JP2010188639A - Piezoelectric element, and liquid ejector using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric element excellent in durability and reliability. <P>SOLUTION: The piezoelectric element 1 is an element which is equipped with a piezoelectric body 30, a lower electrode 20 and an upper electrode 40 which apply an electric field to the piezoelectric body 30. At least part of the portion 30S exposed from the upper electrode 40 of the piezoelectric body 30 is covered with fluent material 50 having hydrophobic and insulation properties. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a piezoelectric element and a liquid ejection apparatus using the same.

  A piezoelectric element including a piezoelectric body that expands and contracts as the electric field application intensity increases and decreases and an electrode that applies an electric field to the piezoelectric body is used as an actuator mounted on a liquid ejection device such as an ink jet recording head. Has been. As a piezoelectric material, a perovskite oxide such as lead zirconate titanate (PZT) is known.

  When a piezoelectric element is used in a high temperature and high humidity environment for a long period of time, the piezoelectric body absorbs moisture, and as a result, micro cracks occur in the piezoelectric body, and characteristics such as electrical resistance or capacitance of the piezoelectric body May change.

  Conventionally, it has been proposed to provide an inorganic moisture barrier film on the surface of a piezoelectric element in order to suppress the penetration of moisture into the piezoelectric body. However, if there is a highly rigid inorganic film on the piezoelectric body, the displacement of the piezoelectric body is constrained and it is difficult to obtain a large displacement.

  In order to solve the above problem, Patent Documents 1 and 2 disclose that a piezoelectric element including a piezoelectric composition pressure-sensitive body including a piezoelectric ceramic powder and a flexible organic polymer has an outer side of the piezoelectric ceramic powder. In addition, a configuration in which a coating layer made of a water-repellent material that suppresses absorption of moisture into the piezoelectric ceramic powder is provided (claims 1 and 2 of patent document 1, claims 1 and 2 of patent document 2). .

  Examples of the water repellent material constituting the coating layer include fatty acids, fatty acid salts, fatty acid amides, fluorine resins, silicon resins, acrylic resins, and silane compounds (Patent Document 1, Paragraph 0072, Patent Document 2). 0071).

Japanese Unexamined Patent Publication No. 2007-17420 JP 2008-192672 A

According to the processes described in Paragraph 0055 of Patent Document 1 and 0053 of Patent Document 2, the coating layer is a solid layer and is more flexible than an inorganic film, but the displacement of the piezoelectric body is still constrained. There is a fear. Moreover, when a microcrack arises in a piezoelectric material, a microcrack will also arise in the coating layer on it, and the moisture barrier function by a coating layer will be lost.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a piezoelectric element excellent in durability and reliability.

The piezoelectric element of the present invention is a piezoelectric element comprising a piezoelectric body, a lower electrode and an upper electrode for applying an electric field to the piezoelectric body,
At least a part of a portion exposed from the upper electrode of the piezoelectric body is covered with a fluid material that is hydrophobic and has an insulating property.

  In the present specification, the “hydrophobic material” is defined by a material having an HLB value (Hydrophile-lipophile balance) of 6.0 or less. The HLB value of the fluid material used in the present invention is preferably 3.0 or less, more preferably 2.0 or less.

  In the piezoelectric element of the present invention, it is preferable that the surface of the upper electrode is coated with the fluid material. In the piezoelectric element of the present invention, it is particularly preferable that the surface and side surfaces of the upper electrode are coated with the fluid material.

In the piezoelectric element of the present invention, it is preferable that the fluid material has an insulating oil as a main component.
In the present specification, the “main component” is defined as a component of 70% by mass or more.
In the piezoelectric element of the present invention, the fluid material may be adsorbed and held by a porous material having flexibility.
In the piezoelectric element of the present invention, it is preferable that a water-absorbing substance is contained in the fluid material.
In the piezoelectric element of the present invention, it is preferable that the piezoelectric body and the upper electrode are sealed with a resin lid.

  A liquid ejection apparatus of the present invention includes the above-described piezoelectric element of the present invention and a liquid ejection member provided adjacent to the piezoelectric element, the liquid ejection member including a liquid storage chamber in which liquid is stored; And a liquid discharge port through which the liquid is discharged from the liquid storage chamber in response to application of the electric field to the piezoelectric body.

According to the present invention, a piezoelectric element excellent in durability and reliability can be provided.
According to the present invention, it is possible to provide a piezoelectric element that is excellent in durability and reliability in a high-temperature and high-humidity environment at 40 ° C. and a relative humidity of 80%.

Sectional drawing which shows the structure of the piezoelectric element and inkjet recording head of 1st Embodiment which concern on this invention Sectional drawing which shows the structure of the piezoelectric element of 2nd Embodiment which concerns on this invention, and an inkjet recording head. Sectional drawing which shows the structure of the piezoelectric element and inkjet recording head of 3rd Embodiment based on this invention. A diagram showing a configuration example of an ink jet recording apparatus Partial top view of the ink jet recording apparatus of FIG.

“First Embodiment of Piezoelectric Element and Inkjet Recording Head”
With reference to FIG. 1, the structure of a piezoelectric element according to a first embodiment of the present invention and an ink jet recording head (liquid ejecting apparatus) including the same will be described. FIG. 1 is a sectional view (a sectional view in the thickness direction of a piezoelectric element) of an ink jet recording head. In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one.

  The piezoelectric element 1 according to this embodiment is an element in which a lower electrode 20, a piezoelectric body 30, and an upper electrode 40 are sequentially stacked on a substrate 10, and the lower electrode 20 and the upper electrode 40 are formed on the piezoelectric body 30. An electric field is applied in the thickness direction.

  The lower electrode 20 and the piezoelectric body 30 are formed on substantially the entire surface of the substrate 10, and the upper electrode 40 is patterned thereon. The piezoelectric body 30 may be patterned. The piezoelectric body 30 is preferably formed by a pattern composed of a plurality of protrusions separated from each other, whereby the expansion and contraction of the individual protrusions occurs smoothly, so that a larger amount of displacement can be obtained.

The substrate 10 is not particularly limited, and examples include silicon, silicon oxide, stainless steel (SUS), yttrium stabilized zirconia (YSZ), alumina, sapphire, SiC, and SrTiO ₃ . As the base material 10, a laminated substrate such as an SOI substrate in which a SiO ₂ film and a Si active layer are sequentially laminated on a silicon substrate may be used.

The composition of the lower electrode 20 is not particularly limited, and examples thereof include metals such as Au, Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ , and SrRuO ₃ , and combinations thereof. The composition of the upper electrode 40 is not particularly limited, and examples thereof include materials exemplified for the lower electrode 20, electrode materials generally used in semiconductor processes such as Al, Ta, Cr, and Cu, and combinations thereof. The thickness of the lower electrode 20 and the upper electrode 40 is not particularly limited and is preferably 50 to 500 nm.

  The form of the piezoelectric body 30 is not particularly limited, and examples thereof include single crystals, bulk ceramics, and films. Considering thinning, downsizing, productivity, and the like of the piezoelectric element 1, the piezoelectric body 30 is preferably a film, more preferably a thin film having a thickness of 10 nm to 100 μm, and particularly preferably a thin film having a thickness of 100 nm to 20 μm.

  The film formation method of the piezoelectric body 30 is not particularly limited, and gas phase methods such as sputtering, plasma CVD, MOCVD, and PLD; liquid phase methods such as sol-gel method and organometallic decomposition method; and aerosol deposition method Etc.

The composition of the piezoelectric body 30 is not particularly limited, and is preferably composed of one or more perovskite oxides (which may contain inevitable impurities) represented by the following general formula (P).
General formula ABO ₃ (P)
(A: Element of A site, including at least one element selected from the group consisting of Pb, Ba, Sr, Bi, Li, Na, Ca, Cd, Mg, K, and lanthanide elements.
B: Element of B site, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Mg, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe, Ni, Hf , And at least one element selected from the group consisting of Al.
O: oxygen.
The molar ratio of the A site element, the B site element, and the oxygen element is 1: 1: 3 as a standard, but these molar ratios may deviate from the reference molar ratio within a range where a perovskite structure can be taken. )

As the perovskite oxide represented by the general formula (P),
Lead titanate, lead zirconate titanate (PZT), lead zirconate, lead lanthanum titanate, lead lanthanum zirconate titanate, lead zirconium niobate titanate titanate, lead zirconium niobate titanate titanate, titanium titanate zinc niobate Lead-containing compounds such as lead acid, and mixed crystal systems thereof;
Examples thereof include lead-free compounds such as barium titanate, barium strontium titanate, bismuth sodium titanate, bismuth potassium titanate, sodium niobate, potassium niobate, lithium niobate, and mixed crystal systems thereof.

  Since the electrical characteristics become better, the perovskite oxide represented by the general formula (P) is composed of Mg, Ca, Sr, Ba, Bi, Nb, Ta, W, and Ln (= lanthanide element (La , Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)).

  In the present embodiment, the surface of the piezoelectric element 1 is covered with a fluid material 50 that is hydrophobic and has an insulating property. Specifically, the portion 30 </ b> S exposed from the upper electrode 40 of the piezoelectric body 30, the surface 40 </ b> S of the upper electrode, and the side surface 40 </ b> E of the upper electrode are covered with the fluid material 50.

The main component of the flowable material 50 is not particularly limited as long as it is a material having hydrophobicity, insulating properties, and fluidity. And various other oils such as synthetic drying oil and synthetic insulating oil (chlorine synthetic oil, fluorine synthetic oil, silicone oil, etc.), insulating gel polymer, insulating gel paste, and grease.
The insulating property of the main component of the fluid material 50 is not particularly limited, and preferably has a volume resistivity of 10 × 10 ¹² Ω / cm or more.

In the present embodiment, since the fluid material 50 is a hydrophobic material, the layer of the fluid material 50 functions as a moisture barrier layer, and the presence of this layer suppresses moisture intrusion into the piezoelectric body 30, and is moisture resistant. Improvement effect is obtained.
The HLB value of the fluid material 50 is 6.0 or less, preferably 3.0 or less, more preferably 2.0 or less.
As the main component of the flowable material 50, a silicone oil having an HLB value of 6.0 or less, preferably 3.0 or less, more preferably 2.0 or less is preferable.

The viscosity of the flowable material 50 is not particularly limited. If the viscosity is too low, the flowable material 50 may be washed away from the surface of the piezoelectric element 1, and is preferably 10 cP or more at room temperature (about 20 to 30 ° C.).
The vapor pressure of the flowable material 50 is not particularly limited. If the vapor pressure is too high, the vapor pressure may volatilize and disappear from the surface of the piezoelectric element 1. preferable.

  The flowable material 50 preferably contains a water-absorbing substance. Examples of the water absorbing material include silica gel and water absorbing polymer particles. In such a configuration, even if moisture enters the flowable material 50, the moisture is captured by the water-absorbing substance, so that a higher moisture resistance improvement effect can be obtained.

  In the piezoelectric actuator 2, a vibration plate 60 that vibrates due to expansion and contraction of the piezoelectric body 30 is attached to the back surface of the substrate 10 of the piezoelectric element 1. The piezoelectric actuator 2 is also provided with control means (not shown) such as a drive circuit for controlling the driving of the piezoelectric element 1.

  The ink jet recording head (liquid ejecting apparatus) 3 is roughly composed of an ink chamber (liquid storing chamber) 71 for storing ink and an ink ejecting port (for ejecting ink from the ink chamber 71 to the outside) on the back surface of the piezoelectric actuator 2. An ink nozzle (liquid storage and discharge member) 70 having a liquid discharge port 72 is attached. In the ink jet recording head 3, the electric field strength applied to the piezoelectric element 1 is increased or decreased to expand and contract the piezoelectric element 1, thereby controlling the ejection of ink from the ink chamber 71 and the ejection amount.

  Instead of attaching the diaphragm 60 and the ink nozzle 70 which are members independent of the substrate 10, a part of the substrate 10 may be processed into the diaphragm 60 and the ink nozzle 70. For example, when the substrate 10 is made of a laminated substrate such as an SOI substrate, the substrate 10 is etched from the back side to form the ink chamber 71, and the vibration plate 60 and the ink nozzle 70 are formed by processing the substrate itself. Can do.

  The piezoelectric element 1 and the ink jet recording head 3 of the present embodiment are configured as described above. In the present embodiment, since the surface of the piezoelectric element 1 is covered with a hydrophobic and insulating fluid material 50, the fluid material 50 can be used even when the piezoelectric element 1 is used for a long time in a high humidity environment. As a result, the intrusion of moisture into the piezoelectric body 30 is suppressed. Therefore, problems such as micro cracks occurring in the piezoelectric body 30 due to moisture absorption of the piezoelectric body 30 and changes in characteristics such as electrical resistance or capacitance of the piezoelectric body 30 are suppressed.

  Further, even if a microcrack occurs in the piezoelectric body 30, the fluid material 50 can penetrate into the microcrack and repair it. In the present embodiment, since the surface of the piezoelectric element 1 is covered with the fluid material 50, heat is easily radiated from the element surface, and an effect of suppressing the deterioration of the element 1 is also obtained. Such an effect cannot be obtained with the solid coating layer described in Patent Documents 1 and 2 listed in the section “Background Art”.

  Patent Document 3 below describes that in an organic EL element, the sealing space is filled with silicone oil to suppress the ingress of moisture (paragraph 0025 and the like). However, no such technology has been reported in the past for piezoelectric elements. Further, this document does not describe the repair effect by the fluid material and the heat dissipation effect by the fluid material when microcracks occur.

Patent Document 3: Japanese Patent Laid-Open No. 2003-173868

  As described above, according to this embodiment, it is possible to provide the piezoelectric element 1 having excellent durability and reliability. According to this embodiment, the piezoelectric element 1 excellent in durability and reliability in a high-temperature and high-humidity environment at 40 ° C. and a relative humidity of 80% can be provided.

  The fine electrical wiring of the ink jet recording head 3 may be covered with the fluid material 50. In this case, leakage of the electric wiring due to the influence of moisture can be suppressed, which is preferable.

  In this embodiment, the case where the entire surface of the piezoelectric element 1, that is, the portion 30S exposed from the upper electrode 40 of the piezoelectric body 30, the surface 40S of the upper electrode, and the side surface 40E of the upper electrode is covered with the fluid material 50 will be described. However, if at least a part of the portion 30S exposed from the upper electrode 40 of the piezoelectric body 30 is covered with the fluid material 50, the effect of improving the durability can be obtained.

  However, the entire portion 30 </ b> S exposed from the upper electrode 40 of the piezoelectric body 30 is preferably covered with the fluid material 50. Furthermore, it is more preferable that the surface 40 </ b> S of the upper electrode 40 is covered with the fluid material 50. Furthermore, it is particularly preferable that the surface 40S and the side surface 40E of the upper electrode 40 are covered with the fluid material 50.

“Second Embodiment of Piezoelectric Element and Inkjet Recording Head”
With reference to FIG. 2, the structure of a piezoelectric element according to a second embodiment of the present invention and an ink jet recording head (liquid ejecting apparatus) including the same will be described. FIG. 2 is a sectional view (a sectional view in the thickness direction of the piezoelectric element) of the ink jet recording head. In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The piezoelectric element 4 of the present embodiment is an element in which the lower electrode 20, the piezoelectric body 30, and the upper electrode 40 are sequentially stacked on the substrate 10, as in the first embodiment. 20 and the upper electrode 40 apply an electric field in the thickness direction. As in the first embodiment, the lower electrode 20 and the piezoelectric body 30 are formed on substantially the entire surface of the substrate 10, and the upper electrode 40 is patterned on the upper electrode 40.

  In the present embodiment, a flexible porous material 80 is placed on the surface of the piezoelectric element 4, and the hydrophobic and insulating fluid material 50 (not shown) of the first embodiment. Is adsorbed and retained. Examples of the porous material 80 include porous resins and sponges. Furthermore, any fibrous material may be used as long as it retains the fluid material.

  In the present embodiment, since the fluid material 50 is adsorbed and held by the porous material 80, the fluid material 50 is prevented from flowing out. Therefore, there is no restriction on the viscosity of the flowable material 50.

  The piezoelectric actuator 5 has a diaphragm 60 attached to the back surface of the substrate 10 of the piezoelectric element 4. The ink jet recording head (liquid ejecting apparatus) 6 has an ink nozzle (liquid storing and ejecting member) 70 attached to the back surface of the piezoelectric actuator 5.

  The piezoelectric element 4 and the ink jet recording head 6 of the present embodiment are configured as described above. Also in the present embodiment, as in the first embodiment, the improvement effect of moisture resistance by the fluid material 50, the effect of repairing microcracks, and the like can be obtained. Therefore, according to this embodiment, the piezoelectric element 4 excellent in durability and reliability can be provided. According to this embodiment, the piezoelectric element 4 excellent in durability and reliability in a high-temperature and high-humidity environment at 40 ° C. and a relative humidity of 80% can be provided.

“Third Embodiment of Piezoelectric Element and Inkjet Recording Head”
With reference to FIG. 3, the structure of a piezoelectric element according to a third embodiment of the present invention and an ink jet recording head (liquid ejecting apparatus) including the same will be described. FIG. 3 is a sectional view (a sectional view in the thickness direction of the piezoelectric element) of the ink jet recording head. In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The piezoelectric element 7 of this embodiment is an element in which a lower electrode 20, a piezoelectric body 30, and an upper electrode 40 are sequentially stacked on a substrate 10, as in the first embodiment. 20 and the upper electrode 40 apply an electric field in the thickness direction. As in the first embodiment, the lower electrode 20 and the piezoelectric body 30 are formed on substantially the entire surface of the substrate 10, and the upper electrode 40 is patterned on the upper electrode 40.

  In the present embodiment, the piezoelectric body 30 and the upper electrode 40 are sealed with a resin lid member 90, and the fluid material 50 of the first embodiment is filled in the inner space of the lid member 90.

  The piezoelectric actuator 8 has a diaphragm 60 attached to the back surface of the substrate 10 of the piezoelectric element 7. The ink jet recording head (liquid ejection device) 9 is one in which an ink nozzle (liquid storage and ejection member) 70 is attached to the back surface of the piezoelectric actuator 2.

The piezoelectric element 7 and the ink jet recording head 9 of the present embodiment are configured as described above. Also in the present embodiment, as in the first embodiment, the improvement effect of moisture resistance by the fluid material 50, the effect of repairing microcracks, and the like can be obtained. Furthermore, in this embodiment, since the piezoelectric body 30 and the upper electrode 40 are sealed with the lid member 90, a higher effect of improving moisture resistance can be obtained.
As described above, according to this embodiment, it is possible to provide the piezoelectric element 7 having excellent durability and reliability. According to this embodiment, the piezoelectric element 7 excellent in durability and reliability in a high-temperature and high-humidity environment at 40 ° C. and a relative humidity of 80% can be provided.

  In the present embodiment, the case where the entire inner space of the lid member 90 is filled with the fluid material 50 has been described, but the coverage of the piezoelectric body 30 and the upper electrode 40 with the fluid material 50 is the same as in the first embodiment. Similarly, it can be appropriately changed.

"Inkjet recording device"
With reference to FIG. 4 and FIG. 5, a configuration example of an ink jet recording apparatus including any one of the ink jet recording heads 3, 6, and 9 of the above embodiment will be described. 4 is an overall view of the apparatus, and FIG. 5 is a partial top view.

The illustrated ink jet recording apparatus 100 includes a printing unit 102 having a plurality of ink jet recording heads (hereinafter simply referred to as “heads”) 102K, 102C, 102M, and 102Y provided for each ink color, and each head 102K, An ink storage / loading unit 114 that stores ink to be supplied to 102C, 102M, and 102Y, a paper feeding unit 118 that supplies recording paper 116, a decurling unit 120 that removes curling of the recording paper 116, and a printing unit An adsorption belt conveyance unit 122 that conveys the recording paper 116 while maintaining the flatness of the recording paper 116, and a print detection unit that reads a printing result by the printing unit 102. 124 and a paper discharge unit 126 that discharges printed recording paper (printed matter) to the outside.
The heads 102K, 102C, 102M, and 102Y that form the printing unit 102 are each one of the ink jet recording heads 3, 6, and 9 of the above-described embodiment.

In the decurling unit 120, heat is applied to the recording paper 116 by the heating drum 130 in the direction opposite to the curl direction, and the decurling process is performed.
In the apparatus using roll paper, as shown in FIG. 4, a cutter 128 is provided at the subsequent stage of the decurling unit 120, and the roll paper is cut into a desired size by this cutter. The cutter 128 includes a fixed blade 128A having a length equal to or larger than the conveyance path width of the recording paper 116, and a round blade 128B that moves along the fixed blade 128A. The fixed blade 128A is provided on the back side of the print. The round blade 128B is arranged on the print surface side with the conveyance path interposed therebetween. In an apparatus using cut paper, the cutter 128 is unnecessary.

  The decurled and cut recording paper 116 is sent to the suction belt conveyance unit 122. The suction belt conveyance unit 122 has a structure in which an endless belt 133 is wound between rollers 131 and 132, and at least portions facing the nozzle surface of the printing unit 102 and the sensor surface of the printing detection unit 124 are horizontal ( Flat surface).

  The belt 133 has a width that is wider than the width of the recording paper 116, and a plurality of suction holes (not shown) are formed on the belt surface. An adsorption chamber 134 is provided at a position facing the nozzle surface of the printing unit 102 and the sensor surface of the print detection unit 124 inside the belt 133 that is stretched between the rollers 131 and 132. The recording paper 116 on the belt 133 is sucked and held by suctioning at 135 to make a negative pressure.

  When the power of a motor (not shown) is transmitted to at least one of the rollers 131 and 132 around which the belt 133 is wound, the belt 133 is driven in the clockwise direction in FIG. 4 and is held on the belt 133. The recording paper 116 is conveyed from left to right in FIG.

Since ink adheres to the belt 133 when a borderless print or the like is printed, the belt cleaning unit 136 is provided at a predetermined position outside the belt 133 (an appropriate position other than the print region).
A heating fan 140 is provided on the upstream side of the printing unit 102 on the paper conveyance path formed by the suction belt conveyance unit 122. The heating fan 140 heats the recording paper 116 by blowing heated air onto the recording paper 116 before printing. Heating the recording paper 116 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 102 is a so-called full line type head in which line type heads having a length corresponding to the maximum paper width are arranged in a direction (main scanning direction) perpendicular to the paper feed direction (see FIG. 5). Each of the print heads 102K, 102C, 102M, and 102Y is a line-type head in which a plurality of ink discharge ports (nozzles) are arranged over a length that exceeds at least one side of the maximum size recording paper 116 targeted by the ink jet recording apparatus 100. It is configured.

Heads 102K, 102C, 102M, and 102Y corresponding to the respective color inks are arranged in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 116. ing. A color image is recorded on the recording paper 116 by ejecting the color ink from each of the heads 102K, 102C, 102M, and 102Y while conveying the recording paper 116.
The print detection unit 124 includes a line sensor that images the droplet ejection result of the print unit 102 and detects ejection defects such as nozzle clogging from the droplet ejection image read by the line sensor.

A post-drying unit 142 including a heating fan or the like for drying the printed image surface is provided at the subsequent stage of the print detection unit 124. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.
A heating / pressurizing unit 144 is provided downstream of the post-drying unit 142 in order to control the glossiness of the image surface. The heating / pressurizing unit 144 presses the image surface with a pressure roller 145 having a predetermined surface irregularity shape while heating the image surface, and transfers the irregular shape to the image surface.

The printed matter obtained in this manner is outputted from the paper output unit 126. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. In the ink jet recording apparatus 100, there is provided sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 126A and 126B. It has been.
When the main image and the test print are simultaneously printed on a large sheet of paper, the cutter 148 may be provided to separate the test print portion.
The ink jet recording apparatus 100 is configured as described above.

(Design changes)
The present invention is not limited to the above-described embodiment, and the design can be changed as appropriate without departing from the spirit of the present invention.

Example 1
Examples and comparative examples according to the present invention will be described.

(Comparative Example 1)
An Ir lower electrode having a thickness of 150 nm was formed on a silicon wafer by sputtering, and a PZT piezoelectric film having a thickness of 4 μm was formed thereon by RF sputtering. The deposition conditions for the PZT film were as follows.
Target: Pb _1.3 (Zr _0.46 Ti _0.42 Nb _0.12 ) O ₃ sintered body,
Substrate temperature: 500 ° C
Deposition gas: Ar / O ₂ = 97.5 / 2.5 (flow rate ratio)
Deposition pressure: 0.5 Pa
Target-substrate distance: 60 mm,
RF power: 200W.
Thereafter, the upper electrode was patterned by a normal photolithography method to obtain a piezoelectric element. The upper electrode has a stacked structure of a 50 nm thick Ti layer and a 200 nm thick Pt layer.

  The obtained piezoelectric element was subjected to a driving test under the conditions of an electric field strength of 60 kV / cm and a 100 kHz rectangular wave in an environment of 40 ° C. and a relative humidity of 80%. Changes such as a decrease in electrical resistance, a decrease in capacitance, and an increase in Tan δ (Tan δ is a parameter serving as an index of dielectric loss) were observed at driving of 1 billion dots or less. It seems that the piezoelectric film was deteriorated by moisture.

Example 1
A portion exposed from the upper electrode of the piezoelectric film by dripping mineral oil having an HLB of 1 or less and a viscosity of 40 cp as a fluid material onto the entire surface of the piezoelectric element obtained in Comparative Example 1 by the dispensing method, upper electrode The surface of the upper electrode and the side surface of the upper electrode were covered with silicone oil.
When the obtained piezoelectric element was subjected to a driving test similar to that of Comparative Example 1, even when driving of 10 billion dots was performed, there was no change in any of electrical resistance, capacitance, and Tanδ.

(Example 2)
A piezoelectric element was obtained in the same manner as in Example 1 except that the flowable material for coating the piezoelectric element was obtained by mixing the silicone oil used in Example 1 with commercially available silica gel (particle size: 5 μm). The amount of silica gel added to the silicone oil was 5% by mass.
When the obtained piezoelectric element was subjected to a driving test similar to that of Comparative Example 1, even when driving of 10 billion dots was performed, there was no change in any of electrical resistance, capacitance, and Tanδ.

(Example 3)
A piezoelectric element was obtained in the same manner as in Example 1, except that the silicone oil used in Example 1 was impregnated into a sponge and placed on the piezoelectric element.
When the obtained piezoelectric element was subjected to a driving test similar to that of Comparative Example 1, even when driving of 10 billion dots was performed, there was no change in any of electrical resistance, capacitance, and Tanδ.

  The piezoelectric element of the present invention includes a piezoelectric actuator mounted on an ink jet recording head, a magnetic recording / reproducing head, a MEMS (Micro Electro-Mechanical Systems) device, a micro pump, an ultrasonic probe, an ultrasonic motor, and the like. It can be preferably applied to a ferroelectric element such as a dielectric memory.

1, 4, 7 Piezoelectric element 3, 6, 9 Inkjet recording head (liquid ejection device)
DESCRIPTION OF SYMBOLS 10 Substrate 20 Lower electrode 30 Piezoelectric 30S Part exposed from upper electrode 40 Upper electrode 40S Upper electrode surface 40E Side surface of upper electrode 50 Fluidity material 80 Porous material 90 Lid material 70 Ink nozzle (liquid storage and discharge member)
71 Ink chamber (liquid storage chamber)
72 Ink ejection port (liquid ejection port)
100 Inkjet recording apparatus 102K, 102C, 102M, 102Y Inkjet recording head (liquid ejection apparatus)

Claims (11)

In a piezoelectric element comprising a piezoelectric body, and a lower electrode and an upper electrode that apply an electric field to the piezoelectric body,
A piezoelectric element, wherein at least a part of a portion exposed from the upper electrode of the piezoelectric body is coated with a fluid material that is hydrophobic and has an insulating property.   Furthermore, the surface of the said upper electrode is coat | covered with the said fluid material, The piezoelectric element of Claim 1 characterized by the above-mentioned.   2. The piezoelectric element according to claim 1, wherein a surface and a side surface of the upper electrode are covered with the fluid material.   The piezoelectric element according to claim 1, wherein the fluid material is mainly composed of insulating oil.   The piezoelectric element according to claim 4, wherein the insulating oil is silicone oil.   The piezoelectric element according to claim 1, wherein the fluid material is adsorbed and held by a porous material having flexibility.   The piezoelectric element according to claim 1, wherein the fluid material contains a water-absorbing substance.   The piezoelectric element according to claim 7, wherein the water-absorbing substance is a water-absorbing polymer particle.   The piezoelectric element according to claim 8, wherein the water-absorbing polymer particles are silica gel.   The piezoelectric element according to claim 1, wherein the piezoelectric body and the upper electrode are sealed with a resin lid.   A piezoelectric element according to any one of claims 1 to 10, and a liquid discharge member provided adjacent to the piezoelectric element, wherein the liquid discharge member includes a liquid storage chamber in which a liquid is stored, and the piezoelectric element A liquid ejection apparatus, comprising: a liquid ejection port through which the liquid is ejected from the liquid storage chamber in response to application of the electric field to the body.

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