JP2010167719A - Liquid injection head, liquid injection device and piezoelectric element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid injection head, the piezoelectric element of which can be favorably displaced even when outermost piezoelectrical body layers are inactive layers, and to provide a liquid injection device and piezoelectric elements. <P>SOLUTION: The piezoelectric elements are so constituted of a plurality of piezoelectrical body layers 21, first internal electrodes 22 and second internal electrodes 23 alternately arranged between the piezoelectrical body layers 21 as the outermost piezoelectrical body layers 21a and 21b are respectively arranged to be non-piezoelectrically deformable in active layers and, at the same time, the thickness of at least either one layer between the outermost piezoelectrical body layers 21a and 21b is made thinner than the thickness of the piezoelectrical body layers 21c except the outermost layers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid ejecting head and a liquid ejecting apparatus that eject liquid droplets from nozzles, and a piezoelectric element used in these.

  As a typical example of a liquid ejecting head, for example, a part of a pressure generation chamber communicating with a nozzle opening for ejecting ink droplets is configured by a vibration plate (spring plate material), and the vibration plate is deformed by a piezoelectric element (actuator). There is an ink jet recording head that pressurizes ink in a pressure generating chamber and ejects ink droplets from nozzle openings. As a piezoelectric element used for such an ink jet recording head, for example, there is one formed by alternately laminating a common internal electrode and individual internal electrodes and a piezoelectric layer (see, for example, Patent Document 1). .

  Various types of piezoelectric element structures in which piezoelectric layers and electrodes are alternately stacked are proposed (see, for example, Patent Documents 2 and 3).

JP 2004-327462 A Japanese Patent No. 3456380 Japanese Patent No. 3214017

  Regarding the piezoelectric element in which such a plurality of piezoelectric layers are laminated, generally, the thickness of the piezoelectric layer of the outermost layer is other than the outermost layer, as is the case with the configuration described in each patent document. It is thicker than the thickness of the piezoelectric layer. When the outermost piezoelectric layer is an active layer, that is, when piezoelectric deformation occurs when a voltage is applied, the outermost piezoelectric layer may be relatively thick. The displacement of the piezoelectric element is not hindered. However, when the outermost piezoelectric layer is an inactive layer, displacement of the piezoelectric element may be hindered by the outermost piezoelectric layer.

  The present invention has been made in view of such circumstances, and a liquid ejecting head, a liquid ejecting apparatus, and a piezoelectric device that can favorably displace a piezoelectric element even if the outermost piezoelectric layer is an inactive layer. An object is to provide an element.

The present invention for solving the above-described problems comprises a pressure generation chamber communicating with a nozzle and a piezoelectric element provided on a diaphragm constituting one surface of the pressure generation chamber, and the piezoelectric element includes a plurality of layers of piezoelectric elements. A first internal electrode and a second internal electrode that are alternately arranged between the body layers and the piezoelectric layers, so that each of the outermost piezoelectric layers is an inactive layer that does not undergo piezoelectric deformation. And a thickness of at least one of the outermost piezoelectric layers is equal to or less than a thickness of the piezoelectric layers other than the outermost layer.
In the present invention, a decrease in displacement of the piezoelectric element can be suppressed in a configuration in which the outermost layer is an inactive layer. Therefore, it is possible to eject droplets from the nozzles satisfactorily.

  Here, the total thickness of the outermost piezoelectric layers is preferably not more than twice the thickness of the piezoelectric layers other than the outermost layer. In addition, it is preferable that the thickness of each of the outermost piezoelectric layers constituting the piezoelectric element is equal to or less than the thickness of the other piezoelectric layers. Thereby, the fall of the displacement of a piezoelectric element is fully suppressed.

  Furthermore, it is preferable that the thickness of the outermost piezoelectric layer constituting the piezoelectric element is 5 μm or more. Thereby, the fall of the displacement of a piezoelectric element is suppressed, and an internal electrode is exposed and generation | occurrence | production of malfunctions, such as a disconnection and a short circuit, is suppressed.

  The piezoelectric element may be deformed by a reverse piezoelectric effect in the d31 direction of the piezoelectric layer, or may be deformed by a reverse piezoelectric effect in the d33 direction of the piezoelectric layer. In any of these types of piezoelectric elements, a decrease in displacement is suppressed by adopting the above configuration.

  According to another aspect of the invention, there is provided a liquid ejecting apparatus including the liquid ejecting head configured as described above. According to the present invention, it is possible to realize a liquid ejecting apparatus that can eject liquid droplets from the head and improve reliability.

  The present invention further includes a plurality of piezoelectric layers and first and second internal electrodes alternately arranged between the piezoelectric layers, each of the outermost piezoelectric layers being The piezoelectric element is configured to be an inactive layer that does not undergo piezoelectric deformation, and the thickness of at least one of the outermost piezoelectric layers is equal to or less than the thickness of the piezoelectric layers other than the outermost layer. . In this invention, even if the outermost layer is an inactive layer, it is possible to suppress a decrease in displacement of the piezoelectric element.

FIG. 3 is a cross-sectional view illustrating a recording head according to an embodiment. It is the top view and sectional drawing which show the piezoelectric element which concerns on one Embodiment. 1 is a schematic perspective view showing a recording apparatus according to an embodiment.

Hereinafter, the present invention will be described in detail based on embodiments.
As shown in FIG. 1, an ink jet recording head that is an example of a liquid ejecting head according to this embodiment includes a flow path forming substrate 12 provided with a plurality of pressure generating chambers 11, and a plurality of communicating with the pressure generating chambers 11. A nozzle plate 14 in which the nozzles 13 are perforated, a diaphragm 15 provided on the surface of the flow path forming substrate 12 opposite to the nozzle plate 14, and areas corresponding to the pressure generation chambers 11 on the diaphragm 15. And a piezoelectric element 16 as pressure generating means.

  In the flow path forming substrate 12, a plurality of pressure generating chambers 11 are partitioned by a partition wall 17 and arranged in parallel in the width direction. For example, in this embodiment, two rows in which the plurality of pressure generating chambers 11 are arranged in parallel are provided on the flow path forming substrate 12.

  A reservoir 18 for supplying ink to each pressure generating chamber 11 is provided outside the row of each pressure generating chamber 11 so as to penetrate the flow path forming substrate 12 in the thickness direction. Each pressure generating chamber 11 and the reservoir 18 communicate with each other via an ink supply path 19. In this embodiment, the ink supply path 19 is formed with a width narrower than that of the pressure generation chamber 11, and plays a role of maintaining a constant flow path resistance of ink flowing from the reservoir 18 into the pressure generation chamber 11.

  Further, in this embodiment, the pressure generation chamber 11 is formed without penetrating the flow path forming substrate 12, and the flow path forming substrate 12 is provided on the end side opposite to the reservoir 18 of the pressure generation chamber 11. A nozzle communication path 20 that penetrates and communicates with the nozzle 13 is formed.

  A nozzle plate 14 is bonded to one surface side of the flow path forming substrate 12. As described above, each nozzle 13 communicates with each pressure generating chamber 11 via the nozzle communication path 20 provided in the flow path forming substrate 12. A vibration plate 15 is bonded to the other surface side of the flow path forming substrate 12, that is, the opening surface side of the pressure generation chamber 11, and each pressure generation chamber 11 is sealed by the vibration plate 15. On the vibration plate 15, a piezoelectric element 16 is provided as pressure generating means for generating pressure for ejecting ink droplets into the pressure generating chamber 11. The piezoelectric element 16 is fixed with the tip of the active region in contact with the diaphragm 15.

  In the piezoelectric element 16, piezoelectric layers 21, individual internal electrodes 22, and common internal electrodes 23 are alternately stacked, and an inactive region that does not contribute to piezoelectric deformation is fixed to a fixed substrate 24. A drive wiring 26 on which a drive IC 25 is mounted is connected to the inactive region of the piezoelectric element 16. The structure of the piezoelectric element 16 will be described later in detail.

  On the vibration plate 15, a head case 28 having an accommodating portion 27 for accommodating the piezoelectric element 16 in a state of being fixed to the fixed substrate 24 is fixed. The vibration plate 15 with which the tip of the piezoelectric element 16 abuts is, for example, a composite plate of an elastic film 29 made of an elastic member such as a resin film and a support plate 30 made of, for example, a metal material that supports the elastic film 29. The elastic film 29 side is joined to the flow path forming substrate 12. In addition, an island portion 31 with which the tip of the active region of the piezoelectric element 16 abuts is provided in a region of the diaphragm 15 facing each pressure generating chamber 11. That is, a thin portion 32 having a thickness smaller than that of other regions is formed in a region of the vibration plate 15 facing the peripheral portion of each pressure generating chamber 11, and an island portion 31 is provided inside each of the thin portions 32. Yes.

  In the region of the vibration plate 15 that faces the reservoir 18, similarly to the thin portion 32, a compliance portion 33 that is substantially composed only of the elastic film 29 is provided by removing the support plate 30. A space portion 34 that is a space that allows deformation of the compliance portion 33 is formed in a portion of the head case 28 that faces the compliance portion 33.

  In such an ink jet recording head, when ejecting ink droplets, the volume of each pressure generating chamber 11 is changed by deformation of the piezoelectric element 16 and the diaphragm 15 so that ink droplets are ejected from a predetermined nozzle 13. It has become. Specifically, when ink is supplied to the reservoir 18 from an ink cartridge (not shown), the ink is distributed to each pressure generating chamber 11 via the ink supply path 19. Actually, the piezoelectric element 16 is contracted by applying a voltage to the piezoelectric element 16. As a result, the diaphragm 15 is deformed together with the piezoelectric element 16 to expand the volume of the pressure generating chamber 11, and ink is drawn into the pressure generating chamber 11. Then, after the ink is filled up to the nozzle 13, the voltage applied to the individual internal electrode 22 and the common internal electrode 23 of the piezoelectric element 16 is released according to the recording signal from the drive IC 25. As a result, the piezoelectric element 16 is expanded to return to the original state, and the diaphragm 15 is also displaced to return to the original state. As a result, the volume of the pressure generation chamber 11 contracts, the pressure in the pressure generation chamber 11 increases, and ink droplets are ejected from the nozzle 13.

  Hereinafter, the structure of the piezoelectric element 16 will be described in detail. The piezoelectric element 16 according to the present embodiment is deformed by the inverse piezoelectric effect of the piezoelectric layer 21 in the d31 direction. As shown in FIG. 2, a plurality of piezoelectric layers 21 and a space between each piezoelectric layer 21 are provided. A plurality of piezoelectric element forming members 35 are formed integrally with individual internal electrodes 22 that are first internal electrodes and common internal electrodes 23 that are second internal electrodes that are alternately arranged. That is, the piezoelectric element forming member 35 is formed with a plurality of slits 36 by, for example, a wire saw or the like, so that the distal end side is cut into a comb-like shape to form a plurality of piezoelectric elements 16. A positioning portion 38 having a width wider than that of the piezoelectric elements 16 is provided on both outer sides of the rows 37 of the piezoelectric elements 16. The positioning portion 38 is provided for positioning each piezoelectric element 16 with respect to the housing portion 27 of the head case 28 with high accuracy.

  The individual internal electrode 22 of each piezoelectric element 16 is provided so as to be exposed at one end face (end face of the active region of the piezoelectric element 16) 35 a of the piezoelectric element forming member 35. In the present embodiment, the individual internal electrode 22 extends from the end surface 35 a of the piezoelectric element forming member 35 to the central portion of the piezoelectric element forming member 35 toward the inactive region. On the other hand, the common internal electrode 23 is provided so as to be exposed at the other end surface (end surface on the base end portion side of the piezoelectric element 16) 35 b of the piezoelectric element forming member 35. The common internal electrode 23 is provided over substantially the entire surface of the piezoelectric element forming member 35, but is formed so as not to be exposed at the end surface 35 a of the piezoelectric element forming member 35. The portion where the individual internal electrode 22 and the common internal electrode 23 overlap is an active region where piezoelectric deformation actually occurs when a voltage is applied, and the other portion does not cause piezoelectric deformation or is active This is an inactive region that undergoes piezoelectric deformation to the extent that it does not contribute to ejection as the region is displaced.

  In the present embodiment, an auxiliary internal electrode 39 that is a third internal electrode independent of the individual internal electrode 22 is provided on the same plane as the individual internal electrode 22. As will be described later, the auxiliary internal electrode 39 is connected to the common internal electrode 23 via the common external electrode 41 and plays a role of reducing the resistance value of the common internal electrode 23. If the resistance value of the common internal electrode 23 is high, there is a possibility that the displacement amount of each piezoelectric element 16 varies due to a voltage drop. In the case where the piezoelectric elements 16 are formed with a high density, variations are particularly likely to occur. However, since the auxiliary internal electrode 39 is connected to the common internal electrode 23, the resistance value of the common internal electrode 23 is substantially reduced, and thus the variation in the displacement amount of the piezoelectric element 16 is suppressed.

  Furthermore, by providing this auxiliary internal electrode 39, deformation (warping) when the piezoelectric element 16 is manufactured can be suppressed. That is, if the number of electrode layers is different between the active region and the inactive region, the piezoelectric element 16 (piezoelectric element forming member 35) may be deformed (warped) by heat. By providing 39, such deformation can be suppressed. In order to obtain such an effect, each region in which the common internal electrode 23 is formed in the direction in which the surface of the piezoelectric element 16 where the individual external electrode 40 and the common external electrode 41 are formed is viewed in plan view. It is desirable that the regions where the auxiliary internal electrodes 39 are formed have the same size and the same size. Although described as “same” here, variations in the manufacturing process of the electrodes are included in the same range.

  On the surface of the piezoelectric element forming member 35, an individual external electrode 40 connected to the individual internal electrode 22 and a common external electrode 41 connected to the common internal electrode 23 and the auxiliary internal electrode 39 are electrically independent. Is formed. In the present embodiment, the individual external electrode 40 is an auxiliary internal portion of the surface on which the individual external electrode 40 and the common external electrode 41 of the piezoelectric element 16 are formed from the end surface 35 a (the tip of the active region) of the piezoelectric element forming member 35. A part of the region (inactive region) facing the electrode 39 is continuously provided. The individual external electrode 40 is connected to each individual internal electrode 22 at the end face 35 a of the piezoelectric element forming member 35. On the other hand, the common external electrode 41 is an auxiliary internal electrode in which the individual external electrode 40 and the common external electrode 41 of the piezoelectric element 16 are formed from the end surface 35b which is the surface opposite to the end surface 35a of the piezoelectric element forming member 35. 39 is continuously provided up to a part of the region facing 39. The common external electrode 41 is connected to the common internal electrode 23 and the auxiliary internal electrode 39 at the end face 35 b of the piezoelectric element forming member 35.

  Here, among the plurality of piezoelectric layers 21 constituting the piezoelectric element 16, the outermost piezoelectric layers 21 a and 21 b, that is, the piezoelectric layers 21 a and 21 b at both ends in the stacking direction are applied to the piezoelectric element 16. It is an inactive layer that does not deform piezoelectrically or deforms slightly with the piezoelectric deformation of the active layer. The individual internal electrode 22, the auxiliary internal electrode 39, and the common internal electrode 23 are the order of the individual internal electrode 22, the auxiliary internal electrode 39, and the common internal electrode 23 from the surface side of the piezoelectric element forming member 35 on which the individual external electrode 40 is formed. Are arranged alternately. Therefore, the outermost piezoelectric layer 21a on the surface side on which the individual external electrode 40 and the common external electrode 41 of the piezoelectric element 16 are formed is the same as the individual internal electrode 22 and the individual external electrode even in the active region. The inactive layer is sandwiched between the electrodes 40 and does not cause piezoelectric deformation. On the other hand, an outer electrode is not formed on the surface of the outermost piezoelectric layer 21b on the fixed substrate 24 side, so that an inactive layer is formed.

  The thickness of at least one of the outermost piezoelectric layers 21a and 21b, which are such inactive layers, is that of the piezoelectric layer other than the outermost layer (hereinafter referred to as “inner piezoelectric layer”) 21c. It is below the thickness. Preferably, the total thickness of the outermost piezoelectric layers 21a and 21b is not more than twice that of the inner piezoelectric layer 21c. In particular, each of the outermost piezoelectric layers 21a and 21b has an inner piezoelectric layer. The thickness is preferably equal to or less than the thickness of the body layer 21c. In the present embodiment, as shown in the drawing, the thicknesses t1 and t2 of the outermost piezoelectric layers 21a and 21b are made thinner than the thickness t3 of the inner piezoelectric layer 21c.

  In the present embodiment, the inner piezoelectric layers 21c are formed with substantially the same thickness, but the inner piezoelectric layers 21c do not necessarily have the same thickness. When the thicknesses of the inner piezoelectric layers 21c are different, the outermost piezoelectric layers 21a and 21b may be less than or equal to the maximum thickness of the inner piezoelectric layer 21c, but less than the minimum thickness. It is preferable.

  As described above, when the outermost piezoelectric layers 21a and 21b constituting the multilayer piezoelectric element 16 are inactive layers, the thickness of the outermost piezoelectric layers 21a and 21b is set to the inner piezoelectric layer. By setting the thickness to be equal to or less than the thickness of the body layer 21c, it is possible to suppress a decrease in displacement of the piezoelectric element 16 due to the outermost piezoelectric layers 21a and 21b. Therefore, each piezoelectric element 16 can be sufficiently displaced to eject ink droplets satisfactorily.

  The thickness of the outermost piezoelectric layers 21a and 21b is preferably as thin as possible from the viewpoint of lowering the displacement of the piezoelectric element 16, but if too thin, internal electrodes (individual internal electrodes 22 and common internal electrodes) 23) may be exposed, leading to problems such as disconnection or short circuit. For this reason, the outermost piezoelectric layers 21a and 21b are preferably formed with such a thickness that does not cause such a problem, and specifically with a thickness of 5 μm or more.

  As mentioned above, although one embodiment of the present invention was described, of course, the present invention is not limited to this embodiment. For example, in the above-described embodiment, the configuration in which a plurality of piezoelectric elements are integrally formed on the piezoelectric element forming member is illustrated, but it is needless to say that the piezoelectric elements may be independent of each other. In the above-described embodiment, the configuration in which the auxiliary internal electrode is provided between the piezoelectric layers is illustrated, but the auxiliary internal electrode may not be provided.

  Further, for example, in the above-described embodiment, external electrodes (individual external electrodes and common external electrodes) are provided on the surface of the piezoelectric element, and internal electrodes (individual internal electrodes and common internal electrodes) are formed on the end surfaces of the piezoelectric elements (piezoelectric element forming members). However, the structure of the external electrode is not particularly limited. For example, a through hole penetrating the piezoelectric element in the thickness direction may be provided, and an external electrode may be formed in the through hole and connected to the internal electrode.

  Further, for example, in the above-described embodiment, the piezoelectric element is exemplified by a piezoelectric layer that deforms due to the reverse piezoelectric effect in the d31 direction of the piezoelectric layer. However, the piezoelectric element is alternately arranged between a plurality of piezoelectric layers and these piezoelectric layers. The present invention can be applied to any multilayer piezoelectric element having a first internal electrode and a second internal electrode. For example, the piezoelectric layer may be deformed by a reverse piezoelectric effect in the d33 direction, and even a piezoelectric element of this type can suppress a decrease in displacement.

  The ink jet recording head of this 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. Specifically, as shown in FIG. 3, the recording head units 1A and 1B in the ink jet recording apparatus are detachably provided with cartridges 2A and 2B constituting the ink supply means, and the recording head units 1A and 1B are provided. The mounted carriage 3 is provided on a carriage shaft 5 attached to the apparatus main body 4 so as to be movable in the axial direction. The recording head units 1A and 1B eject, for example, 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 that is a recording medium such as paper fed by a paper feed roller (not shown) is wound around the platen 8. It is designed to be transported.

  In the above-described embodiment, an ink jet recording head that ejects ink droplets is exemplified as the liquid ejecting head. However, the present invention is widely intended for all liquid ejecting heads. Examples of the liquid ejecting head include a recording head used in an image recording apparatus such as a printer, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an organic EL display, and an electrode formation such as an FED (field emission display). Electrode material ejecting heads used in manufacturing, bioorganic matter ejecting heads used in biochip production, and the like.

  The present invention is not limited to a piezoelectric element mounted on a liquid jet head typified by an ink jet recording head, and can also be applied to a piezoelectric element mounted on another apparatus.

12 flow path forming substrate, 14 nozzle plate, 15 vibrating plate, 16 piezoelectric element, 21 piezoelectric layer, 22 individual internal electrode, 23 common internal electrode, 24 fixed substrate, 28 head case, 29 elastic film, 30 support plate, 35 Piezoelectric element forming member, 39 auxiliary internal electrode, 40 individual external electrode, 41 common external electrode

Claims (8)

A pressure generation chamber communicating with the nozzle, and a piezoelectric element provided on a vibration plate constituting one surface of the pressure generation chamber,
The piezoelectric element has a plurality of piezoelectric layers and first and second internal electrodes alternately arranged between the piezoelectric layers, and each of the outermost piezoelectric layers is A liquid jet configured to be an inert layer that does not undergo piezoelectric deformation, and wherein the thickness of at least one of the outermost piezoelectric layers is equal to or less than the thickness of a piezoelectric layer other than the outermost layer. head.   2. The liquid jet head according to claim 1, wherein the total thickness of the outermost piezoelectric layers is not more than twice the thickness of the piezoelectric layers other than the outermost layer.   3. The liquid jet head according to claim 1, wherein the thickness of each of the outermost piezoelectric layers constituting the piezoelectric element is equal to or less than the thickness of the other piezoelectric layers.   4. The liquid jet head according to claim 1, wherein a thickness of the piezoelectric layer that is an outermost layer constituting the piezoelectric element is 5 μm or more. 5.   The liquid ejecting head according to claim 1, wherein the piezoelectric element is deformed by a reverse piezoelectric effect in a d31 direction of the piezoelectric layer.   5. The liquid jet head according to claim 1, wherein the piezoelectric element is deformed by a reverse piezoelectric effect in a d33 direction of the piezoelectric layer.   A liquid ejecting apparatus including the liquid ejecting head according to claim 1.   A plurality of piezoelectric layers and first and second internal electrodes alternately arranged between the piezoelectric layers, and each of the outermost piezoelectric layers is inactive so as not to undergo piezoelectric deformation. A piezoelectric element configured to be a layer, and wherein the thickness of at least one of the outermost piezoelectric layers is equal to or less than the thickness of a piezoelectric layer other than the outermost layer.

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