JP2011054628A - Method of manufacturing piezoelectric actuator - Google Patents

Abstract

Disclosed is a method for manufacturing a piezoelectric actuator in which electrodes are accurately formed in as short a time as possible.
To manufacture a piezoelectric actuator, first, a plurality of individual electrodes 43 are formed on the upper surface of a vibration plate 41, and then a piezoelectric layer is formed on the upper surface of the vibration plate 41 so as to cover the plurality of individual electrodes 43. 42 is formed (individual electrode forming step). Next, the conductive film 51 is formed on almost the entire upper surface of the piezoelectric layer 42 (conductive film forming step), and then the common electrode 44 is cut out from the conductive film 51 by laser processing (laser processing step). In the laser processing step, when cutting out the connecting portion 44b and the connecting portion 44c, the laser output energy is increased and the laser scanning speed is increased as compared with cutting out the plurality of facing portions 44a. At this time, the remaining portion of the conductive film 51 from which the common electrode 44 is cut out becomes the common electrode 45.
[Selection] Figure 7

Description

  The present invention relates to a method for manufacturing a piezoelectric actuator having a piezoelectric layer sandwiched between individual electrodes and a common electrode.

  In Patent Document 1, a piezoelectric layer is laminated on a top plate (vibration plate) disposed at the upper end of a flow path unit, and an individual electrode facing the pressure chamber is disposed on one surface of these piezoelectric layers. The first constant potential electrode (first common electrode) facing the substantially central portion of the individual electrode on the other surface, and the second constant potential electrode (first electrode facing both ends of the individual electrode in the short direction) A piezoelectric actuator in which two common electrodes) are arranged is described. In the piezoelectric actuator having such a configuration, the portion of the piezoelectric layer facing the individual electrode and the first constant potential electrode, and the portion facing the individual electrode and the second constant potential electrode are simultaneously deformed, The portion of the piezoelectric layer and the diaphragm facing the pressure chamber is deformed, so that the deformation of the portion of the piezoelectric layer facing the pressure chamber propagates to the portion facing the other pressure chamber. Crosstalk can be prevented.

JP 2009-96173 A (FIG. 16)

  Here, when a piezoelectric actuator having such a configuration is manufactured, it is opposed to the individual electrode and the individual electrodes of the two types of common electrodes from the viewpoint of uniform drive characteristics of the portion corresponding to each pressure chamber of the piezoelectric actuator. It is preferable that the portion to be formed is formed with high accuracy. As a method for accurately forming these electrodes, a method is conceivable in which a conductive film is formed in a region extending over a plurality of pressure chambers on the piezoelectric layer, and the electrode is cut out from the conductive film by laser processing. .

  However, when an electrode is formed by cutting an electrode from a conductive film by laser processing, an electrode can be formed more accurately than when an electrode is formed by printing, but the electrode is formed. It takes a lot of time.

  In addition to the piezoelectric actuator in which two types of common electrodes are arranged on the same surface of the piezoelectric layer as described above, for example, in the above-described piezoelectric actuator, only one of the two types of common electrodes is used as the common electrode. Also in the piezoelectric actuator and the like, it is preferable to form the individual electrode and the portion of the common electrode facing the individual electrode with high accuracy, as in the above-described piezoelectric actuator. However, as described above, when the electrode is formed by laser processing Requires a lot of time to form the electrodes.

  An object of the present invention is to provide a method of manufacturing a piezoelectric actuator capable of forming electrodes with high accuracy by laser processing and shortening the time required for forming the electrodes as much as possible.

  According to a first aspect of the present invention, there is provided a piezoelectric actuator manufacturing method comprising: a piezoelectric layer; a plurality of individual electrodes disposed on one surface of the piezoelectric layer; and a surface of the piezoelectric layer opposite to the plurality of individual electrodes. A first common electrode, wherein the first common electrode has a plurality of facing portions that face the plurality of individual electrodes, and a connection portion that connects the plurality of facing portions to each other. In the manufacturing method, the individual electrode forming step of forming the plurality of individual electrodes on the one surface of the piezoelectric layer, and the first common electrode on the surface of the piezoelectric layer opposite to the plurality of individual electrodes. A common electrode forming step to be formed, and the common electrode forming step continuously extends on a surface opposite to the plurality of individual electrodes of the piezoelectric layer across a portion facing the plurality of individual electrodes. Type to form a conductive film And a laser processing step of cutting out the first common electrode from the conductive film by laser processing, and in the laser processing step, when cutting out the plurality of facing portions when cutting out the connection portion In addition, the laser output energy is increased and the scanning speed of the laser is increased.

  According to this, when cutting out the facing part that requires high accuracy, the laser output energy is reduced and the moving speed of the laser is reduced, and when cutting out the connection part that does not require so high accuracy, By increasing the output energy and increasing the moving speed of the laser, the facing portion can be formed with high accuracy in the laser processing step, and the time required for the entire laser processing step can be shortened as much as possible.

  A method for manufacturing a piezoelectric actuator according to a second invention is a method for manufacturing a piezoelectric actuator according to the first invention, wherein the plurality of facing portions are opposed to a part of corresponding individual electrodes, and the piezoelectric actuator is A second common electrode disposed on a surface of the piezoelectric layer opposite to the plurality of individual electrodes, and facing a portion different from the portion of the plurality of individual electrodes, In the laser processing step, by cutting out the first common electrode from the conductive film, a portion of the conductive film excluding the first common electrode becomes the second common electrode. .

  According to this, the first common electrode and the second common electrode can be formed simultaneously in the laser processing step.

  A method for manufacturing a piezoelectric actuator according to a third invention is a method for manufacturing a piezoelectric actuator according to the second invention, wherein in the laser processing step, a portion of the conductive film excluding the first common electrode is further provided. Among them, a part of the portion not facing the plurality of individual electrodes is removed.

  According to this, a portion of the conductive film excluding the first common electrode that is not necessary as the second common electrode is removed, and thus a part of the conductive electrode that is not opposed to the individual electrode is removed. Capacitance and heat generation can be reduced.

  According to the present invention, in the laser processing step of cutting out the first common electrode from the conductive film, the facing portion can be formed with high accuracy, and the time required for the entire laser processing step can be shortened as much as possible.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. It is a top view of the inkjet head of FIG. FIG. 3 is a plan view of the upper surface of a diaphragm in the inkjet head of FIG. 2. FIG. 3 is a plan view of the upper surface of a piezoelectric layer in the ink jet head of FIG. 2. It is the VV sectional view taken on the line of FIG. It is the VI-VI sectional view taken on the line of FIG. It is a figure which shows the manufacturing process of a piezoelectric actuator. It is a figure which shows typically the area | region removed by laser processing. It is a figure equivalent to Drawing 7 (d) of modification 1.

  Hereinafter, preferred embodiments of the present invention will be described.

  FIG. 1 is a schematic configuration diagram of a printer according to the first embodiment. As shown in FIG. 1, the printer 1 includes a carriage 2, an inkjet head 3, a transport roller 4, and the like. The carriage 2 reciprocates along a guide shaft 5 that extends in the scanning direction (left-right direction in FIG. 1). The inkjet head 3 is disposed on the lower surface of the carriage 2 and ejects ink from nozzles 15 (see FIG. 2) disposed on the lower surface thereof. The transport roller 4 transports the recording paper P in the paper feed direction (front side in FIG. 1).

  In the printer 1, printing is performed on the recording paper P by ejecting ink from the inkjet head 3 that reciprocates in the scanning direction together with the carriage 2 onto the recording paper P that is transported in the paper feeding direction by the transport roller 4. . Further, the recording paper P for which printing has been completed is discharged by being conveyed in the paper feeding direction by the conveying roller 4.

  Next, the inkjet head 3 will be described. FIG. 2 is a plan view of the inkjet head 3 of FIG. FIG. 3 is a plan view of the upper surface of a diaphragm 41 described later in FIG. 4 is a plan view of the upper surface of a piezoelectric layer 42 described later in FIG. In order to make the positional relationship easy to understand, in FIG. 3, a piezoelectric layer 42 to be described later is indicated by a two-dot chain line.

  As shown in FIGS. 5 and 6, the inkjet head 3 is disposed on a flow path unit 31 in which an ink flow path including the pressure chamber 10 and the nozzle 15 is formed, and on the upper surface of the flow path unit 31. And a piezoelectric actuator 32 that applies pressure to the ink in the pressure chamber 10.

  The flow path unit 31 is formed by stacking four plates of a cavity plate 21, a base plate 22, a manifold plate 23, and a nozzle plate 24. Of these four plates 21 to 24, the three plates 21 to 23 excluding the nozzle plate 24 are made of a metal material such as stainless steel, and the nozzle plate 24 is made of a synthetic resin material such as polyimide. Or the nozzle plate 24 may also be comprised with the metal material similar to the other three plates 21-23.

  A plurality of pressure chambers 10 and ink supply ports 9 (see FIG. 2) are formed in the cavity plate 21. The pressure chambers 10 have a substantially oval planar shape with the scanning direction (left-right direction in FIG. 2) as the longitudinal direction, and are arranged in two rows along the paper feed direction. In the base plate 22, substantially circular through holes 12 and 13 are formed at portions facing both ends of the plurality of pressure chambers 10 in the scanning direction, respectively. Further, the ink supply port 9 is formed at a position communicating with a manifold channel 11 described later.

  The manifold plate 23 is formed with a manifold channel 11 extending in the paper feed direction (vertical direction in FIG. 2) so as to overlap substantially half of the through-hole 12 side in the scanning direction of the pressure chambers 10 in each row. Here, ink is supplied to the manifold channel 11 from the ink supply port 9. Further, a substantially circular through hole 14 is formed in the manifold plate 23 at a portion overlapping the through hole 13. A nozzle 15 is formed in the nozzle plate 24 at a portion overlapping the through hole 14.

  In the flow path unit 31, the manifold flow path 11 communicates with the pressure chamber 10 through the through hole 12, and the pressure chamber 10 communicates with the nozzle 15 through the through holes 13 and 14. As described above, the flow path unit 31 is formed with a plurality of individual ink flow paths from the outlet of the manifold flow path 11 to the nozzle 15 through the pressure chamber 10.

  The piezoelectric actuator 32 includes a vibration plate 41, a piezoelectric layer 42, a plurality of individual electrodes 43, common electrodes 44 and 45, an insulating layer 46, and a plurality of wirings 47.

  The diaphragm 41 is disposed on the upper surface of the cavity plate 21 so as to cover the plurality of pressure chambers 10. The diaphragm 41 is made of, for example, alumina, zirconia, a ceramic material such as PZT described later, or a metal material such as stainless steel. However, when the vibration plate 41 is made of a metal material, the vibration plate 41 has conductivity. Therefore, in order to prevent conduction between the vibration plate 41 and the individual electrode 43 and the wiring 47 described later, the vibration plate It is necessary to dispose an insulating layer (not shown) made of a ceramic material on the upper surface of 41 and dispose the individual electrodes 43 and wirings 47 thereon.

  The piezoelectric layer 42 is made of a piezoelectric material (PZT) whose main component is lead zirconate titanate, which is a mixed crystal of lead titanate and lead zirconate. The piezoelectric layer 42 is disposed on the upper surface of the vibration plate 41 and continuously extends across a portion facing the plurality of pressure chambers 10.

  The plurality of individual electrodes 43 are arranged on the upper surface of the vibration plate 41 (the lower surface (one surface) of the piezoelectric layer 42) corresponding to the plurality of pressure chambers 10. The plurality of individual electrodes 43 have a substantially oval planar shape that is slightly larger than the pressure chamber 10, and are arranged so as to completely cover the plurality of pressure chambers 10. Thereby, the plurality of individual electrodes 43 are arranged in two rows in the paper feed direction, like the plurality of pressure chambers 10. The plurality of individual electrodes 43 are connected to a driver IC 50 as will be described later, and the driver IC 50 selectively applies either a ground potential or a predetermined positive potential (for example, about 20 V). Is done.

  The common electrode 44 (first common electrode) is disposed on the upper surface (the surface opposite to the individual electrode 43) of the piezoelectric layer 42 and is connected to the driver IC 50 as described later. It is held at ground potential. The common electrode 44 has a plurality of facing portions 44a, two connecting portions 44b, and a connecting portion 44c.

  The plurality of facing portions 44a have a substantially elliptical planar shape that is slightly smaller than the pressure chamber 10, and are disposed so as to face the substantially central portion of the plurality of pressure chambers 10 (individual electrodes 43). Thus, the plurality of facing portions 44 a are arranged in two rows along the paper feed direction, like the plurality of individual electrodes 43.

  The two connecting portions 44b extend in the paper feeding direction, and the left end portions of the plurality of facing portions 44a constituting the left row in FIG. 2 and the plurality of facing portions 44a constituting the right row, respectively. Are connected to each other at their right ends. The connecting portion 44c extends in the scanning direction and connects the upper ends of the two connecting portions 44b in FIG. In the present embodiment, the combination of the two connecting portions 44b and the connecting portion 44c corresponds to the connecting portion according to the present invention.

  The common electrode 45 (second common electrode) is disposed in a region surrounded by the two connection portions 44b and the connection portion 44c on the upper surface of the piezoelectric layer 42 where the common electrode 44 is disposed. A plurality of facing portions 45a and connecting portions 45b are provided. The plurality of facing portions 45 a are disposed so as to face a portion outside the portion facing the common electrode 44 of the pressure chamber 10. The connecting portion 45b is a portion of the common electrode 45 excluding the plurality of facing portions 45a, and connects the plurality of facing portions 45a to each other.

  The common electrode 45 is connected to a driver IC 50 as will be described later, and is always held at the predetermined positive potential by the driver IC 50.

  Here, in the piezoelectric layer 42 described above, a portion sandwiched between the individual electrode 43 and the common electrode 44 (opposing portion 44a) and a portion sandwiched between the individual electrode 43 and the common electrode 45 (opposing portion 45a). Is polarized in the thickness direction of the piezoelectric layer 42.

  The insulating layer 46 is made of an insulating material such as a ceramic material such as alumina, zirconia, or PZT, or a synthetic resin material, and is disposed so as to cover the common electrodes 44 and 45 over almost the entire upper surface of the piezoelectric layer 42. . The common electrode 44 and the common electrode 45 are disposed close to each other on the upper surface of the same piezoelectric layer 42 and are held at different potentials, but an insulating layer 46 covering the common electrodes 44 and 45 is disposed. Therefore, the common electrode 44 and the common electrode 45 can be prevented from conducting due to migration of the material forming the electrode.

  The plurality of wirings 47 include a plurality of wirings 47a individually connected to the plurality of individual electrodes 43, a wiring 47b connected to the common electrode 44, and a wiring 47c connected to the common electrode 45. One end of the wiring 47 is connected to the electrodes 43, 44 and 45, and the other end is connected to a driver IC 50 disposed on the diaphragm 41. 2 to 4, only the portion in the vicinity of the connection portion with the electrodes 43 to 45 and the portion in the vicinity of the connection portion with the driver IC 50 among the plurality of wirings 47 are illustrated, and other portions are illustrated. About is omitted.

  The wiring 47a to 47c will be described in more detail. One end of the wiring 47a is connected to the end of the individual electrode 43 opposite to the nozzle 15 in the scanning direction, and the individual electrode 43 is arranged from this portion. The other end of the diaphragm 41 is connected to the driver IC 50.

  One end of the wiring 47b is connected to the upper end portion of the right connection portion 44b in FIG. 2 on the upper surface of the piezoelectric layer 42, and passes through the right side surface of the piezoelectric layer 42 in FIG. The upper surface of the vibration plate 41 is drawn out, and the upper surface of the vibration plate 41 is further drawn, and the other end is connected to the driver IC 50.

  One end of the wiring 47c is connected to the lower left end portion of the common electrode 45 in FIG. 2 on the upper surface of the piezoelectric layer 42, and passes through the lower side surface of the piezoelectric layer 42 in FIG. The upper surface of the vibration plate 41 is drawn out, and the upper surface of the vibration plate 41 is further drawn, and the other end is connected to the driver IC 50.

  Note that the connection position of the wiring 47 with the electrodes 43 to 45 and the way of routing the wiring 47 are not limited to those described above. Further, the driver IC 50 may also be disposed on a surface other than the upper surface of the diaphragm 41. Furthermore, the wiring 47 is not provided, and the electrodes 43 to 45 are connected to a wiring formed on a flexible wiring board (FPC) disposed above the piezoelectric actuator 32, and through this wiring. It may be connected to a driver IC located at a position away from the piezoelectric actuator 32.

  Here, a driving method of the piezoelectric actuator 32 will be described. In the piezoelectric actuator 32, the plurality of individual electrodes 43 are previously held at the ground potential. In this state, a potential difference is generated between the individual electrode 43 and the common electrode 45 (opposing portion 45a), and an electric field in a direction parallel to the polarization direction is applied to the portion of the piezoelectric layer 42 sandwiched between these electrodes. Has occurred. As a result, this portion of the piezoelectric layer 42 is contracted in the horizontal direction orthogonal to the direction of the electric field, and as a result, the portions of the diaphragm 41, the piezoelectric layer 42, and the insulating layer 46 that face the pressure chamber 10 as a whole. The pressure chamber 10 is deformed so as to be convex on the opposite side, and the volume of the pressure chamber 10 is larger than that in a state where the vibration plate 41 and the piezoelectric layer 42 are not deformed.

  When the piezoelectric actuator 32 is driven, the potential of any one of the plurality of individual electrodes 43 is switched from the ground potential to a predetermined positive potential. Then, the portion of the piezoelectric layer 42 sandwiched between the individual electrode 43 and the common electrode 45 returns to the state before contraction. On the other hand, an electric field in a direction parallel to the polarization direction is generated in a portion sandwiched between the individual electrode 43 and the common electrode 44 (opposing portion 44a) of the piezoelectric layer 42, and this portion of the piezoelectric layer 42 is orthogonal to the direction of the electric field. Shrink horizontally. Accordingly, the portions of the vibration plate 41, the piezoelectric layer 42, and the insulating layer 46 facing the corresponding pressure chambers 10 are deformed so as to be convex toward the pressure chamber 10 as a whole, and the volume of the pressure chamber 10 is reduced. As a result, the pressure of the ink in the pressure chamber 10 increases, and ink is ejected from the nozzle 15 communicating with the pressure chamber 10. After the ink is ejected, the potential of the individual electrode 43 is switched from a predetermined positive potential to the ground potential, and the piezoelectric actuator 32 is returned to the initial state.

  At this time, in the piezoelectric actuator 32, when the potential of the individual electrode 43 is switched from the ground potential to a predetermined positive potential, the portion sandwiched between the individual electrode 43 and the facing portion 44a of the piezoelectric layer 42 contracts in the horizontal direction. At the same time, the portion of the piezoelectric layer 42 sandwiched between the individual electrode 43 and the common electrode 45 expands from a contracted state to a state before contracting. As a result, the contraction and the expansion of the piezoelectric layer 42 are absorbed by each other, and as a result, the deformation of the portion of the piezoelectric layer 42 facing the pressure chamber 10 is a portion facing the other pressure chamber 10. It is possible to prevent so-called crosstalk, in which the ink ejection characteristics from the nozzle 15 fluctuate due to the propagation to the nozzle.

  Next, a method for manufacturing the piezoelectric actuator 32 will be described. FIG. 7 is a process diagram showing a method for manufacturing the piezoelectric actuator 32. In order to make the drawing easier to understand, in FIG. 7, the illustration of the ink flow path formed in the flow path unit 31 is omitted.

  When manufacturing the piezoelectric actuator 32, first, as shown in FIG. 7A, a plurality of individual electrodes 43 and wirings 47 are formed on the upper surface of the diaphragm 41. Here, the plurality of individual electrodes 43 and wirings 47 are formed by forming a conductive film by printing or the like over almost the entire upper surface of the vibration plate 41, as in the case of forming common electrodes 44 and 45 described later, and then laser processing. Thus, unnecessary portions of the conductive film are removed, and a plurality of individual electrodes 43 and wirings 47 are cut out from the conductive film. Note that the individual electrodes 43 and the wirings 47 may be formed by printing directly with a mask without forming a conductive film over almost the entire upper surface of the vibration plate 41.

  Subsequently, as shown in FIG. 7B, the piezoelectric layer 42 is formed on the upper surface of the vibration plate 41 on which the plurality of individual electrodes 43 and the wirings 47 are formed. Here, examples of the method for forming the piezoelectric layer 42 include an aerosol deposition method (AD method), a sol-gel method, and a sputtering method in which an ultrafine particle material is deposited by colliding at high speed. Alternatively, the piezoelectric layer 42 can be formed by disposing a green sheet of piezoelectric material on the upper surface of the vibration plate 41 and then firing the green sheet.

  The piezoelectric layer 42 is formed on the upper surface of the vibration plate 41 on which the plurality of individual electrodes 43 are arranged, so that the plurality of individual electrodes 43 are arranged on the lower surface (one surface) of the piezoelectric layer 42. Become. That is, in the present embodiment, the above-described step of forming the individual electrode 43 on the upper surface of the vibration plate 41 and the step of forming the piezoelectric layer 42 on the upper surface of the vibration plate 41 on which the individual electrode 43 is formed are combined. This corresponds to the individual electrode forming step according to the present invention.

  Next, as shown in FIG. 7C, a conductive film 51 is formed by printing or the like on almost the entire area of the upper surface of the piezoelectric layer 41 (a region extending continuously across the portions facing the plurality of individual electrodes 43). Form (conductive film forming step).

  Subsequently, as shown in FIG. 7D, unnecessary portions such as a boundary between the common electrode 44 and the common electrode 45 are removed from the conductive film 51 by conducting laser processing. The common electrode 44 is cut out (laser processing step). As a result, the common electrode 44 is formed (common electrode forming step), and the remaining portion of the conductive film 51 from which the common electrode 44 is cut out becomes the common electrode 45.

  Further, when the plurality of facing portions 44a are cut out by the laser processing step, the laser output energy is decreased and the laser scanning speed is decreased. On the other hand, when cutting out the connecting portion 44b and the connecting portion 44c by the laser processing step, the laser output energy is increased and the laser scanning speed is increased as compared with the case of cutting out the plurality of facing portions 44a. In the laser processing for removing the relatively thin conductive film 51, it is preferable to use a laser having a high instantaneous output energy such as a YAG laser.

  Here, in the piezoelectric actuator 32, it is preferable that the drive characteristics of the part corresponding to each pressure chamber 10 are uniform. On the other hand, in the piezoelectric actuator 32, if the sizes and positions of the individual electrodes 43 and the opposed portions 44a and 45a are varied, the drive characteristics are varied. Therefore, it is preferable that the opposing portions 44a and 45a of the individual electrode 43 and the common electrodes 44 and 45 are formed with particularly high accuracy.

  On the other hand, laser processing will be described in more detail. In laser processing, for example, as shown in FIG. 8, a circular region of the conductive film is removed by irradiating the conductive film with a laser having a substantially circular cross section. At the same time, by repeating such laser irradiation while shifting the irradiation position by a predetermined distance (scanning the laser at a predetermined scanning speed), unnecessary portions of the conductive film are sequentially removed. At this time, the larger the laser output intensity, the larger the diameter of the irradiated laser. As an example, for example, when cutting out the opposed portion 44a, if the laser output energy is 1 W, the processing diameter at one degree is 40 mm, and if processing is performed with a shift of 1/3 of the diameter, the frequency is 10 kHz (with a scanning speed of When cutting the connecting portion 44b and the connecting portion 44c at a rate of 133 mm / s), assuming that the output energy of the laser is 2 W, the processing diameter at one degree is 56.6 mm, and processing is performed by shifting 1/3 of the diameter. Then, processing can be performed at a frequency of 14 kHz (scanning speed of 264 mm / s).

  FIG. 8 is a diagram schematically showing a region of the conductive film 51 that is removed by the laser when laser processing is performed in this way. FIG. 8A shows a case where the diameter of the laser is D1. b) shows a case where the diameter of the laser is D2 larger than D1. Note that FIG. 8 shows a case where the laser irradiation position is shifted to the right of the figure by about one third of the laser diameter for each laser irradiation and the laser irradiation is performed seven times. ing.

  When laser processing is performed in this way, as shown in FIG. 8, the positions of both ends in the vertical direction of the regions to be removed by laser processing of the conductive film 51 (regions A1 and A2 surrounded by thick lines in FIG. 8) are , It varies within a certain range (ranges of lengths W1 and W2 shown in FIG. 8). As shown in FIG. 8, W1 <W2, the range of this variation increases as the laser diameter (output energy) increases. In other words, the smaller the laser diameter (output energy), the smaller the variation range, and the electrode can be accurately cut out from the conductive film 51.

  Further, when the laser irradiation position is shifted to the right by about one third of the laser diameter for each laser irradiation, for example, (D1 / 3) <(D2 / 3) in FIG. As the diameter of the laser increases, the laser irradiation position is greatly shifted for each laser irradiation. That is, the higher the laser output energy, the faster the laser scanning speed. As a result, when laser irradiation is performed a certain number of times, the lengths of the regions A1 and A2 removed by the laser of the conductive film 51 in the horizontal direction in the drawing (lengths L1 and L2 shown in FIG. 8) The larger the diameter (output energy) of the laser, the larger (L1 <L2 in FIG. 8). In other words, the time required to remove a certain region of the conductive film can be shortened.

  From the above, in the present embodiment, as described above, when cutting out the connecting portion 44b, the connecting portion 44c, and the wiring 47 that do not require so high accuracy, the individual electrode 43 and the facing portion that require high accuracy are cut out. The laser output energy is increased and the laser scanning speed is made faster than when cutting 44a. If the common electrode 44 is cut out from the conductive film 51, the remaining portion of the conductive film 51 becomes the common electrode 45. Therefore, the facing portion 45a is cut out with the same high accuracy as the facing portion 44a. It is formed with lower accuracy than the facing portion 45a, which is comparable to the connecting portions 44b and 44c.

  Accordingly, the plurality of individual electrodes 43 and the opposed portions 44a and 45a of the common electrodes 44 and 45 can be accurately formed, and laser scanning is performed when the connection portions 44b and 45b, the coupling portion 44c, and the wiring 47 are cut out. The time required for the laser processing step can be shortened by the increase in speed.

  Next, modified examples in which various changes are made to the present embodiment will be described. However, the same components as those in the present embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  In the above-described embodiment, the entire remaining portion of the conductive film 51 from which the common electrode 44 has been cut out is the common electrode 45. However, the present invention is not limited to this. Among these portions, unnecessary portions (a portion of the portion that does not face the individual electrode 43) such as a portion that is largely separated from the portions that become the plurality of facing portions 45a may be removed (Modification 1).

  Here, as a method of removing the unnecessary portion, in the laser processing step, as shown in FIG. 9A, among the remaining portions of the conductive film 51, a portion that becomes the common electrode 45 is used. Then, only the boundary portion with the unnecessary portion is removed, and these two portions are separated. Alternatively, as shown in FIG. 9B, an unnecessary portion that is not used as the common electrode 45 may be completely removed from the remaining portion of the conductive film 51. 9A and 9B show a case where the left and right end portions, the upper right end portion, and the lower left end portion of the remaining portion of the conductive film 51 are unnecessary portions.

  Note that, when removing the unnecessary portion of the conductive film 51, high accuracy is not required. Therefore, by increasing the laser output energy and increasing the laser scanning speed as compared with cutting out the facing portion 44a. The time required for the laser processing step can be shortened as much as possible.

  In the case of FIG. 9A, the time required for the laser processing step can be shortened because the unnecessary portion of the conductive film 51 is left. In addition, since either the common electrodes 44, 45 or the conductive film 51 is disposed in almost the entire upper surface of the piezoelectric layer 42, the strength of the piezoelectric layer 42 becomes uniform, and the piezoelectric layer 42 is heated during heating. Less likely to warp. However, if a potential is applied to an unnecessary portion left of the conductive film 51 for some reason, unnecessary capacitance may be generated or heat may be generated.

  On the other hand, in the case of FIG. 9B, since unnecessary portions are completely removed, problems such as generation of unnecessary capacitance and heat generation as described above hardly occur. However, the time required for the laser processing step is increased by removing unnecessary portions of the conductive film 51. Further, in the piezoelectric layer 42, a difference in strength occurs between the portion where the common electrodes 44 and 45 are disposed and the portion where the conductive film 51 is removed. There is a risk of warping.

  In the above-described embodiment, the common electrode 44 (opposing portion 44 a) faces the substantially central portion of the pressure chamber 10 (individual electrode 43), and the common electrode 45 has both ends in the short direction of the pressure chamber 10. However, the present invention is not limited to this. For example, the common electrode 44 is opposed to both ends of the pressure chamber 10 in the short direction, and the common electrode 45 is opposed to the pressure chamber 10. The common electrodes 44 and 45 may face different portions of the pressure chamber 10 from the above.

  In the above-described embodiment, the two connecting portions 44b are connected by the connecting portion 44c. However, the common electrode 44 is connected to the two connecting portions 44b separately from the wiring 47, for example. The connecting portion 44c may not be provided.

  In the above-described embodiment, the piezoelectric actuator 32 has two types of common electrodes 44, 45 arranged on the upper surface of the piezoelectric layer 42. In order to manufacture such a piezoelectric actuator 32, the common electrode 44 is used. However, the present invention is not limited to this, and the piezoelectric actuator has only one type of common electrode (one of the common electrodes 44 and 45). The remaining portion of the conductive film 51 from which the common electrode is cut out may not be used as an electrode.

  In this case, the piezoelectric actuator is driven only by deformation of a portion sandwiched between these electrodes of the piezoelectric layer 42 caused by a potential difference between the individual electrode 43 and the one type of common electrode.

  In this case, the remaining portion of the conductive film 51 from which the common electrode is cut out may be left or removed. When the remaining portion of the conductive film 51 is left, either the common electrode or the remaining portion of the conductive film 51 is disposed over almost the entire upper surface of the piezoelectric layer 42. The strength of 42 becomes uniform, and the piezoelectric layer 42 hardly warps during heating.

  However, if a potential is applied to the remaining portion of the conductive film 51 for some reason, the portion of the piezoelectric layer 42 sandwiched between them is deformed due to a potential difference between the individual electrode 43 and the remaining portion of the conductive film 51. As a result, the drive characteristics of the piezoelectric actuator may vary. Alternatively, there is a possibility that unnecessary capacitance is generated or heat is generated by applying a potential to the remaining portion of the conductive film 51.

  On the other hand, when the remaining portion of the conductive film 51 is removed, problems such as fluctuations in driving characteristics of the piezoelectric actuator, generation of unnecessary capacitance, and heat generation as described above are unlikely to occur. However, the time required for the laser processing step is increased by removing unnecessary portions of the conductive film 51. Further, in the piezoelectric layer 42, a difference in strength occurs between the portion where the common electrode is disposed and the portion where the conductive film 51 is removed, and thus the piezoelectric layer 42 is warped during heating or the like. There is a risk of it.

  However, the remaining portions of the conductive film 51 are not limited to removing all of them. If at least a portion facing the pressure chamber 10 is removed, the individual electrodes 43 of the piezoelectric layer 42 and the conductive film 51 described above are removed. It is possible to prevent deformation of the portion sandwiched between the remaining portions.

  Further, when removing the portion of the conductive film 51 that is not an electrode, so high accuracy is not required, so by increasing the laser output energy and increasing the laser scanning speed than when cutting the facing portion 44a, The time required for the laser processing step can be shortened as much as possible.

  In this case, since only one type of common electrode is disposed on the upper surface of the piezoelectric layer 42, the insulating layer 46 for preventing conduction between the two types of common electrodes is not provided. Also good.

  In the above-described embodiment, the remaining portion of the conductive film 51 from which the common electrode 44 is cut out is the common electrode 45. However, the present invention is not limited to this, and the piezoelectric actuator has one type of common electrode (the common electrode 44, 45), and the remaining portion of the conductive film 51 from which the common electrode is cut out may be an electrode different from the common electrode.

  For example, the remaining portion of the conductive film 51 from which the common electrode has been cut can be used as a crack detection electrode for detecting cracks occurring in the piezoelectric layer 42 in the manufacturing process of the piezoelectric actuator. By measuring the electrical resistance between the crack detection electrode and the individual electrode, it is possible to detect whether or not a crack has occurred in the piezoelectric layer 42. Further, in this case, since the crack detection electrode is formed, the strength of the piezoelectric layer 42 becomes uniform, and the piezoelectric layer 42 hardly warps during heating.

  In the above-described embodiment, the common electrode 44 is always held at the ground potential, and the common electrode 45 is always held at the predetermined positive potential. However, the present invention is not limited to this, and the traffic electrode 44 is always set at the predetermined potential. The common electrode 45 may always be held at the ground potential.

  In the above-described embodiment, the piezoelectric layer 42 is formed on the upper surface of the vibration plate 41 and then the common electrodes 44 and 45 are formed on the upper surface of the piezoelectric layer 42. However, the present invention is not limited to this. The piezoelectric layer 42 on which 44 and 45 are disposed may be bonded to the upper surface of the vibration plate 41.

  Here, the piezoelectric layer 42 on which the common electrodes 44 and 45 are disposed is formed by, for example, firing the green sheet after forming the common electrodes 44 and 45 on the upper surface of the green sheet before firing, or firing the green sheet. It can be produced by forming the common electrodes 44 and 45 on the upper surface of the resulting piezoelectric layer 42. Even in this case, the method of forming the common electrodes 44 and 45 is the same as that in the above-described embodiment.

  Further, in the above-described embodiment, a plurality of individual electrodes 43 are formed on the upper surface of the vibration plate 41 and then a piezoelectric layer 42 is formed on the upper surface of the vibration plate 41, whereby a plurality of individual electrodes are formed on the lower surface of the piezoelectric layer 42. Although the electrodes 43 are formed, the present invention is not limited to this, and a plurality of individual electrodes 43 are directly formed on the lower surface of the piezoelectric layer 42 (individual electrode forming step), and then the piezoelectric in which the plurality of individual electrodes 43 are formed. The layer 42 may be bonded to the vibration plate 41.

  In addition, the piezoelectric layer 42 on which the plurality of individual electrodes 43 are formed is formed by, for example, forming the plurality of individual electrodes 43 in advance on the lower surface of the green sheet of piezoelectric material and then firing the green sheet, It can be produced by forming a plurality of individual electrodes 43 on the lower surface of the piezoelectric layer 42 that can be fired.

  In the above-described embodiment, the plurality of individual electrodes 43 are disposed on the lower surface of the piezoelectric layer 42 and the common electrodes 44 and 45 are disposed on the upper surface of the piezoelectric layer 42. The plurality of individual electrodes 43 may be disposed on the upper surface of the piezoelectric layer 42, and the common electrodes 44 and 45 may be disposed on the lower surface of the piezoelectric layer 42.

  In the above, the present invention has been applied to the manufacture of a piezoelectric actuator used in an inkjet head of a so-called serial printer that ejects ink from a nozzle while reciprocating in the scanning direction. It is also possible to apply the present invention to the manufacture of a so-called line head that extends over the entire length in the width direction and is fixed to the printer body. Furthermore, the present invention can also be applied to the manufacture of piezoelectric actuators used in devices other than inkjet heads.

32 Piezoelectric actuator 42 Piezoelectric layer 43 Individual electrode 44 Common electrode 44a Opposing part 44b Connection part 44c Connection part 45 Common electrode

Claims (3)

A piezoelectric layer;
A plurality of individual electrodes disposed on one surface of the piezoelectric layer;
A first common electrode disposed on a surface opposite to the plurality of individual electrodes of the piezoelectric layer,
The first common electrode is
A plurality of facing portions facing the plurality of individual electrodes;
A method of manufacturing a piezoelectric actuator having a connecting portion that connects the plurality of facing portions to each other,
An individual electrode forming step of forming the plurality of individual electrodes on the one surface of the piezoelectric layer;
A common electrode forming step of forming the first common electrode on a surface of the piezoelectric layer opposite to the plurality of individual electrodes;
The common electrode forming step includes
Forming a conductive film continuously extending across a portion facing the plurality of individual electrodes on a surface opposite to the plurality of individual electrodes of the piezoelectric layer;
A laser processing step of cutting out the first common electrode from the conductive film by laser processing,
In the laser processing step, when cutting out the connecting portion, the laser output energy is increased and the laser scanning speed is increased as compared with cutting out the plurality of facing portions. Method. The plurality of facing portions are opposed to a part of the corresponding individual electrode,
The piezoelectric actuator further includes a second common electrode disposed on a surface of the piezoelectric layer opposite to the plurality of individual electrodes and facing a portion different from the portion of the plurality of individual electrodes. Because
2. The portion of the conductive film excluding the first common electrode becomes the second common electrode by cutting out the first common electrode from the conductive film in the laser processing step. A manufacturing method of the piezoelectric actuator described in 1.   The said laser processing process WHEREIN: Furthermore, a part of part which does not oppose these individual electrodes among the parts except the said 1st common electrode of the said electrically conductive film is removed. A method for manufacturing a piezoelectric actuator.

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