JP2006049717A - Manufacturing methods of piezoelectric element and piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide manufacturing methods of a piezoelectric element and a piezoelectric actuator having the same piezoelectric element wherein the inner electrodes of the piezoelectric element overlap with each other via its piezoelectric material layers, the overlapping portions are gathered in its one end surface, and further, its warpage caused by the overlapping in the case of its heat treatment process can be eliminated by this manufacturing method. <P>SOLUTION: The manufacturing method of the piezoelectric element has the process wherein after a heat treatment, there is applied to the portion of first and second inner electrodes overlapping with each other a lower voltage than the voltage for applying to the portion in the case of a polarization processing to be performed thereafter. The manufacturing method of the piezoelectric actuator has the process wherein this piezoelectric element is joined to a fastening substrate and is subjected to the polarization processing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a piezoelectric element suitable for a piezoelectric actuator used in, for example, a head portion of an ink jet printer, and more specifically, a mother ceramic sintered body and a ceramic sintered body of each piezoelectric element unit. The present invention relates to a method for manufacturing a piezoelectric element including a step of performing polarization processing and a method for manufacturing a piezoelectric actuator including the piezoelectric element.

  Piezoelectric actuators are widely used to drive and control head portions of ink jet printers and the like. This type of piezoelectric actuator is configured using a stacked piezoelectric element in which a plurality of internal electrodes are stacked via a piezoelectric layer. The stacked piezoelectric element expands and contracts when a voltage is applied. By using this expansion and contraction to drive a driven member that is in contact with or connected to the piezoelectric element, the amount of ink ejected is controlled.

  A piezoelectric displacement element having such a laminated piezoelectric element is described in Patent Document 1 below. FIG. 11 is a perspective view showing a method for manufacturing a piezoelectric displacement element disclosed in Patent Document 1. As shown in FIG.

  The piezoelectric displacement element disclosed in Patent Document 1 is manufactured as follows.

  First, a thin piezoelectric material is applied in a rectangular shape on the surface plate 201 to form a piezoelectric layer 202a (FIG. 11A). On the molded piezoelectric layer 202a, a conductive material is applied so as to reach the second end 203b while leaving a portion having a predetermined width from the first end 203a, thereby forming the first internal electrode 204a. (FIG. 11 (b)). A piezoelectric material is further applied so as to cover a portion where the first internal electrode 204a in the vicinity of the first end portion 203a is not formed and a portion where the first internal electrode 204a is formed, and a piezoelectric layer 202b is formed (FIG. 11C). Next, a conductive material is further applied so as to have a portion having a predetermined width from the second end portion 203b so as to have a portion overlapping with the first internal electrode 204a, and to reach the first end portion 203a. A second internal electrode 204b is formed (FIG. 11D). Further, a piezoelectric material is applied. By repeating these steps according to the number of layers to be formed, a rectangular parallelepiped laminated body 205 is obtained (FIG. 11E).

  Next, the laminated body 205 is dried and fired at 1000 to 1200 ° C. for 1 hour to obtain a mother sintered body 206. A conductive material is applied to the first end surface 203a and the second end surface 203b of the mother sintered body 206 to form conductive layers 207a and 207b (FIG. 11 (f)).

  The mother sintered body 206 is formed so as not to reach the first end face 203a and is formed so as not to reach the first inner electrode 204a drawn to the second end face 203b and the second end face 203b. And a second internal electrode 204b led out to the first end face 203a. A portion where the first internal electrode 204 a and the second internal electrode 204 b overlap in the vertical thickness direction is the active portion 208. Here, the active part 208 is offset toward the first end face 203a.

  The mother sintered body 206 on which the conductive layers 207a and 207b are formed is cut into the size of each piezoelectric displacement element. When the piezoelectric displacement element obtained by cutting is used, the side surface of the inactive portion 209 located on the second end surface 203a side is fixed via the adhesive layer. The first end face 203a side is connected to a base that is positioned with respect to the driven member.

  In the piezoelectric displacement element obtained as described above, when a voltage is applied in use, the expansion and contraction of the piezoelectric element is not hindered, so that the amount of ink ejected can be reliably controlled.

  On the other hand, Patent Document 2 below discloses a method for manufacturing a piezoelectric element that is unlikely to crack when driven by applying a voltage.

  When driving by applying a voltage to the laminated piezoelectric body, for example, when driven under a condition where a high load or a high voltage is applied, cracks may occur in the piezoelectric body. One of the causes is that the piezoelectric element is warped.

In Patent Document 2, in order to eliminate this warp, the piezoelectric plate is curved in advance, and the piezoelectric element is flattened by applying electrodes during the polarization process. That is, after electrodes are formed on one surface and the other surface of the piezoelectric plate, respectively, polarization is performed by applying a voltage so that one surface side is a positive electrode and the other surface side is a negative electrode. A flat piezoelectric element is obtained by canceling the deformation after the polarization treatment with the deformation of the piezoelectric plate before the treatment.
Japanese Patent No. 3347346 JP-A-5-167126

  However, usually, piezoelectric elements are produced in large quantities at the same time, and a large number of mother piezoelectric elements are taken at a time. When manufacturing such a large mother piezoelectric element, the mother sintered body 206 is fixed to an adhesive sheet or the like, and is cut into sintered bodies of individual piezoelectric element units. Therefore, the adhesive component of the adhesive sheet tends to adhere to the cut sintered body. Therefore, it was necessary to heat treat the sintered body in order to remove the adhered adhesive component.

  In this heat treatment step, in the piezoelectric element in which the electrode overlapping portion described in Patent Document 1 is brought close to one end face, the piezoelectric element may be deformed into a curved shape. That is, the amount of shrinkage is large at the portion where the internal electrodes are dense, and the amount of shrinkage is small at the portion where the internal electrodes are not dense, which may result in deformation.

  When a piezoelectric element deformed into a curved shape is driven by applying a voltage, for example, when driven under a condition where a high load or a high voltage is applied, cracks are likely to occur in the piezoelectric body.

  Therefore, in order to prevent the occurrence of cracks, it has been necessary to eliminate the curved shape and form a flat piezoelectric element.

  On the other hand, in the method for manufacturing a piezoelectric element described in Patent Document 2, warpage in the electrode stacking direction in which electrodes are formed is reduced. However, it is impossible to eliminate the warp due to the difference in the amount of contraction that occurs in the piezoelectric element in which the electrode overlapping portion described in Patent Document 1 is arranged close to one end face.

  In view of the state of the prior art described above, the present invention is a piezoelectric element in which an electrode overlapping portion through an inner electrode piezoelectric layer is brought close to one end face, and the piezoelectric element capable of eliminating the warp generated during the heat treatment process. And a method of manufacturing a piezoelectric actuator including the piezoelectric element.

  The piezoelectric element manufacturing method according to the present invention includes a piezoelectric body having an upper surface, a lower surface, and opposing first and second end surfaces, and a piezoelectric body disposed in the vertical thickness direction via a piezoelectric layer. A plurality of internal electrodes, wherein the plurality of internal electrodes are formed so as not to reach the second end face and are drawn out to the first end face; and on the first end face And a second internal electrode that is drawn out to the second end face, and the first internal electrode and the second internal electrode are vertically moved through the piezoelectric layer. The present invention relates to a method of manufacturing a piezoelectric element having a portion overlapping in the thickness direction and a portion overlapping in the vertical thickness direction of the first and second internal electrodes being offset from the first end surface or the second end surface. Process for obtaining ceramic green sheet and ceramic green sheet Forming an internal electrode on the substrate, laminating a plurality of ceramic green sheets on which the internal electrode is formed to obtain a laminate, firing the laminate to obtain a mother sintered body, mother Fixing the sintered body on the pressure-sensitive adhesive sheet and cutting it into individual piezoelectric element unit sintered bodies, and heating the sintered body to remove the pressure-sensitive adhesive component of the pressure-sensitive adhesive sheet And a step of applying a voltage lower than a voltage applied in a polarization process performed in a later step to a portion where the first and second internal electrodes overlap after the heat treatment step.

  On the specific situation with the piezoelectric element which concerns on this invention, in the process of applying a voltage, the value of the voltage to apply is 0.2 kV / mm or more.

  In another specific aspect of the piezoelectric element according to the present invention, the voltage application time is 1 to 120 seconds in the step of applying a voltage.

  The method for manufacturing a piezoelectric actuator according to the present invention further includes a step of bonding the piezoelectric element manufactured by the manufacturing method according to the present invention and a fixed substrate, and a step of polarizing the piezoelectric element bonded to the fixed substrate. I have.

  Since the piezoelectric element manufacturing method according to the present invention includes a heat treatment step of heating the sintered body cut into individual piezoelectric element units, the adhesive component of the attached adhesive sheet can be removed. Even if the heat treatment process causes a warp in the plane direction due to the contraction of the internal electrode of the piezoelectric element, the voltage applied to the overlapping portion of the first and second internal electrodes is higher than the voltage applied during the polarization process performed in the subsequent process. Since it further includes a step of applying a low voltage, warping can be remarkably reduced.

  In the step of applying a voltage according to the present invention, when the value of the applied voltage is 0.2 kV / mm or more, the warp of the piezoelectric element can be further reduced.

  In the step of applying a voltage according to the present invention, when the voltage application time is 1 to 120 seconds, the warpage of the piezoelectric element can be further reduced.

  The method for manufacturing a piezoelectric actuator according to the present invention further includes a step of bonding the piezoelectric element and the fixed substrate after applying a voltage to return the warp, and a step of polarizing the piezoelectric element bonded to the fixed substrate. Therefore, the voltage applied during the polarization process can be lowered. Therefore, the occurrence of cracks and the like can be effectively suppressed.

  When the piezoelectric actuator according to the present invention is used in a head portion of an ink jet printer or the like, cracks hardly occur in the piezoelectric body when driven by applying a voltage. Therefore, the head portion can be driven and controlled stably.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  A method for manufacturing a piezoelectric element according to an embodiment of the present invention will be described.

  A mother first ceramic green sheet 1 and a mother second ceramic green sheet 11 shown in schematic plan views in FIGS. 1A and 1B are prepared. The mother ceramic green sheets 1 and 11 are obtained by forming a sheet using a slurry containing piezoelectric ceramics such as lead zirconate titanate ceramics or lead titanate ceramics. Next, a conductive paste is printed on the ceramic green sheets 1 and 11 to form internal electrode patterns 2 and 12, respectively.

  Next, a plurality of first ceramic green sheets 1 and second ceramic green sheets 11 are alternately stacked. Further, a plain ceramic green sheet is laminated on the top to obtain a mother laminate.

  The mother laminate is pressed in the thickness direction and then fired. In this manner, a rectangular parallelepiped mother sintered body 31 shown in the perspective view and the front view of FIGS. 2A and 2B is obtained. In the mother sintered body 31, a plurality of internal electrode patterns 2, 12 are formed so as to overlap with each other via the piezoelectric layer 32.

  Next, as shown in a partially cutaway perspective view in FIG. 3A, the mother sintered body 31 is adhered and fixed on the adhesive sheet 35. After fixing, the mother sintered body 31 is cut into a plurality of ceramic sintered bodies 41 in units of individual piezoelectric elements using a dicing saw or the like.

  One ceramic sintered body 41 is shown in a perspective view in FIG. 3 (b) with the orientation changed from that in FIG. 3 (a). In FIG. 3B, the upper surface of the ceramic sintered body 41 is the first end surface 42a, the lower surface is the second end surface 42b, the front surface is the upper surface 43a, and the rear surface is the lower surface 43b. As shown.

  In addition, about the internal electrode pattern in the right side surface of the ceramic sintered body 41 shown in FIGS. 3B and 4A described below and the piezoelectric element 61 shown in FIGS. It is the same as the internal electrode pattern on the front side surface of the ceramic sintered body of each piezoelectric element unit shown in FIG. 3A, but by referring to FIG. 3A, the internal electrode pattern on the right side surface Is omitted.

  When the ceramic sintered body 41 is peeled from the adhesive sheet 35 after dicing, the adhesive component of the adhesive sheet 35 adheres to the lower surface 43b.

  The ceramic sintered body 41 has a rectangular parallelepiped shape. In the ceramic sintered body 41, a plurality of internal electrodes are formed so as to overlap in the thickness direction with the sintered body layer interposed therebetween. The plurality of internal electrodes are formed so as not to reach the second end surface 42b and reach the first end surface 42a and the plurality of first internal electrodes 44a drawn to the first end surface 42a. A plurality of second internal electrodes 44b which are formed so as not to extend and are drawn to the second end face 42b.

  The portion where the first internal electrode 44a and the second internal electrode 44b overlap in the thickness direction, which is the direction connecting the upper surface 43a and the lower surface 43b, is an active portion 45 to which a voltage is applied during driving. In the present embodiment, the active portion 45 is offset toward the first end face 42a.

  The feature of this embodiment is that the active portion, which is a portion overlapping in the thickness direction between the first internal electrode and the second internal electrode, is shifted to one end surface side of either the first end surface or the second end surface. There is in being.

  Next, in order to remove the adhesive component adhering to the lower surface 43b of the ceramic sintered body 41, the ceramic sintered body 41 is heat-treated. By this heat treatment step, a deformed curved ceramic sintered body 41 shown in a perspective view in FIG. That is, in the ceramic baking body portion on the first end face 42a side, the internal electrodes are denser than in the ceramic sintered body portion on the second end face 42b side. It becomes larger on the side closer to the surface and is deformed into a concave shape. On the other hand, in the ceramic sintered body portion on the second end face 42b side, since the internal electrodes are not denser than the ceramic sintered body portion on the first end face 42a side, the shrinkage amount of the internal electrode due to heat treatment is small, Deformed into a convex shape. The ceramic sintered body 41 has a rectangular parallelepiped shape as described above, and the horizontal side 43a2 is longer than the vertical side 42a1 on the upper surface 43a of FIG. The mother sintered body 31 is cut. The above-described deformation is more prominent when the horizontal side is longer than the longer side. Therefore, the present invention is more effective as it is applied to a long ceramic sintered body.

  FIG. 4B shows a development view of the ceramic sintered body 41. As described above, the ceramic sintered body 41 has a curved shape in which the first end surface 42a having the active portion 45 is deformed into a convex shape. Note that the upper surface 43a and the lower surface 43b are flat surfaces, and no warpage occurs in the stacking direction of the internal electrodes.

  Next, external electrodes are formed on the ceramic sintered body 41 to obtain a piezoelectric element. That is, as shown in FIGS. 5A and 5B in perspective and front views, the piezoelectric element 61 covers the first end surface 42a of the ceramic sintered body 41 and reaches a part of the upper surface 43a and the lower surface 43b. Thus, the first external electrode 62a is formed. A second external electrode 62b is formed so as to cover the second end face 42b and reach a part of the upper surface 43a and the lower surface 43b.

  As a material constituting the first and second external electrodes, an appropriate metal or alloy such as Cu or Ag can be used. The first and second external electrodes can be formed by a thin film forming method such as sputtering or vapor deposition, or an appropriate method such as application / curing or baking of a conductive paste.

  Next, in the piezoelectric element 61, a positive electrode is connected to one of the first and second external electrodes 62a and 62b, and a negative electrode is connected to the other, and a voltage is applied. This voltage is set to a voltage lower than the voltage applied during the polarization process performed in a later step. When a voltage is applied to the piezoelectric element 61, the polarization direction in the vicinity of the active portion 45 is directed to a certain direction and contracts. As the portion on the first end surface 42a side deformed into a concave shape contracts, the portion between the portion on the first end surface 42a side deformed in a concave shape and the portion on the second end surface 42b side deformed into a convex shape. Warpage is reduced and flattened. Therefore, a rectangular piezoelectric element 61 having a small warp as shown in the perspective view of FIG. 6A can be obtained.

  Although the value of the said voltage will not be specifically limited if it is lower than the voltage applied at the time of the polarization process performed at a next process, 0.2-3.0 kV / mm is preferable. When the applied voltage value is lower than 0.2 kV / mm, the effect of reducing the warpage of the piezoelectric element may not be sufficient. When the applied voltage value is higher than 3.0 kV / mm, the piezoelectric element The warp of the element is small and the effect may be too high.

The voltage application time is not particularly limited, but is preferably 1 to 120 seconds. If the voltage application time is shorter than 1 second, the effect of reducing the warpage of the piezoelectric element may not be sufficient, and if the voltage application time is longer than 120 seconds, the effect of reducing the warpage of the piezoelectric element is saturated. It may become a state.
In the above embodiment, the first and second external electrodes 62a and 62b are formed and the voltage is applied. However, another method may be used as long as a voltage is applied to the active portion 45. For example, a voltage may be applied to the lead portions of the opposing first and second internal electrodes 44a and 43b.

  A method for manufacturing a piezoelectric actuator using the rectangular piezoelectric element 61 obtained as described above will be described.

  As shown in FIG. 7, the piezoelectric element 61 is fixed to the fixed substrate 81 using an adhesive. The piezoelectric element 61 includes a first inactive portion 82a between the active portion 45 and the first end surface 42a, and a second inactive portion 82b between the active portion 45 and the second end surface 42b. . When the piezoelectric element 61 is fixed, the lower surface 43b of the second inactive portion 82b may be bonded to the fixed substrate 81.

  The upper surface 43a of the second inactive portion 82b portion, the upper surface 43a of the first inactive portion 82a portion, or the lower surface 43b of the first inactive portion 82a portion may be bonded to the fixing device 81. In other words, any one of the first end surface 42a and the second end surface 42b may be formed to be a driving surface of the piezoelectric actuator.

  As the adhesive, an appropriate resin adhesive such as an epoxy adhesive or a bonding agent made of metal can be used.

  In the present invention, when the piezoelectric element 61 is used to drive, for example, a head of an ink jet printer, a plurality of slits 83 are formed in the piezoelectric element 61. The slit 83 extends from the first end face 42 a of the piezoelectric element 61 toward the second end face 42 b and passes through the lower face 43 b from the upper face 43 a of the piezoelectric element 61. The slit 83 is extended so as to divide the first external electrode 62 a disposed on both sides of the slit 83. Therefore, the piezoelectric part between the adjacent slits 83 constitutes one piezoelectric actuator part. Therefore, in the structure shown in FIG. 7, a plurality of piezoelectric actuator portions are formed by forming a plurality of slits 83.

  Next, the lead wire 92 connected to the positive electrode is placed on the piezoelectric element 61 in which the plurality of slits 83 are formed, the second external electrode 62b is connected to the negative electrode, and polarization is applied by applying a voltage. Perform processing.

  In this case, since the piezoelectric element 61 is previously applied with a voltage to eliminate the warp and the degree of orientation is increased, it is not necessary to apply a high voltage during polarization. Since the voltage applied during the polarization process is low, the occurrence of cracks and the like can be effectively suppressed.

  Although the voltage application conditions during the polarization treatment are not particularly limited, for example, a voltage of 3.0 kV / mm may be applied for 60 seconds. In this polarization process, since the piezoelectric element 61 is fixed to the fixed substrate 81, the contraction is prevented and the deformation hardly occurs.

  Hereinafter, the present invention will be described in more detail by giving specific experimental examples of the method for manufacturing a piezoelectric element according to the present invention.

  As shown in the perspective view of FIG. 8, the first and second external electrodes 62a and 62b of the piezoelectric element 61 having a curved shape obtained according to the above-described manufacturing method are connected to the first external electrode 62a and the positive electrode 63a. The negative electrode 63b was connected to the second external electrode 62b, and a voltage was applied. The application conditions were such that the applied voltage value was 0.6 kV / mm, and the voltage application time was 10, 20, 30, 90 seconds.

  In addition, as the piezoelectric element 61, when not curved, a piezoelectric element having a size of 30 × 3 × thickness 0.6 mm was manufactured. The number of internal electrodes stacked was 16.

  The degree of warpage before and after voltage application, that is, the arch amount was measured with a surface roughness meter. As shown in FIG. 9, in the second end face 42b portion, the maximum value L of the surface roughness when the stylus of the surface roughness meter is run is defined as the arch amount. When the second end face 42b is deformed into a convex shape, the arch amount is a positive value, and when it is deformed into a concave shape, the arch amount is a negative value.

  The relationship between the voltage application time and the arch amount is shown in FIG.

  Before the voltage application, the average arch amount was 3.0 μm, but after the voltage application, the arch amount was small under any condition. Further, the longer the voltage application time, the greater the arch amount after voltage application. When the applied voltage value was 0.6 kV / mm and the voltage application time was 10 seconds, the arch amount was closest to 0 μm, and the rectangular piezoelectric element 61 with extremely small warpage could be obtained.

  Next, in the same manner as in the above embodiment, the voltage applied is changed in the range of 0 to 4.0 kV / mm, the voltage application time is in the range of 1 to 180 seconds, and the arch amount before and after the voltage application is measured. did.

  Table 1 shows the relationship between the voltage application condition and the arch deformation amount (μm), with the distance changed from the arch amount before voltage application as the arch deformation amount.

  The application condition for flattening the curved piezoelectric element 61 varies depending on the arch amount of the piezoelectric element 61 before voltage application. From the results shown in Table 1, the warping depends on the voltage value to be applied and the voltage application time. It was found that can be controlled in the range of 0 to 20 μm.

  By the way, the arch amount of the curved piezoelectric element 61 before voltage application is about 15 μm at the maximum. Therefore, by appropriately setting the application conditions within the range of the applied voltage value of 0 to 4.0 kV / mm and the voltage application time of 1 to 180 seconds, depending on the arch amount of the curved piezoelectric element 61 before voltage application. It was found that a rectangular piezoelectric element 61 can be obtained.

(A) And (b) is a schematic top view which shows the 1st, 2nd ceramic green sheet of the mother used for obtaining the piezoelectric element of this embodiment. (A) And (b) is the perspective view and front view which show the sintered compact of the rectangular parallelepiped mother used for obtaining the piezoelectric element of this embodiment. (A) is a partial notch perspective view which shows the sintered compact of the rectangular parallelepiped mother fixed on the adhesive sheet. (B) is a perspective view showing a ceramic sintered body obtained by cutting a mother sintered body. (A) And (b) is a perspective view and an expanded view which show the curved ceramic sintered compact used for obtaining the piezoelectric element of this embodiment. (A) And (b) is the perspective view and front view which show the piezoelectric element of the curved shape of this embodiment. The perspective view which shows the rectangular-shaped piezoelectric element of this embodiment. The perspective view which shows the rectangular-shaped piezoelectric element fixed to the fixed board | substrate used for obtaining the piezoelectric actuator of this embodiment. The typical front view for demonstrating the process of applying a voltage to a piezoelectric element of curve shape. The typical perspective view for demonstrating the measurement range of the arch amount of a piezoelectric element. The figure which shows the relationship between the voltage application time in the process of applying the voltage of this embodiment, and the amount of arches. (A)-(f) is a perspective view which shows an example of the manufacturing method of the conventional piezoelectric element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st ceramic green sheet 2 ... Internal electrode pattern 11 ... 2nd ceramic green sheet 12 ... Internal electrode pattern 31 ... Sintered body 32 ... Piezoelectric layer 35 ... Adhesive sheet 41 ... Ceramic sintered body 42a ... 1st end surface 42b ... 2nd end surface 43a ... Upper surface 43b ... Lower surface 44a ... 1st internal electrode 44b ... 2nd internal electrode 45 ... Active part 61 ... Piezoelectric element 62a ... 1st external electrode 62b ... 2nd External electrode 81 ... fixed substrate 82a ... first inactive part 82b ... second inactive part 83 ... slit

Claims (4)

A piezoelectric body having an upper surface, a lower surface, and first and second end surfaces facing each other;
A plurality of internal electrodes arranged in the vertical thickness direction through the piezoelectric layer in the piezoelectric body,
The plurality of internal electrodes are formed so as not to reach the second end face, and do not reach the first end face and the first internal electrode drawn out to the first end face. And has a second internal electrode drawn out to the second end face,
The first internal electrode and the second internal electrode have a portion that overlaps in the vertical thickness direction through the piezoelectric layer,
A method of manufacturing a piezoelectric element in which the overlapping portions of the first and second internal electrodes in the vertical thickness direction are offset from the first end surface or the second end surface,
Obtaining a plurality of ceramic green sheets;
Forming an internal electrode on the ceramic green sheet;
Laminating a plurality of ceramic green sheets on which the internal electrodes are formed to obtain a laminate; and
Firing the laminate to obtain a mother sintered body;
Fixing the mother sintered body on an adhesive sheet and cutting the sintered body into individual piezoelectric element units;
A heat treatment step of heating the sintered body and removing the adhesive component of the adhesive sheet attached thereto;
And a step of applying a voltage lower than a voltage applied in a polarization process performed in a subsequent process to an overlapping portion of the first and second internal electrodes after the heat treatment process. Device manufacturing method.   The method for manufacturing a piezoelectric element according to claim 1, wherein in the step of applying the voltage, a value of the applied voltage is 0.2 kV / mm or more.   3. The method of manufacturing a piezoelectric element according to claim 1, wherein in the step of applying the voltage, a voltage application time is 1 to 120 seconds. After manufacturing a piezoelectric element by the method for manufacturing a piezoelectric element according to any one of claims 1 to 3,
Bonding the piezoelectric element and the fixed substrate;
And a step of polarizing the piezoelectric element bonded to the fixed substrate.

Images