JP2013224044A - Liquid jet head and liquid jet apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid jet head capable of preventing breakage of a piezoelectric element, and a liquid jet apparatus.SOLUTION: Lower electrodes 60 are independently installed corresponding to pressure generation chambers 12, so as to constitute individual electrodes of a piezoelectric element 300. An upper electrode 80 is continuously provided in an arrangement direction of the pressure generation chambers 12, so as to constitute a common electrode of the piezoelectric element 300. Width of the lower electrode 60 in the region facing the pressure generation chamber 12 is formed narrower than width of the pressure generation chamber 12. An upper face and end faces of the lower electrode 60 in the region corresponding to the pressure generation chamber 12 are covered with a piezoelectric body layer 70. An upper face of the piezoelectric body layer 70 in the region facing the pressure generation chamber 12 and side faces of the piezoelectric body layer 70 in the arrangement direction of the piezoelectric elements 300 are covered with the upper electrode 80. On one longitudinal end side of the piezoelectric element 300, the piezoelectric body layer 70 is extended to a bonding region 200 of a flow passage forming substrate 10 to which a peripheral edge of a piezoelectric element retaining part 31 of a joining substrate 30 is bonded, and the lower electrode 60 is extended to the outside of an end of the piezoelectric body layer 70. A terminal 95 is provided at the end of the lower electrode 60.

Description

  The present invention relates to a liquid ejecting head and a liquid ejecting apparatus that eject droplets from nozzles by displacement of a piezoelectric element, and more particularly to an ink jet recording head and an ink jet recording apparatus that eject ink droplets as droplets.

  As an ink jet recording head that is a typical example of a liquid ejecting head that ejects liquid droplets, for example, a flow path forming substrate in which a pressure generating chamber is formed, a lower electrode provided on one side of the flow path forming substrate, a piezoelectric There is a piezoelectric element including a body layer and an upper electrode, and an ink droplet is ejected from a nozzle by applying pressure to the pressure generating chamber by displacement of the piezoelectric element. The piezoelectric element employed in such an ink jet recording head has a problem that it is easily destroyed due to an external environment such as moisture. In order to solve this problem, for example, there is one in which the outer peripheral surface of a piezoelectric layer is covered with an upper electrode (see, for example, Patent Document 1).

JP 2005-88441 A

  As described in Patent Document 1, by covering the piezoelectric layer with the upper electrode, it is possible to suppress the destruction of the piezoelectric layer due to moisture, but it is formed on the end surface of the piezoelectric layer. Since the distance between the upper electrode and the lower electrode becomes extremely short, there is a possibility that dielectric breakdown occurs between the two electrodes and the piezoelectric element is destroyed.

  SUMMARY An advantage of some aspects of the invention is that it provides a liquid ejecting head and a liquid ejecting apparatus that can prevent a piezoelectric element from being destroyed.

The present invention that solves the above-described problems includes a flow path forming substrate in which a plurality of pressure generation chambers communicating with nozzles for discharging droplets are arranged in parallel, a lower electrode provided on one side of the flow path forming substrate, and a piezoelectric A piezoelectric substrate including a body layer and an upper electrode; and a bonding substrate having a piezoelectric element holding portion that is bonded to the one surface side of the flow path forming substrate with an adhesive and serves as a space that does not hinder driving of the piezoelectric element. The lower electrode is independently provided corresponding to the pressure generating chamber to constitute an individual electrode of the piezoelectric element, and the upper electrode is continuously provided in the parallel direction of the pressure generating chamber. The common electrode of the piezoelectric element is configured, and the lower electrode in a region facing the pressure generation chamber is formed with a width narrower than the width of the pressure generation chamber, and the lower region in the region corresponding to the pressure generation chamber The upper surface and the end surface of the electrode are the piezoelectric body The upper surface of the piezoelectric layer in a region facing the pressure generation chamber and the side surface of the piezoelectric layer in the direction in which the piezoelectric elements are arranged side by side are covered with the upper electrode. On one end side in the longitudinal direction, the piezoelectric layer extends to the bonding region of the flow path forming substrate to which the peripheral edge of the piezoelectric element holding portion of the bonding substrate is bonded, and the lower electrode is the piezoelectric In the liquid ejecting head, the terminal is provided at the end of the lower electrode so as to extend to the outside of the end of the body layer.
In the configuration of the present invention, an adhesive for bonding the bonding substrate and the flow path forming substrate exists between the exposed portion of the lower electrode and the exposed portion of the upper electrode. The exposed portion and the exposed portion of the upper electrode are insulated. Accordingly, it is possible to prevent the piezoelectric element from being broken due to the dielectric breakdown that occurs between the lower electrode and the upper electrode.

  Moreover, it is preferable that the end of the lower electrode is covered with the piezoelectric layer on the other end side in the longitudinal direction of the piezoelectric element. Thereby, the dielectric breakdown which arises between a lower electrode and an upper electrode can be prevented more reliably.

  The adhesive is preferably an insulating adhesive. Thereby, the exposed part of the lower electrode and the exposed part of the upper electrode are more reliably insulated by the adhesive.

  In addition, it is preferable that the terminal portion is constituted by a mounting electrode connected to the lower electrode, and the lower electrode and the mounting electrode are connected outside the bonding region or the bonding region. In such a configuration, since the lower electrode is not exposed in the piezoelectric element holding portion, it is possible to more reliably prevent dielectric breakdown that occurs between the lower electrode and the upper electrode.

  According to another aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting head as described above. According to the present invention, a reliable liquid ejecting apparatus with improved head durability can be realized.

FIG. 3 is an exploded perspective view of a recording head according to an embodiment of the invention. 2A and 2B are a plan view and a cross-sectional view of a recording head according to an embodiment of the invention. FIG. 3 is a cross-sectional view illustrating a main part of a recording head according to an embodiment of the invention. FIG. 2 is an enlarged cross-sectional view of a recording head according to an embodiment of the present invention. FIG. 6 is an enlarged cross-sectional view illustrating a modified example of the recording head according to the embodiment of the invention. 1 is a schematic diagram of a recording apparatus according to an embodiment.

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 which is a liquid ejecting head according to an embodiment of the present invention. FIG. 2 is a plan view of FIG. is there. 3 is an enlarged view of the piezoelectric element portion in the BB ′ cross section of FIG.

  As shown in the figure, the flow path forming substrate 10 is a silicon single crystal substrate having a crystal plane orientation of (110) in this embodiment, and an elastic film 50 made of an oxide film is formed on one surface thereof. In the flow path forming substrate 10, a plurality of pressure generating chambers 12 partitioned by the partition wall 11 and having one surface formed of the elastic film 50 are juxtaposed in the width direction.

  The flow path forming substrate 10 is provided with an ink supply path 13 and a communication path 14 which are partitioned by a partition wall 11 and communicate with each pressure generation chamber 12 on one end side in the longitudinal direction of the pressure generation chamber 12. A communication portion 15 that communicates with each communication path 14 is provided outside the communication path 14. The communication portion 15 communicates with a reservoir portion 32 of the bonding substrate 30 described later, and constitutes a part of the reservoir 100 serving as a common ink chamber (liquid chamber) for each pressure generating chamber 12.

  Here, the ink supply path 13 is formed to have a narrower cross-sectional area than the pressure generation chamber 12, and the flow path resistance of the ink flowing into the pressure generation chamber 12 from the communication portion 15 is kept constant. . For example, the ink supply path 13 is formed with a width smaller than the width of the pressure generation chamber 12 by narrowing the flow path on the pressure generation chamber 12 side between the reservoir 100 and each pressure generation chamber 12 in the width direction. . In this embodiment, the ink supply path is formed by narrowing the width of the flow path from one side. However, the ink supply path may be formed by narrowing the width of the flow path from both sides. Further, the ink supply path may be formed by narrowing from the thickness direction instead of narrowing the width of the flow path. Each communication passage 14 is formed by extending the partition walls 11 on both sides in the width direction of the pressure generating chamber 12 toward the communication portion 15 to partition the space between the ink supply path 13 and the communication portion 15. Yes.

  In this embodiment, a silicon single crystal substrate is used as a material for the flow path forming substrate 10, but of course, the material is not limited to this, and for example, glass ceramics, stainless steel, or the like may be used.

  On the opening surface side of the flow path forming substrate 10, a nozzle plate 20 having a nozzle 21 communicating with the vicinity of the end portion of each pressure generating chamber 12 on the side opposite to the ink supply path 13 is provided with an adhesive or heat welding. It is fixed by a film or the like. The nozzle plate 20 is made of, for example, glass ceramics, a silicon single crystal substrate, stainless steel, or the like.

  On the other hand, the elastic film 50 is formed on the side opposite to the opening surface of the flow path forming substrate 10 as described above, and an oxide film made of a material different from the elastic film 50 is formed on the elastic film 50. An insulating film 55 is formed. On the insulator film 55, a piezoelectric element 300 including a lower electrode film 60, a piezoelectric layer 70, and an upper electrode film 80 is formed. The piezoelectric element 300 includes at least a portion having the piezoelectric layer 70 as well as a portion having the lower electrode film 60, the piezoelectric layer 70 and the upper electrode film 80. In general, one of the electrodes of the piezoelectric element 300 is used as a common electrode, and the other electrode is patterned together with the piezoelectric layer 70 for each pressure generating chamber 12 to form individual electrodes. Also, here, the piezoelectric element 300 and a diaphragm that is displaced by driving the piezoelectric element 300 are collectively referred to as an actuator. In the above-described example, the elastic film 50, the insulator film 55, and the lower electrode film 60 function as a diaphragm. However, the elastic film 50 and the insulator film 55 are not provided, and only the lower electrode film 60 is left. The electrode film 60 may be a diaphragm. Further, the piezoelectric element 300 itself may substantially serve as a diaphragm.

  On the flow path forming substrate 10, a bonding substrate 30 having a piezoelectric element holding portion 31 that becomes a space that does not hinder the driving of the piezoelectric element 300 is bonded by an adhesive 35. The piezoelectric element holding unit 31 is configured to be able to suppress the intrusion of air into the piezoelectric element holding unit 31. That is, the piezoelectric element holding part 31 does not necessarily need to be sealed as long as the intrusion of the atmosphere can be suppressed. And since the piezoelectric element 300 is formed in such a piezoelectric element holding | maintenance part 31, it is protected in the state which hardly receives the influence of an external environment.

  Here, the structure of the piezoelectric element 300 according to the present embodiment will be described in detail. As shown in FIG. 2, the lower electrode film 60 constituting the piezoelectric element 300 is provided with a width narrower than the width of the pressure generation chamber 12 for each region facing each pressure generation chamber 12. Individual electrodes are configured. Further, the lower electrode film 60 extends to the outside of the end of the pressure generating chamber 12 on one end in the longitudinal direction of the piezoelectric element 300, and the end of the lower electrode film 60 on the other end in the longitudinal direction of the piezoelectric element 300. Is located in the pressure generating chamber 12.

  The piezoelectric layer 70 is provided with a width wider than the width of the lower electrode film 60 and narrower than the width of the pressure generating chamber 12. The piezoelectric layer 70 extends to the outside of the end of the pressure generation chamber 12 in the longitudinal direction of the piezoelectric element 300, and completely covers the upper surface and the end surface of the lower electrode film 60 in a region facing the pressure generation chamber 12. It is provided to cover. Therefore, in the configuration of the present embodiment, the end portion of the lower electrode film 60 located in the pressure generating chamber 12 on the other end side in the longitudinal direction of the piezoelectric element 300 is completely covered with the piezoelectric layer 70.

  Note that the end of the lower electrode film 60 on the other end in the longitudinal direction of the piezoelectric element 300 may be located outside the pressure generating chamber 12. Even in such a configuration, the piezoelectric layer 70 may be provided so as to cover the upper surface and the end surface of the lower electrode film 60 in a region facing the pressure generation chamber 12, but covers the end portion of the lower electrode film 60. Are preferably provided.

  On one end side in the longitudinal direction of the piezoelectric element 300, the piezoelectric layer 70 extends to the bonding region 200 of the flow path forming substrate 10 to which the peripheral edge of the piezoelectric element holding portion 31 of the bonding substrate 30 is bonded. It is preferable to extend to the outside of the bonding region 200.

  The “adhesion region 200” here refers to a region where the adhesive 35 for bonding the bonding substrate 30 to the flow path forming substrate 10 spreads. That is, the piezoelectric layer 70 does not have to be sandwiched between the flow path forming substrate 10 and the bonding substrate 30, and it is sufficient that at least the end surface thereof is in contact with the adhesive 35. For example, as shown in FIG. 4, in this embodiment, the end portion of the piezoelectric layer 70 extends to the outside of the bonding region 200, but as shown in FIG. If the part is in contact with the adhesive 35, it may be formed in the piezoelectric element holding part 31.

  In addition, a lower electrode film 60 is further extended outside the piezoelectric layer 70 extending to the adhesion region 200 in this way, and gold (Au) or the like is provided at the end of the lower electrode film 60, for example. A terminal portion 95 to which a connection electrode (not shown) made of a bonding wire or the like is connected is formed. That is, the lower electrode film 60 and the mounting electrode 90 are connected not in the piezoelectric element holding portion 31 but in the adhesion region 200 or outside the adhesion region 200. A voltage is selectively applied to each piezoelectric element 300 via the terminal portion 95 (mounting electrode 90).

  The upper electrode film 80 is continuously formed in a region facing the plurality of pressure generating chambers 12, and the end of the upper electrode film 80 is a region facing the pressure generating chamber 12 on one end side in the longitudinal direction of the piezoelectric element. The end of the upper electrode film 80 is located outside the pressure generation chamber 12 at the other longitudinal end of the piezoelectric element 300. In the upper electrode film 80, the upper surface of the piezoelectric layer 70 in the region facing the pressure generation chamber 12 and the side surface (end surface) of the piezoelectric layer in the direction in which the piezoelectric elements 300 are arranged are covered with the upper electrode. That is, the width of the piezoelectric layer 70 is formed wider toward the lower electrode film 60 side, and the side surface of the piezoelectric layer 70 is inclined, and the upper electrode film 80 is piezoelectric in the region facing the pressure generating chamber 12. It is provided to cover the side surface of the body layer 70 (see FIG. 3). In the present embodiment, the side surface of the piezoelectric layer 70 on the other end side in the longitudinal direction of the piezoelectric element 300 is also covered with the upper electrode film 80.

  Further, such an upper electrode film 80 is provided substantially only in the piezoelectric element holding portion 31. Actually, the upper electrode film 80 is formed only in the piezoelectric element holding part 31, but the mounting electrode 91 connected to the upper electrode film 80 extends to the outside of the piezoelectric element holding part 31, and As in the case of the electrode film 60, the tip end portion of the mounting electrode 91 is a terminal portion 95 connected to a connection wiring (not shown). That is, the upper electrode film 80 is formed in the piezoelectric element holding portion 31 except for the terminal portion 95.

  In such a configuration, the lower electrode film 60 is exposed only outside the piezoelectric element holding portion 31, while the upper electrode film 80 is exposed only inside the piezoelectric element holding portion 31. An adhesive 35 for bonding the bonding substrate 30 and the flow path forming substrate 10 exists between the exposed portion of the upper electrode film 80. Therefore, the lower electrode film 60 and the upper electrode film 80 are insulated from each other by the adhesive 35, and the piezoelectric element 300 is prevented from being destroyed due to the dielectric breakdown generated between the lower electrode film 60 and the upper electrode film 80. Can do.

  Since the adhesive 35 that bonds the bonding substrate 30 and the flow path forming substrate 10 serves to insulate the upper electrode film 80 and the lower electrode film 60 in this way, it is preferable to use an insulating adhesive. . Thereby, the lower electrode film 60 and the upper electrode film 80 can be more reliably insulated.

  In addition, since the upper electrode film 80 is provided so as to cover the surface of the piezoelectric layer 70, it is possible to prevent moisture (humidity) from penetrating into the piezoelectric layer 70 without separately providing a protective film. . Since a protective film is not required, the manufacturing cost is greatly reduced, the destruction of the piezoelectric element 300 (piezoelectric layer 70) due to moisture (humidity) can be prevented, and the durability of the piezoelectric element 300 is improved. Can do.

  Furthermore, in the present embodiment, as described above, the end portion of the upper electrode film 80 on the one end side in the longitudinal direction of the piezoelectric element 300 is located in a region facing the pressure generation chamber 12, A driving unit is provided in a region facing the pressure generating chamber 12. That is, in the piezoelectric element 300, a portion between the end portion of the lower electrode film 60 and the end portion of the upper electrode film 80 located in the pressure generating chamber 12 is a substantial driving unit. For this reason, even if the piezoelectric element 300 is driven, the vibration plate (the elastic film 50 and the insulator film 55) in the vicinity of both ends in the longitudinal direction of the pressure generating chamber 12 is not greatly deformed. It is possible to prevent cracks from occurring.

  The bonding substrate 30 is provided with a reservoir portion 32 in a region corresponding to the communication portion 15 of the flow path forming substrate 10. In this embodiment, the reservoir portion 32 is provided along the parallel direction of the pressure generating chambers 12 through the bonding substrate 30 in the thickness direction. As described above, the communication portion of the flow path forming substrate 10 is provided. The reservoir 100 is connected to the pressure generation chamber 12 and serves as a common ink chamber for the pressure generation chambers 12.

  Further, a through hole 33 that penetrates the bonding substrate 30 in the thickness direction is provided in a region of the bonding substrate 30 on the opposite side of the piezoelectric element holding portion 31 from the reservoir portion 32, and the lower electrode film 60 and the upper electrode described above are provided. A terminal portion 95 of the film 80 is formed in the through hole 33. Although not shown, the terminal portions 95 of the lower electrode film 60 and the upper electrode film 80 are connected to a driving IC or the like for driving the piezoelectric element 300 by connection wiring extending in the through hole 33.

  In addition, examples of the material of the bonding substrate 30 include glass, ceramic material, metal, resin, and the like, but it is more preferable that the bonding substrate 30 is formed of substantially the same material as the thermal expansion coefficient of the flow path forming substrate 10. In this embodiment, the silicon single crystal substrate made of the same material as the flow path forming substrate 10 is used.

  A compliance substrate 40 including a sealing film 41 and a fixing plate 42 is further bonded onto the bonding substrate 30. The sealing film 41 is made of a material having low rigidity and flexibility, and one surface of the reservoir portion 32 is sealed by the sealing film 41. The fixed plate 42 is formed of a hard material such as metal. Since the region of the fixing plate 42 facing the reservoir 100 is an opening 43 that is completely removed in the thickness direction, one surface of the reservoir 100 is sealed only with a flexible sealing film 41. Has been.

  In such an ink jet recording head of the present embodiment, ink is taken in from an external ink supply means (not shown), filled with ink from the reservoir 100 to the nozzle 21, and then in accordance with a recording signal from a driving IC (not shown). By applying a voltage to each piezoelectric element 300 corresponding to the pressure generation chamber 12 to bend and deform the piezoelectric element 300, the pressure in each pressure generation chamber 12 increases and ink droplets are ejected from the nozzles 21.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to embodiment mentioned above of course.

  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. 6 is a schematic view showing an example of the ink jet recording apparatus. As shown in FIG. 6, 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. Then, the driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and a 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 main 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 not-shown paper feed roller, is conveyed on the platen 8. It is like that.

  In the above-described embodiment, the ink jet recording apparatus in which the ink jet recording head is mounted on the carriage and moves in the main scanning direction is exemplified. However, the present invention is also applicable to other types of ink jet recording apparatuses. be able to. For example, the present invention is also applied to a so-called line type ink jet recording apparatus that has a plurality of fixed ink jet recording heads and performs printing only by moving a recording sheet S such as paper in the sub-scanning direction. Can do.

  In the above-described embodiments, the ink jet recording head and the ink jet recording apparatus have been described as examples of the liquid ejecting head and the liquid ejecting apparatus of the present invention. However, the basic configurations of the liquid ejecting head and the liquid ejecting apparatus are as described above. It is not limited. The present invention covers a wide range of liquid ejecting heads and liquid ejecting apparatuses that include a liquid ejecting head, and can be applied to a device that ejects liquid other than ink. 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 (field emission 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.

  10 flow path forming substrate, 12 pressure generating chamber, 20 nozzle plate, 21 nozzle, 30 bonding substrate, 40 compliance substrate, 50 elastic film, 55 insulator film, 60 lower electrode film, 70 piezoelectric layer, 80 upper electrode film, 90, 91 Mounting electrode, 95 Terminal section, 100 Reservoir, 200 Adhesion area, 300 Piezoelectric element

Claims (5)

A flow path forming substrate in which a plurality of pressure generating chambers communicating with nozzles for discharging droplets are arranged in parallel, and a piezoelectric element comprising a lower electrode, a piezoelectric layer, and an upper electrode provided on one side of the flow path forming substrate And a bonding substrate having a piezoelectric element holding portion that is bonded to the one surface side of the flow path forming substrate with an adhesive and becomes a space that does not hinder driving of the piezoelectric element,
The lower electrode is provided independently corresponding to the pressure generation chamber to constitute an individual electrode of the piezoelectric element, and the upper electrode is continuously provided across the direction in which the pressure generation chambers are arranged. Configure the common electrode of the piezoelectric element,
The lower electrode in the region facing the pressure generating chamber is formed with a width narrower than the width of the pressure generating chamber, and the upper surface and the end surface of the lower electrode in the region corresponding to the pressure generating chamber are the piezoelectric layer. Covered by
The upper surface of the piezoelectric layer in the region facing the pressure generation chamber and the side surface of the piezoelectric layer in the direction in which the piezoelectric elements are arranged side by side are covered with the upper electrode,
On one end side in the longitudinal direction of the piezoelectric element, the piezoelectric layer extends to the bonding region of the flow path forming substrate to which the peripheral edge of the piezoelectric element holding portion of the bonding substrate is bonded. A liquid ejecting head, wherein an electrode extends to an outside of an end portion of the piezoelectric layer, and a terminal portion is provided at an end portion of the lower electrode.   The liquid ejecting head according to claim 1, wherein an end portion of the lower electrode is covered with the piezoelectric layer on the other end portion side in the longitudinal direction of the piezoelectric element.   The liquid ejecting head according to claim 1, wherein the adhesive is an insulating adhesive.   The terminal portion is composed of a mounting electrode connected to the lower electrode, and the lower electrode and the mounting electrode are connected to each other on the adhesive region or outside the adhesive region. The liquid jet head according to claim 1.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1.

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