JP2011016319A - Piezoelectric device, driving method of piezoelectric element, and liquid ejector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric device having superior durability.SOLUTION: The piezoelectric device 2 includes a piezoelectric element 1 having a piezoelectric body 13 and electrodes 12, 14 applying voltage to the piezoelectric body 13; a drive control means 20 controlling the applied voltage and the applied frequency of the piezoelectric element 1; an outer temperature measuring device 30 measuring the outer temperature of the piezoelectric device 2; an outer humidity measuring device 30 measuring the outer humidity of the piezoelectric device 2; a dew point measuring means 30 finding the dew point of forming dew on the piezoelectric body 13 in a use state of the piezoelectric device 2, based on the measuring results of the outer temperature measuring device 30 and outer humidity measuring device 30, and the relation between the outer temperature and outer humidity acquired in advance, and the dew point forming dew on the piezoelectric body 13; and a piezoelectric body temperature control means 40 controlling the temperature of the piezoelectric body 13 within a controlled temperature range higher than the dew point measured by the dew point measuring means 30 and lower than 80°C.

Description

  The present invention relates to a piezoelectric device, a piezoelectric element driving method, and a liquid ejection device.

  Piezoelectric elements that include a piezoelectric body that expands and contracts as the electric field application intensity increases and decreases and an electrode that applies a voltage to the piezoelectric body are used for applications such as piezoelectric actuators mounted on ink jet recording heads. . As a piezoelectric material, PZT (lead zirconate titanate) and a PZT substitution system in which part of the A site and / or B site of PZT is substituted with another element are known. In this specification, PZT and its substitution system are collectively referred to as “PZT system”.

  In Patent Documents 1 and 2, etc., due to heat generation of the piezoelectric body, the ink temperature rises, the volume of the ink flow path is not stable, ejection becomes unstable, or the piezoelectric body itself depolarizes, etc. It is pointed out that this problem occurs, and it is described that the heat radiation of the piezoelectric body is effective.

  On the other hand, it is known that the piezoelectric body deteriorates due to moisture mixing. Patent Document 3 proposes using dry air to keep the dew point of the piezoelectric element and its surrounding atmosphere at a value lower than the dew point of the external environment (claim 1, paragraph 0037). However, the structure described in Patent Document 3 is complicated. In paragraph 0037 of Patent Document 3, it is described that a cylinder of dry air is used. However, it is unrealistic to be mounted on a small ink jet printer or the like. Patent Document 4 proposes that a piezoelectric material is heated using a heat generating film to remove moisture (claims 1 and 2).

  As described above, in the past, while there was an idea that the heat dissipation of the piezoelectric body was good, there was a contradictory idea that the heating of the piezoelectric body was good, and it was not clear which was effective.

Japanese Unexamined Patent Publication No. 2000-135788 JP 2005-027402 JP 2004-322605 A JP 2000-43259 A

The inventor has found a suitable driving condition of the piezoelectric body by focusing on the relationship between the temperature and humidity of the external environment of the piezoelectric element, the temperature of the piezoelectric body itself, and the durability of the piezoelectric body, and has excellent durability. Invented a piezoelectric device and a driving method of the piezoelectric element.
That is, an object of the present invention is to provide a piezoelectric device excellent in durability and a driving method of a piezoelectric element excellent in durability.

The piezoelectric device of the present invention is
A piezoelectric element including a piezoelectric body and an electrode for applying a voltage to the piezoelectric body;
In a piezoelectric device comprising drive control means for controlling the applied voltage and applied frequency of the piezoelectric element,
An external temperature measuring means for measuring an external temperature of the piezoelectric device;
External humidity measuring means for measuring the external humidity of the piezoelectric device;
Based on the measurement results by the external temperature measurement means and the external humidity measurement means, and the relationship between the external temperature and external humidity acquired in advance and the dew point at which dew condensation occurs on the piezoelectric body, under the usage environment of the piezoelectric device. Dew point measuring means for obtaining a dew point at which dew condensation occurs on the piezoelectric body;
Piezoelectric temperature control means for controlling the temperature of the piezoelectric body within a control temperature range higher than the dew point measured by the dew point measuring means and not higher than 80 ° C. is provided.

The piezoelectric body temperature control means includes
Piezoelectric body temperature measuring means for measuring the temperature of the piezoelectric body;
It is preferable that a piezoelectric body temperature adjusting unit that adjusts the temperature of the piezoelectric body based on a measurement result by the piezoelectric body temperature measuring unit and the control temperature range is provided.

The piezoelectric body temperature adjusting means includes:
Heating means for heating the piezoelectric body;
Cooling means for cooling the piezoelectric body;
It is preferable to include a heating / cooling control means for controlling the heating means and the cooling means.

The piezoelectric body temperature control means includes
It is preferable that the temperature of the piezoelectric body is controlled within a control temperature range of the dew point + 2 ° C. to 40 ° C. measured by the dew point measuring means.

The present invention is effective when the piezoelectric body is a piezoelectric film, and is particularly effective when the piezoelectric body is a piezoelectric film having a thickness of 10 μm or less.
The present invention is effective when the drive frequency of the piezoelectric body by the drive control means is 30 kHz or more.
The present invention is effective when the difference (Vpp) between the minimum voltage and the maximum voltage of the drive waveform voltage of the piezoelectric body by the drive control means is 20V or more.

Examples of the piezoelectric body include those containing a perovskite oxide represented by the following general formula (P).
A _a (Zr _x , Ti _y , M _b-xy ) _b O _c (P)
(In the formula, A: an element of A site, and at least one element including Pb.
M represents one or more metal elements.
0 <x <b, 0 <y <b, 0 ≦ b−xy.
Although a: b: c = 1: 1: 3 is a standard, these molar ratios may deviate from the reference molar ratio within a range where a perovskite structure can be taken. )

The piezoelectric element driving method of the present invention is a piezoelectric element driving method comprising a piezoelectric body and an electrode for applying a voltage to the piezoelectric body.
Driving is performed by controlling the temperature of the piezoelectric body within a control temperature range of 80 ° C. or higher higher than a dew point at which dew condensation occurs on the piezoelectric body under the usage environment of the piezoelectric device. is there.

  The liquid ejection device of the present invention includes the piezoelectric device of the present invention and a liquid ejection member provided adjacent to the piezoelectric device, and the liquid ejection member includes a liquid storage chamber in which liquid is stored and the piezoelectric device. And a liquid discharge port through which the liquid is discharged from the liquid storage chamber in response to application of the voltage to the body.

The inventor has found a suitable driving condition of the piezoelectric body by focusing on the relationship between the temperature and humidity of the external environment of the piezoelectric element, the temperature of the piezoelectric body itself, and the durability of the piezoelectric body, and has excellent durability. Invented a piezoelectric device and a driving method of the piezoelectric element.
ADVANTAGE OF THE INVENTION According to this invention, the piezoelectric device excellent in durability and the drive method of the piezoelectric element excellent in durability can be provided.

1 is a perspective view showing the structure of an ink jet recording head (liquid ejecting apparatus) according to a first embodiment of the invention. The perspective view which shows the structure of the inkjet recording head (liquid discharge apparatus) of 2nd Embodiment which concerns 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.

  The inventor has found that when the temperature of the piezoelectric body becomes lower than the dew point, condensation occurs on the piezoelectric body and the piezoelectric body rapidly deteriorates. On the other hand, the higher the temperature of the piezoelectric body, the higher Cp · tan δ (where Cp is the capacitance and tan δ is the dielectric loss), and the amount of heat generated from the piezoelectric body increases. It was found that deterioration accelerates. The present inventor has found that the piezoelectric element can be driven with high durability by controlling the temperature of the piezoelectric body within a temperature range of 80 ° C. or higher higher than the dew point, and has completed the present invention.

That is, the piezoelectric device of the present invention is
A piezoelectric element including a piezoelectric body and an electrode for applying a voltage to the piezoelectric body;
In a piezoelectric device comprising drive control means for controlling the applied voltage and applied frequency of the piezoelectric element,
An external temperature measuring means for measuring an external temperature of the piezoelectric device;
External humidity measuring means for measuring the external humidity of the piezoelectric device;
Based on the measurement results by the external temperature measurement means and the external humidity measurement means, and the relationship between the external temperature and external humidity acquired in advance and the dew point at which dew condensation occurs on the piezoelectric body, under the usage environment of the piezoelectric device. Dew point measuring means for obtaining a dew point at which dew condensation occurs on the piezoelectric body;
Piezoelectric temperature control means for controlling the temperature of the piezoelectric body within a control temperature range higher than the dew point measured by the dew point measuring means and not higher than 80 ° C. is provided.

The piezoelectric element driving method of the present invention is a piezoelectric element driving method comprising a piezoelectric body and an electrode for applying a voltage to the piezoelectric body.
Driving is performed by controlling the temperature of the piezoelectric body within a control temperature range of 80 ° C. or higher higher than a dew point at which dew condensation occurs on the piezoelectric body under the usage environment of the piezoelectric device. is there.

“Inkjet recording head of the first embodiment”
With reference to FIG. 1, the structure of a piezoelectric actuator (piezoelectric device) according to a first embodiment of the present invention and an ink jet recording head (liquid ejection device) including the same will be described. In order to facilitate visual recognition, the scales and positional relationships of the components are appropriately changed from the actual ones.

  A piezoelectric actuator (piezoelectric device) 2 according to this embodiment includes a piezoelectric element 1 and various drive control mechanisms. The piezoelectric actuator 2 of the present embodiment can control the temperature of the piezoelectric body 13 within a control temperature range higher than the dew point and not higher than 80 ° C.

  The piezoelectric element 1 is an element in which a lower electrode 12, a piezoelectric body 13, and an upper electrode 14 are sequentially laminated on a substrate 11 that also serves as a vibration plate. Thus, a voltage is applied in the thickness direction. The patterns of the lower electrode 12, the piezoelectric body 13, and the upper electrode 14 are not limited to those shown in the drawings, and are appropriately designed. The diaphragm may be constituted by a member independent of the substrate 11.

The substrate 11 is not particularly limited, and examples thereof include silicon, silicon oxide, stainless steel (SUS), yttrium-stabilized zirconia (YSZ), alumina, sapphire, SiC, and SrTiO ₃ . As the substrate 11, 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 12 is not particularly limited, and examples thereof include metals or metal oxides such as Au, Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ , and SrRuO ₃ , and combinations thereof. The composition of the upper electrode 14 is not particularly limited, and examples thereof include materials exemplified for the lower electrode 12, electrode materials generally used in semiconductor processes such as Al, Ta, Cr, and Cu, and combinations thereof. The thicknesses of the lower electrode 12 and the upper electrode 14 are not particularly limited and are preferably 50 to 500 nm.

  The piezoelectric actuator 2 is provided with drive control means 20 including a drive circuit for controlling the applied voltage and applied frequency of the piezoelectric element 1.

The piezoelectric actuator 2 further includes
An external temperature measuring means for measuring the external temperature;
An external humidity measuring means for measuring external humidity;
Based on the measurement results obtained by the external temperature measuring means and the external humidity measuring means, and the relationship between the external temperature and external humidity acquired in advance and the dew point at which dew condensation occurs on the piezoelectric body 13, the piezoelectric actuator 2 is used in the usage environment. Dew point measuring means for obtaining a dew point at which condensation occurs on the body 13 is provided.

  In the present embodiment, as the external temperature measuring means, the external humidity measuring means, and the dew point measuring means, the temperature and humidity of the external environment are measured, and the dew point at which dew condensation occurs on the piezoelectric body 13 in the usage environment of the piezoelectric actuator 2 is determined. A temperature / humidity sensor 30 is provided to display the temperature and humidity of the external environment to be obtained and the obtained dew point.

  The piezoelectric actuator 2 further includes piezoelectric body temperature control means 40 for controlling the temperature of the piezoelectric body 13 within a control temperature range of 80 ° C. or higher higher than the dew point measured by the dew point measuring means.

  In order to stably suppress the temperature of the piezoelectric body 13 from becoming the dew point or lower, the piezoelectric body temperature control means 40 sets the temperature of the piezoelectric body 13 to a dew point of + 2 ° C. or higher and 80 ° C. or lower measured by the dew point measuring means. It is preferable to control the temperature within the control temperature range.

  The piezoelectric body temperature control means 40 is more preferably one that controls the temperature as low as possible within the control temperature range. Specifically, it is more preferable that the piezoelectric body temperature control unit 40 controls the temperature of the piezoelectric body 13 within a control temperature range of dew point + 2 ° C. to 60 ° C. measured by the dew point measurement unit. It is particularly preferable to control the temperature of the piezoelectric body 13 within a control temperature range of dew point + 2 ° C. to 40 ° C. measured by the dew point measuring means.

  In the present embodiment, as the piezoelectric body temperature control means 40, the piezoelectric body temperature measurement means 41 that measures the temperature of the piezoelectric body 13, the measurement result by the piezoelectric body temperature measurement means 41, and the control temperature range are used. And a piezoelectric material temperature adjusting means 42 for adjusting the temperature of the piezoelectric material.

  In this embodiment, a thermocouple for measuring the temperature of the piezoelectric body 13 is provided as the piezoelectric body temperature measuring means 41. In this embodiment, the thermocouple is provided so as to contact the lower electrode 12, but the position is not particularly limited as long as the temperature of the piezoelectric body 13 can be measured. As the piezoelectric body temperature measuring means 41, thermography, an infrared microscope, or the like can be used in addition to the thermocouple.

  In this embodiment, as the piezoelectric body temperature adjusting means 42, a heating means 43 for heating the piezoelectric body 13, a cooling means 44 for cooling the piezoelectric body 13, and a heating / cooling control means 45 for controlling the heating means 43 and the cooling means 44. And are provided.

  Examples of the heating means 43 include various heaters such as a silicon rubber heater. Examples of the cooling means 44 include a Peltier element and a blower fan, and a Peltier element is preferable. The installation location of the heating means 43 and the cooling means 44 is not particularly limited as long as the temperature of the piezoelectric body 13 can be changed.

  In the present embodiment, the heating / cooling control means 45 determines the set temperature of the piezoelectric body 13 based on the measurement result by the piezoelectric body temperature measuring means 41 and the control temperature range, so that the piezoelectric body 13 becomes this set temperature. A control device comprising a control circuit 46 for controlling the heating means 43 and the cooling means 44, a display unit 47 for displaying the measurement result by the piezoelectric body temperature measuring unit 41, a display unit 48 for displaying the set temperature of the piezoelectric body 13, and the like. is there.

  The set temperature of the piezoelectric body 13 by the heating / cooling control means 45 is more preferably as low as possible within the above control temperature range.

  According to the present embodiment, driving is performed by controlling the temperature of the piezoelectric body 13 within a control temperature range of 80 ° C. or less higher than the dew point at which dew condensation occurs on the piezoelectric body 13 in the usage environment of the piezoelectric actuator 2. be able to. According to this embodiment, it is possible to provide a piezoelectric actuator 2 having excellent durability and a method for driving a piezoelectric element.

This embodiment is effective when the amount of heat generated from the piezoelectric body 13 is large.
The calorific value W from the piezoelectric body 13 is expressed by the following formula.
W = 1 / 2ω · Cp · Vpp ² · tan δ
(Where Cp is the capacitance, Vpp is the voltage amplitude (difference between the lowest voltage and the highest voltage of the driving waveform voltage), and tan δ is the dielectric loss. Ω = 2πf, Cp = ε0 · εr · S / d (Where d is the film thickness, S is the area, εr is the relative dielectric constant of the substance, and ε0 is the dielectric constant of the vacuum.)

  As can be seen from the above equation, the amount of heat generated from the piezoelectric body 13 tends to increase as the thickness of the piezoelectric body 13 decreases. Therefore, this embodiment is effective when the piezoelectric body 13 is a piezoelectric film, and is particularly effective when the piezoelectric body 13 is a piezoelectric film having a thickness of 10 μm or less. The lower limit of the film thickness of the piezoelectric film is not particularly limited, and is, for example, 500 nm or more.

  As can be seen from the above equation, the amount of heat generated from the piezoelectric body 13 tends to increase as the drive frequency of the piezoelectric body 13 increases. Therefore, this embodiment is effective when the drive frequency of the piezoelectric body 13 by the drive control means 20 is 30 kHz or more, more effective when it is 50 kHz or more, and particularly effective when it is 100 kHz.

As can be seen from the above equation, the amount of heat generated from the piezoelectric body 13 tends to increase as the voltage amplitude of the piezoelectric body 13 increases. Therefore, this embodiment is effective when the difference (Vpp) between the minimum voltage and the maximum voltage of the drive waveform voltage of the piezoelectric body 13 by the drive control means 20 is 20 V or more, and further effective when it is 25 V or more. It is particularly effective when it is 30 V or higher.

The composition of the piezoelectric body 13 is not particularly limited.
Examples of the piezoelectric body 13 include those containing one or more perovskite oxides represented by the following general formula.
General formula ABO ₃
(In the formula, A: an element at the A site, and at least one element selected from the group consisting of Pb, Ba, La, Sr, Bi, Li, Na, Ca, Cd, Mg, K, and a lanthanide element) ,
B: Element of B site, which is composed of Ti, Zr, V, Nb, Ta, Sb, Cr, Mo, W, Mn, Sc, Co, Cu, In, Sn, Ga, Zn, Cd, Fe and Ni At least one element selected from the group,
O: oxygen element,
The ratio of the total number of moles of the A-site element, the total number of moles of the B-site element and the number of moles of the oxygen element is 1: 1: 3 as a standard, but these mole ratios are within a range that can take a perovskite structure. It may deviate from the molar ratio. )

As the perovskite oxide represented by the above general formula,
Lead titanate, lead zirconate titanate (PZT), lead zirconate, lead lanthanum titanate, lead lanthanum zirconate titanate, lead zirconium niobate titanate titanate, lead niobium zirconium titanate titanate, titanium titanate zinc niobate Lead-containing compounds such as lead acid, and mixed crystal systems thereof;
Non-lead-containing compounds such as barium titanate, barium strontium titanate, bismuth sodium titanate, bismuth potassium titanate, sodium niobate, potassium niobate, lithium niobate, bismuth ferrite, and mixed crystal systems thereof may be mentioned.

The piezoelectric actuator 2 and the driving method of the piezoelectric element of this embodiment can be preferably applied to the case where the piezoelectric body 13 includes PZT represented by the following general formula (P) or a perovskite oxide of its substitution system.
A _a (Zr _x , Ti _y , M _b-xy ) _b O _c (P)
(In the formula, A: an element of A site, and at least one element including Pb.
M represents one or more metal elements.
0 <x <b, 0 <y <b, 0 ≦ b−xy.
Although a: b: c = 1: 1: 3 is a standard, these molar ratios may deviate from the reference molar ratio within a range where a perovskite structure can be taken. )

M, which is one or more substitution elements of the B site, is not particularly limited.
It is known that PZT to which various donor ions having a valence higher than that of a substituted ion are added has improved characteristics such as piezoelectric performance as compared with intrinsic PZT. M is preferably one or more donor ions having a valence larger than that of tetravalent Zr or Ti. Examples of such donor ions include V ⁵⁺ , Nb ⁵⁺ , Ta ⁵⁺ , Sb ⁵⁺ , Mo ⁶⁺ , and W ⁶⁺ . That is, the perovskite oxide (P) is 0 <b-xy, and M is a perovskite oxide (M) containing at least one element selected from the group consisting of V, Nb, Ta, and Sb. PX).

  In the perovskite type oxide (P), elements other than Pb that may be contained in the A site are not particularly limited, and are preferably dona ions, specifically, at least one kind of various lanthanoids such as Bi and La. Elements are preferred.

  The ink jet recording head (liquid ejecting apparatus) 3 generally includes an ink chamber (liquid storing chamber) 61 in which ink is stored in the piezoelectric actuator 2 and an ink discharging port (liquid that discharges ink from the ink chamber 61 to the outside). An ink nozzle (liquid storing and discharging member) 60 having a discharge port 62 is attached. An ink supply port 63 for supplying ink to the ink chamber 61 from an ink storage / loading unit 114 of the ink jet recording apparatus 100 described later is opened in the substrate 11 that also serves as a vibration plate.

  In the ink jet recording head 3, the electric field strength applied to the piezoelectric element 1 is increased / decreased to expand / contract the piezoelectric element 1, thereby controlling the ejection of ink from the ink chamber 61 and the ejection amount.

  Instead of attaching the ink nozzle 60 which is a member independent of the substrate 11, a part of the substrate 11 may be processed into the ink nozzle 60. For example, when the substrate 11 is made of a laminated substrate such as an SOI substrate, the substrate 11 is etched from the back side to form the ink chamber 61, and the ink nozzle 60 can be formed by processing the substrate itself.

  The piezoelectric actuator 2 and the ink jet recording head 3 of the present embodiment are configured as described above. According to this embodiment, it is possible to provide a piezoelectric actuator 2 having excellent durability and a method for driving a piezoelectric element.

“Inkjet recording head of second embodiment”
With reference to FIG. 2, the structure of a piezoelectric actuator (piezoelectric device) according to a second embodiment of the present invention and an ink jet recording head (liquid ejection device) including the same will be described. The basic configuration of the piezoelectric actuator 4 and the ink jet recording head 5 of this embodiment is the same as that of the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the piezoelectric actuator 4 of the present embodiment, as in the first embodiment,
An external temperature measuring means for measuring the external temperature;
An external humidity measuring means for measuring external humidity;
Based on the measurement results obtained by the external temperature measuring means and the external humidity measuring means, and the relationship between the external temperature and external humidity acquired in advance and the dew point at which dew condensation occurs on the piezoelectric body 13, the piezoelectric actuator 4 is used in the usage environment. Dew point measuring means for obtaining a dew point at which condensation occurs on the body 13 is provided.

  Also in this embodiment, as an external temperature measuring means, an external humidity measuring means, and a dew point measuring means, the temperature and humidity of the external environment are measured, and the dew point at which dew condensation occurs on the piezoelectric body 13 in the usage environment of the piezoelectric actuator 4 And a temperature / humidity sensor 30 for displaying the temperature and humidity of the external environment and the determined dew point.

  Also in the present embodiment, as in the first embodiment, the piezoelectric body temperature control means 50 that controls the temperature of the piezoelectric body 13 within a control temperature range that is higher than the dew point measured by the dew point measurement means and is 80 ° C. or less is provided. It has been.

  In order to stably suppress the temperature of the piezoelectric body 13 from becoming the dew point or lower, the piezoelectric body temperature control means 50 sets the temperature of the piezoelectric body 13 to a dew point of + 2 ° C. or higher and 80 ° C. or lower measured by the dew point measuring means. It is preferable to control the temperature within the control temperature range.

  The piezoelectric body temperature control means 50 is particularly preferably one that controls the temperature as low as possible within the control temperature range. Specifically, it is more preferable that the piezoelectric body temperature control means 50 controls the temperature of the piezoelectric body 13 within a control temperature range of dew point + 2 ° C. to 60 ° C. measured by the dew point measurement means, It is particularly preferable to control the temperature of the piezoelectric body 13 within a control temperature range of dew point + 2 ° C. to 40 ° C. measured by the dew point measuring means.

  In the present embodiment, as the piezoelectric body temperature control means 50, the piezoelectric body temperature measurement means 51 that measures the temperature of the piezoelectric body 13, the measurement result by the piezoelectric body temperature measurement means 51, and the control temperature range are used. And a piezoelectric temperature adjusting means 52 for adjusting the temperature of the piezoelectric material.

  In the present embodiment, a thermocouple for measuring the temperature of the piezoelectric body 13 is provided as the piezoelectric body temperature measuring means 51. In this embodiment, the thermocouple is provided so as to contact the lower electrode 12, but the position is not particularly limited as long as the temperature of the piezoelectric body 13 can be measured. As the piezoelectric body temperature measuring means 51, a thermography, an infrared microscope, or the like can be used in addition to the thermocouple.

  In the present embodiment, as the piezoelectric body temperature adjusting means 52, a fluid circulation rod 53 in which a fluid circulates and a fluid temperature control means 54 for adjusting the temperature of the fluid in the fluid circulation rod 53 are provided.

  The fluid temperature control means 54 includes a heating means 55 that heats the fluid in the fluid circulation cage 53, a cooling means 56 that cools the fluid in the fluid circulation cage 53, a measurement result by the piezoelectric body temperature measurement means 51, and the piezoelectric body 13. Based on the control temperature range, the set temperature of the piezoelectric body 13 is determined, and the heating means 55 and the cooling means 56 are controlled so that the piezoelectric body 13 reaches this set temperature, thereby controlling the temperature of the fluid in the fluid circulation rod 53. The control device includes a heating / cooling control unit 57 configured by a control circuit and the like, a display unit 58 that displays a measurement result by the piezoelectric body temperature measurement unit 51, a display unit 59 that displays a set temperature of the piezoelectric body 13, and the like.

  The composition of the fluid in the fluid circulation gutter 53 is not particularly limited. The fluid in the fluid circulation gutter 53 may be an inorganic fluid such as water or an organic fluid such as ethylene glycol or various oils. The fluid in the fluid circulation gutter 53 may be a single material or a mixture. The fluid in the fluid circulation gutter 53 may be one in which some solute is dissolved in the solvent.

  The set temperature of the piezoelectric body 13 by the fluid temperature control means 54 is more preferably as low as possible within the above control temperature range.

  Also according to the present embodiment, driving is performed by controlling the temperature of the piezoelectric body 13 within a control temperature range of 80 ° C. or less higher than the dew point at which dew condensation occurs on the piezoelectric body 13 in the usage environment of the piezoelectric actuator 2. Can do. Also according to this embodiment, it is possible to provide a piezoelectric actuator 4 having excellent durability and a driving method of the piezoelectric element.

"Inkjet recording device"
With reference to FIG. 3 and FIG. 4, a configuration example of an ink jet recording apparatus including the ink jet recording head 3 of the above embodiment will be described. 3 is an overall view of the apparatus, and FIG. 4 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”) 3K, 3C, 3M, and 3Y provided for each ink color, and each head 3K, An ink storage / loading unit 114 that stores ink to be supplied to 3C, 3M, and 3Y, 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.
Each of the heads 3K, 3C, 3M, and 3Y forming the printing unit 102 is the ink jet recording head 3 of the above 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. 3, 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 print 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. 3 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. 4). Each of the print heads 3K, 3C, 3M, and 3Y 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 3K, 3C, 3M, and 3Y 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 3K, 3C, 3M, 3Y 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.

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

(Production of piezoelectric element)
A Si film having a thickness of 20 nm and a (111) Ir film having a thickness of 150 nm were sequentially formed on the Si wafer as a lower electrode by sputtering. An Nb-PZT piezoelectric film was formed on the lower electrode. The conditions for forming the piezoelectric film were as follows.
Film forming apparatus: RF sputtering apparatus ("ferroelectric film forming sputtering apparatus MPS type" manufactured by ULVAC),
Target: 120 mmφ Pb _1.3 ((Zr _0.52 Ti _0.48 ) _0.88 Nb _0.12 ) O ₃ sintered body,
Deposition power: 500W
Substrate / target distance: 60 mm,
Deposition pressure: 0.3 Pa
Deposition gas: Ar / O ₂ = 97.5 / 2.5 (molar ratio).
A Ti / Pt upper electrode (Ti: 20 nm thickness / Pt: 150 nm thickness) is formed on the Nb-PZT film (Ti functions as an adhesion layer, and Pt mainly functions as an electrode), 5 × 12. The piezoelectric element was obtained by cutting to a size of 0.5 mm ² .

(Durability test)
For the piezoelectric element manufactured under the same conditions, an average life test was performed by changing the temperature and humidity of the external environment and the temperature of the piezoelectric film.
The temperature and humidity of the external environment were controlled by a constant temperature and humidity chamber.
The temperature of the piezoelectric film was measured in three ways: thermography “TH7102FM” manufactured by NEC Sanei Co., Ltd., infrared microscope “FSV-GX7000” manufactured by Apiste Co., Ltd., and K thermocouple pasted on a sample.
Since thermography and infrared microscope display temperature differently depending on the emissivity of the surface material of the object, the actual temperature is read after comparing the actual film temperature and display temperature on the hot plate in advance. I did it. In either method, the difference between the actual film temperature and the display temperature was within ± 5 ° C.
An LCR meter is applied by applying a trapezoidal wave of −12.5 V ± 12.5 V and 100 kHz to the piezoelectric element, and turning off the voltage every 1 billion cycles (ie, 100 kHz × 1 billion cycles = 16.7 minutes). Then, tan δ at 1 V and 1 kHz was measured, and the point where tan δ exceeded 0.1 was obtained as the lifetime. The average of the lifespan measured at 20 locations was determined as “average life”.

(Test 1)
The average life was measured under conditions of an external environment of 40 ° C. and a relative humidity of 80%.
<Example 1>
An aluminum block painted in black of 50 mm × 50 mm × 10 mm size was placed on the back of the sample. The piezoelectric film was sufficiently dissipated, and the piezoelectric film was at the same temperature as the external environment. Under this condition, an average life test was conducted.
<Example 2, Comparative Example 1>
An average life test was conducted while heating the sample with a temperature-controlled silicon rubber heater and controlling the temperature. The temperature of the piezoelectric film was monitored by attaching a Teflon-coated K thermocouple on the film with Kapton tape (Teflon and Kapton are registered trademarks).
<Comparative Example 2>
The back of the sample was cooled with a Peltier device and held at 33 ° C., and an average life test was conducted. The temperature of the piezoelectric film was monitored by attaching a Teflon-coated K thermocouple on the film with Kapton tape (Teflon and Kapton are registered trademarks). Condensation was observed on the sample surface.
Table 1 shows the temperature and humidity of the external environment, the dew point in the external environment, and the driving temperature of the piezoelectric film in Example 1-2 and Comparative Example 1-2.
<Evaluation results>
The evaluation results are shown in Table 1.
As shown in Table 1, it was found that the deterioration of the piezoelectric film becomes remarkable when driving at 90 ° C. or higher. It was also found that when the piezoelectric film was cooled to a dew point or lower, condensation occurred in the sample and the deterioration of the piezoelectric film became significant. It has been found that high durability can be obtained by controlling the temperature of the piezoelectric film to be higher than the dew point and not higher than 80 ° C.

(Test 2)
The average life was measured under conditions of an external environment of 25 ° C. and a relative humidity of 50%.
<Example 3-4, Comparative Example 3-5>
The temperature control of the piezoelectric film was performed in the same manner as in Test 1. This test tended to have a longer life than Test 1. For this reason, it was difficult to continue the life test for those whose average life exceeded 150 billion dots. Therefore, extrapolation was performed using the data up to 150 billion dots using the least squares method of Weibull plot, and the estimated average life was calculated. Asked.
Table 2 shows the temperature and humidity of the external environment, the dew point in the external environment, the driving temperature of the piezoelectric film, and the evaluation results in Example 3-4 and Comparative Example 3-5.
As shown in Table 2, it was found that the deterioration of the piezoelectric film becomes remarkable when driving at 90 ° C. or higher. It was also found that when the piezoelectric film was cooled to a dew point or lower, condensation occurred in the sample and the deterioration of the piezoelectric film became significant. It has been found that high durability can be obtained by controlling the temperature of the piezoelectric film to be higher than the dew point and not higher than 80 ° C.

(Test 3)
The average life was measured under conditions of an external environment of 25 ° C. and a relative humidity of 50%.
<Example 5, Comparative Example 6>
No particular temperature control of the piezoelectric film was performed.
In Comparative Example 6, as in Tests 1 and 2, a test was performed by applying a trapezoidal wave of −12.5 V ± 12.5 V and 100 kHz. Under the condition of a driving frequency of 100 kHz, heat generation from the piezoelectric film was large, and the temperature of the piezoelectric film rose to 90 ° C. immediately after the start of the test, and deterioration of the piezoelectric film was observed.
In Example 5, a test was performed by applying a trapezoidal wave of −12.5 V ± 12.5 V and 20 kHz. Since the test time of 5 times the drive frequency of 100 kHz is required under the condition of the drive frequency of 20 kHz, the average life was obtained by extrapolation as in Test 2. Under the condition of a driving frequency of 20 kHz, there was little heat generation from the piezoelectric film, the temperature of the piezoelectric film at the beginning of the test was 40 ° C., and about 40 ° C. was maintained thereafter. In Example 5, the piezoelectric film had a long life.
Table 3 shows the temperature and humidity of the external environment, the dew point in the external environment, the initial driving temperature of the piezoelectric film, and the evaluation results in Example 5 and Comparative Example 6.
If the drive frequency is 20 kHz or less, there is a case where the life is long even if the temperature is not particularly controlled. However, if the drive frequency is 30 kHz or more, the heat generated from the piezoelectric film is large, and the present invention for performing temperature control is effective.

  The piezoelectric device and the driving method of the piezoelectric element of the present invention are 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. The present invention is preferably applicable to ferroelectric elements such as piezoelectric actuators and ferroelectric memories.

1 Piezoelectric element 2, 4 Piezoelectric actuator (piezoelectric device)
3,5 Inkjet recording head (liquid ejection device)
3K, 3C, 3M, 3Y Inkjet recording head (liquid ejection device)
11 Substrate also serving as a diaphragm 12, 14 Electrode 13 Piezoelectric body 20 Drive control means 30 Temperature / humidity sensor (external temperature measurement means, external humidity measurement means, dew point measurement means)
40, 50 Piezoelectric temperature control means 41, 51 Piezoelectric temperature measurement means 42, 52 Piezoelectric temperature adjustment means 43, 55 Heating means 44, 56 Cooling means 45, 57 Heating / cooling control means 60 Ink nozzle (liquid storage and discharge member)
61 Ink chamber (liquid storage chamber)
62 Ink ejection port (liquid ejection port)
100 Inkjet recording device

Claims (11)

A piezoelectric element including a piezoelectric body and an electrode for applying a voltage to the piezoelectric body;
In a piezoelectric device comprising drive control means for controlling the applied voltage and applied frequency of the piezoelectric element,
An external temperature measuring means for measuring an external temperature of the piezoelectric device;
External humidity measuring means for measuring the external humidity of the piezoelectric device;
Based on the measurement results by the external temperature measurement means and the external humidity measurement means, and the relationship between the external temperature and external humidity acquired in advance and the dew point at which dew condensation occurs on the piezoelectric body, under the usage environment of the piezoelectric device. Dew point measuring means for obtaining a dew point at which dew condensation occurs on the piezoelectric body;
A piezoelectric device comprising: a piezoelectric body temperature control means for controlling the temperature of the piezoelectric body within a control temperature range higher than the dew point measured by the dew point measuring means and not higher than 80 ° C. The piezoelectric body temperature control means includes
Piezoelectric body temperature measuring means for measuring the temperature of the piezoelectric body;
2. The piezoelectric device according to claim 1, further comprising: a piezoelectric body temperature adjusting unit that adjusts a temperature of the piezoelectric body based on a measurement result by the piezoelectric body temperature measuring unit and the control temperature range. The piezoelectric body temperature adjusting means includes:
Heating means for heating the piezoelectric body;
Cooling means for cooling the piezoelectric body;
The piezoelectric device according to claim 2, further comprising a heating / cooling control unit that controls the heating unit and the cooling unit. The piezoelectric body temperature control means includes
The temperature of the piezoelectric body is controlled within the control temperature range of the dew point + 2 ° C to 40 ° C measured by the dew point measuring means. Piezoelectric device.   The piezoelectric device according to claim 1, wherein the piezoelectric body is a piezoelectric film.   The piezoelectric device according to claim 5, wherein the piezoelectric body is a piezoelectric film having a thickness of 10 μm or less.   The piezoelectric device according to claim 1, wherein a driving frequency of the piezoelectric body by the drive control unit is 30 kHz or more.   The piezoelectric device according to claim 1, wherein a difference (Vpp) between a minimum voltage and a maximum voltage of a drive waveform voltage of the piezoelectric body by the drive control unit is 20 V or more. The piezoelectric device according to claim 1, wherein the piezoelectric body includes a perovskite oxide represented by the following general formula (P).
A _a (Zr _x , Ti _y , M _b-xy ) _b O _c (P)
(In the formula, A: an element of A site, and at least one element including Pb.
M represents one or more metal elements.
0 <x <b, 0 <y <b, 0 ≦ b−xy.
Although a: b: c = 1: 1: 3 is a standard, these molar ratios may deviate from the reference molar ratio within a range where a perovskite structure can be taken. ) In a piezoelectric element driving method including a piezoelectric body and an electrode for applying a voltage to the piezoelectric body,
The piezoelectric element is driven by controlling the temperature of the piezoelectric body within a control temperature range of 80 ° C. or less higher than a dew point at which dew condensation occurs on the piezoelectric body under the usage environment of the piezoelectric device. Driving method.   A piezoelectric device according to claim 1, and a liquid discharge member provided adjacent to the piezoelectric device, wherein the liquid discharge member includes a liquid storage chamber in which a liquid is stored, and the piezoelectric device. A liquid discharge apparatus comprising: a liquid discharge port through which the liquid is discharged from the liquid storage chamber in response to application of the voltage to the body.

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