JP4911289B2 - Actuator device, liquid jet head, and liquid jet device - Google Patents

Description

  The present invention relates to an actuator device having a piezoelectric element provided on a substrate via a vibration plate, a liquid ejecting head using the actuator device, and a liquid ejecting device.

  An actuator device including a piezoelectric element that is displaced by applying a voltage is mounted on, for example, a liquid ejecting head that ejects liquid droplets from a nozzle opening. As such a liquid ejecting head, for example, a part of a pressure generation chamber communicating with a nozzle opening is configured by a vibration plate, and the vibration plate is deformed by a piezoelectric element so as to pressurize ink in the pressure generation chamber to form a nozzle opening. Inkjet recording heads that discharge ink droplets are known. Two types of ink jet recording heads have been put into practical use: those equipped with a piezoelectric actuator device in a longitudinal vibration mode that extends and contracts in the axial direction of the piezoelectric element, and those equipped with a piezoelectric actuator device in a flexural vibration mode. Yes.

  Also, as an actuator device in a flexural vibration mode, a uniform piezoelectric layer is formed over the entire surface of the diaphragm by a film forming technique, and this piezoelectric material layer is cut into a shape corresponding to the pressure generating chamber by a lithography method. One in which a piezoelectric element is formed so as to be independent for each pressure generating chamber has been proposed. This eliminates the need to affix the piezoelectric element to the diaphragm, so that not only can the piezoelectric element be created by a precise and simple technique called lithography, but also the thickness of the piezoelectric element can be reduced. There is an advantage that high-speed driving is possible. However, a piezoelectric element manufactured by such a film forming technique and a lithography method has a problem that dielectric breakdown occurs when driving is repeated by applying a voltage to the piezoelectric element.

  In addition, the cause of dielectric breakdown is considered to be the influence of moisture (humidity) in the atmosphere, and as a countermeasure, there is one in which the entire piezoelectric element is covered with a protective film. By providing the protective film in this manner, the dielectric breakdown of the piezoelectric element can be prevented. Further, by providing the protective film, the rigidity of the diaphragm is substantially increased, and the diaphragm can be prevented from being broken or cracked due to deformation. However, there is a problem that the amount of displacement of the diaphragm due to the driving of the piezoelectric element is reduced.

  Further, there is a structure in which such a protective film is provided on a side surface portion of a piezoelectric element (piezoelectric vibrator), that is, a structure in which a window exposing the surface of the upper electrode is provided in the protective film (for example, Patent Document 1). reference). With such a structure, it is possible to suppress a decrease in the amount of displacement of the diaphragm due to driving of the piezoelectric element while preventing dielectric breakdown. However, problems such as breakage of the diaphragm and generation of cracks are likely to occur. Further, such a crack or the like of the diaphragm is particularly likely to occur along the width direction of the pressure generating chamber. That is, it is considered that cracks and the like are generated in the diaphragm due to the tensile stress in the longitudinal direction of the pressure generating chamber.

Japanese Patent No. 3552013 (FIG. 4 etc.)

  In view of such circumstances, the present invention provides an actuator device, a liquid ejecting head, and a liquid ejecting device that can prevent dielectric breakdown of a piezoelectric element, suppress a decrease in the amount of displacement of the diaphragm, and prevent destruction of the diaphragm. Is an issue.

A first aspect of the present invention that solves the above problems includes a piezoelectric element having a lower electrode, a piezoelectric layer, and an upper electrode, and a protective film that is made of an insulating material and is provided so as to cover the piezoelectric element. In the region of the protective film facing the upper electrode, a plurality of concave portions having a thickness of the protective film thinner than that of other portions are arranged in parallel in the width direction of the piezoelectric element, and the longitudinal direction of the piezoelectric element The length of each concave portion in the piezoelectric element is longer toward the central portion in the width direction of the piezoelectric element, and both end portions of each concave portion in the longitudinal direction of the piezoelectric element are on the width direction central portion side of the piezoelectric element. In the actuator device, the concave portion is located closer to the end portion in the longitudinal direction of the piezoelectric element.
In the first aspect, the rigidity of the diaphragm in the longitudinal direction of the pressure generation chamber is greater than the rigidity in the width direction of the pressure generation chamber. Therefore, it is possible to prevent the occurrence of dielectric breakdown, suppress a decrease in the amount of displacement of the diaphragm due to driving of the piezoelectric element, and prevent the diaphragm from being destroyed due to deformation of the piezoelectric element. Further, since stress gradually changes in the vicinity of the longitudinal end portion of the piezoelectric body active portion, occurrence of stress concentration in this portion is prevented. Thereby, destruction of a diaphragm can be prevented more reliably.

A second aspect of the present invention, the sum of the lateral direction of width of the piezoelectric element of the plurality of recesses, wherein the 60% or less 25% or more in the short direction of the width of the piezoelectric element The actuator device according to the first aspect.
In the second aspect, it is possible to more reliably prevent the diaphragm from being lowered and the diaphragm from being destroyed.

According to a third aspect of the present invention, in the actuator device according to the first or second aspect, the concave portion is a through-hole penetrating the protective film.
In the third aspect, a decrease in the displacement amount of the diaphragm is more reliably suppressed.

According to a fourth aspect of the present invention, in the actuator device according to any one of the first to third aspects, the protective film is made of an inorganic insulating material.
In the fourth aspect, dielectric breakdown of the piezoelectric element caused by moisture (humidity) in the atmosphere can be prevented more reliably.

According to a fifth aspect of the present invention, there is provided a liquid ejecting head including the actuator device according to any one of the first to fourth aspects.
In the fifth aspect, it is possible to realize a liquid ejecting head that is excellent in various characteristics such as droplet ejection characteristics and durability.

A sixth aspect of the present invention is a liquid ejecting head that ejects liquid in a pressure generating chamber from a nozzle opening by displacement of the actuator device, wherein both longitudinal ends of the piezoelectric element face the pressure generating chamber. In the liquid jet head according to the fifth aspect, the liquid jet head extends to the outside of the region.
In the sixth aspect, since only the rigidity of the diaphragm in the width direction of the pressure generation chamber substantially contributes to the deformation of the diaphragm, the displacement amount of the diaphragm is reduced by providing a plurality of recesses in the protective film. Less.

According to a seventh aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting head according to the fifth or sixth aspect.
In the seventh aspect, it is possible to realize a liquid ejecting apparatus with improved reliability and durability.

Hereinafter, the present invention will be described in detail based on embodiments.
FIG. 1 is an exploded perspective view showing a schematic configuration of an ink jet recording head according to an embodiment of the present invention, and FIG. 2 is a plan view of an essential part of the ink jet recording head and a sectional view taken along line AA ′. .

  As shown in the drawing, the flow path forming substrate 10 is made of a silicon single crystal substrate having a plane orientation (110) in this embodiment, and one surface thereof is made of silicon dioxide previously formed by thermal oxidation. An elastic film 50 of 5 to 2 μm is formed. In the flow path forming substrate 10, a plurality of pressure generating chambers 12 partitioned by a partition wall 11 are arranged in parallel in the width direction. In addition, a communication portion 13 is formed in a region outside the longitudinal direction of the pressure generation chamber 12 of the flow path forming substrate 10, and the communication portion 13 and each pressure generation chamber 12 are provided for each pressure generation chamber 12. Communication is made via a supply path 14. The communication portion 13 communicates with a reservoir portion of a reservoir forming substrate, which will be described later, and constitutes a part of a reservoir that serves as a common ink chamber for the pressure generation chambers 12. The ink supply path 14 is formed with a narrower width than the pressure generation chamber 12, and maintains a constant flow path resistance of ink flowing into the pressure generation chamber 12 from the communication portion 13.

  A nozzle plate 20 having a plurality of nozzle openings 21 is bonded to the opening surface side of the flow path forming substrate 10 via an insulating film 51 used as a mask when forming the pressure generating chamber 12 and the like. It is fixed by an agent, a heat welding film or the like. The nozzle plate 20 is made of glass ceramics, a silicon single crystal substrate, stainless steel, or the like.

On the other hand, an elastic film 50 made of silicon dioxide and having a thickness of, for example, about 1.0 μm is formed on the side opposite to the opening surface of the flow path forming substrate 10. For example, an insulator film 55 made of zirconium oxide (ZrO ₂ ) or the like and having a thickness of, for example, about 0.3 to 0.4 μm is laminated. Further, on the insulator film 55, the lower electrode film 60 with a thickness of, for example, about 0.1 to 0.2 μm, the piezoelectric layer 70 with a thickness of, for example, about 0.5 to 5 μm, and a thickness For example, the piezoelectric element 300 including the upper electrode film 80 of about 0.05 μm is formed. Here, the piezoelectric element 300 refers to a portion including the lower electrode film 60, the piezoelectric layer 70, and the upper electrode film 80. In general, one electrode of the piezoelectric element 300 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure generating chamber 12. For example, in this embodiment, the lower electrode film 60 is used as a common electrode for the piezoelectric element 300 and the upper electrode film 80 is used as an individual electrode for the piezoelectric element 300. Absent. In addition, here, the piezoelectric element 300 and the diaphragm that is displaced by driving the piezoelectric element 300 are collectively referred to as an actuator device. In the present embodiment, the elastic film 50, the insulator film 55, and the lower electrode film 60 function as a diaphragm.

  Hereinafter, the configuration of the piezoelectric element 300 will be described in more detail. In the present embodiment, as shown in FIG. 3, the lower electrode film 60 is formed in a region facing the pressure generation chamber 12 in the longitudinal direction of the pressure generation chamber 12, and is formed in a region corresponding to the plurality of pressure generation chambers 12. It is provided continuously. Further, the lower electrode film 60 extends to the vicinity of the end of the flow path forming substrate 10 outside the row of the pressure generating chambers 12, and the connection wiring 210 extending from the driving IC 200 described later is provided at the tip of the lower electrode film 60. The connecting portion 60a is connected. The piezoelectric layer 70 and the upper electrode film 80 are provided in a region facing the pressure generation chamber 12 in the width direction of the pressure generation chamber 12, but in the longitudinal direction of the pressure generation chamber 12, Outside the end, in this embodiment, the piezoelectric layer 70 and the upper electrode film 80 extend to the outside of the end of the pressure generating chamber 12, and the end face of the lower electrode film 60 is covered by the piezoelectric layer 70. ing. That is, the piezoelectric active part 320 that is a substantial driving part of the piezoelectric element 300 is provided in a region facing the pressure generating chamber 12, and the piezoelectric active layer 320 has the piezoelectric layers 70 on both outer sides. Each of the piezoelectric non-active parts 330 that are not driven is provided and extends to the outside of the pressure generating chamber 12. The piezoelectric element 300 is patterned so that the width becomes narrower toward the upper electrode film 80 side, and each side end surface is an inclined surface.

  In addition, a lead electrode 90 made of, for example, gold (Au) or the like is connected near one end of the upper electrode film 80 constituting each piezoelectric element 300. In this embodiment, the lead electrode 90 extends from the piezoelectric inactive portion 330 outside the pressure generating chamber 12 to the insulator film 55, and the tip thereof is the same as the connecting portion 60 a of the lower electrode film 60. In addition, a connection portion 90a is connected to the connection wiring 210.

  A protective film 100 made of an insulating material is provided on the piezoelectric element 300 and the lead electrode 90, and the piezoelectric element 300 and the lead electrode 90 are connected to the lower electrode film 60 and the connection part 60 a of the lead electrode 90. Except for 90 a and the plurality of recesses 101 provided in the protective film 100, it is substantially covered with the protective film 100.

  Here, the concave portion 101 provided in the protective film 100 is formed thinner than the thickness of other regions of the protective film 100. For example, in the present embodiment, the concave portion 101 has the protective film 100 in the thickness direction. The upper electrode film 80 is exposed in the recess 101.

  Such a recess 101 is provided in the width direction of the pressure generating chamber 12 in the protective film 100 in a region facing the piezoelectric active part 320 of each piezoelectric element 300, that is, in a region facing the lower electrode film 60 of the piezoelectric element 300. A plurality are arranged side by side. In other words, the protective film 100 is provided with a plurality of concave portions 101 partitioned by the beam portions 100 a along the width direction of the piezoelectric element 300. For example, in the present embodiment, three recesses 101 are arranged in parallel in the protective film 100 in a region facing each piezoelectric active portion 320 so as to be parallel to the longitudinal direction of the piezoelectric element 300.

  In such a configuration, since the side end face of each piezoelectric element 300 is reliably covered by the protective film 100, the occurrence of dielectric breakdown can be prevented. In addition, since the protective film 100 is provided with the recess 101, it is possible to suppress a decrease in the amount of displacement of the diaphragm due to the driving of the piezoelectric element 300. Furthermore, in the present invention, since the plurality of concave portions 101 are arranged in parallel in the protective film 100, it is possible to prevent the diaphragm from being destroyed due to the deformation of the piezoelectric element 300.

  Specifically, the presence of the girder portion 100 a between the recesses 101 of the protective film 100 makes the rigidity of the diaphragm in the longitudinal direction of the pressure generation chamber 12 greater than the rigidity of the pressure generation chamber 12 in the width direction. . For example, even when compared with a structure in which a single recess having the same opening area as the sum of the opening areas of the plurality of recesses 101 is provided in the protective film, the rigidity of the diaphragm in the longitudinal direction of the pressure generating chamber 12 is It becomes larger than the rigidity of the generation chamber 12 in the width direction. Thereby, it is possible to prevent the vibration plate from being destroyed due to the deformation of the piezoelectric element 300.

  Further, in such a configuration, the rigidity of the diaphragm in the width direction of the pressure generating chamber 12 does not substantially increase, and the amount of displacement of the diaphragm due to the driving of the piezoelectric element 300 is maintained well. In particular, in the structure in which the piezoelectric element 300 extends to the outside in the longitudinal direction of the pressure generating chamber 12 as in the present embodiment, the influence of the rigidity of the diaphragm in the longitudinal direction of the pressure generating chamber 12 on the displacement amount of the diaphragm. Therefore, the amount of displacement of the diaphragm due to the driving of the piezoelectric element 300 is maintained well.

  Here, the total of the widths of the plurality of recesses 101, in this embodiment, the total of the widths W1 to W3 of the piezoelectric elements 300 of the three recesses in the width W4 of the piezoelectric active part 320 in the width direction. It is preferably 25% or more and 60% or less. Thereby, it is possible to prevent the vibration plate from being destroyed due to the deformation of the piezoelectric element 300 while suppressing a decrease in the displacement of the vibration plate. Moreover, it is preferable that the width W5 of the protective film 100 at both ends in the short direction of the piezoelectric element 300 is secured to a predetermined width, for example, about 5 (μm). Thereby, generation | occurrence | production of a dielectric breakdown can be prevented more reliably. Moreover, although the width | variety, space | interval, etc. of each recessed part 101 are not specifically limited, It is preferable to form the recessed part 101 of the same width at the same space | interval like this embodiment. A plurality of recesses having different widths may be arranged side by side, but in that case, it is desirable that the recesses be arranged so as to be symmetrical in the width direction of the piezoelectric element 300. This is because if the recesses are asymmetrical, the deformation state of the diaphragm due to driving of the piezoelectric element 300 is not uniform, and the diaphragm may be broken due to stress concentration.

  In the present embodiment, a plurality of concave portions 101 having the same length are arranged in parallel in the protective film 100. For example, as shown in FIGS. 4 (a) and (b), the protective film 100 has a length. A plurality of recesses 101 having different sizes may be provided side by side. In this case, the end of each recess 101 in the longitudinal direction of the piezoelectric element 300 is positioned closer to the end in the longitudinal direction of the piezoelectric element 300 as the recess 101 closer to the center in the width direction of the piezoelectric element 300. Is preferred. As a result, the stress gradually changes in the vicinity of the end in the longitudinal direction of the piezoelectric body active portion 320, and stress concentration in this portion is prevented. Thereby, destruction of the diaphragm can be prevented more reliably.

The material of the protective film 100 may be an insulating material, but it is preferable to use an inorganic insulating material such as aluminum oxide (Al ₂ O ₃ ) or silicon oxide (SiO ₂ ). This is because the protective film 100 made of such an inorganic insulating material has a very low moisture permeability even in a thin film, and thus is effective in preventing the occurrence of dielectric breakdown due to moisture in the atmosphere.

  A protective substrate 30 having a piezoelectric element holding portion 31 that is a space for protecting the piezoelectric element 300 is bonded to a region facing the piezoelectric element 300 on the flow path forming substrate 10 on which the piezoelectric element 300 is formed. Bonded by the agent 35. The piezoelectric element holding part 31 may be a space that does not hinder the movement of the piezoelectric element 300, and the space may be sealed or unsealed. A reservoir portion 32 is provided in a region of the protective substrate 30 that faces the communication portion 13. As described above, the reservoir section 32 communicates with the communication section 13 of the flow path forming substrate 10 and constitutes a reservoir 110 serving as a common ink chamber for the pressure generating chambers 12.

  The protective substrate 30 is preferably formed of a material substantially the same as the coefficient of thermal expansion of the flow path forming substrate 10, for example, glass, ceramic material, etc. For example, in this embodiment, the same as the flow path forming substrate 10. It was formed using a silicon single crystal substrate of the material.

  A driving IC 200 for driving the piezoelectric element 300 is mounted on the protective substrate 30. The drive IC 200 is electrically connected to the connection portion 60a of the lower electrode film 60 and the connection portion 90a of the lead electrode 90 via a connection wiring 210 made of a conductive wire such as a bonding wire.

  On the protective substrate 30, a compliance substrate 40 composed of a sealing film 41 and a fixing plate 42 is further bonded to seal the reservoir portion 32. Here, the sealing film 41 is made of a material having low rigidity and flexibility, and the fixing plate 42 is made of a hard material such as metal. Since the region of the fixing plate 42 facing the reservoir 110 is an opening 43 that is completely removed in the thickness direction, one surface of the reservoir 110 is sealed only by the flexible sealing film 41. Has been. However, an ink introduction port (not shown) is formed in the compliance substrate 40, and the ink introduction port communicates with the reservoir unit 32 to introduce ink into the reservoir unit 32 from an external ink supply unit (not shown).

  In such an ink jet recording head according to the present embodiment, ink is taken in from an external ink supply unit (not shown), filled with ink from the reservoir 110 to the nozzle opening 21, and then subjected to pressure according to a recording signal from the driving IC 200. By applying a voltage between the lower electrode film 60 and the upper electrode film 80 corresponding to the generation chamber 12 to bend and deform the elastic film 50, the lower electrode film 60, and the piezoelectric layer 70, each pressure generation chamber. The pressure inside the nozzle 12 increases and ink droplets are ejected from the nozzle openings 21.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment. For example, in this embodiment, the protective film 100 is provided so as to cover almost the entire region where the piezoelectric element 300 and the lead electrode 90 are formed. However, the present invention is not limited to this, and the protective film 100 includes at least each of the regions. It suffices if it is provided in a region corresponding to the piezoelectric element 300.

  Further, the ink jet recording head of the above-described embodiment constitutes a part of a recording head unit including an ink flow path communicating with an ink cartridge or the like, and is mounted on the ink jet recording apparatus. FIG. 5 is a schematic perspective view showing an example of the ink jet recording apparatus. As shown in FIG. 5, in the recording head units 1A and 1B having the ink jet recording head, cartridges 2A and 2B constituting ink supply means are detachably provided, and a carriage 3 on which the recording head units 1A and 1B are mounted. Is provided on a carriage shaft 5 attached to the apparatus body 4 so as to be movable in the axial direction. The recording head units 1A and 1B, for example, are configured to eject a black ink composition and a color ink composition, respectively. The driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and timing belt 7 (not shown), so that the carriage 3 on which the recording head units 1A and 1B are mounted is moved along the carriage shaft 5. The On the other hand, the apparatus body 4 is provided with a platen 8 along the carriage shaft 5, and a recording sheet S, which is a recording medium such as paper fed by a paper feed roller (not shown), is conveyed on the platen 8. It is like that.

  In the above-described embodiment, the present invention has been described by taking an ink jet recording head as an example of a liquid ejecting head. However, the present invention is widely applied to all liquid ejecting heads and ejects liquids other than ink. Of course, the invention can also be applied to a liquid jet head. Other liquid ejecting heads include, for example, various recording heads used in image recording apparatuses such as printers, color material ejecting heads used in the manufacture of color filters such as liquid crystal displays, organic EL displays, and FEDs (surface emitting displays). Examples thereof include an electrode material ejection head used for electrode formation, a bioorganic matter ejection head used for biochip production, and the like.

  The present invention can be applied not only to an actuator device mounted on such a liquid jet head (inkjet recording head) but also to an actuator device mounted on any device. The actuator device of the present invention can be applied to, for example, a sensor in addition to the head described above.

FIG. 2 is an exploded perspective view illustrating a schematic configuration of a recording head according to an embodiment. FIG. 2 is a plan view and a cross-sectional view of a main part of a recording head according to an embodiment. FIG. 3 is an enlarged cross-sectional view illustrating a piezoelectric element portion of a recording head according to an embodiment. It is a top view which shows the modification of the recessed part which concerns on one Embodiment. 1 is a schematic perspective view of a recording head according to an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flow path formation board | substrate, 12 Pressure generation chamber, 13 Communication part, 14 Ink supply path, 20 Nozzle plate, 30 Protection board, 40 Compliance board | substrate, 50 Elastic film, 55 Insulator film, 100 Protection film | membrane, 100a Girder part, 101 Recess, 200 Drive IC, 210 Connection wiring, 300 Piezoelectric element

Claims (7)

A piezoelectric element having a lower electrode, a piezoelectric layer and an upper electrode, and a protective film made of an insulating material and provided to cover the piezoelectric element;
In the region of the protective film facing the upper electrode, a plurality of recesses having a thickness of the protective film thinner than other parts are arranged in parallel in the width direction of the piezoelectric element ,
The length of each concave portion in the longitudinal direction of the piezoelectric element is longer toward the concave portion on the central side in the width direction of the piezoelectric element, and both end portions of each concave portion in the longitudinal direction of the piezoelectric element are An actuator device characterized in that the concave portion closer to the center in the width direction is located closer to the end in the longitudinal direction of the piezoelectric element.   2. The actuator device according to claim 1, wherein the total width of the plurality of recesses in the short direction of the piezoelectric element is 25% or more and 60% or less of the width in the short direction of the piezoelectric element. The actuator device according to claim 1 or 2, wherein the recess is a through hole passing through the protective film.   The actuator device according to claim 1, wherein the protective film is made of an inorganic insulating material. Liquid jet head characterized by including the actuator device according to any one of claims 1-4. A liquid ejecting head that ejects liquid in a pressure generating chamber from a nozzle opening by displacement of the actuator device;
6. The liquid jet head according to claim 5 , wherein both ends in the longitudinal direction of the piezoelectric element extend to the outside of a region facing the pressure generation chamber. A liquid ejecting apparatus comprising the liquid ejecting head according to claim 5 .

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