JP5096659B2 - Piezoelectric actuator and print head - Google Patents

Description

  The present invention relates to a laminated piezoelectric material, a piezoelectric actuator, and a print head. More specifically, for example, a piezoelectric sensor such as an acceleration sensor, a knocking sensor, and an AE sensor, a fuel injection injector, a print head for an inkjet printer, a piezoelectric resonator, an oscillator, Laminate piezoelectric material suitable for ultrasonic motors, ultrasonic vibrators, filters, etc., piezoelectric actuators using spreading vibration, stretching vibration, thickness vibration, and printing mounted on inkjet printers used for printing characters and images Regarding the head.

  Conventionally, products using piezoelectric ceramics include, for example, piezoelectric actuators, filters, piezoelectric resonators (including oscillators), ultrasonic vibrators, ultrasonic motors, and piezoelectric sensors. Among them, the piezoelectric actuator has a very high response speed to the electric signal on the order of microseconds, so that it can be used as a piezoelectric actuator for positioning an XY stage of a semiconductor manufacturing apparatus, a piezoelectric actuator used for a print head of an ink jet printer, or the like. Applied. In particular, due to the recent increase in speed and cost of color printers, there is an increasing demand for use in ink ejection actuators such as inkjet printers.

  In response to this requirement, for example, Patent Document 1 discloses that an internal electrode is formed by applying and printing an electrode paste on the surface of a green sheet mainly composed of piezoelectric ceramics and having a thickness of several hundreds μm. After lamination, the binder is removed to remove the binder contained in the green sheet and internal electrode, and then sintered to obtain a fired body. Further, an insulator, external electrode, and lead wire are formed on the fired body. A piezoelectric actuator is disclosed. An Ag—Pd alloy is used as the internal electrode material in this piezoelectric actuator.

  Such a piezoelectric actuator has a feature that a multilayer laminate of a piezoelectric ceramic layer and internal electrodes can be easily and inexpensively manufactured by simultaneous firing, and is suitable for a print head for an inkjet printer, an XY stage positioning device, and the like. Is used.

  However, in the conventional piezoelectric actuator as described above, the adhesion strength between the piezoelectric ceramic layer and the internal electrode is not always sufficient, and when the piezoelectric actuator is used, for example, a speed of 16000 times per second (16 kHz) by applying a driving voltage. Therefore, there is a problem that delamination occurs due to stress applied between the piezoelectric ceramic layers and between the piezoelectric ceramic layers and the internal electrodes.

  Therefore, Patent Document 2 discloses that two piezoelectric ceramic layers facing each other through the internal electrode are added by adding substantially the same ceramic powder (co-material) as the piezoelectric ceramic layer to the conductive paste as the internal electrode material. It has been proposed to increase the interlayer adhesion strength of the laminate by connecting them.

  On the other hand, high-precision printers that have made remarkable progress in recent years tend to require a large amount of displacement. However, in the piezoelectric actuator described in Patent Document 1, the amount of displacement is limited due to the large thickness and overall thickness of the piezoelectric ceramic layer. . Therefore, in order to increase the displacement amount of the piezoelectric actuator, the total thickness tends to be reduced in recent years. In particular, the total thickness needs to be 100 μm or less in order to cope with a high-speed printer.

Moreover, in the method described in Patent Document 2, sufficient interlayer strength cannot always be obtained under severe use conditions that cause displacement as in the case of a piezoelectric actuator, and in particular, a thin layer having an overall thickness of 100 μm or less as described above. In this piezoelectric actuator, since the thickness of the piezoelectric ceramic layer is thin, deformation due to firing becomes remarkable. In particular, it is extremely difficult to suppress deformation in a piezoelectric laminate in which each piezoelectric ceramic layer has a thickness of 25 μm or less. Due to the delamination caused by such deformation, the variation of the displacement amount becomes large. In particular, in a piezoelectric laminate having a plurality of piezoelectric elements on the same substrate, it is difficult to control the displacement as an actuator.
JP 11-121820 A JP-A-10-172855

  An object of the present invention is to provide a laminated piezoelectric body, a piezoelectric actuator, and a print head including the same, which can suppress delamination even when the total thickness is 100 μm or less, obtain excellent piezoelectric characteristics, and easily control displacement. It is to be.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have found that most of the common material in the Ag—Pd alloy constituting the electrode layer of the laminated piezoelectric body is 3 of the grain boundary of the Ag—Pd alloy. A new fact that delamination between the piezoelectric ceramic layer and the electrode can be suppressed by the presence of emphasis has been found, and the present invention has been completed.

That is, pressure electrostatic actuator and the print head of the present invention comprises the following arrangement.
(1) A piezoelectric actuator having a thickness of 100 μm or less, comprising a laminate in which a plurality of piezoelectric ceramic layers are laminated, and an electrode layer made of an Ag—Pd alloy provided on the surface and / or inside of the laminate, The piezoelectric ceramic layer is made of lead zirconate titanate, and the electrode layer contains a common material made of ceramics, and 90% or more of the common material is at the triple point of the grain boundary of the Ag-Pd alloy. A piezoelectric actuator characterized in that it exists.
(2) The piezoelectric actuator according to (1), wherein a ratio (M / T) of an average grain size (M) of the Ag—Pd alloy to an average grain size (T) of the common material is 2.5 or more.
(3) The piezoelectric actuator according to (1) or (2), wherein the Ag—Pd alloy contains 70% by volume or more of Ag.
(4) The piezoelectric actuator according to any one of (1) to (3), wherein the electrode layer contains 50 to 90% by volume of the Ag—Pd alloy and 10 to 50% by volume of the common material.
(5) The piezoelectric actuator according to any one of (1) to (4), wherein the ceramic constituting the common material has substantially the same composition as the piezoelectric ceramic constituting the piezoelectric ceramic layer.
(6) At least one electrode layer is provided inside the laminate, and two piezoelectric ceramic layers facing each other through the electrode layer are connected by the common material in the electrode layer (1) The piezoelectric actuator according to any one of to (5).
(7) The piezoelectric actuator according to any one of (1) to (6), wherein the piezoelectric ceramic constituting the piezoelectric ceramic layer contains Pb.
(8) The piezoelectric actuator according to any one of (1) to (7), wherein the piezoelectric ceramic layer has a thickness in a range of 1 to 50 μm.
(9) The value obtained by dividing the standard deviation σ of the mechanical quality factor (Qm) by the average value of the mechanical quality factor (Qm) and multiplying by 100 is 10 or less. Piezoelectric actuator .
(10) The piezoelectric actuator according to any one of (1) to (9) is mounted on a flow path member in which a plurality of ink flow paths having ink discharge holes are arranged. Print head.

According to the piezoelectric actuator described in the above (1), by causing 90% or more of the common material to exist at the triple point of the grain boundary of the Ag—Pd alloy, generation of pores (holes) in the electrode is suppressed, Since delamination between the piezoelectric ceramic layer and the electrode can be suppressed, a large displacement can be obtained by increasing the piezoelectric constant (d31) representing the piezoelectric characteristics, and a mechanical quality factor (Qm) representing the elastic characteristics. ) Can be suppressed. As a result, a piezoelectric actuator having excellent piezoelectric characteristics and easy displacement control can be provided.

  As described in (2) above, when the ratio (M / T) of the average grain size (M) of the Ag—Pd alloy to the average grain size (T) of the common material is 2.5 or more, the common material This increases the probability that there is a triple point at the grain boundary. On the other hand, if the ratio (M / T) is outside the above range, that is, if the average particle size of the common material is large, the common material may not easily exist at the triple point of the grain boundary.

  As described in (3) above, when the Ag—Pd alloy in the electrode layer contains 70% by volume or more of Ag, the wettability between the electrode and the piezoelectric ceramic layer is improved, and the adhesion strength between them can be increased. .

  As described in (4) above, when the content ratio of the Ag—Pd alloy and the common material in the electrode layer is in the above range, the probability that the common material exists at the triple point of the grain boundary is further improved, The occurrence of pores can be more reliably suppressed.

  As described in (5) above, when the ceramic particles have substantially the same composition as the piezoelectric ceramic, the adhesion strength between the piezoelectric ceramic layer and the electrode layer can be further improved.

  As described in (6) above, when the two piezoelectric ceramic layers facing each other through the electrode layer are connected by the common material in the electrode layer, the interlayer strength of the laminate can be further improved.

  As described in (7) above, when the piezoelectric ceramic constituting the piezoelectric ceramic layer contains Pb, wettability with the Ag—Pd alloy constituting the electrode layer can be improved.

  As described in (8) above, when the thickness of the piezoelectric ceramic layer (the thickness of one piezoelectric ceramic layer) is in the range of 1 to 50 μm, a larger displacement can be obtained.

According to the above piezoelectric actuator , as described in (9) above, the value obtained by dividing the standard deviation σ of Qm by the average value of Qm and multiplying it by 100 can be reduced to 10 or less. As a result, when a plurality of actuators are configured on one substrate, displacement control can be easily performed.

Printhead before Symbol (10) described, reliable, has excellent piezoelectric properties.

  Hereinafter, a laminated piezoelectric material according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the laminated piezoelectric body of the present embodiment. As shown in FIG. 1, this laminated piezoelectric body includes a laminated body in which two piezoelectric ceramic layers 1 and 1 are laminated, and electrode layers provided on the surface and inside of the laminated body.

  This electrode layer includes an internal electrode 2 existing inside the multilayer body and a plurality of surface electrodes 3 present on the surface of the multilayer body. A plurality of piezoelectric elements are formed by the surface electrode 3, the internal electrode 2, and the piezoelectric ceramic layer 1 disposed between these electrodes. This laminated piezoelectric body can be suitably used as a piezoelectric actuator by connecting a lead wire to the surface electrode 3 and making an electrical connection with the outside.

  It is important that the total thickness T of the laminated piezoelectric material is 100 μm or less, particularly 85 μm or less, and more preferably 70 μm or less. Thereby, the displacement of each piezoelectric element can be increased, and high-efficiency driving can be realized at a low voltage. Moreover, the thickness t of each piezoelectric ceramic layer 1 is preferably 1 to 50 μm, more preferably 3 to 22 μm, still more preferably 5 to 19 μm, and further preferably 7 to 16 μm. The point of increasing the displacement is to prevent and maintain the self-shape.

  The internal electrode 2 contains an Ag—Pd alloy as a main component and a co-material made of ceramics. The Ag—Pd alloy preferably contains Ag in an amount of 70% by volume or more, more preferably 70 to 99.9% by volume of Ag and 0.1 to 30% by volume of palladium. The electrode having such a composition has high wettability with the piezoelectric ceramic constituting the piezoelectric ceramic layer 1 and can improve the adhesion strength. In particular, an Ag—Pd alloy containing 90% by volume or more of Ag has a melting point as low as 1000 ° C. or less, and is effective in terms of wettability and movement of the common material to the grain boundary.

  The internal electrode 2 contains a common material made of ceramics. The content ratio of the Ag-Pd alloy and the common material is in the range of 50 to 90% by volume of the Ag-Pd alloy and 10 to 50% by volume of the common material, preferably 70 to 80% by volume of the Ag-Pd alloy, and 20 to 30% of the common material. % Should be good. Thereby, the adhesion strength between the internal electrode 2 and the piezoelectric ceramic layer 1 can be further increased, the residual stress can be reduced, and the piezoelectric characteristics can be further stabilized. The internal electrode 2 has a thickness of 0.5 to 5 μm, preferably 1 to 3 μm.

  As the co-material, various ceramics can be used, but preferably a piezoelectric ceramic having substantially the same composition as the piezoelectric ceramic layer 1 is preferable. Accordingly, the reaction between the common material and the piezoelectric ceramic layer 1 or the diffusion of the common material into the piezoelectric ceramic layer 1 is likely to occur.

  FIG. 2 is a partially enlarged plan view in which the surface of the internal electrode 2 is enlarged. As shown in FIG. 2, the internal electrode 2 is composed of an Ag—Pd alloy 30 and a common material 4 existing at the grain boundary of the alloy 30. In the internal electrode 2 in the present invention, 90% or more, preferably 93% or more of the co-material 4 is preferably present at the triple point of the grain boundary of the Ag—Pd alloy 30. Thereby, sintering of an internal electrode can be suppressed and the generation amount of pores in the internal electrode 2 can be reduced, and as a result, interlayer strength can be increased. Furthermore, since the ratio (M / T) of the average grain size (M) of the Ag—Pd alloy to the average grain size (T) of the common material is 2.5 or more, the common material can easily exist at the grain boundary. Become.

  Further, it is preferable that the two piezoelectric ceramic layers 1 and 1 facing each other through the internal electrode 2 are connected by a common material (not shown). Thereby, sufficient interlayer strength as a piezoelectric actuator can be obtained.

  Any material can be used as the material of the surface electrode 3 as long as it has conductivity. Specific examples include Au, Ag, Pd, Pt, Cu, Al, and alloys thereof. The same Ag—Pd alloy as 2 may be used. The thickness of the surface electrode 3 is preferably thin in order to suppress restraint during displacement, and is preferably 1 μm or less, more preferably 0.1 to 0.8 μm.

  The piezoelectric ceramic constituting the piezoelectric ceramic layer 1 in the present invention may be any ceramic that exhibits piezoelectricity, and includes, for example, a Bi layer compound, a tungsten bronze structure material, a perovskite structure compound of an Nb acid alkali compound, and Pb. Examples include perovskite structure compounds containing lead zirconate titanate (PZT) and lead titanate, among which lead zirconate titanate and lead titanate containing Pb enhance wettability with the electrode. It is suitable at the point which raises adhesive strength with.

  That is, it is a crystal containing Pb as an A-site constituent element and Zr and / or Ti as a B-site constituent element. In particular, a lead zirconate titanate-based compound has a higher d constant. This is preferable for obtaining a stable piezoelectric sintered body.

Moreover, it is preferable that the piezoelectric ceramic layer 1 contains at least 1 sort (s) among Sr, Ba, Ni, Sb, Nb, Zn, and Te. As a result, a more stable piezoelectric sintered body can be obtained. For example, Pb (Zn _1/3 Sb _2/3 ) O ₃ and Pb (Ni _1/2 Te _1/2 ) O ₃ are solidified as subcomponents. What melt | dissolves can be illustrated.

In particular, it is desirable to further contain an alkaline earth element as the A site constituent element. As the alkaline earth element, Ba and Sr are particularly preferable in that a high displacement can be obtained, and the inclusion of 0.02 to 0.08 mol of Ba and 0.02 to 0.12 mol of Sr is particularly mainly tetragonal composition. It is advantageous to obtain a large displacement in the case of the following composition. For _{example, Pb 1-xy Sr x Ba} y (Zn 1/3 Sb 2/3) a (Ni 1/2 Te 1/2) b Zr 1-abc Ti c O 3 + αwt% Pb 1/2 NbO 3 (0 ≤ x ≤ 0.14, 0 ≤ y ≤ 0.14, 0.05 ≤ a ≤ 0.1, 0.002 ≤ b ≤ 0.01, 0.44 ≤ c ≤ 0.50, α = 0.1 in which it expresses by 1.0).

Next, the manufacturing method of the laminated piezoelectric material of the present invention will be described by taking as an example the case of using PZT as the piezoelectric ceramic.
First, as a raw material, a PZT powder having a purity of 99% and an average particle size of 1 μm or less is prepared as a piezoelectric ceramic powder. An appropriate organic binder is added to the piezoelectric ceramic powder and formed into a tape shape to produce the required number of green sheets. Next, an Ag—Pd paste containing the above composition Ag—Pd alloy and co-material is applied to a part of the produced green sheet to form an internal electrode and cut into a desired shape. Next, the green sheets are laminated, debindered at about 400 ° C., and then fired. After firing, a desired electrode can be formed on the surface and polarized to obtain a laminated piezoelectric material.

  By combining the internal electrode 2 made of such an Ag—Pd alloy and the piezoelectric ceramic layer 1, the elastic stability of the laminated piezoelectric body can be obtained, and as a result, the mechanical quality factor (Qm) of the laminated piezoelectric body varies. Is suppressed. In order to suppress the displacement variation within 10%, the value obtained by dividing the standard deviation σ of the mechanical quality factor (Qm) of the laminated piezoelectric body by the average value and multiplying by 100 is preferably 10 or less. As a result, it is possible to obtain a laminated piezoelectric body in which displacement variation is further suppressed and displacement control is easy.

  In addition, when producing a laminated body by laminating green sheets, a constraining sheet made of a piezoelectric ceramic and an organic composition having substantially the same composition as the green sheet is disposed on both sides or one side of the laminated body, and pressure adhesion It is preferable to carry out. By suppressing the shrinkage of the outer green sheet with the restraint sheet in this way, it is possible to expect the effect of reducing the warpage of the laminate, and it is possible to reduce the stress when adhering to the support member.

  Next, a piezoelectric actuator according to an embodiment of the present invention and an ink jet print head including the same will be described. FIG. 3A is a schematic cross-sectional view showing a print head including the piezoelectric actuator according to the present embodiment, and FIG. 3B is a plan view thereof. This piezoelectric actuator includes a plurality of piezoelectric elements on one substrate, and can be suitably used for an ink jet print head used in a recording apparatus using an ink jet system.

  As shown in FIG. 3A, the actuator 15 of this embodiment includes piezoelectric ceramic layers 11a and 11b, a common electrode 12 disposed between the piezoelectric ceramic layers 11a and 11b, and a piezoelectric ceramic layer 11b. A plurality of individual electrodes 13 formed in a lattice shape on the surface, and includes a common electrode 12, a plurality of individual electrodes 13, and a piezoelectric ceramic layer 11b positioned between the individual electrodes 13 and the common electrode 12. A plurality of piezoelectric elements 14 are formed. Each individual electrode 13 is independently connected to an external electronic control circuit, and when a voltage is applied between the electrodes, the common electrode 12 to which the voltage is applied and the piezoelectric ceramic layer sandwiched between the individual electrodes 13 11b is displaced. The piezoelectric ceramic layer 11b plays the role of a diaphragm.

  As the piezoelectric ceramic layers 11a and 11b, the same material as that of the piezoelectric ceramic layer 1 described above can be used. The common electrode 12 and the individual electrode 13 can be made of the same material as the internal electrode 2 and the surface electrode 3 described above. The piezoelectric actuator 15 is manufactured in the same manner as the laminated piezoelectric material.

  In the print head according to the present embodiment, the piezoelectric actuator 15 is arranged on the flow path member 16 in which a plurality of ink flow paths 16a having ink discharge holes 16c are arranged so that the positions of the ink flow paths 16a and the individual electrodes 13 are aligned. It is attached. Each ink flow path 16a is partitioned by a partition wall 16b.

  The flow path member 16 is obtained by a rolling method or the like, and the ink discharge holes 16c and the ink flow path 16a are provided by being processed into a predetermined shape by etching. The flow path member 16 is preferably formed of at least one selected from the group consisting of Fe—Cr, Fe—Ni, and WC—TiC, and is made of a material particularly excellent in corrosion resistance to ink. Desirably, the Fe-Cr system is more preferable.

  The piezoelectric actuator 15 and the flow path member 16 can be laminated and bonded via an adhesive layer, for example. A well-known adhesive layer can be used as the adhesive layer, but in order not to affect the piezoelectric actuator 11 and the flow path member 13, an epoxy resin, phenol resin, polyphenylene ether having a thermosetting temperature of 100 to 250 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group of resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric actuator 15 and the flow path member 16 can be heat-bonded, whereby a print head can be obtained. When a voltage is applied between the common electrode 12 and the predetermined individual electrode 13 by an external drive circuit, the piezoelectric ceramic layer 11b immediately below the individual electrode 13 to which the voltage is applied is displaced, and the ink flow path 16a is displaced. The ink is pressurized and ink droplets are ejected from the ink ejection holes 16c.

  By adopting such a configuration, ink droplets can be ejected at high speed with high accuracy, and a print head suitable for high-speed printing can be provided. Further, by configuring a printer (printing machine) including the print head of the present invention, an ink tank containing ink, an ink supply unit that supplies ink from the ink tank to the print head, and a paper feeding device. High-speed and high-precision printing can be realized.

  As mentioned above, although one Embodiment of this invention was shown, it cannot be overemphasized that this invention can be applied not only to the embodiment mentioned above but what was changed and improved in the range which does not deviate from the summary of this invention. For example, in the above-described embodiment, the case where the laminated piezoelectric body is applied to a piezoelectric actuator and an inkjet print head has been described. However, the laminated piezoelectric body of the present invention may be a piezoelectric sensor such as an acceleration sensor, a knocking sensor, or an AE sensor, The present invention can also be applied to fuel injectors, piezoelectric resonators, oscillators, ultrasonic motors, ultrasonic vibrators, filters, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to a following example.

As the raw material powder for the piezoelectric ceramic layer, high-purity Pb ₂ O ₃ , ZrO ₂ , TiO ₂ , BaCO ₃ , ZnO, SrCO ₃ , Sb ₂ O ₃ , NiO, TeO ₂ are used as the raw material powder, and the sintered body is Pb _{1. -xy Sr x Ba y (Zr 1/3} Sb 2/3) a (Ni 1/2 Te 1/2) b Zr 1-abc Ti c O 3 (x = 0.04, y = 0.02, a = 0.075, b = 0.005, c = 0.4.2), and a predetermined amount was weighed. In addition, PbTiO ₃ and BaTiO ₃ were similarly prepared as ceramic layers.

  The above prepared powder was wet mixed by a ball mill for 20 hours, and then this mixture was dehydrated and dried. Thereafter, the mixture was calcined at 900 ° C. for 3 hours, and the obtained calcined product was wet pulverized again with a ball mill. Next, an organic binder, water, a dispersing agent and a plasticizer are mixed into the pulverized product to prepare a slurry, and the thickness after firing is determined by a roll coater method generally used for forming a thin green sheet. A green sheet in which the shrinkage rate was considered in advance so as to have the size shown in Table 1 was produced.

  Also, an electrode paste for an internal electrode made of an Ag—Pd alloy was prepared in the composition shown in Table 1, and piezoelectric ceramic powder was added as a co-material so as to have the composition shown in Table 1. The piezoelectric ceramic powder used as the co-material had an average particle size of 1.0 μm or less. These were separately mixed with a vehicle containing an organic binder and an organic solvent, and then both were sufficiently kneaded to prepare an internal electrode paste.

  The obtained internal electrode paste was printed on the surface of the green sheet with a thickness of 4 μm to form an internal electrode. Further, one green sheet on which the internal electrode paste was not printed was laminated between two sheets of green sheets with the surface on which the internal electrodes were printed facing upward, and pressed to obtain a laminated molded body. After degreasing the laminated molded body, it was sintered in an atmosphere of 940 to 1000 ° C. and oxygen of 99% or more for 2 to 4 hours to produce a sintered body. A plurality of surface electrodes 3 were formed on one surface of the sintered body. The surface electrode 3 was formed by applying Au paste by screen printing to form 600 points per substrate. This was formed by baking at 600 to 800 ° C. in the air. Thus, a piezoelectric actuator 25 having piezoelectric ceramic layers 21a and 21b, a common electrode 22 and individual electrodes 23 as shown in FIG. 4 and having a plurality of piezoelectric elements formed was obtained. Lead wires were connected to the individual electrodes 23 of the piezoelectric actuator 25 with solder.

  Next, a d constant, a mechanical quality factor (Qm) indicating the piezoelectric characteristics of the piezoelectric actuator, and a method for evaluating the adhesion strength will be described. The above piezoelectric actuator is cut into 10 cm × 10 cm, and only one side thereof is polished to leave only one piezoelectric ceramic layer. Then, electrodes were formed on both main surfaces of the porcelain by Au vapor deposition. After that, it was cut by dicing into 12 mm in the long side direction and 3 mm in the short side direction, and polarized by applying a DC voltage of 3 kv / mm in the thickness direction in silicon oil for 5 minutes. This element was measured for resonance frequency, anti-resonance frequency, resonance resistance, anti-resonance resistance, and capacitance with an impedance analyzer (Agilent Technology 4194A), and Qm and d31 were calculated from the density measured by the Archimedes method. Then, an average value of Qm and a standard deviation (σ) of variation were obtained, and [{(σ of Qm) / (average value of Qm)} × 100] was used as an index of variation. In this example, a case where [{(σ of Qm) / (average value of Qm)} × 100] was 10 or less was regarded as a non-defective product.

  As shown in FIG. 5, the displacement of the piezoelectric actuator was measured using a sample obtained by bonding the piezoelectric actuator 25 obtained above to a support 26 having a groove 26a and a partition wall 26b. The actuator was irradiated with a laser beam from the groove 26a side of this sample, and the displacement amount at the center and the peripheral portion of the groove 26a was measured with a laser Doppler displacement meter, and the average value and variation of the displacement amount were calculated. The variation of the displacement amount was the difference between the maximum displacement amount and the minimum displacement amount (maximum displacement amount−minimum displacement amount), and the case where this variation was 10 nm or less was regarded as a non-defective product.

  For adhesion strength, the piezoelectric actuator 25 manufactured under the above conditions was bonded to a SUS316 plate at 120 ° C. using an epoxy adhesive, and then the piezoelectric actuator 25 was subjected to a Vickers indentation with a load of 1.0 kgf (9.8 N). For 5 seconds, the peeling state of the piezoelectric ceramic layers 21a and 21b and the common electrode layer 22 was observed. Of the 20 indentations per sample, one where one or more peels occurred was judged as insufficient interlayer strength. The results are shown in Table 1.

  The connection state between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b by the common material in the common electrode 22 was performed as follows. That is, the cross section of the piezoelectric actuator 25 was mirror-polished and then observed with a scanning electron microscope (SEM) at 2000 times magnification. The number of connecting portions in the 150 μm width of the common electrode was counted, and those having 10 or more connecting portions were regarded as non-defective products. Similarly, a non-defective product having 5 or less pores was used.

Observation of the electrode surface was performed as follows. That is, after the individual electrode 23 and the common electrode 22 are immersed in water, a voltage of 40 V is applied between the two electrodes, whereby the common electrode 22 and the piezoelectric ceramic layers 21a and 21b are separated by an electrochemical reaction. The peeled piezoelectric ceramic layers 21a and 21b were removed, and the surface of the remaining common electrode was observed with an SEM. Each component on the surface of the common electrode was subjected to component analysis, and it was determined that common material was present in the portion where Pb was detected. Based on the following formula {(number of co-materials present at the triple point / total number of co-materials) × 100}, an evaluation of what percentage of the common material is present at the triple point of the Ag—Pd alloy is performed. I went. Each evaluation result is shown in Table 1.

  From Table 1, Sample No. which is within the scope of the present invention. 3-14 and no. Nos. 16 to 19 were laminated piezoelectric bodies having a displacement variation range of 10 nm or less, no delamination, and easy displacement control.

  On the other hand, Sample No. outside the scope of the present invention in which Ag is less than 70% by volume and a large amount of common material is present in the grains. In Nos. 1 and 2, the displacement variation range was larger than 10 nm, and delamination occurred. Sample No. 1 having a piezoelectric ceramic layer thickness of 100 μm was used. No. 15 had a small displacement of 50 nm.

It is a schematic sectional drawing which shows the laminated piezoelectric material of this invention. FIG. 2 is a schematic plan view schematically showing a surface of an internal electrode in the multilayer piezoelectric body of FIG. 1. It is a schematic sectional drawing which shows the printing head provided with the piezoelectric actuator of this invention. It is a schematic sectional drawing which shows the piezoelectric actuator produced in the Example. FIG. 5 is a schematic cross-sectional view showing a structure for evaluating the characteristics of the piezoelectric actuator shown in FIG. 4 in the example.

Explanation of symbols

l, 11a, 11b, 21a, 22b Piezoelectric ceramic layer 2 Internal electrode 3 Surface electrode 12 Common electrode 13 Individual electrode 14 Piezoelectric element 15 Actuator 16 Channel member 16a Ink channel 16b Partition 16c Ink ejection hole

Claims (10)

A piezoelectric actuator having a thickness of 100 μm or less, comprising a laminate in which a plurality of piezoelectric ceramic layers are laminated, and an electrode layer made of an Ag—Pd alloy provided on the surface and / or inside of the laminate,
The piezoelectric ceramic layer is composed of lead zirconate titanate,
The piezoelectric actuator characterized in that the electrode layer contains a common material made of ceramics, and 90% or more of the common material exists at the triple point of the grain boundary of the Ag-Pd alloy. 2. The piezoelectric actuator according to claim 1, wherein a ratio (M / T) of an average grain size (M) of the Ag—Pd alloy and an average grain size (T) of the common material is 2.5 or more. The piezoelectric actuator according to claim 1 or 2, wherein the Ag-Pd alloy contains 70% by volume or more of Ag. 4. The piezoelectric actuator according to claim 1, wherein the electrode layer contains 50 to 90% by volume of the Ag—Pd alloy and 10 to 50% by volume of the common material. The piezoelectric actuator according to claim 1, wherein the ceramic constituting the common material has substantially the same composition as the piezoelectric ceramic constituting the piezoelectric ceramic layer. The at least 1 layer of said electrode layer is provided in the inside of the said laminated body, The two piezoelectric ceramic layers which oppose through this electrode layer are connected by the said co-material in an electrode layer. Any one of the piezoelectric actuators . The piezoelectric actuator according to claim 1, wherein the piezoelectric ceramic constituting the piezoelectric ceramic layer contains Pb. The piezoelectric actuator according to claim 1, wherein the piezoelectric ceramic layer has a thickness in a range of 1 to 50 μm. The piezoelectric actuator according to claim 1, wherein a value obtained by dividing the standard deviation σ of the mechanical quality factor (Qm) by the average value of the mechanical quality factor (Qm) and multiplying by 100 is 10 or less. The piezoelectric actuator according to any one of claims 1 to 9, the print head is characterized in that a plurality of ink flow paths is mounted on the channel members arranged with the ink discharge hole.

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