JP5023515B2 - A method for manufacturing a piezoelectric element. - Google Patents

Description

  The present invention relates to a method of manufacturing a piezoelectric element having a piezoelectric layer and a displacement transmission layer for transmitting displacement of the piezoelectric layer.

  For example, as a piezoelectric component such as a piezoelectric buzzer, a sounding body, a piezoelectric sensor, and a piezoelectric actuator, a laminated piezoelectric application product in which piezoelectric layers and internal electrode layers are alternately stacked is known (for example, see Patent Document 1). . Such a laminated piezoelectric application product is small in size, and has an advantage that a large mechanical and physical displacement can be obtained with a small voltage. Since these advantages are adapted to industrial demands, their development has been progressing rapidly in recent years.

As the most common piezoelectric actuator, ceramic powder mainly composed of lead zirconate titanate (PZT) is made into a sheet, and a paste composed of Ag and Pd is printed on the obtained sheet, and then the paste is printed. The green sheet is produced by alternately laminating the sheet and the sheet on which the paste is not printed, and the terminal electrode is applied after the green layer is fired.
JP 2001-260349 A

  As a method of using a piezoelectric actuator, it is common to operate a target by transmitting a minute displacement generated by ON / OFF of a voltage applied to the piezoelectric actuator to the target. When the object is solid, it is only necessary to attach the object to the tip of the actuator and transmit the displacement. However, if the object is a liquid and the liquid directly touches the displacement transmission surface of the piezoelectric actuator, the liquid will impregnate the piezoelectric actuator from the displacement transmission surface, causing deterioration of the piezoelectric actuator characteristics such as poor insulation. There is.

  Accordingly, an object of the present invention is to provide a method for manufacturing a piezoelectric element capable of suppressing deterioration of characteristics when a displacement of a piezoelectric layer is transmitted to a liquid.

  As a result of extensive studies, the inventors have impregnated the liquid into the piezoelectric element and cause deterioration of the characteristics of the element. It has been found that there is a so-called electro-osmotic phenomenon in which liquid is attracted. In order to prevent this, for example, it is necessary to provide some partition wall such as a thin plate between the displacement transmission surface of the piezoelectric element and the liquid. However, when such a partition wall is provided, the piezoelectric element can be prevented from being destroyed, but there is a problem that a displacement transmission loss is generated by the amount of the partition wall, and the amount of displacement that can be transmitted to the liquid is reduced. Moreover, in order to compensate for the decrease in transmission displacement due to the partition walls, it is necessary to increase the size of the piezoelectric element or increase the number of layers to be stacked. There are further problems, such as higher prices.

  As a result of analyzing the electroosmosis phenomenon of the liquid, the present inventors have found that the liquid penetrates (enters) into the piezoelectric element through the gaps between the particles of the displacement transmission layer. Therefore, the present inventors have conducted further studies. As a result, if the silicon oxide is diffused into the displacement transmission layer and the silicon oxide fills the gaps between the particles of the displacement transmission layer, the electroosmosis phenomenon can be prevented. I found. The present invention has been made based on such new findings.

  That is, the present invention is a method of manufacturing a piezoelectric element having a piezoelectric layer and a displacement transmission layer for transmitting the displacement of the piezoelectric layer, the piezoelectric ceramic green sheet as a precursor of the piezoelectric layer, a displacement A green sheet preparing step for preparing a displacement transmitting ceramic green sheet as a precursor of the transmission layer, and a green laminate forming a green laminate in which the piezoelectric ceramic green sheet and the displacement transmitting ceramic green sheet are laminated And forming a silicon oxide layer made of silicon oxide on the displacement-transmitting ceramic green sheet.

  Thus, the green laminate formed by the method for manufacturing a piezoelectric element of the present invention includes a silicon oxide layer, a piezoelectric layer, and a displacement transmission layer. In this case, for example, in the baking process, the silicon oxide forming the silicon oxide layer diffuses into the displacement transmission layer. The silicon oxide soaked in the displacement transmission layer fills the gaps between the particles of the displacement transmission layer. As a result, when the displacement of the piezoelectric layer is transmitted to the liquid object via the displacement transmission layer, the electroosmosis phenomenon of the liquid in contact with the displacement transmission layer is prevented, so that the deterioration of characteristics such as poor insulation of the piezoelectric element is caused. Can be deterred.

  At this time, in the green laminate forming step, the displacement transmitting ceramic green sheet on which the silicon oxide layer is formed by the silicon oxide layer forming step is laminated so that the silicon oxide layer is on the ceramic green sheet side for the piezoelectric body. Thus, a green laminate may be formed. In this case, in the green laminate forming step, it is preferable to further laminate a displacement transmitting ceramic green sheet between the piezoelectric ceramic green sheet and the silicon oxide layer to form a green laminate.

  Also, in the green laminate forming step, the displacement transmitting ceramic green sheet on which the silicon oxide layer is formed by the silicon oxide layer forming step is arranged so that the displacement transmitting ceramic green sheet is on the piezoelectric ceramic green sheet side. A green laminate may be formed by laminating.

  In the green laminate forming step, after the ceramic green sheet for piezoelectric body and the ceramic green sheet for displacement transmission are laminated, the silicon oxide layer is formed on the ceramic green sheet for displacement transmission by the step of forming the silicon oxide layer. Thus, a green laminate may be formed.

  In these cases, since silicon oxide diffuses into the displacement transmission layer, a gradient of silicon oxide concentration is formed in the displacement transmission layer. For this reason, the silicon oxide layer side of the displacement transmission layer has a high concentration of silicon oxide, so that the electroosmosis phenomenon is reliably prevented. On the other hand, the silicon oxide layer has a low concentration on the side opposite to the silicon oxide layer side of the displacement transmission layer, and hardly affects the piezoelectric characteristics of the piezoelectric element. That is, the electroosmotic phenomenon can be reliably prevented without affecting the original piezoelectric characteristics of the piezoelectric element.

  According to the present invention, when the displacement of the piezoelectric layer is transmitted to the liquid, the electroosmosis phenomenon of the charged liquid is prevented, so that it is possible to suppress deterioration of characteristics such as insulation failure of the piezoelectric element. As a result, there is no need to provide a partition wall or the like separate from the element between the displacement transmission layer of the piezoelectric element and the liquid, so that the element can be miniaturized and the manufacturing cost can be reduced.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a preferred embodiment of a method for producing a piezoelectric element according to the invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted.

[First Embodiment]
Hereinafter, the manufacturing method of the piezoelectric element 2 according to the first embodiment of the present invention will be described with reference to the drawings. First, FIG. 1 is a perspective view showing a piezoelectric actuator 1 including a piezoelectric element 2 according to the manufacturing method according to the first embodiment. FIG. 2 is a partial cross-sectional view of the piezoelectric actuator 1 shown in FIG. A piezoelectric actuator 1 shown in each figure is a liquid control piezoelectric device used in, for example, a micropump unit.

  As shown in FIGS. 1 and 2, the piezoelectric actuator 1 includes a stacked piezoelectric element 2 and a liquid circulation part 3 joined to the bottom surface of the piezoelectric element 2. The piezoelectric element 2 has a rectangular parallelepiped green laminated body 4, and the green laminated body 4 includes an active region layer 5 and a displacement transmission layer 6 disposed on the liquid circulation part 3 side of the active region layer 5. Yes.

  The active region layer 5 is disposed so as to face the piezoelectric layer 7 with the piezoelectric layer 7 interposed therebetween, and a plurality of internal individual electrodes 8 and internal common electrodes for operating the piezoelectric layer 7 to expand and contract (displace). 9 over a plurality of layers. The individual internal electrode layers 8 and the internal common electrodes 9 are alternately stacked via the piezoelectric layers 7. In the piezoelectric layer 7, a plurality of portions sandwiched between each internal individual electrode 8 and the internal common electrode 9 actually expand and contract when a voltage is applied between each internal individual electrode 8 and the internal common electrode 9. The piezoelectric active portion 7a is configured.

  On the upper surface of the green laminate 4, a plurality of individual terminal electrodes 10 electrically connected to the plurality of internal individual electrodes 8 of each layer, and a common terminal electrode 11 electrically connected to the internal common electrode 9 of each layer. And are provided.

  The piezoelectric layer 7 is made of, for example, a piezoelectric ceramic material mainly composed of PZT (lead zirconate titanate). The internal individual electrode 8 and the internal common electrode 9 are made of, for example, an Ag—Pd alloy, and the individual terminal electrode 10 and the common terminal electrode 11 are made of, for example, Ag, Au, or Cu. The thickness of the piezoelectric layer 7 is, for example, about 30 μm at the time after firing described later. The thickness of the internal individual electrode 8 and the internal common electrode 9 is, for example, about 0.2 to 5.0 μm.

  The displacement transmission layer 6 laminated on the lower side with respect to the active region layer 5 is a layer that transmits the displacement of the piezoelectric active portion 7 a of the piezoelectric layer 7 to the liquid flowing in the liquid flowing portion 3. The displacement transmission layer 6 is preferably formed of the same material as the piezoelectric layer 7. As a result, as will be described later, since the displacement transmission layer 6 can be formed in the same process as the piezoelectric layer 7, the green laminate 4 can be easily manufactured. The displacement transmission layer 6 is composed of two layers (two displacement transmission layers 60), and the thickness of each of the two layers is, for example, about 15 μm at the time after firing described later.

The displacement transmission layer 6 is impregnated with silicon oxide (for example, SiO ₂ ). This silicon oxide is transferred from the silicon oxide paste (silicon oxide layer) applied between the two layers constituting the displacement transmitting layer 6 by a procedure (piezoelectric element manufacturing method) for manufacturing the piezoelectric actuator 1 described later. It has been diffused into the layer 6. FIG. 2 illustrates the concentration of silicon oxide in the displacement transmission layer 6 as the number of points in the portion representing the displacement transmission layer 6. As shown in FIG. 2, the concentration inside the center of the displacement transmission layer 6 expressed by a precise number of points is high in the concentration of silicon oxide. The silicon oxide concentration is low on both sides of the displacement transmission layer 6 such as the portion 3 side. That is, a gradient of silicon oxide concentration is formed in the displacement transmission layer 6.

  Specifically, as shown in FIG. 3, the piezoelectric element 2 has a structure in which a plurality of types (here, six types) of sheet-like layers are stacked. FIG. 3 is an exploded perspective view of the piezoelectric element 2. Hereafter, each layer which comprises the piezoelectric element 2 is demonstrated in detail, further referring FIGS. 4-9.

  First, as shown in FIG. 4, the electrode-attached ceramic layer 13 has a plurality of individual electrode patterns 18 corresponding to the internal individual electrodes 8 and a common electrode relay pattern 19 on the upper surface of the piezoelectric layer 7. Yes. The plurality of individual electrode patterns 18 are two-dimensionally arranged on the upper surface of the rectangular piezoelectric layer 7. The common electrode relay pattern 19 is formed at one end of the upper surface of the piezoelectric layer 7. The ceramic layer 13 with electrodes is provided with a plurality of through holes 20 electrically connected to the individual electrode patterns 18 and through holes 21 electrically connected to the common electrode relay pattern 19. . The through holes 20 and 21 are filled with a conductive material made of, for example, an Ag—Pd alloy.

  As shown in FIG. 5, the electrode-attached ceramic layer 14 has a plurality of individual electrode patterns 18 and a common electrode relay pattern 19 on the upper surface of the piezoelectric layer 7 in the same manner as the above-described electrode-attached ceramic layer 13. Yes. The ceramic layer 14 with an electrode is provided with a through hole 21 similar to that of the ceramic layer 13 with an electrode, but the through hole 20 is not provided.

  As shown in FIG. 6, the electrode-attached ceramic layer 15 has a common electrode pattern 22 corresponding to the internal common electrode 9 and a plurality of individual electrode relay patterns 23 on the upper surface of the piezoelectric layer 7. The common electrode pattern 22 includes a plurality of electrode pattern portions 22 a formed at positions corresponding to the individual electrode patterns 18, and an electrode pattern portion 22 b formed at positions corresponding to the common electrode relay pattern 19. The individual electrode relay pattern 23 is formed adjacent to the electrode pattern portion 22 a at a position corresponding to the individual electrode pattern 18. The ceramic layer with electrodes 15 is provided with a plurality of through holes 24 electrically connected to the individual electrode relay patterns 23 and through holes 25 electrically connected to the common electrode pattern 22. . The through holes 24 and 25 are filled with a conductive material made of, for example, an Ag—Pd alloy.

  As shown in FIG. 7, the electrode-attached ceramic layer 16 has a common electrode pattern 26 corresponding to the internal common electrode 9 on the upper surface of the displacement transmission layer 60. The electrode-attached ceramic layer 16 is not provided with individual electrode relay patterns and through holes. The common electrode pattern 26 may be formed in a solid shape on the entire upper surface of the electrode-attached ceramic layer 16.

  As shown in FIG. 8, the silicon oxide diffusion ceramic layer 161 is formed by diffusing silicon oxide on the upper surface of the displacement transmission layer 60. 8 and 3, the state in which silicon oxide diffuses into the displacement transmission layer 60 is represented by a point on the surface of the displacement transmission layer 60. This silicon oxide is transferred from the silicon oxide paste applied on the entire upper surface of the displacement transmitting ceramic green sheet, which is a precursor of the displacement transmitting layer 60, to the displacement transmitting layer 60 during the firing step. It has been diffused.

  As shown in FIG. 9, the electrode-attached ceramic layer 17 has the plurality of individual terminal electrodes 10 and the common terminal electrode 11 on the upper surface of the piezoelectric layer 7. The individual terminal electrode 10 is formed at a position corresponding to the individual electrode relay pattern 23 of the electrode-attached ceramic layer 15. The common terminal electrode 11 is formed at a position corresponding to the common electrode relay pattern 19 of the electrode-attached ceramic layer 13. The ceramic layer 17 with electrodes is provided with a plurality of through holes 27 electrically connected to the individual terminal electrodes 10 and through holes 28 electrically connected to the common terminal electrodes 11. The through holes 27 and 28 are filled with a conductive material made of, for example, an Ag—Pd alloy.

  Returning to FIG. 3, the piezoelectric element 2 includes, in order from the top, the ceramic layer with electrode 17, the ceramic layer with electrode 15, the ceramic layer with electrode 13,..., The ceramic layer with electrode 15, and the ceramic layer with electrode 14. The active region layer 5) formed by laminating the layer 7), the electrode-attached ceramic layer 16 and the silicon oxide diffusion ceramic layer 161 (hereinafter referred to as the displacement transmission layer 6) are stacked. The individual terminal electrode 10 passes through the through hole 27 of the ceramic layer 17 with electrode, the individual electrode relay pattern 23 and the through hole 24 of the ceramic layer 15 with electrode, and the individual electrode pattern 18 and the through hole 20 of the ceramic layer 13 with electrode. Thus, the individual electrode pattern 18 of the third ceramic layer 14 with electrode from the bottom is electrically connected. The common terminal electrode pattern 11 includes a through hole 28 in the ceramic layer 17 with electrode, a common electrode pattern 22 and a through hole 25 in the ceramic layer 15 with electrode, a common electrode relay pattern 19 and a through hole 21 in the ceramic layer 13 with electrode, It is electrically connected to the common electrode pattern 26 of the ceramic layer 16 with electrode through the common electrode relay pattern 19 and the through hole 21 of the ceramic layer 14 with electrode.

  Returning to FIG. 1 and FIG. 2, a voltage application lead wire 29 is joined to each individual terminal electrode 10 and common terminal electrode 11 by solder or the like. The lead wire 29 is made of, for example, a flexible printed wiring board (FPC).

  The liquid circulation part 3 located on the displacement transmission surface 12 side of the piezoelectric element 2 has a plurality of liquid chambers 30 for containing the liquid to which the displacement of the piezoelectric layer 7 is transmitted. Each liquid chamber 30 is formed at a position corresponding to each internal individual electrode 10. A liquid inlet 31 for introducing a liquid into each liquid chamber 30 is provided on one end side of the liquid circulation part 3. In addition, a plurality of liquid outlets 32 are provided at the bottom of the liquid circulation part 3 to allow the liquid to flow out of the liquid chamber 30 when the displacement of the piezoelectric layer 7 is transmitted to the liquid. The liquid circulation part 3 is formed of a metal material such as nickel alloy steel or chromium alloy steel, resin, ceramic, or the like. The liquid introduced into the liquid chamber 30 is, for example, a mixture of pure water as a main component and glycerin and a nonionic surfactant.

  Subsequently, a procedure for manufacturing the above-described piezoelectric actuator 1 (piezoelectric element manufacturing method) will be described with reference to FIG. FIG. 10 is a flowchart for explaining a procedure for manufacturing the piezoelectric actuator 1.

  First, for example, a piezoelectric ceramic powder containing PZT as a main component is prepared, and a piezoelectric ceramic paste in which an organic binder, an organic solvent, and the like are mixed is prepared (step S1).

  Next, the piezoelectric ceramic paste is formed into a sheet using the PET film as a carrier film, thereby forming a ceramic green sheet to be the piezoelectric layer 7 and a ceramic green sheet to be the displacement transmission layer 60. At this time, the piezoelectric green sheet is formed such that the thickness of the piezoelectric layer 7 after firing in step S9, which will be described later, is about 30 μm, for example. On the other hand, the thickness of the displacement transmitting green sheet is formed such that the thickness of the displacement transmitting layer 60 at a time point after the firing process of step S9 described later becomes, for example, about 15 μm (step S2, green sheet preparing process).

  Next, through holes are formed in the green sheet by, for example, irradiating a predetermined position of the green sheet with a third harmonic laser beam of YAG to make a hole. At this time, the through hole is processed so that the hole diameter becomes, for example, 40 μm after the firing step of Step S9 described later. Then, for example, a conductive paste in which a conductive material configured in a ratio of Ag: Pd = 7: 3 and an organic binder / organic solvent is mixed is prepared, and the conductive paste is filled into the through hole by, for example, screen printing ( Step S3).

  Next, for example, using the same conductive paste as the conductive paste filled in the through holes, an internal electrode pattern is formed on one surface of the piezoelectric green sheet by, for example, screen printing. (Step S4).

  Next, for example, by using a conductive paste similar to the conductive paste filled in the through hole, an internal electrode pattern is formed on one surface of the displacement transmitting green sheet by, for example, a screen printing method. (Step S5).

Next, a silicon oxide paste is prepared and applied to a displacement transmitting green sheet. At this time, the silicon oxide paste is applied to the entire surface of the displacement transmitting green sheet with a thickness of about 2 μm, for example, by screen printing. The silicon oxide paste is produced, for example, by mixing SiO ₂ in an organic binder / organic solvent at 30% by weight (step S6).

  Next, a predetermined number (see FIG. 3) of green sheets on which internal electrode patterns are printed and green sheets coated with silicon oxide paste are stacked in a predetermined order (see FIG. 3) to form a green laminate 4. At this time, as shown in FIG. 3, in the ceramic green sheet to be the silicon oxide diffusion ceramic layer 161 later, the one side coated with the silicon oxide paste is laminated so as to be in contact with the ceramic green sheet to be the ceramic layer 16 with electrode later. Then, the green laminated body 4 is formed (step S7, green laminated body forming step).

  Next, the green laminate 4 formed in step S7 is pressed at a pressure of about 100 MPa while applying heat of about 60 ° C., for example, and the green sheets of the respective layers are pressure-bonded (step S8).

  Next, the green laminated body 4 is cut into a predetermined dimension. Then, the green laminate 4 is placed on a setter, and the green laminate 4 is degreased (binder removed) at a temperature of about 400 ° C. for about 10 hours, for example. Thereafter, the setter on which the green laminated body 4 is placed is put in a closed mortar, and the green laminated body 4 is fired at a temperature of, for example, about 1100 ° C. for about 2 hours. The laminated body 4 is obtained (step S9).

  Next, the individual terminal electrode 10 and the common terminal electrode 11 made of, for example, Ag are formed on the upper surface of the green laminate 4 after firing. As a method for forming the terminal electrodes 10 and 11, baking, sputtering, electroless plating, or the like is used (step S10).

  Next, the lead wires 29 are connected to the terminal electrodes 10 and 11 by solder or the like. Then, for example, under a temperature of 120 ° C., a polarization process is performed by applying a predetermined voltage, for example, for 3 minutes so that the electric field strength with respect to the thickness of the piezoelectric layer 7 becomes 3 kV / mm. Thereby, the piezoelectric element 2 is completed (step S11).

  Then, the piezoelectric actuator 1 is obtained by sticking the separately produced liquid circulation part 3 to the bottom surface (displacement transmission surface) 12 of the piezoelectric element 2 with an adhesive (step S12).

  The piezoelectric actuator 1 obtained by such a procedure operates as follows. That is, each liquid chamber 30 of the liquid circulation part 3 contains liquid in advance, and the liquid is in contact with the bottom surface 12 of the piezoelectric element 2. In this state, when a predetermined voltage is applied via the lead wire 29 between any of the individual terminal electrodes 10 and the common terminal electrode 11 so that the common terminal electrode 11 is at the GND potential, the selected individual terminal electrode is selected. A voltage is applied between the internal individual electrode 8 corresponding to 10 and the internal common electrode 9. As a result, an electric field is generated in a portion (piezoelectric active portion 7 a) between the internal individual electrode 8 and the internal common electrode 9 in the piezoelectric layer 7 of each layer, and the piezoelectric active portion 7 a extends in the stacking direction of the green laminate 4. It will be displaced. Then, the displacement of the piezoelectric active portion 7 a is transmitted to the liquid in the corresponding liquid chamber 30 through the displacement transmission layer 6. As a result, the volume of the liquid chamber 30 is reduced, and an amount of liquid corresponding to the volume reduction is discharged from the liquid outlet 32.

  Then, the effect | action and effect of 1st Embodiment are demonstrated. The green laminate 4 formed by the piezoelectric element manufacturing method of the first embodiment includes a silicon oxide paste (silicon oxide layer), a piezoelectric layer 7 and a displacement transmission layer 6. In this case, the silicon oxide that has formed the silicon oxide paste diffuses into the displacement transmission layer 6 in the firing step of step S9. The silicon oxide soaked into the displacement transmission layer 6 fills the gaps between the particles of the displacement transmission layer 6. As a result, when the displacement of the piezoelectric layer 7 is transmitted to the liquid object via the displacement transmission layer 6, the electroosmosis phenomenon of the liquid in contact with the displacement transmission layer 6 is prevented. Such characteristic deterioration can be suppressed. As a result, the reliability of the piezoelectric element 2 can be improved.

  Further, since silicon oxide diffuses into the displacement transmission layer 6, a gradient of silicon oxide concentration is formed in the displacement transmission layer 6. For this reason, the concentration inside the center of the displacement transmission layer 6 having both ends of the active region layer 5 side and the liquid circulation part 3 side is high, and the electroosmosis phenomenon is surely prevented. The active region layer 5 side has a low concentration of silicon oxide and hardly affects the piezoelectric characteristics of the piezoelectric element 2. That is, according to the method for manufacturing the piezoelectric element 2 of the first embodiment, the electroosmosis phenomenon can be reliably prevented without affecting the original piezoelectric characteristics of the piezoelectric element 2.

  Therefore, it is not necessary to provide a partition wall between the piezoelectric element 2 and the liquid circulation part 3 in order to avoid insulation failure of the piezoelectric element 2 and the like. For this reason, since the displacement transmission of the piezoelectric layer 7 to the liquid is not hindered by the partition walls, it is not necessary to increase the number of layers of the green laminate 4 more than necessary in order to compensate for the loss of the transmission displacement amount by the partition walls. . As a result, the piezoelectric element 2 and thus the piezoelectric actuator 1 can be reduced in size, and an increase in manufacturing cost thereof can be suppressed.

  In order to verify the effect of the first embodiment described above, an experiment was performed as follows. First, as a sample of an element including a silicon oxide layer in the displacement transmission layer 6, ten piezoelectric elements 2 manufactured by the manufacturing method of the first embodiment are prepared. Further, as a sample of an element not including the silicon oxide layer in the displacement transmission layer 6, a piezoelectric element manufactured by doubling the thickness of the electrode-attached ceramic layer 16 instead of the silicon oxide diffusion ceramic layer 161 shown in FIG. 10 pieces of 2 ′ are prepared. Then, a lead wire 29 was attached to each piezoelectric element so that a voltage could be applied to the terminal electrode. Subsequently, a liquid was filled in the liquid circulation portion of each piezoelectric actuator and sealed. As the liquid, pure water was used as a main component, and a mixture of glycerin and a nonionic surfactant was used. Subsequently, a DC voltage of 1 kV / mm per piezoelectric layer thickness was simultaneously applied to all the individual terminal electrodes. Then, static electricity was periodically applied to each piezoelectric actuator to charge the liquid.

  Thus, each piezoelectric actuator was continuously driven for 500 hours, and the state before and after driving each piezoelectric actuator was confirmed. Specifically, after 500 hours from the start of driving of each piezoelectric actuator, the liquid was discharged from the liquid circulation portion, and the insulation resistance of each piezoelectric element was examined.

As a result of the above comparative experiment, it was confirmed that the change in the insulation resistance value was not observed before and after the experiment in the element including the silicon oxide layer in the displacement transmission layer 6. On the other hand, in an experiment with respect to an element that does not include the silicon oxide layer in the displacement transmission layer 6, deterioration of the insulation resistance value was recognized for all the elements. Further, in an experiment for an element that does not include the silicon oxide layer in the displacement transmission layer 6, a value (1 × 10 ⁸ to 1 × 10 ⁶ ) in which the insulation resistance value is deteriorated by 4 digits or more compared to the initial value (1 × 10 ¹⁰ ). ) In some cases.

[Second Embodiment]
Hereinafter, a method of manufacturing the piezoelectric element 2 according to the second embodiment of the present invention will be described with reference to FIGS. In the following, only parts different from the first embodiment will be described for the sake of simplicity.

  FIG. 11 is an exploded perspective view of the piezoelectric element 2 manufactured by the manufacturing method of the second embodiment. In the green laminated body formation process of step S7 in the manufacturing method of 2nd Embodiment, as shown in FIG. 11, in the ceramic green sheet used as the silicon oxide diffusion ceramic layer 161 later, the surface where the silicon oxide paste is not apply | coated is Thereafter, the green laminate 4 is formed by laminating the ceramic green sheets to be in contact with the ceramic layer 16 with electrodes. A silicon oxide paste is applied to the other surface of the ceramic green sheet that will later become the silicon oxide diffusion ceramic layer 161 (the surface opposite to the ceramic green sheet side that will later become the ceramic layer 16 with electrode). (A silicon oxide layer is formed).

  FIG. 12 is a partial cross-sectional view of the piezoelectric actuator 1 manufactured by the above manufacturing method. As shown in FIG. 12, the displacement transmission layer 6 is infiltrated with silicon oxide. This silicon oxide has been diffused from the silicon oxide paste applied to the other surface of the ceramic green sheet that will later become the silicon oxide diffusion ceramic layer 161.

  FIG. 12 illustrates the concentration of silicon oxide in the displacement transmission layer 6 as the number of points in the portion representing the displacement transmission layer 6. As shown in FIG. 12, the concentration of silicon oxide is high on the liquid flow passage 3 side of the displacement transmission layer 6 represented by a precise number of points, and the opposite side of the liquid flow passage 3 side, that is, the active region layer 5. On the side, the concentration of silicon oxide is low. That is, a gradient of silicon oxide concentration is formed in the displacement transmission layer 6.

  Then, the effect | action and effect of 2nd Embodiment are demonstrated. The green laminated body 4 formed by the piezoelectric element manufacturing method of the second embodiment includes a silicon oxide paste (silicon oxide layer), a piezoelectric layer 7 and a displacement transmission layer 6. In this case, the silicon oxide that has formed the silicon oxide paste diffuses into the displacement transmission layer 6 in the firing step of step S9. The silicon oxide soaked into the displacement transmission layer 6 fills the gaps between the particles of the displacement transmission layer 6. As a result, when the displacement of the piezoelectric layer 7 is transmitted to the liquid object via the displacement transmission layer 6, the electroosmosis phenomenon of the liquid in contact with the displacement transmission layer 6 is prevented. Such characteristic deterioration can be suppressed. As a result, the reliability of the piezoelectric element 2 can be improved.

  Further, since silicon oxide diffuses into the displacement transmission layer 6, a gradient of silicon oxide concentration is formed in the displacement transmission layer 6. For this reason, the concentration of silicon oxide is high on the liquid flow section 3 side of the displacement transmission layer 6, and the electroosmosis phenomenon is reliably prevented. Further, the active region layer 5 side of the displacement transmission layer 6 has a low concentration of silicon oxide and hardly affects the piezoelectric characteristics of the piezoelectric element 2. That is, according to the method for manufacturing the piezoelectric element 2 of the second embodiment, the electroosmotic phenomenon can be reliably prevented without affecting the original piezoelectric characteristics of the piezoelectric element 2.

  Therefore, it is not necessary to provide a partition wall between the piezoelectric element 2 and the liquid circulation part 3 in order to avoid insulation failure of the piezoelectric element 2 and the like. For this reason, since the displacement transmission of the piezoelectric layer 7 to the liquid is not hindered by the partition walls, it is not necessary to increase the number of layers of the green laminate 4 more than necessary in order to compensate for the loss of the transmission displacement amount by the partition walls. . As a result, the piezoelectric element 2 and thus the piezoelectric actuator 1 can be reduced in size, and an increase in manufacturing cost thereof can be suppressed.

[Third Embodiment]
Hereinafter, the manufacturing method of the piezoelectric element 2 according to the third embodiment of the present invention will be described with reference to FIGS. In the following, only parts different from the first embodiment will be described for the sake of simplicity.

  FIG. 13 is a flowchart for explaining the manufacturing method according to the third embodiment. In the third embodiment, as shown in FIG. 13, after step S <b> 5 in which electrodes are formed on the displacement transmitting green sheet, a green laminate forming process in step S <b> 7 is performed. In this green laminated body forming step, as shown in FIG. 14, a predetermined number of green sheets on which internal electrode patterns are printed and displacement transmitting green sheets to which no silicon oxide paste is applied are predetermined. The green laminate 4 is formed by laminating in order. FIG. 14 is an exploded perspective view of the piezoelectric element 2 for explaining the manufacturing method of the third embodiment. In FIG. 14, the silicon oxide paste is not applied to any one surface of the displacement transmitting green sheet.

  Next, the green laminate 4 formed in step S7 is pressed at a pressure of about 100 MPa while applying heat of about 60 ° C., for example, and the green sheets of the respective layers are pressure-bonded (step S8).

  Next to the pressing process in step S8, a silicon oxide paste prepared by mixing 30% by weight of silicon oxide with an organic binder, an organic solvent, or the like is applied to one surface of the green laminate 4 shown in FIG. The coating is applied to the entire surface (the entire surface of the green laminate 4 on the side that will later become the displacement transmission layer 6) with a thickness of about 2 μm (step S61).

  And the process after step S9 is performed similarly to 1st Embodiment with respect to the green laminated body 4 to which the silicon oxide paste was apply | coated in step S61, and the piezoelectric actuator 1 is obtained.

  FIG. 12 shows the piezoelectric actuator 1 manufactured by the manufacturing method of the third embodiment. As shown in FIG. 12, the displacement transmission layer 6 is infiltrated with silicon oxide. This silicon oxide has been diffused into the displacement transmission layer 6 from the silicon oxide paste applied in step S61 after the formation of the green laminate 4 in step S7 and the press working in step S8.

  FIG. 12 illustrates the concentration of silicon oxide in the displacement transmission layer 6 as the number of points in the portion representing the displacement transmission layer 6. As shown in FIG. 12, the concentration of silicon oxide is high on the liquid flow passage 3 side of the displacement transmission layer 6 represented by a precise number of points, and the opposite side of the liquid flow passage 3 side, that is, the active region layer 5. On the side, the concentration of silicon oxide is low. That is, a gradient of silicon oxide concentration is formed in the displacement transmission layer 6.

  Then, the effect | action and effect of 3rd Embodiment are demonstrated. According to the piezoelectric element manufacturing method of the third embodiment, the silicon oxide paste is applied to the green laminate 4 in step S61. In this case, the silicon oxide that has formed the silicon oxide paste diffuses into the displacement transmission layer 6 in the firing step of step S9. The silicon oxide soaked into the displacement transmission layer 6 fills the gaps between the particles of the displacement transmission layer 6. As a result, when the displacement of the piezoelectric layer 7 is transmitted to the liquid object via the displacement transmission layer 6, the electroosmosis phenomenon of the liquid in contact with the displacement transmission layer 6 is prevented. Such characteristic deterioration can be suppressed. As a result, the reliability of the piezoelectric element 2 can be improved.

  Further, since silicon oxide diffuses into the displacement transmission layer 6, a gradient of silicon oxide concentration is formed in the displacement transmission layer 6. For this reason, the concentration of silicon oxide is high on the liquid flow section 3 side of the displacement transmission layer 6, and the electroosmosis phenomenon is reliably prevented. Further, the active region layer 5 side of the displacement transmission layer 6 has a low concentration of silicon oxide and hardly affects the piezoelectric characteristics of the piezoelectric element 2. That is, according to the method for manufacturing the piezoelectric element 2 of the third embodiment, the electroosmosis phenomenon can be reliably prevented without affecting the original piezoelectric characteristics of the piezoelectric element 2.

  Therefore, it is not necessary to provide a partition wall between the piezoelectric element 2 and the liquid circulation part 3 in order to avoid insulation failure of the piezoelectric element 2 and the like. For this reason, since the displacement transmission of the piezoelectric layer 7 to the liquid is not hindered by the partition walls, it is not necessary to increase the number of layers of the green laminate 4 more than necessary in order to compensate for the loss of the transmission displacement amount by the partition walls. . As a result, the piezoelectric element 2 and thus the piezoelectric actuator 1 can be reduced in size, and an increase in manufacturing cost thereof can be suppressed.

  The piezoelectric element and the piezoelectric actuator according to the present invention are not limited to the above three embodiments. For example, in the above embodiment, a plurality of piezoelectric layers 7 are stacked, but the piezoelectric layer 7 may be a single layer as long as a large amount of displacement is not required. The displacement transmission layer 6 may also be configured as a single layer.

  Further, the number and arrangement of the internal individual electrodes 8 in each layer are not particularly limited to those in the above embodiment. In addition, the electrical connection means between the internal individual electrodes 8 of each layer and the internal common electrodes 9 of each layer is not limited to the through-hole as in the above-described embodiment. For example, the external electrode formed on the side surface of the green laminate 4 It is also good.

It is a perspective view which shows the piezoelectric actuator 1 manufactured by the manufacturing method concerning 1st Embodiment. FIG. 2 is a partial side sectional view of the piezoelectric actuator 1 shown in FIG. 1. FIG. 3 is an exploded perspective view of the piezoelectric element 2 shown in FIG. 2. It is a top view which shows the ceramic layer 13 with an electrode shown in FIG. It is a top view which shows the ceramic layer 14 with an electrode shown in FIG. It is a top view which shows the ceramic layer 15 with an electrode shown in FIG. It is a top view which shows the ceramic layer 16 with an electrode shown in FIG. FIG. 4 is a plan view showing a silicon oxide diffusion ceramic layer 161 shown in FIG. 3. It is a top view which shows the ceramic layer 17 with an electrode shown in FIG. It is a flowchart which shows the manufacturing method concerning 1st Embodiment. It is a disassembled perspective view of the piezoelectric element 2 by the manufacturing method of 2nd Embodiment. It is a partial sectional side view of the piezoelectric actuator 1 by the manufacturing method of 2nd Embodiment. It is a flowchart which shows the manufacturing method concerning 3rd Embodiment. It is a disassembled perspective view of the piezoelectric element 2 by the manufacturing method of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric actuator, 2 ... Piezoelectric element, 3 ... Liquid distribution | circulation part, 6 ... Displacement transmission layer, 7 ... Piezoelectric layer, 8 ... Internal separate electrode, 9 ... Internal common electrode.

Claims (4)

A method of manufacturing a piezoelectric element having a piezoelectric layer and a displacement transmission layer for transmitting displacement of the piezoelectric layer,
A green sheet preparation step of preparing a piezoelectric ceramic green sheet as a precursor of the piezoelectric layer and a displacement transmitting ceramic green sheet as a precursor of the displacement transmitting layer;
A green laminated body forming step of forming a green laminated body in which the ceramic green sheet for piezoelectric bodies and the ceramic green sheet for displacement transmission are laminated,
The green laminated body formation step, have a step of forming a silicon oxide layer of silicon oxide on the ceramic green sheet for the displacement transmission,
In the green laminated body forming step, the displacement transmitting ceramic green sheet on which the silicon oxide layer is formed by the step of forming the silicon oxide layer is used, and the silicon oxide layer is on the piezoelectric ceramic green sheet side. A method of manufacturing a piezoelectric element, characterized in that the green laminate is formed by laminating as described above . In the green laminated body formation step, claim 1, characterized in that forming the green laminate displacement transmitting ceramic green sheet further laminated between the piezoelectric ceramic green sheets and the silicon oxide layer The manufacturing method of the piezoelectric element as described in any one of. A method of manufacturing a piezoelectric element having a piezoelectric layer and a displacement transmission layer for transmitting displacement of the piezoelectric layer,
A green sheet preparation step of preparing a piezoelectric ceramic green sheet as a precursor of the piezoelectric layer and a displacement transmitting ceramic green sheet as a precursor of the displacement transmitting layer;
A green laminated body forming step of forming a green laminated body in which the ceramic green sheet for piezoelectric bodies and the ceramic green sheet for displacement transmission are laminated,
The green laminate forming step includes a step of forming a silicon oxide layer made of silicon oxide on the displacement-transmitting ceramic green sheet;
In the green laminate forming step, the displacement transmitting ceramic green sheet in which the silicon oxide layer is formed in the step of forming the silicon oxide layer is used as the displacement transmitting ceramic green sheet. The green laminated body is formed by laminating so as to be on the side, and a method for manufacturing a piezoelectric element. A method of manufacturing a piezoelectric element having a piezoelectric layer and a displacement transmission layer for transmitting displacement of the piezoelectric layer,
A green sheet preparation step of preparing a piezoelectric ceramic green sheet as a precursor of the piezoelectric layer and a displacement transmitting ceramic green sheet as a precursor of the displacement transmitting layer;
A green laminated body forming step of forming a green laminated body in which the ceramic green sheet for piezoelectric bodies and the ceramic green sheet for displacement transmission are laminated,
The green laminate forming step includes a step of forming a silicon oxide layer made of silicon oxide on the displacement-transmitting ceramic green sheet;
In the green laminate forming step, after the piezoelectric ceramic green sheet and the displacement transmitting ceramic green sheet are laminated, the silicon oxide layer is formed on the displacement transmitting ceramic green sheet by the step of forming the silicon oxide layer. A method of manufacturing a piezoelectric element, wherein the green laminate is formed by forming a layer.

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