JP2013105971A - Liquid injection head, liquid injection apparatus, and piezoelectric element - Google Patents

Abstract

The performance of a piezoelectric element, a liquid ejecting head, and a liquid ejecting apparatus including a piezoelectric layer including at least Bi, Ba, Fe, and Ti is improved.
A piezoelectric layer is formed on a first electrode, and is formed on the first layer and a first layer having a perovskite oxide containing at least lead, zirconium, and titanium. And a second layer 32 having a perovskite oxide containing at least bismuth, barium, iron and titanium.

Description

  The present invention relates to a piezoelectric element and a liquid jet head including the piezoelectric element.

  Piezoelectric elements having the characteristics of being charged when a crystal is distorted or distorted when placed in an electric field are widely used in liquid ejecting apparatuses such as ink jet printers, actuators, sensors, and the like. As a typical piezoelectric material of this piezoelectric element, PZT (lead zirconate titanate) is used (for example, refer to Patent Documents 1 and 2).

  In recent years, there has been a demand for a piezoelectric element in which the amount of lead used is reduced from the viewpoint of environmental load (see, for example, Patent Document 3). Therefore, research on lead-free piezoelectric elements containing bismuth (Bi) or barium (Ba) instead of lead has been underway. For example, the BiFeO3-BaTiO3 (hereinafter also referred to as BF-BT) material disclosed in Patent Document 1 has good characteristics as a lead-free thin film piezoelectric material.

JP-A-11-126930 Japanese Patent Laid-Open No. 11-129478 JP 2005-244133 A

  However, the BiFeO3-BaTiO3 piezoelectric material has a higher Young's modulus than PZT, and it has been found that cracks may occur in the piezoelectric layer. In addition, since the stress applied to the interface between the piezoelectric layer and the first electrode is proportional to the film thickness, if the thickness of the piezoelectric layer exceeds a predetermined length, the occurrence of cracks becomes significant and the film thickness grows. It was difficult. Such a problem exists not only in the liquid ejecting head but also in a piezoelectric element such as a piezoelectric actuator or a sensor.

  In view of the above, one object of the present invention is to improve the performance of a piezoelectric element, a liquid ejecting head, and a liquid ejecting apparatus that include a piezoelectric layer including at least Bi, Ba, Fe, and Ti.

  In order to achieve one of the above objects, according to the present invention, there is provided a liquid ejecting head including a pressure generating chamber communicating with a nozzle opening, a piezoelectric element having a piezoelectric layer, a first electrode, and a second electrode. The piezoelectric layer is formed on the first electrode, has a first layer having a perovskite oxide containing at least lead, zirconium, and titanium, and is formed on the first layer, and has at least bismuth, And a second layer having a perovskite oxide containing barium, iron, and titanium.

  Furthermore, in the present invention, a piezoelectric element having a piezoelectric layer, a first electrode, and a second electrode, wherein the piezoelectric layer is formed on the first electrode and includes a perovskite containing at least lead, zirconium, and titanium. A first layer having a type oxide, and a second layer formed on the first layer and having a perovskite type oxide containing at least bismuth, barium, iron and titanium.

  That is, a first layer containing at least lead, zinc, and titanium is formed on the lower electrode that increases stress with respect to the piezoelectric element. Since the first layer is formed of a material having a Young's modulus lower than that of the piezoelectric layer, occurrence of cracks can be reduced. In addition, the first layer contains at least lead, zirconium, and titanium, so that a certain dielectric constant can be secured, and driving of the piezoelectric layer is not hindered.

FIG. 3 is a vertical cross-sectional view illustrating a main part of a piezoelectric element 3 included in a liquid ejecting head according to an embodiment of the invention. FIG. 2 is an exploded perspective view showing an ink jet recording head 1 which is an example of a liquid ejecting head in an exploded manner. (A)-(c) is sectional drawing for demonstrating the manufacturing process of the recording head 1. FIG. (A)-(c) is sectional drawing for demonstrating the manufacturing process of the recording head 1. FIG. 2 shows an appearance of a recording apparatus (liquid ejecting apparatus) 200 having the recording head 1 described above. 3 is an SEM diagram showing the surface of a piezoelectric layer of Example 1. FIG. 6 is an SEM diagram showing the surface of a piezoelectric layer of Comparative Example 1. FIG. 6 is a graph showing values of leakage currents of Example 1 and Comparative Example 1.

  Embodiments of the present invention will be described below. Of course, the embodiments described below are merely illustrative of the present invention.

(1) Schematic Configuration of Piezoelectric Element and Liquid Ejecting Head FIG. 1 is a vertical cross-sectional view showing the main part of the piezoelectric element 3 included in the liquid ejecting head according to the embodiment of the invention. FIG. 2 is an exploded perspective view showing the ink jet recording head 1 which is an example of the liquid ejecting head in an exploded manner. 3A to 3C are cross-sectional views for explaining the manufacturing process of the recording head 1. 4A to 4C are cross-sectional views for explaining the manufacturing process of the recording head 1.

  The recording head (liquid ejecting head) 1 illustrated in FIG. 2 includes a piezoelectric element 3 having a piezoelectric layer 30 and electrodes (20, 40), and pressure generation that causes a pressure change by the piezoelectric element 3 communicating with the nozzle opening 71. And a chamber 12. More specifically, the piezoelectric element 3 is configured by laminating the lower electrode 20, the piezoelectric layer 30, and the upper electrode 40 in this order on the diaphragm 16 having an elastic film. The pressure generation chamber 12 is formed on a silicon substrate 15 that constitutes a part of the flow path forming substrate 10. The flow path forming substrate 10 is fixed to the side of the diaphragm 16 where the piezoelectric element 3 is not laminated. A nozzle plate 70 is fixed to the side of the flow path forming substrate 10 that is not fixed to the diaphragm 16. The nozzle plate 70 has a plurality of nozzle openings 71 that are part of a flow path for ejecting ink. Further, a protective substrate 50 to which a compliance substrate 60 is fixed is fixed to the side of the diaphragm 16 to which the piezoelectric element 3 is fixed.

First, the configuration of the piezoelectric element 3 will be described with reference to FIG.
The piezoelectric element 3 is formed by stacking layers so that the piezoelectric layer 30 is sandwiched between a lower electrode (first electrode) 20 and an upper electrode (second electrode) 40. The piezoelectric layer 30 includes a first layer 31 containing lead immediately above the lower electrode 20 and a second layer 32 containing bismuth (Bi) and barium (Ba) on the first layer 31. Are stacked to suppress the occurrence of cracks in the piezoelectric layer 30.
That is, in the piezoelectric element 3, the stress becomes maximum near the interface with the diaphragm 16. On the other hand, the composite oxide containing Bi is characterized by (i) strong brittleness and poor ductility, and (ii) a high Young's modulus (for example, 150 Gpa). Therefore, due to the features (i) and (ii) above, cracks are likely to occur in the vicinity of the interface with the lower electrode 20 where the generation of stress is significant in the piezoelectric layer 30. Therefore, in the piezoelectric layer 30, the generation of cracks is suppressed by providing the first layer 31 having a small Young's modulus immediately above the lower electrode 20.

  As shown in FIG. 1, a lower electrode 20 having a layer containing at least one of platinum (Pt) and titanium (Ti) is laminated immediately above the diaphragm 16.

A first layer 31 containing at least lead (Pb), zirconium (Zr), and titanium (Ti) is laminated immediately above the lower electrode 20. The first layer 31 is made of a perovskite oxide, and is made of lead zirconate titanate containing Pb as the A site element and Zr and Ti as the B site element. Such a perovskite oxide includes a perovskite oxide having a composition represented by the following general formula.
Pb (Zr, Ti) Ox (1)
(Pb, MA) (Zr, Ti) Ox (2)
Pb (Zr, Ti, MB) Ox (3)
(Pb, MA) (Zr, Ti, MB) Ox (4)
Here, MA is one or more metal elements excluding Pb, and MB is one or more metal elements excluding Zr, Ti, and Pb. x is 3 as a standard, but may deviate from 3 within a range where a perovskite structure can be taken. The ratio of the A site element to the B site element is 1: 1 as a standard, but may be deviated from 1: 1 within a range where a perovskite structure can be taken.
The MB element includes niobium (Nb), tantalum (Ta), and the like.

Further, a second layer 32 is laminated immediately above the first layer 31. This second layer 32 is a lead-free perovskite type containing at least bismuth (Bi) and barium (Ba) as the A site element and at least iron (Fe) and titanium (Ti) as the B site element. It is an oxide. Such a perovskite oxide includes a lead-free perovskite oxide having a composition represented by the following general formula.
(Bi, Ba) (Fe, Ti) Ox (5)
(Bi, Ba, MC) (Fe, Ti) Ox (6)
(Bi, Ba) (Fe, Ti, MD) Ox (7)
(Bi, Ba, MC) (Fe, Ti, MD) Ox (8)
Here, MC is one or more metal elements excluding Bi and Ba, and MD is one or more metal elements excluding Fe, Ti, Bi, and Ba. x is 3 as a standard, but may deviate from 3 within a range where a perovskite structure can be taken. The ratio of the A site element to the B site element is 1: 1 as a standard, but may be deviated from 1: 1 within a range where a perovskite structure can be taken.

The molar ratio of Bi to the total molar number of Bi, Ba, and MA can be, for example, about 65 to 95%. Moreover, the mole number ratio of Ba with respect to the total mole number of Bi, Ba, and MA can be about 5 to 35%, for example. And the mole number ratio of MA with respect to the mole number total of Bi, Ba, and MA can be about 0.1 to 30%, for example.
Furthermore, the molar ratio of Fe to the total molar number of Fe, Ti, and MD can be, for example, about 52 to 95%. Furthermore, the mole number ratio of Ti with respect to the total mole number of Fe, Ti, and MD can be, for example, about 5 to 35%. And the mole number ratio of MD with respect to the mole number total of Fe, Ti, MD can be made into about 0.1 to 19%, for example.
The MD element includes Mn and the like. The molar ratio of Mn in the B site constituent metal can be, for example, about 0.1 to 10%, with the total molar ratio of the B site constituent metal being 100%. When Mn is added, an effect of increasing the insulating property of the piezoelectric layer (improving leakage characteristics) is expected, but a piezoelectric element having piezoelectric performance can be formed without Mn.

An upper electrode 40 is stacked on the second layer 32. As the metal constituting the upper electrode 40, iridium (Ir), gold (Au), platinum (Pt), or the like can be used. Of course, in addition to this, a different metal may be contained in the above-described metal.
In addition, the upper electrode 40 may be stacked directly on the second layer 32. In addition to this, another layer may be stacked between the second layer 32 and the upper electrode 40. Good.

  Here, the ratio of the thicknesses of the first layer 31 and the second layer 32 is obtained when the thickness of the piezoelectric layer 30 (the sum of the first layer 31 and the second layer 32) is 100%. The thickness ratio of the first layer 31 is desirably 30% or less. More preferably, the thickness ratio of the first layer 31 is about 10%. This is because if the thickness ratio of the first layer 31 is 30% or less, the object of the present invention can be achieved while reducing the Pb content in the piezoelectric element.

(2) Manufacturing Method of Piezoelectric Element and Liquid Ejecting Head A manufacturing method of the above-described piezoelectric element 3 and a recording head (liquid ejecting head) 1 including the piezoelectric element 3 will be described with reference to FIGS.

  As a method for manufacturing the recording head 1, first, the flow path forming substrate 10 is formed from a silicon single crystal substrate or the like. Then, for example, one surface of the relatively thick and rigid silicon substrate 15 having a film thickness of about 625 μm is thermally oxidized by a diffusion path of about 1100 ° C. to thereby form an elastic film made of silicon dioxide (SiO 2) (the diaphragm 16 ) Are integrally formed. The thickness of the elastic film is not limited as long as it has elasticity, but can be, for example, about 0.5 to 2 μm.

  Next, as shown in FIG. 3A, the lower electrode 20 is formed on the elastic film 16 by sputtering or the like. In the example shown in FIG. 3B, patterning is performed after the lower electrode 20 is formed. As a constituent metal of the lower electrode 20, one or more kinds of metals such as Pt, Au, Ir, Ti, and the like can be used. Although the thickness of a lower electrode is not specifically limited, For example, it can be set as about 50-500 nm. A layer such as a TiAlN (titanium aluminum nitride) film, an Ir film, an IrO (iridium oxide) film, or a ZrO2 (zirconium oxide) film is formed on the elastic film 16 as the adhesion layer or the diffusion prevention layer, and then the lower electrode 20 may be formed.

  Next, a precursor solution containing at least a lead salt, a zirconium salt, and a titanium salt is applied to the surface of the lower electrode 20. The metal molar concentration ratio in the precursor solution can be determined according to the composition of the perovskite oxide to be formed. The molar ratio of the A site element and the B site element in the above formulas (1) to (4) is 1: 1 as a standard, but may be deviated from 1: 1 within the range in which the perovskite oxide is formed.

Then, as shown in FIG. 3A, the applied precursor solution 81 is crystallized to form the first layer 31. As an example, preferably, the precursor solution 81 is heated and dried at about 140 to 190 ° C., and then degreased by heating at about 300 to 400 ° C., for example, at about 550 to 850 ° C. Heat to crystallize.
The thickness of the formed first layer 31 can be about 100 nm, for example. Of course, the thickness of the first layer 31 is not limited to this, but it is desirable that the ratio of the thickness to the thickness of the piezoelectric layer 30 is set to 30% or less.

  Next, a precursor solution containing at least a bismuth salt, a barium salt, an iron salt, and a titanium compound is applied to the upper portion of the first layer 31. The metal molar concentration ratio in the precursor solution can be determined according to the composition of the perovskite oxide to be formed. In the above formulas (5) to (8), the molar ratio of the A site element and the B site element is 1: 1 as a standard, but may be deviated from 1: 1 within the range in which the perovskite oxide is formed.

Then, as shown in FIG. 3B, the applied precursor solution 31 is crystallized to form a second layer 32 containing a perovskite oxide. The crystallization process is the same as that of the first layer 31 described above. That is, preferably, the precursor solution 31 is heated and dried at about 140 to 190 ° C., and then degreased by heating at about 300 to 400 ° C., for example, heated at about 550 to 850 ° C. Then, it is fired and crystallized.
In addition, in order to thicken the 2nd layer 32, you may perform the combination of an application | coating process, a drying process, a degreasing process, and a baking process in multiple times. In order to reduce the firing process, the firing process may be performed after the combination of the coating process, the drying process, and the degreasing process is performed a plurality of times. Further, a combination of these steps may be performed a plurality of times.

  In addition, as a heating apparatus for performing the above-described drying and degreasing, a hot plate, an infrared lamp annealing apparatus that heats by irradiation with an infrared lamp, or the like can be used. An infrared lamp annealing device or the like can be used as the heating device for performing the firing. Preferably, the temperature rising rate may be made relatively fast by using an RTA (Rapid Thermal Annealing) method or the like.

On the piezoelectric layer 30 thus formed, as shown in FIG. 3B, the upper electrode 40 is formed by sputtering or the like. As the metal constituting the upper electrode, one or more kinds of metals such as Ir, Au, and Pt can be used. Moreover, the thickness of the upper electrode is not particularly limited, but can be, for example, about 50 to 200 nm. In the example shown in FIG. 3C, after the upper electrode 40 is formed, the piezoelectric layer 30 and the upper electrode 40 are patterned in regions facing the pressure generation chambers 12 to form the piezoelectric element 3. Yes.
In general, any one electrode of the piezoelectric element 3 is used as a common electrode, and the other electrode and the piezoelectric layer 30 are patterned for each pressure generating chamber 12 to constitute the piezoelectric element 3. 2 and 4, the lower electrode 20 is a common electrode and the upper electrode 40 is an individual electrode, but the upper electrode 40 is a common electrode and the lower electrode is an individual electrode. Also good.

  Thus, the piezoelectric element 3 having the piezoelectric layer 30 and the electrodes (20, 40) is formed, and the piezoelectric actuator 2 including the piezoelectric element 3 and the diaphragm 16 is formed.

  Subsequently, as shown in FIG. 3C, a lead electrode 45 is formed. For example, the lead electrode 45 is provided by forming a gold layer over the front surface of the flow path forming substrate 10 and then patterning each piezoelectric element 3 through a mask pattern made of a resist or the like. A lead electrode 45 extending from the vicinity of the end on the ink supply path 14 side to the diaphragm 16 is connected to each upper electrode 40 shown in FIG.

  The lower electrode 20, the upper electrode 40, and the lead electrode 45 can be formed by a sputtering method such as a DC (direct current) magnetron sputtering method. The thickness of each layer can be adjusted by changing the voltage applied to the sputtering apparatus and the sputtering processing time.

  Next, as shown in FIG. 4A, the protective substrate 50 on which the piezoelectric element holding portion 52 and the like are formed in advance is bonded onto the flow path forming substrate 10 with an adhesive, for example. As the protective substrate 50, for example, a silicon single crystal substrate, glass, a ceramic material, or the like can be used. Although the thickness of the protective substrate 50 is not specifically limited, For example, it can be set as about 400 micrometers. The reservoir portion 51 penetrating in the thickness direction of the protective substrate 50 constitutes the reservoir 9 serving as a common ink chamber together with the communication portion 13. The piezoelectric element holding portion 52 provided in the region facing the piezoelectric element 3 has a space that does not hinder the movement of the piezoelectric element 3. In the through hole 53 of the protective substrate 50, the vicinity of the end portion of the lead electrode 45 drawn from each piezoelectric element 3 is exposed.

Next, after polishing the silicon substrate 15 to a certain thickness, the silicon substrate 15 is further etched to a predetermined thickness (for example, about 70 μm) by wet etching with hydrofluoric acid. Next, as shown in FIG. 4B, a mask film 17 is newly formed on the silicon substrate 15 and patterned into a predetermined shape. Silicon nitride (SiN) or the like can be used for the mask film 17. Next, the silicon substrate 15 is anisotropically etched (wet etching) using an alkaline solution such as KOH. As a result, a plurality of liquid flow paths including the pressure generating chambers 12 defined by the plurality of partition walls 11 and the narrow ink supply paths 14, and a communication portion 13 that is a common liquid flow path connected to each ink supply path 14. And are formed. The liquid flow paths (12, 14) are arranged in the width direction D1, which is the short direction of the pressure generating chamber 12.
The pressure generation chamber 12 may be formed before the piezoelectric element 3 is formed.

  Next, unnecessary portions at the peripheral portions of the flow path forming substrate 10 and the protective substrate 50 are removed by cutting, for example, by dicing. Next, as shown in FIG. 4C, the nozzle plate 70 is bonded to the surface of the silicon substrate 15 opposite to the protective substrate 50. The nozzle plate 70 can be made of glass ceramics, silicon single crystal substrate, stainless steel, or the like, and is fixed to the opening surface side of the flow path forming substrate 10. For this fixation, an adhesive, a heat welding film, or the like can be used. The nozzle plate 70 is formed with nozzle openings 71 communicating with the vicinity of the end of each pressure generating chamber 12 on the side opposite to the ink supply path 14. Therefore, the pressure generation chamber 12 communicates with the nozzle opening 71 that discharges the liquid.

  Next, the compliance substrate 60 having the sealing film 61 and the fixing plate 62 is bonded onto the protective substrate 50 and divided into a predetermined chip size. The sealing film 61 is made of, for example, a material having low rigidity such as a polyphenylene sulfide (PPS) film having a thickness of about 6 μm, and seals one surface of the reservoir unit 51. The fixed plate 62 is made of a hard material such as a metal such as stainless steel (SUS) having a thickness of about 30 μm, for example, and an area facing the reservoir 9 is an opening 63.

A driving circuit 65 for driving the piezoelectric elements 3 arranged in parallel is fixed on the protective substrate 50. For the drive circuit 65, a circuit board, a semiconductor integrated circuit (IC), or the like can be used. The drive circuit 65 and the lead electrode 45 are electrically connected via the connection wiring 66. As the connection wiring 66, a conductive wire such as a bonding wire can be used.
Thus, the recording head 1 is manufactured.

  The recording head 1 takes in ink from an ink introduction port connected to an external ink supply unit (not shown), and fills the interior from the reservoir 9 to the nozzle opening 71 with ink. When a voltage is applied between the lower electrode 20 and the upper electrode 40 for each pressure generating chamber 12 in accordance with a recording signal from the drive circuit 65, the deformation of the piezoelectric layer 30, the lower electrode 20 and the diaphragm 16 causes deformation from the nozzle opening 71. Ink droplets are ejected.

(3) Liquid ejecting apparatus:
FIG. 5 shows the appearance of a recording apparatus (liquid ejecting apparatus) 200 having the recording head 1 described above. When the recording head 1 is incorporated in the recording head units 211 and 212, the recording apparatus 200 can be manufactured. In the recording apparatus 200 shown in FIG. 5, the recording head 1 is provided in each of the recording head units 211 and 212, and ink cartridges 221 and 222 as external ink supply units are detachably provided. A carriage 203 on which the recording head units 211 and 212 are mounted is provided so as to be able to reciprocate along a carriage shaft 205 attached to the apparatus main body 204. When the driving force of the driving motor 206 is transmitted to the carriage 203 via a plurality of gears and a timing belt 207 (not shown), the carriage 203 moves along the carriage shaft 205. A recording sheet 290 fed by a sheet feeding roller (not shown) is conveyed onto the platen 208 and printed by ink supplied from the ink cartridges 221 and 222 and ejected from the recording head 1.

(4) Example:
Hereinafter, although an example is shown, the present invention is not limited by the following examples.

[Fabrication of substrate with lower electrode laminated]
A substrate having each layer of Pt / TiOx (titanium oxide) / SiO2 / Si was prepared as follows.
First, the Si substrate was thermally oxidized at 1100 ° C. in a diffusion furnace to form a 1.3 μm thick SiO 2 film on the Si substrate surface. Next, a Ti film having a thickness of 20 nm was formed on the SiO2 film surface by DC sputtering, and heat treatment was performed in oxygen at 700 [deg.] C. for 5 minutes with a lamp heat treatment apparatus (RTA method) to form a TiOx film. Further, a 130 nm thick Pt film was formed on the surface of the TiOx film by DC sputtering at 330 ° C. and 300 W.

[Example 1]
(PZT precursor solution preparation)
Pb, Zr, Ti As precursor materials for each metal element, lead acetate trihydrate (Pb (CH3COOH) 2 · 3H2O), zirconium tetra-n-butoxide (Zr {CH3 (CH2) 3O} 4), titanium isopropoxy (Ti {(CH3) 2CHO} 4) was used.
2-n-butoxyethanol was used as a solvent, and the precursor material was used so as to be 0.3 to 0.6 (mol / l) with respect to the solvent.

(PZT film production)
A PZT precursor solution was spin-coated on a Pt / TiOx / SiO2 / Si substrate at 3000 rpm (coating process), dried by heating for 3 minutes (drying process), and further degreased by heating for 3 minutes (degreasing process). . And it heat-processed for 5 minutes at 750 degreeC with the lamp | ramp heat processing apparatus (RTA method). These steps were repeated twice and crystallized to form a PZT film on the Pt / TiOx / SiO2 / Si substrate (first layer).

(Preparation of BFM-BT precursor solution)
Bi, Fe, Mn, Ba As precursor materials for each metal element, bismuth-n-butoxide (Bi {(CH3) 2CHO} 4), iron acetyl acetate (Fe {CH3COCHCOCH3} 3), manganese acetylacetonate (Mn {CH3COCHCOCH3) } 2), barium acetate (Ba (CH3COO) 2), and titanium isopropoxide (Ti {(CH3) 2CHO} 4) were used.
Isoamyl acetate was used as the solvent, and the precursor material was used in an amount of 0.3 to 0.6 (mol / l) based on the solvent.

(BFM-BT film production)
Each precursor solution was spin-coated on the first layer 80 at 3000 rpm (application process), dried by heating (drying process), and further degreased by heating (degreasing process). And it heat-processed for 5 minutes at 750 degreeC with the lamp | ramp heat processing apparatus (RTA method). These steps were repeated 10 times and crystallized to form a BFM-BT film on the PZT film (second layer).

In contrast to Example 1, Comparative Example 1 having no PZT film was prepared. This Comparative Example 1 was prepared under the same conditions and method as in Example 1 except that it did not have a PZT film.
And the upper electrode was formed on this PZT film | membrane, and the piezoelectric element was created.

Table 1 shows the film thicknesses of the PZT film and the BFM-BT film of Example 1 and Comparative Example 1. In the case where the PZT film was not provided, 0 nm was described.

6 is an SEM (Scanning Electron Microscope) diagram showing the surface of the piezoelectric layer of Example 1. FIG. FIG. 7 is an SEM diagram showing the surface of the piezoelectric layer of Comparative Example 1.
As a result of observing the surface of the piezoelectric layer of Example 1 and the surface of the piezoelectric layer of Comparative Example 1 using a scanning electron microscope, generation of cracks was observed in Comparative Example 1. On the other hand, in Example 1, generation | occurrence | production of the crack was not observed. From the above, it was found that cracks can be suppressed in the BFM-BT layer that forms the PZT layer immediately above the lower electrode.
Moreover, it has been found that by adopting the above configuration, the occurrence of cracks can be suppressed even when the piezoelectric layer is formed with a thickness of 1000 nm or more.

(Other evaluation)
FIG. 8 is a graph showing the values of leakage current between Example 1 and Comparative Example 1. In FIG. 8, the applied voltage is shown on the horizontal axis, and the leakage current (A / m 2) shown in current density per unit area is shown on the vertical axis.
As shown in FIG. 8, in the region where the applied voltage was 3 V or less, the difference in current density between the BFM-BT films of Example 1 and Comparative Example 1 did not change. On the other hand, in the region where the applied voltage is 3 V or higher, the BFM-BT film of Example 1 has a lower leakage current than the BFM-BT film of Comparative Example 1.

In general, in a low voltage range (region where the applied voltage is less than 3 V in FIG. 8), the value of the leakage current changes according to Ohm's law with respect to the applied voltage, and the influence of the composition of the piezoelectric element on the insulation is small. Is understood. On the other hand, in the high voltage range (region where the applied voltage is 3 V or more in FIG. 8), the change in leakage current does not follow Ohm's law and is greatly affected by the operating environment or the composition of the piezoelectric element.
For this reason, since the leakage current in the high voltage region in Example 1 is smaller than that in Comparative Example 1, by providing the first layer between the lower electrode and the second layer, in this high voltage region It is thought that this contributes to a decrease in the leakage current. This is presumed to be due to the function of blocking the movement of defects, ions, etc. generated in the second layer in the first layer.

(5) Application and others:
Various modifications can be considered for the present invention.
In the above-described embodiment, an individual piezoelectric body is provided for each pressure generation chamber. However, a common piezoelectric body may be provided for a plurality of pressure generation chambers, and an individual electrode may be provided for each pressure generation chamber.
In the above-described embodiment, a part of the reservoir is formed on the flow path forming substrate. However, the reservoir may be formed on a member different from the flow path forming substrate.
In the above-described embodiment, the upper side of the piezoelectric element is covered with the piezoelectric element holding unit, but the upper side of the piezoelectric element can be opened to the atmosphere.
In the embodiment described above, the pressure generating chamber is provided on the opposite side of the piezoelectric element with the diaphragm interposed therebetween, but it is also possible to provide the pressure generating chamber on the piezoelectric element side. For example, if a space surrounded by fixed plates and piezoelectric elements is formed, this space can be used as a pressure generating chamber.

  The liquid ejected from the fluid ejecting head may be any material that can be ejected from the liquid ejecting head, such as a solution in which a dye or the like is dissolved in a solvent, or a sol in which solid particles such as pigments or metal particles are dispersed in a dispersion medium. Is included. Such fluids include ink, liquid crystal, and the like. The liquid ejecting head includes one that discharges powder or gas. The liquid ejecting head can be mounted on an image recording apparatus such as a printer, a color filter manufacturing apparatus such as a liquid crystal display, an electrode manufacturing apparatus such as an organic EL display, a biochip manufacturing apparatus, and the like.

As described above, according to the present invention, according to various embodiments, a piezoelectric element having a piezoelectric layer containing at least Bi, Ba, Fe, and Ti, a technique for improving the performance of the liquid ejecting head, and the liquid ejecting apparatus are provided. can do.
In addition, the configurations disclosed in the embodiments and modifications described above are mutually replaced, the combinations are changed, the known technology, and the configurations disclosed in the embodiments and modifications described above are mutually connected. It is possible to implement a configuration in which replacement or combination is changed. The present invention includes these configurations and the like.

  DESCRIPTION OF SYMBOLS 1 ... Recording head, 2 ... Piezoelectric actuator, 3 ... Piezoelectric element, 10 ... Channel formation substrate, 12 ... Pressure generating chamber, 15 ... Silicon substrate, 16 ... Vibration plate, 20 ... Lower electrode, 30 ... Piezoelectric layer, 40 ... Upper electrode, 50 ... Protective substrate, 60 ... Compliance substrate, 70 ... Nozzle plate, 71 ... Nozzle opening, 200 ... Recording apparatus

Claims (5)

A pressure generating chamber communicating with the nozzle opening;
A piezoelectric element having a piezoelectric layer, a first electrode and a second electrode, and a liquid jet head comprising:
The piezoelectric layer is
A first layer formed on the first electrode and having a perovskite oxide containing at least lead, zirconium, and titanium;
And a second layer having a perovskite oxide that includes at least bismuth, barium, iron, and titanium, and is formed on the first layer.   2. The liquid jet head according to claim 1, wherein a ratio of a thickness of the first layer to a sum of thicknesses of the first layer and the second layer is 30% or less.   The liquid ejecting head according to claim 1, wherein manganese is contained in the perovskite oxide of the second layer.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1. A piezoelectric element having a piezoelectric layer, a first electrode and a second electrode,
The piezoelectric layer is
A first layer formed on the first electrode and having a perovskite oxide containing at least lead, zirconium, and titanium;
And a second layer having a perovskite-type oxide containing at least bismuth, barium, iron and titanium formed on the first layer.