JP5707907B2 - Piezoelectric actuator, droplet discharge head, and droplet discharge device - Google Patents

Description

  The present invention relates to a piezoelectric actuator using a ferroelectric material as a material, a droplet discharge head using the piezoelectric actuator, and an inkjet recording apparatus or display device for printing applications using the droplet discharge head. Therefore, the present invention relates to a droplet discharge device for discharging industrial materials.

  In recent years, piezoelectric inkjet heads used as inkjet actuators have been accelerated in the trend toward higher density, and thin-film piezoelectric elements have been changed from conventional methods using stacked piezoelectric elements (see, for example, Patent Document 1). A method of forming on a diaphragm (for example, see Patent Document 2) is being transferred. In the latter method, a diaphragm made of an insulator is formed on a silicon (Si) substrate on which an ink liquid chamber is formed, and a piezoelectric body (piezoelectric element) sandwiched between electrodes is disposed on the opposite side of the ink liquid chamber. It becomes the composition to do. In this system, a voltage is applied to the upper and lower electrodes, and the deformation of the piezoelectric body corresponding to the voltage is transmitted to the ink in the ink liquid chamber via the diaphragm, and the compressed ink in the ink chamber is a nozzle. It discharges from the nozzle hole formed in the board.

In addition, ferroelectric memories using the same material system and the same electrode configuration have been developed. Ferroelectric memory is said to be FeRAM (Ferroelectric Random Access Memory), and it is said that high-speed operation similar to DRAM can be expected because the polarization inversion time of the dielectric film is fast (less than 1 ns) as a nonvolatile semiconductor memory.
Although the application of the device is different, the inkjet actuator and the ferroelectric memory are the same in that the driving voltage is repeatedly applied, and it can be said that the device has a common problem of durability due to the repetition of the driving voltage.

  Here, as means for improving fatigue characteristics related to durability, (i) improvement by the material of the piezoelectric body itself (for example, refer to Patent Document 3), (ii) improvement by processing method (for example, Patent Document 4) (Iii) by improvement of an electrode such as an oxide electrode (see, for example, Patent Documents 5 and 6), (iv) by insertion of a barrier layer (for example, see Patent Document 7), and the like.

Incidentally, in the above-mentioned Patent Document 3, a lower electrode film is formed, and then a rapid heating process is performed on the lower electrode film, and then a ferroelectric film is formed on the lower electrode film. A semiconductor manufacturing method in which an upper electrode film is formed on a ferroelectric film is described.
Patent Document 4 discloses a method for forming a ferroelectric device that employs RTA (Rapid Thermal Anneal).
Patent Document 5 discloses a ferroelectric device in which the first barrier layer on the second electrode layer is formed of IrO ₂ .
In Patent Document 6, the SrRuO ₃ film in which the upper electrode is formed on the side close to the dielectric film and the conductive film formed using a conductive material different from SrRuO ₃ on the side far from the dielectric film are disclosed. The constituent semiconductor is described.
Patent Document 7 describes a semiconductor in which a barrier film (TiAlN film, TiN film, etc.) is formed on the entire lower surface of a lower electrode.

  An object of the present invention is to provide a piezoelectric actuator having a small characteristic deterioration with respect to repeated application of a drive voltage, a droplet discharge head using the piezoelectric actuator, and a droplet discharge device.

As described above, in particular, in the ferroelectric memory, the fatigue characteristic is an important item in that data reading / writing is repeated 1 × 10 ¹⁰ times. It is well known that the fatigue characteristics are improved by the approach of the oxide electrode as compared with the case of directly using the Pt electrode. However, even if these conventional techniques are used, the fatigue characteristics are decreasing, and there is a problem that the deterioration of the fatigue characteristics cannot be suppressed even by these conventional techniques. The situation is the same for piezoelectric actuators. In addition, as described above, the deterioration mechanism is that oxygen atoms in the piezoelectric body are pulled in the positive direction by applying voltage during driving, and the concentration decreases near the electrodes and oxygen vacancies increase. There is a problem in getting it. In the process, the same is considered even when an oxide electrode is used.

  The present inventor has been made in view of such circumstances, and a barrier layer having a specific configuration having characteristics equal to or higher than that of an oxide electrode with respect to repeated fatigue characteristics of driving voltage of an electronic device using a piezoelectric body. It has been found that a good effect (improvement of fatigue characteristics) is brought about by being provided in contact with the piezoelectric film. The present invention has been made based on these findings. According to the present invention, the following invention is provided.

(1) A piezoelectric actuator in which a vibration layer film, a first electrode film, a first barrier layer film, a piezoelectric film, a second barrier layer film, and a second electrode film are laminated in this order on a substrate. The piezoelectric film is made of lead zirconate titanate, and the second barrier layer film is made of at least one metal element selected from Ti, Ta, Zr, V, Nb, and Mo, an oxygen element, and a carbon element. A piezoelectric actuator characterized in that the proportion of metal carbide in the material constituting the second barrier layer film is 20 mol% or more.
(2) The piezoelectric actuator according to (1) above the material constituting the first layer film is characterized in that it is a LaNiO _3.
( 3 ) A droplet discharge head comprising the piezoelectric actuator according to any one of (1) to (2 ) above.
( 4 ) A droplet discharge apparatus comprising the droplet discharge head described in (3 ) above.

  In the present invention, by using a material composed of at least one metal selected from Ti, Ta, Zr, V, Nb, and Mo and oxygen and carbon as the second barrier layer, against the repeated application of the driving voltage. It was possible to achieve the formation of an element with small characteristic deterioration. The reason why this effect can be exhibited is that it has a good barrier property against the movement of Pb and the like, and is a material more stable than the oxide electrode at the electrode interface where oxygen moves, and PZT (lead zirconate titanate) and commonly used Pt, This is considered to be due to excellent adhesion to a metal electrode such as Ir and a material having a small electric resistance.

It is the schematic of the piezoelectric actuator of this invention. It is the schematic of the droplet discharge head provided with the piezoelectric actuator of this invention. It is a disassembled perspective view of the droplet discharge head of this invention. It is a figure which shows the droplet discharge apparatus (inkjet recording device) which mounts the droplet discharge head (inkjet head) of this invention. It is a figure which shows the droplet discharge apparatus (inkjet recording device) which mounts the droplet discharge head (inkjet head) of this invention. It is a figure which shows the specific resistance of the target by a mixing ratio regarding the composition amount of a carbide | carbonized_material and an oxide.

  The present inventor has a good barrier property as the second barrier layer, is more stable than the oxide electrode at the electrode interface where oxygen moves, and has good adhesion to PZT and commonly used metal electrodes such as Pt and Ir. In addition, a material having a low electric resistance was selected from several simple metals, oxides, carbides and nitrides, and their melting points were examined (Table 1).

  As can be seen from Table 1, carbides have higher melting points than oxides and are excellent in thermal stability. The fact that it is thermally stable is considered to be chemically stable in many materials, has little interaction with substances, and is effective as a second barrier layer. However, on the other hand, carbides are not necessarily good in adhesion to many substances, for example, as used as a mold material when molding a glass material. For example, TiC or the like used as a metal tool is formed at a high temperature using a special forming method such as ion plating on a metal tool to ensure adhesion. The reason why the film is formed by using such a method is that if it is formed normally, sufficient adhesion cannot be obtained, and film peeling occurs when it is used as a tool.

  Therefore, the present inventor used a material for forming the second barrier layer in a mixture of these carbides and oxides as a method for improving adhesion. It was confirmed that a barrier layer having chemical stability and adhesion can be obtained by using a mixture. The carbon content can be changed depending on conditions such as the type of piezoelectric material used and the type of electrode material, and the content is a design matter for establishing the process.

  Furthermore, the melting points of oxide electrodes that have been conventionally known were also investigated. The results are listed in Table 2. Even when these melting points are compared, many carbides have melting points higher than those of the oxide electrode materials shown in Table 2. That is, it can be judged that it is chemically stable.

In the present invention derived from such research and examination , the vibration layer film, the first electrode film, the first barrier layer film, the piezoelectric film, the second barrier layer film, and the second electrode film are formed on the substrate. Piezoelectric actuators laminated in order, wherein the piezoelectric film is made of lead zirconate titanate, and the second barrier layer film is at least one metal selected from Ti, Ta, Zr, V, Nb, Mo It is characterized in that the proportion of the metal carbide in the material which is composed of an element, oxygen element and carbon element and which constitutes the second barrier layer film is 20 mol% or more .

Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 shows a schematic diagram of the piezoelectric actuator of the present invention. A piezoelectric film 60 having an electromechanical conversion effect sandwiched between the first barrier layer film 10 and the lower electrode 50 and the second barrier layer film 11 and the upper electrode 70 is formed on the substrate 30. Then, a part of the vibration layer film integrated with the substrate is deformed. In the figure, reference numeral 40 denotes a vibration layer film, and 51 denotes an electrode adhesion layer. Here, the vibration layer film 40 formed between the substrate 30 and the electrode adhesion layer 51 is, for example, a SiO ₂ insulating film formed by thermally oxidizing the surface of the Si substrate material. The electrode adhesion layer 51 formed between the vibration layer film 40 and the lower electrode 50 is formed of a metal oxide film because it bears the mechanical strength of the piezoelectric actuator.

  Furthermore, as shown in FIG. 2, when a pressure chamber 31 is formed in a part of the substrate 30 corresponding to a piezoelectric element (piezoelectric actuator) and the nozzle plate 20 is joined, the nozzle hole 21 is applied by applying an electric field to the electrodes. A liquid droplet discharge head (inkjet head) that discharges the liquid (ink) in the pressure chamber 31 is configured.

  The substrate 30 is not particularly restricted as long as it is excellent in workability, has high mechanical strength, and is inactive at the heat treatment / firing temperature. It may be composed of a structure made of a plurality of materials, but is preferably a Si substrate.

The material of the electrodes 50 and 70 may be a conductor that can withstand a high-temperature oxidizing atmosphere at a heat treatment / firing temperature, high-temperature melting precious metals such as platinum and platinum group elements (Pd, Rh, Ir, Ru), and their An electrode material mainly composed of an alloy is most preferable from the viewpoint of stability.
The film thickness of the lower electrode 50 is 100 to 250 nm. The formation conditions of the lower electrode 50 are substrate temperature: 250 to 350 ° C., RF input power: 300 to 500 W, Ar gas pressure: 2 × 10 ^{−3 to} 5 × 10 ⁻² Torr.
The film thickness of the upper electrode 70 is 50 to 150 nm. The formation conditions of the upper electrode 70 are substrate temperature: 250 to 350 ° C., RF input power: 300 to 500 W, Ar gas pressure: 2 × 10 ^{−3 to} 5 × 10 ⁻² Torr.
In the above description, the conditions when the sputtering method is used for electrode formation are shown. As the sputtering apparatus, a sputtering apparatus manufactured by Canon Anelva (model: E-401S) was used. This device has a target size of 4 inches φ, and the input power described above is the power applied to the size of 4 inches φ. If the target size changes, the condition can be changed by increasing or decreasing the area ratio. Is possible.

  The piezoelectric film 60 is preferably a PZT ceramic, and may be a thick film obtained by screen printing and sintering, or a thin film formed by sputtering, vapor deposition, or a sol-gel method. The film thickness of the piezoelectric film 60 is 300 nm to 3 μm.

The second barrier layer film 11 serves to prevent the diffusion of lead from the PZT of the piezoelectric film 60 from spreading to the upper electrode 70.
The material of the second barrier layer film 11 is a material that has good barrier properties and is more stable than an oxide electrode at the electrode interface through which oxygen moves, and has good adhesion to PZT and commonly used metal electrodes such as Pt and Ir. In addition, a material having an excellent electrical resistance is selected. Specifically, a material composed of at least one metal selected from Ti, Ta, Zr, V, Nb, and Mo, oxygen, and carbon is used.
The film thickness of the second barrier layer film 11 may be thinner than the known adhesion layer film thickness range because of high chemical stability, and the film thickness of the second barrier layer is about 2 to 50 nm, preferably It is 2-30 nm, More preferably, it is 2-20 nm. If it is less than 2 nm, it is difficult to uniformly cover the entire surface as a film, and if it exceeds 50 nm, displacement of the piezoelectric film starts to be inhibited.
In addition, the second barrier layer film 11 is sintered in the form of a sputtering target by using the powder of the material, and after homogeneous mixing, by the HIP method (method of sintering under isotropic pressure using a gas pressure). Is formed by sputtering. The formation conditions of the second barrier layer 11 are: substrate temperature: 200 to 300 ° C., RF input power: 300 to 500 W, Ar gas pressure: 2 × 10 ^{−3 to} 5 × 10 ⁻² Torr.

The first barrier layer film 10 serves to stop the diffusion of lead from the PZT of the piezoelectric film 60 from spreading to the vibration layer film (SiO ₂ insulating film) 40.
As the material of the first barrier layer film 10, LaNiO ₃ , IrO ₂ , SrO, SrRuO ₃ , CaRuO ₃ , BaRuO ₃ , LaCuO ₃ , LaCoO ₃ , which have good crystal lattice matching with the piezoelectric film 60 to be laminated next. ₃ , LaTiO ₃ , LuNiO ₃ , CaIrO ₃ , CaRuO ₃ , and the like are preferable. A particularly preferred material is LaNiO ₃ .
The film thickness of the first barrier layer film 10 is 10 to 100 nm, preferably 30 to 80 nm. If the thickness is less than 10 nm, a sufficient barrier property as a film may not be obtained. If the thickness exceeds 100 nm, it takes too much time for etching and the process time increases.
The formation conditions of the first barrier layer film 10 are substrate temperature: 250 to 550 ° C., RF input power: 300 to 500 W, Ar gas pressure: 2 × 10 ^{−3 to} 5 × 10 ⁻² Torr.

The electrode adhesion layer film 51 is provided as necessary for improving the adhesion between the lower electrode 50 and the vibration layer film (SiO ₂ insulating film) 40. As a material of the electrode adhesion layer film 51, a metal oxide film having sufficient resistance at a PZT firing temperature, low reactivity with respect to lead, and high mechanical strength, for example, MgO, GeO ₂ , Y ₂ O ₃ , A partially stabilized or fully stabilized zirconium oxide film containing at least one oxide of Al ₂ O ₃ , SrTiO ₃ , MgO—Al ₂ O ₃ , yttrium, cerium, magnesium and calcium having higher toughness. It is also preferable to use it.
The film thickness of the electrode adhesion layer film 51 is 100 to 600 nm, and more preferably 300 to 400 nm in order not to cause stress distribution in the film. The formation conditions of the adhesion layer film 51 are: substrate temperature: 300 to 500 ° C., RF input power: 300 to 500 W, Ar gas pressure: 3 × 10 ^{−3 to} 7 × 10 ⁻³ Torr.

  FIG. 3 is an exploded perspective view of the droplet discharge head of the present invention, and a part thereof is shown in a sectional view. The present embodiment is a side shooter type liquid discharge head that discharges ink droplets from nozzle holes provided on the surface of the substrate, and the second substrate 2 that becomes the nozzle plate 20 having the nozzle holes 21 for discharging ink. A first substrate serving as a liquid chamber substrate on which an ejection chamber (ink liquid chamber) 31, a vibration plate, and a piezoelectric element are formed, and a third substrate serving as a protective substrate provided with a space 74 for protecting the piezoelectric element. It has a laminated structure in which these three substrates are stacked.

In the first substrate 1, the vibration layer film 40 having a structure in which a laminated film is formed on the silicon substrate 30 is formed, for example, by thermally oxidizing the surface of a Si substrate material (SiO ₂ insulating film) 40. It has been. On one surface of the silicon substrate 30, a vibration layer film 40, a platinum film serving as a lower electrode 50, a first barrier layer 10, a piezoelectric layer 60, a second barrier layer 11, and an upper electrode 70 are laminated. Yes. In addition, a discharge chamber 31, a fluid resistance portion 32 and a common liquid chamber 33 communicating with the discharge chamber 31 are formed on the other surface by etching the silicon substrate 30.

  The second substrate 2 is formed by a nickel high speed electroforming method and has a thickness of 30 μm. The second substrate 2 constitutes the wall surface of the discharge chamber 31 formed in the first substrate 1, and the nozzle hole 21 is provided corresponding to each discharge chamber 31.

  The third substrate 3 is provided with a space 74 for securing and protecting an operation area of the piezoelectric element constituted by the lower electrode 50, the piezoelectric film 60, and the upper electrode 70.

  The operation of this droplet discharge head will be described. Ink is supplied into each discharge chamber 31 from the ink supply hole 34 via the common liquid chamber 33. In a state where each discharge chamber 31 is filled with ink, a pulse voltage having a predetermined pulse width of 20 V is applied between the upper electrode 70 and the lower electrode 50 of the piezoelectric element. As a result, the piezoelectric element that is deformed in the transverse vibration mode contracts, and the entire vibration layer film 40 is deformed so as to be convex toward the discharge chamber 31 side. As a result, the volume in the discharge chamber 31 decreases, the pressure in the discharge chamber 31 increases rapidly, and ink droplets (not shown) are discharged from the nozzle holes 21 toward the recording paper. By continuously applying this pulse voltage, ink droplets can be continuously discharged from the nozzle hole 21.

Next, the droplet discharge device according to the present invention will be described.
A droplet discharge apparatus according to the present invention is an apparatus that forms an image by discharging (also referred to as jetting) droplets, and includes the above-described droplet discharge head of the present invention.
Here, with reference to FIGS. 4 and 5, an ink jet recording apparatus which is a liquid droplet ejection apparatus equipped with the liquid droplet ejection head of the present invention will be described as an example. 4 is an explanatory perspective view of the recording apparatus, and FIG. 5 is an explanatory side view of a mechanism portion of the recording apparatus.

  This ink jet recording apparatus includes a carriage movable in the main scanning direction inside the recording apparatus main body 81, a recording head composed of an ink jet head embodying the present invention mounted on the carriage, an ink cartridge for supplying ink to the recording head, and the like. A sheet feeding cassette (or a sheet feeding tray) 84 on which a large number of sheets 83 can be stacked from the front side is detachably attached to the lower part of the apparatus main body 81. The manual feed tray 85 for manually feeding the paper 83 can be opened, the paper 83 fed from the paper feed cassette 84 or the manual feed tray 85 is taken in, and the printing mechanism 82 After recording a required image, the image is discharged to a paper discharge tray 86 mounted on the rear side.

  The print mechanism 82 holds a carriage 93 slidably in the main scanning direction by a main guide rod 91 and a sub guide rod 92 which are guide members horizontally mounted on left and right side plates (not shown). (Y), cyan (C), magenta (M), and black (Bk) ink jet heads according to the present invention for ejecting ink droplets of each color (head) (recording head) 94 is provided with a plurality of ink ejection openings (nozzles). They are arranged in a direction crossing the main scanning direction, and are mounted with the ink droplet ejection direction facing downward. Further, each ink cartridge 95 for supplying ink of each color to the recording head 94 is replaceably mounted on the carriage 93.

  The ink cartridge 95 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside, and the capillary force of the porous body. Thus, the ink supplied to the inkjet head is maintained at a slight negative pressure. Further, although the heads 94 of the respective colors are used here as the recording heads, a single head having nozzles for ejecting ink droplets of the respective colors may be used.

  Here, the carriage 93 is slidably fitted to the main guide rod 91 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 92 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 93 in the main scanning direction, a timing belt 100 is stretched between a drive pulley 98 and a driven pulley 99 that are rotationally driven by a main scanning motor 97, and the timing belt 100 is moved to the carriage 93. The carriage 93 is driven to reciprocate by forward and reverse rotation of the main scanning motor 97.

  On the other hand, in order to convey the paper 83 set in the paper feed cassette 84 to the lower side of the head 94, the paper feed roller 101 and the friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84 and the paper 83 are guided. A guide member 103, a transport roller 104 that reverses and transports the fed paper 83, a transport roller 105 that is pressed against the peripheral surface of the transport roller 104, and a leading end that defines a feed angle of the paper 83 from the transport roller 104 A roller 106 is provided. The transport roller 104 is rotationally driven by a sub-scanning motor 107 through a gear train.

  A printing receiving member 109 is provided as a paper guide member that guides the paper 83 sent from the transport roller 104 below the recording head 94 in accordance with the movement range of the carriage 93 in the main scanning direction. A conveyance roller 111 and a spur 112 that are rotationally driven to send the paper 83 in the paper discharge direction are provided on the downstream side of the printing receiving member 109 in the paper conveyance direction, and the paper 83 is further delivered to the paper discharge tray 86. A roller 113 and a spur 114, and guide members 115 and 116 that form a paper discharge path are disposed.

  At the time of recording, the recording head 94 is driven according to the image signal while moving the carriage 93, thereby ejecting ink onto the stopped sheet 83 to record one line. Record the line. Upon receiving a recording end signal or a signal that the trailing edge of the paper 83 has reached the recording area, the recording operation is terminated and the paper 83 is discharged.

  Further, a recovery device 117 for recovering defective ejection of the head 94 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 93. The recovery device 117 includes a cap unit, a suction unit, and a cleaning unit. The carriage 93 is moved to the recovery device 117 side during printing standby and the head 94 is capped by the capping means, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  When a discharge failure occurs, the discharge port (nozzle) of the head 94 is sealed with a capping unit, and bubbles and the like are sucked out from the discharge port with the suction unit through the tube. Is removed by the cleaning means to recover the ejection failure. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.

  As described above, since the inkjet head embodying the present invention is mounted in this inkjet recording apparatus, there is no ink droplet ejection failure due to vibration plate drive failure, stable ink droplet ejection characteristics are obtained, and image quality is improved. improves.

  In the above-described embodiment, the example in which the ink jet head is applied as a liquid droplet ejecting head has been described. The present invention can also be applied to other droplet discharge heads such as a droplet discharge head (spotter) that discharges the sample as droplets.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

  In the configuration shown in FIG. 1, an example is shown in which a piezoelectric actuator and a droplet discharge head having a second barrier layer 11 made of a predetermined metal oxide and carbide are manufactured.

[Example 1]
A piezoelectric actuator and a piezoelectric actuator structure (droplet ejection head 1) were produced by the following procedure.
First, a SiO ₂ insulating film was formed by thermally oxidizing the surface of the Si (100) substrate material. This SiO ₂ film becomes the diaphragm 40. The SiO ₂ film thickness at this time was 2 μm.
Next, an electrode adhesion layer 51 serving as an adhesion layer with the lower electrode 50 was formed on the SiO ₂ / Si substrate. The formation conditions of the electrode adhesion layer 51 are as follows: substrate temperature: 300 ° C., RF input power: 500 W, Ar gas pressure: 5 × 10 ⁻³ Torr, and the formed film thickness is 50 nm.
Next, a Pt electrode as the lower electrode 50 was formed with a film thickness of 200 nm. The formation conditions of the lower electrode 50 were as follows: substrate temperature: 300 ° C., RF input power: 500 W, Ar gas pressure: 3 × 10 ^{−3 to} 5 × 10 ⁻³ Torr. Thereby, the (111) plane of the lower electrode 50 is oriented in the film thickness direction.
Further, on the lower electrode film 50, a LaNiO ₃ having a good lattice matching with the piezoelectric film 60 to be laminated next was formed as a first barrier layer 10 with a thickness of 100 nm. The formation conditions of the first barrier layer 10 are substrate temperature: 300 ° C., RF input power: 300 W, Ar gas pressure: 4.2 × 10 ⁻³ Torr, oxygen gas pressure: 8 × 10 ⁻⁴ Torr. The reason for introducing oxygen gas is to reduce oxygen vacancies in the LaNiO ₃ film.

Further, a lead titanate-based piezoelectric thin film that becomes the piezoelectric film 60 was formed on the first barrier layer 10 by a sol-gel method. Specifically, lead acetate trihydrate, titanium isopropoxide, and zirconium propoxide were used as starting materials, and 2 methoxyethanol was used as a solvent.
First, lead acetate trihydrate is dissolved in 2 methoxyethanol and distilled at 137 ° C. to discharge crystal water. Next, an alkoxide of Zr and Ti weighed so as to have a predetermined composition (in this case, the mass ratio is Pb / Ti / Zr = 100/47/53) is added to the dehydrated lead acetate solution at 127 ° C. A composite alkoxide solution was prepared in Pb, Ti, and Zr by refluxing at a low temperature. Using this solution, a thin film was formed by spin coating at 3000 rpm on a Pt / Ti / SiO ₂ / Si substrate having a Pt coating layer with the (111) plane oriented in the film thickness direction. Next, after drying this, after repeating the organic pyrolysis 10-25 times under two kinds of temperature conditions of 400 ° C. and 450 ° C., respectively, for 3 minutes, 700 ° C. at a heating rate of 30 ° C./sec, Baking for 5 minutes was performed in an O ₂ atmosphere, and Pb (Ti _0.47 Zr _0.53 ) O ₃ having a thickness of 300 nm to 1 μm.
A thin film was formed on a laminated thin film made of a Pt / Ti / SiO ₂ / Si substrate.

Here, 30 mol% TiO ₂ and 70 mol% TiC material powder were used as the second barrier layer material, and after homogeneous mixing, sintered into a sputtering target by the HIP method, the composition was (TiO ₂ ) _0.3 A sputtering target of (TiC) _0.7 was formed, and a second barrier layer was formed by sputtering using this target.
In the target preparation state, it is a mixture of oxide and carbide, and it seems that the state does not change even after sintering, but in the state of film, a random network is formed, and X-ray diffraction measurement Diffraction peaks did not appear even after performing. Table 1 shows the target preparation amounts of oxide and carbide, but it has been confirmed that the formed thin film does not have a crystal structure.
Here, the formation conditions of the second barrier layer 11 are: substrate temperature: 300 ° C., RF input power: 300 W, Ar gas pressure: 5 × 10 ⁻³ Torr, and the formed film thickness is 10 nm.

After forming the second barrier layer, a Pt electrode to be the upper electrode 70 was formed with a film thickness of 100 nm. The formation conditions of the upper electrode 70 are: substrate temperature: 300 ° C., RF input power: 500 W, Ar gas pressure: 3-5 × 10 ⁻³ Torr.
Then, after forming a resist pattern using a photolithographic technique, etching of the laminated structure and resist ashing were performed in a cross-sectional shape as shown in FIG. The size of the upper electrode in FIG. 1 was a strip shape of 45 μm × 1 mm.

After forming to the above state, a driving voltage was repeatedly applied under the following conditions for a fatigue test after polarization treatment without forming a passivation film for protecting the element. The second barrier layer side was set to a positive potential, and the first barrier layer side was set to a negative potential (ground potential).
The evaluation results are as shown in Table 3. It was found that up to 10 ¹² times can be secured with attenuation within 10% of the initial value under the above conditions.

<< Polarization conditions >>
Applied voltage 40V (Voltage is gradually increased from 0V in 3min and held for 1min.
Slowly lower the voltage to 0V in 3 min. )
Evaluation after polarization Measured with the initial value of the capacitance measured at 1 kHz square wave of the applied voltage of the repeated drive voltage test between the upper and lower electrodes.
<< Test conditions for repeated application of drive voltage >>
Applied voltage DC 0-30V Square wave (Upper electrode is positive potential)
Application period 100 kHz
Duty 50% (time ratio of positive potential application)
Evaluation during the test The initial value of capacitance after polarization was normalized as 1, and the same evaluation as the evaluation after polarization was performed at each point for each number of applications, and the attenuation rate was observed. The point at which the initial value was attenuated by 10% after normalization was taken as the fatigue evaluation point.
As a result, it was found that up to 10 ¹² times can be secured with attenuation within 10% of the initial value under the above conditions.

[Example 2]
In Example 1, the composition of the sputtering target was changed to (TaO ₂ ) _0.2 (TaC) _0.8 instead of (TiO ₂ ) _0.3 (TiC) _0.7 , and the rest was the same as in Example 1. Thus, the piezoelectric film laminated structure of FIG. 1 was produced, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3.

Example 3
In Example 1, the composition of the sputtering target was changed to (ZrO ₂ ) _0.5 (ZrC) _{0.5 in place} of (TiO ₂ ) _0.3 (TiC) _0.7 , and the rest was the same as in Example 1. Thus, the piezoelectric film laminated structure of FIG. 1 was produced, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3.

Example 4
In Example 1, the composition of the sputtering target was changed to (VO ₂ ) _0.2 (VC) _0.8 instead of (TiO ₂ ) _0.3 (TiC) _0.7 , and the rest was the same as in Example 1. Thus, the piezoelectric film laminated structure of FIG. 1 was produced, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3.

Example 5
In Example 1, the composition of the sputtering target was changed to (Nb ₂ O ₅ ) _0.3 (NbC) _0.7 instead of (TiO ₂ ) _0.3 (TiC) _0.7 , and other than that, Example 1 1 was fabricated, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3.

Example 6
In Example 1, the composition of the sputtering target was changed to (MoO ₂ ) _0.05 (MoC) _0.95 instead of (TiO ₂ ) _0.3 (TiC) _0.7 , and other than that, the same as in Example 1 Thus, the piezoelectric film laminated structure of FIG. 1 was produced, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3.

[Comparative Example 1]
In Example 1, except that the second barrier layer (TiO ₂ ) _0.3 (TiC) _0.7 was not provided, and the upper electrode 70 was formed directly on the piezoelectric film 60, Example 1 A piezoelectric film laminated structure was produced in the same manner as described above, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3. The result is a 10 ⁹ times the number of repetitions of a 10% attenuation value of the initial value was 2 to 3 orders of magnitude lower value than that of Example 1.

[Comparative Example 2]
In Example 1, instead of using (TiO ₂ ) _0.3 (TiC) _0.7 , a piezoelectric film laminated structure was produced in the same manner as in Example 1 except that a single TiC film was formed. However, after the formation of the upper electrode, peeling of the film occurred between the dielectric film and the TiC film in the photolithography process, and the subsequent process was abandoned. The evaluation result “x” in Table 3 means that evaluation could not be performed because film peeling occurred with the ferroelectric.

[Comparative Example 3]
In Example 1, instead of using (TiO ₂ ) _0.3 (TiC) _0.7 , (SiO ₂ ) _0.3 (SiC) _0.7 was formed in the same manner as in Example 1 except that A piezoelectric film laminated structure was prepared, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3. Further, in this example, in the Si oxide and carbide, circular peeling was observed. The evaluation result “x” in Table 3 means that evaluation could not be performed because film peeling occurred in a circular shape between the ferroelectric and the upper electrode.

[Comparative Example 4]
Example 1 is the same as Example 1 except that (Cr ₂ O ₃ ) _0.3 (CrC) _0.7 was formed instead of using (TiO ₂ ) _0.3 (TiC) _0.7. Thus, a piezoelectric film laminated structure was prepared, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3. The evaluation result “x” in Table 3 means that the film could not be evaluated because the film peeled indefinitely due to the stress of the film.

[Comparative Example 5]
In Example 1, instead of (TiO ₂ ) _0.3 (TiC) _0.7 , LaNIO ₃ was formed as a second barrier layer (however, the film thickness was set to 100 nm). Similarly, a piezoelectric film laminated structure was produced, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3.

[Comparative Example 6]
In Example 1, instead of (TiO ₂ ) _0.3 (TiC) _0.7 , LaNIO ₃ was formed as a second barrier layer (however, the film thickness was set to 100 nm). Similarly, a piezoelectric film laminated structure was produced, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3.

[Comparative Example 7]
In Example 1, instead of (TiO ₂ ) _0.3 (TiC) _0.7 , IrO ₂ was formed as a second barrier layer (however, the film thickness was set to 100 nm). Similarly, a piezoelectric film laminated structure was produced, and the same fatigue characteristic test as in Example 1 was evaluated. The evaluation results are summarized in Table 3.

As is apparent from Table 3, Examples 1 to 6 obtained repeated results of 1 × 10 ¹¹ times or more in each test, and were found to be satisfactory in characteristics.

Example 7
The specific resistance of the target according to the mixing ratio with respect to the composition amount of carbide and oxide was investigated. The results are shown in FIG. It can be seen that the carbide composition amount has an inflection point at 20 mol%, and the effect of mixing the carbide does not appear even in the specific resistance when the carbide composition amount is less than 20 mol%.

Example 8
By applying the piezoelectric actuator structures of Examples 1 to 6 to produce a droplet discharge head having the configuration shown in FIG. 4, fatigue deterioration does not occur due to the second barrier layer 11. A droplet discharge head having stable ink droplet discharge characteristics without defects could be obtained.
In addition, when these droplet discharge heads of Examples 1 to 6 are used as inkjet heads mounted on the inkjet recording apparatus of FIGS. 4 and 5, there is no ink droplet ejection failure due to drive failure, and stable ink droplet ejection. The characteristics were obtained, and good image quality was obtained without missing images.

(In FIGS. 1 and 2)
10 first barrier layer film 11 and the second barrier layer film 20 nozzle plate 21 nozzle holes 30 substrate 31 pressure chamber 40 diaphragm (SiO ₂ insulating film)
50 Lower electrode 51 Electrode adhesion layer 60 Piezoelectric film 70 Upper electrode (in FIG. 3)
DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 3rd board | substrate 20 Nozzle plate 21 Nozzle hole 30 Silicon substrate 31 Ejection port 32 Fluid resistance part 33 Common liquid chamber 34 Ink supply port 72 Protective substrate 73 Piezoelectric film 74 Space (FIG. 4 and 5)
81 Recording Device Body 82 Printing Mechanism Section 84 Paper Feed Cassette 85 Manual Tray 86 Paper Discharge Tray 91 Main Guide Rod 92 Subordinate Guide Rod 93 Carriage 94 Recording Head 95 Ink Cartridge 97 Main Scanning Motor 98 Drive Pulley 99 Driven Pulley 100 Timing Belt 101 Feed Paper roller 102 Friction pad 103, 115, 116 Guide member 104 Conveying roller 105, 111 Conveying roller 106 Leading roller 107 Sub-scanning motor 109 Print receiving member 112, 114 Spur 113 Discharged roller 117 Recovery device

JP 2001-063047 A JP 2004-349712 A JP 2005-101491 A JP 2009-016741 A JP 2001-007299 A JP 2000-208725 A JP 2007-088147 A

Claims (4)

A piezoelectric actuator in which a vibration layer film, a first electrode film, a first barrier layer film, a piezoelectric film, a second barrier layer film, and a second electrode film are laminated in this order on a substrate, The piezoelectric film is composed of lead zirconate titanate, and the second barrier layer film is composed of at least one metal element selected from Ti, Ta, Zr, V, Nb, and Mo, an oxygen element, and a carbon element, And the ratio of the metal carbide in the material which comprises this 2nd barrier layer film | membrane is 20 mol% or more, The piezoelectric actuator characterized by the above-mentioned . 2. The piezoelectric actuator according to claim 1, wherein a material constituting the first barrier layer film is LaNiO ₃ . A droplet discharge head comprising the piezoelectric actuator according to claim 1 . A droplet discharge apparatus comprising the droplet discharge head according to claim 3 .