JP2014151511A - Method for manufacturing liquid droplet discharge head, liquid discharge head and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing at a reduced production cost a liquid droplet discharge head having a curved electromechanical conversion element.SOLUTION: A method for manufacturing a liquid droplet discharge head performs: a vibrating plate formation step of forming a vibrating plate 15 on a substrate 16; an electromechanical conversion element formation step that forms an electromechanical conversion element 14 by forming sequentially respective materials of a lower electrode layer 14b, an electromechanical conversion layer 14a and an upper electrode layer 14c constituting the electromechanical conversion element 14 on the vibrating plate 15 and heating and burning for every formation of each layer; a pressurized-liquid chamber formation step that forms a pressurized-liquid chamber so that the vibrating plate 15 constitutes a part of the pressurized-liquid chamber at a position of the substrate 16 opposing to the electromechanical conversion element 14 across the vibrating plate 15; and a nozzle plate jointing step that joints a nozzle plate 12 having a nozzle 11 formed therein to an end portion opposite to a portion contacting the vibrating plate 15 of a bulkhead partitioning the pressurized-liquid chamber.

Description

  The present invention relates to a method for manufacturing a droplet discharge head using a piezoelectric actuator in a flexural vibration mode, a liquid discharge head, and an image forming apparatus.

  Generally, as an image forming apparatus that combines a printer, a fax machine, a copier, a plotter, or a plurality of these functions, for example, there is an ink jet recording apparatus that includes a liquid ejection head that ejects ink droplets. In this inkjet recording apparatus, image formation is performed by adhering ink droplets to a sheet while conveying a medium. The medium here is also referred to as “paper”, but the material is not limited, and a recording medium, a recording medium, a transfer material, a recording paper, and the like are also used synonymously. The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics. The image formation is not only giving an image having a meaning such as a character or a figure to the medium but also giving an image having no meaning such as a pattern to the medium (simply ejecting a droplet). Also means. The ink is not limited to so-called ink, and is not particularly limited as long as it becomes liquid when ejected. For example, the ink is a generic term for liquids including DNA samples, resists, pattern materials, and the like. Use.

  A droplet discharge head in an ink jet recording apparatus which is an example of an image forming apparatus includes a nozzle that discharges ink droplets, a pressurized liquid chamber that communicates with the nozzle, and an actuator unit that generates energy for boosting the pressurized liquid chamber And. The actuator means is driven to boost the pressure in the pressurized liquid chamber and eject ink droplets from the nozzles. Ink-on-demand systems, which eject ink droplets only when recording is required, are the mainstream. It is. Depending on the type of actuator means for ejecting ink droplets, it is roughly classified into methods such as a piezo method, a bubble method, and an electrostatic method.

  At present, a droplet discharge head adopting a piezo method is mainly used. As this piezo-type actuator means, one using a flexural vibration mode electro-mechanical transducer that vibrates in the thickness direction of the electro-mechanical transducer has been put into practical use. In the droplet discharge head using the electro-mechanical conversion element in this flexural vibration mode, the electro-mechanical conversion element flexures and vibrates, thereby changing the internal pressure of the pressurized liquid chamber via the vibration plate, thereby causing ink droplets to be discharged from the nozzle. Discharge. Specifically, the electro-mechanical conversion element is configured by forming a lower electrode layer, an electro-mechanical conversion layer, and an upper electrode layer in layers. The shape of the electro-mechanical conversion element is flat when the application of the drive voltage applied between the lower electrode layer and the upper electrode layer of the electro-mechanical conversion element is off. When the drive voltage application is on when the drive voltage application is on, the shape of the electro-mechanical conversion element is a curved shape that is bent so as to protrude toward the pressurized liquid chamber in the thickness direction (hereinafter referred to as a first curved shape). It is. When the driving voltage is applied, the internal pressure of the pressurizing liquid chamber is increased via the diaphragm, and ink droplets are ejected from nozzles provided in a part of the pressurizing liquid chamber. When the driving voltage application is turned on and the driving voltage application is turned off, the shape of the electromechanical conversion element returns from the first curved shape to the flat shape, and the internal pressure of the pressurized liquid chamber is reduced. In this case, the pressure is reduced to such an extent that air is not sucked from the nozzle into the pressurized liquid chamber and a mini-scus formed on the nozzle is present. Then, the ink is supplied to the pressurizing liquid chamber from an ink storage unit such as an ink cartridge via a common liquid chamber communicating with the pressurizing liquid chamber and an ink supply path.

  By the way, an ink jet recording apparatus equipped with the droplet discharge head may be continuously driven. In this case, the flexural vibration of the electromechanical conversion element in the droplet discharge head is continuously performed. If this continuous driving is performed for a long time, the electromechanical conversion element is mechanically fatigued and cannot maintain a flat shape when the driving voltage application is off, and protrudes from the flat shape to the pressurized liquid chamber side in the thickness direction. Thus, the bent shape is bent (hereinafter referred to as the second bent shape). The first curved shape of the electromechanical conversion element when the drive voltage application is on is defined by the material and thickness of the electromechanical conversion element. For these reasons, the displacement width in the thickness direction of the electro-mechanical conversion element when the drive voltage application is on is reduced, so that the pressure increase value and the pressure decrease value in the pressurized liquid chamber are reduced as compared with the target values. In a droplet discharge head equipped with such an electro-mechanical conversion element, when the driving voltage is applied, the target boosted value is not reached, so that the target ink droplet amount is not discharged and the image quality deteriorates. In addition, when the drive voltage application is turned off, there is a problem that the target miniscus cannot be present and the ink drips and soils a medium such as a recording material.

  As a droplet discharge head, one described in Patent Document 1 is known. In the droplet discharge head of Patent Document 1, the shape of the electro-mechanical conversion element when the driving voltage application is turned off is a curved shape that is bent so as to protrude toward the pressurized liquid chamber in the thickness direction (hereinafter referred to as a third type). It is formed in advance in a curved shape.) The third curved shape is substantially the same curved shape as the second curved shape. The shape of the electromechanical conversion element when the drive voltage application is on is bent from the third curved shape to the first curved shape. The shape of the electromechanical conversion element when the drive voltage application is off returns from the first curved shape to the third curved shape. When the ink droplet ejection operation and the ink supply operation are repeatedly performed, the shape of the electromechanical conversion element is bent from the third curved shape to the first curved shape, or from the first curved shape to the third curved shape. Repeat or return to.

In the droplet discharge head of Patent Document 1, even when continuous driving is performed for a long time, the shape of the electro-mechanical conversion element when the driving voltage application is off is further bent from the previously bent third curved shape. There is little to do. As a result, it is possible to suppress a decrease in the displacement width in the thickness direction of the electromechanical change element when the drive voltage application is on, and the pressure increase value and the pressure decrease value in the pressurizing liquid chamber become substantially target values.
However, in the process of manufacturing the droplet discharge head of Patent Document 1, a press method is used as a method for forming the electromechanical conversion element in a curved shape. Even if an attempt is made to apply the pressure to the electromechanical conversion element by this press method to form the target third curved shape, the shape of the electromechanical conversion element is affected by the elastic force inherent in the electromechanical conversion element. May not be the intended third curved shape. In this case, it is difficult to obtain the pressure increase value and the pressure reduction value in the target pressurized liquid chamber. Although it is conceivable to continue pressing for a long time in order to obtain the target third curved shape, there arises a problem that the production cost increases.

  The present invention has been made in view of the above problems, and the objects thereof are as follows. Droplet discharge head manufacturing method capable of manufacturing a droplet discharge head having a curved electro-mechanical conversion element while suppressing production costs, a liquid discharge head manufactured by the manufacturing method, and an image on which the droplet discharge head is mounted A forming apparatus is provided.

  In order to achieve the above object, the invention according to claim 1 is a liquid droplet ejection head for ejecting liquid droplets from a nozzle using a curved electro-mechanical conversion element bent so as to protrude into a pressurized liquid chamber. In the manufacturing method, a diaphragm forming step of forming a diaphragm on a substrate, and each material of a lower electrode layer, an electro-mechanical conversion layer, and an upper electrode layer constituting the electro-mechanical conversion element are sequentially formed on the diaphragm. And forming the electro-mechanical conversion element by heating each time the layers are formed, and facing the electro-mechanical conversion element across the diaphragm A pressurizing liquid chamber forming step for forming the pressurizing liquid chamber so that the vibration plate forms a part of the pressurizing liquid chamber at the position of the substrate; and the partition walls defining the pressurizing liquid chamber. The nozzle is formed at the end opposite to the side in contact with the diaphragm. And it is characterized in that it has a nozzle plate bonding step of bonding the nozzle plate.

  In the present invention, in the electromechanical conversion element forming step, the lower electrode layer of the electromechanical conversion element is formed on the diaphragm. At this time, the material of the lower electrode layer is in a state where there is no deflection following the surface shape of the diaphragm. After that, when firing is performed to remove the liquid component of the material of the lower electrode layer by heating, the lower electrode layer shrinks while gradually increasing the adhesion between the lower electrode layer and the diaphragm, and the lower electrode at the end of firing The layer has a contraction force that tends to contract. At this time, the surface of the lower electrode layer opposite to the interface with the diaphragm is an open end and is bent. On the other hand, the contraction force is also transmitted to the vicinity of the interface between the lower electrode layer and the diaphragm, and a stress opposite to the contraction force of the lower electrode layer is generated near the interface with the diaphragm of the lower electrode layer. They are in a balanced state. That is, a stress in a direction toward the central portion in the short direction of the pressurized liquid chamber is generated on the interface side of the lower electrode layer with the diaphragm, and the pressurized liquid chamber is formed on the interface side of the diaphragm with the lower electrode layer. The stress which is going to extend in the direction away from the center part of the transversal direction of has occurred. An electro-mechanical conversion layer is formed on the lower electrode layer, and an upper electrode layer is formed on the electro-mechanical conversion layer. In the formation of these layers, the same mechanism as in the formation of the lower electrode layer occurs. For this reason, on the interface side of the diaphragm with the lower electrode layer, there is a cumulative amount of stress that tends to extend in the direction away from the central portion in the short direction of the pressurized liquid chamber that occurs during the formation of each layer. Yes. The stress to be extended on the interface side with the lower electrode layer of the diaphragm is also transmitted to the surface of the opposite diaphragm on the interface side with the lower electrode layer, and the stress from the substrate on which the diaphragm is formed Is in a balanced state. The stress that tends to extend away from the central portion of the pressurizing fluid chamber in the lateral direction of the pressurizing fluid chamber is caused by the formation of the pressurizing fluid chamber on the substrate in the pressurizing fluid chamber forming step. When the diaphragm constituting the part appears, it is opened. At this time, in the vicinity of the interface between the diaphragm and the lower electrode layer, the diaphragm contracts due to the contraction force from the lower electrode layer. Further, deformation of the diaphragm other than that constituting a part of the pressurizing fluid chamber is regulated by the partition wall that partitions the pressurizing fluid chamber. Accordingly, the diaphragm is easily bent into a curved shape so as to protrude toward the open pressurized liquid chamber side on the opposite side to the vicinity of the interface with the lower electrode layer of the diaphragm to be contracted. The bending amount of the curved shape of the electro-mechanical conversion element is determined by the bending of the diaphragm that receives pressure due to the bending of the electro-mechanical conversion element. Since the rigidity of the diaphragm is higher than the rigidity of the electromechanical conversion element, the pressure due to the bending of the electromechanical conversion element has little influence on the bending of the diaphragm. Since the diaphragm is a single body, for example, if the material and thickness of the diaphragm are defined, the bending amount of the curved shape of the diaphragm is determined. For this reason, in the diaphragm forming process, if the material and thickness of the diaphragm are specified to be the desired one so that the diaphragm is deflected, the electro-mechanical conversion element The amount of bending of the curved shape bent through the diaphragm so as to protrude toward the pressurized liquid chamber is determined to be the target amount of bending. As a result, a droplet discharge head that is manufactured in a manufacturing time shorter than the manufacturing time in the case of using a conventional press process, and that includes a curved electro-mechanical conversion element with a target deflection amount while suppressing the production cost. A unique effect that it can be manufactured is obtained.

1 is a perspective view illustrating a configuration of an ink jet recording apparatus according to an embodiment. It is a side view of the mechanism part of the inkjet recording device of this embodiment. (A) It is sectional drawing of the droplet discharge head at the time of manufacture, (b) It is sectional drawing of the droplet discharge head of this embodiment. It is process sectional drawing which shows the manufacturing process of the droplet discharge head of this embodiment. It is a figure explaining a curvature radius. It is sectional drawing which shows what has arrange | positioned the several droplet discharge head of this embodiment.

  First, the configuration of an ink jet recording apparatus equipped with a droplet discharge head which is an example of a droplet discharge head according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration of an ink jet recording apparatus according to the present embodiment, and FIG. 2 is a side view of a mechanism portion of the ink jet recording apparatus according to the present embodiment.

  The ink jet recording apparatus 100 of this embodiment shown in FIGS. 1 and 2 includes a carriage 101 that can move in the main scanning direction inside the apparatus main body. And the printing mechanism part 103 etc. which are comprised by the ink cartridge 102 etc. which supply the ink with respect to the droplet discharge head 1 of this embodiment and the droplet discharge head 1 mounted in the carriage 101 are accommodated. A sheet feeding cassette (or a sheet feeding tray) 104 on which a large number of recording sheets P can be stacked from the front side is detachably attached to the lower part of the apparatus main body. In addition, it has a manual feed tray 105 that is opened to manually feed the recording paper P. The recording paper P fed from the paper feed cassette 104 or the manual feed tray 105 is taken in, and after a required image is recorded by the printing mechanism unit 103, the paper is discharged onto a paper discharge tray 106 mounted on the rear side.

  The printing mechanism 103 holds the carriage 101 slidably in the main scanning direction with a main guide rod 107 and a sub guide rod 108 which are guide members horizontally mounted on left and right side plates (not shown). The carriage 101 has a droplet discharge head 1 for discharging ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk), and a plurality of ink discharge ports (nozzles) in the main scanning direction. Are arranged in the sub-scanning direction orthogonal to. The ink droplet is ejected in the downward direction. In addition, each ink cartridge 102 for supplying ink of each color to the droplet discharge head 1 is replaceably mounted on the carriage 101.

  The ink cartridge 102 is provided with an atmosphere port communicating with the atmosphere above, and a supply port for supplying ink to the droplet discharge head 1 below. A porous body filled with ink is contained inside, and the ink supplied to the droplet discharge head 1 is maintained at a slight negative pressure by the capillary force of the porous body. Further, although the droplet discharge head 1 is used for each color, a single droplet discharge head having nozzles for discharging ink droplets of each color may be used.

  Here, the carriage 101 is slidably fitted to the main guide rod 107 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the secondary guide rod 108 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 101 in the main scanning direction, a timing belt 112 is stretched between a driving pulley 110 and a driven pulley 111 that are rotationally driven by a main scanning motor 109a. The timing belt 112 is fixed to the carriage 101, and the carriage 101 is reciprocally scanned by forward and reverse rotation of the main scanning motor 109a.

  On the other hand, in order to transport the recording paper P set in the paper feed cassette 104 to the lower side of the droplet discharge head 1, a paper feed roller 113, a friction pad 114, a guide member 115, a transport roller 116, a transport roller 117, a transport roller 116 and a tip roller 118. The paper feed roller 113 and the friction pad 114 separate and feed the recording paper P from the paper feed cassette 104. The guide member 115 is a guide member that guides the recording paper P. The conveyance roller 116 is a conveyance roller that reverses and conveys the fed recording paper P. The leading end roller 118 is a roller that regulates the conveying roller 117 pressed against the circumferential surface of the conveying roller 116 and the feeding angle of the recording paper P from the conveying roller 116. The conveyance roller 116 is rotationally driven via a gear train by the sub-scanning motor 109b.

  In addition, a printing receiving member 119 that is a paper guide member is provided to guide the recording paper P fed from the transport roller 116 below the droplet discharge head 1 in accordance with the moving range of the carriage 101 in the main scanning direction. ing. A conveyance roller 120 and a spur 121 that are rotationally driven to send the recording paper P in the paper discharge direction are provided on the downstream side of the printing receiving member 119 in the paper conveyance direction. Further, a discharge roller 123 and a spur 124 for feeding the recording paper P to the discharge tray 106, and guide members 125 and 126 for forming a discharge path are provided.

  When recording with the inkjet recording apparatus 100, the droplet discharge head 1 is driven in accordance with the image signal while moving the carriage 101, thereby discharging ink onto the stopped recording paper P to record one line. Thereafter, after the recording paper P is conveyed by a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the recording paper P reaches the recording area, the recording operation is terminated and the recording paper P is discharged.

  A recovery device 127 for recovering the ejection failure of the droplet ejection head 1 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 101. Each of the recovery devices 127 includes a cap unit, a suction unit, and a cleaning unit (not shown). During printing standby, the carriage 101 is moved to the recovery device 127 side, and the droplet discharge head 1 is capped by the capping unit to keep the discharge port portion in a wet state, thereby preventing discharge failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  Further, when a discharge failure occurs, the discharge port (nozzle) of the droplet discharge head 1 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port through the tube with a suction unit. Ink, dust, etc. adhering to the ejection port surface are removed by the cleaning means, and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  As described above, the ink jet recording apparatus 100 is equipped with a droplet discharge head of the present invention described later. For this reason, there is no ink droplet ejection failure due to vibration plate drive failure, and fluctuations in displacement are suppressed, so that stable ink droplet ejection characteristics can be obtained and image quality is improved.

  FIG. 3 is a cross-sectional view of the droplet discharge head of this embodiment. 3A is a cross-sectional view of the droplet discharge head at the time of manufacture, and FIG. 3B is a cross-sectional view of the droplet discharge head after continuous driving. The droplet discharge head 10 of the droplet discharge head of this embodiment shown in FIG. 3 includes an ink liquid chamber 13 and a pressure generating means. The ink liquid chamber 13 is a pressurized liquid chamber that communicates with the nozzle 11 that discharges ink droplets provided on the nozzle plate 12. The pressure generating means is an actuator for discharging ink in the ink liquid chamber 13. The ink liquid chamber 13 is also referred to as a discharge chamber, a pressurized liquid chamber, a pressure chamber, an ink flow path, and the like. Examples of the pressure generating means include a piezo type and a thermal type (bubble type). Among them, the piezoelectric type uses an electro-mechanical conversion element such as a piezoelectric element (for example, lead zirconate titanate (PZT), which is a ternary metal oxide) 14 to form the wall surface of the ink liquid chamber. Ink droplets are ejected by deforming the vibrating plate 15. This piezo type includes a longitudinal vibration (push mode) type utilizing deformation in the d33 direction, a transverse vibration (bend mode) type utilizing deformation in the d31 direction, and a shear mode type utilizing shear deformation. is there.

  Recently, a thin film actuator in which the ink liquid chamber 13 and the electro-mechanical conversion element 14 are directly formed on a Si substrate has been devised due to advances in semiconductor processes and MEMS (Micro Electro Mechanical System). However, when such an electro-mechanical conversion element 14 is repeatedly used, the electro-mechanical conversion element 14 is mechanically fatigued, and the flat shape of the thin film actuator during manufacture shown in FIG. 3A cannot be maintained. Then, as shown in FIG. 3B, the electro-mechanical conversion element 14 is bent toward the ink chamber 13 as compared with the flat shape of the thin film actuator at the time of manufacture (the one-dot chain line A in the figure). The amount of displacement of the electromechanical conversion element 14 is reduced. In an ink jet recording apparatus equipped with such an electro-mechanical conversion element, there arises a problem that ejection droplet characteristics such as ejection droplet volume and ejection droplet velocity are not stable. This problem exists not only in ink jet recording apparatuses that eject ink but also in other liquid ejection apparatuses that eject liquids other than ink. The present invention is intended to suppress the change in the amount of displacement more than ever by deflecting the electro-mechanical conversion element into a curved shape so as to protrude to the ink liquid chamber 13 side.

As a material of the substrate 16 forming the ink liquid chamber 13, it is preferable to use a silicon single crystal substrate, and it is usually preferable to have a thickness of 100 to 600 [μm]. There are three types of plane orientations, (100), (110), and (111), but (100) and (111) are generally widely used in the semiconductor industry. A single crystal substrate having a plane orientation of 100) was mainly used. When the ink liquid chamber 13 is manufactured, the silicon single crystal substrate is processed using etching. In this case, anisotropic etching is generally used as an etching method. Anisotropic etching utilizes the property that the etching rate is different with respect to the plane orientation of the crystal structure. For example, anisotropic etching immersed in an alkaline solution such as KOH (compared to the (100) plane ( 111) plane has an etching rate of about 1/400. Accordingly, a structure having an inclination of about 54 ° can be produced in the plane orientation (100), whereas a deep groove can be dug in the plane orientation (110). For this reason, it has been found that the arrangement density can be increased while maintaining rigidity, and it is also possible to use a single crystal substrate having a (110) plane orientation as this configuration. However, in this case, SiO ₂ that is a mask material is also etched, and this point is also used with attention.

The vibration plate 15 receives a force generated by the electro-mechanical conversion film 14a, deforms and discharges the ink in the ink liquid chamber 13 from the nozzle 11, so that the vibration plate 15 has a predetermined strength. preferable. Examples of the material include Si, SiO ₂ , and Si ₃ N _{4 produced} by chemical vapor deposition (CVD). Furthermore, it is preferable to select a material close to the linear expansion coefficient of the lower electrode layer 14b and the electromechanical conversion film 14a shown in FIG. In particular, as the electromechanical conversion film 14a, since PZT is generally used as a material, the linear expansion coefficient close to 8 × 10 ⁻⁶ (1 / K) is 5 × 10 ⁻⁶ to 10 × 10. A material having a linear expansion coefficient of × 10 ⁻⁶ is preferable. Furthermore, a material having a linear expansion coefficient of 7 × 10 ^{−6 to} 9 × 10 ⁻⁶ is more preferable.

  The diaphragm is preferably formed by laminating a plurality of films having tensile stress or compressive stress by a low pressure chemical vapor deposition method (LPCVD). The reason for this is an SOI wafer in the case of a single layer film, but in that case the wafer cost is very high, and it is not possible to set an arbitrary film stress when trying to make the bending rigidity uniform. On the other hand, in the case of a diaphragm having a laminated structure, by optimizing the laminated structure, it is possible to obtain a degree of freedom to set the rigidity and film stress of the diaphragm to a desired value. Stress control can be realized by a combination of lamination, film thickness, and lamination configuration. Thereby, it can respond to the material and film thickness of an electromechanical conversion element (an electrode layer, a ferroelectric layer) in a timely manner. In addition, since a stable diaphragm with less fluctuation in rigidity and stress due to the firing temperature of the electro-mechanical conversion film can be obtained, droplet ejection characteristics can be made highly accurate and a stable droplet ejection head can be realized. it can.

The lower electrode layer 14b is formed of a metal material, an adhesion layer, and a conductive oxide layer, and platinum having high heat resistance and low reactivity has been conventionally used as the metal material. However, it may not be said that it has sufficient barrier properties against lead, and examples include platinum group elements such as iridium and platinum-rhodium, and alloy films thereof. In the case of using platinum, it is preferable that Ti, TiO ₂ , Ta, Ta ₂ O ₅ , Ta ₃ N _5, etc. are laminated first because of poor adhesion to the base (particularly SiO ₂ ). As a production method, vacuum film formation such as sputtering or vacuum deposition is generally used, and the film thickness is preferably 0.05 to 1 [μm], more preferably 0.1 to 0.5 [μm]. . At this time, when PZT is selected as the electro-mechanical conversion film, the crystallinity thereof preferably has (111) orientation. Therefore, it is preferable to select Pt having a high (111) orientation as the electrode material. Further, in consideration of the fatigue characteristics over time of the displacement of the electro-mechanical conversion film 14a, a conductive oxide such as strontium ruthenate is laminated as an electrode part between the lower electrode layer 14b and the electro-mechanical conversion film 14a. It is preferable. Similarly to the lower electrode layer 14b, the upper electrode layer 14c is formed by using a metal material such as platinum and laminating a conductive oxide such as strontium ruthenate between the platinum and the electro-mechanical conversion film 14a.

Specific materials for the electro-mechanical conversion film 14a are as follows. Examples thereof include aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds thereof. These can be produced by a spin coater using a sputtering method or a Sol-Gel method. The film thickness is preferably from 0.1 to 10 [μm], more preferably from 0.5 to 3 [μm]. If it is smaller than this range, it becomes difficult to process the ink liquid chamber 13 as shown in FIG. 2, and if it is larger than this range, the vibration plate 15 is difficult to deform and displace, and ink droplet ejection becomes unstable. In the present invention, lead zirconate titanate (PZT) is mainly used as the electromechanical conversion film 14a. PZT is a solid solution of lead zirconate (PbTiO ₃ ) and titanic acid (PbTiO ₃ ), and the characteristics differ depending on the ratio. In general, the composition exhibiting excellent piezoelectric characteristics has a ratio of PbZrO ₃ and PbTiO ₃ of 53:47. When expressed by the chemical formula, it is indicated as Pb (Zr0.53Ti0.47) O ₃ and general PZT (53/47). It is. Examples of composite oxides other than PZT include barium titanate. In this case, it is possible to prepare a barium titanate precursor solution by using barium alkoxide and a titanium alkoxide compound as starting materials and dissolving them in a common solvent.

These materials are described by the general formula ABO ₃ and correspond to composite oxides containing A = Pb, Ba, Sr B = Ti, Zr, Sn, Ni, Zn, Mg, and Nb as main components. The specific description is (Pb1-x, Bax) (Zr, Ti) O ₃ , (Pb) (Zrx, Tiy, Nb1-xy) O ₃ , which is obtained by partially replacing Pb at the A site with Ba. And Zr and Ti in the B site are partially substituted with Nb. Such replacement is performed by material modification for application of displacement characteristics of PZT. As a manufacturing method, it can be manufactured by a spin coater using a sputtering method or a Sol-Gel method. In that case, since patterning is required, a desired pattern is obtained by photolithography etching or the like.

  When the above PZT is produced by the Sol-Gel method, a PZT precursor solution is produced by using lead acetate, zirconium alkoxide, and titanium alkoxide compounds as starting materials and dissolving them in methoxyethanol as a common solvent to obtain a uniform solution. it can. Since the metal alkoxide compound is easily hydrolyzed by moisture in the atmosphere, an appropriate amount of acetylacetone, acetic acid, diethanolamine or the like may be added to the precursor solution as a stabilizer. When a PZT film is obtained on the entire surface of the base substrate, it is obtained by forming a coating film by a solution coating method such as spin coating, and performing heat treatments such as solvent drying, thermal decomposition, and crystallization. Since the transformation from the coating film to the crystallized film involves volume shrinkage, it is necessary to adjust the precursor concentration so that a film thickness of 100 nm or less can be obtained in one step in order to obtain a crack-free film. Become. The thickness of the electromechanical conversion film is preferably 0.5 to 5 [μm], more preferably 1 to 2 [μm]. If it is smaller than this range, it will not be possible to generate a sufficient displacement, and if it is larger than this range, many layers will be laminated, resulting in an increase in the number of steps and a longer process time.

<Example 1>
FIG. 4 is a process sectional view showing the manufacturing process. As shown in FIG. 4A, the silicon wafer of the substrate 16 is made of SiO ₂ (film thickness: 600 [nm]), Si ₃ N ₄ (film thickness: 250 [nm]), SiO ₂ (film thickness: 600 [nm]). nm]). Further, Si (film thickness: 200 [nm]) and SiO ₂ (film thickness: 500 [nm]) are laminated to form a diaphragm 15 of a laminated film. A titanium film (film thickness: 50 nm) is formed on the laminated film diaphragm 15, and a platinum film (film thickness: 250 [nm]) and an SrRuO ₃ film (film thickness: 50 [nm]) are successively formed as the lower electrode layer 14b. Sputter deposition was performed. The titanium film serves as an adhesion layer between SiO ₂ and the platinum film. Film formation was performed at a substrate heating temperature of 550 [° C.] during the sputtering film formation. When the raised heating temperature decreases, the lower electrode layer 14b generates a contraction force that tends to contract. Further, since the thermal expansion coefficients of the diaphragm 15 and the lower electrode layer 14b are different, the vicinity of the interface between the diaphragm 15 and the lower electrode layer 14b with respect to the contraction force of the lower electrode layer 14b starts from the central portion in the short direction. A tensile stress is generated to move away. Next, a solution prepared with a composition ratio of Pb: Zr: Ti = 150: 53: 47 was prepared as the electro-mechanical conversion film 14a. For the synthesis of a specific precursor coating solution, lead acetate trihydrate, isopropoxide titanium and isopropoxide zirconium were used as starting materials. Crystal water of lead acetate was dissolved in methoxyethanol and then dehydrated. The lead amount is excessive with respect to the stoichiometric composition. This is to prevent crystallinity deterioration due to so-called lead loss during heat treatment.

Then, isopropoxide titanium and isopropoxide zirconium are dissolved in methoxyethanol, the alcohol exchange reaction and the esterification reaction are advanced, and the PZT precursor solution is synthesized by mixing with the methoxyethanol solution in which the lead acetate is dissolved. did. The PZT concentration was 0.5 [mol / l]. Using this solution, as shown in FIG. 4B, a film was formed by spin coating, dried at 120 [° C.] after the film formation, and pyrolyzed at 500 [° C.]. After thermal decomposition treatment of the third layer, crystallization heat treatment (temperature: 750 ° C.) was performed by rapid heat treatment (RTA: Rapid Thermal Annealing). At this time, the film thickness of PZT was 240 [nm]. This process was performed a total of 6 times (18 layers) to obtain a PZT film thickness of about 1.6 [μm]. When the temperature of the raised heat treatment decreases, the electro-mechanical conversion layer 14a generates a contraction force that tends to contract. Then, in opposition to the contraction force, tensile stress is generated in the vicinity of the interface between the lower electrode layer 14b and the electro-mechanical conversion film 14a so as to move away from the central portion in the short direction. Actually, a difference between the tensile stress and the contraction force is generated inside the lower electrode layer. Next, as shown in FIG. 4C, an SrRuO ₃ film (film thickness: 40 [nm]) and a platinum film (film thickness: 125 [nm]) were sequentially formed as an upper electrode layer by sputtering. Film formation was performed at a substrate temperature of 300 [° C.] during sputtering film formation. The SrRuO ₃ film was subjected to post-annealing treatment at 550 [° C./300 s] in an oxygen atmosphere by rapid thermal processing. Thereafter, a photoresist (TSMR8800) manufactured by Tokyo Ohka Co., Ltd. is formed by spin coating. After a resist pattern was formed by ordinary photolithography, a pattern was prepared using an inductively coupled plasma (ICP) etching apparatus (manufactured by Samco). When the raised heating temperature decreases, the electro-mechanical conversion element 14 generates a cumulative contraction force (arrow A in the figure) that tends to contract. Then, a cumulative tensile stress (arrow B in the figure) tends to move away from the central portion in the short direction near the interface with the lower electrode layer 14b of the diaphragm 15 with respect to the contraction force of the electromechanical conversion element 14. Occur.

  Next, as shown in FIG. 4 (d), anisotropic wet etching is performed with an alkaline solution (KOH solution or TMHA solution) to form an ink liquid chamber in a post-process, and the width in the short direction is reduced. An ink liquid chamber 13 having a thickness of 60 [μm] is formed. Then, an electro-mechanical conversion element and a droplet discharge head constituted by the electro-mechanical conversion element were produced. The electro-mechanical conversion film 14a, the lower electrode layer 14b, and the upper electrode layer 14c all have tensile stress. Then, when the ink liquid chamber is formed by etching and the vibration plate appears on the ink liquid chamber side and the surface on the ink liquid chamber side of the vibration plate is in a free open state, the tensile stress of the vibration plate is released. As a result, the diaphragm including the electromechanical conversion element is bent into a curved shape so as to protrude toward the ink liquid chamber. On the other hand, the total stress can be adjusted by devising the layer structure of the diaphragm having a laminated structure, and the deflection amount of the diaphragm can be changed. In this embodiment, the radius of curvature of bending of the electromechanical conversion element is 1800 [μm], the amount of bending is 0.252 [μm], and the radius of curvature is defined in FIG.

<Example 2>
With respect to the diaphragm configuration of Example 1, a diaphragm is manufactured so that the amount of deflection is 0.225 [μm] (curvature radius: 2000 [μm]) by stress design. Then, the lower electrode layer, the electromechanical conversion film, the upper electrode layer, and the etching step were produced under the same conditions as in Example 1.

<Example 3>
With respect to the diaphragm configuration of the first embodiment, the diaphragm is manufactured so that the amount of deflection is 0.42 [μm] (curvature radius: 1070 [μm]) by stress design. Then, the lower electrode layer, the electromechanical conversion film, the upper electrode layer, and the etching step were produced under the same conditions as in Example 1.

<Comparative Example 1>
With respect to the diaphragm configuration of the first embodiment, due to the stress design, the bending of the electromechanical conversion element has a curved shape protruding in the opposite direction to the ink liquid chamber, and the amount of bending is 0.25 [μm] (curvature radius; 1800 [ μm]) is produced. Then, the lower electrode layer, the electromechanical conversion film, the upper electrode layer, and the etching step were produced under the same conditions as in Example 1.

<Comparative example 2>
Compared to the diaphragm configuration of Example 1, the diaphragm is composed of a single layer film of SiO ₂ , and the lower electrode layer, the electro-mechanical conversion film, the upper electrode layer, and the etching process are manufactured under the same conditions as in Example 1. Do. The bending was made into a curved shape protruding to the ink liquid chamber side, and the bending amount was 0.25 [μm] (curvature radius: 1800 [μm]).

<Comparative Example 3>
With respect to the diaphragm configuration of the first embodiment, the flexure is curved so as to protrude toward the ink liquid chamber side due to the stress design, and the flexure amount is 0.50 [μm] (curvature radius: 900 [μm]). Make a plate. Then, the lower electrode layer, the electromechanical conversion film, the upper electrode layer, and the etching step were produced under the same conditions as in Example 1.

<Comparative example 4>
With respect to the diaphragm configuration of the first embodiment, the flexure is curved so as to protrude toward the ink liquid chamber side due to the stress design, and the flexure amount is 0.15 [μm] (curvature radius: 3000 [μm]). Make a plate. Then, the lower electrode layer, the electromechanical conversion film, the upper electrode layer, and the etching step were produced under the same conditions as in Example 1.

The droplet discharge heads produced in Examples 1 to 3 and Comparative Examples 1 to 4 are used. An electro-mechanical conversion element in continuous driving using a pulse waveform having an applied electric field of 150 [kV / cm], a rise of 1 [μs], a fall of 1 [μs], a pulse width of 4 [μs], and 100 [kHz]. The fluctuations in the displacement were evaluated. The displacement was measured using a laser Doppler vibrometer. Evaluation of variation in displacement is based on the rate of change of displacement after applying an electric field of 1 × 10 ⁸ [times] when the absolute value of the initial displacement of measurement is 100 [%]. It is shown in 1. As a criterion for judgment, if the deterioration rate of displacement exceeds 5 [%], sufficient reliability cannot be obtained as the liquid ejection capability of the head. Therefore, it is effective that the displacement deterioration rate is 5 [%] or less. Standard.

From Examples 1 and 3, as the amount of bending of the electromechanical conversion element increases, the decrease in the amount of displacement due to continuous drive is suppressed. This is because by deflecting the electro-mechanical conversion element from the beginning toward the liquid chamber side, the amount of deviation from the curved shape of the bending due to continuous driving can be suppressed, and a decrease in the amount of displacement can be prevented. And since the thing of Example 3 has few fall rates of a displacement, even when it drives 1x10 ⁸ times, it is more preferable that the amount of bending of an electromechanical conversion element becomes near 0.45 [micrometers].

  In Comparative Example 1, the amount of deflection before driving is small when the bending amount of the electro-mechanical conversion element shown in FIG. 1 is a curved shape protruding in the opposite direction to the ink liquid chamber. This is because the electro-mechanical conversion element has a curved shape that protrudes in the opposite direction to the ink liquid chamber. The rigidity of the diaphragm is reduced to counteract the tensile stress of the lower electrode layer, electro-mechanical conversion film, and upper electrode layer. This is because it was enlarged. For this reason, in order to ensure the amount of displacement, it is preferable that the electromechanical conversion element has a curved shape protruding toward the ink liquid chamber. In Comparative Example 2, since the diaphragm cracks during continuous driving, the diaphragm is preferably laminated rather than a single layer. In Comparative Example 3, as a result of the initial deflection of the diaphragm being too large, a sufficient amount of displacement for ejecting ink droplets could not be obtained, and cracking of the diaphragm occurred during continuous driving, so the initial deflection of the diaphragm was It is desirable that it is 0.45 [μm] or less. In Comparative Example 4, a sufficient amount of displacement for ejecting ink droplets is obtained, but since the rate of decrease in displacement due to continuous driving increases, the initial deflection amount of the diaphragm is 0.25 [μm] or more. It is desirable to be.

  FIG. 6 is a cross-sectional view showing a plurality of droplet discharge heads according to this embodiment. According to this embodiment, the electromechanical conversion element can be formed by a simple manufacturing process (and having performance equivalent to that of bulk ceramics). A liquid discharge head can be formed by removing etching from the rear surface for forming a pressure chamber and joining a nozzle plate having nozzle holes. In the figure, descriptions of liquid supply means, flow paths, and fluid resistance are omitted.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect 1)
In a manufacturing method of a droplet discharge head that discharges droplets from a nozzle 11 using a curved electro-mechanical conversion element 14 that is bent so as to protrude into a pressurized liquid chamber such as an ink liquid chamber 13, The vibration plate forming step for forming the vibration plate 15 and the lower electrode layer 14b, the electro-mechanical conversion layer 14a and the upper electrode layer 14c constituting the electro-mechanical conversion element 14 are sequentially formed on the vibration plate 15. In addition, by heating and firing for each layer formation, an electro-mechanical conversion element forming step for forming the electro-mechanical conversion element 14 and a substrate 16 facing the electro-mechanical conversion element 14 with the diaphragm 15 interposed therebetween. The pressurizing liquid chamber forming step for forming the pressurizing liquid chamber and the diaphragm 15 of the partition wall defining the pressurizing liquid chamber are brought into contact with each other so that the vibrating plate 15 constitutes a part of the pressurizing liquid chamber. Nozzle 11 was formed at the end opposite to the side And having a nozzle plate bonding step of bonding the nozzle plate 12. According to this, as described in the above embodiment, in the electro-mechanical conversion element forming step, the lower electrode layer 14 b of the electro-mechanical conversion element 14 is formed on the diaphragm 15. At this time, the material of the lower electrode layer 14b is in a state where there is no deflection following the surface shape of the diaphragm 15. Thereafter, when baking is performed to remove the liquid component of the material of the lower electrode layer 14b by heating, the lower electrode layer 14b contracts while gradually increasing the adhesion between the lower electrode layer 14b and the diaphragm 15, and the baking ends. A contraction force that tends to contract occurs in the lower electrode layer 14b at the time. At this time, the surface of the lower electrode layer 14b opposite to the interface with the diaphragm 15 is an open end and is bent. On the other hand, the contraction force is also transmitted to the vicinity of the interface between the lower electrode layer 14b and the diaphragm 15, and in the vicinity of the interface between the lower electrode layer 14b and the diaphragm 15, the contraction force of the lower electrode layer 14b is contradictory. Stress is generated and balanced with each other. That is, a stress in the direction toward the central portion in the short side direction of the pressurized liquid chamber is generated on the interface side of the lower electrode layer 14b with the diaphragm 15, and on the interface side of the diaphragm 15 with the lower electrode layer 14b. A stress is generated that tends to extend away from the central portion of the pressurized liquid chamber in the short direction. An electro-mechanical conversion layer 14a is formed on the lower electrode layer 14b, and an upper electrode layer 14c is formed on the electro-mechanical conversion layer 14a. In the formation of these layers, the same mechanism as in the formation of the lower electrode layer 14b occurs. For this reason, on the interface side of the diaphragm 15 with the lower electrode layer 14b, a stress is generated that accumulates in a direction away from the central portion in the short direction of the pressurizing liquid chamber generated every time the layers are formed. doing. The stress that tends to extend on the interface side of the diaphragm 15 with the lower electrode layer 14b is also transmitted to the surface of the diaphragm 15 opposite to the interface side with the lower electrode layer 14b, and the diaphragm 15 is formed. The state is balanced by the stress from the substrate 16. The stress that tends to extend away from the central portion in the short direction of the pressurizing liquid chamber in the diaphragm 15 is caused by the pressurizing liquid chamber being formed on the substrate 16 in the pressurizing liquid chamber forming step. Is opened when the diaphragm 15 constituting a part of the plate appears. At this time, in the vicinity of the interface between the diaphragm 15 and the lower electrode layer 14b, the diaphragm 15 is contracted due to the contraction force from the lower electrode layer 14b. Further, deformation of the diaphragm 15 other than that constituting a part of the pressurizing liquid chamber is regulated by the partition wall defining the pressurizing liquid chamber. As a result, the diaphragm 15 bends in a curved shape so as to protrude toward the open pressurized liquid chamber side opposite to the vicinity of the interface with the lower electrode layer 14b of the diaphragm 15 to be contracted. easy. The bending amount of the curved shape of the electro-mechanical conversion element 14 is determined by the bending of the diaphragm 15 that receives pressure due to the bending of the electro-mechanical conversion element 14. Since the rigidity of the diaphragm 15 is higher than the rigidity of the electro-mechanical conversion element 14, the pressure due to the bending of the electro-mechanical conversion element 14 has little influence on the bending of the diaphragm 15. Since the diaphragm 15 is a single body, for example, if the material and thickness of the diaphragm 15 are defined, the bending amount of the curved shape of the diaphragm 15 is determined. For this reason, in the diaphragm forming process, the material and thickness of the diaphragm 15 are defined to be the target so that the amount of deflection of the diaphragm 15 becomes the target amount of deflection. As a result, the bending amount of the curved shape bent through the diaphragm 15 so as to protrude toward the pressurized liquid chamber side of the electro-mechanical conversion element 14 is determined to be a target bending amount. Therefore, it is manufactured in a manufacturing time shorter than the manufacturing time when using a conventional press process, and a droplet discharge head including a curved electro-mechanical conversion element with a desired deflection amount is manufactured while suppressing the production cost. it can.
(Aspect 2)
In (Aspect 1), when the width of the diaphragm 15 in the short direction is set to 60 [μm], the target deflection amount of the electromechanical conversion element 14 is set to a range of 250 to 450 [nm]. According to this, as described in the example of the above embodiment, it is known that the rigidity and tensile stress of the entire diaphragm 15 can be controlled by a combination of lamination, film thickness, and lamination configuration. For this reason, when the width of the diaphragm 15 in the short direction is set to 60 [μm], the amount of deflection of the diaphragm 15 is set when the amount of deflection of the target electro-mechanical conversion element 14 is in the range of 250 to 450 [nm]. The diaphragm 15 is formed so as to have a target value of 0.42 [μm]. As a result, a stable diaphragm can be obtained that can respond to the material and film thickness of the electro-mechanical conversion element in a timely manner, and that has less fluctuation in rigidity and stress due to the firing temperature of the electro-mechanical conversion film. Therefore, it is possible to realize a liquid droplet ejection characteristic with high accuracy and a stable liquid droplet ejection head.
(Aspect 3)
In (Aspect 1), in the diaphragm forming step, the diaphragm 15 is formed in a laminated structure. According to this, as described in the above embodiment, in the case of a diaphragm having a laminated structure, the degree of freedom for setting the rigidity and film stress of the diaphragm to desired values is obtained by optimizing the laminated structure. be able to. Therefore, the diaphragm can be easily formed so that the diaphragm is bent toward the pressurized liquid chamber by a target amount of bending.
(Aspect 4)
A feature of the droplet discharge head manufactured by the method of manufacturing a droplet discharge head according to any one of (Aspect 1) to (Aspect 3). According to this, as described in the above embodiment, it is possible to suppress a decrease in the amount of displacement of the diaphragm and to stabilize the ejection droplet characteristics.
(Aspect 5)
(Embodiment 4) is characterized by an image forming apparatus that mounts the droplet discharge head and forms an image on a recording material by discharging a recording liquid from the droplet discharge head. According to this, as described in the above embodiment, the discharge characteristics are excellent and stable image formation can be performed.

DESCRIPTION OF SYMBOLS 1 Droplet discharge head 10 Droplet discharge head 11 Nozzle 12 Nozzle plate 13 Ink liquid chamber 14 Electro-mechanical conversion element 14a Electro-mechanical conversion film 14b Lower electrode layer 14c Upper electrode layer 15 Diaphragm 16 Substrate 100 Inkjet recording apparatus

Japanese Patent No. 344889

Claims (5)

In a method of manufacturing a droplet discharge head that discharges droplets from a nozzle using a curved electro-mechanical conversion element that is bent so as to protrude into a pressurized liquid chamber,
A diaphragm forming step of forming a diaphragm on the substrate;
The respective materials of the lower electrode layer, the electro-mechanical conversion layer, and the upper electrode layer constituting the electro-mechanical conversion element are sequentially formed on the diaphragm and heated and fired for each layer formation, An electro-mechanical conversion element forming step of forming an electro-mechanical conversion element;
A pressurizing liquid chamber that forms the pressurizing liquid chamber at a position of the substrate facing the electromechanical conversion element with the vibration plate interposed therebetween so that the vibrating plate forms a part of the pressurizing liquid chamber. Forming process;
And a nozzle plate joining step for joining a nozzle plate on which the nozzles are formed at an end of the partition partitioning the pressurized liquid chamber opposite to the side in contact with the vibration plate. Manufacturing method of the discharge head. In the manufacturing method of the droplet discharge head according to claim 1,
When the width of the diaphragm in the short direction is set to 60 [μm], a target deflection amount of the electro-mechanical conversion element is set in a range of 250 to 450 [nm]. Production method. In the manufacturing method of the droplet discharge head according to claim 1,
In the vibration plate forming step, the vibration plate is formed in a laminated structure.   A droplet discharge head manufactured by the method for manufacturing a droplet discharge head according to claim 1.   An image forming apparatus comprising the droplet discharge head according to claim 4 and forming an image on a recording material by discharging a recording liquid from the droplet discharge head.

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