JP5043336B2 - Inkjet printer head - Google Patents

Description

The present invention relates to an inkjet printer head provided with a piezoelectric actuator .

A piezoelectric actuator using the electrostrictive characteristics of a piezoelectric ceramic is used as a drive source for an inkjet printer head or the like. Moreover, as a suitable example of a piezoelectric actuator, when a voltage is applied in the thickness direction, a plate-shaped one including a transverse vibration mode piezoelectric ceramic layer that expands and contracts in a plane direction orthogonal to the thickness direction can be cited.
The plate-like piezoelectric actuator is usually formed by laminating a pair of electrode layers for applying a voltage in the thickness direction of the piezoelectric ceramic layer and expanding and contracting in the surface direction on both surfaces of the piezoelectric ceramic layer. On the outer surface of the piezoelectric ceramic layer, a diaphragm for bending and deforming the piezoelectric actuator in the thickness direction is laminated by restricting expansion and contraction in the surface direction of the piezoelectric ceramic layer, or one electrode layer is vibrated. It is configured by integrating with a plate.

  The plate-like piezoelectric actuator having the laminated structure is used in a state in which a piezoelectric ceramic layer is polarized in a thickness direction, and the polarization direction (“positive polarization direction”) is connected to the piezoelectric ceramic layer via a pair of electrode layers. When the voltage is applied in the same direction as that (referred to as “forward direction”), the piezoelectric ceramic layer contracts in the plane direction. However, since the diaphragm (or the electrode layer that also serves as the diaphragm) is fixed to one surface of the piezoelectric ceramic layer and expansion and contraction in the surface direction is restricted, the piezoelectric actuator has a surface on which the diaphragm is laminated. It bends and deforms so as to protrude in the thickness direction.

On the other hand, when a voltage in the direction opposite to the positive polarization direction is applied to the piezoelectric ceramic layer via a pair of electrode layers, the piezoelectric ceramic layer expands in the plane direction. The surface opposite to the surface where the layers are stacked is bent and deformed so as to protrude in the thickness direction.
In Patent Document 1, in order to increase the displacement amount of the piezoelectric actuator in the thickness direction as much as possible, the forward and reverse voltages are alternately applied to the piezoelectric ceramic layer via a pair of electrode layers. It is described that a driving voltage pulse that is replaced with is applied.
JP-A-11-97755

  Further, in the invention of Patent Document 1, particularly when the piezoelectric ceramic layer is made of a ferroelectric, the polarization direction of each crystal grain forming the piezoelectric ceramic layer is determined by applying a reverse voltage during driving. In order to prevent inversion, the absolute value of the reverse voltage applied to the piezoelectric ceramic layer is set to be equal to or less than the coercive electric field strength Ec of the piezoelectric ceramic layer. However, with such a setting, it is assumed that the driving method described in Patent Document 1 is used to apply a driving voltage pulse in which the forward and reverse voltages are alternately switched to the piezoelectric ceramic layer. However, there is a limit to the effect of increasing the displacement amount of the bending deformation in the thickness direction of the piezoelectric actuator.

  On the other hand, in the above driving method, the absolute value of the reverse voltage applied to the piezoelectric ceramic layer is set to Patent Document 1 in order to further increase the displacement amount of the bending deformation in the thickness direction of the piezoelectric actuator. If the driving is repeated with the value exceeding the coercive electric field strength Ec of the piezoelectric ceramic layer, the crystal grains polarized in the normal positive polarization direction (“positive polarization crystal” A large amount of crystal grains polarized in the opposite direction (referred to as “inverted polarized crystal grains” and having a stretching behavior opposite to that of positively polarized crystal grains) are generated. Then, when viewed as a whole of the piezoelectric ceramic layer, there is a problem that the ratio of the reversely polarized crystal grains is greatly increased, and the displacement amount of the piezoelectric actuator in the thickness direction is greatly decreased with time. .

The object of the present invention is excellent in durability, and even if the piezoelectric ceramic layer is driven by a driving method in which a reverse voltage exceeding the coercive electric field strength Ec is applied, the displacement amount of the bending deformation in the thickness direction changes with time. Another object of the present invention is to provide an ink jet printer head provided with a piezoelectric actuator that is not likely to be greatly reduced.

  As described above, when the reverse voltage exceeding the coercive electric field strength Ec is applied to the piezoelectric ceramic layer, the displacement amount of the bending deformation of the piezoelectric actuator greatly decreases with time. As described above, the polarization direction of the individual crystal grains forming the piezoelectric ceramic layer is reversed by the application of the voltage in the reverse direction, and the ratio of the inverted polarization crystal grains when viewed as a whole of the piezoelectric ceramic layer is greatly increased. Because.

  According to the inventors' investigation, the main cause is that the polarization direction existing in the piezoelectric ceramic layer made of the piezoelectric ceramic material is tilted by 90 ° with respect to the positive polarization direction. Crystal grains (hereinafter referred to as “domain rotation crystal grains”). When a voltage exceeding the coercive electric field strength Ec of the piezoelectric ceramic layer is applied in the forward direction or the reverse direction when the piezoelectric actuator is driven, the domain-rotated crystal grains cause a 90 ° rotational displacement in the voltage application direction. Thus, it contributes to the bending deformation in the thickness direction of the piezoelectric actuator together with the piezoelectric displacement caused by the positively polarized crystal grains.

  However, the domain-rotated crystal grains are polarized in the reverse direction when applied with a reverse voltage exceeding the coercive electric field strength Ec as compared to the positive-polarized crystal grains. high. Therefore, the more the domain rotating crystal grains exist in the piezoelectric ceramic layer, the more the reverse voltage of the high voltage is repeatedly applied when the piezoelectric actuator is driven, so that the piezoelectric ceramic layer as a whole is viewed. As a result, the ratio of the reversely polarized crystal grains is greatly increased, and the displacement amount of the piezoelectric actuator in the thickness direction is greatly reduced over time. Therefore, it is important to reduce the proportion of domain rotating crystal grains present in the piezoelectric ceramic layer.

As described above, when a voltage exceeding the coercive electric field strength Ec in the forward direction or the reverse direction is applied when the piezoelectric actuator is driven, the domain-rotated crystal grain is rotated by 90 ° in the voltage application direction. This contributes to bending deformation in the thickness direction of the piezoelectric actuator along with piezoelectric displacement caused by positively polarized crystal grains. That is, when the voltage exceeding the coercive electric field strength Ec is applied, the total amount ε of the displacement of the piezoelectric actuator in the thickness direction is expressed by equation (1):
ε = ε ^P31 + ε ^d31 (1)
As shown in FIG. 4, the displacement amount due to the 90 ° rotational displacement of the domain rotation crystal grain, that is, the sum of the 90 ° rotational displacement component ε ^d31 and the displacement amount due to the piezoelectric displacement of the positive polarization crystal grain, ie, the piezoelectric displacement component ε ^P31 expressed.

Therefore, the inventor prescribes the ratio of the domain rotation crystal grains within the range of the ratio (180 ° domain ratio) of the piezoelectric displacement component ε ^P31 to the total displacement ε of the deformation in the thickness direction of the piezoelectric actuator. As a result of examining this, if the piezoelectric ceramic layer is applied with a voltage exceeding 1.2 times the coercive electric field strength Ec to bend and deform in the thickness direction, the ratio should be 0.6 or more. In addition, since the ratio of the domain rotating crystal grains is small, the durability is excellent, even if the piezoelectric ceramic layer is driven by a driving method in which a reverse voltage exceeding the coercive electric field strength Ec is repeatedly applied. It has been found that a piezoelectric actuator can be obtained in which the amount of displacement of the bending deformation does not significantly decrease with time.

Therefore, the invention described in claim 1 includes a plurality of pressurizing chambers, a substrate including a plurality of nozzles respectively communicating with the plurality of pressurizing chambers, and a plate-like piezoelectric actuator stacked on the substrate. An inkjet printer head,
The piezoelectric actuator includes a diaphragm having a size covering the plurality of pressurizing chambers, a common electrode, and a piezoelectric ceramic layer, and a plurality of individual electrode layers provided corresponding to the plurality of pressurizing chambers, respectively. Including
The area of the individual electrode layer is 0.8 times or more and less than 1.0 times the area of the pressurizing chamber,
The piezoelectric ceramic layer has an average crystal grain size of not less than 0.5 μm and not more than 2.5 μm, and the piezoelectric ceramic layer is sandwiched between the common electrode layer and the individual electrode layer and has a voltage in the thickness direction. by but is applied to stretch in the plane direction orthogonal to the thickness direction, and deformed in the thickness direction, and the piezoelectric ceramic layer, more than 1.2 times the coercive field strength Ec of the piezoelectric ceramic layer Formula (1) when applying voltage to bend and deform in the thickness direction:
ε = ε ^P31 + ε ^d31 (1)
(In the equation, ε ^P31 represents the piezoelectric displacement component of the displacement amount, and ε ^d31 represents the 90 ° rotational displacement component of the displacement amount.)
The ratio of the piezoelectric displacement component ε ^P31 to the total displacement ε expressed by is an ink jet printer head characterized by being 0.6 or more.

The piezoelectric ceramic layer is preferably made of a piezoelectric ceramic mainly composed of lead zirconate titanate .

1, Lee inkjet purine meter size EBEP head 2 of the present invention, is an enlarged cross-sectional view showing an example of the embodiment.
Referring to FIG. 1, an ink jet printer head 2 of this example communicates with a pressurizing chamber 3 filled with ink and the pressurizing chamber 3, and ejects ink in the pressurizing chamber 3 as ink droplets. Including a substrate 6 formed by arranging a plurality of droplet discharge portions 5 having nozzles 4 for arranging in a plane direction, and a piezoelectric ceramic layer 7 having a size covering the plurality of pressure chambers 3 of the substrate 6. And a plate-like piezoelectric actuator 1 laminated on the substrate 6.

  The piezoelectric actuator 1 is disposed corresponding to each pressurizing chamber 3 and individually applied with a voltage, thereby individually bending and deforming in the thickness direction, and a plurality of piezoelectric deformation regions 8. The area 8 is disposed so as to surround the area 8 and is partitioned into a restrained area 9 which is fixed to the substrate 6 and prevented from being deformed. Also, the piezoelectric actuator 1 in the example shown in the figure is laminated in order on the upper surface of the piezoelectric ceramic layer 7, on the individual electrode layer 10 formed individually for each pressurizing chamber 3, and on the lower surface of the piezoelectric ceramic layer 7. Both have a so-called unimorph type configuration including a common electrode layer 11 and a diaphragm 12 having a size covering the plurality of pressurizing chambers 3.

  The piezoelectric ceramic layer 7 is formed of, for example, a piezoelectric material such as PZT, and is previously polarized in the positive polarization direction to give a transverse vibration mode piezoelectric deformation characteristic. A forward direction, that is, a positive polarization direction of the piezoelectric ceramic layer 7, in an arbitrary piezoelectric deformation region 8 of the piezoelectric actuator 1 via the individual electrode layer 10 corresponding to the piezoelectric deformation region 8 and the common electrode layer 11. When a voltage in the same direction is applied, the region sandwiched between the electrode layers 10 and 11 of the piezoelectric ceramic layer 7 contracts in the plane direction of the layer. However, since the lower surface of the piezoelectric ceramic layer 7 is fixed to the diaphragm 12 via the common electrode layer 11, when the region contracts, the piezoelectric deformation region 8 moves in the direction of the pressurizing chamber 3. To bend and deform.

  In addition, when a voltage in the reverse direction is applied to an arbitrary piezoelectric deformation region 8 of the piezoelectric actuator 1 via the individual electrode layer 10 corresponding to the piezoelectric deformation region 8 and the common electrode layer 11, the piezoelectric A region sandwiched between the electrode layers 10 and 11 of the ceramic layer 7 extends in the plane direction of the layer, and accordingly, the piezoelectric deformation region 8 is opposite to the direction of the pressurizing chamber 3. It bends and deforms so as to protrude in the direction. Therefore, for example, as described above, the drive voltage pulse in which the forward voltage and the reverse voltage are alternately switched to the arbitrary piezoelectric deformation region 8 of the piezoelectric actuator 1 via both electrode layers 10 and 11. Is applied, the piezoelectric deformation region 8 vibrates in the thickness direction of the piezoelectric actuator 1, and the ink in the pressurizing chamber 3 pressurized by the vibration is ejected as an ink droplet through the nozzle 4.

In the present invention, a voltage exceeding 1.2 times the coercive field strength Ec of the piezoelectric ceramic layer 7 is applied to the piezoelectric deformation region 8 of the piezoelectric actuator 1 via both electrode layers 10 and 11 to bend in the thickness direction. Equation (1) when transformed:
ε = ε ^P31 + ε ^d31 (1)
(In the equation, ε ^P31 represents a piezoelectric displacement component of the displacement amount, and ε ^d31 represents a 90 ° rotational displacement component of the displacement amount.)
The domain rotation is present in the piezoelectric ceramic layer 7 made of a piezoelectric ceramic material polycrystal so that the ratio of the piezoelectric displacement component ε ^P31 to the total displacement ε represented by The proportion of crystal grains is limited.

  For this reason, the piezoelectric ceramic layer 7 suppresses a significant increase in the ratio of inversion crystal grains due to the application of a reverse voltage when viewed as a whole of the region corresponding to the piezoelectric deformation region 8. The displacement amount of the bending deformation in the thickness direction of the actuator 1 can be prevented from greatly decreasing with time, and the piezoelectric actuator 1 is excellent in durability. For example, the piezoelectric ceramic layer 7 has a coercive electric field strength. Even if it is driven by a driving method in which a reverse voltage exceeding Ec is applied, the displacement amount of the bending deformation in the thickness direction is not likely to greatly decrease with time.

  Therefore, for example, when the piezoelectric actuator 1 is driven by applying a drive voltage pulse in which the forward and reverse voltages are alternately switched, the voltage in both directions is increased to a high voltage exceeding the coercive electric field strength Ec. By setting, it is possible to make the displacement amount of the bending deformation in the thickness direction larger than the current amount. In addition, the piezoelectric actuator can be driven by applying a drive voltage pulse or the like in which a voltage of 0 V and a forward direction or a voltage of 0 V and a reverse direction are repeated. By setting the voltage to a high voltage exceeding the coercive electric field strength Ec, it is possible to further increase the displacement amount of the bending deformation in the thickness direction than the current state.

  Further, the piezoelectric actuator 1 can be driven at a higher speed than the current state. For example, when driving by applying a driving voltage pulse in which the forward voltage and the reverse voltage are alternately switched, the driving can be favorably performed in a frequency range of 0.01 to 25 kHz. This is because the piezoelectric displacement of the positively polarized crystal grains has a higher response speed than the 90 ° rotational displacement of the domain rotating crystal grains.

Further, the piezoelectric actuator 1 can be driven in a wider temperature range than the current state. Specifically, it can be driven satisfactorily in the range of -20 to + 180 ° C. This is because the piezoelectric displacement of the positively polarized crystal grains is less temperature dependent than the 90 ° rotational displacement of the domain rotating crystal grains.
The ratio of the piezoelectric displacement component ε ^P31 to the total displacement ε is preferably as large as possible even within the above range, and 1.0 is the most ideal in terms of durability of the piezoelectric actuator 1. is there. That is, it is ideal that the region corresponding to the piezoelectric deformation region 8 in the piezoelectric ceramic layer 7 does not include any domain rotation crystal grains. However, since it is not easy to form such a piezoelectric ceramic layer 7 and the productivity of the piezoelectric actuator 1 may be reduced, the displacement of the piezoelectric actuator 1 is considered in consideration of the balance between the durability of the piezoelectric actuator 1 and the productivity. The ratio of the piezoelectric displacement component ε ^P31 to the total amount ε is particularly preferably 0.7 to 0.9 even within the above range.

In order to obtain the ratio, the voltage applied to the piezoelectric deformation region 8 of the piezoelectric actuator 1 is limited to a range exceeding 1.2 times the coercive electric field strength Ec of the piezoelectric ceramic layer 7. As described, the 90 ° rotational displacement component ε ^d31 has low responsiveness to the applied voltage, and below the above range, the domain rotating crystal existing in the region corresponding to the piezoelectric deformation region 8 in the piezoelectric ceramic layer 7. This is because the total amount of grains cannot be rotated and displaced by 90 °, so that the proportion of domain-rotated crystal grains existing in the region cannot be accurately grasped.

That is, as shown in FIG. 2 showing the relationship between the displacement amount (nm) of the piezoelectric deformation region 8 and the electric field strength (kV / cm), the piezoelectric deformation region 8 indicated by the line-●-●-in the drawing. The total displacement ε from 0 V to the coercive electric field strength Ec of the piezoelectric ceramic layer 7 substantially coincides with the piezoelectric displacement component ε ^P31 due to the piezoelectric displacement of the positively polarized crystal grains shown by the broken line in the figure. When the coercive electric field strength Ec is exceeded, the 90 ° rotational displacement component ε ^d31 due to the 90 ° rotational displacement of the domain rotating crystal grains gradually increases, and the voltage Ed that is 1.2 times the coercive electric field strength Ec is increased. The 90 ° rotational displacement component ε ^d31 is substantially constant in the subsequent range from the time when the ^value is exceeded. Therefore, by obtaining the ratio of the 90 ° rotational displacement component ε ^d31 to the total displacement ε of the piezoelectric deformation region 8 when a voltage exceeding 1.2 times the coercive electric field strength Ec is applied, the piezoelectric is obtained. In the ceramic layer 7, it is possible to accurately grasp the ratio of domain rotating crystal grains existing in the region corresponding to the piezoelectric deformation region 8.

Domain rotation crystal existing in a region corresponding to the piezoelectric deformation region 8 in the piezoelectric ceramic layer 7 so that the ratio of the piezoelectric displacement component ε ^P31 to the total displacement ε is in the range of 0.6 or more. In order to adjust the proportion of grains, the composition and particle size of the piezoelectric ceramic material forming the piezoelectric ceramic layer 7, firing conditions, polarization conditions (temperature, applied voltage, etc.) when the piezoelectric ceramic layer 7 is polarized, etc. It is conceivable to adjust so that domain-rotated crystal grains are not generated as much as possible.

In particular, when the composition, grain size, firing conditions, etc. of the piezoelectric ceramic material as a raw material are adjusted so that the average crystal grain size of the piezoelectric ceramic forming the piezoelectric ceramic layer 7 is 0.5 to 2.5 μm, the firing step In addition, in the subsequent polarization step, the generation of domain rotating crystal grains is suppressed, and a piezoelectric actuator having excellent durability in which the ratio of the piezoelectric displacement component ε ^P31 to the total displacement ε is 0.6 or more is formed. Is easy. This is proportional to the generation ratio of the domain rotation crystal grains and the crystal grain size of the piezoelectric ceramic forming the piezoelectric ceramic layer 7, and the domain rotation increases as the crystal grain size increases. This is because the generation ratio of crystal grains increases.

The average crystal grain size of the piezoelectric ceramic is preferably in the range of 0.5 to 2.5 μm. If the average crystal grain size is less than the above range, the grain size of the crystal grains contributing to the displacement becomes too small. This is because the total amount of displacement in the initial stage may be reduced. In addition, when the above range is exceeded, the generation of domain rotating crystal grains cannot be sufficiently suppressed, and the ratio of the piezoelectric displacement component ε ^P31 to the total displacement ε is less than 0.6, and the piezoelectric actuator This is because the durability of the steel may be reduced.

  Note that the average crystal grain size of the piezoelectric ceramic is 2.0 μm even within the above range in consideration of further suppressing the generation of domain rotating crystal grains and further improving the durability of the piezoelectric actuator. It is preferable that: In consideration of the balance between the durability of the piezoelectric actuator and preventing the total amount of displacement in the initial stage from becoming too small, the thickness is preferably 1.0 to 2.0 μm even within the above range.

However, the average crystal grain size of the piezoelectric ceramic is not an essential requirement for setting the ratio of the piezoelectric displacement component ε ^P31 to the total displacement ε of the piezoelectric actuator to be 0.6 or more. Even if it has a piezoelectric ceramic layer made of a piezoelectric ceramic having an average crystal grain size exceeding 2.5 μm, by devising the polarization method of the piezoelectric ceramic layer, the piezoelectric displacement component with respect to the total displacement ε of the piezoelectric actuator The ratio of ε ^P31 can be 0.6 or more.

For example, in the case of the piezoelectric actuator 1 having the structure shown in FIG. 1, the piezoelectric actuator 1 is formed in the area A _{1 in the} surface direction of the piezoelectric deformation region 8 surrounded by the restriction region 9 and in the piezoelectric deformation region 8. Further, the pressure chamber 3 is set such that the ratio A ₂ / A _{1 of} the individual electrode layer 10 to the area A _{2 in the} plane direction is 0.8 or more, particularly 0.9 or more and less than 1.0. By defining the opening area and the area of the individual electrode layer 10, the ratio of the piezoelectric displacement component ε ^P31 to the total displacement ε of the piezoelectric actuator can be 0.6 or more.

  This is because, after the piezoelectric ceramic layer 7 of the piezoelectric actuator 1 having the structure shown in FIG. 1 is laminated on the substrate 6, for example, in the high temperature polarization method, both electrode layers 10 are heated while being heated to a predetermined temperature. This is because a polarization process is performed by applying a direct-current voltage between 11 and 11. That is, in the piezoelectric actuator 1 that performs the polarization process, the individual electrode layer 10 between the piezoelectric ceramic layer 7 and the restraining region 9 around the individual electrode layer 10 in the region corresponding to the piezoelectric deformation region 8. The direction of the DC voltage applied between the electrode layers 10 and 11 does not coincide with the thickness direction (positive polarization direction) of the piezoelectric ceramic layer 7 in the gap region where no electrode is formed. The direction is slightly inclined toward the direction, and the rate of occurrence of domain-rotated crystal grains increases during the polarization treatment.

Therefore, in order to minimize the rate of occurrence of domain rotation crystal grains generated in the gap region around the individual electrode layer 10, it is conceivable to reduce the ratio of the gap region. The ratio A ₂ / A ₁ between the area A _{1 in the} plane direction of the piezoelectric deformation region 8 and the area A _{2 in the} plane direction of the individual electrode layer 10 is set to 0.8 or more, particularly 0.9 or more. Is preferred. The ratio A ₂ / A ₁ is preferably less than 1.0 when the ratio A ₂ / A ₁ is 1.0 or more, that is, the individual electrode layer 10 is larger than the piezoelectric deformation region 8. At the time of driving, a driving voltage is also applied to a region of the piezoelectric ceramic layer 7 corresponding to the constraining region 9 around the piezoelectric deformation region 8, and the driving efficiency of the piezoelectric deformation region 8 is reduced. Because.

  The configuration of the present invention is not limited to the example of the figure described above. For example, the piezoelectric ceramic layer 7 may be formed individually for each piezoelectric deformation region 8. In that case, the individual electrode layer 10 is generally formed on the individually formed piezoelectric ceramic layer 7 in the same shape and size as the piezoelectric ceramic layer 7. Generation | occurrence | production of area | region rotation crystal grain can be suppressed.

Therefore, for example, by using a piezoelectric ceramic layer 7 made of a piezoelectric ceramic having an average crystal grain size of 0.5 to 2.5 μm, the piezoelectric displacement component ε ^P31 with respect to the total displacement ε of the piezoelectric actuator By setting the ratio to 0.6 or more, the generation of domain rotating crystal grains can be suppressed and the durability of the piezoelectric actuator can be improved. In addition, various design changes can be made without departing from the scope of the present invention.

Example 1
Having the structure shown in FIG. 1, to produce an inkjet-purine meter size EBEP head 2. The piezoelectric ceramic layer 7, the common electrode layer 11, and the diaphragm 12 of the piezoelectric actuator 1 sandwich a metal paste layer between two green sheet layers containing a piezoelectric ceramic powder mainly composed of lead zirconate titanate. The laminated body was baked and integrally formed, and a metal paste was screen-printed thereon and baked to form the individual electrode layer 10, thereby producing a plate-like piezoelectric actuator 1.

From the result of measuring the crystal grain size of the individual crystal grains of the piezoelectric ceramic forming the piezoelectric ceramic layer 7 observed by a scanning electron microscope by the intercept method, the average crystal grain size of the piezoelectric ceramic was determined. It was 1.8 μm. The ratio A ₂ / A ₁ between the area A 1 in the plane direction of the piezoelectric deformation region 8 and the area A _{2 in the} plane direction of the individual electrode layer 10 was adjusted to be 0.9. Next, the piezoelectric actuator 1 was bonded to the substrate 6 using an adhesive, and then polarized by a high temperature polarization method, whereby the ink jet printer head 2 was manufactured.

The coercive electric field strength Ec of the piezoelectric ceramic layer 7 of the piezoelectric actuator 1 was 1.41 kV / cm. Further, while maintaining the temperature of the piezoelectric actuator 1 at room temperature (+5 to + 35 ° C.), the piezoelectric ceramic layer 7 has ± 1.83 kV / cm, a frequency of 0.1. The ratio of the piezoelectric displacement component ε ^P31 to the total amount of displacement ε when a driving voltage pulse of 01 Hz, in which forward and reverse voltages are alternately switched, is applied and deformed in the thickness direction is 0.61. Met.

  A driving voltage in which forward and reverse voltages of ± 1.83 kV / cm and a frequency of 1 kHz are alternately switched in the piezoelectric ceramic layer 7 while maintaining the temperature of the piezoelectric actuator 1 at room temperature (+5 to + 35 ° C.). After applying and driving a pulse for 1 billion cycles, while maintaining the same room temperature (+5 to + 35 ° C.) and driving by applying a driving voltage pulse having the same voltage and different frequency, The displacement amount of the center position in the surface direction of the piezoelectric deformation region 8 of the piezoelectric actuator 1 was measured. The relationship between the change rate (%) of the displacement from the initial value measured under the same conditions and the frequency (Hz) was plotted in FIG. From FIG. 3, the piezoelectric actuator 1 of Example 1 has a displacement change rate after 1 billion cycles within a frequency range of 0.01 to 25 kHz, and is suppressed to within −15.0%. It was confirmed that it was excellent in durability and could be driven well in the frequency range.

  Further, while maintaining the temperature of the piezoelectric actuator 1 at an arbitrary temperature of −20 to 180 ° C., forward and reverse voltages of ± 1.83 kV / cm, frequency 1 kHz are alternately applied to the piezoelectric ceramic layer 7. Of the piezoelectric actuator 1 when the drive voltage pulse having the same frequency and the same frequency is applied and driven while maintaining the same temperature after being applied and driven for 1 billion cycles. The displacement amount of the center position in the surface direction of the piezoelectric deformation region 8 was measured. Then, the relationship between the change rate (%) of the displacement amount from the initial value measured under the same conditions and the temperature (° C.) of the piezoelectric actuator 1 was plotted in FIG. From FIG. 4, the piezoelectric actuator 1 of Example 1 has a displacement change rate after 1 billion cycles within a temperature range of −20 to 180 ° C., both of which are suppressed to within −15.0%. It was confirmed that it was excellent in durability and could be driven well in the temperature range.

(Example 2)
The grain size of the piezoelectric ceramic powder mainly composed of lead zirconate titanate as a raw material for forming the piezoelectric ceramic layer 7 and the firing conditions are adjusted and obtained from the measurement result of the crystal grain size by the intercept method. In the same manner as in Example 1, except that the piezoelectric ceramic layer 7 having an average crystal grain size of the piezoelectric ceramic having a value shown in Table 1 was used, A kind of piezoelectric actuator 1 was produced, and an ink jet printer head 2 was produced. The ratio A ₂ / A ₁ between the area A _{1 in the} plane direction of the piezoelectric deformation region 8 and the area A _{2 in the} plane direction of the individual electrode layer 10 was adjusted to be 0.9.

The coercive electric field strength Ec of the piezoelectric ceramic layer 7 of the piezoelectric actuator 1 was 1.41 kV / cm. Further, while maintaining the temperature of the piezoelectric actuator 1 at room temperature (+5 to + 35 ° C.), the piezoelectric ceramic layer 7 has ± 1.83 kV / cm, a frequency of 0.1. Table 1 shows the ratio of the piezoelectric displacement component ε ^P31 to the total amount of displacement ε when a driving voltage pulse of 01 Hz in which forward and reverse voltages are alternately applied is applied to bend and deform in the thickness direction. It became the value shown.

  A driving voltage in which forward and reverse voltages of ± 1.83 kV / cm and a frequency of 1 kHz are alternately switched in the piezoelectric ceramic layer 7 while maintaining the temperature of the piezoelectric actuator 1 at room temperature (+5 to + 35 ° C.). The piezoelectric actuator when driven by applying a drive voltage pulse having the same voltage and the same frequency while maintaining the same room temperature (+5 to + 35 ° C.) after being applied and driven for 1 billion cycles. The displacement amount of the center position in the surface direction of one piezoelectric deformation region 8 was measured. The relationship between the change rate (%) of the amount of displacement from the initial value measured under the same conditions before driving for 1 billion cycles and the average crystal grain size (μm) of the piezoelectric ceramic forming the piezoelectric ceramic layer 7. Is plotted in FIG.

  From Table 1 and FIG. 4, by setting the average crystal grain size of the piezoelectric ceramic forming the piezoelectric ceramic layer 7 to 2.5 μm or less, the displacement change rate after 1 billion cycles of the piezoelectric actuator 1 is −10.0%. It was confirmed that it was suppressed within.

Lee inkjet purine meter size EBEP head of the present invention, is an enlarged cross-sectional view showing an example of the embodiment. 2 is a graph showing a relationship between a displacement amount (nm) of a piezoelectric deformation region and an electric field strength (kV / cm) in the ink jet printer head of FIG. It is a graph which shows the relationship between the change rate (%) of the displacement amount of a piezoelectric deformation area | region in the inkjet printer head produced in Example 1 of this invention, and a frequency. It is a graph which shows the relationship between the change rate (%) of the displacement amount of a piezoelectric deformation area | region, and temperature in the inkjet printer head produced in Example 1 of this invention. The graph which shows the relationship between the change rate (%) of the displacement amount of a piezoelectric deformation area | region, and the average crystal grain diameter of the piezoelectric ceramic which forms a piezoelectric ceramic layer in the ink brush printer head produced in Example 2 of this invention. It is.

Explanation of symbols

1 Piezoelectric actuator
2 Inkjet printer head 7 Piezoelectric ceramic layer 8 Piezoelectric deformation region 9 Restraint region 10 Individual electrode layer 11 Common electrode layer 12 Diaphragm

Claims (2)

An inkjet printer head comprising a plurality of pressurizing chambers, a substrate including a plurality of nozzles respectively communicating with the plurality of pressurizing chambers, and a plate-shaped piezoelectric actuator laminated on the substrate,
The piezoelectric actuator includes a diaphragm having a size covering the plurality of pressurizing chambers, a common electrode, and a piezoelectric ceramic layer, and a plurality of individual electrode layers provided corresponding to the plurality of pressurizing chambers, respectively. Including
The area of the individual electrode layer is 0.8 times or more and less than 1.0 times the area of the pressurizing chamber,
The piezoelectric ceramic layer has an average crystal grain size of not less than 0.5 μm and not more than 2.5 μm, and the piezoelectric ceramic layer is sandwiched between the common electrode layer and the individual electrode layer and has a voltage in the thickness direction. by but is applied to stretch in the plane direction orthogonal to the thickness direction, and deformed in the thickness direction, and the piezoelectric ceramic layer, more than 1.2 times the coercive field strength Ec of the piezoelectric ceramic layer Formula (1) when applying voltage to bend and deform in the thickness direction:
ε = ε ^P31 + ε ^d31 (1)
(In the equation, ε ^P31 represents the piezoelectric displacement component of the displacement amount, and ε ^d31 represents the 90 ° rotational displacement component of the displacement amount.)
In the total amount epsilon displacement represented, the ratio of the piezoelectric displacement component epsilon ^P31-jet printer head, characterized in that it is 0.6 or more. 2. The ink jet printer head according to claim 1 , wherein the piezoelectric ceramic layer is made of a piezoelectric ceramic mainly composed of lead zirconate titanate .

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