JP6658296B2 - Discharge drive device, liquid discharge head, liquid discharge unit, device for discharging liquid - Google Patents

Description

  The present invention relates to an ejection driving device, a liquid ejection head, a liquid ejection unit, and an apparatus for ejecting liquid.

  2. Description of the Related Art For a liquid ejection head used as an image recording apparatus or an image forming apparatus such as a printer, a facsimile, a copying machine, etc., a nozzle for ejecting ink droplets, a pressure chamber communicating with the nozzle, a piezoelectric element for pressurizing ink in the pressure chamber, and the like. Are known. Two types of liquid ejection heads have been put into practical use, one using a longitudinal vibration mode actuator and the other using a flexural vibration mode actuator.

  As a method using the flexural vibration mode, for example, a uniform electromechanical conversion film is formed by a film forming technique over the entire surface of a diaphragm, and the electromechanical conversion film is formed into a shape corresponding to a pressure chamber by a lithography method. It is known that an electromechanical transducer is formed so as to be independent of each pressure chamber.

  This electromechanical conversion element includes, for example, a perovskite-type composite oxide having any one of a tetragonal system, an orthorhombic system, and a rhombohedral system in a film forming process (including an unavoidable impurity. ), And is preferentially oriented to any one of the (100) plane, the (001) plane, and the (111) plane, and the degree of orientation is 95% or more.

  However, for example, when the (111) plane is preferentially oriented and the degree of orientation is 95% or more, when the degree of orientation becomes extremely high, the displacement of the electromechanical conversion film with respect to the electric field strength is saturated halfway, and the high electric field strength A problem that a sufficient displacement cannot be obtained below occurs.

  That is, as the case where the amount of displacement is large, there are a case where the amount of displacement is increased due to piezoelectric strain when a voltage is applied to the piezoelectric film, and a case where the amount of displacement is obtained by increasing the strain due to domain rotation. When the (111) plane is completely oriented, the displacement becomes large only when the piezoelectric strain is applied. Therefore, there is almost no portion where the amount of displacement can be obtained by the domain rotation, and the amount of displacement saturates on the way, and a sufficient amount of displacement cannot be obtained.

  In addition, the amount of displacement of the electromechanical conversion film is greatly affected by the film stress and bending stiffness of the diaphragm. If the film stress and bending stiffness of the diaphragm are not appropriate, it becomes difficult to ensure the discharge performance particularly at high frequencies. . In this regard, for example, a diaphragm is formed by laminating three or more films including a film having a compressive stress and a film having a tensile stress, and a silicon nitride film is included as a film having a tensile stress. (See, for example, Patent Document 1). However, in this film configuration, since the tensile stress is too large, it is not possible to perform a sufficient discharge particularly at a high frequency.

  The present invention has been made in view of the above, and an object of the present invention is to provide a discharge driving device capable of ensuring high-frequency discharge performance.

The present ejection driving device is an ejection driving device in which an electromechanical transducer is formed on a vibration plate, wherein the vibration plate is formed of a laminated film including at least one single-layer film having a compressive stress, The flexural rigidity of the plate is required to be 2.0 × 10 ⁻¹¹ Nm ² or more, and the stress of each single-layer film constituting the diaphragm is required to be 600 MPa or less.

  According to the disclosed technology, it is possible to provide a discharge driving device capable of ensuring high-frequency discharge performance.

FIG. 2 is a cross-sectional view (part 1) illustrating the liquid ejection head according to the first embodiment. FIG. 5 is a cross-sectional view illustrating a manufacturing process of the liquid ejection head according to the first embodiment. FIG. 3 is a cross-sectional view (part 2) illustrating the liquid ejection head according to the first embodiment. FIG. 3 is a diagram illustrating wiring and the like of the liquid ejection head according to the first embodiment. It is a figure which illustrates the schematic structure of a polarization processing apparatus. It is a figure explaining corona discharge. It is a figure which illustrates about a PE hysteresis loop. It is a principal part plane explanatory view of an example of the device which discharges the liquid concerning a 2nd embodiment. It is principal part side explanatory drawing of an example of the apparatus which discharges the liquid which concerns on 2nd Embodiment. FIG. 14 is an explanatory plan view of a main part of another example of the liquid ejection unit according to the second embodiment. FIG. 13 is an explanatory front view of still another example of the liquid ejection unit according to the second embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
FIG. 1 is a cross-sectional view illustrating a liquid ejection head according to the first embodiment. Referring to FIG. 1, the liquid ejection head 1 includes a substrate 10, a vibration plate 20, an electromechanical transducer 30, and an insulating protective film 40. The electromechanical conversion element 30 has a lower electrode 31, an electromechanical conversion film 32, and an upper electrode 33. In the liquid ejection head 1, a portion where the electromechanical transducer 30 is formed on the vibration plate 20 is the ejection driving device 35.

  In the liquid ejection head 1, the vibration plate 20 is formed on the substrate 10, and the lower electrode 31 of the electromechanical transducer 30 is formed on the vibration plate 20. An electromechanical conversion film 32 is formed in a predetermined region of the lower electrode 31, and an upper electrode 33 is formed on the electromechanical conversion film 32. The insulating protective film 40 covers the electromechanical transducer 30. The insulating protective film 40 has an opening for selectively exposing the lower electrode 31 and the upper electrode 33, and wiring can be routed from the lower electrode 31 and the upper electrode 33 through the opening.

  A nozzle plate 50 having nozzles 51 for ejecting ink droplets is joined to a lower portion of the substrate 10. A pressure chamber 10x (also referred to as an ink flow path, a pressurized liquid chamber, a pressurized chamber, a discharge chamber, a liquid chamber, or the like) communicating with the nozzle 51 is formed by the nozzle plate 50, the substrate 10, and the vibration plate 20. Is formed. The vibration plate 20 forms a part of the wall surface of the ink flow path. In other words, the pressure chamber 10x is partitioned by the substrate 10 (constituting the side surface), the nozzle plate 50 (constituting the lower surface), and the diaphragm 20 (constituting the upper surface), and communicates with the nozzle 51.

  To manufacture the liquid discharge head 1, first, as shown in FIG. 2, a vibration plate 20, a lower electrode 31, an electromechanical conversion film 32, and an upper electrode 33 are sequentially stacked on a substrate 10. After that, the lower electrode 31, the electromechanical conversion film 32, and the upper electrode 33 are etched into a desired shape, and covered with an insulating protective film 40. Then, an opening for selectively exposing the lower electrode 31 and the upper electrode 33 is formed in the insulating protective film 40. Thereafter, the pressure chamber 10x is formed by etching the substrate 10 from below. Next, the nozzle plate 50 having the nozzles 51 is joined to the lower surface of the substrate 10 to complete the liquid ejection head 1.

  Although FIG. 1 shows the liquid ejection head 1 having the ejection drive device 35 in which one electromechanical transducer 30 is formed on the vibration plate 20, in practice, as shown in FIG. A liquid ejection head 2 in which a plurality of ejection heads 1 are arranged in a predetermined direction is manufactured.

  The liquid discharge head 2 includes a discharge driving device 35 in which a plurality of electromechanical transducers 30 are arranged on the vibration plate 20, and a nozzle 51 that discharges a liquid and is provided corresponding to each electromechanical transducer 30. , A pressure chamber 10x with which the nozzle 51 communicates. In the liquid ejection head 2, a part of the wall of the pressure chamber 10x is formed by the vibration plate 20, and the ejection driving device 35 pressurizes the liquid in the pressure chamber 10x.

  By the way, when ink is ejected, residual vibration is generated, so that it is necessary to prepare a waveform for suppressing the residual vibration. Since the frequency of the waveform for suppressing the generation of the residual vibration is low, it is difficult to ensure the ejection performance at a high frequency.

  For this reason, in order to ensure the discharge performance at high frequencies, it is necessary to increase the rigidity of the diaphragm 20, the electromechanical conversion film 32, and the insulating protective film 40. Need to be done.

In particular, the characteristics of the diaphragm 20 are important. The vibration plate 20 is composed of a laminated film in which a plurality of single-layer films are laminated. In consideration of stress design, a silicon oxide film (SiO ₂ ), a silicon nitride film (SiN), a polysilicon (Poly-Si), or the like is used. It is preferable to form from a laminated film including a single-layer film made of a material. At this time, the bending rigidity of the diaphragm 20 needs to be 2.0 × 10 ⁻¹¹ Nm ² or more. If the flexural rigidity of the diaphragm 20 is less than 2.0 × 10 ⁻¹¹ Nm ² , it is not possible to ensure high-frequency discharge performance.

  Further, it is preferable that the diaphragm 20 is formed to have a thickness of 1 μm or more and 3 μm or less. This makes it easy to provide rigidity for ensuring high-frequency discharge performance.

  The bending stiffness depends not only on the Young's modulus of the material of the diaphragm 20 but also on the shape of the pressure chamber 10x, but it is preferable to configure the diaphragm 20 to have a length of 600 μm to 1500 μm in the longitudinal direction. If this range is not satisfied, there is a possibility that stable ejection performance at high frequencies cannot be ensured, and if the film thickness is sufficiently large, problems such as cracks may occur during the production of the pressure chamber 10x.

  The stress of the diaphragm 20 can be calculated by forming a single-layer film on the substrate 10 made of Si or the like and evaluating the amount of warpage before and after the film formation. In the diaphragm 20, it is preferable to design the stress so as to be convex upward when the amount of warpage of the substrate 10 immediately after laminating all the single-layer films constituting the diaphragm 20 on the substrate 10 is observed. That is, in the diaphragm 20, it is preferable to select the material of each single layer film so that the diaphragm 20 has a compressive stress as a whole.

  This is because many of the materials used for the electromechanical conversion film 32 and the lower electrode 31 have tensile stress. For example, when a PZT film is used as the electromechanical conversion film 32 or when a Pt film is used as the lower electrode, the PZT film or the Pt film has a tensile stress. Therefore, by adopting a configuration in which the diaphragm 20 has a compressive stress so as to cancel this, a good quality can be obtained as the characteristics of the actuator.

  The diaphragm 20 is formed from a laminated film including at least one single-layer film having a compressive stress. That is, the diaphragm 20 has a configuration having both a single-layer film having a compressive stress and a single-layer film having a tensile stress, or a configuration having only a compressive stress.

  In the diaphragm 20, the film stress of all the single-layer films (both on the tension side and the compression side) needs to be 600 MPa or less, and preferably 400 MPa or less. If the film stress of any one of the single-layer films is larger than 600 MPa, cracks and the like are produced during the production of a thick film, so that a sufficient thickness cannot be obtained by a single film formation, and the process tact is deteriorated.

  If the film stress of any single-layer film is larger than 600 MPa, the film stress of the entire diaphragm 20 cannot be properly adjusted. For example, when the film stress of any single-layer film in the tensile direction is larger than 600 MPa, it is difficult to control the diaphragm 20 so as to be compressed as the entire stress.

  When a material such as SiN having a high tensile stress and a high Young's modulus is selected, the stress can be relaxed by cutting the Si—N bond by ion implantation.

When a material having a high compressive stress and a high Young's modulus, such as Poly-Si, is selected, the surface can be roughened by ion implantation, and the crystal state can be partially made amorphous, so that the stress can be relaxed. It is preferable that the ion implantation amount is 1 × 10 ¹⁴ ions / cm ² or more. If the value exceeds this, the effect of the stress relaxation is saturated.

  The element used for ion implantation may be basically any element other than the constituent elements. Any kind of ion implantation such as boron, phosphorus, arsenic, germanium, and argon used in a general semiconductor process may be used, and is not limited to the above elements.

The film having the highest Young's modulus among the laminated films forming the diaphragm 20 may be subjected to ion implantation with an element other than the constituent elements to adjust the stress. Further, the diaphragm 20 includes a first film made of SiO ₂ , a _second film made of SiN, and a third film made of Poly-Si, and among the first film, the second film, and the third film, Any of the films may be ion-implanted with an element other than the constituent elements to adjust the stress.

Further, in order to secure the bending stiffness of 2.0 × 10 ⁻¹¹ Nm ² or more, in consideration of the process tact, when trying to realize a film as thin as possible, the Young's modulus of the laminated film constituting the diaphragm 20 is the lowest. The large single layer film preferably has a Young's modulus of 150 GPa or more, and preferably 200 GPa or more. Further, it is preferable that the equivalent Young's modulus of the laminated film forming the diaphragm 20 be 75 GPa or more.

As described above, in the ejection driving device 35 according to the present embodiment, the diaphragm 20 is formed of a laminated film including at least one single-layer film having a compressive stress, and the bending rigidity of the diaphragm 20 is 2.0 × 10 ⁻¹¹ Nm ² or more, and the stress of each single-layer film constituting the diaphragm 20 is 600 MPa or less.

  This makes it possible to sufficiently secure a displacement amount capable of stably ejecting the liquid at a high frequency. In addition, since the deterioration of the displacement amount can be sufficiently suppressed even when the liquid is continuously discharged, stable liquid discharge characteristics can be obtained.

  Further, when the stress of the single-layer film constituting the diaphragm 20 is 600 MPa or less, cracks and the like hardly occur at the time of film formation, so that a sufficient thickness can be obtained by one film formation, and the process tact time is reduced. Deterioration can be prevented.

  Hereinafter, suitable materials for forming the liquid ejection head 2 will be described in more detail. As the substrate 10, a silicon single crystal substrate is preferably used, and usually preferably has a thickness of 100 to 600 μm. There are three types of plane orientations, (100), (110), and (111). In the semiconductor industry, generally, (100) and (111) are widely used. A single crystal substrate having a (100) plane orientation can be used.

  Further, when manufacturing the pressure chamber 10x, the silicon single crystal substrate is processed by using etching. In this case, it is preferable to use anisotropic etching. Note that the anisotropic etching utilizes a property that an etching rate is different from a plane orientation of a crystal structure.

For example, in anisotropic etching immersed in an alkaline solution such as KOH, the (111) plane has an etching rate of about 1/400 compared to the (100) plane. Therefore, a structure having an inclination of about 54 ° can be manufactured in the plane orientation (100), while a deep groove can be dug in the plane orientation (110). Therefore, since the arrangement density can be increased while maintaining the rigidity, the liquid discharge head 2 may use a single crystal substrate having the (110) plane orientation. However, in this case, it should be noted that SiO _{2 as the} mask material is also etched.

  Further, the width (length in the lateral direction) of the pressure chamber 10x is preferably 50 μm or more and 70 μm or less, and more preferably 55 μm or more and 65 μm or less. If the value is larger than this value, the residual vibration becomes large and it becomes difficult to secure the discharge performance at a high frequency. If the value is smaller than this value, the amount of displacement of the electromechanical transducer decreases, and a sufficient discharge voltage cannot be secured.

The vibration plate 20 is deformed and displaced by receiving the force generated by the electromechanical conversion film 32, and ejects ink droplets in the pressure chamber 10x. Therefore, it is preferable that the diaphragm 20 has a predetermined strength. Specifically, a material prepared from Si, SiO ₂ , Si ₃ N _4, or the like by a CVD method or the like can be given.

  Further, as the material of the diaphragm 20, it is preferable to select a material having a linear expansion coefficient close to that of the lower electrode 31 and the electromechanical conversion film 32.

In particular, when using PZT as an electromechanical conversion film 32, as the material of the diaphragm 20, 5 × ¹⁰ -6 close to the linear expansion coefficient of ^{PZT 8 × 10 -6 (1 /} K) (1 / K) It is preferable to select a material having a linear expansion coefficient of about 〜１０10 × 10 ⁻⁶ (1 / K). It is further preferable to select a material having a linear expansion coefficient of about 7 × 10 ⁻⁶ (1 / K) to 9 × 10 ⁻⁶ (1 / K).

  As a material of the diaphragm 20, aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, a compound thereof, or the like may be used. These can be produced by a spin coater using a sputtering method or a Sol-gel method.

  The thickness of the diaphragm 20 is preferably 1 to 3 μm, more preferably 1.5 to 2.5 μm. If it is smaller than this range, it becomes difficult to process the pressure chamber 10x, and if it is larger than this range, it becomes difficult to deform and displace, and the ejection of ink droplets becomes unstable.

  As the lower electrode 31 and the upper electrode 33, platinum having high heat resistance and low reactivity can be used as a metal material. However, platinum may not be said to have sufficient barrier properties against lead, and in that case, a platinum group element such as iridium or platinum-rhodium, or an alloy film of these can be used. .

When platinum is used for the lower electrode 31 and the upper electrode 33, Ti, TiO ₂ , Ta, Ta ₂ O ₅ , and Ta are used because of poor adhesion to the diaphragm 20 (especially, SiO ₂ ) as a base. it is preferable to laminate via an adhesive layer, such as ₃ N _5. As a method for forming the lower electrode 31 and the upper electrode 33, a vacuum film formation such as a sputtering method or a vacuum deposition can be used. The thickness of the lower electrode 31 and the upper electrode 33 is preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm.

Furthermore, in the lower electrode 31 and the upper electrode 33, an oxide electrode film made of SrRuO ₃ or LaNiO ₃ may be formed between the metal material and the electromechanical conversion film 32. Note that the oxide electrode film between the lower electrode 31 and the electromechanical conversion film 32 affects the alignment control of the electromechanical conversion film 32 (for example, a PZT film) formed thereon. The material selected depends on the orientation.

In the liquid ejection head 2, when PZT is used as the electromechanical conversion film 32 and PZT (100) is preferentially oriented, a seed layer made of LaNiO ₃ , TiO ₂ , PbTiO ₃ or the like is formed on the lower electrode 31. Preferably, a PZT film is formed on the seed layer. In particular, by using PbTiO ₃ (lead titanate), it is possible to form a PZT film having excellent crystallinity preferentially oriented to PZT (100).

  Further, an SRO film can be used as an oxide electrode film between the upper electrode 33 and the electromechanical conversion film 32, and the thickness of the SRO film is preferably 20 nm to 80 nm, more preferably 30 nm to 50 nm. If the thickness is smaller than this range, sufficient initial displacement and displacement deterioration characteristics cannot be obtained. If it exceeds this range, the dielectric breakdown voltage of PZT is very poor, and leakage tends to occur.

As the electromechanical conversion film 32, lead zirconate titanate (PZT) can be preferably used. PZT is a solid solution of lead zirconate (PbZrO ₃ ) and lead titanate (PbTiO ₃ ), and the characteristics of PZT differ depending on the ratio between PbZrO ₃ and PbTiO ₃ . For example, the ratio of PbZrO ₃ to PbTiO ₃ is 53:47, and Pb (Zr _0.53 , Ti _0.47 ) O ₃ when represented by a chemical formula, PZT generally represented as PZT (53/47), etc. Can be used.

  The electromechanical conversion film 32 can be formed by a spin coater using a sputtering method or a Sol-gel method. In that case, since patterning is required, a desired pattern can be obtained by photolithography etching or the like.

  When producing PZT by the Sol-gel method, first, a lead acetate, a zirconium alkoxide, or a titanium alkoxide compound is used as a starting material. Then, a PZT precursor solution can be prepared by dissolving in methoxyethanol as a common solvent to obtain a uniform solution. Since the metal alkoxide compound is easily hydrolyzed by atmospheric moisture, an appropriate amount of acetylacetone, acetic acid, diethanolamine or the like may be added as a stabilizer to the PZT precursor solution.

  When a PZT film is formed on the entire surface of the lower electrode 31, it is obtained by forming a coating film by a solution coating method such as spin coating and performing each of heat treatments of solvent drying, thermal decomposition, and crystallization. Since the transformation from a coating film to a crystallized film involves volume shrinkage, it is necessary to adjust the concentration of the PZT precursor so as to obtain a film thickness of 100 nm or less in a single step in order to obtain a crack-free film. .

  The thickness of the electromechanical conversion film 32 is preferably 1 μm or more and 3 μm or less, and more preferably 1.5 μm or more and 2.5 μm or less. If it is smaller than this range, it becomes difficult to process the pressure chamber 10x, and if it is larger than this range, it becomes difficult to deform and displace, and the ejection of ink droplets becomes unstable.

  When PZT is used as the electromechanical conversion film 32 and the PZT (100) plane is preferentially oriented, the composition ratio of Zr / Ti is such that the composition ratio Ti / (Zr + Ti) is 0.45 or more and 0.55 or less. It is more preferably 0.48 or more and 0.52 or less.

  The crystal orientation is represented by ρ (hkl) = I (hkl) / ΣI (hkl). Here, ρ (hkl) is the degree of orientation in the (hkl) plane orientation, I (hkl) is the peak intensity of an arbitrary orientation, and ΔI (hkl) is the sum of the respective peak intensities. In the arrangement direction of the electromechanical transducers 30, it is calculated based on the ratio of the peak intensities of the respective orientations when the sum of the peak intensities obtained by the θ-2θ measurement by the X-ray diffraction method is set to 1 (100). The average value of the degree of orientation is preferably 0.95 (95%) or more, and more preferably 0.99 (99%) or more. If it is less than 0.95 (95%), sufficient piezoelectric strain cannot be obtained, and the displacement of the electromechanical transducer 30 cannot be sufficiently secured.

As the electromechanical conversion film 32, an ABO ₃ type perovskite type crystalline film other than PZT may be used. As the ABO ₃ type perovskite type crystalline film other than PZT, for example, a lead-free composite oxide film such as barium titanate may be used. In this case, a barium titanate precursor solution can be prepared by using a barium alkoxide or a titanium alkoxide compound as a starting material and dissolving it in a common solvent.

These materials are described by the general formula _{ABO 3, A = Pb, Ba} , Sr B = Ti, Zr, Sn, Ni, Zn, Mg, composite oxide corresponds mainly composed of Nb. As specific description _{(Pb1-x, Ba) (} Zr, Ti) O 3, (Pb1-x, Sr) (Zr, Ti) O 3, expressed as which part of Pb of the A site Ba And Sr. Such substitution is possible if it is a divalent element, and its effect is to reduce the characteristic deterioration due to evaporation of lead during heat treatment.

  Here, the configuration of the liquid ejection head including the wiring and the like will be described. FIGS. 4A and 4B are diagrams illustrating wirings and the like of the liquid discharge head according to the first embodiment. FIG. 4A is a cross-sectional view, and FIG. 4B is a plan view. In FIG. 4B, illustration of the insulating protective films 40 and 70 is omitted.

  Referring to FIG. 4, a plurality of wirings 60 are provided on the insulating protection film 40, and an insulating protection film 70 is provided on the wiring 60. The insulating protective film 40 has a plurality of openings 40x, and the surface of the lower electrode 31 or the upper electrode 33 is exposed in the openings 40x. The wiring 60 fills the opening 40x and is connected to the upper electrode 33 (the portion of the contact hole H in FIG. 4B), and the wiring 60 fills the opening 40x and is connected to the lower electrode 31. And wiring.

  The insulating protective film 70 has a plurality of openings 70x, and the surface of each wiring 60 is exposed in each opening 70x. The respective wires 60 exposed in the respective openings 70x become the electrode pads 61, 62, and 63. Here, the electrode pad 61 is a common electrode pad, and is connected to the lower electrode 31 common to each of the electromechanical transducers 30 via the wiring 60. The electrode pads 62 and 63 are individual electrode pads, and are connected to the upper electrode 33 independent for each electromechanical transducer 30 via the wiring 60.

  Next, the polarization processing device will be described. FIG. 5 is a diagram illustrating a schematic configuration of a polarization processing apparatus. The polarization processing device 500 includes a corona electrode 510 and a grid electrode 520, and the corona electrode 510 and the grid electrode 520 are connected to a corona electrode power supply 511 and a grid electrode power supply 521, respectively. A temperature control function is added to the stage 530 for setting a sample, and a polarization process can be performed while applying a temperature of up to about 350 ° C. The stage 530 is provided with an earth 540, and when this is not added, the polarization process cannot be performed.

  The grid electrode 520 is, for example, subjected to mesh processing, and when a high voltage is applied to the corona electrode 510, ions and charges generated by corona discharge efficiently pour down to the lower stage 530, and the electric machine It is designed to be injected into the conversion film 32. By adjusting the magnitude of the voltage applied to the corona electrode 510 or the grid electrode 520 or the distance between the sample and each electrode, the intensity of the corona discharge can be increased.

  As shown in FIG. 6, when corona discharge is performed using the corona wire 600, molecules 610 in the atmosphere are ionized to generate cations 620. Then, the generated cations 620 flow through the pad portions of the electromechanical transducer 30 to charge the electromechanical transducer 30.

In this case, it is considered that an internal potential difference occurs due to a charge difference between the upper electrode and the lower electrode, and the polarization process is performed. At this time, the charge amount Q required for the polarization process is not particularly limited, but it is preferable that a charge amount of 1.0 × 10 ⁻⁸ C or more is accumulated in the electromechanical conversion element 30. More preferably, a charge amount of 0 × 10 ⁻⁸ C or more is accumulated. When the value is less than this value, the polarization processing cannot be performed sufficiently, and sufficient characteristics of displacement deterioration after continuous driving as a PZT piezoelectric actuator cannot be obtained.

  Here, the state of the polarization processing can be determined from the PE hysteresis loop of the electromechanical transducer 30. A method of determining the polarization processing will be described with reference to FIG. FIG. 7A illustrates the PE hysteresis loop before the polarization processing, and FIG. 7B illustrates the PE hysteresis loop after the polarization processing.

  Specifically, first, as shown in FIG. 7, the hysteresis loop is measured with an electric field strength of ± 150 kv / cm. When the initial polarization at 0 kv / cm is Pind, and when the polarization at 0 kv / cm when the voltage is returned to 0 kv / cm after application of a voltage of +150 kv / cm is Pr, the value of Pr-Pind is the polarization rate. By defining the polarizability, it is possible to judge whether the polarization state is good or bad.

Polarizability Pr-Pind is preferably at 10 [mu] C / cm ² or less, still more preferably 5 [mu] C / cm ² or less. If the polarizability Pr-Pind is larger than this value, sufficient characteristics regarding displacement deterioration after continuous driving as a PZT piezoelectric actuator cannot be obtained.

  In FIG. 5, the desired polarizability Pr-Pind can be obtained by adjusting the voltages of the corona electrode 510 and the grid electrode 520, the distance between the stage 530 and the corona electrode 510 and the grid electrode 520, and the like. However, when trying to obtain a desired polarizability Pr-Pind, it is preferable to generate a high electric field with respect to the electromechanical conversion film 32.

  When the vector component of the spontaneous polarization axis of the electromechanical conversion film 32 matches the electric field application direction, expansion and contraction due to the increase and decrease of the electric field application strength occurs effectively, and a large piezoelectric constant is obtained. Most preferably, the spontaneous polarization axis of the electromechanical conversion film 32 completely coincides with the electric field application direction.

<Second embodiment>
In the second embodiment, as an application example, an apparatus for ejecting liquid provided with a liquid ejection head 2 (see FIG. 3) will be described.

  First, an example of an apparatus for discharging liquid according to the second embodiment will be described with reference to FIGS. FIG. 8 is an explanatory plan view of a main part of the apparatus, and FIG. 9 is an explanatory side view of an essential part of the apparatus.

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

  On the carriage 403, a liquid discharge unit 440 in which the liquid discharge head 2 and the head tank 441 according to the first embodiment are integrated is mounted. The liquid discharge head 2 of the liquid discharge unit 440 discharges, for example, liquid of each color of yellow (Y), cyan (C), magenta (M), and black (K). The liquid ejection head 2 has a nozzle row composed of a plurality of nozzles 51 arranged in a sub-scanning direction orthogonal to the main scanning direction, and is mounted with the ejection direction facing downward.

  The liquid stored in the liquid cartridge 450 is supplied to the head tank 441 by the supply mechanism 494 for supplying the liquid stored outside the liquid discharge head 2 to the liquid discharge head 2.

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

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

  The transport belt 412 attracts the paper 410 and transports it at a position facing the liquid discharge head 2. The transport belt 412 is an endless belt, and is stretched between a transport roller 413 and a tension roller 414. Suction can be performed by electrostatic suction or air suction.

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

  Further, on one side of the carriage 403 in the main scanning direction, a maintenance / recovery mechanism 420 for maintaining and recovering the liquid ejection head 2 is disposed on the side of the transport belt 412.

  The maintenance and recovery mechanism 420 includes, for example, a cap member 421 for capping the nozzle surface (the surface on which the nozzles 51 are formed) of the liquid ejection head 2 and a wiper member 422 for wiping the nozzle surface.

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

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

  Therefore, by driving the liquid discharge head 2 according to the image signal while moving the carriage 403 in the main scanning direction, the liquid is discharged onto the stopped paper 410 to form an image.

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

  Next, another example of the liquid ejection unit according to the second embodiment will be described with reference to FIG. FIG. 10 is an explanatory plan view of a main part of the unit.

  The liquid discharge unit includes a housing portion including side plates 491A and 491B and a back plate 491C, a main scanning moving mechanism 493, a carriage 403, It is composed of a discharge head 2.

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

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

  The liquid discharge unit includes the liquid discharge head 2 to which the flow path component 444 is attached, and a tube 456 connected to the flow path component 444.

  The flow channel component 444 is disposed inside the cover 442. A head tank 441 may be included instead of the flow path component 444. A connector 443 for making an electrical connection with the liquid ejection head 2 is provided above the flow path component 444.

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

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

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

Further, the "device for discharging liquid" is not limited to a device in which a significant image such as a character or a figure is visualized by the discharged liquid. For example, those that form a pattern or the like that has no meaning in itself, and those that form a three-dimensional image are also included.
The above-mentioned "thing to which a liquid can be attached" means a thing to which a liquid can be attached at least temporarily, such as a thing which adheres and adheres, a thing which adheres and penetrates, and the like. Specific examples include recording media such as paper, recording paper, recording paper, film, and cloth; electronic components such as electronic substrates and piezoelectric elements; powder layers (powder layers); organ models; and media such as inspection cells. Yes, unless otherwise specified, all that adhere to the liquid.

  The material of the above-mentioned "things to which liquid can adhere" is a liquid such as paper, yarn, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, building materials such as wallpaper and flooring, and textiles for clothing. However, any material can be used as long as it can be attached.

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

  In addition, the "device for discharging liquid" includes a device in which a liquid discharge head and a device to which liquid can adhere are relatively moved, but are not limited thereto. Specific examples include a serial device that moves the liquid ejection head, a line device that does not move the liquid ejection head, and the like.

  Other examples of the "device for discharging liquid" include a processing liquid coating device for discharging a processing liquid onto a sheet in order to apply the processing liquid to the surface of the paper for the purpose of modifying the surface of the paper, and a raw material. There is an injection granulation apparatus or the like that granulates fine particles of a raw material by spraying a composition liquid in which a composition is dispersed in a solution through a nozzle.

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

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

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

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

  Further, as a liquid discharge unit, there is a liquid discharge head in which a liquid discharge head is movably held by a guide member constituting a part of a scanning moving mechanism, and the liquid discharging head and the scanning moving mechanism are integrated. Further, as shown in FIG. 10, there is a liquid discharge unit in which a liquid discharge head, a carriage, and a main scanning moving mechanism are integrated.

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

  In addition, as shown in FIG. 11, there is a liquid discharge unit in which a tube is connected to a liquid discharge head to which a head tank or a flow path component is attached, and a liquid discharge head and a supply mechanism are integrated. .

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

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

  Further, image forming, recording, printing, printing, printing, modeling, and the like in the terms of the present application are all synonymous.

[Example 1]
A 6-inch silicon wafer is prepared as the substrate 10, and SiO ₂ (thickness: 600 nm), Si (thickness: 200 nm), SiO ₂ (thickness: 100 nm), SiN (thickness: 150 nm), SiO ₂ (thickness: 1300 nm), SiN (150 nm), SiO ₂ (film thickness 100 nm), Si (200 nm), and SiO ₂ (film thickness 600 nm) were formed in this order to produce the diaphragm 20.

At this time, as for the SiN film, the tensile stress of the conventional SiN film was relaxed by implanting boron at 1 × 10 ¹⁵ ions / cm ² . Evaluation of the film stress and rigidity of each single-layer film was performed separately from the laminated film, and some of the results are shown in Table 1 below.

  Thereafter, a titanium film (thickness: 20 nm) was formed as a close contact layer on the vibration plate 20 at a film formation temperature of 350 ° C. by a sputtering apparatus, and then thermally oxidized at 750 ° C. using RTA (rapid heat treatment). Further, a platinum film (160 nm in thickness) was formed on the adhesion layer by a sputtering device at a film formation temperature of 300 ° C. to produce a lower electrode 31.

Next, a solution in which Pb: Ti = 1: 1 is adjusted as a PbTiO ₃ layer serving as a base layer on the lower electrode 31 and a solution in which Pb: Zr: Ti is adjusted to 115: 49: 51 as the electromechanical conversion film 32. Was prepared, and a film was formed by spin coating.

  For the synthesis of a specific precursor coating solution, lead acetate trihydrate, isopropoxide titanium, and isopropoxide zirconium were used as starting materials. The water of crystallization of lead acetate was dissolved in methoxyethanol and then dehydrated. The lead content is excessive relative to the stoichiometric composition. This is to prevent a decrease in crystallinity due to so-called lead loss during the heat treatment.

  Titanium isopropoxide and zirconium isopropoxide were dissolved in methoxyethanol, an alcohol exchange reaction and an esterification reaction were advanced, and a PZT precursor solution was synthesized by mixing with the methoxyethanol solution in which lead acetate was dissolved. This PZT concentration was 0.5 mol / liter. A solution of PT is also prepared in the same manner as PZT, and a PT layer is first formed by spin coating using these solutions, dried at 120 ° C., and then formed by spin coating of the PZT solution. The film was dried at 120 ° C. and then thermally decomposed at 380 ° C.

  After the thermal decomposition treatment of the third layer, a crystallization heat treatment (at a temperature of 730 ° C.) was performed by RTA. At this time, the film thickness of PZT was 240 nm. This process was performed eight times (24 layers) in total, and a PZT film of about 2 μm was obtained as the electromechanical conversion film 32.

Next, an SrRuO ₃ film (film thickness: 40 nm) was formed as an oxide electrode film constituting the upper electrode 33, and a platinum film (film thickness: 125 nm) was formed as a metal film by sputtering. Thereafter, a photoresist (TSMR8800) manufactured by Tokyo Ohkasha Co., Ltd. is formed by spin coating, a resist pattern is formed by ordinary photolithography, and a pattern as shown in FIG. 4 is formed using an ICP etching apparatus (manufactured by Samco). Produced. As a result, the electromechanical transducer 30 was formed on the diaphragm 20.

Next, an Al ₂ O ₃ film having a thickness of 50 nm was formed on the electromechanical transducer 30 as the insulating protective film 40 by using the ALD method. For Al as a raw material At this time, TMA (Sigma-Aldrich), by laminating the O ₃ which is generated by the ozone generator alternately for O, and advances the film formation.

Thereafter, as shown in FIG. 4, a contact hole H was formed by etching. After that, Al was formed by a sputtering method, patterned by etching to form a wiring 60, and Si ₃ N ₄ was formed as an insulating protective film 70 to a thickness of 500 nm by a plasma CVD method. Then, an opening 70x was provided in the insulating protective film 70 to expose a part of the wiring 60 to form electrode pads 61, 62 and 63. The electrode pad 61 is a common electrode pad, the electrode pads 62 and 63 are individual electrode pads, and the distance between the individual electrode pads is 80 μm.

  Thereafter, the polarization treatment was performed by a corona charging treatment using the polarization treatment device 500. For the corona charging treatment, a tungsten wire of φ50 μm is used. The polarization processing conditions include a processing temperature of 80 ° C., a voltage of 9 kV for the corona electrode 510, a voltage of 2.5 kV for the grid electrode 520, a processing time of 30 s, a distance of 4 mm between the corona electrode 510 and the grid electrode 520, and a distance between the grid electrode 520 and the stage 530. At a distance of 4 mm.

  Thereafter, the back surface of the substrate 10 was etched to form a pressure chamber 10x (width 60 μm, depth 1000 μm), and the liquid ejection head 2 was obtained. However, the nozzle plate 50 having the nozzles 51 is not joined to the lower portion of the substrate 10, and the liquid discharge head 2 is in a semi-finished state.

[Example 2]
A liquid discharge head 2 was manufactured in the same manner as in Example 1 except that the vibration plate 20 was formed except for the Si layer.

[Example 3]
A liquid ejection head 2 was manufactured in the same manner as in Example 1 except that boron was implanted into the Si layer at 1 × 10 ¹⁵ ions / cm ² .

[Example 4]
A liquid discharge head 2 was manufactured in the same manner as in Example 1 except that the diaphragm 20 was formed except for the SiN layer.

[Example 5]
Except for the SiN layer, a liquid ejection head 2 was manufactured in the same manner as in Example 1 except that boron was implanted into the Si layer at 1 × 10 ¹⁵ ions / cm ² .

[Comparative Example 1]
A liquid discharge head 2 was manufactured in the same manner as in Example 1 except that a film was formed without injecting boron into the SiN layer at 1 × 10 ¹⁵ ions / cm ² .

[Comparative Example 2]
A liquid ejection head 2 was manufactured in the same manner as in Example 1 except that only a SiO ₂ film (thickness: 600 nm) was formed on a 6-inch silicon wafer.

[Examination of Examples 1 to 5 and Comparative Examples 1 and 2]
With respect to the electromechanical transducer 30 of each of the liquid ejection heads 2 manufactured in Examples 1 to 5 and Comparative Examples 1 and 2, the electrical characteristics and the displacement (piezoelectric constant) of the electromechanical transducer 30 were evaluated.

  As for the amount of displacement, as shown in FIG. 3, the pressure chamber 10x was formed by excavating from the back side of the substrate 10, and evaluation was performed. Specifically, the amount of displacement (piezoelectric constant) due to the application of an electric field (150 kV / cm) was measured by a laser Doppler vibrometer and calculated from the adjustment by simulation. Table 1 shows the evaluation results. In addition, in the maximum film stress of the single-layer film in Table 1, “+” indicates a tensile stress, and “−” indicates a compressive stress.

表１から分かるように、実施例１〜５については、初期特性の結果について一般的なセラミックス焼結体と同等の特性を有していた（圧電定数は−１２０〜−１６０ｐｍ／Ｖ）。比較例１については、若干初期の圧電定数が低く、若干一般的なセラミックス焼結体に比べて特性が劣っていることが分かる。これは、比較例１では、振動板２０が引張方向で６００ＭＰａよりも大きな応力を有する単層膜（＋１３００ＭＰａの単層膜）を含んでいるため、振動板２０全体の膜応力が適切に調整できなかったからである。

As can be seen from Table 1, the results of the initial characteristics of Examples 1 to 5 were equivalent to those of a general ceramic sintered body (the piezoelectric constant was -120 to -160 pm / V). It can be seen from Comparative Example 1 that the initial piezoelectric constant was slightly lower and the characteristics were slightly inferior to those of a general ceramic sintered body. This is because, in Comparative Example 1, since the diaphragm 20 includes a single-layer film having a stress greater than 600 MPa in the tensile direction (a single-layer film of +1300 MPa), the film stress of the entire diaphragm 20 can be appropriately adjusted. Because there was no.

  Further, using the electromechanical transducers 30 manufactured in Examples 1 to 5 and Comparative Examples 1 and 2, the liquid discharge head shown in FIG. 3 was manufactured, and the liquid discharge evaluation was performed. Using the ink whose viscosity was adjusted to 5 cp, the ejection state when an applied voltage of -10 to -30 V was applied was confirmed by a simple Push waveform.

  As a result, as shown in Table 1, it was confirmed that all of Examples 1 to 5 can be ejected from any of the nozzle holes and can be ejected at a high frequency (in Table 1, indicated by a circle). On the other hand, in Comparative Example 1, the voltage required for slightly discharging was almost at the upper limit (indicated by Δ in Table 1), and in Comparative Example 2, ink could not be discharged stably when trying to discharge at high frequency (Table 1). In the case of 1, it is indicated by x).

In Comparative Example 2, ink could not be stably ejected at a high frequency because, in Comparative Example 2, the diaphragm was formed from only one layer of film, and the flexural rigidity of the diaphragm was 2.0 × 10 ^This is because it was less than ⁻¹¹ Nm ² and the bending rigidity was insufficient.

  As described above, the preferred embodiments and the like have been described in detail. However, the present invention is not limited to the above-described embodiments and the like, and various modifications may be made to the above-described embodiments and the like without departing from the scope described in the claims. Variations and substitutions can be made.

  For example, in the above embodiment, the case where the upper electrode is an individual electrode and the lower electrode is a common electrode has been described, but the present invention is not limited to this. That is, the same effect can be obtained in a configuration in which the upper electrode is a common electrode and the lower electrode is an individual electrode.

1, 2 Liquid discharge head 10 Substrate 10x Pressure chamber 20 Vibration plate 30 Electromechanical conversion element 31 Lower electrode 32 Electromechanical conversion film 33 Upper electrode 35 Discharge drive device 40, 70 Insulation protection film 40x, 70x Opening 50 Nozzle plate 51 Nozzle 60 Wiring 61, 62, 63 Electrode pad 401 Guide member 403 Carriage 405 Main scanning motor 406 Driving pulley 407 Driven pulley 408 Timing belt 410 Paper 412 Conveying belt 413 Conveying roller 414 Tension roller 416 Sub-scanning motor 417 Timing belt 418 Timing pulley 420 Maintaining Recovery mechanism 421 Cap member 422 Wiper member 440 Liquid ejection unit 441 Head tank 442 Cover 443 Connector 444 Flow path component 450 Liquid cartridge 451 Cartridge holder 452 liquid-feeding unit 456 tubes 491A, 491B plate 491C backplate 493 main scan movement mechanism 494 supplying mechanism 495 transporting mechanism

Patent No. 5618208

Claims (12)

An ejection drive device in which an electromechanical conversion element is formed on a diaphragm,
The diaphragm is formed from a laminated film including at least one single-layer film having a compressive stress,
The diaphragm has a flexural rigidity of 2.0 × 10 ⁻¹¹ Nm ² or more,
The single-layer film constituting the diaphragm has a stress of 600 MPa or less.   2. The ejection driving device according to claim 1, wherein a Young's modulus of a film having the highest Young's modulus among the stacked films is 150 GPa or more. 3.   3. The ejection driving device according to claim 2, wherein the film having the largest Young's modulus is ion-implanted with an element other than a constituent element. The laminated film includes a first film made of SiO ₂ , a _second film made of SiN, and a third film made of Poly-Si,
4. The method according to claim 1, wherein any one of the first film, the second film, and the third film is ion-implanted with an element other than a constituent element. The ejection drive device according to any one of the preceding claims.   5. The discharge driving device according to claim 1, wherein an equivalent Young's modulus of the laminated film is 75 GPa or more. 6.   The ejection driving device according to claim 1, wherein a thickness of the diaphragm is 1 μm or more and 3 μm or less. The electromechanical conversion element has a structure in which a lower electrode, an electromechanical conversion film, and an upper electrode are sequentially stacked,
The discharge driving device according to any one of claims 1 to 6, wherein a seed layer made of lead titanate is formed between the lower electrode and the electromechanical conversion film. The electromechanical conversion element has a structure in which a lower electrode, an electromechanical conversion film, and an upper electrode are sequentially stacked,
A plurality of the electromechanical transducers are arranged on the diaphragm,
8. The ejection driving device according to claim 1, wherein in the arrangement direction, the average value of the degree of orientation of the (100) orientation of the electromechanical conversion film is 95% or more. 9. An ejection drive device according to any one of claims 1 to 8,
Provided corresponding to the electromechanical transducer, a nozzle for discharging liquid, and a pressurized chamber with which the nozzle communicates,
A part of the wall of the pressurizing chamber is constituted by the diaphragm,
A liquid discharge head, wherein the discharge drive device pressurizes the liquid in the pressurized chamber.   A liquid discharge unit comprising the liquid discharge head according to claim 9.   A head tank for storing liquid to be supplied to the liquid discharge head, a carriage on which the liquid discharge head is mounted, a supply mechanism for supplying liquid to the liquid discharge head, a maintenance and recovery mechanism for maintaining and recovering the liquid discharge head, and the liquid The liquid ejection unit according to claim 10, wherein at least one of a main scanning movement mechanism for moving the ejection head in the main scanning direction and the liquid ejection head are integrated.   An apparatus for discharging liquid, comprising the liquid discharge head according to claim 9 or the liquid discharge unit according to claim 10 or 11.

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