JP2013091228A - Liquid jet head, liquid jetting apparatus, and piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid jet head having a reduced environmental load and a large strain amount.SOLUTION: There is provided a liquid jet head for ejecting a liquid from a nozzle opening, which has a piezoelectric element equipped with a piezoelectric layer and an electrode installed to the piezoelectric element. The piezoelectric layer consists of a composite oxide containing bismuth, iron, barium, titanium and having a perovskite structure. A Pr2/Pr1 ratio is 0.39-0.70, wherein Pr1 is a remnant polarization value at an application end time when 30V 1 kHz triangle wave for one period is applied, and Pr2 is the remnant polarization value at a time point of 1.0 sec. after the application end time.

Description

  The present invention relates to a liquid ejecting head, a liquid ejecting apparatus, and a piezoelectric element that include a piezoelectric element having a piezoelectric layer made of a piezoelectric material and an electrode and eject liquid droplets from nozzle openings.

  As a typical example of a liquid ejecting head, for example, a part of a pressure generation chamber communicating with a nozzle for ejecting ink droplets is configured by a vibration plate, and the vibration plate is deformed by a piezoelectric element to add ink in the pressure generation chamber. There is an ink jet recording head that presses and ejects ink droplets from a nozzle. A piezoelectric element used in an ink jet recording head is configured by sandwiching a piezoelectric material (electromagnetic film) made of a piezoelectric material exhibiting an electromechanical conversion function, for example, a crystallized dielectric material, between two electrodes. There is something.

A piezoelectric material used as a piezoelectric layer constituting such a piezoelectric element is required to have high piezoelectric characteristics, and a typical example of the piezoelectric material is lead zirconate titanate (PZT) (see Patent Document 1). ). However, from the viewpoint of environmental problems, there is a demand for a piezoelectric material with reduced lead or lead content. As a piezoelectric material not containing lead, for example, there is a BiFeO ₃ -based piezoelectric material containing Bi and Fe (see, for example, Patent Document 2).

JP 2001-223404 A JP 2007-287745 A

  However, the piezoelectric layer made of a composite oxide with a reduced content of non-lead or lead does not have a sufficient amount of strain compared to lead zirconate titanate (PZT). It has been. Such a problem exists not only in the ink jet recording head, but of course in other liquid ejecting heads that eject droplets other than ink, and also in piezoelectric elements used in other than liquid ejecting heads. Exist as well.

  In view of such circumstances, it is an object of the present invention to provide a liquid ejecting head, a liquid ejecting apparatus, and a piezoelectric element that have a small environmental load and a large amount of distortion.

An aspect of the present invention that solves the above problem is a liquid ejecting head that discharges liquid from a nozzle opening, and includes a piezoelectric element that includes a piezoelectric layer and an electrode provided on the piezoelectric layer, and the piezoelectric body The layer is made of a complex oxide having a perovskite structure containing bismuth, iron, barium and titanium, and a residual polarization amount Pr1 at the end of application when a 30 V 1 kHz triangular wave is applied, and 1 from the end of the application. In the liquid jet head, Pr2 / Pr1, which is a ratio to the residual polarization amount Pr2 when 0.0 second has elapsed, is 0.39 or more and 0.70 or less.
In this aspect, by setting the ratio of the residual polarization amount Pr1 when a predetermined voltage is applied to the piezoelectric layer and the residual polarization amount Pr2 when a predetermined time has passed thereafter to a predetermined range, the strain amount, that is, The amount of displacement is significantly improved. Furthermore, since the content of non-lead or lead can be suppressed, the burden on the environment can be reduced.

  According to another aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting head. In this aspect, since the piezoelectric element having a reduced environmental load and an improved displacement amount is provided, a liquid ejecting apparatus having excellent piezoelectric characteristics (displacement amount) can be realized.

Another aspect of the present invention is a piezoelectric element comprising a piezoelectric layer and an electrode provided on the piezoelectric layer, wherein the piezoelectric layer includes bismuth, iron, barium and titanium and has a perovskite structure. This is the ratio between the residual polarization amount Pr1 at the end of application when a period of 30 V 1 kHz triangular wave is applied, and the residual polarization amount Pr2 when 1.0 second has elapsed from the end of application. In the piezoelectric element, Pr2 / Pr1 is 0.39 or more and 0.70 or less.
In this aspect, by setting the ratio of the residual polarization amount Pr1 when a predetermined voltage is applied to the piezoelectric layer and the residual polarization amount Pr2 when a predetermined time has passed thereafter to a predetermined range, the strain amount, that is, The piezoelectric element has a significantly improved displacement. Furthermore, since the content of non-lead or lead can be suppressed, the burden on the environment can be reduced.

FIG. 3 is an exploded perspective view illustrating a schematic configuration of the recording head according to the first embodiment. FIG. 3 is a plan view of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view of the recording head according to the first embodiment. The figure which shows the PV curve example of a piezoelectric material layer, and the figure which shows the triangular wave applied to a piezoelectric material layer. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the recording head according to the first embodiment. The figure which shows the relationship between Pr2 / Pr1 and a displacement amount of an Example and a comparative example. 1 is a diagram illustrating a schematic configuration of a recording apparatus according to an embodiment of the present invention.

(Embodiment 1)
FIG. 1 is an exploded perspective view showing a schematic configuration of an ink jet recording head which is an example of a liquid ejecting head according to Embodiment 1 of the invention, FIG. 2 is a plan view of FIG. 1, and FIG. 2 is a cross-sectional view taken along line AA ′ of FIG. As shown in FIGS. 1 to 3, the flow path forming substrate 10 of the present embodiment is made of a silicon single crystal substrate, and an elastic film 50 made of silicon dioxide is formed on one surface thereof.

  A plurality of pressure generating chambers 12 are arranged in parallel in the width direction of the flow path forming substrate 10. In addition, a communication portion 13 is formed in a region outside the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10, and the communication portion 13 and each pressure generation chamber 12 are provided for each pressure generation chamber 12. Communication is made via a supply path 14 and a communication path 15. The communication part 13 communicates with a manifold part 31 of a protective substrate, which will be described later, and constitutes a part of a manifold that becomes a common ink chamber for each pressure generating chamber 12. The ink supply path 14 is formed with a narrower width than the pressure generation chamber 12, and maintains a constant flow path resistance of ink flowing into the pressure generation chamber 12 from the communication portion 13. In this embodiment, the ink supply path 14 is formed by narrowing the width of the flow path from one side. However, the ink supply path may be formed by narrowing the width of the flow path from both sides. Further, the ink supply path may be formed by narrowing from the thickness direction instead of narrowing the width of the flow path. In the present embodiment, the flow path forming substrate 10 is provided with a liquid flow path including the pressure generation chamber 12, the communication portion 13, the ink supply path 14, and the communication path 15.

  Further, on the opening surface side of the flow path forming substrate 10, a nozzle plate 20 having a nozzle opening 21 communicating with the vicinity of the end of each pressure generating chamber 12 on the side opposite to the ink supply path 14 is provided with an adhesive. Or a heat-welded film or the like. The nozzle plate 20 is made of, for example, glass ceramics, a silicon single crystal substrate, stainless steel, or the like.

  On the other hand, the elastic film 50 is formed on the side opposite to the opening surface of the flow path forming substrate 10 as described above. On the elastic film 50, for example, titanium oxide having a thickness of about 30 to 50 nm or the like. An adhesion layer 56 for improving adhesion between the first electrode 60 such as the elastic film 50 and the like is provided. Note that an insulator film made of zirconium oxide or the like may be provided on the elastic film 50 as necessary.

  Further, on the adhesion layer 56, a first electrode 60, a piezoelectric layer 70 which is a thin film having a thickness of 3 μm or less, preferably 0.3 to 1.5 μm, and a second electrode 80 are laminated. Thus, a piezoelectric element 300 is configured as pressure generating means for causing a pressure change in the pressure generating chamber 12. Here, the piezoelectric element 300 refers to a portion including the first electrode 60, the piezoelectric layer 70, and the second electrode 80. In general, one electrode of the piezoelectric element 300 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure generating chamber 12. In the present embodiment, the first electrode 60 is a common electrode of the piezoelectric element 300, and the second electrode 80 is an individual electrode of the piezoelectric element 300. However, there is no problem even if this is reversed for the convenience of the drive circuit and wiring. Also, here, the piezoelectric element 300 and the diaphragm that is displaced by driving the piezoelectric element 300 are collectively referred to as an actuator device. In the above-described example, the elastic film 50, the adhesion layer 56, the first electrode 60, and the insulator film provided as necessary function as a vibration plate. However, the present invention is not limited to this. 50 and the adhesion layer 56 may not be provided. Further, the piezoelectric element 300 itself may substantially serve as a diaphragm.

In this embodiment, the piezoelectric material constituting the piezoelectric layer 70 is a complex oxide having a perovskite structure including bismuth (Bi), iron (Fe), barium (Ba), and titanium (Ti). In the A site of the perovskite structure, that is, the ABO ₃ type structure, oxygen is 12-coordinated, and in the B site, oxygen is 6-coordinated to form an octahedron. Bi and Ba are located at the A site, and Fe and Ti are located at the B site.

  Such a composite oxide containing Bi, Fe, Ba and Ti and having a perovskite structure is a composite oxide having a perovskite structure of a mixed crystal of bismuth ferrate and barium titanate, or bismuth ferrate and barium titanate. Is also expressed as a solid solution in which the solid solution is uniformly dissolved. In the X-ray diffraction pattern, bismuth ferrate and barium titanate are not detected alone.

Here, bismuth ferrate and barium titanate are known piezoelectric materials each having a perovskite structure, and those having various compositions are known. For example, as bismuth ferrate or barium titanate, in addition to BiFeO ₃ or BaTiO ₃ , some elements (Bi, Fe, Ba, Ti, O) are partially lost or excessive, or some of the elements are other elements However, in the present invention, when expressed as bismuth ferrate or barium titanate, as long as the basic characteristics are not changed, those that deviate from the stoichiometric composition due to deficiency or excess Those in which some of the elements are substituted with other elements are also included in the ranges of bismuth ferrate and barium titanate. The ratio of bismuth ferrate to barium titanate can also be changed variously.

  The composition of the piezoelectric layer 70 made of a complex oxide having such a perovskite structure is represented, for example, as a mixed crystal represented by the following general formula (1). Further, the formula (1) can also be expressed by the following general formula (1 ′). Here, the description of the general formula (1) and the general formula (1 ′) is a composition notation based on the stoichiometry. Of course, a partial substitution of elements is allowed as well as a slight compositional deviation. For example, if the stoichiometric ratio is 1, the range of 0.85 to 1.20 is allowed. In addition, even when the general formulas are different as described below, those having the same ratio of the A-site element to the B-site element may be regarded as the same composite oxide.

(1-x) [BiFeO ₃ ] -x [BaTiO ₃ ] (1)
(0 <x <0.40)
(Bi _1-x Ba _x ) (Fe _1-x Ti _x ) O ₃ (1 ′)
(0 <x <0.40)

  Further, the complex oxide constituting the piezoelectric layer 70 may further contain an element other than Bi, Fe, Ba, and Ti. Examples of other elements include Mn, Co, and Cr. Of course, even a complex oxide containing other elements needs to have a perovskite structure.

  When the piezoelectric layer 70 includes Mn, Co, and Cr, Mn, Co, and Cr are complex oxides having a structure located at the B site. For example, when Mn is included, the composite oxide constituting the piezoelectric layer 70 has a structure in which part of Fe in a solid solution in which bismuth ferrate and barium titanate are uniformly dissolved, is substituted with Mn, or ferric acid It is expressed as a composite oxide having a perovskite structure of mixed crystals of bismuth manganate and barium titanate, and the basic characteristics are the same as those of a composite oxide having a perovskite structure of mixed crystals of bismuth ferrate and barium titanate. However, it has been found that the leakage characteristics are improved. Further, when Co or Cr is included, the leakage characteristics are improved in the same manner as Mn. In the X-ray diffraction pattern, bismuth ferrate, barium titanate, bismuth iron manganate, bismuth iron cobaltate, and bismuth iron chromate are not detected alone. Further, although Mn, Co and Cr have been described as examples, it has been found that leakage characteristics are similarly improved when two other transition metal elements are included at the same time. In addition, other known additives may be included to improve the properties.

  The piezoelectric layer 70 made of a composite oxide having a perovskite structure including Mn, Co, and Cr in addition to Bi, Fe, Ba, and Ti is, for example, a mixed crystal represented by the following general formula (2). is there. Further, the formula (2) can also be expressed by the following general formula (2 ′). In general formula (2) and general formula (2 '), M is Mn, Co, or Cr. Here, the description of the general formula (2) and the general formula (2 ′) is a composition notation based on the stoichiometry, and as described above, as long as the perovskite structure can be taken, it is unavoidable due to lattice mismatch, oxygen deficiency, etc. Such a composition deviation is allowed. For example, if the stoichiometry is 1, one in the range of 0.85 to 1.20 is allowed. In addition, even when the general formulas are different as described below, those having the same ratio of the A-site element to the B-site element may be regarded as the same composite oxide.

(1-x) [Bi (Fe _1-y M _y ) O ₃ ] -x [BaTiO ₃ ] (2)
(0 <x <0.40, 0.01 <y <0.10)
_{(Bi 1-x Ba x)} ((Fe 1-y M y) 1-x Ti x) O 3 (2 ')
(0 <x <0.40, 0.01 <y <0.10)

  Here, when a triangular wave voltage is applied to the piezoelectric material, the PV curve indicating the relationship between the polarization amount P and the voltage V becomes hysteresis. In the present invention, the piezoelectric layer 70, which is a piezoelectric material, has a residual polarization amount Pr1 at the end of application when applying one period of a 30V 1kHz triangular wave, and 1.0 second has elapsed from the end of the application. The ratio Pr2 / Pr1, which is a ratio with the residual polarization amount Pr2, is 0.39 or more and 0.70 or less. Hereinafter, the piezoelectric layer 70 according to the present invention will be described with reference to FIG. 4A is a schematic diagram showing a PV curve of the piezoelectric layer, and FIG. 4B is a diagram showing a triangular wave applied to the piezoelectric layer.

  When a voltage of 30 V 1 kHz triangular wave for one period, that is, for example, a triangular wave-shaped voltage shown in FIG. 4B is applied to the piezoelectric layer 70 and thus the piezoelectric element, first, as shown by the solid line in FIG. The amount of polarization increases as the applied voltage increases, and reaches the saturation saturation amount Pm + on the positive side when the applied voltage is + 30V. Next, although the polarization amount decreases as the applied voltage decreases, the plus side residual polarization amount Pr + is when the applied voltage becomes 0V. Subsequently, the amount of polarization continues to decrease as the applied voltage decreases, and reaches the negative saturation polarization amount Pm− when the applied voltage is −30V. Next, the amount of polarization increases again as the applied voltage increases. However, the amount of polarization when the applied voltage becomes 0 V again, that is, the amount of polarization when the application of the triangular wave for one cycle is completed, remains on the negative side. The amount of polarization Pr1. Then, if the voltage is not applied after the application of the triangular wave for one period is completed, the charge is released and the absolute value of the polarization amount decreases. The residual polarization amount after being left when the standing time is set to 1.0 second, that is, the residual polarization amount when 1.0 second has elapsed after the application of the triangular wave for one period is finished is Pr2. Pr2 is obtained from a PV curve (hysteresis) obtained by applying one period of the first triangular wave and then applying one period of the triangular wave again after 1.0 second has elapsed. In the present invention, the ratio Pr2 / Pr1 between Pr1 and Pr2 is set within a predetermined range. When the triangular wave is applied to the piezoelectric layer 70 that is not polarized, that is, the polarization amount is 0, the polarization amount from 0 V to +30 V is as shown by the dotted line in FIG. After reaching + 30V and reaching Pm +, the behavior is the same as the solid line described above.

  Here, as described in Patent Document 2 and the like, a composite oxide containing Bi, Ba, Fe, and Ti is known as a piezoelectric material. In the present invention, the ratio Pr2 / Pr1 of the predetermined remanent polarization amounts Pr1 and Pr2 when a predetermined triangular wave is applied is made of such a complex oxide containing Bi, Ba, Fe, and Ti is 0.39 or more. By using the piezoelectric layer 70 of 0.70 or less, as shown in Examples and Comparative Examples described later, the Pr2 / Pr1 is significantly displaced as compared with those of less than 0.39 or more than 0.70. The amount can be improved. Further, the piezoelectric layer obtained from the PV curve (hysteresis) obtained by applying one period of a triangular wave of 30 V 1 kHz was determined for the residual polarization amount Pr1, then left for 1.0 second, and then again at 30 V 1 kHz. One period of the triangular wave is applied, the residual polarization amount Pr2 is obtained from the obtained PV curve (hysteresis), and the ratio Pr2 / Pr1, which is the ratio of Pr1 to Pr2, is calculated. Whether or not the piezoelectric element using the piezoelectric layer generates a large amount of displacement can be easily evaluated by checking whether or not it falls within the range of 39 to 0.70.

  The relationship between the absolute value of the residual polarization amount of the piezoelectric material, for example, the absolute value of Pr1 and Pr2, and the displacement amount is not a simple relationship that the displacement amount increases when the residual polarization amount Pr1 or Pr2 is large. In the case of a piezoelectric material made of a composite oxide containing Bi, Ba, Fe and Ti, if Pr2 / Pr1 is 0.39 or more and 0.70 or less, Pr2 / Pr1 is less than 0.39 or more than 0.70. It has been found in the present invention that the amount of displacement is significantly larger than that of the present invention.

  Increasing the number of element defects in the composite oxide containing Bi, Ba, Fe, and Ti constituting the piezoelectric layer 70 tends to decrease the Pr2 / Pr1, and the composite oxide has a large amount of impurities that do not contribute to piezoelectricity. When included, the Pr2 / Pr1 tends to decrease, and when the crystallinity of the composite oxide is increased, the Pr2 / Pr1 tends to increase.

  In addition, the piezoelectric layer 70 made of a complex oxide containing Bi, Ba, Fe, and Ti tends to have a large Pr1 when the film thickness is large. The tendency for Pr1 to increase with the film thickness is a characteristic peculiar to a composite oxide containing Bi, Ba, Fe, and Ti, and for example, tends not to be found in barium titanate-based piezoelectric materials.

  As will be described later, a buffer layer made of a piezoelectric material or the like is provided on the first electrode 60 as the lowermost layer of the piezoelectric layer 70, or firing when producing a composite oxide containing Bi, Ba, Fe, and Ti. The value of Pr2 / Pr1 can also be adjusted by changing firing conditions such as temperature.

  Further, a buffer layer made of a complex oxide having a perovskite structure may be provided as the lowermost layer of the piezoelectric layer 70. Examples of the composite oxide having a perovskite structure constituting the buffer layer include piezoelectric materials such as composite oxides containing Bi, Fe, Ti, and Co. By providing such a buffer layer as the lowermost layer of the piezoelectric layer 70, the value of Pr2 / Pr1 can be adjusted to a predetermined value. The buffer layer is preferably very thin compared to the piezoelectric layer 70, and is preferably about 10 to 100 nm, for example.

  Each second electrode 80, which is an individual electrode of the piezoelectric element 300, is drawn from the vicinity of the end on the ink supply path 14 side and extends to the elastic film 50 or an insulator film provided as necessary. For example, a lead electrode 90 made of gold (Au) or the like is connected.

  At least a part of the manifold 100 is formed on the flow path forming substrate 10 on which such a piezoelectric element 300 is formed, that is, on the first electrode 60, the elastic film 50, the insulator film provided as necessary, and the lead electrode 90. A protective substrate 30 having a manifold portion 31 constituting the above is joined via an adhesive 35. In this embodiment, the manifold portion 31 penetrates the protective substrate 30 in the thickness direction and is formed across the width direction of the pressure generating chamber 12. As described above, the communication portion 13 of the flow path forming substrate 10. The manifold 100 is configured as a common ink chamber for the pressure generation chambers 12. Alternatively, the communication portion 13 of the flow path forming substrate 10 may be divided into a plurality of pressure generation chambers 12 and only the manifold portion 31 may be used as a manifold. Further, for example, only the pressure generation chamber 12 is provided in the flow path forming substrate 10 and a member (for example, an elastic film 50, an insulator film provided as necessary, etc.) interposed between the flow path forming substrate 10 and the protective substrate 30 is provided. ) May be provided with an ink supply path 14 for communicating the manifold 100 and each pressure generating chamber 12.

  A piezoelectric element holding portion 32 having a space that does not hinder the movement of the piezoelectric element 300 is provided in a region of the protective substrate 30 that faces the piezoelectric element 300. The piezoelectric element holding part 32 only needs to have a space that does not hinder the movement of the piezoelectric element 300, and the space may be sealed or unsealed.

  As such a protective substrate 30, it is preferable to use substantially the same material as the coefficient of thermal expansion of the flow path forming substrate 10, for example, glass, ceramic material, etc. In this embodiment, the same material as the flow path forming substrate 10 The silicon single crystal substrate was used.

  The protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the thickness direction. The vicinity of the end portion of the lead electrode 90 drawn from each piezoelectric element 300 is provided so as to be exposed in the through hole 33.

  A drive circuit 120 for driving the piezoelectric elements 300 arranged in parallel is fixed on the protective substrate 30. For example, a circuit board or a semiconductor integrated circuit (IC) can be used as the drive circuit 120. The drive circuit 120 and the lead electrode 90 are electrically connected via a connection wiring 121 made of a conductive wire such as a bonding wire.

  In addition, a compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the protective substrate 30. Here, the sealing film 41 is made of a material having low rigidity and flexibility, and one surface of the manifold portion 31 is sealed by the sealing film 41. The fixing plate 42 is formed of a relatively hard material. Since the area of the fixing plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction, one surface of the manifold 100 is sealed only with a flexible sealing film 41. Has been.

  In such an ink jet recording head I of this embodiment, ink is taken in from an ink introduction port connected to an external ink supply means (not shown), and the interior from the manifold 100 to the nozzle opening 21 is filled with ink, and then driven. In accordance with a recording signal from the circuit 120, a voltage is applied between each of the first electrode 60 and the second electrode 80 corresponding to the pressure generating chamber 12, and the elastic film 50, the adhesion layer 56, the first electrode 60, and the piezoelectric body. By bending and deforming the layer 70, the pressure in each pressure generation chamber 12 is increased, and ink droplets are ejected from the nozzle openings 21.

  Next, an example of a method for manufacturing the ink jet recording head of the present embodiment will be described with reference to FIGS. 5 to 9 are cross-sectional views in the longitudinal direction of the pressure generating chamber.

First, as shown in FIG. 5A, a silicon dioxide film made of silicon dioxide (SiO ₂ ) or the like constituting the elastic film 50 is formed by thermal oxidation or the like on the surface of a flow path forming substrate wafer 110 that is a silicon wafer. To do. Next, as shown in FIG. 5B, an adhesion layer 56 made of titanium oxide or the like is formed on the elastic film 50 (silicon dioxide film) by sputtering or thermal oxidation.

  Next, as shown in FIG. 6A, a first electrode 60 made of platinum, iridium, iridium oxide, or a laminated structure thereof is formed on the entire surface of the adhesion layer 56 by a sputtering method, a vapor deposition method, or the like. . Next, as shown in FIG. 6B, patterning is performed simultaneously on the first electrode 60 so that the side surfaces of the adhesion layer 56 and the first electrode 60 are inclined using a resist (not shown) having a predetermined shape as a mask.

  Next, after peeling off the resist, the piezoelectric layer 70 is laminated on the first electrode 60. The method for manufacturing the piezoelectric layer 70 is not particularly limited. For example, a MOD (Metal film) that obtains a piezoelectric layer (piezoelectric film) made of a metal oxide by coating and drying a solution containing a metal complex and firing at a high temperature. The piezoelectric layer 70 can be manufactured by using a chemical solution method such as an —Organic Decomposition ”method or a sol-gel method. In addition, the piezoelectric layer 70 is manufactured by a vapor phase method, a liquid phase method, or a solid phase method such as a laser ablation method, a sputtering method, a pulse laser deposition method (PLD method), a CVD method, an aerosol deposition method, or the like. be able to.

  As a specific example of the formation procedure when the piezoelectric layer 70 is formed by the chemical solution method, first, as shown in FIG. 6C, a metal complex, specifically Bi, is formed on the first electrode 60. The piezoelectric precursor film 71 is formed by applying a piezoelectric film forming composition (precursor solution) made of a MOD solution or a sol containing a metal complex containing Fe, Ba and Ti using a spin coating method or the like. Form (application process).

  The precursor solution to be applied is obtained by mixing a metal complex capable of forming a composite oxide containing Bi, Fe, Ba and Ti by firing, and dissolving or dispersing the mixture in an organic solvent. When forming the piezoelectric layer 70 made of a complex oxide containing Mn, Co, and Cr, a precursor solution containing a metal complex containing Mn, Co, and Cr is further used. What is necessary is just to mix the mixing ratio of the metal complex which each contains Bi, Fe, Ba, and Ti, and the metal complex which has Mn, Co, and Cr mixed as needed so that each metal may become a desired molar ratio. As the metal complex containing Bi, Fe, Ba, Ti, Mn, Co, and Cr, for example, alkoxide, organic acid salt, β diketone complex, and the like can be used. Examples of the metal complex containing Bi include bismuth 2-ethylhexanoate and bismuth acetate. Examples of the metal complex containing Fe include iron 2-ethylhexanoate, iron acetate, and tris (acetylacetonato) iron. Examples of the metal complex containing Ba include barium isopropoxide, barium 2-ethylhexanoate, barium acetylacetonate, and the like. Examples of the metal complex containing Ti include titanium isopropoxide, titanium 2-ethylhexanoate, titanium (di-i-propoxide) bis (acetylacetonate), and the like. Examples of the metal complex containing Mn include manganese 2-ethylhexanoate and manganese acetate. Examples of the organometallic compound containing Co include cobalt 2-ethylhexanoate and cobalt (III) acetylacetonate. Examples of the organometallic compound containing Cr include chromium 2-ethylhexanoate. Of course, you may use Bi, Fe, Ba, Ti, and the metal complex containing 2 or more types of Mn, Co, and Cr contained as needed. Examples of the solvent for the precursor solution include propanol, butanol, pentanol, hexanol, octanol, ethylene glycol, propylene glycol, octane, decane, cyclohexane, xylene, toluene, tetrahydrofuran, acetic acid, octylic acid, and the like.

Next, the piezoelectric precursor film 71 is heated to a predetermined temperature (for example, 150 to 200 ° C.) and dried for a predetermined time (drying step). Next, the dried piezoelectric precursor film 71 is degreased by heating it to a predetermined temperature (for example, 350 to 450 ° C.) and holding it for a certain time (degreasing process). The degreasing referred to here is to release the organic component contained in the piezoelectric precursor film 71 as, for example, NO ₂ , CO ₂ , H ₂ O, or the like. The atmosphere of the drying step or the degreasing step is not limited, and may be in the air, in an oxygen atmosphere, or in an inert gas. In addition, you may perform an application | coating process, a drying process, and a degreasing process in multiple times.

  Next, as shown in FIG. 7A, the piezoelectric precursor film 71 is crystallized by heating to a predetermined temperature, for example, about 600 to 850 ° C., and holding it for a certain time, for example, 1 to 10 minutes. Then, a piezoelectric film 72 made of a composite oxide containing bismuth, iron, barium and titanium and having a perovskite structure is formed (firing step). Also in this firing step, the atmosphere is not limited, and may be in the air, in an oxygen atmosphere, or in an inert gas. Examples of the heating device used in the drying step, the degreasing step, and the firing step include an RTA (Rapid Thermal Annealing) device that heats by irradiation with an infrared lamp, a hot plate, and the like.

  Next, the above-described coating process, drying process, degreasing process, coating process, drying process, degreasing process, and firing process are repeated a plurality of times in accordance with a desired film thickness and the like, and the piezoelectric layer 70 composed of a plurality of piezoelectric films 72. As shown in FIG. 7B, a piezoelectric layer 70 having a predetermined thickness composed of a plurality of layers of piezoelectric films 72 is formed. For example, when the film thickness of the coating solution per one time is about 0.1 μm, for example, the entire film thickness of the piezoelectric layer 70 composed of the ten piezoelectric films 72 is about 1.1 μm. In the present embodiment, the piezoelectric film 72 is provided by being laminated, but only one layer may be provided.

  When a buffer layer is provided in the lowermost layer of the piezoelectric layer 70, a buffer layer may be provided on the first electrode 60 and a piezoelectric film may be laminated on the buffer layer. The method for producing the buffer layer is not particularly limited, and can be produced by the same method as that for the piezoelectric layer 70 described above. For example, a metal oxide is obtained by applying and drying a solution containing a metal complex and firing at a high temperature. Chemical solution methods such as MOD method and sol-gel method to obtain a buffer layer consisting of, laser ablation method, sputtering method, pulse laser deposition method (PLD method), CVD method, aerosol deposition method, etc. It can also be produced by a gas phase method, a liquid phase method or a solid phase method. Examples of the metal complex that is a raw material when the buffer layer is formed by the chemical solution method include the same compounds as those described in the method for manufacturing the piezoelectric layer 70.

  When the piezoelectric layer 70 is manufactured as described above, the element ratio and impurity amount of the precursor solution, the presence or absence of the buffer layer as the lowermost layer of the piezoelectric layer 70, the thickness of the piezoelectric layer 70, the piezoelectric layer 70, and the like. The value of Pr2 / Pr1 can be adjusted by adjusting the firing conditions such as the firing temperature of the firing step. The Pr2 / Pr1 value varies depending on the element ratio and the amount of impurities in the precursor solution, the presence or absence of the buffer layer, the thickness of the piezoelectric layer 70, and the firing conditions of the piezoelectric layer 70, so the balance of each condition is adjusted. There is a need to.

  After the piezoelectric layer 70 is formed in this way, as shown in FIG. 8A, the second electrode 80 made of platinum or the like is formed on the piezoelectric layer 70 by a sputtering method or the like, and each pressure generating chamber 12 is formed. Then, the piezoelectric layer 70 and the second electrode 80 are simultaneously patterned in a region opposite to each other to form the piezoelectric element 300 including the first electrode 60, the piezoelectric layer 70, and the second electrode 80. The patterning of the piezoelectric layer 70 and the second electrode 80 can be performed collectively by dry etching via a resist (not shown) formed in a predetermined shape. Then, you may anneal in the temperature range of 600-850 degreeC as needed, for example. Thereby, a good interface between the piezoelectric layer 70 and the first electrode 60 or the second electrode 80 can be formed, and the crystallinity of the piezoelectric layer 70 can be increased.

  Next, as shown in FIG. 8B, a lead electrode 90 made of, for example, gold (Au) or the like is formed over the entire surface of the flow path forming substrate wafer 110, and then a mask pattern made of, for example, a resist or the like. Patterning is performed for each piezoelectric element 300 via (not shown).

  Next, as shown in FIG. 8C, a protective substrate wafer 130 that is a silicon wafer and serves as a plurality of protective substrates 30 is placed on the piezoelectric element 300 side of the flow path forming substrate wafer 110 with an adhesive 35 interposed therebetween. After the bonding, the flow path forming substrate wafer 110 is thinned to a predetermined thickness.

  Next, as shown in FIG. 9A, a mask film 52 is newly formed on the flow path forming substrate wafer 110 and patterned into a predetermined shape.

  Then, as shown in FIG. 9B, the flow path forming substrate wafer 110 is anisotropically etched (wet etching) using an alkaline solution such as KOH through the mask film 52, thereby forming the piezoelectric element 300. Corresponding pressure generating chambers 12, communication portions 13, ink supply passages 14, communication passages 15 and the like are formed.

  Thereafter, unnecessary portions of the outer peripheral edge portions of the flow path forming substrate wafer 110 and the protective substrate wafer 130 are removed by cutting, for example, by dicing. Then, after removing the mask film 52 on the surface opposite to the protective substrate wafer 130 of the flow path forming substrate wafer 110, the nozzle plate 20 having the nozzle openings 21 formed therein is bonded, and the protective substrate wafer 130 is also formed. The compliance substrate 40 is bonded to the substrate, and the flow path forming substrate wafer 110 or the like is divided into a single chip size flow path forming substrate 10 or the like as shown in FIG. To do.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.

Example 1
First, a 1200 nm-thickness silicon oxide (SiO ₂ ) film was formed on the surface of a (100) single crystal silicon (Si) substrate by thermal oxidation. Next, a titanium film having a thickness of 40 nm was formed on the SiO ₂ film by RF magnetron sputtering, and a titanium oxide film was formed by thermal oxidation. Next, a platinum film (first electrode 60) having a thickness of 100 nm and oriented in the (111) plane was formed on the titanium oxide film by RF magnetron sputtering.

  Next, a buffer layer made of a complex oxide having a perovskite structure was formed on the first electrode 60 as the lowermost layer of the piezoelectric layer 70. The method is as follows. First, an n-octane solution of bismuth 2-ethylhexanoate, iron 2-ethylhexanoate, titanium 2-ethylhexanoate and cobalt 2-ethylhexanoate has a molar concentration ratio of Bi: Fe: Ti: Co = 100: A buffer layer precursor solution was prepared by mixing at 80:10:10.

  Next, the buffer layer precursor solution was dropped on the substrate on which the titanium oxide film and the platinum film were formed, and the substrate was rotated at 3000 rpm to form a piezoelectric precursor film by spin coating (buffer layer coating). Process). Next, it was dried at 180 ° C. for 2 minutes on a hot plate (buffer layer drying step). Subsequently, degreasing was performed at 450 ° C. for 2 minutes (buffer layer degreasing step). Thereafter, firing was performed at 750 ° C. for 2 minutes in an RTA (Rapid Thermal Annealing) apparatus in an oxygen atmosphere (buffer layer firing step).

  Next, a piezoelectric film was formed on this buffer layer to obtain a piezoelectric layer 70. The method is as follows. First, each n-octane solution of bismuth 2-ethylhexanoate, iron 2-ethylhexanoate, manganese 2-ethylhexanoate, barium 2-ethylhexanoate and titanium 2-ethylhexanoate, each element in molar ratio A precursor solution was prepared by mixing Bi: Ba: Fe: Ti: Mn = 75: 25: 71.25: 25: 3.75.

  And this precursor solution was dripped on the board | substrate with which the buffer layer top was formed, the board | substrate was rotated at 3000 rpm, and the piezoelectric precursor film | membrane was formed (application | coating process). Next, it was dried at 180 ° C. for 2 minutes on a hot plate (drying process). Next, degreasing was performed at 350 ° C. for 2 minutes (degreasing step). After repeating this coating step, drying step, and degreasing step twice, firing was performed in an oxygen atmosphere with a RTA (Rapid Thermal Annealing) apparatus at 800 ° C. for 2 minutes (firing step). Next, in this example, the step of performing the baking step of baking all at once after repeating the coating step, the drying step, and the degreasing step twice is repeated in this example, one buffer layer, and a total of 24 piezoelectric steps. A piezoelectric layer 70 having a total thickness of 1820 nm made of a body film was formed.

  Thereafter, a platinum film (second electrode 80) having a thickness of 100 nm is formed as a second electrode 80 on the piezoelectric layer 70 by sputtering, and then baked at 750 ° C. for 5 minutes in an oxygen atmosphere using an RTA apparatus. As a result, a piezoelectric element 300 was formed in which the composite oxide containing Bi, Fe, Mn, Ba and Ti and having a perovskite structure was used as the piezoelectric layer 70.

(Example 2)
The same operation as in Example 1 was performed except that the step of performing the baking step of collectively baking was repeated 10 times, and the piezoelectric layer was formed by a total of 20 coatings and had a total thickness of 1520 nm. Went.

(Example 3)
The same operation as in Example 1 was performed except that the step of performing the baking step of batch baking was repeated 8 times, and the piezoelectric layer was formed by a total of 16 coatings to have a piezoelectric layer 70 with a total thickness of 1220 nm. Went.

Example 4
The same operation as in Example 3 was performed except that the firing temperature in the firing step was 850 ° C.

(Example 5)
The same operation as in Example 1 was repeated except that the step of performing the baking step of baking all at once was repeated seven times, and the piezoelectric film was formed in a total of 14 times, and the piezoelectric layer 70 had a thickness of 1070 nm as a whole. Went.

(Example 6)
The same operation as in Example 5 was performed except that the firing temperature in the firing step was 750 ° C.

(Example 7)
The same operation as in Example 6 was performed, except that no buffer layer was provided.

(Comparative Example 1)
Except using the precursor solution mixed so that each element might become Bi: Ba: Fe: Ti: Mn = 77.5: 22.5: 73.625: 22.5: 3.875 in molar ratio, The same operation as in Example 5 was performed.

(Comparative Example 2)
The same operation as in Example 1 was performed except that the step of performing the baking step of baking in a lump was repeated four times, and the piezoelectric layer was formed with a total of eight times of application and had a total thickness of 620 nm. Went.

(Comparative Example 3)
The same operation as in Example 1 is repeated except that the step of performing the baking step of baking at once is repeated three times, and the piezoelectric layer is formed with a total of six times of coating and has a total thickness of 470 nm. Went.

(Test Example 1)
For each of the piezoelectric elements of Examples 1 to 7 and Comparative Examples 1 to 3, Pr2 / Pr1, which is the ratio of Pr1 and Pr2, was obtained. Specifically, first, using “FCE-1A” manufactured by Toyo Technica Co., Ltd., using an electrode pattern of φ = 500 μm, a triangular wave of 30 V frequency 1 kHz is applied to the piezoelectric layer 70 for one period at room temperature, Pr1 was calculated | required from the obtained P (polarization amount) -V (voltage) curve. Then, after the application of the triangular wave for one period is completed, the triangular wave is left for 1.0 second, and then one period of the triangular wave of 30 V and 1 kHz is applied to the piezoelectric layer 70 again, and the obtained P (polarization amount) −V Pr2 was determined from the (voltage) curve. Table 1 shows Pr2 / Pr1 calculated from Pr1 and Pr2.

(Test Example 2)
About each piezoelectric element of Examples 1-7 and Comparative Examples 1-3, the voltage of 30V is applied at the frequency of 1 kHz using the electrode pattern of (phi) = 500micrometer using the displacement measuring apparatus (DBLI) made from an Axact company at room temperature. S (electric field induced strain (displacement amount)) was obtained. From the results of Test Example 1 and Test Example 2, the relationship between Pr2 / Pr1 and the displacement (denoted as Dpp2 in Table 1) is shown in FIG.

  As a result, in Examples 1 to 7 in which Pr2 / Pr1 is 0.39 or more and 0.70 or less, the amount of displacement is significantly larger than the comparative examples in which Pr2 / Pr1 is less than 0.39 or more than 0.70. Was big.

(Other embodiments)
As mentioned above, although one Embodiment of this invention was described, the basic composition of this invention is not limited to what was mentioned above. For example, in the above-described embodiment, the silicon single crystal substrate is exemplified as the flow path forming substrate 10, but the present invention is not particularly limited thereto, and for example, a material such as an SOI substrate or glass may be used.

  Furthermore, in the above-described embodiment, the piezoelectric element 300 in which the first electrode 60, the piezoelectric layer 70, and the second electrode 80 are sequentially stacked on the substrate (the flow path forming substrate 10) is illustrated, but the present invention is not particularly limited thereto. For example, the present invention can also be applied to a longitudinal vibration type piezoelectric element in which piezoelectric materials and electrode forming materials are alternately stacked to expand and contract in the axial direction.

  In addition, the ink jet recording head of these embodiments constitutes a part of a recording head unit including an ink flow path communicating with an ink cartridge or the like, and is mounted on the ink jet recording apparatus. FIG. 11 is a schematic view showing an example of the ink jet recording apparatus.

  In the ink jet recording apparatus II shown in FIG. 11, the recording head units 1A and 1B having the ink jet recording head I are detachably provided with cartridges 2A and 2B constituting the ink supply means, and the recording head units 1A and 1B. Is mounted on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction. The recording head units 1A and 1B, for example, are configured to eject a black ink composition and a color ink composition, respectively.

  The driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and timing belt 7 (not shown), so that the carriage 3 on which the recording head units 1A and 1B are mounted is moved along the carriage shaft 5. The On the other hand, the apparatus body 4 is provided with a platen 8 along the carriage shaft 5, and a recording sheet S that is a recording medium such as paper fed by a paper feed roller (not shown) is wound around the platen 8. It is designed to be transported.

  In the above-described embodiment, the ink jet recording head has been described as an example of the liquid ejecting head. However, the present invention is widely applied to all liquid ejecting heads, and the liquid ejecting ejects a liquid other than ink. Of course, it can also be applied to the head. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used in the manufacture of color filters such as liquid crystal displays, organic EL displays, and FEDs (field emission displays). Examples thereof include an electrode material ejection head used for electrode formation, a bioorganic matter ejection head used for biochip production, and the like.

  Further, the piezoelectric element according to the present invention is not limited to the piezoelectric element used in the liquid ejecting head, and can be used in other devices. Other devices include, for example, an ultrasonic device such as an ultrasonic transmitter, an ultrasonic motor, a temperature-electric converter, a pressure-electric converter, a ferroelectric transistor, a piezoelectric transformer, and a filter for blocking harmful rays such as infrared rays. And filters such as an optical filter using a photonic crystal effect by quantum dot formation, an optical filter using optical interference of a thin film, and the like. The present invention can also be applied to a piezoelectric element used as a sensor and a piezoelectric element used as a ferroelectric memory. Examples of the sensor using the piezoelectric element include an infrared sensor, an ultrasonic sensor, a thermal sensor, a pressure sensor, a pyroelectric sensor, and a gyro sensor (angular velocity sensor).

  I ink jet recording head (liquid ejecting head), II ink jet recording apparatus (liquid ejecting apparatus), 10 flow path forming substrate, 12 pressure generating chamber, 13 communicating portion, 14 ink supply path, 20 nozzle plate, 21 nozzle opening, 30 protective substrate, 31 manifold portion, 32 piezoelectric element holding portion, 40 compliance substrate, 50 elastic film, 60 first electrode, 70 piezoelectric layer, 80 second electrode, 90 lead electrode, 100 manifold, 120 drive circuit, 300 piezoelectric element

Claims (3)

A liquid ejecting head that discharges liquid from a nozzle opening, comprising: a piezoelectric element comprising a piezoelectric layer and an electrode provided on the piezoelectric layer;
The piezoelectric layer is made of a complex oxide having a perovskite structure including bismuth, iron, barium, and titanium, and a residual polarization amount Pr1 at the end of application when a 30 V 1 kHz triangular wave period is applied, and the application end. A liquid ejecting head, wherein Pr2 / Pr1, which is a ratio to a residual polarization amount Pr2 when 1.0 second has elapsed from time, is 0.39 or more and 0.70 or less.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1.   A piezoelectric element comprising a piezoelectric layer and an electrode provided on the piezoelectric layer, wherein the piezoelectric layer is made of a complex oxide having a perovskite structure including bismuth, iron, barium, and titanium, and is 30 V 1 kHz Pr2 / Pr1, which is the ratio of the residual polarization amount Pr1 at the end of application when applying one period of the triangular wave and the residual polarization amount Pr2 after 1.0 second from the end of the application, is 0.39. A piezoelectric element characterized by being 0.70 or more and 0.70 or less.

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