JP2013065698A - Electro-mechanical conversion element, droplet discharge head, droplet discharge device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electro-mechanical conversion element that is installed in an image forming apparatus employing an ink jet printing method, and has a proper surface roughness of a diaphragm to obtain a proper crystal orientation of a lower electrode and an electro-mechanical conversion film, and thereby provides a stable driving force with time; a head that includes the element, and discharges droplets such as of ink; a droplet discharge device including the head; and an image forming apparatus including all of the above.SOLUTION: An electro-mechanical conversion element 10 includes: a diaphragm 12 formed on a substrate 11; a lower electrode 21 formed directly or indirectly on the diaphragm 12; an electro-mechanical conversion film 16 formed on the lower electrode 21; and an upper electrode 22 formed on the electro-mechanical conversion film 16. The lower electrode 21 includes a layer having a (111) orientation. The electro-mechanical conversion film 16 is made of PZT having the (111) orientation as a preferential orientation. The diaphragm 12 includes a polysilicon layer having a surface roughness of 5 nm or less.

Description

  The present invention relates to an electro-mechanical conversion element used as a drive source for a droplet discharge head for discharging a droplet of ink or the like provided in an image forming apparatus such as an ink jet printer, facsimile, or copying machine. The present invention relates to a droplet discharge head provided with the above, a droplet discharge device provided in such an image forming apparatus provided with the same, and an image forming apparatus including these.

  Conventionally, in such a droplet discharge head, a nozzle that discharges a droplet, a pressurizing chamber that contains ink (hereinafter referred to as ink) that communicates with the nozzle, and an ink in the pressurizing chamber. A diaphragm that vibrates for ejection from the nozzle, an electromechanical transducer such as a piezoelectric element or an electrothermal transducer such as a heater, or a wall surface of an ink flow path as a drive source for vibrating the vibrating plate An energy generating means comprising an oscillating plate and an electrode facing the oscillating plate is provided, and the ink is ejected from the nozzles by oscillating the oscillating plate with the energy generated by the driving source or the energy generating unit and pressurizing ink in the pressurizing chamber. Things are known. Such a pressurizing chamber may also be referred to as an ink flow path, a pressurized liquid chamber, a pressure chamber, a discharge chamber, a liquid chamber, or the like.

  As actuators that can be used or can be used as such driving sources, film structures such as semiconductor devices and electronic devices are known (see, for example, [Patent Document 1] to [Patent Document 19]). As such an actuator, for example, two types are put into practical use, one using a longitudinal vibration mode piezoelectric actuator that extends and contracts in the axial direction of the piezoelectric element, and one using a flexural vibration mode piezoelectric actuator. .

  Using a piezoelectric actuator in flexural vibration mode, for example, a uniform piezoelectric material layer is formed over the entire surface of the diaphragm by film formation technology, and this piezoelectric material layer is applied to the pressure generation chamber by lithography. A piezoelectric element is known that is divided into shapes to be formed and formed independently of each pressure generating chamber.

  In such a piezoelectric actuator, when the vector component of the spontaneous polarization axis of the piezoelectric film matches the electric field application direction, the expansion and contraction accompanying the increase and decrease of the electric field application intensity occurs effectively, and a large piezoelectric constant is obtained. Most preferably, the spontaneous polarization axis of the piezoelectric film and the electric field application direction completely coincide. Further, in order to suppress variations in the ink discharge amount, it is preferable that the in-plane variation in the piezoelectric performance of the piezoelectric film is small. Considering these points, a piezoelectric film having excellent crystal orientation is preferable.

  As a technique related to crystal orientation, for example, a technique for forming a piezoelectric film having excellent crystal orientation by forming a piezoelectric film on a Ti-containing noble metal electrode on which Ti is deposited in an island shape (for example, [Patent Document 1]), using a MgO substrate as a substrate, a technique for forming a piezoelectric film having excellent crystal orientation (for example, see [Patent Document 2]), and forming an amorphous ferroelectric film Thereafter, in a technique relating to a manufacturing method of a ferroelectric film in which the film is crystallized by a rapid heating method (see, for example, [Patent Document 3]), in a film forming process, a tetragonal system, an orthorhombic system, and a rhombus A perovskite complex oxide (which may contain unavoidable impurities) having any crystal structure of a rhombohedral system, and any one of (100) plane, (001) plane, and (111) plane Preferentially oriented on the surface Production process technique of a piezoelectric film having a degree of orientation to the film formation of the piezoelectric film is 95% or more (for example, see [Patent Document 4]) is known.

  As for the method of manufacturing a piezoelectric element, in the method of manufacturing a piezoelectric element in which a lower electrode, a piezoelectric film, and an upper electrode are sequentially stacked on a substrate, a seed layer containing at least one constituent element of the piezoelectric film on the substrate. And a step of sequentially forming a film and a lower electrode, a step of diffusing constituent elements of the piezoelectric film contained in the seed layer in a non-oxidizing atmosphere and depositing on the surface of the lower electrode, and the piezoelectric film on the lower electrode A technique has been proposed that sequentially includes a step of forming a film. According to this technique, a piezoelectric film having excellent crystallinity and excellent piezoelectricity can be formed at a relatively low temperature without using an expensive substrate such as MgO. Further, in such a technique, the thickness of the seed layer containing Ti is 5 to 50 nm, the thickness of the lower electrode is 50 to 500 nm, and the average surface roughness Ra of the lower electrode is 0.5 to 8.0 nm. It has been proposed to provide a piezoelectric element in which the piezoelectric constant d31 of the piezoelectric film is 150 pm / V or more by performing diffusion.

  By the way, various studies have been made on the diaphragm, and techniques using a metal oxide film (see, for example, [Patent Document 5]), nickel, chromium, aluminum, alumina, silicon oxide, or polyimide resin are used. In addition, attempts have been made to use an organic polymer material such as SiO 2, oxides of nickel, chromium, aluminum, and polyimide (see, for example, [Patent Document 6]).

  On the other hand, regarding the diaphragm, the present inventors have found that in a piezoelectric actuator having a diaphragm composed of a film formed by the LPCVD method, the surface roughness of the diaphragm depends on the crystal orientation of the lower electrode and PZT. It has been found that control of the surface roughness of the diaphragm is important because it greatly affects the droplet discharge characteristics.

  Specifically, it has been found that by reducing the surface roughness, it becomes a piezoelectric film in which electric field concentration hardly occurs, the breakdown voltage can be increased, and deterioration of the piezoelectric body can be suppressed. Since the surface roughness of the diaphragm is small, the processing accuracy of the subsequent process is improved, the uniformity within the wafer surface is good, and the ink discharge characteristics of each droplet discharge head can be made uniform. is there.

  In addition, a diaphragm composed of a film formed by the LPCVD method is a film that has been conventionally applied to semiconductors and MEMS devices, and since it is easy to process, it does not bring new process issues, A stable diaphragm can be obtained without using an expensive substrate such as SOI, and a liquid droplet ejection head with high accuracy and little variation can be realized.

  Furthermore, the present inventors have also found that in a diaphragm including a polysilicon film, the surface roughness increases due to polysilicon crystal grains, and the roughness of the diaphragm increases. In this regard, it is possible to reduce the surface roughness of an amorphous silicon film, but the process of forming a piezoelectric film with excellent crystal orientation requires heat treatment at a high temperature such as a baking step. Therefore, the roughness and stress of the silicon film fluctuate, making it impossible to realize a highly reliable droplet discharge head and limiting the piezoelectric element formation process. In some cases, the yield and cost It was found that there is a possibility of affecting.

  As described above, since the surface roughness of the diaphragm greatly affects the crystal orientation of the lower electrode and PZT, and greatly affects the droplet discharge characteristics, it is important to control the surface roughness of the diaphragm. Nevertheless, details regarding the roughness of the diaphragm are not stipulated in conventional techniques such as those described above. According to the studies by the present inventors, the surface roughness of the diaphragm is affected by, for example, the thickness of the silicon layer, and the surface roughness can be reduced if the silicon layer is thinned. Therefore, it is necessary to pay attention to these points in order to control the surface roughness of the diaphragm.

  The present invention is provided in an image forming apparatus such as an ink jet printer, a facsimile machine, a copying machine, etc., and optimizes the crystal orientation of the lower electrode and the electromechanical conversion film by making the surface roughness of the diaphragm appropriate. An electro-mechanical conversion element capable of obtaining a stable driving force over time, a droplet discharge head for discharging a droplet of ink or the like provided with the electro-mechanical conversion element, a droplet discharge device including the same, and the like An object of the present invention is to provide such an image forming apparatus.

  In order to achieve the above object, the present invention provides a diaphragm formed on a substrate, a lower electrode formed directly or indirectly on the diaphragm, and an electro-mechanical conversion formed on the lower electrode. And an upper electrode formed on the electro-mechanical conversion film, wherein the lower electrode includes a layer having a (111) orientation, and the electro-mechanical conversion film has (111) as a preferred orientation. The diaphragm is made of PZT, and the diaphragm is in an electro-mechanical conversion element including a polysilicon layer having a surface roughness of 5 nm or less.

  The present invention relates to a diaphragm formed on a substrate, a lower electrode formed directly or indirectly on the diaphragm, an electro-mechanical conversion film formed on the lower electrode, and the electro-mechanical An upper electrode formed on the conversion film, the lower electrode including a layer having a (111) orientation, and the electro-mechanical conversion film is made of PZT having (111) as a preferred orientation, and the diaphragm Is in an electro-mechanical conversion element including a polysilicon layer having a surface roughness of 5 nm or less. By optimizing the surface roughness of the diaphragm, the crystal orientation of the lower electrode and the electro-mechanical conversion film is optimized, It is possible to provide an electromechanical conversion element that can obtain a stable driving force.

It is the schematic of the cross section of an example of the electromechanical conversion element to which this invention is applied. It is the schematic of the cross section of an example of the droplet discharge head provided with the electromechanical conversion element shown in FIG. FIG. 4 is a schematic cross-sectional view of another example of a droplet discharge head including the electromechanical conversion element shown in FIG. 1. It is the schematic of the cross section of the diaphragm with which the electromechanical conversion element shown in FIG. 1 was equipped. It is the figure which showed the measurement result of the peak of each orientation of the electromechanical conversion element shown in FIG. It is a figure which shows the typical PE hysteresis curve at the time of evaluating the characteristic of an electromechanical conversion element. FIG. 4 is a schematic diagram of an image forming apparatus including the droplet discharge head illustrated in FIG. 3.

FIG. 1 shows an outline of a cross section of an example of an electromechanical conversion element to which the present invention is applied.
The electromechanical conversion element 10 includes a diaphragm 12 which is a film-forming diaphragm formed on the substrate 11 as a base film on the substrate 11, an adhesion layer 13 formed on the diaphragm 12, and the adhesion It has a lower electrode 21 formed on the layer 13, an electro-mechanical conversion film 16 formed on the lower electrode 21, and an upper electrode 22 formed on the electro-mechanical conversion film 16.

  The electro-mechanical conversion element 10 includes a diaphragm 12, an adhesion layer 13, a lower electrode 21, an electro-mechanical conversion film 16, and an upper electrode 22 in this order on a substrate 11. It is formed by forming a film by the technique used in the manufacture of

  Therefore, the lower electrode 21 is indirectly formed on the diaphragm 12 via the adhesion layer 13. However, the lower electrode 21 may be formed directly on the diaphragm 12 by omitting the adhesion layer 13. Further, the adhesion layer 13 may be included in the lower electrode 21 (see FIGS. 2 and 3 shown below). However, in FIGS. 2 and 3, the illustration of the adhesion layer 13 is merely omitted. The diaphragm 12 is directly formed on the substrate 11.

  The electro-mechanical conversion element 10 is a piezoelectric element including the electro-mechanical conversion film 16 as a piezoelectric film. The upper electrode 22 is an individual electrode.

  As shown in FIGS. 2 and 3, the electromechanical conversion element 10 can be used as a part of a droplet discharge head 30 that is a liquid ejecting head. The droplet discharge head 30 shown in FIG. 2 is an example of the configuration of one nozzle, and FIG. 3 is an outline of the droplet discharge head 30 formed by arranging a plurality of elements shown in FIG. ing.

  The droplet discharge head 30 is formed by etching the substrate 11 on which the electro-mechanical conversion element 10 is formed, as well as the electro-mechanical conversion element 10 that functions as a driving source, as described later. Hereinafter, a pressure chamber 31 as a pressurizing chamber that is an ink chamber for storing (ink) is provided, and a nozzle 32 that is a nozzle hole as an ink ejection port that ejects ink in the pressure chamber 31 in the form of droplets. And a nozzle plate 33 as ink nozzles.

  The droplet discharge head 30 is a head that discharges ink droplets from the nozzles 32 when the electro-mechanical conversion element 10 is driven. Specifically, the droplet discharge head 30 generates stress in the electromechanical conversion film 16 by being supplied with power to the lower electrode 21 and the upper electrode 22 as described later, thereby vibrating the diaphragm 12, Along with this vibration, the ink in the pressure chamber 31 is ejected from the nozzle 32 in the form of droplets. Note that illustration and description of liquid supply means, which are ink supply means for supplying ink into the pressure chamber 31, ink flow paths, and fluid resistance are omitted.

  Hereinafter, the material of the substrate 11, the diaphragm 12, the adhesion layer 13, the lower electrode 21, the electro-mechanical conversion film 16, the upper electrode 22, the film forming conditions, the orientation, and the like will be described more specifically.

  As the substrate 11, 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 used.

  When a pressure chamber such as the pressure chamber 31 shown in FIGS. 2 and 3 is manufactured, a silicon single crystal substrate is processed using etching. In this case, as an etching method, anisotropy is performed. It is common to use etching. Anisotropic etching utilizes the property that the etching rate differs with respect to the plane orientation of the 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. Accordingly, while a structure having an inclination of about 54.74 ° is produced in the plane orientation (100), a deep groove can be removed in the plane orientation (110), so that rigidity is maintained. It has been found that it is possible to increase the arrangement density. Therefore, a single crystal substrate having a (110) plane orientation can be used as this configuration. However, in this case, SiO2 which is a mask material is also etched, so this point is used with attention.

  The vibration plate 12 is deformed and displaced by receiving the force generated by the electro-mechanical conversion film 16 and discharges ink in the pressure chamber 31 as ink droplets. Therefore, it is preferable that the diaphragm 12 has a predetermined strength.

  The diaphragm 12 is manufactured by LPCVD and has a surface roughness of 4 nm or less in terms of arithmetic average roughness. When the roughness exceeds this range, the dielectric strength voltage of the PZT formed thereafter is very poor and leaks easily. Examples of the material of the diaphragm 12 include polysilicon, a silicon oxide film, a silicon nitride film, and combinations thereof, and includes at least one of a silicon oxide film and a silicon nitride film. The film itself formed by the LPCVD method is a film that has been conventionally applied to semiconductors and MEMS devices, and since it is easy to process, it does not introduce new process problems and is expensive such as SOI. A stable diaphragm can be obtained without using a substrate. The diaphragm 12 may be formed by a heat treatment film forming method.

  The diaphragm 12 is formed by forming a silicon oxide film having a thickness of 200 nm by a LPCVD method on the silicon single crystal substrate 11 having a (100) plane orientation as a diaphragm constituting film, and then by a LPCVD method. A polysilicon film was formed, and then a silicon nitride film was formed by LPCVD. The thickness of the polysilicon layer is 0.1 μm or more and 3 μm or less, and the surface roughness is 5 nm or less in terms of arithmetic average roughness.

The diaphragm 12 actually has a further nine-layer structure.
Specifically, as shown in FIG. 4, the following films are sequentially formed from the substrate 11 side toward the adhesion layer 13 side. A silicon oxide film 12a formed on the substrate 11 which is a silicon single crystal substrate by the LPCVD method or the heat treatment film forming method. A polysilicon film 12b formed on the silicon oxide film 12a by the LPCVD method. A silicon oxide film 12c formed on the polysilicon film 12b by the LPCVD method. A silicon nitride film 12d formed by LPCVD on this silicon oxide film 12c. A silicon oxide film 12e formed on the silicon nitride film 12d by the LPCVD method. A silicon nitride film 12f formed on the silicon oxide film 12e by the LPCVD method. A silicon oxide film 12g formed on the silicon nitride film 12f by the LPCVD method. A polysilicon film 12h formed on the silicon oxide film 12g by the LPCVD method. A silicon oxide film 12i formed on the polysilicon film 12h by the LPCVD method. Formation of the constituent films of the vibration plate 12 is completed by forming the respective films described above. The film thickness of each film is set so that the diaphragm 12 has desired diaphragm rigidity and stress in the entire nine layers.

  When the thermal oxide film of the vibration plate 12 is formed by the LPCDV method, the surface roughness is several tens of nanometers. Therefore, the surface roughness is reduced by stacking. However, when a conventionally known structure is formed by a general method, even if lamination is performed, the surface roughness is usually about 10 nm, and it is difficult to make it 4 nm or less. Therefore, the surface roughness of the diaphragm 12 is reduced by including a polysilicon film having a surface roughness of 5 nm or less and a thickness of 0.1 μm or more and 3 μm or less formed on the diaphragm 12 by the LPCVD method. The inventors of the present invention have developed a technique for setting the thickness to 4 nm or less.

  A method for forming a polysilicon film having a surface roughness of 5 nm or less by the LPCVD method will be described. First, an amorphous silicon film is formed by LPCVD at 600 ° C. or less, preferably 500 to 600 ° C. In order to make the amorphous silicon formed continuously into polysilicon which becomes a stable film at high temperature, in an inert gas atmosphere, for example, in argon or nitrogen, at a high temperature of 700 to 1100 ° C. for 30 minutes to 2 hours. Apply a degree of heat treatment. Thereby, a polysilicon film having a surface roughness of 5 nm or less is formed. The present inventors have newly developed such a technique as a technique for forming a polysilicon film, which is a constituent film of an inkjet diaphragm.

  The lower electrode 21 is made of a layer having (111) orientation. However, when the lower electrode 21 is configured to include the adhesion layer 13, the part or the whole excluding the adhesion layer 13 is a layer having a (111) orientation. In this regard, the lower electrode 21 includes a layer having a (111) orientation. Examples of the material of the lower electrode 21 include a metal or metal oxide containing at least one selected from Pt, Ir, IrO2, RuO2, LaNiO3, and SrRuO3 as a main component, and combinations thereof.

  Conventionally, platinum having high heat resistance and low reactivity has been used as the metal material constituting the lower electrode 21, but it may not be said that it has sufficient barrier properties against lead. Therefore, examples of the metal material constituting the lower electrode 21 include platinum group elements such as iridium and platinum-rhodium, and alloy films thereof.

  As a method for producing the lower electrode 21, vacuum film formation such as sputtering or vacuum deposition is generally used. The film thickness of the lower electrode 21 is preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm. At this time, when PZT is selected as the electromechanical conversion film 16, it is preferable that the crystallinity thereof has (111) orientation. Therefore, the material of the lower electrode 21 includes Pt having a high (111) orientation.

However, among the materials described above as the material of the lower electrode 21, it is particularly preferable to include SrRuO3 (strontium ruthenate). The reason for this is as follows.
It has been pointed out that oxygen vacancies in the piezoelectric body may increase over time during the operation of the piezoelectric body. As a supply source of the deficient oxygen component, it is preferable to use a conductive oxide electrode as a contact interface with the dielectric material. In this respect, since SrRuO3 has the same perovskite crystal structure as PZT, it has excellent bonding properties at the interface, facilitates the epitaxial growth of PZT, and has excellent characteristics as a Pb diffusion barrier layer.

  The adhesion layer 13 is provided as an intermediate layer, and is formed by laminating Ti, TiO 2, Ta, Ta 2 O 5, Ta 3 N 5 and the like before the lower electrode 21. This is because, when platinum is used for the lower electrode 21, the adhesion between the base formed by the diaphragm 12 and the lower electrode 21 is low.

  The configuration of the upper electrode 22 is not particularly limited, and examples of the material of the upper electrode 22 include materials exemplified in the lower electrode 21, materials such as Al and Cu, and materials generally used in semiconductor processes and combinations thereof.

  The electromechanical conversion film 16 is made of PZT. PZT is a solid solution of lead zirconate (PbTiO3) and titanic acid (PbTiO3), and the characteristics differ depending on the ratio. In general, the composition exhibiting excellent piezoelectric characteristics has a ratio of PbZrO3 and PbTiO3 of 53:47. When expressed by a chemical formula, Pb (Zr0.53, Ti0.47) O3 and general PZT (53/47) are shown. It is. Examples of composite oxides other than PZT include barium titanate. In this case, it is also possible to prepare a barium titanate precursor solution by dissolving barium alkoxide and a titanium alkoxide compound in a common solvent. is there.

  These materials are described by the general formula ABO3, and A = Pb, Ba, Sr, B = Ti, Zr, Sn, Ni, Zn, Mg, and complex oxides whose main components are applicable. The specific description is (Pb1-x, Ba) (Zr, Ti) O3, (Pb1-x, Sr) (Zr, Ti) O3, which is obtained by partially replacing Pb of the A site with Ba or Sr. Is the case. Such substitution is possible with a divalent element, and the effect thereof has an effect of reducing characteristic deterioration due to evaporation of lead during heat treatment.

  As a manufacturing method, it is possible to manufacture 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 PZT is produced by the Sol-gel method, lead acetate, zirconium alkoxide, and titanium alkoxide compounds are used as starting materials and dissolved in methoxyethanol as a common solvent to obtain a uniform solution, thereby producing a PZT precursor solution. The Since the metal alkoxide compound is easily hydrolyzed by moisture in the atmosphere, an appropriate amount of a stabilizer such as acetylacetone, acetic acid or diethanolamine 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.

  Further, in the case of manufacturing by the inkjet method, it is possible to obtain a film patterned by the same manufacturing flow as that of the lower electrode 21. As for the surface modifying material, although it varies depending on the material of the lower electrode 21 which is a base, mainly a silane compound is selected when an oxide is a base, and alkanethiol is mainly selected when a metal is a base.

  The film thickness of the electromechanical conversion film 16 is preferably 0.5 to 5 μm, more preferably 1 μm 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.

  FIG. 5 shows XRD after forming 1 μm of PZT on the lower electrode 21 by spin coating using a solution prepared by the Sol-gel method. From the figure, it can be seen that PZT has a film in which the (111) plane is highly preferentially oriented. In addition, depending on the heat treatment conditions of PZT, it is an orientation film other than (111). When the following formula is used, the (111) orientation degree is 0.95 or more and the (110) orientation degree is 0.05. The following is preferable.

This equation shows a calculation method that represents the ratio of each orientation when the sum of the peaks of each orientation obtained by XRD is 1. The value obtained by this formula represents the average degree of orientation.
ρ = I (hkl) / ΣI (hkl)
Denominator: Total numerator of each peak intensity: Peak intensity of arbitrary orientation When exceeding this range, it was found that sufficient characteristics could not be obtained for displacement degradation after continuous driving.

  As can be seen from the above description, the electromechanical conversion element 10 can be formed by a simple manufacturing process, has performance equivalent to that of bulk ceramics, and is etched from the back surface for forming the pressure chamber 31 thereafter. By removing and joining the nozzle plate 33 having the nozzles 32, the droplet discharge head 30 can be manufactured.

Hereinafter, examples of the present invention and comparative examples compared with the examples will be described.
In these examples, the configuration of the electromechanical conversion element is the same as that shown in FIG. In addition, about the matter which is not stated in the following description, the already stated matter is used suitably.

<Example 1>
A vibration plate 12 made of a thermal oxide film having a thickness of 1 micron was formed on a silicon wafer as the substrate 11 by LPCVD. Specifically, the diaphragm 12 is formed by forming a silicon oxide film having a thickness of 200 nm by the LPCVD method, forming a polysilicon film having a thickness of 500 nm by the LPCVD method, and then forming a silicon nitride film by the LPCVD method. Was deposited. Next, an adhesion layer 13 made of a titanium film with a thickness of 50 nm was formed, then a platinum film with a thickness of 250 nm was formed by sputtering as the lower electrode 21, and an SrRuO film with a thickness of 50 nm was formed by sputtering.

Note that the platinum film and the SrRuO film constituting the lower electrode 21 are the first electrode and the second electrode in the electro-mechanical conversion element 10, respectively.
The titanium film as the adhesion layer 13 is an adhesion layer between the thermal oxide film and the platinum film.
The substrate was heated at a temperature of 550 ° C. when the SrRuO film was formed by sputtering.

  In preparing the electromechanical conversion film 16, a solution prepared with a composition ratio of Pb: Zr: Ti = 110: 53: 47 was prepared. 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. Isopropoxide titanium and isopropoxide zirconium were dissolved in methoxyethanol, followed by alcohol exchange reaction and esterification reaction, and mixed with the above-mentioned methoxyethanol solution in which lead acetate was dissolved to synthesize a PZT precursor solution. The PZT concentration was 0.5 mol / liter.

  The electro-mechanical conversion film 16 was formed by spin coating using this solution, and after film formation, 120 ° C. drying → 500 ° C. thermal decomposition was performed. After the thermal decomposition treatment of the third layer, crystallization heat treatment at a temperature of 750 ° C. was performed by RTA which is rapid heat treatment. At this time, the film thickness of PZT was 240 nm. This process was performed 8 times in total, and a PZT film thickness of about 2 μm was obtained with 24 layers.

  Next, a 40 nm thick SrRuO film and a 125 nm thick Pt film were formed by sputtering as the upper electrode 22. The SrRuO film and the Pt film constituting the upper electrode 22 are the third electrode and the fourth electrode in the electro-mechanical conversion element 10, respectively.

  Thereafter, a photoresist (TSMR8800) manufactured by Tokyo Ohka Co., Ltd. was formed by spin coating, a resist pattern was formed by ordinary photolithography, and then a pattern was prepared using an ICP etching apparatus (manufactured by Samco).

Thereafter, the silicon wafer constituting the substrate 11 was processed to form a pressure chamber 31 and a nozzle plate 33 having nozzles 32.
The electromechanical conversion element 10 was produced as described above.

<Example 2>
The electromechanical conversion element 10 was produced in the same manner as in Example 1 except that the diaphragm configuration of the diaphragm 12 by the LPCVD method was changed and the surface roughness was changed to the conditions shown in Table 1 (a).

<Example 3>
The electromechanical conversion element 10 was produced in the same manner as in Example 1 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and no SrRuO film was formed.

<Example 4>
The electromechanical conversion element 10 was produced in the same manner as in Example 2 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and no SrRuO film was formed.

<Example 5>
The electromechanical conversion element 10 was produced in the same manner as in Example 1 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to an Ir film.

<Example 6>
The electromechanical conversion element 10 was produced in the same manner as in Example 2 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to an Ir film.

<Example 7>
The electromechanical conversion element 10 was produced in the same manner as in Example 1 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to an IrO 2 film.

<Example 8>
The electromechanical conversion element 10 was produced in the same manner as in Example 2 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to an IrO 2 film.

<Example 9>
The electromechanical conversion element 10 was produced in the same manner as in Example 1 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to a RuO 2 film.

<Example 10>
The electromechanical conversion element 10 was produced in the same manner as in Example 2 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to a RuO2 film.

<Example 11>
The electromechanical conversion element 10 was produced in the same manner as in Example 1 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to a LaNiO 3 film.

<Example 12>
The electromechanical conversion element 10 was produced in the same manner as in Example 2 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to a LaNiO 3 film.

<Comparative Example 1>
An electromechanical conversion element was produced in the same manner as in Example 1 except that the diaphragm configuration of the diaphragm 12 by the LPCVD method was changed and the surface roughness was changed to the conditions shown in Table 1 (a).

<Comparative example 2>
An electromechanical conversion element was produced in the same manner as in Example 1 except that the diaphragm configuration of the diaphragm 12 by the LPCVD method was changed and the surface roughness was changed to the conditions shown in Table 1 (a).

<Comparative Example 3>
An electro-mechanical conversion element was produced in the same manner as in Comparative Example 1 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and no SrRuO film was formed.

<Comparative example 4>
An electromechanical conversion element was produced in the same manner as in Comparative Example 1 except that the configuration of the lower electrode 21 was changed as shown in Table 1 (b) and the SrRuO film was changed to an Ir film.

  For the electromechanical transducers prepared in Examples 1 and 2 and Comparative Examples 1 and 2, the surface roughness was measured using NanoScope IIIaAFM manufactured by Beiko Japan, immediately after the diaphragm 12 was formed by LPCVD in the process. Was evaluated. This surface roughness is an average roughness. In AFM measurement, the measurement mode was tapping mode, the measurement range was 3 μm × 3 μm, and the scanning speed was 1 Hz. Electrical characteristics and electro-mechanical conversion ability (piezoelectric constant) were evaluated using the produced electro-mechanical conversion element. A typical PE hysteresis curve is shown in FIG. The electro-mechanical conversion ability was calculated from the amount of deformation due to electric field application (150 kV / cm) measured by a laser Doppler vibrometer and adjusted by simulation. After evaluating the initial characteristics, durability (characteristics immediately after applying the applied voltage 10 ^ 10 times) was evaluated.

These detailed results are summarized in Table 1 (a).
In the table, the numerical values in the thick frame indicate that the characteristics are inferior. For items for which no numerical value is indicated in the bold frame, the case where evaluation is impossible during the test is shown.

  About Example 1, 2, and the comparative example 1, it had the characteristic equivalent to the general ceramic sintered compact also about the initial characteristic and the result after a durability test. For example, the residual polarization Pr is in the range of 20 to 25 μC / cm 2 and the piezoelectric constant d31 is in the range of −130 to −160 pm / V.

  On the other hand, in Comparative Example 2, the initial characteristics are inferior in both residual polarization Pr and piezoelectric constant d31 as compared with a general ceramic sintered body. Further, after 10 ^ 10 times, i.e., the durability test in which the applied voltage was repeatedly applied 10 ^ 10 times, in other words, in the characteristic immediately after the deterioration test, the comparative example 2 is different from the first and second examples in the residual polarization Pr and the piezoelectric constant d31. In both cases, it was confirmed that the electrode was deteriorated, electrode leakage occurred during the deterioration test, and evaluation could not be performed on the way.

  From comparison of such characteristics between Examples 1 and 2 and Comparative Example 1 and Comparative Example 2, regarding the electrical characteristics of the electromechanical conversion film 10, 2Pr value is obtained in the PE hysteresis at 150 kV / cm. It has been found that it is preferably 35 μC / cm 2 or more.

  Using the electro-mechanical transducers produced in Examples 1 and 2 and Comparative Example 1, the droplet ejection head 30 shown in FIG. 3 was produced and the ejection of the liquid was evaluated. Using an ink whose viscosity was adjusted to 5 cp, the discharge situation when applying an applied voltage of −10 to −30 V was confirmed by a simple Push waveform, and it was confirmed that all the nozzle holes were discharging.

  However, with respect to the deterioration rate of the droplet velocity Vj after the durability test in the same table (a), in the vj characteristics immediately after the durability test in which the applied voltage was applied 10 ^ 10 times, that is, 10 ^ 10 times repeatedly, Example 1 Compared to 2, Comparative Example 1 was confirmed to be deteriorated by 10% or more, was inferior in durability, and judged to be NG.

Next, using the electro-mechanical conversion elements produced in Examples 3 to 12 and Comparative Examples 3 and 4, the droplet ejection head 30 shown in FIG. 3 was produced and the ejection of the liquid was evaluated. Specifically, it is as follows.
Using an ink whose viscosity was adjusted to 5 cp, the discharge situation when applying an applied voltage of −10 to −30 V was confirmed by a simple Push waveform, and it was confirmed that all the nozzle holes were discharging.

  Table (b) shows the deterioration rate of the droplet velocity Vj after the durability test in this case. In the Vj characteristics immediately after the durability test after applying the applied voltage 10 ^ 10 times after 10 ^ 10 times, compared with Examples 3-12, Comparative Examples 3 and 4 are degraded by 10% or more. Was confirmed, it was inferior in durability, and judged to be NG.

  An example of an ink jet recording apparatus which is an image forming apparatus in which the droplet discharge head 30 is mounted as an ink jet recording head will be described with reference to FIG. 2A is a side view of the mechanism portion of the recording apparatus, and FIG. 2B is a perspective view of the recording apparatus.

  The ink jet recording apparatus 50 is a digital printing apparatus that is a printer as an ink jet printer and can perform full color image formation. The ink jet recording apparatus 50 performs an image forming process based on an image signal corresponding to image information received from the outside.

  The ink jet recording apparatus 50 can form an image on a sheet-like recording medium using not only plain paper generally used for copying, but also OHP sheets, cardboard, postcards and other thick paper, envelopes, and the like. It is. The inkjet recording apparatus 50 is a single-sided image forming apparatus that can form an image on one side of a transfer sheet S that is a recording medium as a recording medium, but is a double-sided image forming apparatus that can form an image on both sides of the transfer sheet S. There may be.

  The ink jet recording apparatus 50 includes a carriage 93 that can move in the main scanning direction, a liquid droplet ejection head 30 that is a recording head as an ink jet head mounted on the carriage 93, and a liquid droplet ejection head 30. A printing mechanism 82 serving as a droplet discharge device having an ink cartridge 95 serving as a liquid supply unit for supplying ink to the ink is accommodated.

  In the ink jet recording apparatus 50, a sheet feeding cassette 84 on which a large number of sheets 83 can be stacked from the front side is detachably attached to a lower portion of a main body 81. The main body 81 can turn over a manual feed tray 85 for manually feeding the paper 83. The paper feed cassette 84 may be a paper feed tray.

  The ink jet recording apparatus 50 takes in the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85, records a required image by the printing mechanism unit 82, and then discharges the paper onto a paper discharge tray 86 mounted on the rear side. To do.

  The printing mechanism 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown). In the carriage 93, a droplet discharge head 30 that discharges ink of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) crosses the plurality of nozzles 32 with the main scanning direction. The ink droplets are mounted with the ink droplet ejection direction downward. In addition, an ink cartridge 95 for supplying ink of each color to each of the droplet discharge heads 30 is mounted on the carriage 93 in a replaceable manner.

  The ink cartridge 95 has an air port (not shown) that communicates with the atmosphere above and an ink port (not shown) that supplies ink to the droplet discharge head 30 below, and is filled with ink (not shown). The ink has a porous body, and the ink supplied to the droplet discharge head 30 is maintained at a slight negative pressure by the capillary force of the porous body. Although a plurality of droplet discharge heads 30 of this configuration are provided corresponding to each color, the droplet discharge head 30 may be configured to discharge ink of each color, and one may be provided.

  The carriage 93 is slidably fitted to the main guide rod 91 on the downstream side in the paper conveyance direction corresponding to the rear side, and is slidably mounted on the secondary guide rod 92 on the upstream side in the paper conveyance direction corresponding to the front side. ing. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 to which the carriage 93 is fixed is stretched between a driving pulley 98 and a driven pulley 99 that are rotationally driven by the main scanning motor 97. The carriage 93 is driven to reciprocate by forward and reverse rotation.

  The inkjet recording apparatus 50 includes a paper feed roller 101 and a friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84 in order to transport the paper 83 set in the paper feed cassette 84 to the lower side of the droplet discharge head 30. A guide member 103 that guides the paper 83, a transport roller 104 that reverses and transports the fed paper 83, a transport roller 105 that is pressed against the peripheral surface of the transport roller 104, and a paper 83 from the transport roller 104. And a tip roller 106 for defining the feed angle of the head. The transport roller 104 is rotationally driven by a sub-scanning motor 107 via a gear train (not shown).

  Below the droplet discharge head 30 is a sheet guide member that guides the sheet 83 fed from the transport roller 104 corresponding to the range of movement of the carriage 93 in the main scanning direction on the lower side of the droplet discharge head 30. A copying member 109 is provided. A conveyance roller 111 and a spur 112 that are rotationally driven to send the paper 83 in the paper discharge direction are provided on the downstream side of the printing receiving member 109 in the paper conveyance direction, and the paper 83 is further delivered to the paper discharge tray 86. A roller 113 and a spur 114, and guide members 115 and 116 that form a paper discharge path are disposed.

  During recording, the droplet discharge head 30 is driven in accordance with the image signal while moving the carriage 93, thereby ejecting ink onto the stopped sheet 83 to record one line, and conveying the sheet 83 by a predetermined amount. After that, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

  A recovery device 117 for recovering defective ejection of the droplet ejection head 30 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 93. Although not shown, the recovery device 117 has a cap unit, a suction unit, and a cleaning unit. While waiting for printing, the carriage 93 is moved to the recovery device 117 side and the droplet discharge head 30 is capped by the capping unit, and the discharge port portion is kept in a wet state to prevent 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.

  When a discharge failure occurs, the nozzle 32 of the droplet discharge head 30 is sealed with a capping unit, and bubbles and the like are sucked out from the nozzle 32 with a suction unit through a tube (not shown) and adhered to the surface of the nozzle plate 33. Ink, dust, etc. are removed by the cleaning means, and the ejection failure is recovered. The sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body 81 and absorbed and held by an ink absorber inside the waste ink reservoir.

  In the ink jet recording apparatus 50 having such a configuration, the droplet discharge head 30 is mounted, and the droplet discharge head 30 is obtained by optimizing the surface roughness of the electro-mechanical conversion element 10, that is, the diaphragm 12. By providing the electro-mechanical conversion element 10 in which the crystal orientation of the lower electrode 21 and the electro-mechanical conversion film 16 is optimized, ink ejection characteristics can be stably obtained over time and ink droplet ejection defects can be prevented. Or suppressed, and good image quality can be obtained.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments, and the present invention described in the claims is not specifically limited by the above description. Various modifications and changes are possible within the scope of the above.

  For example, the electro-mechanical conversion element has at least the base film, the lower electrode, the electro-mechanical conversion film, and the upper electrode among the substrate, the base film, the adhesion layer, the lower electrode, the electro-mechanical conversion film, and the upper electrode. In addition to this, an adhesion layer and / or a substrate may be provided.

  The image forming apparatus to which the present invention is applied is not limited to the above-mentioned type of image forming apparatus, but other types of image forming apparatuses, that is, a copying machine, a single facsimile, a complex machine of these, a monochrome machine related thereto, and the like. The image forming apparatus may be a multifunction peripheral, an image forming apparatus used for forming an electric circuit, or an image forming apparatus used for forming a predetermined image in the biotechnology field.

  The application range of the electro-mechanical conversion element is not limited to the image forming apparatus. However, even when the electro-mechanical conversion element is applied to the image forming apparatus, the electro-mechanical conversion element is provided as an actuator in a portion different from the droplet discharge head in the image forming apparatus. It may be done. The electro-mechanical conversion element can be applied to a three-dimensional molding technique using an inkjet technique.

  The effects described in the embodiments of the present invention are only the most preferable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. is not.

DESCRIPTION OF SYMBOLS 10 Electro-mechanical conversion element 11 Board | substrate 12 Diaphragm 16 Electro-mechanical conversion film 21 Lower electrode 22 Upper electrode 30 Droplet discharge head 50 Image forming apparatus 82 Droplet discharge apparatus 95 Liquid supply part

JP 2004-186646 A JP 2004-262253 A JP 2003-218325 A JP 2007-258389 A JP 2005-144918 A JP 2004-262253 A Japanese Patent No. 4091641 JP 2009-054994 A Japanese Patent No. 45198110 JP 2010-045152 A Japanese Patent No. 4100553 JP-A-10-264385 JP 2003-309303 A JP 2004-214308 A JP 2002-134806 A JP 2004-237676 A JP 2000-196157 A JP 2008-094019 A JP 2009-285886 A

Claims (8)

A diaphragm formed on a substrate;
A lower electrode formed directly or indirectly on the diaphragm;
An electro-mechanical conversion film formed on the lower electrode;
An upper electrode formed on the electro-mechanical conversion film,
The lower electrode includes a layer having a (111) orientation,
The electro-mechanical conversion film is made of PZT with a preferred orientation of (111),
The diaphragm is an electromechanical conversion element including a polysilicon layer having a surface roughness of 5 nm or less. The electro-mechanical transducer according to claim 1,
The diaphragm has a surface roughness of 4 nm or less and a thickness of the polysilicon layer of 0.1 μm to 3 μm. The electro-mechanical conversion element according to claim 1 or 2,
Regarding the crystal orientation of the electro-mechanical conversion film,
ρ = I (hkl) / ΣI (hkl)
[I (hkl): peak intensity of arbitrary orientation, ΣI (hkl) sum of each peak intensity]
In the average orientation degree by the calculation direction representing the ratio of the respective orientations when the sum of the peaks of the respective orientations obtained by XRD is 1 represented by
An electro-mechanical transducer having an orientation degree of (111) orientation of 0.95 or more and an orientation degree of (110) orientation of 0.05 or less. The electromechanical conversion element according to any one of claims 1 to 3,
Regarding the electrical characteristics of the electro-mechanical conversion film, the 2Pr value is 35 μC / cm 2 or more in the PE hysteresis at 150 kV / cm. The electromechanical conversion element according to any one of claims 1 to 4,
The electro-mechanical conversion element, wherein the diaphragm includes at least one of a silicon oxide film and a silicon nitride film.   A liquid droplet ejection head comprising the electro-mechanical conversion element according to claim 1 and ejecting liquid droplets by driving the electro-mechanical conversion element.   7. A droplet discharge apparatus comprising: the droplet discharge head according to claim 6; and a liquid supply unit that supplies a liquid that becomes a droplet to the droplet discharge head.   An image forming apparatus comprising the electro-mechanical conversion element according to claim 1, the droplet discharge head according to claim 6, or the droplet discharge device according to claim 7.

Images