JP2007335489A - Piezoelectric thin film element, thin film actuator, ink jet head, and ink jet recording apparatus - Google Patents

Abstract

A piezoelectric thin film element having good piezoelectric characteristics even when various internal stresses are present during the formation of the thin film, a thin film actuator and an ink jet head using the piezoelectric thin film element, and an ink jet recording provided with the ink jet head as a printing means To get the equipment.
A piezoelectric layer 14 formed of an oxide containing Pb having a perovskite crystal structure, and electrode layers 13 and 15 formed on layer surfaces on both sides in the thickness direction of the piezoelectric layer 14 are provided. In the piezoelectric thin film element, the piezoelectric layer 14 is formed such that the residual strain has a first value larger than a predetermined value and a second value smaller than the predetermined value depending on the direction of voltage application. . The linearity between the applied voltage and the displacement can be ensured by using one of two types of values having different residual strains. The piezoelectric layer does not necessarily require a polarization process, and the piezoelectric characteristics are hardly affected by external influences.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric thin film element exhibiting an electromechanical conversion function, a thin film actuator and an ink jet head using the piezoelectric thin film element, and an ink jet recording apparatus including the ink jet head as a printing unit.

A piezoelectric thin film element exhibiting an electromechanical conversion function generally includes a laminated body in which a piezoelectric thin film is sandwiched between two electrodes in the thickness direction. Typical examples of the piezoelectric material include lead zirconate titanate (Pb (Zr, Ti) O ₃ ) (hereinafter referred to as “PZT”), which is an oxide having a perovskite crystal structure, and magnesium, manganese, and PZT. , Nickel, niobium and the like.

  In particular, in the case of tetragonal PZT having a perovskite crystal structure, a large piezoelectric displacement is obtained in the <001> axial direction (C-axis direction), and in the case of rhombohedral PZT, in the <111> axial direction. Large piezoelectric displacement is obtained. However, many piezoelectric materials are polycrystals (piezoelectric ceramics) composed of aggregates of crystal particles, and each crystal axis faces a random direction. For this purpose, the spontaneous polarization Ps is also randomly arranged, but in the case of a piezoelectric thin film element, the sum of those vectors is made to be parallel to the electric field direction. In a thin film actuator that is one form of use of a piezoelectric thin film element, when a voltage is applied between both electrodes, a mechanical displacement proportional to the magnitude of the voltage is obtained. The ink jet head uses this piezoelectric thin film element as a vibrator serving as an ink discharge drive source.

  By the way, in the PZT-based piezoelectric ceramics, the relationship between the electric field and strain when an electric field of a certain magnitude is applied is almost linear when the applied electric field is small, but when the applied electric field exceeds a certain critical value, It becomes a symmetrical butterfly shape (see, for example, Non-Patent Document 1). The same applies to the case of a piezoelectric thin film formed on a substrate (see, for example, Patent Document 1).

In (Patent Document 1), after applying an electric field to a virgin state piezoelectric thin film element, residual strain and polarization distortion occur even if the electric field is removed, and good piezoelectric characteristics cannot be obtained. There has been proposed a method for improving the piezoelectric effect by reducing the amount of foreign matter existing between crystal grains and reducing the residual strain to 2.5 × 10 ⁻⁴ or less. Here, the residual strain is a displacement exhibited when the electric field strength is 0 (kV / cm).
Japanese Patent Laid-Open No. 11-214763 Kenji Uchino “Piezoelectric / Electrostrictive Actuator” Morikita Publishing Co., Ltd. (page 34)

  However, when a piezoelectric thin film is formed using a piezoelectric material, there are various stresses such as stress generated in the thin film at the time of formation, stress due to the difference in linear expansion coefficient from the base substrate, stress received from thin films such as electrode films There are various internal stresses. These stresses cause residual strain that occurs after applying an electric field to the piezoelectric thin film and removing the electric field in the same way as when foreign matter exists between crystal grains of the piezoelectric thin film. It becomes an obstacle to obtain the characteristics. For example, when a piezoelectric thin film element is applied to a thin film actuator, not only is it difficult to obtain a linear displacement with respect to an applied voltage, but reproducibility of the displacement with respect to the voltage is not obtained in a long-term use. However, these internal stresses are inevitably generated in the case of forming a thin film and are very difficult to eliminate.

  The present invention has been made in view of the above, and a piezoelectric thin film element having good piezoelectric characteristics even when various internal stresses exist at the time of thin film formation, a thin film actuator and an ink jet head using the piezoelectric thin film element, and the above-mentioned An object of the present invention is to obtain an ink jet recording apparatus provided with an ink jet head as printing means.

  In order to achieve the above-described object, the present invention provides a piezoelectric layer formed of an oxide containing Pb having a perovskite crystal structure, and an electrode layer formed on each of the layer surfaces on both sides in the thickness direction of the piezoelectric layer. In the piezoelectric thin film element, the piezoelectric layer has a first value whose residual strain is larger than a predetermined value and a second value smaller than the predetermined value depending on a voltage application direction. It is characterized by being formed into a film.

  According to the present invention, since the piezoelectric layer is formed under the condition that the polarization is already oriented in one direction after the formation, the residual strain is formed so that the residual strain has two kinds of values depending on the voltage application direction. can do. In other words, even when various internal stresses are present during the formation of the thin film, the linearity between the applied voltage and the displacement can be ensured by using one of two values having different residual strains. . In addition, the piezoelectric layer does not necessarily require a polarization process, and the piezoelectric characteristics are hardly affected by external influences. That is, a piezoelectric thin film element having good piezoelectric characteristics can be obtained.

  According to the present invention, there is an effect that a piezoelectric thin film element having good piezoelectric characteristics can be obtained even when various internal stresses exist during the formation of the thin film.

  Exemplary embodiments of a piezoelectric thin film element, a thin film actuator, an ink jet head, and an ink jet recording apparatus according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a configuration of a piezoelectric thin film element according to Embodiment 1 of the present invention. As shown in FIG. 1, the piezoelectric thin film element according to the first embodiment includes an adhesion layer 12, a first electrode layer 13 that is a lower electrode, a piezoelectric layer 14 that is a piezoelectric thin film, and a substrate 11. The second electrode layer 15 that is the upper electrode is formed by depositing in this order.

  There are various film forming methods for this piezoelectric thin film element, such as sputtering, vacuum deposition, laser ablation, ion plating, MBE, PVD, MOCVD, plasma CVD, sol-gel, and MOD. In the first embodiment, a sputtering method is used for forming the piezoelectric layer 14. Other elements are optional.

  As the substrate 11, a silicon substrate is used in the first embodiment, but a glass substrate, a metal substrate, a ceramic substrate, or the like can also be used as a matter of course.

  The adhesion layer 12 is for enhancing the adhesion between the substrate 11 and the first electrode layer 13. In the first embodiment, the case where the adhesion layer 12 is provided for the purpose of maintaining generality is shown. However, if there is no problem in the adhesion between the substrate 11 and the first electrode layer 13, it is not necessary to provide the adhesion layer 12. The film thickness of the adhesion layer 12 should just be in the range of 0.005-1 micrometer. The material used for the adhesion layer 12 is titanium (Ti) in the first embodiment, but may be tantalum, iron, cobalt, nickel, chromium, a compound thereof, or the like.

  The material used for the first electrode layer 13 is usually platinum (Pt), but may be at least one noble metal selected from the group of Pt, iridium, palladium and ruthenium or a compound thereof. Should just be in the range of 0.05-2 micrometers.

  The last second electrode layer 15 is usually made of platinum (Pt), but any conductive material may be used. The thickness should just be in the range of 0.1-0.4 micrometer.

  The piezoelectric layer 14 is lead (Pb) having a perovskite crystal structure such as lead zirconate titanate (PZT) that can be formed so that the polarization is already in one direction after the thin film is formed. However, by forming the film using a sputtering method as described above, “residual strain has different characteristics depending on the direction of voltage application” and “obtains desired crystal orientation. "Make columnar particle diameter and film thickness ratio within desired range" "Make foreign matter not exist between columnar particles" "Make polarization treatment at high temperature unnecessary after thin film formation" Realize.

First, the piezoelectric layer 14 is preferentially oriented in either the <111> plane or the <001> plane because the polarization is already in one direction after the thin film is formed. Due to this preferential orientation, the residual strain varies depending on the direction of voltage application, one of which has a value exceeding 2.5 × 10 ⁻⁴ and the other has a value of less than 2.5 × 10 ^−4. Characteristics are obtained. The orientation ratio in the <111> plane or the <001> plane is desirably 90% or more, but if it is 70% or more, a temporary characteristic can be obtained.

  Here, if the orientation rate in the <111> plane is expressed as α <111> and the orientation rate in the <001> plane is expressed as α <001>, α <111> = I <111> / ΣI ( hkl), α <001> = I <001> / ΣI (hkl). Note that ΣI (hkl) is the sum of diffraction peak intensities from each crystal plane in PZT of a perovskite crystal structure with 2θ of 10 ° to 70 ° when using Cu-Kα rays in the X-ray diffraction method. is there.

  The piezoelectric layer 14 has a thickness in the range of 1 μm to 10 μm, but the film structure is a columnar structure grown in the thickness direction. And the particle diameter of the columnar particles is 0.1 μm to 0.8 μm, and the ratio of the particle diameter of the columnar particles to the film thickness is 1/2 to 1/100. By having such a shape, the above-described residual strain varies depending on the voltage application direction, and can be realized. That is, by using any one of two different values, the linearity between the applied voltage and the displacement can be ensured, so that excellent piezoelectric characteristics can be realized.

  The piezoelectric layer 14 has a columnar structure in which the film structure grows in the thickness direction, but no foreign matter exists between the columnar particles. Also from this point, the residual strain described above varies depending on the voltage application direction, and excellent piezoelectric characteristics can be realized.

  In addition, in the case of a piezoelectric thin film, since a base substrate, an electrode film, and the like exist, it is not possible to freely change crystal distortion during polarization treatment as in normal ceramics. For this reason, when polarization processing is performed, distortion due to inversion of polarization or the like remains without being relaxed, and thus sufficient polarization processing is difficult to perform. When the polarization treatment is forcibly performed by increasing the voltage, microcracks are easily generated inside the piezoelectric thin film, or peeling is likely to occur at the interface with the electrode film or the substrate. Since the piezoelectric layer 14 which is the main part of the piezoelectric thin film element according to this embodiment has the polarization aligned in one direction after formation, it is not necessary to perform a polarization process at a high temperature. Therefore, since the piezoelectric characteristics are not easily affected by external influences, the above-described reliability is not lowered.

  Next, FIG. 2 is a perspective view showing an external appearance of a thin film actuator manufactured using the piezoelectric thin film element shown in FIG. A thin film actuator 50 shown in FIG. 2 includes a support portion 51 corresponding to the substrate 11, an adhesion layer 52 corresponding to the adhesion layer 12, a first electrode layer 53 corresponding to the first electrode layer 13, and a piezoelectric layer. 14 and a second electrode layer 55 corresponding to the second electrode layer 15.

In the thin film actuator 50 using the piezoelectric thin film element according to the first embodiment, the application direction of the driving voltage is a direction in which the residual strain has a value exceeding 2.5 × 10 ⁻⁴ . As a result, the thin film actuator 50 is a thin film actuator having excellent durability performance since the piezoelectric characteristics of the piezoelectric thin film layer do not deteriorate during use.

  In the following, two production examples (Examples 1 and 2) with different film formation conditions (sputtering conditions) for only the piezoelectric layer 14 are shown, and the piezoelectric thin film according to the first embodiment having the above-described piezoelectric characteristics. The film forming conditions (sputtering conditions) of the piezoelectric layer 14 from which the element is obtained are shown.

  The film forming conditions are different only in the piezoelectric layer 14, and the thickness of each layer is the same. Therefore, the entire manufacturing procedure is described first. That is, in FIG. 1, a substrate 11 is a disk-shaped silicon wafer substrate having a thickness of 0.3 mm and a diameter of 4 inches. On the upper surface of the disk-shaped silicon substrate 11, an adhesion layer 12 having a thickness of 0.02 μm, a first electrode layer 13 having a thickness of 0.22 μm, a piezoelectric layer 14 having a thickness of 3.0 μm, and a thickness of 0.02 μm. The second electrode layer 15 was formed by sequentially forming a film by a sputtering method.

  The adhesion layer 12 was formed using, for example, a titanium (Ti) target and applying high frequency power of 100 W for 1 minute while heating the substrate 11 to 400 ° C. in an argon gas with a vacuum degree of 1 Pa. The first electrode layer 13 was formed by using, for example, a platinum (Pt) target and applying high-frequency power of 200 W for 12 minutes while heating the substrate 11 at 400 ° C. in an argon gas with a vacuum degree of 1 Pa. The second electrode layer 15 was formed using, for example, a platinum (Pt) target and applying high-frequency power of 200 W for 10 minutes in an argon gas having a degree of vacuum of 1 Pa at room temperature.

  Here, a PZT sintered target having a composition of Zr / Ti = 53/47 was used for the piezoelectric layer 14, but the Zr / Ti composition of PZT was a boundary between a tetragonal crystal and a rhombohedral crystal (morphotropic phase). Since Zr / Ti = 52/48 near the boundary), the Zr / Ti composition in the piezoelectric layer 14 is not limited to the above composition. The constituent material of the piezoelectric layer 14 may be a piezoelectric material mainly composed of PZT, such as PZT containing additives such as La, Sr, Nb, and Al. There may be.

[Example 1: The piezoelectric layer 14 is obtained by heating the substrate 11 to 610 ° C. in a mixed atmosphere of argon and oxygen with a degree of vacuum of 0.3 Pa (gas volume ratio Ar: O ₂ = 15: 5). The film was formed by applying high-frequency power of 200 W for 240 minutes. And “Example 2: The piezoelectric layer 14 has the substrate 11 at 650 ° C. in a mixed atmosphere of argon and oxygen with a degree of vacuum of 0.4 Pa (gas volume ratio Ar: O ₂ = 18: 2). While heating, 150 W high frequency power was applied for 80 minutes to form a film. The case will be described.

(A) About Example 1 As a result of examining the crystal structure and crystal orientation by X-ray diffraction, the piezoelectric layer 14 had a rhombohedral perovskite crystal structure and had a <111> orientation. . The <111> orientation ratio was 99%. As a result of SEM observation, the piezoelectric layer 14 had a columnar structure. The film thickness was 3.0 μm. The columnar particle diameter was 0.3 μm on average, and the ratio between the columnar particle diameter and the film thickness was 1/10. As a result of examining the presence or absence of foreign matter between the columnar particles by TEM, no foreign matter was found between the columnar particles. Furthermore, as a result of examining the composition of the inside of the columnar particles and the crystal grain boundary (between the columnar particles) with an X-ray microanalyzer, both had the same composition and were Pb _1.08 (Zr _0.535 , Ti _0.465 ) O ₃ .

Next, a cantilever cut out to 20 mm × 2.5 mm was manufactured by dicing, and the relationship between the electric field and strain and the piezoelectric constant d ₃₁ were measured. The measurement method is basically the same as (Patent Document 1).

  FIG. 3 is a diagram showing the relationship between applied electric field and strain in the piezoelectric thin film element obtained in Example 1. As shown in FIG. 3, the change in distortion with respect to the electric field of the piezoelectric thin film element obtained in Example 1 was not a symmetrical butterfly shape, but asymmetrical left and right. This indicates that the polarization is already directed in one direction after the formation of the piezoelectric layer 14.

When the electric field strength is zero, the value of residual strain is negative on the second electrode layer 15 side (upper electrode) while maintaining the first electrode layer 13 side (lower electrode on the substrate 11 side) at the ground potential. When a voltage was applied, it was 3.4 × 10 ⁻⁴ , but when a positive voltage was applied, it was 0.1 × 10 ⁻⁴ .

From this, one of the two types of values that the residual strain has depending on the voltage application direction is a value that exceeds 2.5 × 10 ⁻⁴ , and the other is a value that is less than 2.5 × 10 ^−4. I understand. In this case, the case where a negative voltage is applied to the second electrode layer 15 is forward with respect to the polarization direction.

In addition, Table 1 shows the piezoelectric constant d ₃₁ when a negative voltage is applied to the second electrode layer 15.

From Table 1, it can be seen that the piezoelectric constant d ₃₁ is substantially constant with respect to the electric field strength, that is, the applied voltage. This is because there is no distortion due to the rotation of the polarization accompanying an increase in voltage, indicating that the polarization is stably oriented in one direction.

  Next, the characteristics of the thin film actuator (FIG. 2) produced using the piezoelectric thin film element obtained in Example 1 were as follows. That is, the first electrode layer 53 of the thin film actuator 50 is maintained at the ground potential, and a sin wave having an electric field intensity of −100 (V / cm) and a period of 1 kHz is continuously applied to the second electrode layer 55 for 1000 hours. As a result of measuring the displacement of the actuator every 25 hours in the applied state and investigating the change over time, the decrease in the displacement amount showing the change over time of 1000 hours of continuous driving is 2%, and excellent piezoelectric characteristics It was found that it has the durability performance.

(B) About Example 2 The observation results of the piezoelectric layer 14 with the film forming conditions changed were as follows. That is, as a result of X-ray diffraction, it had a rhombohedral perovskite crystal structure, but no crystal orientation. As a result of SEM observation, it similarly had a columnar structure. The film thickness was 1.0 μm. The columnar particle diameter was 0.55 μm on average, and the ratio between the columnar particle diameter and the film thickness was 1.1 / 2. Furthermore, as a result of examining the presence or absence of foreign matter between the columnar particles by TEM, no foreign matter having a structure different from that of the crystal particles was observed at the crystal grain boundary. As a result of examining the composition of the inside of the columnar particles and the crystal grain boundary (between the columnar particles) with an X-ray microanalyzer, the compositions were both Pb _1.03 (Zr _0.533 , Ti _0.467 ) O ₃ .

Next, a cantilever cut out to 20 mm × 2.5 mm by dicing was prepared, and the relationship between the electric field and strain and the piezoelectric constant d ₃₁ were measured. The measurement method is basically the same as (Patent Document 1).

FIG. 4 is a graph showing the relationship between applied electric field and strain in the piezoelectric thin film element obtained in Example 2. As shown in FIG. 4, in the piezoelectric thin film element obtained in Example 2, the distortion change with respect to the applied electric field was a symmetrical butterfly shape unlike FIG. This indicates that in the piezoelectric layer 14 whose manufacturing method is changed, the polarization is not directed in one direction after the film formation. When the electric field strength was zero, the value of residual strain was 1.5 × 10 ⁻⁴ , the same value, regardless of the direction of application of the electric field.

The piezoelectric constant d ₃₁ when a negative voltage is applied to the second electrode layer 15 is shown in (Table 2).

From Table 2, it can be seen that the piezoelectric constant d ₃₁ is not constant with respect to the electric field strength, that is, the applied voltage, and increases as the voltage increases. This is because distortion due to the rotation of the polarization accompanying an increase in voltage occurs, indicating that the polarization is not stably oriented in one direction.

  Next, similarly, the thin film actuator 50 shown in FIG. 2 was manufactured using the piezoelectric thin film element obtained in Example 2, and the actuator characteristics were examined by the same method as described above. That is, as described above, the first electrode layer 53 of the thin film actuator 50 is maintained at the ground potential, and a sine wave having an electric field strength of −100 (V / cm) and a period of 1 kHz is applied to the second electrode layer 55. The displacement of the actuator was measured every 25 hours in the state of being continuously applied for 1000 hours, and the change with time was examined. As a result, the decrease of the displacement amount showing the change with time of displacement with respect to 1000 hours of continuous driving was 18%, and a large decrease was observed.

From the above comparison results, according to the first embodiment, “the residual strain of the piezoelectric layer has two different values depending on the application direction of the voltage, and one of the values exceeds 2.5 × 10 ^−4. It can be understood that a piezoelectric thin film element having a value ^less than 2.5 × 10 ⁻⁴ can be manufactured by appropriately selecting the film formation conditions (sputtering conditions) of the piezoelectric layer.

When a thin film actuator manufactured using the same is used by applying a voltage in a direction in which the residual strain has a value exceeding 2.5 × 10 ⁻⁴ , the reversal of polarization can be achieved. Since it does not occur, even if it has a large residual strain exceeding 2.5 × 10 ⁻⁴ , the piezoelectric characteristics do not deteriorate, and it has excellent piezoelectric performance and excellent long-term stability. Understandable.

(Embodiment 2)
In the second embodiment, a configuration example of an inkjet head using the piezoelectric thin film element according to the first embodiment as a vibrator serving as an ink discharge drive source will be described. Briefly, the inkjet head includes a diaphragm layer provided on one of the electrode-side surfaces of the piezoelectric thin film element according to the first embodiment, and a surface of the diaphragm layer opposite to the piezoelectric thin film element. And a pressure chamber member having a pressure chamber for containing ink, and the diaphragm layer is displaced in the layer thickness direction by the piezoelectric effect of the piezoelectric thin film element so that the ink in the pressure chamber is ejected. Composed. Hereinafter, a specific configuration example (FIGS. 5 to 7) and a manufacturing procedure (FIGS. 8 to 13) will be shown.

  FIG. 5 is an external view showing the overall configuration of the inkjet head according to the second embodiment of the present invention. FIG. 6 is a perspective view showing a configuration of a main part of the ink jet head shown in FIG. As shown in FIGS. 5 and 6, the inkjet head 100 includes a pressure chamber member A, an actuator part B, an ink flow path member C, and a nozzle plate D as main elements.

  5 and 6, the pressure chamber member A is formed with a large number of pressure chamber openings 101 penetrating in the thickness direction (vertical direction). The large number of pressure chamber openings 101 are constituted by an actuator part B arranged so as to cover the upper end opening in common and an ink flow path member C arranged so as to cover the lower end opening in common. By closing the upper and lower ends, individual pressure chambers 102 are formed.

  The ink flow path member C includes a common liquid chamber 105 shared by the pressure chambers 102 arranged in the ink supply direction, a supply port 106 for supplying ink in the common liquid chamber 105 to the pressure chamber 102, And an ink flow path 107 for discharging the ink. A nozzle hole 108 communicating with the ink flow path 107 is formed in the nozzle plate D. In addition, a voltage is supplied from the IC chip E to each individual electrode 103 through the bonding wire BW.

  Next, FIG. 7 is a cross-sectional view showing a configuration of an actuator part that is a main part of the ink jet head shown in FIG. FIG. 7 shows a cross-sectional configuration in a direction orthogonal to the ink supply direction shown in FIG. 5, and a pressure chamber member A having four pressure chambers 102 arranged in the orthogonal direction is drawn for reference. . The four pressure chambers 102 are partitioned by a partition wall 102a.

  As shown in FIG. 7, the actuator portion B is a member constituting a common ceiling surface for each pressure chamber 102, and is an intermediate layer (on the side of the partition wall 102a) bonded to the upper end surface of the partition wall 102a with an adhesive 114. 113 formed on the same surface as the wall surface, a vibration layer 111 laminated thereon, and a second electrode layer 112 which is a common electrode laminated thereon.

  The actuator portion B is a driving means for each pressure chamber 102, and includes a piezoelectric layer 110 provided at a position immediately above each pressure chamber 102 on the upper surface of the second electrode layer 112, and individual electrodes stacked thereon. A first electrode layer 103 is provided.

  That is, the actuator unit B includes a piezoelectric thin film element having a configuration in which the second electrode layer 112, the piezoelectric layer 110, and the first electrode layer 103 are sequentially stacked for each pressure chamber 102. The vibration layer 111 is provided on the second electrode layer 112 side which is a common electrode. The constituent materials of the first electrode layer 103, the piezoelectric layer 110, and the second electrode layer 112 are the first electrode layer 13, the piezoelectric layer 14, and the second electrode layer 15 described in the first embodiment. The structure of the piezoelectric layer 110 is the same as that of the piezoelectric layer 14. However, some of the constituent elements have different contents.

  In the actuator portion B, according to this configuration, the vibration layer 111 is displaced in the layer thickness direction and vibrates by the piezoelectric effect of the piezoelectric layer 110 with respect to one pressure chamber 102, thereby changing the volume of the pressure chamber 102. Can do.

  The pressure chamber member A and the actuator portion B are bonded to each other with an adhesive 114. However, when the intermediate layer 113 is bonded using the adhesive 114, a part of the adhesive 114 is separated from the partition wall 102a. Even when the adhesive layer 114 protrudes outward, the upper surface of the pressure chamber 102, which is the upper end surface of the partition wall 102a, causes the vibration layer 111 to undergo the desired displacement and vibration without adhering to the vibration layer 111. And has a role of expanding the distance between the lower surface of the vibration layer 111. Therefore, there is a case in which the vibration layer 111 is directly supported on the upper end surface of the partition wall 102a without providing the intermediate layer 113.

  Next, referring to FIG. 8 to FIG. 12, from the main part excluding the IC chip E shown in FIG. 5, that is, from the pressure chamber member A, the actuator part B, the ink flow path member C and the nozzle plate D shown in FIG. A method for manufacturing the inkjet head will be described.

  FIG. 8 is a cross-sectional view illustrating a laminating process, a pressure chamber opening forming process, and an adhesive attaching process. As shown in FIG. 8A, an adhesion layer 121, a first electrode layer 103, a piezoelectric layer 110, a second electrode layer 112, a vibration layer 111, an intermediate layer (vertical wall) are sequentially formed on a substrate 120. A film 113 is deposited by sputtering.

  Note that the adhesion layer 121 is the same as the adhesion layer 12 described in Embodiment 1, and is interposed between the two in order to improve the adhesion between the substrate 120 and the first electrode layer 103. That is, the adhesion layer 121 is not essential. As will be described later, the adhesion layer 121 is removed in the same manner as the substrate 120.

  Here, the substrate 120 is a substrate for film formation, that is, a substrate serving as a unit for producing one piezoelectric thin film element. The substrate 120 is the same as the substrate 11 described in the first embodiment, and may be any of a silicon (Si) substrate, a glass substrate, a metal substrate, and a ceramic substrate. The shape may be a disc shape having an appropriate thickness as shown in Example 1, but here, for the substrate 120, for example, a Si substrate cut into a square shape with a thickness of 18 mm was used.

  The adhesion layer 121, the first electrode layer 103, the piezoelectric layer 110, and the second electrode layer 112 were produced by the same method as in Example 1 described above, but here, the vibration layer that is an additional element The material of 111 and the intermediate layer 113 and the manufacturing method will be described.

  That is, the vibration layer 111 is a single element such as Cr, nickel, aluminum, tantalum, tungsten, silicon, or any one of these oxides or nitrides (for example, silicon dioxide, aluminum oxide, zirconium oxide, silicon nitride), For example, a Cr target was used to maintain the substrate 120 at room temperature in an argon gas with a vacuum degree of 1 Pa and apply 200 W of high frequency power for 6 hours. The film thickness is 3 μm here, but may be in the range of 1 μm to 10 μm.

  Further, the intermediate layer 113 is formed by applying a high-frequency power of 200 W for 5 hours while maintaining the substrate 120 at room temperature in an argon gas having a degree of vacuum of 1 Pa using a conductive metal such as Ti or Cr, for example, a Ti target. Formed. The film thickness is 5 μm here, but may be in the range of 3 μm to 10 μm.

  Next, a pressure chamber member A is formed as shown in FIGS. FIG. 13 is a plan view for explaining the relationship between the film formation substrate and the pressure chamber member substrate. As shown in FIG. 13, the substrate 130 used in the pressure chamber member A is a Si wafer substrate that is large enough to mount the required number of substrates 120. Specifically, the substrate 130 has a disk shape with an appropriate diameter (here, 4 inches) within a range of 2 inches to 10 inches.

  The pressure chamber member A is formed using this substrate 130. Specifically, first, a plurality of pressure chamber openings 101 are patterned on the substrate 130. In this patterning, as can be seen from FIG. 8B, the four pressure chamber openings 101 are set as one set, and the thickness width of the partition wall 102b dividing each set is determined by the pressure chamber openings 101 in each set. It is set to approximately twice the width of the partition wall 102a to be partitioned.

  Then, the pressure chamber member A is obtained by processing the patterned substrate 130 by chemical etching or dry etching to form four pressure chamber openings 101 in each group.

  Thereafter, as shown in FIG. 8C, the pressure chamber member A and the substrate 130 are bonded with an adhesive 114. The formation of the adhesive 114 is by electrodeposition. In FIG. 8C, first, an adhesive 114 is attached by electrodeposition to the upper surfaces of the partition walls 102a and 102b of the pressure chamber as an adhesive surface on the pressure chamber member A side. Specifically, although not shown in the drawing, a Ni thin film of several hundreds of centimeters thin enough to transmit light is formed as a base electrode film on the upper surfaces of the partition walls 102a and 102b by a sputtering method, and then on the Ni thin film. Then, a patterned adhesive 114 is formed.

  Here, as the electrodeposition liquid, a solution obtained by adding 0 to 50 parts by weight of pure water to the acrylic resin aqueous dispersion and stirring and mixing it well is used. The reason why the thickness of the Ni thin film is set so thin that light is transmitted is to make it easy to visually recognize that the adhesive resin is completely attached to the substrate 130. According to experiments, the electrodeposition conditions are preferably a liquid temperature of about 25 ° C., a DC voltage of 30 V, and an energization time of 60 seconds. Under this condition, an acrylic resin of about 3 to 10 μm is electrodeposited on the Ni thin film of the pressure chamber member substrate 130.

  Next, FIG. 9 is a cross-sectional view illustrating a bonding process between the substrate after film formation and the pressure chamber member and a vertical wall forming process. As shown in FIG. 9A, an adhesive 114 is used in which a predetermined number of film-forming substrates 120 stacked as described above and the pressure chamber member A (that is, the substrate 130) are electrodeposited as described above. And glue. This adhesion is performed using the intermediate layer 113 formed on the substrate 120 as a substrate-side adhesion surface.

  FIG. 13 shows this state. In the example shown in FIG. 13, the substrate 120 has a rectangular shape of 18 mm square, whereas the disk surface of the substrate 130 has a large circular shape of 4 inches, so that the 14 film-forming substrates 120 have pressure. It is attached to one substrate 130 used in the chamber member A.

  This affixing is performed in a state where the center of each substrate 120 is positioned so as to be positioned at the center of the partition wall 102b of the pressure chamber member A, as shown in FIG. After pasting, the pressure chamber member A is pressed and brought into close contact with the substrate 120 side to enhance the adhesion between them. Further, the bonded substrate 120 and pressure chamber member A are gradually heated and heated in a heating furnace to completely cure the adhesive 114. Subsequently, as shown in FIG. 9B, plasma treatment is performed to remove the fragments protruding from the pressure chamber opening 101 in the adhesive 114. Further, the intermediate layer 113 is etched using the partition walls 102a and 102b of the pressure chamber member A as a mask, and finished in a predetermined shape that is continuous with the vertical walls of the partition walls 102a and 102b.

  In FIG. 9A, the substrate 120 after film formation and the pressure chamber member A are bonded together, but the substrate 120 for forming the pressure chamber member at a stage where the pressure chamber opening 101 is not formed is formed. And may be adhered.

  Next, FIG. 10 is a cross-sectional view for explaining the film formation substrate and the adhesion layer removal step after film formation and the individualization step of the first electrode layer. As shown in FIG. 10A, after forming FIG. 9B, the film-forming substrate 120 and the adhesion layer 121 after film formation are removed by etching. After that, as shown in FIG. 10B, the first electrode layer 103 positioned on the pressure chamber member A is etched by using a photolithography technique and individualized into each pressure chamber 102.

  Next, FIG. 11 is a cross-sectional view illustrating a piezoelectric layer individualizing process and a pressure chamber member substrate cutting process. As shown in FIG. 11A, the piezoelectric layer 110 and the orientation control layer 104 are etched to be individualized into a shape similar to that of the first electrode layer 103 by using a photolithography technique. In these etchings, the first electrode layer 103 and the piezoelectric layer 110 are positioned above each of the pressure chambers 102, and the center in the width direction of the first electrode layer 103 and the piezoelectric layer 110 corresponds to the pressure chamber. It is formed so as to coincide with the center of the width direction 102 with high accuracy.

  After the first electrode layer 103 and the piezoelectric layer 110 are individually provided for each pressure chamber 102 in this way, as shown in FIG. 11B, the pressure chamber member substrate (substrate 130) is attached to each partition wall 102b. By cutting at a part, four sets of pressure chamber members A having four pressure chambers 102 and actuator portions B fixed on the upper surface thereof are completed.

  Next, FIG. 12 illustrates an ink flow path member and nozzle plate generating process, an ink flow path member and nozzle plate bonding process, a pressure chamber member and ink flow path member bonding process, and a completed inkjet head. It is sectional drawing.

  Thereafter, as shown in FIG. 12A, the common liquid chamber 105, the supply port 106, and the ink flow path 107 are formed in the ink flow path member C, and the nozzle hole 108 is formed in the nozzle plate D. Next, as shown in FIG. 12B, the ink flow path member C and the nozzle plate D are bonded using an adhesive 109.

  Thereafter, as shown in FIG. 12C, an adhesive (not shown) is transferred to the lower end surface of the pressure chamber member A or the upper end surface of the ink channel member C, and the pressure chamber member A and the ink channel member C are transferred. The two are bonded together by the adhesive 109. Thus, an ink jet head having a pressure chamber member A, an actuator portion B, an ink flow path member C, and a nozzle plate D is completed as shown in FIG.

  The ink jet head manufactured as described above uses a piezoelectric thin film element having a piezoelectric thin film (piezoelectric layer) manufactured under the film forming conditions according to Example 1 of the first embodiment. In this ink jet head, a predetermined voltage was applied between the first electrode layer 103 and the second electrode layer 112, and an AC voltage having a frequency of 20 kHz and a peak value of 30 V was continuously applied for 100 days. There was no drop in the discharge performance.

  On the other hand, when an inkjet head using a piezoelectric thin film element having a piezoelectric thin film (piezoelectric layer) manufactured under the film forming conditions according to Example 2 in Embodiment 1 was manufactured, a similar test was performed on this inkjet head. Ink ejection failure occurred in a portion corresponding to all the pressure chambers 102. This is not due to ink clogging or the like, and it is considered that the piezoelectric performance of the actuator portion B (piezoelectric thin film element) has been lowered.

  Therefore, the inkjet head according to the second embodiment using the piezoelectric thin film element having the piezoelectric thin film (piezoelectric layer) manufactured under the film forming conditions according to the first embodiment in the first embodiment is excellent in long-term durability performance. You can see that

(Embodiment 3)
In the third embodiment, a configuration example of an ink jet recording apparatus using the ink jet head according to the second embodiment is shown. Briefly, this ink jet recording apparatus includes the ink jet head according to the second embodiment that uses a piezoelectric thin film element having a piezoelectric thin film (piezoelectric layer) manufactured under the film forming conditions according to the first embodiment of the first embodiment. And a relative moving means for moving the ink jet head and the recording medium relative to each other, and the ink jet head communicates with a pressure chamber when the ink jet head is moved relative to the recording medium by the relative moving means. Recording is performed by ejecting the ink in the pressure chamber onto a recording medium from a nozzle hole provided to do so. A specific configuration example (FIG. 14) is shown below.

  FIG. 14 is a schematic perspective view showing the configuration of an ink jet recording apparatus according to Embodiment 3 of the present invention. An ink jet recording apparatus 27 shown in FIG. 14 includes an ink jet head 28 according to the second embodiment. In the ink jet head 28, the ink in the pressure chamber is transferred from a nozzle hole (nozzle hole 108 in the second embodiment) provided to communicate with the pressure chamber (the pressure chamber 102 in the second embodiment). It is configured to perform recording by discharging the ink.

  The inkjet head 28 is mounted on a carriage 31 provided on a carriage shaft 30 that extends in the main scanning direction X, and reciprocates in the main scanning direction X as the carriage 31 reciprocates along the carriage shaft 30. It is configured. Thus, the carriage 31 constitutes a relative movement unit that relatively moves the inkjet head 28 and the recording medium 29 in the main scanning direction X.

  In addition, the ink jet recording apparatus 27 includes a plurality of rollers 32 that move the recording medium 29 in the sub scanning direction Y substantially perpendicular to the main scanning direction X (width direction) of the ink jet head 28. Thus, the plurality of rollers 32 constitute a relative moving unit that relatively moves the inkjet head 28 and the recording medium 29 in the sub-scanning direction Y. In FIG. 14, Z is the vertical direction.

  When the ink jet head 28 is moved in the main scanning direction X by the carriage 31, ink is ejected from the nozzle holes of the ink jet head 28 to the recording medium 29. The relative moving means is controlled so that the medium 29 is moved by a predetermined amount and printing for the next one scan is performed.

  As described above, the ink jet recording apparatus according to the third embodiment uses the piezoelectric thin film element having the piezoelectric thin film (piezoelectric layer) manufactured under the film forming conditions according to the first embodiment in the first embodiment. Therefore, it is possible to have good printing performance and durability.

  In this specification, as a suitable application example of the piezoelectric thin film element according to the first embodiment, an application example to an ink jet head and an ink jet recording apparatus is shown, but the present invention is not limited to this. , Thin film capacitors, charge storage capacitors for nonvolatile memory elements, various actuators, infrared sensors, ultrasonic sensors, pressure sensors, angular velocity sansei, acceleration sensors, flow sensors, shock sensors, piezoelectric transformers, piezoelectric ignition elements, piezoelectric speakers, piezoelectrics The present invention can also be applied to a microphone, a piezoelectric filter, a piezoelectric pickup, a tuning fork oscillator, a delay line, and the like.

  As described above, the piezoelectric thin film element according to the present invention is useful for forming good piezoelectric characteristics even when various internal stresses existing at the time of thin film formation exist. It is suitable for improving the durability performance of the recording apparatus.

Sectional drawing which shows the structure of the piezoelectric thin film element by Embodiment 1 of this invention The perspective view which shows the external appearance of the thin film actuator produced using the piezoelectric thin film element shown in FIG. The figure which shows the relational characteristic of the applied electric field and distortion in the piezoelectric-material thin film element shown in FIG. 1 produced on the film-forming conditions (sputtering conditions) of the piezoelectric material layer by Example 1. FIG. The figure which shows the relational characteristic of the applied electric field and distortion in the piezoelectric-material thin film element shown in FIG. 1 produced on the film-forming conditions (sputtering conditions) of the piezoelectric material layer by Example 2. FIG. FIG. 3 is an external view showing the overall configuration of an inkjet head according to a second embodiment of the present invention. The perspective view which shows the structure of the principal part of the inkjet head shown in FIG. Sectional drawing which shows the structure of the actuator part which is the principal part of the inkjet head shown in FIG. Sectional drawing explaining the manufacturing procedure (lamination process, the formation process of the opening part for pressure chambers, and the adhesion process of an adhesive agent) of the inkjet head shown in FIG. Sectional drawing explaining the manufacturing procedure (The adhesion process of the film-forming board | substrate and pressure chamber member after film-forming, and the formation process of a vertical wall) of the inkjet head shown in FIG. Sectional drawing explaining the manufacturing procedure (The board | substrate for film-forming and the adhesion | attachment layer after film-forming, and the individualization process of the 1st electrode layer) of the inkjet head shown in FIG. Sectional drawing explaining the manufacturing procedure (Individualization process of a piezoelectric material layer, and the cutting process of the board | substrate for pressure chamber members) of the inkjet head shown in FIG. Manufacturing procedure of ink jet head shown in FIG. 5 (ink flow channel member and nozzle plate generating step, ink flow channel member and nozzle plate bonding step, pressure chamber member and ink flow channel member bonding step, and completed ink jet head ) The top view explaining the relationship between the board | substrate (film-forming substrate) formed into a film in the manufacturing process shown in FIG. 8, and the board | substrate (pressure chamber member board | substrate) used with a pressure chamber member Schematic perspective view showing the configuration of an ink jet recording apparatus according to Embodiment 3 of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Substrate 12 Adhesion layer 12 1st electrode layer 14 Piezoelectric layer 15 2nd electrode layer 27 Inkjet recording device 28 Inkjet head 29 Recording medium 30 Carriage shaft 31 Carriage (relative movement means)
DESCRIPTION OF SYMBOLS 50 Thin film actuator 51 Support part 52 Adhesion layer 53 1st electrode layer 54 Piezoelectric layer 55 2nd electrode layer 100 Inkjet head 102 Pressure chamber 102a Partition wall 103 1st electrode layer (individual electrode)
104 Orientation control layer 105 Common liquid chamber 106 Supply port 107 Ink flow path 108 Nozzle hole 109 Adhesive 110 Piezoelectric layer 111 Vibration layer 112 Second electrode layer (common electrode)
113 Middle layer (vertical wall)
114 Adhesive 120 Substrate (for film formation)
121 Adhesion layer 130 Substrate (for pressure chamber member)
A Pressure chamber member B Actuator part C Ink channel member D Nozzle plate

Claims (12)

In a piezoelectric thin film element comprising: a piezoelectric layer formed of an oxide containing Pb having a perovskite crystal structure; and an electrode layer formed on each layer surface on both sides in the thickness direction of the piezoelectric layer.
The piezoelectric layer is formed such that the residual strain has a first value larger than a predetermined value and a second value smaller than the predetermined value depending on a voltage application direction. Thin film element. 2. The piezoelectric device according to claim 1, wherein the first value is a value exceeding 2.5 × 10 ⁻⁴ , and the second value is a value ^less than 2.5 × 10 ^−4. Thin film element. 2. The piezoelectric thin film element according to claim 1, wherein the piezoelectric layer is preferentially oriented in one of a <111> plane and a <001> plane. 2. The piezoelectric thin film element according to claim 1, wherein a film thickness of the piezoelectric layer is in a range of 1 μm to 10 μm. 2. The piezoelectric thin film element according to claim 1, wherein the piezoelectric layer has a columnar structure grown in a thickness direction, and a columnar particle diameter thereof is in a range of 0.1 μm to 0.8 μm. The piezoelectric layer has a columnar structure grown in a thickness direction, and a ratio between a particle diameter and a film thickness of the columnar particles is within a range of 1/2 to 1/100. 2. The piezoelectric thin film element according to 1. 2. The piezoelectric thin film element according to claim 1, wherein the piezoelectric layer has a columnar structure grown in a thickness direction, and no foreign matter exists between the columnar particles. 2. The piezoelectric thin film element according to claim 1, wherein the piezoelectric layer is not subjected to polarization treatment at a high temperature after being formed. 2. The piezoelectric thin film element according to claim 1, wherein the piezoelectric layer is produced by a sputtering method. 2. The thin film actuator using the piezoelectric thin film element according to claim 1, wherein a voltage application direction during driving is a direction in which the residual strain has the first value. The piezoelectric thin film element according to claim 1,
A diaphragm layer provided on the surface of one of the electrodes of the piezoelectric thin film element;
A pressure chamber that is bonded to a surface of the diaphragm layer opposite to the piezoelectric thin film element and that discharges ink in accordance with a displacement of the diaphragm layer in a layer thickness direction due to a piezoelectric effect of the piezoelectric thin film element; ,
An ink jet head comprising: An inkjet head according to claim 11;
Relative movement means for relatively moving the inkjet head and the recording medium;
When the ink jet head is moved relative to the recording medium by the relative moving means, the ink in the pressure chamber is ejected to the recording medium from a nozzle hole provided in the ink jet head so as to communicate with the pressure chamber. Means for driving the piezoelectric thin film element according to claim 1, wherein the inkjet head is provided to perform
An ink jet recording apparatus comprising:

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