, a tube 456, a liquid sending unit 452 including a liquid sending pump, and the like. The liquid cartridge 450 is detachably mounted on the cartridge holder 451. The liquid is sent from the liquid cartridge 450 to the head tank 441 by the liquid sending unit 452 via the tube 456.

  This apparatus includes a transport mechanism 495 for transporting the sheet 410. The transport mechanism 495 includes a transport belt 412 as transport means, and a sub-scanning motor 416 for driving the transport belt 412.

  The transport belt 412 attracts the paper 410 and transports the paper 410 at a position facing the liquid ejection head 404. The transport belt 412 is an endless belt, and is stretched between a transport roller 413 and a tension roller 414. Suction can be performed by electrostatic suction or air suction.

  The transport belt 412 is rotated in the sub-scanning direction by rotating the transport roller 413 via the timing belt 417 and the timing pulley 418 by the sub-scanning motor 416.

  Further, on one side of the carriage 403 in the main scanning direction, a maintenance and recovery mechanism 420 for maintaining and recovering the liquid ejection head 404 is arranged on the side of the transport belt 412.

  The maintenance and recovery mechanism 420 includes, for example, a cap member 421 for capping the nozzle surface (the surface on which the nozzle 11 is formed) of the liquid ejection head 404, a wiper member 422 for wiping 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 and 491B and a back plate 491C.

  In this apparatus configured as described above, the paper 410 is fed onto the transport belt 412 and is adsorbed, and the paper 410 is transported in the sub-scanning direction by the orbital movement of the transport belt 412.

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

  As described above, since this apparatus includes the liquid ejection head according to the present invention, a high-quality image can be stably formed.

  Next, another example of the liquid ejection unit according to the present invention will be described with reference to FIG. FIG. 6 is an explanatory plan view of a main part of the unit.

  The liquid discharge unit includes a housing portion including side plates 491A and 491B and a back plate 491C, a main scanning moving mechanism 493, a carriage 403, It comprises a discharge head 404.

  In addition, a liquid discharge unit in which at least one of the above-described maintenance and recovery mechanism 420 and the supply mechanism 494 is further attached to, for example, the side plate 491B of the liquid discharge unit may be configured.

  Next, still another example of the liquid ejection unit according to the present invention will be described with reference to FIG. FIG. 7 is an explanatory front view of the unit.

  The liquid discharge unit includes a liquid discharge head 404 to which a flow path component 444 is attached, and a tube 456 connected to the flow path component 444.

  The flow path component 444 is disposed inside the cover 442. A head tank 441 may be included instead of the flow path component 444. Further, a connector 443 for making an electrical connection with the liquid ejection head 404 is provided above the flow path component 444.

  In the present invention, the “liquid ejection device” is a device that includes a liquid ejection head or a liquid ejection unit, and drives the liquid ejection head to eject liquid. The device that discharges a liquid includes not only a device that can discharge a liquid to which a liquid can be attached, but also a device that discharges a liquid into the air or into the liquid.

  The “device for discharging liquid” may include a unit for feeding, transporting, and discharging paper to which liquid can be attached, as well as a pre-processing device and a post-processing device.

  For example, as a "device for ejecting liquid", an image forming apparatus that ejects ink to form an image on paper, and a powder is formed in layers to form a three-dimensional object (three-dimensional object) There is a three-dimensional modeling device (three-dimensional modeling device) that discharges a modeling liquid to the formed powder layer.

  Further, the “device for discharging liquid” is not limited to a device in which a significant image such as a character or a graphic is visualized by the discharged liquid. For example, those that form a pattern or the like that has no meaning in itself, and those that form a three-dimensional image are also included.

  The above-mentioned "thing to which a liquid can be attached" means a thing to which a liquid can be attached at least temporarily, such as a thing which is attached and fixed, a thing which is attached and penetrates, and the like. Specific examples include recording media such as paper, recording paper, recording paper, film, and cloth; electronic components such as electronic substrates and piezoelectric elements; powder layers (powder layers); organ models; and media such as inspection cells. Yes, unless otherwise specified, includes everything to which a liquid adheres.

  The material of the above-mentioned "thing to which the liquid can be attached" may be paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, etc. as long as the liquid can be attached even temporarily.

  The “liquid” also includes inks, processing liquids, DNA samples, resists, pattern materials, binders, modeling liquids, or solutions and dispersions containing amino acids, proteins, and calcium.

  Further, the “liquid ejection device” includes a device in which the liquid ejection head and the device to which the liquid can adhere are relatively moved, but the invention is not limited to this. Specific examples include a serial device that moves the liquid ejection head, a line device that does not move the liquid ejection head, and the like.

  In addition, as the “liquid ejection device”, there are also a treatment liquid application device that ejects a treatment liquid onto the paper in order to apply the treatment liquid to the surface of the paper for the purpose of modifying the surface of the paper, etc. There is an injection granulating apparatus that granulates fine particles of raw materials by spraying a composition liquid dispersed therein through a nozzle.

  The “liquid discharge unit” is a unit in which functional components and mechanisms are integrated with a liquid discharge head, and is an assembly of components related to liquid discharge. For example, the “liquid ejection unit” includes a combination of at least one of a head tank, a carriage, a supply mechanism, a maintenance and recovery mechanism, and a main scanning movement mechanism with a liquid ejection head.

  Here, the term “integration” means, for example, a case where the liquid ejection head and the functional component or mechanism are fixed to each other by fastening, bonding, engagement, or the like, or a case where one is movably held with respect to the other. Including. Further, the liquid ejection head, the functional component, and the mechanism may be configured to be detachable from each other.

  For example, as a liquid discharge unit, there is a liquid discharge unit in which a liquid discharge head and a head tank are integrated as in a liquid discharge unit 440 shown in FIG. In some cases, the liquid ejection head and the head tank are integrated with each other by a tube or the like. Here, a unit including a filter can be added between the head tank and the liquid discharge head of these liquid discharge units.

  There is a liquid discharge unit in which a liquid discharge head and a carriage are integrated.

  Further, as a liquid discharge unit, there is a liquid discharge head in which a liquid ejection head is movably held by a guide member constituting a part of a scanning movement mechanism, and the liquid ejection head and the scanning movement mechanism are integrated. As shown in FIG. 6, there is a liquid discharge unit in which a liquid discharge head, a carriage, and a main scanning moving mechanism are integrated.

  Further, as a liquid discharge unit, there is a liquid discharge head in which a cap member, which is a part of a maintenance and recovery mechanism, is fixed to a carriage to which a liquid discharge head is attached, and the liquid discharge head, the carriage, and the maintenance and recovery mechanism are integrated. .

  Also, as shown in FIG. 7, there is a liquid discharge unit in which a tube is connected to a liquid discharge head to which a head tank or a flow path component is attached, and a liquid discharge head and a supply mechanism are integrated. .

  The main scanning movement mechanism includes a guide member alone. The supply mechanism also includes a tube unit and a loading unit alone.

  Further, the "liquid ejection head" is not limited to the pressure generating means used. For example, in addition to the piezoelectric actuator described in the above embodiment (a laminated piezoelectric element may be used), a thermal actuator using an electrothermal conversion element such as a heating resistor, a diaphragm and a counter electrode are provided. An actuator using an electrostatic actuator or the like may be used.

  In the terms of the present invention, image formation, recording, printing, printing, printing, modeling, and the like are all synonyms.

  The piezoelectric device of the present invention includes the piezoelectric element of the present invention, and includes an actuator, a sensor, a speaker, an ultrasonic motor, an optical device, a vibration device, in addition to the above-described liquid ejection head, liquid ejection unit, and liquid ejection device. Device, an imaging device, and the like.

  Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited to the following examples. The following embodiment is an example in which a PZT film is used as a ferroelectric thin film.

(Synthesis of precursor solution)
In this embodiment, a precursor solution composed of Pb, Zr, and Ti using a sol-gel method will be described.In general, for improving the characteristics, V, Nb, Ta, Sb, Mo, W, K, Na, and Li are used. , Bi, La, Ba, and other elements can also be added. The other elements can be contained, for example, in the PZT film in an amount of, for example, 0 to 20 mol%.

A precursor solution was synthesized based on the chemical reaction formulas (1) to (6) and the flow shown in FIG.
As starting materials, lead acetate trihydrate Pb (CH ₃ COO) ₂ .3H ₂ O, zirconium tetranormal propoxide Zr (OCH ₂ CH ₂ CH ₃ ) ₄ , titanium tetraisopropoxide Ti [OCH (CH _{3 2} ) ₄ was used.
Using these starting materials, a stoichiometric composition of Pb (Zr _0.53 Ti _0.47 ) O ₃ , commonly referred to as PZT (53/47), of lead zirconate titanate is used. Synthesis was performed. Generally, when producing a lead-containing composite oxide such as PZT, lead is supposed to be removed during the heat treatment, and Pb is added to the starting material by about 5 to 25 mol% as compared with the stoichiometric composition as described above. It is common to add in excess. In the first embodiment, the starting materials were weighed so that the composition was such that the lead content was 10 mol% excess, that is, Pb _1.10 (Zr _0.53 Ti _0.47 ) O ₃ .
After weighing, first, lead acetate trihydrate is dissolved in ₂ -methoxyethanol CH ₃ OCH ₂ CH ₂ OH, and the mixture is heated and refluxed at the boiling point of the solvent to perform dehydration of the hydrate and alcohol exchange of lead acetate. went.
Subsequently, zirconium tetranormal propoxide and titanium tetraisopropoxide are added to a 2-methoxyethanol solution of the lead acetate subjected to the dehydration / alcohol exchange treatment, and the mixture is heated and refluxed to carry out an alcohol exchange reaction and a polycondensation reaction. Let it go. The retention time after reaching the solvent boiling point is 12 hours. Finally, a trace amount of acetic acid CH ₃ COOH was added as a stabilizer.

Here, the liquid ejection head used in this embodiment will be described. FIG. 9 is a schematic sectional view for explaining the liquid ejection head used in this embodiment.
The liquid discharge head includes a first electrode 205, a second electrode 207, an actuator 206, a vibration plate 202, a substrate 201, a pressure chamber 204 surrounded by an inner wall of the substrate, and a pressure sealing plate 203 having discharge holes.
As a material of the substrate 201, a silicon single crystal substrate having a (100) plane orientation was used.
The vibration plate 202 preferably has a predetermined strength in order to receive a force generated by the PZT film as the actuator 206 and to deform and displace and eject ink droplets in the pressure chamber. Examples of the material include, in addition to the above-described materials, Si, SiO ₂ , and Si ₃ N ₄ produced by a CVD method. Also, considering the use of a PZT film, diaphragm 202 has a linear expansion coefficient of 5 × 10 ⁻⁶ to 10 × 10 ⁻⁶ as a linear expansion coefficient close to 8 × 10 ⁻⁶ (1 / K). Is preferable, and a material having a linear expansion coefficient of 7 × 10 ^{−6 to} 9 × 10 ⁻⁶ is more preferable. Further, it is desirable that the diaphragm 202 is constructed by stacking a plurality of films having a tensile stress or a compressive stress by LPCVD. The reason is that an SOI wafer is used in the case of a single-layer film, but in that case, the wafer cost 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 a laminated diaphragm, by optimizing the laminated structure, it is possible to obtain a degree of freedom to set the rigidity and the film stress of the diaphragm to desired values, and thus to control the rigidity and stress of the entire diaphragm. Can be realized by a combination of lamination, its film thickness, and lamination structure. Accordingly, the material and film thickness of the piezoelectric element (electrode layer, ferroelectric layer) can be appropriately adjusted, and a stable diaphragm with little fluctuation in the rigidity and stress of the diaphragm due to the firing temperature of the piezoelectric element can be obtained. The droplet ejection characteristics can be made highly accurate, and a stable liquid ejection head can be realized.

The first electrode 205 is composed of a metal material, an adhesion layer, and a conductive oxide layer. As the metal material, platinum having high heat resistance and low reactivity has been used, but a sufficient barrier against lead has been used. In some cases, it may not be said that the alloy has a property, and platinum group elements such as iridium and platinum-rhodium, and alloy films thereof can also be used. When platinum is used, it is preferable to laminate platinum on Ti, TiO ₂ , Ta, Ta ₂ O ₅ , Ta ₃ N _5, or the like because adhesion to a base (particularly, SiO ₂ ) is poor. As a method for forming the first electrode 205, a vacuum film formation such as a sputtering method or a vacuum deposition is generally used, and the thickness is preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm. Platinum preferably has a (111) orientation as its crystallinity. Therefore, it is preferable to select platinum having high (111) orientation as the first electrode 205. Further, due to concerns about the fatigue characteristics over time of the displacement of the PZT film, a conductive oxide such as strontium ruthenate is preferably interposed between the first electrode 205 and the PZT film. The form was adopted.

  After applying the precursor solution prepared above on the first electrode 205 on a substrate such as a single crystal silicon substrate by using a spin coating method, solvent removal, degreasing treatment and crystallization treatment were sequentially performed. Usually, if the coating thickness per layer is too large, it will cause cracks. This process for one layer is repeated until a desired film thickness is obtained. Further, the occurrence of cracks may be prevented by, for example, performing the crystallization process once every several times without performing the crystallization process.

  In this example, the solvent was removed at 120 ° C., and the degreasing treatment was performed at 300 ° C. The crystallization treatment was performed under the condition of 700 ° C., and the crystallization treatment was performed by the RTA apparatus every time spin coating was performed three times. The thickness of the RZT film after performing spin coating, removing the solvent, and performing the degreasing treatment three times, and then performing the crystallization treatment, was 240 nm. This process was performed a total of 10 times (30 layers) to obtain a PZT film of about 2.0 μm.

  Similarly to the first electrode 205, the second electrode 207 is formed by using a metal material such as platinum and laminating a conductive oxide such as strontium ruthenate between platinum and the PZT film.

  Next, in order to form the pressure chamber 204, anisotropic wet etching is performed with an alkali solution (KOH solution or TMHA solution) to form a pressure chamber having a width in the lateral direction of 60 μm, as shown in FIG. Such a liquid discharge head was manufactured.

  Of the above liquid discharge heads, those satisfying the desired droplet discharge speed (good) and those not satisfying (defective) were analyzed by SIMS for the amounts of Pb, Zr, and Ti in the PZT films of various thicknesses. . The results are shown in FIGS. From the results of the SIMS analysis, it can be seen from the results of FIG. 10 in particular that the amount of Pb remaining in the PZT film is smaller in the non-defective product than in the defective product. Further, as shown in FIGS. 11 to 12, it can be seen that the amounts of Zr and Ti in the PZT film do not differ between good and defective products. In addition, the element concentration in the precursor solution, the process in the process, and the like are not changed between the liquid discharge heads. From the above, similarly to the result of the above-mentioned NMR measurement, the degree of progress of the reaction shown in the chemical reaction formulas (1) to (6), particularly, 2% bound to the lead element shown in the chemical reaction formula (2), According to the progress of the reaction in which one of the two acetic acid groups is replaced with the alcohol group of 2-methoxyethanol as a solvent, the amount of lead in the PZT film changes, which may cause non-defective and defective liquid ejection heads. Was guessed.

  Next, based on these results, Tg-DTA of various precursor solutions used for liquid ejection heads having different droplet ejection speeds was performed. The temperature profile and weight loss of Tg-DTA are shown in FIGS. 13 (a) and (b). In general, the temperature profile of Tg-DTA is to observe the differential heat and the weight change during heating at a constant heating rate. However, in this example, since the purpose is to observe only the weight loss due to lead loss in the high-temperature region, the precursor solution is sufficiently stable in a region higher than the temperature at which organic substances decompose and lower than the temperature at which crystallization starts. Need to be converted. In this example, a two-stage temperature profile was used so that the degreasing treatment was performed at 300 ° C., and after the decomposition of the organic matter was sufficiently completed, the material was heated to the temperature range of the crystallization treatment. However, depending on the type of the precursor solution, this temperature profile may not be in an optimal form. Therefore, it is preferable to set an optimal temperature profile by appropriately referring to differential heat. In the result shown in FIG. 13, a sharp weight loss occurs at around 300 ° C. from an initial slow weight loss. At this time, since the endothermic reaction is shown also in the differential heat, it is presumed that the organic matter is decomposed. Thereafter, even after the temperature reaches 300 ° C., the weight decreases gradually, and the weight becomes stable after about 100 minutes. That is, the degree of weight reduction with respect to the initial weight of the precursor solution is 0.05% or less over 30 minutes or more. Thereafter, no weight loss was observed up to around 450 ° C., which indicates that the organic matter was sufficiently decomposed.

FIG. 14 is a chart showing the results of FT-IR analysis of the precursor liquids processed at different temperatures. From FIG. 14, it can be seen that the peak around 3500 cm ^{−1 representing} a hydroxyl group peculiar to an organic substance disappears between 300 ° C. and 400 ° C., and most of the organic substance is decomposed at about 300 ° C. Further, it was found that a weight loss occurs with a rapid heat generation around 450 ° C. The rapid heat generation indicates that combustion and crystallization are progressing. Further, when Tg was measured, it was found that the combustion reaction due to the bonding with oxygen was progressing from the fact that the weight decreased once after the weight was slightly increased. It is presumed that at the time of heating after the degreasing treatment, the volatilization of lead has occurred along with the desorption of the adsorbed water and the remaining hydroxyl groups.

Based on the above findings, the present inventors have further conducted intensive studies. As a result, the degreasing treatment was performed at 300 ° C., and when the variation rate of the mass reduction of the precursor solution became 0.05% or less over 30 minutes, the degreasing was performed. When the treatment is completed and the temperature is raised from this state to 700 ° C. at a rate of 10 ° C./min to perform crystallization, the reduction rate of the obtained precursor solution defined by the above formula (1) is reduced. It was found that the effect of the present invention was further favorably exhibited when the content was 5.0% or more and 6.5% or less.
In this embodiment, the reduction rate of the precursor solution between the one satisfying the desired droplet discharge speed (non-defective product) and the one not satisfying the desired droplet discharge rate (defective product) is defined as 5.0 to 5.0 for the non-defective product. The result was 6.5%, and the defective product was out of the range.

  FIG. 15 is a graph showing the relationship between the reduction rate of the precursor solution defined by the formula (1) and the displacement of the diaphragm in the non-defective product and the defective product. In FIG. 15, the displacement amount is relatively expressed, and the reference value of the desired displacement is set to 1.00. There were a total of four precursor solutions, three of which formed non-defective products and one of which was defective. For four precursor solutions. Each displacement was examined three times. As a result, when the reduction rate of the precursor solution defined by the formula (1) is 5.0% or more and 6.5% or less as shown in FIG. 15, a non-defective product is formed. The solution was a defective product (displacement relative value = 0.94 or less). Further, a good correlation was confirmed between the reduction rate and the displacement amount. This result is consistent with the tendency of the amount of residual Pb in the PZT film in the non-defective product and the defective product, and it was found that the ease of lead removal affects the displacement characteristics. As described above, the displacement characteristics of the actuator can be more accurately managed by defining the reduction rate during the process in the precursor solution.

DESCRIPTION OF SYMBOLS 10 Substrate 11 Vibration plate 20 Base film 21 Adhesion layer 22 Lower electrode 23 Orientation control layer 30 Piezoelectric film 40 Upper electrode 41 Conductive oxide layer 42 Upper electrode layer 50 Protective layer 70 Pressurized liquid chamber 71 Flow path forming substrate 72 Common liquid chamber 73 Actuator section 74A Actuator section escape 74B Ink flow path 75 Fluid resistance 76 Subframe 79 Nozzle hole 80 Nozzle substrate 201 Substrate 202 Vibrating plate 203 Pressure sealing plate 204 Pressure chamber 205 First electrode 206 Actuator 207 Second electrode 401 Guide member 403 Carriage 404 Liquid discharge head 405 Main scanning motor 406 Drive pulley 407 Driven pulley 408 Timing belt 410 Paper 412 Transport belt 413 Transport roller 414 Tension roller 421 Cap member 422 Wiper member 440 Liquid discharge unit 44 Head tank 442 cover 443 connector 444 the channel part 450 liquid cartridge 451 cartridge holder 452 liquid-feeding unit 456 tubes 491A, 491B plate 491C backplate 493 main scan movement mechanism 494 supplying mechanism 495 transporting mechanism

JP 2015-207725 A JP 2017-157773 A Japanese Patent No. 6156068

Claims (10)

A ferroelectric thin film forming solution for forming a ferroelectric thin film,
The ferroelectric thin film forming solution contains lead, zirconium and titanium,
When heating the solution for forming a ferroelectric thin film and sequentially performing a degreasing process and a crystallization process,
When the mass of the treated material 1 after the degreasing treatment is represented by mass A and the mass of the treated material 2 after the crystallization treatment is represented by mass B, the reduction rate defined by the following formula (1) is 5 0.0% or more and 6.5% or less,
A solution for forming a ferroelectric thin film, comprising:
Reduction rate = {(mass A−mass B) / mass A} × 100 (%) Formula (1)   The degreasing process of the ferroelectric thin film forming solution is performed at 300 ° C., and the degreasing process is completed when the rate of change in mass decrease of the ferroelectric thin film forming solution becomes 0.05% or less over 30 minutes. From this state, the temperature was raised to 700 ° C. at a rate of 10 ° C./min to perform crystallization treatment, and the decrease rate of the obtained ferroelectric thin film forming solution defined by the above formula (1) was 5%. 2. The solution for forming a ferroelectric thin film according to claim 1, wherein the content is not less than 0.0% and not more than 6.5%. 3. The solution for forming a ferroelectric thin film according to claim 1, wherein the decrease rate is represented by the following equation (2).
{17.86 / (207.2 × α + 323.5)} × 100 ≦ reduction rate (%) ≦ {22.32 / (207.2 × α + 323.5)} × 100 Equation (2)
In the formula (2), α is the amount of lead (mol%) added excessively to the desired amount of lead in the ferroelectric thin film.   V, Nb, Ta, Sb, Mo, W, K, Na, Li, Bi, La and Ba, wherein one or more selected from the group consisting of further added, characterized in that it is further added. The solution for forming a ferroelectric thin film according to any one of the above.   A ferroelectric thin film formed using the solution for forming a ferroelectric thin film according to claim 1.   A piezoelectric element comprising electrodes provided on an upper surface and a lower surface of the ferroelectric thin film according to claim 5, respectively. A nozzle substrate having a nozzle hole for discharging liquid,
A flow path forming substrate having a pressurized liquid chamber communicating with the nozzle hole,
A diaphragm constituting at least one wall of the pressurized liquid chamber,
A liquid discharge head comprising: the piezoelectric element according to claim 6 on the vibration plate.   A liquid discharge unit comprising the liquid discharge head according to claim 7.   A liquid discharge apparatus comprising the liquid discharge head according to claim 7 or the liquid discharge unit according to claim 8.   A piezoelectric device comprising the piezoelectric element according to claim 6.