JP7167626B2 - Actuator, liquid ejection head, liquid ejection unit, and apparatus for ejecting liquid - Google Patents

Description

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

2. Description of the Related Art In the field of industrial and commercial printing, there is a demand for a liquid ejection head and a liquid ejection device that are highly productive, such as being capable of high-frequency driving.

Specific examples of the liquid ejection head and the liquid ejection device include nozzles for ejecting liquid, pressurizing chambers (also referred to as individual liquid chambers) communicating with the nozzles, and a vibration plate forming a part of the pressurizing chambers. and an electro-mechanical conversion element such as a piezoelectric element for pressurizing the ink in the pressurizing chamber. In this case, the liquid is ejected from the nozzle by pressurizing the liquid in the pressure chamber with the electro-mechanical transducer.

It is important to increase the rigidity of the diaphragm as one means of achieving high-frequency driving. Specifically, rigidity is ensured by increasing the thickness of the diaphragm. There is a technique using an SOI wafer as the diaphragm material.
However, increasing the rigidity of the diaphragm by increasing its thickness reduces the amount of deformation when a force is applied, resulting in a problem of poor ejection efficiency.

In Patent Document 1, SOI is used as the diaphragm, first and second silicon oxide films are formed on the front and back surfaces of the diaphragm made of silicon, and the thickness of the diaphragm is 2 μm or more and 20 μm or less. It is disclosed that the thickness of the first and second silicon oxide films is 0.5 μm or more and 2.0 μm or less.
However, in Patent Document 1, although the rigidity of the diaphragm is increased, no consideration has been given to increasing the amount of deformation of the diaphragm, and good ejection efficiency has not been obtained. In addition, displacement characteristics deteriorate with time.

In Patent Document 2, a diaphragm is formed by a laminated film including at least one monolayer film having compressive stress, and the bending rigidity of the diaphragm and the stress of each monolayer film constituting the diaphragm are set to predetermined values. is disclosed. Japanese Patent Laid-Open No. 2002-200000 aims to ensure ejection performance at high frequencies.
However, since sufficient diaphragm rigidity is not obtained in Patent Document 2, it is desired to improve the ejection efficiency in high-frequency driving and at the same time increase the diaphragm rigidity.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an actuator with good initial and temporal displacement characteristics and good ejection characteristics.

In order to solve the above problems, the actuator of the present invention has a diaphragm, a lower electrode, an electro-mechanical conversion film and an upper electrode, the diaphragm comprising a first silicon oxide film having a thickness of 0.5 μm or more, A silicon layer having a thickness of 3 μm or more is formed on the first silicon oxide film, and a second silicon oxide film having a thickness of 0.5 μm or more is formed on the silicon layer, and the silicon layer has a volume resistivity of 10 ³ Ω. · cm or more and 10 ⁶ Ω·cm or less.

According to the present invention, it is possible to provide an actuator with good initial and temporal displacement characteristics and good ejection characteristics.

1 is a cross-sectional view of an example of an actuator according to the present invention; FIG. FIG. 4 is another cross-sectional view of an example of an actuator according to the present invention; FIG. 4 is a diagram plotting an example of the relationship between stress and displacement of a diaphragm. FIG. 3 is a diagram plotting an example of the relationship between the resistance of the silicon layer (active layer), the stress of the diaphragm, and the thickness of the second silicon oxide film (surface layer). FIG. 4 is a cross-sectional view of another example of an actuator according to the present invention; FIG. 4 is a cross-sectional view of another example of an actuator according to the present invention; FIG. 4 is a cross-sectional view of another example of an actuator according to the present invention; FIG. 4 is a cross-sectional view of another example of an actuator according to the present invention; FIG. 4 is a diagram showing an example of XRD (X-ray diffraction) measurement results of an electro-mechanical conversion film; FIG. 4 is a diagram showing an example of XRD measurement results of an electro-mechanical conversion film; FIG. 4 is a diagram showing an example of the relationship between the number of peaks and fitting residue when performing peak separation and fitting on XRD measurement results of an electro-mechanical conversion film. FIG. 2A is a schematic diagram showing an example of the crystal structure of an electro-mechanical conversion film, and FIG. 2B is a diagram showing an example of XRD measurement results of the electro-mechanical conversion film. It is sectional drawing (a) and top view (b) in the other example of the actuator which concerns on this invention. It is a perspective view which shows an example of a polarization processing apparatus. Examples of PE hysteresis loops (a) and (b). FIG. 3 is a schematic diagram for explaining corona discharge; 1 is a schematic diagram showing an example of an apparatus for ejecting liquid according to the present invention; FIG. FIG. 4 is a schematic diagram showing another example of a device for ejecting liquid according to the present invention; 1 is a schematic diagram showing an example of a liquid ejection unit according to the present invention; FIG. FIG. 5 is a schematic diagram showing another example of the liquid ejection unit according to the present invention; FIG. 4 is a perspective view of another example of the device for ejecting liquid according to the present invention; FIG. 4 is a side view of another example of the device for ejecting liquid according to the present invention;

An actuator, a liquid ejection head, a liquid ejection unit, and an apparatus for ejecting liquid according to the present invention will be described below with reference to the drawings. In addition, the present invention is not limited to the embodiments shown below, and can be changed within the scope of those skilled in the art, such as other embodiments, additions, modifications, deletions, etc. is also included in the scope of the present invention as long as the functions and effects of the present invention are exhibited.

INDUSTRIAL APPLICABILITY The present invention can be used in the field of printing such as digital printing, for example, and is applicable to inkjet printers, digital printing apparatuses using MFPs, office and personal printers, MFPs, and the like. In addition, it can be applied to three-dimensional molding technology using inkjet technology.

(actuator, liquid ejection head)
The actuator of the present invention has a diaphragm, a lower electrode, an electro-mechanical conversion film and an upper electrode, and the diaphragm comprises a first silicon oxide film having a thickness of 0.5 μm or more, and a silicon oxide film on the first silicon oxide film. It has a silicon layer with a thickness of 3 μm or more, and a second silicon oxide film with a thickness of 0.5 μm or more on the silicon layer, and the silicon layer has a volume resistivity of 10 ³ Ω·cm or more and 10 ⁶ Ω·cm or less. It is characterized by

<First Embodiment>
An embodiment of an actuator according to the present invention will be described below. FIG. 1 shows a cross-sectional view of the actuator of this embodiment. In FIG. 1, a substrate 11, a diaphragm 12, a lower electrode 13, an electro-mechanical conversion film 14, and an upper electrode 15 are illustrated. In this embodiment, the lower electrode 13, the electro-mechanical conversion film 14, the upper electrode 15, and the like are formed on the substrate 11 one by one by etching or the like.
Details will be described below. The details of the substrate, the lower electrode, the upper electrode, and the diaphragm are mainly described here, and the electro-mechanical conversion film and other configurations will be described in later embodiments.

<<Substrate>>
As the substrate 11, it is preferable to use a silicon single crystal substrate, and it is preferable to have a thickness of 100 to 600 μm. There are three plane orientations, (100), (110), and (111). In general, (100) and (111) are widely used in the semiconductor industry. ) can be used.

<<lower electrode, upper electrode>>
As the metal material for the lower electrode 13 and the upper electrode 15, platinum having high heat resistance and low reactivity can be used. However, platinum may not have sufficient barrier properties against lead, in which case platinum group elements such as iridium, platinum-rhodium, and alloy films thereof can be used. .

When platinum is used as the lower electrode 13 and the upper electrode 15, Ti, TiO ₂ , Ta, Ta ₂ O ₅ and Ta are used in consideration of adhesion to the underlying vibration plate 12 (especially SiO ₂ ). It is preferable to laminate via an _adhesion layer such as _3N5 . As a method for producing the lower electrode 13 and the upper electrode 15, vacuum film formation such as a sputtering method or vacuum deposition can be used. The film thickness of the lower electrode 13 and the upper electrode 15 is preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm.

Furthermore, in the lower electrode 13 and the upper electrode 15, an oxide electrode film made of SrRuO ₃ or LaNiO ₃ may be formed between the metal material and the electro-mechanical conversion film 14. FIG. Note that the oxide electrode film between the lower electrode 13 and the electro-mechanical conversion film 14 affects the orientation control of the electro-mechanical conversion film 14 (eg, PZT film) formed thereon. The material selected depends on the desired orientation.

<<Diaphragm>>
The diaphragm 12 of this embodiment is constructed using SOI (Silicon on Insulator). FIG. 2 shows the diaphragm 12 of this embodiment. FIG. 2 is a cross-sectional view showing the diaphragm 12 in FIG. 1 in more detail. A substrate 11, a first silicon oxide film 20, a silicon layer 21, and a second silicon oxide film 22 are shown from the bottom. function as

For high-frequency driving, it is preferable to make the diaphragm as thick as possible and to increase its rigidity. However, if the thickness of the diaphragm is increased and the rigidity is increased, the amount of deformation when a force is applied is reduced, resulting in a problem of poor discharge efficiency.
As a result of extensive studies, the inventors have found that by controlling the stress of the entire diaphragm to the compression side, the tensile stress of the electro-mechanical conversion film can be reduced, the strain (displacement amount) is improved, and the rigidity is secured. It was found that the ejection efficiency can be improved.

The relationship between stress and displacement of the diaphragm will be described with reference to FIG. Figure 3 plots the stress of the diaphragm on the horizontal axis and the displacement of the diaphragm on the vertical axis for multiple samples in which the stress of the diaphragm is distributed to the compression side and the tension side after the rigidity of the diaphragm is the same. It is what I did. As shown in (C) in the figure, when the stress of the diaphragm is tensile stress, good displacement cannot be obtained. Further, as shown in (B) in the figure, when the stress of the diaphragm is on the compressive stress side, the displacement is improved. Then, as shown in (A) in the figure, when the stress of the diaphragm is on the compressive stress side and is within a predetermined range, the displacement is further improved. This embodiment aims at (A) in the figure, and can improve the ejection efficiency while securing the rigidity.

In this embodiment, an SOI wafer is used as a diaphragm material to increase the rigidity of the diaphragm, and at the same time, the first silicon oxide film, the silicon layer, and the second silicon oxide film have predetermined thicknesses, and the thickness of the silicon layer is increased. The stress is reduced to be the stress on the compression side. As a result, the stress of the diaphragm as a whole can be controlled to the compressive side, the tensile stress of the electro-mechanical conversion film can be reduced, the amount of displacement can be improved, and the ejection efficiency can be improved. As a result of a further detailed study, it was found that it is important to set the resistance value of the silicon layer 21 in the diaphragm to a predetermined value in order to control the stress of the diaphragm as a whole to the compressive side.
Details will be described below.

- First silicon oxide film -
The first silicon oxide film 20 is also called a Box layer and functions as a buried oxide film. The first silicon oxide film 20 preferably has compressive stress. The thickness of the first silicon oxide film 20 is 0.5 μm or more, preferably 1 μm or more. When the thickness is 0.5 μm or more, it becomes possible to control the entire diaphragm to the compression side. Also, the thickness of the first silicon oxide film 20 is preferably 8 μm or less.

- Second silicon oxide film -
The second silicon oxide film 22 is also called a surface layer and is an oxide film obtained by oxidizing the silicon layer 21 . The second silicon oxide film 22 preferably has compressive stress. The thickness of the second silicon oxide film 22 is 0.5 μm or more, preferably 2 μm or more. When the thickness is 0.5 μm or more, it becomes possible to control the entire diaphragm to the compression side. Also, the thickness of the second silicon oxide film 22 is preferably 8 μm or less.

The function of the second silicon oxide film 22 is to form a crystalline film with a very high degree of (100) orientation when the lower electrode 13 and the electro-mechanical conversion film 14 formed thereon are PZT films. Also serves as By setting the thickness of the second silicon oxide film 22 to 0.5 μm or more, it becomes easy to obtain a film with a high degree of (100) orientation of the lower electrode and PZT.

Moreover, the thickness of the second silicon oxide film 22 is preferably equal to or greater than the thickness of the first silicon oxide film 20 . In this case, it becomes easier to control the entire diaphragm to the compression side, and it is possible to further increase the rigidity of the diaphragm.

-Silicon layer-
The silicon layer 21 is also called an active layer and has a thickness of 3 μm or more. By setting the thickness to 3 μm or more, it is possible to increase the rigidity of the diaphragm. Moreover, it is more preferably 5 μm or more, and in this case, the ejection characteristics can be further improved. Also, the thickness of the silicon layer 21 is preferably 12 μm or less, more preferably 8 μm or less.

By reducing the stress of the silicon layer 21 to within a predetermined range, the stress of the diaphragm as a whole can be controlled to the compressive side. In order to reduce the stress in the silicon layer 21, it is important to set the resistance value of the silicon layer 21 to a predetermined value.

FIG. 4 is a diagram for explaining the relationship between the resistance of the silicon layer 21 and the stress of the diaphragm. FIG. 4 plots the measurement results of several samples, with the horizontal axis representing the resistance of the silicon layer 21 and the vertical axis representing the stress of the diaphragm. The upper side of the vertical axis is the compressive stress side and the lower side is the tensile stress side. As for the stress value, when the value is small, the stress is on the compressive stress side, so it is positioned above the vertical axis, and when the value is large, it is on the tensile stress side, so it is on the lower side of the vertical axis. Located in

In FIG. 4, a1 to a4 are samples when the thickness of the second silicon oxide film 22 (surface layer) is thick (about 2 μm), and b1 to b4 are the thickness of the second silicon oxide film 22 (surface layer). This sample is thin (about 0.3 μm). In addition, in the samples a1 to a4 and b1 to b4 in the figure, the rigidity of the diaphragm is the same.

First, when a1 to a4 and b1 to b4 are compared, by increasing the thickness of the second silicon oxide film 22, the stress of the diaphragm becomes compressive. Considering a1 to a4 or b1 to b4, by increasing the resistance of the silicon layer 21, the stress of the silicon layer 21 is reduced and the stress of the silicon layer 21 on the compression side is increased. As a result, the stress on the compression side of the diaphragm increases.

For this reason, by increasing the thickness of the second silicon oxide film 22 (surface layer) and controlling the silicon layer 21 to a high resistance side, the stress of the silicon layer 21 itself can be reduced, and the entire diaphragm can be controlled. Can be adjusted on the compression side. Displacement can be increased by adjusting the entire diaphragm to the compression side. By adjusting in this way, a1 is targeted in this embodiment.
Incidentally, in obtaining the plot of FIG. 4, it is determined that the diaphragm has a compressive stress from the wafer warp amount of the diaphragm.

Si (silicon) itself has a slight tensile stress, but a silicon oxide film has a compressive stress. For this reason, the resistance of the silicon layer 21 is increased, the stress is reduced, and the first silicon oxide film 20 and the second silicon oxide film 22 are made thicker than a predetermined thickness, thereby compressing the entire diaphragm. side can be controlled.

The volume resistivity of the silicon layer 21 must be 10 ³ Ω·cm or more and 10 ⁶ Ω·cm or less. When the resistance is 10 ³ Ω·cm or more, the stress of the silicon layer 21 is reduced, and the stress of the entire diaphragm can be controlled to the compression side. If it is less than 10 ³ Ω·cm, good piezoelectric properties and ejection properties cannot be obtained. If it is larger than 10 ⁶ Ω·cm, the polarization does not proceed well when the polarization treatment is performed, and the deterioration of the characteristics in the subsequent continuous driving endurance is affected.
Moreover, the volume resistivity of the silicon layer 21 is preferably 10 ⁴ Ω·cm or more.
The volume resistivity of the silicon layer 21 is measured using a resistivity meter such as a four-probe method.

As a method for setting the volume resistivity of the silicon layer 21 within the above range, it is effective to control the concentration of the additive (impurity) in the silicon layer 21 within an appropriate range. The impurity concentration in the silicon layer 21 is proportional to the volume resistivity of the silicon layer 21, and by controlling the impurity concentration in an appropriate range, the stress of the diaphragm can be controlled and the stress of the diaphragm can be controlled. Rigidity can be increased.

The silicon layer 21 may be made of, for example, p-type silicon or n-type silicon.
When using p-type silicon, for example, B or the like is doped as an impurity. In the case of p-type silicon, the impurity concentration is preferably 1.3×10 ¹³ atoms/cm ³ or less, more preferably 1.3×10 ¹² atoms/cm ³ or less. Since the resistance of the silicon layer 21 also affects the impurity concentration, when the impurity concentration satisfies the above preferable range, the volume resistivity of the silicon layer 21 can be easily set within the above range.
In addition, the lower limit is preferably 1.3×10 ¹⁰ atoms/cm ³ or more. In this case, the polarization treatment can be performed better, and deterioration of characteristics during continuous driving durability can be suppressed.

When using n-type silicon, for example, As, P, or the like is doped as an impurity. In the case of n-type silicon, the impurity concentration is preferably 4.3×10 ¹² atoms/cm ³ or less, more preferably 4.3×10 ¹¹ atoms/cm ³ or less. Since the resistance of the silicon layer 21 also affects the impurity concentration, when the impurity concentration satisfies the above preferable range, the volume resistivity of the silicon layer 21 can be easily set within the above range.
In addition, the lower limit is preferably 4.3×10 ⁹ atoms/cm ³ or more. In this case, the polarization treatment can be performed more favorably, and deterioration of characteristics during continuous driving durability can be suppressed.

Impurity concentration can be measured by ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) analysis or SIMS (Secondary Ion Mass Spectrometry) analysis.

-Bending stiffness-
In this embodiment, the bending rigidity of the diaphragm is preferably 7.0×10 ⁻¹⁰ Nm ² or more, more preferably 5.0×10 ⁻⁹ Nm ² or more. When the above range is satisfied, drive ejection at a high frequency can be performed more satisfactorily. In this embodiment, the flexural rigidity of the diaphragm is obtained from the film thickness, Young's modulus, and Poisson's ratio of each layer of the diaphragm.

-Thickness of Diaphragm-
The thickness of diaphragm 12 is preferably 8 μm or more, more preferably 10 μm or more. When the thickness is 8 μm or more, ejection characteristics can be improved. Further, the thickness of diaphragm 12 is preferably 20 μm or less.

<Second embodiment>
Another embodiment of the actuator according to the present invention will be described with reference to FIG. Descriptions of matters common to the above embodiment will be omitted. FIG. 5 is a cross-sectional view similar to FIG. In this embodiment, a stress control layer 16 is formed between the diaphragm 12 and the lower electrode 13 . That is, the stress control layer 16 is formed on the SOI diaphragm. The stress control layer 16 is made of a material having a compressive stress. When the stress control layer 16 is provided, when the diaphragm is viewed from the first silicon oxide film 20 to the stress control layer 16 as a whole, the diaphragm is compressed. It can be controlled on the compression side.

The stress control layer 16 is not particularly limited as long as it is a material having compressive stress, and examples thereof include oxide electrodes such as ZrO ₂ , SiO ₂ , poly-Si and LaNiO ₃ . Among these, _ZrO2 is preferred.
The film thickness is preferably 50 nm or more, more preferably 100 nm or more. By setting the thickness to 50 nm or more, it becomes easier to control the stress of the entire diaphragm.

<Third Embodiment>
Another embodiment according to the present invention will be described with reference to FIGS. 6 and 7. FIG. Descriptions of matters common to the above embodiment will be omitted. 6 shows one electro-mechanical conversion element 19, and FIG. 7 shows a plurality of electro-mechanical conversion elements 19. As shown in FIG.

In this embodiment, the substrate 11 has the individual liquid chambers 42, and the nozzle substrate 40 provided with the nozzles 41 is joined to the individual liquid chambers 42 side. The individual liquid chambers 42 are partitioned by partition walls 43, which are made of Si in this embodiment.

Moreover, in the present embodiment, the volume resistivity of the partition walls 43 is preferably 10 Ω·cm or less, more preferably 1 Ω·cm or less. The volume resistivity of the partition wall 43 affects the polarization treatment, and by satisfying the above range, the polarization treatment can be performed favorably, and the characteristics in the continuous driving endurance are improved. When the volume resistivity of the partition wall 43 is greater than 10 Ω·cm, for example, when the partition wall has a volume resistivity of 1.0×10 ⁵ , the initial displacement characteristics are good, but the displacement characteristics after endurance deteriorate. can occur.
The volume resistivity of the partition wall 43 is measured after the individual liquid chambers 42 are formed in the substrate 11 and the nozzle substrate 40 is bonded. Measurement is performed using a resistivity meter such as a four-terminal method.

Further, this embodiment shows one embodiment of the liquid ejection head, and the liquid ejection head of this embodiment includes nozzles 41 that eject liquid, individual liquid chambers 42 that communicate with the nozzles 41, and individual liquid chambers 42 that communicate with the nozzles 41. and an actuator for generating pressure in the liquid chamber 42, and the actuator is the actuator of the present invention.

Further, in this embodiment, a first insulating protective film 17 is formed on the electro-mechanical conversion element 19 as illustrated. As a result, deterioration of the electro-mechanical conversion element 19 can be suppressed.

According to this embodiment, the electro-mechanical conversion element 19 can be formed by a simple manufacturing process (and has performance equivalent to that of bulk ceramics). A liquid ejection head can be made by joining the nozzle plate 40 having 41 . Note that liquid supply means, flow paths, and fluid resistance are omitted in the figure.

<Fourth Embodiment>
Next, another embodiment according to the present invention will be described with reference to FIG. Descriptions of matters common to the above embodiment will be omitted. FIG. 8 is a cross-sectional view similar to FIG. 1, in which the lower electrode 13 and upper electrode 15 in FIG. different in that there are

As the lower electrode 13 and the upper electrode 15 in FIG. 1, it is preferable to use a metal layer that provides sufficient electrical resistance. In this case, it corresponds to the first electrode 31 and the fourth electrode 34 in this embodiment. do.

Furthermore, in order to suppress a decrease in displacement or the like when continuously driven when functioning as an actuator, the layer at the interface of the electro-mechanical conversion film 14 is a conductive oxide electrode layer. is preferred. In this embodiment, the second electrode 32 and the third electrode 33 are oxide electrode layers.
Details of each configuration in the present embodiment will be described below.

<<first electrode, fourth electrode>>
As the first electrode 31 and the fourth electrode 34, platinum, which has high heat resistance and low reactivity, has conventionally been used as a metal material. Platinum group elements such as iridium and platinum-rhodium, and their alloy films may also be mentioned.

Also, when platinum is used, it is preferable to first laminate Ti, TiO ₂ , Ta, Ta ₂ O ₅ , Ta ₃ N ₅ or the like in order to improve adhesion to the base (particularly SiO ₂ ). . Therefore, the first electrode 31 and the fourth electrode 34 may be multiple layers. For example, the first electrode 31 may be formed in multiple layers by forming Ti on the vibration plate 12, thermally oxidizing the Ti to form an adhesion layer, and further forming platinum.
Vacuum film formation such as a sputtering method or vacuum deposition is generally used as a manufacturing method.
The film thickness is preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm.

<<second electrode, third electrode>>
Examples of the second electrode 32 and the third electrode 33 include SrRuO ₃ and LaNiO ₃ .

As for the second electrode 32, the material to be selected differs depending on the direction in which the orientation is to be prioritized, since it also affects the orientation control of the PZT film formed thereon. In this embodiment, a seed layer is preferably used. The use of a seed layer facilitates preferential orientation of the PZT (100). Examples of the seed layer include LaNiO ₃ , IrO, TiO ₂ , PbTiO ₃ and the like. For example, a seed layer is formed on the first electrode 31 and then a PZT film is formed.
Also, the thickness of the second electrode 32 is preferably 20 to 200 nm.

SRO is preferably used as the third electrode 33 employed as the upper electrode.
Further, the thickness of the third electrode 33 is preferably 20 nm to 80 nm, more preferably 30 nm to 50 nm. When the thickness is 20 nm or more, initial displacement and displacement deterioration characteristics are improved.

<<Electro-mechanical conversion film>>
PZT (lead zirconate titanate) is preferably used as the electro-mechanical conversion film. PZT is a solid solution of lead zirconate (PbTiO ₃ ) and titanate (PbTiO ₃ ), and its properties differ depending on the ratio. A composition that generally exhibits excellent piezoelectric properties has a ratio of _{PbZrO 3} and _{PbTiO 3} of _53:47 . /47).

Composite oxides other than PZT include barium titanate. In this case, barium alkoxide and titanium alkoxide compounds can be used as starting materials and dissolved in a common solvent to prepare a barium titanate precursor solution.
A case where the electro-mechanical conversion film is PZT will be described below.

The composition ratio of Zr/Ti is preferably 0.40 or more and 0.55 or less, more preferably 0.45 or more and 0.53 or less when represented by Ti/(Zr+Ti). When the composition ratio of Zr/Ti is within the above range, it is possible to prevent the amount of displacement associated with rotational strain and the amount of displacement due to piezoelectric strain from becoming insufficient, resulting in an insufficient amount of displacement.

In this embodiment, when θ-2θ measurement is performed on PZT by XRD (X-ray diffraction) measurement, the degree of orientation of (100) orientation is preferably 99% or more, and (200) plane or (002) plane It is preferable that the diffraction peak shape of the (400) plane obtained when the tilt angle (χ) is swung is separated into three peaks having peaks and troughs at 2θ where the peak of the plane is obtained is the maximum peak position. .

The state of the crystal plane of PZT can be measured by the rocking curve method or measurement with tilt angle.
In the rocking curve method, the X-ray incident angle and the detector angle (2θ) are fixed at the position where the diffraction intensity in the measurement by the θ-2θ method becomes maximum, and only the angle (ω) between the sample substrate surface and the incident X-ray is is slightly changed near θ to measure the diffraction intensity.

FIG. 9 shows an example of θ-2θ measurement of PZT by XRD (X-ray diffraction) measurement. This figure shows the 2θ peak position of the PZT (200) plane. By adjusting the Zr/Ti composition ratio, the peak position and peak asymmetry of the PZT (200) plane (or (002) plane) as shown in FIG. 9 are varied.

FIG. 10 shows an example of the XRD measurement results obtained when the tilt angle (χ) is swung at 2θ where the (200) plane or (002) plane is obtained is the maximum peak position. FIG. 10 focuses on the PZT (400) plane on the high angle side, and the peak top of the (400) plane in this embodiment is around 99°.

Peak separation is performed from the XRD diffraction intensity as shown in FIG. 10 to confirm the attribution state of the crystal structure. It is preferable that the peak of the diffraction intensity has a shape in which the diffraction intensity is asymmetrical. Although the peak separation may be performed on the PZT (200) plane, it is preferably performed on the PZT (400) plane.

In the figure, it is separated into three peaks X1 to X3. In the figure, (A) is the measured value, and (B) is the value when X1 to X3 are superimposed. The difference between (A) and (B) is used as a fitting residue, and fitting is performed so that this value becomes small.
As for the fitting conditions, fitting is performed mainly on the 2θ position described in the JCPDS card information after estimating the attributed structure to some extent. When fitting is performed with the separated peak as one, the fitting is performed according to the 2θ position where the peak intensity is maximum.

FIG. 11 plots the relationship between the number of peaks separated in FIG. 10 and the fitting residue. Increasing the number of separated peaks reduces the fitting residue. A guideline for the fitting residue is 10% or less. Among them, the number of separated peaks is determined at the point of saturation to some extent. For example, when the number of wires is changed from n to n+1, the number of wires is set so that the reduction of the fitting residue is within 0.5%.

At the time of fitting, the ratios of X1 to X3 as shown in FIG. 10 will vary when repeated fitting is performed, so the average value when fitting is repeatedly performed is adopted. At this time, the value is calculated by excluding those with extremely deviated fitting and averaging them. The standard number of repetitions of fitting is about 6 to 10 times.

As a crystal structure, it preferably has the following three crystal structures. That is, two crystal structures, a tetragonal a-domain structure and c-domain structure, and one crystal structure of rhombohedral, orthorhombic, or pseudocubic (see FIG. 12 described later).

In order to confirm whether or not such three crystal structures exist, that is, to confirm whether or not there is one derived from the above crystal structure, the peak state of the crystal obtained by XRD measurement We are conducting peak separation and fitting to investigate whether there is anything that can be attributed to the peak conditions of the actually obtained crystals.

As shown in FIG. 10, the (400) plane (or (200) It is preferred that the diffraction peak shape of the plane) be separated into three peaks with peaks and valleys. When separated into three peaks, it can be said to have the above three crystal structures.

In addition, as described above, in the present embodiment, (100) preferential orientation is preferred. Crystal orientation is expressed as follows.

ρ(hkl)=I(hkl)/ΣI(hkl)
[ρ(hkl) represents the degree of orientation of the (hkl) plane orientation, I(hkl) represents the peak intensity of an arbitrary orientation, and ΣI(hkl) represents the sum of each peak intensity. ]

When the sum of the peak intensities obtained by the θ-2θ measurement by the X-ray diffraction method is 1, the degree of orientation of the (100) orientation calculated based on the ratio of the peak intensities of each orientation is 99% or more. is preferred, and 99.5% or more is more preferred. It can be said that preferential orientation is achieved when the degree of orientation is 99% or more.

FIG. 12 shows a schematic diagram of the crystal structure in the case of (100) preferential orientation (a), and the case where the diffraction intensity is measured by slightly changing only the angle (ω) between the sample substrate surface and the incident X-ray near θ. An example (b) of is shown. When the (100) orientation is given priority, structures with different aspect ratios such as a-domains and c-domains coexist. Therefore, as shown in FIG. will have Moreover, when it has a crystal plane like FIG.12(a), it is attributed to three peaks, as shown, for example in FIG.12(b).

Further, when PZT has tetragonal a-domain and c-domain, in θ-2θ measurement by XRD (X-ray diffraction) measurement of PZT, 2θ at which a peak of (200) plane or (002) plane is obtained is the maximum. At the peak position, when the diffraction peak obtained when the tilt angle (χ) is swung is peak-separated, the lattice constant is obtained for the peaks corresponding to the a-domain and c-domain of the tetragonal crystal, and the value is Assuming that the larger one is the maximum lattice constant and the smaller one is the minimum lattice constant, the ratio of the maximum lattice constant to the minimum lattice constant (maximum lattice constant/minimum lattice constant) is preferably 1.02 or more. More preferably, it is 1.03 or more.

Here, the lattice constant is calculated from the following Bragg equation.
2d x sin θ = n x λ
[d: lattice constant, θ: crystal peak position (angle between crystal plane and X-ray), λ: wavelength of X-ray, n: integer]

In FIG. 10 of this embodiment, the lattice constant obtained from the peak position (2θ) of X1 corresponds to the maximum lattice constant, and the lattice constant obtained from the peak position (2θ) of X3 corresponds to the minimum lattice constant.
The X1 or X3 peak in FIG. 10 is attributed to the a-domain or c-domain peak. In this case, X1 may be the a domain and X3 may be the c domain, or X1 may be the c domain and X3 may be the a domain.

The greater the ratio of the maximum lattice constant to the minimum lattice constant of the tetragonal a or c domain, the greater the displacement contribution due to rotational strain. Also, the greater the influence of the compressive stress from the diaphragm, the greater the ratio of maximum lattice constant/minimum lattice constant. Therefore, when the ratio of the maximum lattice constant/minimum lattice constant is 1.02 or more, the displacement contribution due to rotational strain can be increased, and the stress on the compression side of the diaphragm is increased, thereby increasing the displacement of the actuator. can be improved. Although the upper limit of the ratio of the maximum lattice constant to the minimum lattice constant is not particularly limited, it is preferably 1.06 or less.

- An example of a method for producing an electro-mechanical conversion film -
When PZT is produced by the Sol-gel method, a PZT precursor solution can be 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 homogeneous solution. .

Since the metal alkoxide compound is easily hydrolyzed by moisture in the air, an appropriate amount of stabilizer such as acetylacetone, acetic acid, diethanolamine, etc. may be added to the precursor solution.

When the PZT film is formed on the entire surface of the base, it is obtained by forming a coating film by a solution coating method such as spin coating, and then performing heat treatments such as solvent drying, thermal decomposition, and crystallization. Since the transformation from a coating film to a crystallized film is accompanied by volumetric shrinkage, it is preferable 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.

In addition, in the case of manufacturing by the inkjet method, a patterned film can be obtained in the same manufacturing flow as the second electrode 32 . Regarding the surface modifying material, although it varies depending on the material of the base of the second electrode 32 (first electrode 31), a silane compound is preferable when using an oxide as a base, and an alkanethiol when using a metal as a base. is preferred.

The film thickness of the electro-mechanical conversion film is preferably 0.5-5 μm, more preferably 1-2 μm. When it is above this range, the displacement can be improved, and when it is below this range, it is possible to prevent the process time from increasing due to the increase in the number of steps due to lamination of many layers.

<Fifth Embodiment>
Next, another embodiment according to the present invention will be described with reference to FIG. Descriptions of matters common to the above embodiment will be omitted. FIGS. 13A and 13B show an embodiment of a configuration including an insulating protective film and lead wires, FIG. 13A is a schematic cross-sectional view, and FIG. 13B is a schematic plan view of the main part. Note that FIG. 13(a) is a cross section taken along the line AA of FIG. 13(b), and illustration of the insulating protective film is omitted in FIG. 13(b).

As illustrated, a first insulating protective film 17 is formed on the electro-mechanical conversion element 19 and the first insulating protective film 17 has a contact hole 53 . A fifth electrode 35 and a sixth electrode 36 are formed as lead wires on the first insulating protective film 17, and a second insulating protective film 18 is formed thereon. The first electrode 31, the second electrode 32, and the fifth electrode 35 are electrically connected through the contact hole of the first insulating protective film 17, and the third electrode 33, the fourth electrode 34, and the fifth electrode 35 are electrically connected. 6 and the electrode 36 are electrically connected.

Also, in the present embodiment, the fifth electrode 35 is used as a common electrode and the sixth electrode 36 is used as an individual electrode, but the reverse is also possible. The second insulating protective film 18 protects the common electrode and the individual electrodes, and is partially opened to form an electrode PAD. An individual electrode PAD51 is formed for the individual electrode, and a common electrode PAD52 is formed for the common electrode.

<<Polarization>>
FIG. 14 shows an example of a polarization treatment apparatus. Using such an apparatus, the electro-mechanical conversion element is subjected to polarization treatment. The configuration of the polarization treatment apparatus of this embodiment includes a corona electrode 61 and a grid electrode 62, which are connected to a corona power supply 63 and a grid power supply 64, respectively. The grid electrode 62 is mesh-processed so that when a high voltage is applied to the corona electrode 61, ions, charges, etc. generated by corona discharge efficiently fall onto the sample stage 65 below. By adjusting the voltage applied to the corona electrode 61 and the grid electrode 62 and the distance between the sample and each electrode, it is possible to adjust the strength of the corona discharge.

Moreover, the sample stage 65 on which the sample is set has a temperature control function, so that the polarization process can be performed while applying a temperature of up to about 350.degree. The sample stage 65 is grounded, and polarization processing cannot be performed without the grounding.

Here, the state of polarization processing is determined from the PE hysteresis loop. FIG. 15 shows an example of a PE hysteresis loop. FIG. 15(a) is an example of a PE hysteresis loop before polarization, and FIG. 15(b) is an example of a PE hysteresis loop before polarization.

As shown, the hysteresis loop was measured under an electric field strength of ±150 kV/cm, the initial polarization at 0 kV/cm was Pind, and the polarization at +150 kV/cm was returned to 0 kV/cm. When the polarization at time is Pr, the value of Pr-Pind is defined as the polarizability, and the quality of the polarization state is judged from this polarizability. The polarizability Pr-Pind is preferably 10 μC/cm ² or less, more preferably 5 μC/cm ² or less. Within the above range, it is possible to suppress displacement degradation after continuous driving as a PZT piezoelectric actuator.

FIG. 16 shows a schematic diagram for explaining the polarization treatment. As shown in the figure, when a corona wire 70 is used to cause corona discharge, molecules 71 in the atmosphere are ionized to generate cations 72, which are passed through the PAD portion of the electro-mechanical conversion element (piezoelectric element). The flow of positive ions 72 accumulates electric charge in the electro-mechanical conversion element. An internal potential difference is generated due to a charge difference between the upper electrode and the lower electrode, and polarization processing is performed.

Here, as the charge amount Q required for the polarization process, a charge amount of 1×10 ⁻⁸ C or more is preferably accumulated, and a charge amount of 4×10 ⁻⁸ C or more is more preferably accumulated. Within the above range, the polarization process can be performed satisfactorily, and the deterioration of displacement after continuous driving can be suppressed as a piezoelectric actuator of PZT.

In order to obtain the desired polarizability Pr-Pind, the voltage of the corona electrode 61 and grid electrode 62 shown in FIG. 14, the distance between the sample stage 65 and the corona electrode 61 and grid electrode 62, etc. Adjusting is preferred. In order to obtain the desired polarizability, it is preferable to generate a high electric field with respect to the electro-mechanical conversion film.

<<First insulating protective film>>
As the first insulating protective film 17, it is preferable to select a material that prevents damage to the electro-mechanical conversion element due to the film formation and etching processes and that makes it difficult for moisture in the atmosphere to permeate. preferable. In the case of organic materials, it is necessary to increase the film thickness in order to obtain sufficient protective performance. If the insulating film is made thick, the vibration displacement of the vibration plate is significantly hindered, and thus the ejection performance may be degraded.

As the first insulating protective film 17, it is preferable to use an oxide, nitride, carbide film, or the like in order to obtain a thin film with high protective performance. It is preferable to select a material having high adhesion to the electrode material, the piezoelectric material, and the diaphragm material, which serve as the base of the insulating film.

Moreover, it is preferable to select a film forming method that does not damage the electro-mechanical conversion element. The electro-mechanical conversion element may be damaged in the plasma CVD method in which a reactive gas is turned into plasma and deposited on the substrate, or in the sputtering method in which the plasma is ejected by colliding with the target material to form a film.
Preferable film forming methods include a vapor deposition method and an ALD (Atomic Layer Deposition) method. Among them, the ALD method, which has a wide range of materials to choose from, is preferable.

Preferable materials include oxide films used for ceramic materials such as Al ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , Ta ₂ O ₃ and TiO ₂ . When these materials are used, particularly by using the ALD method, a thin film with a very high film density can be produced and damage during the process can be suppressed.

The film thickness of the first insulating protective film 17 is preferably a thickness sufficient to ensure the protection performance of the electro-mechanical transducer, and should be as thin as possible so as not to hinder the displacement of the diaphragm. preferable. The film thickness of the first insulating protective film 17 is preferably 20 nm to 100 nm. When the thickness is 20 nm or more, the function as a protective layer of the electro-mechanical transducer can be obtained, and deterioration of the performance of the electro-mechanical transducer can be suppressed. When it is 100 nm or less, it is possible to suppress a decrease in the displacement of the vibration plate, thereby suppressing a decrease in ejection efficiency.

Also, the first insulating protective film 17 may have a plurality of layers, for example, two layers. In this case, in order to increase the thickness of the second insulating protective film, the second insulating protective film may be opened in the vicinity of the second electrode 32 so as not to significantly hinder the vibrational displacement of the diaphragm. . At this time, any oxide, nitride, carbide, or composite compound thereof can be used as the second insulating protective film, and SiO ₂ generally used in semiconductor devices is preferably used.

Any method can be used as a method for forming the second insulating protective film. For example, the CVD method, the sputtering method, and the like can be mentioned, and it is preferable to use the CVD method, which is capable of isotropically forming a film, considering the step coverage of the pattern forming portion such as the electrode forming portion.

It is preferable that the film thickness of the insulating protective film of the second layer is such that the voltage applied to the lower electrode and the individual electrode wiring does not cause dielectric breakdown. That is, it is preferable to set the electric field intensity applied to the insulating film within a range that does not cause dielectric breakdown. Furthermore, considering the surface properties and pinholes of the first insulating protective film, the film thickness of the insulating protective film in the case of multiple layers is preferably 200 nm or more, more preferably 500 nm or more.

<<Fifth Electrode, Sixth Electrode>>
Metal electrode materials such as Ag alloy, Cu, Al, Au, Pt and Ir are preferable for the fifth electrode 35 and the sixth electrode 36 .
As a manufacturing method, it is preferable to use a sputtering method, a spin coating method, or the like, and then obtain a desired pattern by photolithoetching or the like.

The film thickness of the fifth electrode 35 and the sixth electrode 36 is preferably 0.1-20 μm, more preferably 0.2-10 μm. When the thickness is 0.1 μm or more, it is possible to prevent the resistance from becoming large and to prevent a sufficient current from flowing through the electrode, thereby preventing the ejection from becoming unstable. When it is 20 μm or less, the process time can be shortened.

In addition, the contact resistance at the contact hole portion (for example, 10 μm×10 μm) of the common electrode and the individual electrode is preferably 10Ω or less for the common electrode and 1Ω or less for the individual electrode, and more preferably 5Ω or less for the common electrode. As an individual electrode, it is 0.5Ω or less.
Within this range, it is possible to supply a sufficient amount of electric current, and to prevent problems that occur when the liquid is ejected.

<<Second insulating protective film>>
The second insulating protective film 18 functions as a passivation layer that protects the individual electrode wiring and the common electrode wiring. In FIG. 13, the individual electrodes and the common electrode are covered except for the individual electrode lead-out portion and the common electrode lead-out portion.
By using the second insulating protective film 18, inexpensive Al or an alloy material containing Al as a main component can be used as the electrode material. As a result, a low-cost and highly reliable inkjet head can be obtained.

Any inorganic material or organic material can be used as the material of the second insulating protective film 18, but a material with low moisture permeability is preferable.
Examples of inorganic materials include oxides, nitrides, and carbides, and examples of organic materials include polyimides, acrylic resins, urethane resins, and the like. In the case of an organic material, it is necessary to form a thick film, so it should be noted that patterning is difficult. Therefore, it is preferable to use an inorganic material capable of exhibiting a wiring protection function in a thin film. In particular, the use of Si ₃ N ₄ on the Al wiring is preferable because it is a proven technology for semiconductor devices.

The film thickness of the second insulating protective film 18 is preferably 200 nm or more, more preferably 500 nm or more. In the case of the above range, a sufficient passivation function can be exhibited, and disconnection due to corrosion of the wiring material and deterioration of the reliability of the inkjet can be prevented.

Moreover, it is preferable that the second insulating protective film 18 has openings on the electro-mechanical conversion element and on the surrounding diaphragm. As a result, it is possible to prevent the displacement of the diaphragm from being hindered, and to further improve the ejection characteristics and reliability.

Further, as shown in FIG. 13, a part of the second insulating protective film 18 is opened to form an individual electrode PAD51 and a common electrode PAD52. A method for forming the opening portion can be appropriately selected. Since the electro-mechanical conversion element is protected by the first insulating protective film 17, a photolithography method or a dry etching method can be used.

Also, the area of the PAD portion is preferably 50×50 μm ² or more, more preferably 100×300 μm ² or more. In this case, the polarization process can be performed satisfactorily, and displacement deterioration after continuous driving can be suppressed.

(liquid ejection unit, device for ejecting liquid)
Next, an example of an apparatus for ejecting liquid according to the present invention will be described with reference to FIGS. 17 and 18. FIG. FIG. 17 is an explanatory plan view of the essential parts of the device, and FIG. 18 is an explanatory side view of the essential parts of the same device.

This apparatus is a serial type apparatus, and a main scanning movement mechanism 493 reciprocates the carriage 403 in the main scanning direction. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, and the like. The guide member 401 is bridged between the left and right side plates 491A and 491B to movably hold the carriage 403 . A main scanning motor 405 reciprocates the carriage 403 in the main scanning direction via a timing belt 408 stretched between a drive pulley 406 and a driven pulley 407 .

The carriage 403 is equipped with a liquid ejection unit 440 in which a liquid ejection head 404 and a head tank 441 according to the present invention are integrated. The liquid ejection head 404 of the liquid ejection unit 440 ejects yellow (Y), cyan (C), magenta (M), and black (K) liquids, for example. Further, the liquid ejection head 404 is mounted with a nozzle row having a plurality of nozzles arranged in a sub-scanning direction perpendicular to the main scanning direction, and the ejection direction facing downward.

The liquid stored in the liquid cartridge 450 is supplied to the head tank 441 by the supply mechanism 494 for supplying the liquid stored outside the liquid ejection head 404 to the liquid ejection head 404 .

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

This device has a transport mechanism 495 for transporting the paper 410 . The transport mechanism 495 includes a transport belt 412 as transport means and a sub-scanning motor 416 for driving the transport belt 412 .

The transport belt 412 attracts the paper 410 and transports it at a position facing the liquid ejection head 404 . The conveying belt 412 is an endless belt and stretched between a conveying roller 413 and a tension roller 414 . Adsorption can be performed by electrostatic adsorption, air suction, or the like.

The conveying belt 412 rotates in the sub-scanning direction when the conveying roller 413 is rotationally driven by the sub-scanning motor 416 via the timing belt 417 and the timing pulley 418 .

Further, on one side of the carriage 403 in the main scanning direction, a maintenance/recovery mechanism 420 for maintaining/recovering the liquid ejection head 404 is arranged on the side of the transport belt 412 .

The maintenance/recovery mechanism 420 includes, for example, a cap member 421 that caps the nozzle surface (surface on which nozzles are formed) of the liquid ejection head 404, a wiper member 422 that wipes the nozzle surface, and the like.

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

In this apparatus configured as described above, the paper 410 is fed onto the conveying belt 412 and attracted thereto, and the conveying belt 412 is rotated to convey the paper 410 in the sub-scanning direction.

Therefore, by driving the liquid ejection head 404 according to the image signal while moving the carriage 403 in the main scanning direction, the liquid is ejected onto the stationary paper 410 to form an image.

As described above, since this apparatus includes the liquid ejection head according to the present invention, it is possible to stably form a high-quality image.

Next, another example of the liquid ejection unit according to the invention will be described with reference to FIG. FIG. 19 is an explanatory plan view of the main part of the same unit.

Among the members constituting the apparatus for ejecting the liquid, the liquid ejection unit includes a housing portion composed of side plates 491A and 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, a liquid It is composed of an ejection head 404 .

A liquid ejection unit can also be constructed in which at least one of the maintenance/restoration mechanism 420 and the supply mechanism 494 is further attached to, for example, the side plate 491B of the liquid ejection unit.

Next, still another example of the liquid ejection unit according to the present invention will be described with reference to FIG. FIG. 20 is an explanatory front view of the same unit.

This liquid ejection unit comprises a liquid ejection head 404 to which a channel component 444 is attached, and a tube 456 connected to the channel component 444 .

Note that the channel component 444 is arranged inside the cover 442 . A head tank 441 can also be included in place of the channel component 444 . A connector 443 for electrical connection with the liquid ejection head 404 is provided above the channel component 444 .

In the present application, a "device that ejects liquid" is a device that includes a liquid ejection head or a liquid ejection unit, drives the liquid ejection head, and ejects liquid. Devices that eject liquid include not only devices that can eject liquid onto an object to which liquid can adhere, but also devices that eject liquid into air or liquid.

The "liquid ejecting device" can include means for feeding, transporting, and ejecting an object to which liquid can adhere, as well as a pre-processing device, a post-processing device, and the like.

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

Further, the "apparatus for ejecting liquid" is not limited to one that visualizes significant images such as characters and figures with the ejected liquid. For example, it includes those that form patterns that have no meaning per se, and those that form three-dimensional images.

The above-mentioned "substance to which a liquid can adhere" means a substance to which a liquid can adhere at least temporarily, such as a substance to which a liquid adheres and adheres, a substance which adheres and permeates, and the like. Specific examples include media such as recording media such as paper, recording paper, recording paper, film, and cloth, electronic components such as electronic substrates and piezoelectric elements, powder layers (powder layers), organ models, and test cells. Yes, and unless otherwise specified, includes anything that has liquid on it.

The materials of the above "things to which liquids can adhere" include paper, threads, fibers, fabrics, leather, metals, plastics, glass, wood, ceramics, building materials such as wallpaper and flooring, textiles for clothing, etc. However, it is sufficient if it can be attached.

The "liquid" also includes inks, treatment liquids, DNA samples, resists, pattern materials, binders, modeling liquids, and solutions and dispersions containing amino acids, proteins, and calcium.

Further, the ``device for ejecting liquid'' includes a device in which a liquid ejection head and an object to which liquid can be adhered move relatively, but is not limited to this. Specific examples include a serial type apparatus in which the liquid ejection head is moved and a line type apparatus in which the liquid ejection head is not moved.

In addition, as a "liquid ejecting device", there are other processing liquid coating devices that eject processing liquid onto the paper in order to apply the processing liquid to the surface of the paper for the purpose of modifying the surface of the paper, raw materials is dispersed in a solution, and sprays a composition liquid through a nozzle to granulate fine particles of the raw material.

A "liquid ejection unit" is a combination of functional parts and mechanisms integrated with a liquid ejection head, and is a collection of parts related to ejection of liquid. For example, the "liquid ejection unit" includes a combination of at least one of a head tank, a carriage, a supply mechanism, a maintenance/recovery mechanism, and a main scanning movement mechanism with a liquid ejection head.

Here, integration means, for example, that the liquid ejection head and functional parts or mechanisms are fixed to each other by fastening, adhesion, or engagement, or that one is held movably with respect to the other. include. Also, the liquid ejection head, the functional parts, and the mechanism may be configured to be detachable from each other.

For example, as a liquid ejection unit, there is a liquid ejection head and a head tank integrated like a liquid ejection unit 440 shown in FIG. Also, there is a type in which a liquid ejection head and a head tank are integrated by being connected to each other by a tube or the like. Here, it is also possible to add a unit including a filter between the head tank and the liquid ejection head of these liquid ejection units.

Further, there is a liquid ejection unit in which a liquid ejection head and a carriage are integrated.

Further, as a liquid ejection unit, there is one in which the liquid ejection head is movably held by a guide member constituting a part of the scanning movement mechanism, and the liquid ejection head and the scanning movement mechanism are integrated. Further, as shown in FIG. 19, there is a liquid ejection unit in which a liquid ejection head, a carriage, and a main scanning movement mechanism are integrated.

There is also a liquid ejection unit in which the liquid ejection head, the carriage, and the maintenance and recovery mechanism are integrated by fixing a cap member, which is a part of the maintenance and recovery mechanism, to a carriage to which the liquid ejection head is attached. .

Further, as a liquid ejection unit, as shown in FIG. 20, there is a liquid ejection head in which a tube is connected to a head tank or a liquid ejection head to which flow path parts are attached, and the liquid ejection head and the supply mechanism are integrated. .

It is assumed that the main scanning movement mechanism also includes a single guide member. Also, the supply mechanism includes a single tube and a single loading unit.

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

Further, the terms used in the present application, such as image formation, recording, printing, printing, printing, modeling, etc., are synonymous.

<One Embodiment of Apparatus for Discharging Liquid>
Next, an example of an apparatus for ejecting liquid equipped with an electro-mechanical transducer according to the present invention will be described with reference to the inkjet recording apparatus shown in FIGS. 21 and 22. FIG. 21 is an explanatory perspective view of the same recording apparatus, and FIG. 22 is an explanatory side view of a mechanical portion of the same recording apparatus.

This ink jet recording apparatus comprises a carriage which can move in the main scanning direction inside a main body 81 of the recording apparatus, a recording head including an ink jet head mounted on the carriage, an ink cartridge which supplies ink to the recording head, and the like. A paper feeding cassette (or a paper feeding tray may be used) 84 capable of stacking a large number of papers 83 from the front side is detachably attached to the lower part of the apparatus body 81 . be able to. In addition, a manual feed tray 85 for manually feeding the paper 83 can be opened. Also, the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and after a desired image is recorded by the printing mechanism unit 82, the paper is discharged to the paper discharge tray 86 mounted on the rear side.

The printing mechanism unit 82 holds a carriage 93 slidably in the main scanning direction by means of a main guide rod 91 and a sub guide rod 92, which are guide members placed horizontally between left and right side plates (not shown). (Y), cyan (C), magenta (M), and black (Bk). They are arranged in an intersecting direction and mounted with the ink droplet ejection direction directed downward. In addition, each ink cartridge 95 for supplying ink of each color to the head 94 is exchangeably mounted on the carriage 93 .

The ink cartridge 95 has an upper atmosphere port communicating with the atmosphere, a lower supply port for supplying ink to the inkjet head, and a porous body filled with ink inside. maintains the ink supplied to the inkjet head at a slight negative pressure. Further, although the heads 94 for each color are used as the recording heads here, one head having nozzles for ejecting ink droplets for each color may be used.

Here, the carriage 93 has its rear side (downstream side in the paper transport direction) slidably fitted on the main guide rod 91 and its front side (upstream side in the paper transport direction) slidably placed on the secondary guide rod 92 . is doing. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is stretched between a driving pulley 98 and a driven pulley 99 which are rotationally driven by a main scanning motor 97 . , and the carriage 93 is reciprocally driven by the forward and reverse rotation of the main scanning motor 97 .

On the other hand, in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the head 94, a paper feed roller 101 and a friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84 and the paper 83 are guided. A guide member 103, 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 leading end that defines the delivery angle of the paper 83 from the transport roller 104. A roller 106 is provided. The conveying roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

A print receiving member 109 serving as a paper guide member is provided below the recording head 94 to guide the paper 83 fed from the conveying roller 104 so as to correspond to the moving range of the carriage 93 in the main scanning direction. A conveying roller 111 and a spur 112 which are rotatably driven to feed the paper 83 in the paper discharge direction are provided downstream of the print receiving member 109 in the paper conveying direction, and a paper discharge tray 86 for sending the paper 83 to the paper discharge tray 86. A roller 113, a spur 114, and guide members 115 and 116 forming a paper ejection path are provided.

During recording, the carriage 93 is moved and the recording head 94 is driven according to image signals to eject ink onto the stationary paper 83 to record one line. Make a record of the line of Upon receiving a recording end signal or a signal indicating that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

In addition, a recovery device 117 for recovering defective ejection of the head 94 is arranged at a position outside the recording area on the right end side in the moving direction of the carriage 93 . The recovery device 117 has cap means, suction means and cleaning means. The carriage 93 is moved to the side of the recovery device 117 while waiting for printing, and the head 94 is capped by the capping means to keep the ejection openings in a wet state, thereby preventing ejection failure due to ink drying. In addition, by ejecting ink that is not related to printing during printing, etc., the ink viscosity of all ejection ports is made constant, and stable ejection performance is maintained.

In the event of an ejection failure, the ejection port (nozzle) of the head 94 is sealed with capping means, and the ink and air bubbles are sucked out from the ejection port through the tube by suction means to remove ink, dust, etc. adhering to the ejection port surface. is removed by the cleaning means to recover the ejection failure. Also, the sucked ink is discharged to a waste ink reservoir provided at the bottom of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.

In the ink jet recording apparatus, since the actuator of the present invention is mounted, the displacement characteristics at the initial stage and over time are good, and the ejection characteristics are good. In addition, there is no ejection failure due to defective driving of the diaphragm, stable ejection characteristics are obtained, and image quality is improved.

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

(Example 1)
SOI wafers shown in Table 1 were used as the substrate and diaphragm. In this embodiment, the silicon layer is p-type Si and B is used as an impurity.
A Ti film (film thickness: about 20 nm) was formed on an SOI wafer at 350° C. by sputtering, and thermally oxidized at 750° C. by RTA (rapid thermal annealing). Subsequently, a Pt film (thickness: about 160 nm) was deposited at about 300° C. by sputtering. A TiO ₂ film obtained by thermally oxidizing the Ti film serves as an adhesion layer between the SiO ₂ film and the Pt film. Thus, a first electrode was formed on the diaphragm.

Next, as a material for a PbTiO ₃ layer (also referred to as a PT layer) that serves as a seed layer for the PZT film, a coating solution (hereinafter referred to as a PT coating solution) prepared at a composition ratio of Pb:Ti=1:1 was prepared.

Also, as materials for the PZT film, three PZT precursor coating liquids prepared at the following composition ratios were prepared.
[1st liquid] Pb:Zr:Ti=115:55:45
[2nd liquid] Pb:Zr:Ti=115:49:51
[3rd solution] Pb:Zr:Ti=115:43:57

A concrete PZT precursor coating liquid was synthesized as follows. First, lead acetate trihydrate, isopropoxide titanium, and isopropoxide zirconium were used as starting materials. Crystal water of lead acetate was dehydrated after dissolving in methoxyethanol. The amount of lead is excessive for the stoichiometric composition. This is to prevent deterioration of crystallinity due to so-called lead removal during heat treatment.
Next, titanium isopropoxide and zirconium isopropoxide are dissolved in methoxyethanol, alcohol exchange reaction and esterification reaction are allowed to proceed, and the PZT precursor coating liquid is obtained by mixing with the methoxyethanol solution in which lead acetate is dissolved. Synthesized. The PZT concentration was 0.5 mol/l. The PT coating liquid is also synthesized in the same manner as the PZT precursor coating liquid.

First, a film was formed on the first electrode by spin coating using a PT coating liquid, and then dried at 120° C. with a hot plate. This formed a seed layer with a thickness of 7 nm.

Next, on the seed layer, a PZT film was formed by spin coating using [1st liquid] with a high Zr ratio, and dried (120° C.) and thermally decomposed (400° C.) with a hot plate. Next, a PZT film was formed by spin coating with the [2nd liquid], dried (120° C.) and thermally decomposed (400° C.) by a hot plate. Furthermore, a PZT film was formed by spin coating using [3rd liquid] with a low Zr ratio, and dried (120° C.) and pyrolyzed (400° C.) on a hot plate to form three layers. Next, after thermal decomposition treatment for the third layer, heat treatment (at a temperature of 730° C.) for crystallization was performed by RTA (rapid heat treatment).

The film thickness of the PZT film was 240 nm when the heat treatment for crystallization was completed. A total of 8 times (24 layers) of the heat treatment steps of coating, drying, thermal decomposition and crystallization of the PZT precursor solution were performed to obtain a PZT film having a thickness of about 2.0 μm.

Next, a third electrode and a fourth electrode are produced. A SrRuO ₃ film (40 nm thick) was formed as an oxide film (third electrode), and a Pt film (125 nm thick) was formed as a metal film (fourth electrode) by sputtering. Thereafter, a photoresist (TSMR8800) manufactured by Tokyo Ohka Co., Ltd. was formed by spin coating, and after forming a resist pattern by normal photolithography, a pattern as shown in FIG. 13 was formed using an ICP etching device (manufactured by Samco). made.

Next, as a first insulating protective film, an Al ₂ O ₃ film was formed to a thickness of 50 nm using the ALD method. At this time, TMA (Sigma-Aldrich Co.) for Al and O ₃ generated by an ozone generator were alternately laminated for O to form a film. After that, as shown in FIG. 13, a contact hole portion was formed by etching.

Next, Al was deposited as a fifth electrode and a sixth electrode by sputtering, and patterned by etching. Then, Si ₃ N ₄ was deposited as a second insulating protective film to a thickness of 500 nm by plasma CVD to fabricate an actuator.

Next, the obtained actuator was subjected to polarization treatment by corona charging treatment. The apparatus shown in FIG. 14 was used for the polarization treatment. A tungsten wire with a diameter of 50 μm is used for the corona charging treatment. The polarization treatment conditions were a treatment temperature of 80° C., a corona voltage of 9 kV, a grid voltage of 2.5 kV, a treatment time of 30 s, a distance between the corona electrode and the grid electrode of 4 mm, and a distance between the grid electrode and the stage of 4 mm.

A common electrode PAD and an individual electrode PAD for connecting to the fifth electrode and the sixth electrode are formed. The distance between the individual electrodes PAD was set to 80 μm.

(Examples 2 to 8, 10)
An actuator was produced in the same manner as in Example 1, except that the SOI wafer used in Example 1 was changed to the SOI wafer shown in Table 1.

(Example 9)
_The SOI wafer used in Example 1 was changed to the SOI wafer shown in Table 1, and as shown in FIG. An actuator was produced in the same manner as in 1.

(Comparative Examples 1 and 2)
The SOI wafer used in Example 1 was changed to the SOI wafer shown in Table 1, and instead of the PT layer, which was the second electrode (seed layer), a TiO ₂ film of 7 nm was formed using a sputtering apparatus. An actuator was produced in the same manner as in Example 1.

(Comparative Examples 3 and 4)
An actuator was produced in the same manner as in Example 1, except that the SOI wafer used in Example 1 was changed to the SOI wafer shown in Table 1.

(evaluation)
The displacement characteristics (piezoelectric constant) and ejection characteristics of the actuator obtained above were evaluated.

<Displacement evaluation>
As for the evaluation of displacement characteristics, as shown in FIG. 6, excavation is performed from the back side of the substrate to form individual liquid chambers, and then vibration evaluation is performed. The amount of deformation (piezoelectric constant d31) due to the application of an electric field (150 kV/cm) was measured with a laser Doppler vibrometer, and calculated from matching by simulation. Table 1 shows the results obtained. Evaluation criteria are as follows. ⊚ and ◯ were regarded as passed.

[Evaluation criteria]
◎: Piezoelectric constant d31 is -140 to -160 pm / V
○: Piezoelectric constant d31 is -160 to -180pm/V (excluding -160pm/V)
△: Piezoelectric constant d31 is -120 to -140pm/V (excluding -140pm/V)
×: Piezoelectric constant d31 other than the above

The examples had characteristics (piezoelectric constant of -140 to -180 pm/V) equivalent to those of general ceramic sintered bodies at the initial stage and with time.
As for the comparative example, the piezoelectric constant is low at least at the initial stage and after aging, and it can be seen that the characteristics are inferior to those of general ceramic sintered bodies.

<Discharge evaluation>
Using the actuator obtained as described above, a liquid ejection head as shown in FIG. 7 was produced, and the liquid ejection characteristics were evaluated. Using an ink having a viscosity adjusted to 5 cp as a liquid, the discharge state was confirmed when an applied voltage of -10 to -30 V was applied with a simple push waveform. Good results are obtained in the order of ⊚, ◯, Δ, and ×.

It was confirmed that all of Examples 1 to 10 could be ejected from any nozzle hole and could be ejected at a high frequency.
On the other hand, in Comparative Example 2, ink could not be ejected, and in Comparative Example 1, ink could not be ejected stably when it was attempted to eject at a high frequency.

<Evaluation of diaphragm stress>
In the example, it was determined that the diaphragm had stress on the compression side based on the measurement result of the amount of warpage when the diaphragm was manufactured. On the other hand, in the comparative example, it was determined that the diaphragm did not have the stress on the compression side, but had the stress on the tension side.

Although the above example shows the results for p-type Si, even if the silicon layer is n-type Si, the same results as for p-type Si can be obtained.

Reference Signs List 11 substrate 12 diaphragm 13 lower electrode 14 electro-mechanical conversion film 15 upper electrode 16 stress control layer 17 first insulating protective film 18 second insulating protective film 19 electro-mechanical conversion element 20 first silicon oxide film 21 silicon Layer 22 Second silicon oxide film 31 First electrode 32 Second electrode 33 Third electrode 34 Fourth electrode 35 Fifth electrode 36 Sixth electrode 40 Nozzle plate 41 Nozzle 42 Individual liquid chamber 43 Partition 51 Individual electrode PAD
52 common electrode PAD
53 contact hole 61 corona electrode 62 grid electrode 63 corona power source 64 grid power source 65 sample stage 401 guide member 403 carriage 404 liquid ejection head 405 main scanning motor 406 drive pulley 407 driven pulley 408 timing belt 410 paper 412 transport belt 413 transport roller 414 tension Roller 416 sub-scanning motor 417 timing belt 418 timing pulley 420 maintenance and recovery mechanism 421 cap member 422 wiper member 440 liquid discharge unit 441 head tank 442 cover 443 connector 444 channel component 450 liquid cartridge 451 cartridge holder 452 liquid feed unit 456 tube 491A, 491B side plate 491C back plate 493 main scanning movement mechanism 494 supply mechanism 495 transport mechanism

Japanese Patent No. 5164244 JP 2017-205955 A

Claims (13)

having a diaphragm, a lower electrode, an electro-mechanical conversion film and an upper electrode,
The diaphragm includes a first silicon oxide film with a thickness of 0.5 μm or more, a silicon layer with a thickness of 3 μm or more on the first silicon oxide film, and a second silicon layer with a thickness of 0.5 μm or more on the silicon layer. having a silicon oxide film,
The actuator, wherein the silicon layer has a volume resistivity of 10 ³ Ω·cm or more and 10 ⁶ Ω·cm or less. The silicon layer is made of p-type silicon with an impurity concentration of 1.3×10 ¹³ atoms/cm ³ or less or n-type silicon with an impurity concentration of 4.3×10 ¹² atoms/cm ³ or less. Item 1. The actuator according to item 1. 3. The actuator according to claim 1, wherein the thickness of said second silicon oxide film is equal to or greater than the thickness of said first silicon oxide film. The electro-mechanical conversion film is made of PZT (lead zirconate titanate),
In the θ-2θ measurement by XRD (X-ray diffraction) measurement of the PZT, the degree of orientation of (100) orientation is 99% or more, and the maximum peak is 2θ at which the peak of the (200) plane or (002) plane is obtained. Any one of claims 1 to 3, wherein the diffraction peak of the (400) plane obtained when the tilt angle (χ) is swung at the position is separated into three peaks having peaks and valleys. Actuator as described. The electro-mechanical conversion film is made of PZT (lead zirconate titanate),
The PZT has a tetragonal a-domain and c-domain,
In the θ-2θ measurement by XRD (X-ray diffraction) measurement of the PZT, when the tilt angle (χ) is swung at the 2θ where the peak of the (200) plane or (002) plane is obtained is the maximum peak position When the diffraction peak of the (400) plane obtained in 1 is separated, the lattice constant is obtained for the peaks corresponding to the a domain and the c domain of the tetragonal crystal, and the maximum lattice constant is determined for a large value, and the maximum lattice constant for a small value is the minimum lattice constant, the ratio of the maximum lattice constant to the minimum lattice constant (maximum lattice constant/minimum lattice constant) is 1.02 or more. The actuator according to any one of claims 1 to 5, wherein the bending rigidity of the diaphragm is 7.0 × 10 ^-10 Nm ² or more. a stress control layer between the diaphragm and the lower electrode ;
7. The actuator according to claim 1 , wherein said stress control layer is made of a material having compressive stress . 8. The actuator according to claim ₇ , wherein said stress control layer consists of ZrO2. a nozzle for ejecting liquid, an individual liquid chamber communicating with the nozzle, and an actuator for generating pressure in the individual liquid chamber,
A liquid ejection head, wherein the actuator is the actuator according to any one of claims 1 to 8. a partition partitioning the individual liquid chamber is formed on the substrate forming the individual liquid chamber;
The diaphragm is provided on the substrate,
10. The liquid ejection head according to claim 9, wherein the partition is made of Si and has a volume resistivity of 10 Ω·cm or less. A liquid ejection unit comprising the liquid ejection head according to claim 9 . a head tank for storing the liquid to be supplied to the liquid ejection head, a carriage for mounting the liquid ejection head, a supply mechanism for supplying the liquid to the liquid ejection head, a maintenance and recovery mechanism for maintaining and recovering the liquid ejection head, and the liquid 12. The liquid ejection unit according to claim 11, wherein at least one of main scanning movement mechanisms for moving the ejection head in the main scanning direction is integrated with the liquid ejection head. 13. A device for ejecting liquid, comprising the liquid ejection head according to claim 9 or 10, or the liquid ejection unit according to claim 11 or 12.

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