JP2009049433A - Piezoelectric element, liquid-jet head, method for manufacturing the same, and liquid-jet apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric element, having high breakdown voltage and long lifetime durability, and its manufacturing method; and to provide a liquid ejection head and its manufacturing process, and a liquid ejector. <P>SOLUTION: The method for manufacturing a piezoelectric element comprises: a step for forming the lower electrode on a substrate; a step for forming a piezoelectric layer on the lower electrode by forming a piezoelectric precursor film containing Pb, Zr and Ti, such that composition ratio after calcination becomes Pb/(Zr+Ti)=1.0 to 1.3 and at least one additive selected from among a group of manganese, nickel and strontium is added to the precursor film and then calcinating the piezoelectric precursor film at 650-750°C for 0.5-3 hours; and a step for forming an upper electrode on the piezoelectric layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric element including a lower electrode, a piezoelectric layer, and an upper electrode and a manufacturing method thereof, and more particularly to a liquid ejecting head that discharges liquid droplets from a nozzle opening, a manufacturing method thereof, and a piezoelectric element used in a liquid ejecting apparatus.

  A part of the pressure generation chamber communicating with the nozzle opening for discharging ink droplets is constituted by a vibration plate, and the vibration plate is deformed by a piezoelectric element to pressurize the ink in the pressure generation chamber to discharge ink droplets from the nozzle opening. Inkjet recording heads have been put into practical use. For example, in such an ink jet recording head, a uniform piezoelectric material layer is formed over the entire surface of the diaphragm by a film forming technique, and the piezoelectric material layer is cut into a shape corresponding to the pressure generating chamber by a lithography method. Some piezoelectric elements are formed so as to be independent for each pressure generating chamber.

  In addition, as a piezoelectric element used in such an ink jet recording head, by specifying the content of a halogen-based substance as a composition of the piezoelectric layer, the withstand voltage of the piezoelectric layer is improved by suppressing the leakage current Has been proposed (see, for example, Patent Document 1).

  However, in Patent Document 1, although the leakage current of the piezoelectric layer can be suppressed, the electrical resistivity of the piezoelectric layer is not defined. When the electrical resistivity is low, there is a problem that the leakage current increases and the durability of the piezoelectric layer is lowered.

  Such a problem is not limited to a liquid jet head typified by an ink jet recording head and a method for manufacturing the same, and similarly exists in other piezoelectric elements and methods for manufacturing the same.

JP 2004-107181 A (claims, page 11)

  In view of such circumstances, it is an object of the present invention to provide a piezoelectric element having a high withstand voltage and a long durability life, a manufacturing method thereof, a liquid ejecting head, a manufacturing method thereof, and a liquid ejecting apparatus.

A first aspect of the present invention that solves the above problems includes a step of forming a lower electrode on a substrate, Pb, Zr, and Ti on the lower electrode, and a composition ratio after firing is Pb / (Zr + Ti ) = 1.0 to 1.3 and at least one additive selected from the group consisting of manganese, nickel and strontium is added to form a piezoelectric precursor film, A method for manufacturing a piezoelectric element, comprising: a step of forming a piezoelectric layer by baking at 750 ° C. for 0.5 to 3 hours; and a step of forming an upper electrode on the piezoelectric layer. is there.
In the first aspect, a piezoelectric element with good crystallinity and high stability can be formed by containing excess lead and setting the firing temperature and firing time to a predetermined temperature and a predetermined time.
Moreover, by adding a predetermined additive, a piezoelectric element having a desired electrical resistivity and withstand voltage can be obtained, and the durability can be extended to improve the reliability.

According to a second aspect of the present invention, there is provided the method for manufacturing a piezoelectric element according to the first aspect, wherein the additive is added in an amount of 10 mol% or less.
In the second aspect, by setting the addition amount to a predetermined amount, it is possible to prevent the displacement characteristics of the piezoelectric element from being deteriorated by an excessive additive.

According to a third aspect of the present invention, in the step of forming the piezoelectric layer, the piezoelectric layer is repeatedly formed by forming a piezoelectric film by firing a plurality of piezoelectric precursor films. The piezoelectric film firing time in each piezoelectric film forming step is 0.5 hour or more, and the total firing time of the piezoelectric layer is 3 hours or less. Or it exists in the manufacturing method of the piezoelectric element of 2 aspect.
In the third aspect, a piezoelectric layer having a desired thickness can be formed with high accuracy, and a piezoelectric layer with good crystallinity and high stability can be formed.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a liquid ejecting head, which is manufactured by the method for manufacturing a piezoelectric element according to any one of the first to third aspects.
According to the fourth aspect, it is possible to obtain a liquid jet head that has a long durability life and improved reliability.

According to a fifth aspect of the present invention, there is provided at least one additive selected from the group consisting of a lower electrode, a piezoelectric layer and an upper electrode provided on a substrate, wherein the piezoelectric layer is made of manganese, nickel and strontium. The piezoelectric element is characterized in that the piezoelectric element layer has an electrical resistivity of 20 MΩ · cm or more.
In the fifth aspect, by setting the electrical resistivity of the piezoelectric layer to a predetermined value, the withstand voltage can be improved and the durability life can be extended.
Moreover, by adding a predetermined additive, a piezoelectric element having a desired electrical resistivity and withstand voltage can be obtained, and the durability can be extended to improve the reliability.

A sixth aspect of the present invention is the piezoelectric element according to the fifth aspect, wherein the piezoelectric layer has a withstand voltage of 900 kV / cm or more.
In the sixth aspect, by setting the withstand voltage of the piezoelectric layer to a predetermined value, the durability life can be extended and the reliability can be improved.

According to a seventh aspect of the present invention, in the piezoelectric element according to the fifth or sixth aspect, the leakage current of the piezoelectric layer is 1 × 10 ⁻⁸ A / cm ² or less.
In the seventh aspect, by setting the leakage current of the piezoelectric layer to a predetermined value, the durability life can be extended and the reliability can be improved.

An eighth aspect of the present invention is the piezoelectric element according to any one of the fifth to seventh aspects, wherein the piezoelectric layer has a relative dielectric constant of 750 to 1500.
In the eighth aspect, the crystallinity of the piezoelectric layer is greatly improved. Therefore, it is possible to provide a piezoelectric element having excellent displacement characteristics and a high withstand voltage and a long durability life.

According to a ninth aspect of the present invention, in any one of the fifth to eighth aspects, the coercive electric field of the piezoelectric layer is 15 to 30 kV / cm and the remanent polarization strength is 10 to 25 μC / cm ² . It exists in the piezoelectric element of an aspect.
In the ninth aspect, the crystallinity of the piezoelectric layer becomes better, and the displacement characteristics and the durability life of the piezoelectric element are further improved.

According to a tenth aspect of the present invention, there is provided at least one additive selected from the group consisting of a lower electrode, a piezoelectric layer and an upper electrode provided on a substrate, wherein the piezoelectric layer is made of manganese, nickel and strontium. The piezoelectric layer has an electrical resistivity of 20 MΩ · cm or more, a leakage current of 1 × 10 ⁻⁸ A / cm ² or less, and a withstand voltage of 900 kV / cm or more. It is in the piezoelectric element.
In the tenth aspect, by setting the electrical resistivity, leakage current, and withstand voltage of the piezoelectric layer to predetermined values, the durability life can be extended and the reliability can be improved.
Moreover, by adding a predetermined additive, a piezoelectric element having a desired electrical resistivity and withstand voltage can be obtained, and the durability can be extended to improve the reliability.

According to an eleventh aspect of the present invention, there is provided a flow path including the piezoelectric element according to any one of the fifth to tenth aspects and a pressure generation chamber in which the piezoelectric element is provided via a vibration plate and communicates with a nozzle opening. A liquid jet head comprising a substrate.
In the eleventh aspect, it is possible to obtain a liquid jet head that has improved durability and improved reliability.

According to a twelfth aspect of the present invention, there is provided a liquid ejecting apparatus including the liquid ejecting head according to the eleventh aspect.
In the twelfth aspect, it is possible to obtain a liquid ejecting apparatus that has improved durability and improved reliability.

Hereinafter, the present invention will be described in detail based on embodiments.
(Embodiment 1)
FIG. 1 is an exploded perspective view of the ink jet recording head according to the first embodiment of the present invention, and FIG. 2 is a plan view of FIG.

  As shown in the drawing, the flow path forming substrate 10 is made of a silicon single crystal substrate in the present embodiment, and one surface thereof is made of silicon dioxide previously formed by thermal oxidation, and has an elastic film 50 having a thickness of 0.5 to 2 μm. Is formed.

  This flow path forming substrate 10 is provided with pressure generating chambers 12 partitioned by a plurality of partition walls 11 by anisotropic etching from the other side, and each pressure generating chamber 12 is disposed on the outer side in the longitudinal direction. A communication portion 13 constituting a part of the reservoir 100 serving as a common ink chamber is formed, and is communicated with one end portion in the longitudinal direction of each pressure generation chamber 12 via an ink supply path 14. 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.

Further, a nozzle plate 20 having a nozzle opening 21 communicating with the side opposite to the ink supply path 14 of each pressure generating chamber 12 on the opening surface side of the flow path forming substrate 10 is an adhesive, a heat-welded film, or the like. It is fixed through. The nozzle plate 20 has a thickness of, for example, 0.01 to 1 mm and a linear expansion coefficient of 300 ° C. or lower, for example, 2.5 to 4.5 [× 10 ⁻⁶ / ° C.], or Made of stainless steel. The nozzle plate 20 entirely covers one surface of the flow path forming substrate 10 on one surface, and also serves as a reinforcing plate that protects the silicon single crystal substrate from impact and external force. Further, the nozzle plate 20 may be formed of a material having substantially the same thermal expansion coefficient as that of the flow path forming substrate 10. In this case, since the deformation by heat of the flow path forming substrate 10 and the nozzle plate 20 is substantially the same, it can be easily joined using a thermosetting adhesive or the like.

On the other hand, an elastic film 50 made of silicon dioxide and having a thickness of, for example, about 1.0 μm is formed on the side opposite to the opening surface of the flow path forming substrate 10. An insulator film 55 made of zirconium oxide (ZrO ₂ ) or the like and having a thickness of, for example, about 0.4 μm is laminated. Further, on the insulator film 55, the lower electrode film 60 having a thickness of about 0.1 to 0.5 μm and lead zirconate titanate (PZT) or the like has a thickness of about 1.0 μm, for example. The piezoelectric layer 300 and an upper electrode film 80 made of gold, platinum, iridium, or the like and having a thickness of, for example, about 0.05 μm are laminated by a process described later to constitute the piezoelectric element 300.

  Here, the piezoelectric element 300 refers to a portion including the lower electrode film 60, the piezoelectric layer 70, and the upper electrode film 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 addition, here, a portion that is configured by any one of the patterned electrodes and the piezoelectric layer 70 and in which piezoelectric distortion is generated by applying a voltage to both electrodes is referred to as a piezoelectric active portion. In this embodiment, the lower electrode film 60 is a common electrode of the piezoelectric element 300, and the upper electrode film 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. In any case, a piezoelectric active part is formed for each pressure generating chamber 12. Further, here, the piezoelectric element 300 and the vibration plate that is displaced by driving the piezoelectric element 300 are collectively referred to as a piezoelectric actuator. In the example described above, the elastic film 50, the insulator film 55, and the lower electrode film 60 function as a diaphragm.

The piezoelectric layer 70 of the present embodiment has an electric resistivity of 20 MΩ · cm or more. By setting the piezoelectric layer 70 to such an electrical resistivity, an increase in leakage current can be prevented and the durable life of the piezoelectric layer 70 can be extended. The leakage current of the piezoelectric layer 70 is preferably 1 × 10 ⁻⁸ A / cm ² or less. The withstand voltage of the piezoelectric layer 70 is preferably 900 kV / cm or more. By setting the piezoelectric layer 70 to such a leakage current and withstand voltage, the durability life of the piezoelectric layer 70 can be extended.

Such a piezoelectric layer 70 has a relative dielectric constant of 750 to 1500. Further, such a piezoelectric layer 70 has a coercive electric field of Ec = 15 to 30 kV / cm (2Ec = 30 to 60 kV / cm) and a residual polarization strength of Pr = 10 to 25 μC / cm ² (2Pr = 20 to 50 μC / cm ² ). The coercive electric field Ec and the remanent polarization strength Pr of the piezoelectric layer 70 are values obtained from 2Ec and 2Pr of the hysteresis curve of the piezoelectric layer as shown in FIG. 3, for example.

The piezoelectric layer 70 having such characteristics has a very good piezoelectric constant, specifically, a piezoelectric constant d ₃₁ of 150 to 250 pC / N, and the displacement characteristics of the piezoelectric element 300 are improved.

As such a piezoelectric layer 70 of the present embodiment, a perovskite structure crystal film made of a ferroelectric ceramic material having an electromechanical conversion effect formed on the lower electrode film 60 can be cited. As a material of the piezoelectric layer 70, for example, a ferroelectric piezoelectric material such as lead zirconate titanate (PZT) or a material obtained by adding a metal oxide such as niobium oxide, nickel oxide or magnesium oxide to the piezoelectric material is suitable. It is. Specifically, lead titanate (PbTiO ₃ ), lead zirconate titanate (Pb (Zr, Ti) O ₃ ), lead zirconate (PbZrO ₃ ), lead lanthanum titanate ((Pb, La), TiO ₃ ) ) Lead lanthanum zirconate titanate ((Pb, La) (Zr, Ti) O ₃ ) or lead magnesium titanate zirconate titanate (Pb (Zr, Ti) (Mg, Nb) O ₃ ) or the like is used. it can. In this embodiment, the piezoelectric layer 70 is made of a material containing Pb (lead), Zr (zirconium), and Ti (titanium), and the composition ratio after firing is Pb / (Zr + Ti) = 1.0 to 1.3. It was made to become. As a result, it is possible to prevent excess lead from gathering at the grain boundaries and increasing the leakage current, thereby obtaining a predetermined leakage current.

  In addition, by adding at least one additive selected from nickel (Ni), manganese (Mn), and strontium (Sr) to the piezoelectric layer 70 of the present embodiment, the electrical property of the piezoelectric layer 70 can be reliably ensured. The resistivity, leak current, withstand voltage, relative dielectric constant, remanent polarization strength, coercive electric field, piezoelectric constant, and the like can be set to predetermined values. The addition of at least one additive selected from nickel (Ni), manganese (Mn), and strontium (Sr) causes the electrical resistivity, leakage current, withstand voltage, relative dielectric constant, and remanent polarization of the piezoelectric layer 70 to be added. This is one method of setting values such as strength, coercive electric field, and piezoelectric constant to predetermined values. The amount of such an additive is preferably a predetermined amount, particularly 10 mol% or less. Here, “less than or equal to 10 mol%” does not mean that the addition amount should be reduced as much as possible, but the reason that the displacement amount of the piezoelectric layer 70 is reduced when the addition amount of the additive is large. The upper limit is determined from

  Further, the thickness of the piezoelectric layer 70 is reduced to such a degree that cracks do not occur in the manufacturing process and is formed thick enough to exhibit sufficient displacement characteristics. For example, in this embodiment, the piezoelectric layer 70 is formed with a thickness of about 1 to 2 μm.

  Further, each upper electrode film 80 that 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 extended to the insulator film 55, for example, from gold (Au) or the like. Lead electrode 90 is connected.

  On the flow path forming substrate 10 on which such a piezoelectric element 300 is formed, that is, on the lower electrode film 60, the elastic film 50, and the lead electrode 90, a protection having a reservoir portion 31 constituting at least a part of the reservoir 100. The substrate 30 is bonded via an adhesive 34. In the present embodiment, the reservoir portion 31 is formed through the protective substrate 30 in the thickness direction and across the width direction of the pressure generation chamber 12. As described above, the communication portion 13 of the flow path forming substrate 10. The reservoir 100 is configured as a common ink chamber for the pressure generation chambers 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 protective substrate 30 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 is used. 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 driving circuit 110 for driving the piezoelectric elements 300 arranged in parallel is fixed on the protective substrate 30. As the drive circuit 110, for example, a circuit board, a semiconductor integrated circuit (IC), or the like can be used. The drive circuit 110 and the lead electrode 90 are electrically connected via a connection wiring 120 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 (for example, a polyphenylene sulfide (PPS) film having a thickness of 6 μm), and the sealing film 41 seals one surface of the reservoir portion 31. It has been stopped. The fixing plate 42 is made of a hard material such as metal (for example, stainless steel (SUS) having a thickness of 30 μm). Since the region of the fixing plate 42 facing the reservoir 100 is an opening 43 that is completely removed in the thickness direction, one surface of the reservoir 100 is sealed only with a flexible sealing film 41. Has been.

  An ink introduction port 44 for supplying ink to the reservoir 100 is formed on the compliance substrate 40 on the outer side of the central portion of the reservoir 100 in the longitudinal direction. Further, the protective substrate 30 is provided with an ink introduction path 35 that allows the ink introduction port 44 and the side wall of the reservoir 100 to communicate with each other.

  In such an ink jet recording head of this embodiment, ink is taken in from an ink introduction port 44 connected to an external ink supply means (not shown), and the interior is filled with ink from the reservoir 100 to the nozzle opening 21. In accordance with the recording signal from, a voltage is applied between each of the lower electrode film 60 and the upper electrode film 80 corresponding to the pressure generating chamber 12, and the elastic film 50, the lower electrode film 60, and the piezoelectric layer 70 are bent and deformed. As a result, the pressure in each pressure generating chamber 12 increases and ink droplets are ejected from the nozzle openings 21.

Hereinafter, a method for manufacturing such an ink jet recording head will be described with reference to FIGS. 4 to 6 are sectional views of the pressure generating chamber 12 in the longitudinal direction. First, as shown in FIG. 4A, a flow path forming substrate 10 made of a silicon single crystal substrate is thermally oxidized in a diffusion furnace at about 1100 ° C., and a silicon dioxide film serving as an elastic film 50 and a protective film 51 on its surface. 52 is formed. Next, as shown in FIG. 4B, a zirconium (Zr) layer is formed on the elastic film 50 (silicon dioxide film 52), and then thermally oxidized in a diffusion furnace at 500 to 1200 ° C., for example, to form zirconium oxide ( An insulator film 55 made of ZrO ₂ ) is formed.

  Next, as shown in FIG. 4C, after forming iridium, platinum or the like over the entire surface of the flow path forming substrate 10, the lower electrode film 60 is formed by patterning into a predetermined shape.

  Then, the piezoelectric layer 70 is formed on the lower electrode film 60. Here, in the present embodiment, a so-called sol-gel is obtained in which a so-called sol in which a metal organic material is dissolved and dispersed in a catalyst is applied, dried, gelled, and further fired at a high temperature to obtain a piezoelectric layer 70 made of a metal oxide. The piezoelectric layer 70 is formed using the method. The method for manufacturing the piezoelectric layer 70 is not limited to the sol-gel method, and for example, a MOD (Metal-Organic Decomposition) method or the like may be used.

  The material of the piezoelectric layer 70 includes Pb, Zr and Ti. In this embodiment, the piezoelectric layer 70 is made of lead zirconate titanate (PZT). In addition, the piezoelectric layer 70 of the present embodiment is formed such that the composition ratio after firing is Pb / (Zr + Ti) = 1.0 to 1.3. That is, the piezoelectric layer 70 contains 30% or less of excess lead. Thus, the leakage current is prevented from increasing by containing 30% or less of excess lead. Furthermore, by adding at least one additive selected from manganese (Mn), nickel (Ni), and strontium (Sr) to the piezoelectric layer 70, the piezoelectric layer having excellent electrical resistivity and withstand voltage. 70 can be formed. If the amount of the additive is too large, the displacement amount of the piezoelectric layer 70 is reduced. Therefore, the additive amount is preferably 10 mol% or less with respect to the entire piezoelectric layer 70. Such additives such as manganese, nickel and strontium can be added by mixing manganese nitrate, nickel nitrate and strontium nitrate into the sol. Further, the added additive will be described later in detail, but is also present in the piezoelectric layer 70 formed by firing.

  As a specific procedure for forming the piezoelectric layer 70, first, as shown in FIG. 5A, a piezoelectric precursor film 71 that is a PZT precursor is formed on the lower electrode film 60. That is, a sol (solution) containing a metal organic compound is applied onto the flow path forming substrate 10 on which the lower electrode film 60 is formed (application process).

  Next, the piezoelectric precursor film 71 is heated to a predetermined temperature and dried for a predetermined time. For example, in the present embodiment, the piezoelectric precursor film 71 can be dried by holding at 170 to 180 ° C. for 8 to 30 minutes. Moreover, 0.5-1.5 degreeC / sec is suitable for the temperature increase rate in a drying process. The “temperature increase rate” referred to here is the time from the temperature at which the temperature difference between the temperature at the start of heating (room temperature) and the attained temperature increases by 20% to the temperature at which the temperature difference reaches 80%. It is defined as the rate of change. For example, when the temperature is raised from room temperature 25 ° C. to 100 ° C. in 50 seconds, the rate of temperature rise is (100−25) × (0.8−0.2) /50=0.9 [° C./sec]. Become.

Next, the dried piezoelectric precursor film 71 is degreased by heating it to a predetermined temperature and holding it for a predetermined time. For example, in this embodiment, the piezoelectric precursor film 71 is degreased by heating to a temperature of about 300 to 400 ° C. and holding for about 10 to 30 minutes. 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. In the degreasing step, it is preferable that the temperature rising rate is 0.5 to 1.5 ° C./sec.

  Next, as shown in FIG. 5B, the piezoelectric precursor film 71 is crystallized by being heated to a predetermined temperature and held for a predetermined time to form a piezoelectric film 72 (firing step). In the firing step, the piezoelectric precursor film 71 is preferably heated to 650 to 750 ° C. In this embodiment, the piezoelectric precursor film 71 is heated at 680 ° C. for 30 minutes. In the firing step, it is preferable that the temperature rising rate is 15 ° C./sec or less. Thus, when the piezoelectric film 72 is formed by firing, it is preferable to heat the piezoelectric precursor film 71 for 30 minutes or more. Thereby, the piezoelectric film 72 having excellent characteristics can be obtained.

  In addition, as a heating apparatus used in such a drying process, a degreasing process, and a baking process, for example, a hot plate, an RTP (Rapid Thermal Processing) apparatus that heats by irradiation with an infrared lamp, or the like can be used.

  Then, the piezoelectric film forming process including the coating process, the drying process, the degreasing process, and the baking process described above is repeated a plurality of times, 10 times in this embodiment, so that 10 layers of piezoelectric bodies are obtained as shown in FIG. A piezoelectric layer 70 having a predetermined thickness made of the film 72 is formed. For example, when the film thickness per sol is about 0.1 μm, the film thickness of the entire piezoelectric layer 70 is about 1.1 μm.

  In practice, the first and second piezoelectric films 72 are formed by firing, and after the third and subsequent layers, the coating process, the drying process, and the degreasing process are performed twice. It is formed by firing two layers at a time. That is, the piezoelectric layer 70 composed of the ten piezoelectric films 72 can be formed by firing six times. The total firing time of the piezoelectric layer 70 is preferably 3 hours or less. Thereby, the piezoelectric layer 70 having excellent characteristics can be formed.

  Here, in the manufacturing method described above, the withstand voltage, the relative dielectric constant, and the electrical resistivity when the additive amount was changed were measured. The results are shown in Table 1 below.

  As shown in Table 1, by forming the piezoelectric layer 70 by adding an additive, the piezoelectric layer 70 is formed with an electric resistivity of 20 MΩ · cm or more and a withstand voltage of 900 kV / cm or more. Thus, the durable life of the piezoelectric layer 70 can be extended. Even if an additive is added, the dielectric constant of the piezoelectric layer 70 can be set to 750 to 1500, and the crystallinity of the piezoelectric layer 70 can be greatly improved. Therefore, the durability life can be extended.

Further, the leakage current of the piezoelectric layer 70 can be formed at 1 × 10 ⁻⁸ A / cm ² or less by the method for manufacturing the piezoelectric layer 70 of the present embodiment. By using the leakage current of the piezoelectric layer 70 in this way, the durability life of the piezoelectric layer 70 can be extended.

Further, when the piezoelectric layer 70 is formed under the conditions of this embodiment, the coercive electric field Ec of the piezoelectric layer 70 is approximately 15 to 30 kV / cm and the remanent polarization strength Pr is approximately 10 to 25 μC / cm ^2. .

  Then, after the piezoelectric layer 70 is formed by the steps shown in FIGS. 5A to 5C, the upper electrode film 80 made of, for example, iridium is formed as a flow path as shown in FIG. 6A. The piezoelectric element 300 is formed by patterning the piezoelectric layer 70 and the upper electrode film 80 on the entire surface of the substrate 10 in regions facing the pressure generating chambers 12.

The piezoelectric constant d ₃₁ of the piezoelectric layer 70 thus formed is as high as 150 to 250 (pC / N) as described above, and the displacement characteristics of the piezoelectric element 300 are greatly improved. Thereby, ink discharge characteristics can be improved.

  Next, the lead electrode 90 is formed. Specifically, as shown in FIG. 6B, after forming the lead electrode 90 made of, for example, gold (Au) over the entire surface of the flow path forming substrate 10, for example, a mask pattern made of resist or the like. It is formed by patterning each piezoelectric element 300 via (not shown).

  Next, as shown in FIG. 6C, the protective substrate 30 that holds the plurality of patterned piezoelectric elements 300 is bonded onto the flow path forming substrate 10 with, for example, an adhesive 34. The protective substrate 30 is preliminarily formed with a reservoir portion 31, a piezoelectric element holding portion 32, and the like. Further, the protective substrate 30 is made of, for example, a silicon single crystal substrate having a thickness of about 400 μm, and the rigidity of the flow path forming substrate 10 is remarkably improved by bonding the protective substrate 30.

  Next, as shown in FIG. 6D, the protective film 51 is formed by patterning the silicon dioxide film 52 on the opposite side of the surface on which the piezoelectric element 300 of the flow path forming substrate 10 is formed into a predetermined shape. Then, the flow path forming substrate 10 is anisotropically etched (wet etching) using an alkaline solution such as KOH by using the protective film 51 as a mask, whereby the pressure generating chamber 12, the communication portion 13, and the ink supply are supplied to the flow path forming substrate 10. A path 14 and the like are formed.

  Thereafter, the nozzle plate 20 having the nozzle openings 21 formed on the surface of the flow path forming substrate 10 opposite to the protective substrate 30 is bonded, and the compliance substrate 40 is bonded to the protective substrate 30, so that FIG. An ink jet recording head as shown in FIG.

  In practice, a large number of chips are simultaneously formed on a single wafer by the above-described series of film formation and anisotropic etching, and after the process is completed, a single chip-sized flow path is formed as shown in FIG. An ink jet recording head is formed by dividing each substrate 10.

As described above, in the present invention, the electrical resistivity of the piezoelectric layer 70 constituting the piezoelectric element 300 is set to 20 MΩ · cm or more. As a result, the piezoelectric constant d ₃₁ of the piezoelectric layer 70 is increased, so that the displacement characteristics of the piezoelectric element 300 are improved. Further, by improving the crystallinity of the piezoelectric layer 70, for example, the withstand voltage can be set to 900 kV / cm or more, and the leakage current can be set to 1 × 10 ⁻⁸ A / cm ² or less. Durability life can be greatly extended.

  Here, an endurance test in which a predetermined drive pulse is continuously applied 30 billion times to a sample of a piezoelectric element having a piezoelectric layer having the above-described characteristics is performed, and changes in displacement amount and displacement reduction rate of the piezoelectric element at that time are performed. FIG. 7 shows the result of examination. The sample piezoelectric element has a piezoelectric layer thickness of 1.5 μm, a lower electrode film thickness of 200 nm, and an upper electrode film thickness of 50 nm. The drive pulse applied in the durability test is a sin waveform with a voltage of 50 V and a frequency of 100 kHz, and the drive pulse applied at the time of displacement measurement is a trapezoidal waveform with a voltage of 30 V and a frequency of 800 Hz.

  As shown in FIG. 7, the piezoelectric element according to the present invention has a displacement amount that decreases with an increase in the number of endurance pulses, that is, the displacement decrease rate increases, but even after the drive pulse is applied 30 billion times, The rate of decrease was very low at 13.3%. As is apparent from this result, according to the present invention, the durable life of the piezoelectric element (piezoelectric layer) is significantly improved.

(Other embodiments)
The first embodiment of the present invention has been described above, but the basic configuration of the ink jet recording head is not limited to that described above. For example, in the first embodiment described above, the piezoelectric layer is formed by the sol-gel method or the MOD method. However, the present invention is not particularly limited thereto. For example, the piezoelectric layer may be formed by a sputtering method. When the piezoelectric layer is thus formed by sputtering, the piezoelectric precursor film may be post-annealed at 650 to 750 ° C. for 0.5 to 3 hours.

  In Embodiment 1 described above, at least one additive selected from nickel (Ni), manganese (Mn), and strontium (Sr) is added to the piezoelectric layer 70 constituting the piezoelectric element 300 of the present invention. However, the present invention is not limited to this, and the piezoelectric layer 70 having desired characteristics can be obtained without adding nickel (Ni), manganese (Mn), strontium (Sr), or the like to the piezoelectric layer 70. Can do.

  In addition, the ink jet recording heads of these embodiments constitute a part of a recording head unit having an ink flow path communicating with an ink cartridge or the like, and are mounted on the ink jet recording apparatus. FIG. 6 is a schematic configuration diagram illustrating an example of the ink jet recording apparatus.

  As shown in FIG. 8, in the recording head units 1A and 1B having the ink jet recording head, cartridges 2A and 2B constituting ink supply means are detachably provided, and a carriage 3 on which the recording head units 1A and 1B are mounted. Is provided on a carriage shaft 5 attached to the apparatus 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, which is a recording medium such as paper fed by a paper feed roller (not shown), is conveyed on the platen 8. It is like that.

  In the first embodiment described above, an ink jet recording head has been described as an example of a liquid ejecting head. However, the present invention is widely intended for all liquid ejecting heads, and is a liquid ejecting a liquid other than ink. Of course, the present invention can also be applied to an ejection head. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used for manufacturing color filters such as liquid crystal displays, organic EL displays, and FEDs (surface emitting 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.

FIG. 2 is an exploded perspective view illustrating a schematic configuration of the recording head according to the first embodiment. 2A and 2B are a plan view and a cross-sectional view of the recording head according to the first embodiment. It is a figure which shows an example of the hysteresis curve of a piezoelectric material layer. FIG. 4 is a cross-sectional view illustrating the recording head manufacturing method according to the first embodiment. FIG. 4 is a cross-sectional view illustrating the recording head manufacturing method according to the first embodiment. FIG. 4 is a cross-sectional view illustrating the recording head manufacturing method according to the first embodiment. It is a graph which shows the displacement amount and displacement reduction rate of a sample piezoelectric element. 1 is a diagram illustrating a schematic configuration of a recording apparatus according to an embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Flow path formation board | substrate, 12 ... Pressure generating chamber, 13 ... Communication part, 14 ... Ink supply path, 20 ... Nozzle plate, 21 ... Nozzle opening, 30 ... Protection board, 31 ... Reservoir part, 32 ... Piezoelectric element holding part , 40 ... compliance substrate, 60 ... lower electrode film, 70 ... piezoelectric layer, 80 ... upper electrode film, 90 ... lead electrode, 100 ... reservoir, 110 ... drive circuit, 120 ... connection wiring, 300 ... piezoelectric element.

Claims (6)

  A step of forming a lower electrode, and Pb, Zr and Ti are included on the lower electrode, and the composition ratio after firing is Pb / (Zr + Ti) = 1.0 to 1.3 and from manganese, nickel and strontium A piezoelectric precursor film to which at least one additive selected from the group consisting of the above is added is formed, and the piezoelectric precursor film is baked at 650 to 750 ° C. for 0.5 to 3 hours to form a piezoelectric layer. A method of manufacturing a piezoelectric element, comprising: a step of forming; and a step of forming an upper electrode on the piezoelectric layer.   2. The method of manufacturing a piezoelectric element according to claim 1, wherein the piezoelectric precursor film is added with both manganese and strontium.   The step of forming the piezoelectric layer includes a step of preparing the additive so that the amount added is 10 mol% or less, and a step of adding the prepared additive to the piezoelectric precursor. A method for manufacturing a piezoelectric element according to claim 1 or 2.   In the step of forming the piezoelectric layer, the piezoelectric layer is formed by repeatedly performing a piezoelectric layer forming step of forming a piezoelectric layer by firing a plurality of piezoelectric precursor layers. The firing time of the piezoelectric film in the forming step is 0.5 hours or more, and the total firing time of the piezoelectric layer is within 3 hours. A method for manufacturing a piezoelectric element. A step of manufacturing a piezoelectric element by the method for manufacturing a piezoelectric element according to claim 1,
Forming a liquid flow path, and a method of manufacturing a liquid ejecting head. Producing a liquid jet head by the production method according to claim 5;
And a step of electrically connecting a control unit for controlling the liquid ejecting head to the lower electrode and the upper electrode of the piezoelectric element.

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