Liquid ejection head

Abstract

To improve reliability of a liquid discharge head.SOLUTION: The liquid discharge head includes a piezoelectric element that applies a pressure to a pressure chamber communicating with a nozzle that discharges liquid, a lead electrode that is bonded to each of a wiring substrate that supplies a drive signal for driving the piezoelectric element and the piezoelectric element, and an underlayer disposed below the lead electrode, an upper surface of the underlayer has a first uneven surface, an upper surface of the lead electrode has a second uneven surface having a shape derived from the first uneven surface, the wiring substrate is bonded to the second uneven surface, and the underlayer is made of a non-metallic and insulating material.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a liquid ejection head. [Background technology]

[0002] In a liquid ejection head, such as a piezoelectric inkjet head, a piezoelectric element that applies pressure to a pressure chamber connected to a nozzle that ejects liquid is generally electrically connected to a wiring board that supplies a drive signal to the piezoelectric element. For example, Patent Document 1 discloses a configuration in which a wiring board is bonded to lead electrodes electrically connected to the piezoelectric element using a non-conductive adhesive. Here, the lead electrodes are formed on a plurality of protrusions made of the same material as the piezoelectric layer and electrodes of the piezoelectric element, and an uneven surface is formed on the bonding surface of the lead electrodes with the wiring board due to the plurality of protrusions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-128133 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration of Patent Document 1, since metal is present on the surface of the protrusion, there is a risk that corrosion will occur between the protrusion and the lead electrode due to contact between the protrusion and the lead electrode. [Means for solving the problem]

[0005] In order to solve the above problems, a liquid ejection head according to a preferred embodiment of the present disclosure comprises a piezoelectric element that applies pressure to a pressure chamber that communicates with a nozzle that ejects liquid, a wiring board that supplies a drive signal to drive the piezoelectric element and lead electrodes that are bonded to the piezoelectric element, and a base layer that is arranged below the lead electrodes, wherein the upper surface of the base layer has a first uneven surface, the upper surface of the lead electrode has a second uneven surface that is shaped like the first uneven surface, the wiring board is bonded to the second uneven surface, and the base layer is made of a non-metallic, insulating material. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of the configuration of a liquid ejection device. [Figure 2] FIG. 1 is an exploded perspective view of a liquid ejection head according to a first embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 3 is a plan view of a portion of the liquid ejection head shown in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line BB in FIG. [Figure 6] FIG. 3 is a plan view showing an example of the arrangement of the first uneven surface. [Figure 7] FIG. 10 is a cross-sectional view of a liquid ejection head according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited.

[0008] For convenience, the following description will use the mutually intersecting X-axis, Y-axis, and Z-axis as appropriate. In the following, one direction along the X-axis is the X1 direction, and the direction opposite the X1 direction is the X2 direction. Similarly, the opposite directions along the Y-axis are the Y1 direction and the Y2 direction. Furthermore, the opposite directions along the Z-axis are the Z1 direction and the Z2 direction. The Z1 direction corresponds to "upward" or "top," and the Z2 direction corresponds to "downward" or "bottom." Hereinafter, viewing in the Z1 or Z2 direction may be referred to as "planar view."

[0009] Typically, the Z axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. However, the Z axis does not have to be a vertical axis. Furthermore, the X axis, Y axis, and Z axis are typically perpendicular to each other, but are not limited to this. For example, they may intersect at an angle between 80° and 100°.

[0010] A: First embodiment A1: Overall configuration of the liquid ejection device 1 is a schematic diagram showing an example of the configuration of a liquid ejection device 100. The liquid ejection device 100 is an inkjet printing device that ejects ink, which is an example of a "liquid," in the form of droplets toward a recording medium M. The recording medium M is, for example, printing paper. Note that the recording medium M is not limited to printing paper, and may be a printing target made of any material, such as a resin film or fabric.

[0011] As shown in FIG. 1, the liquid ejection device 100 includes a liquid container 10, a control module 20, a transport mechanism 30, a moving mechanism 40, and a plurality of liquid ejection heads 50.

[0012] The liquid container 10 stores ink. Specific examples of the liquid container 10 include a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. The type of ink stored in the liquid container 10 is arbitrary.

[0013] The control module 20 controls the operation of each element of the liquid ejection device 100. The control module 20 includes, for example, a processing circuit such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and a storage circuit such as a semiconductor memory. Here, the control module 20 outputs a drive signal Com for driving the liquid ejection head 50, and a control signal SI for controlling the driving of the liquid ejection head 50.

[0014] The transport mechanism 30 transports the recording medium M along the Y axis under the control of the control module 20.

[0015] The movement mechanism 40 reciprocates the liquid ejection head 50 along the X axis under the control of the control module 20. The movement mechanism 40 has a substantially box-shaped transport body 41 called a carriage that houses the liquid ejection head 50, and an endless transport belt 42 to which the transport body 41 is fixed. The number of liquid ejection heads 50 mounted on the transport body 41 is not limited to one, and may be multiple. In addition to the liquid ejection head 50, the transport body 41 may also be equipped with the aforementioned liquid container 10.

[0016] Each of the plurality of liquid ejection heads 50 ejects ink supplied from the liquid container 10 from each of the plurality of nozzles N onto the recording medium M under the control of the control module 20. This ejection is performed in parallel with the transport of the recording medium M by the transport mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the movement mechanism 40, thereby forming an ink image on the surface of the recording medium M.

[0017] In the example shown in Fig. 1, the number of liquid ejection heads 50 is four. The number of liquid ejection heads 50 is not limited to the example shown in Fig. 1 and may be any number, and may be one, or a plurality of three or less, or five or more. The arrangement of the plurality of liquid ejection heads 50 is also not limited to the example shown in Fig. 1 and may be any arrangement.

[0018] A2: Liquid ejection head Fig. 2 is an exploded perspective view of the liquid ejection head 50 according to the first embodiment. Fig. 3 is a cross-sectional view taken along line AA in Fig. 2. An example of the configuration of the liquid ejection head 50 will now be described.

[0019] As shown in FIGS. 2 and 3, the liquid ejection head 50 has a plurality of nozzles N arranged in a direction along the Y axis.

[0020] The multiple nozzles N of the liquid ejection head 50 are divided into a first nozzle row Ln1 and a second nozzle row Ln2 that are arranged at intervals along the X-axis. Each of the first nozzle row Ln1 and the second nozzle row Ln2 is a collection of multiple nozzles N that are linearly arranged along the Y-axis.

[0021] The liquid ejection heads 50 are configured to be substantially symmetrical with respect to each other in the direction along the X-axis. However, the positions of the multiple nozzles N of the first nozzle row Ln1 and the multiple nozzles N of the second nozzle row Ln2 in the direction along the Y-axis may or may not match. 2 and 3 illustrate a configuration in which the positions of the multiple nozzles N of the first nozzle row Ln1 and the multiple nozzles N of the second nozzle row Ln2 in the direction along the Y-axis match each other.

[0022] As shown in FIGS. 2 and 3, the liquid ejection head 50 has a communication substrate 510, a pressure chamber substrate 520, a nozzle plate 530, a vibration absorber 540, a vibration plate 550, a plurality of piezoelectric elements 560, a protection substrate 570, a case 580, and a wiring substrate 590.

[0023] The communication substrate 510 and the pressure chamber substrate 520 are stacked in this order in the Z1 direction to form a flow path for supplying ink to the multiple nozzles N. A vibration plate 550, multiple piezoelectric elements 560, a protective substrate 570, a case 580, a wiring substrate 590, and a drive circuit 600 are installed in an area positioned in the Z1 direction from the stack consisting of the communication substrate 510 and the pressure chamber substrate 520. On the other hand, a nozzle plate 530 and a vibration absorber 540 are installed in an area positioned in the Z2 direction from the stack. Each element of the liquid ejection head 50 is roughly a plate-like member elongated in the Y direction and is joined to each other, for example, by an adhesive. Each element of the liquid ejection head 50 will be described in order below.

[0024] The nozzle plate 530 is a plate-like member provided with a plurality of nozzles N of each of the first nozzle row Ln1 and the second nozzle row Ln2. Each of the plurality of nozzles N is a through-hole that allows ink to pass through. Here, the surface of the nozzle plate 530 facing the Z2 direction is the nozzle surface FN. The nozzle plate 530 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing techniques such as dry etching or wet etching. However, other known methods and materials may also be used as appropriate to manufacture the nozzle plate 530. Furthermore, the cross-sectional shape of the nozzle N is typically circular, but is not limited thereto and may be a non-circular shape such as a polygonal or elliptical shape.

[0025] The communication substrate 510 is provided with a flow path R1, a plurality of supply flow paths Ra, and a plurality of communication flow paths Na for each of the first nozzle row Ln1 and the second nozzle row Ln2. The flow path R1 is a flow path provided in common to a plurality of nozzles N, communicates with the plurality of nozzles N, and is a flow path upstream of the nozzles N, and is configured as an elongated hole extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. Each of the supply flow path Ra and the communication flow path Na is a flow path configured as a through-hole formed for each nozzle N. Each supply flow path Ra communicates with the flow path R1.

[0026] The communicating substrate 510 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example, in the same manner as the above-described nozzle plate 530. However, other known methods and materials may also be used appropriately to manufacture the communicating substrate 510.

[0027] The pressure chamber substrate 520 is a plate-like member in which a plurality of pressure chambers C, called cavities, are provided for each of the first nozzle row Ln1 and the second nozzle row Ln2. The pressure chambers C are arranged in a direction along the Y axis. Each pressure chamber C is formed for each nozzle N and is an elongated space extending in a direction along the X axis in a plan view.

[0028] The pressure chamber substrate 520 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example, in the same way as the nozzle plate 530. However, other known methods and materials may also be used appropriately to manufacture the pressure chamber substrate 520.

[0029] The pressure chambers C are located between the communication substrate 510 and the vibration plate 550. A plurality of pressure chambers C are arranged in the direction along the Y axis for each of the first nozzle row Ln1 and the second nozzle row Ln2. The pressure chambers C are also in communication with the communication flow path Na and the supply flow path Ra. Therefore, the pressure chambers C are in communication with the nozzles N via the communication flow path Na, and are in communication with the flow path R1 via the supply flow path Ra.

[0030] A vibration plate 550 is disposed on the surface facing the Z1 direction of the pressure chamber substrate 520. The vibration plate 550 is a plate-like member that can vibrate elastically, and is vibrated by a piezoelectric element 560. Details of the vibration plate 550 will be described later with reference to FIG.

[0031] On the surface of the vibration plate 550 facing the Z1 direction, a plurality of piezoelectric elements 560 corresponding to the nozzles N of each of the first nozzle row Ln1 and the second nozzle row Ln2 are arranged. Each piezoelectric element 560 is a passive element that deforms when supplied with a potential according to the drive signal Com, and generates pressure fluctuations in the ink in the pressure chambers C. Each piezoelectric element 560 has an elongated shape extending in the direction along the X axis in a plan view. The plurality of piezoelectric elements 560 are arranged in the direction along the Y axis so as to correspond to the plurality of pressure chambers C. The piezoelectric elements 560 overlap the pressure chambers C in a plan view. The above-mentioned piezoelectric elements 560 apply pressure to the pressure chambers C that communicate with the nozzles N that eject ink. Details of the piezoelectric elements 560 will be described later with reference to FIG. 5.

[0032] Protective substrate 570 is a plate-like member placed on the surface of diaphragm 550 facing the Z1 direction, and protects multiple piezoelectric elements 560 and reinforces the mechanical strength of diaphragm 550. Here, multiple piezoelectric elements 560 are housed in space S between protective substrate 570 and diaphragm 550. Protective substrate 570 is made of, for example, a resin material.

[0033] The case 580 is a case for storing ink to be supplied to the multiple pressure chambers C. The case 580 is made of, for example, a resin material. The case 580 is provided with a flow path R2 for each of the first nozzle row Ln1 and the second nozzle row Ln2. The flow path R2 is a space connected to the aforementioned flow path R1 and is formed as an elongated hole extending in the direction along the Y axis in a plan view seen in the direction along the Z axis. The flow path R2 communicates with the nozzles N and, together with the flow path R1, functions as a reservoir R for storing ink to be supplied to the multiple pressure chambers C. The case 580 is provided with an inlet HL for supplying ink to each reservoir R. The ink in each reservoir R is supplied to the pressure chambers C via each supply flow path Ra. Note that the position and number of the inlet HL for each reservoir R are not limited to the examples shown in FIGS. 2 and 3 and may be any.

[0034] The vibration absorber 540, also called a compliance substrate, is a flexible resin film that forms the wall surface of the reservoir R and absorbs pressure fluctuations of the ink inside the reservoir R. The vibration absorber 540 may also be a flexible thin metal plate. The surface of the vibration absorber 540 facing the Z1 direction is bonded to the communication substrate 510 with an adhesive or the like.

[0035] The wiring board 590 is mounted on the surface of the diaphragm 550 facing the Z1 direction and is a mounting component for electrically connecting the control module 20 and the liquid ejection head 50. The wiring board 590 is a flexible wiring board such as a COF (Chip On Film), an FPC (Flexible Printed Circuit), or an FFC (Flexible Flat Cable). A drive circuit 600 is mounted on the wiring board 590 of this embodiment. Under the control of the control module 20, the drive circuit 600 switches whether or not to supply pulses included in the drive signal Com output from the control module 20 to each of the multiple piezoelectric elements 560 of the liquid ejection head 50. As described above, the wiring board 590 supplies the drive signal Com that drives the piezoelectric elements 560. Note that the wiring board 590 may be a rigid board. In this case, the drive circuit 600 is mounted on the rigid board or on a flexible board connected to the rigid board.

[0036] A3: Electrical connection between the piezoelectric element and the wiring board Fig. 4 is a plan view of a part of the liquid ejection head 50 shown in Fig. 2. Fig. 5 is a cross-sectional view taken along line BB in Fig. 4. Fig. 6 is a plan view showing an example of the arrangement of the first concave-convex surface.

[0037] As shown in FIGS. 4 and 5, the liquid ejection head 50 has lead electrodes 91 and common wiring 92 in addition to the above-mentioned components.

[0038] Before describing the lead electrodes 91 and the common wiring 92, the diaphragm 550 and the piezoelectric element 560 will be described below.

[0039] As shown in FIG. 5, diaphragm 550 has elastic film 551 and insulating film 552, which are laminated in this order in the Z1 direction.

[0040] The elastic film 551 is made of, for example, silicon oxide (SiO2) and is formed by thermally oxidizing one surface of a silicon single crystal substrate. The insulating film 552 is made of, for example, zirconium oxide (ZrO2) and is formed by forming a zirconium layer by sputtering and then thermally oxidizing the layer.

[0041] Note that diaphragm 550 is not limited to the configuration of a laminate of elastic film 551 and insulating film 552 described above, and may be configured, for example, as a single layer, or as three or more layers. Furthermore, the material of each layer constituting diaphragm 550 is not limited to the materials described above, and may be, for example, silicon or silicon nitride. For example, as a material constituting insulating film 552, TiO2, Al2O3, SiO2, SiN, etc., can be used in addition to ZrO2.

[0042] A plurality of piezoelectric elements 560 are arranged on the surface of the above-described vibration plate 550 facing the Z1 direction. As shown in Fig. 5, each piezoelectric element 560 has a lower electrode 561, a piezoelectric body 562, and an upper electrode 563, which are stacked in this order in the Z1 direction. Therefore, the piezoelectric body 562 is arranged between the lower electrode 561 and the upper electrode 563.

[0043] The lower electrodes 561 are individual electrodes spaced apart from one another and arranged for each piezoelectric element 560. A supply drive signal Vin corresponding to the drive signal Com is supplied to the lower electrodes 561. The upper electrode 563 is a strip-shaped common electrode extending continuously along the Y-axis across the plurality of piezoelectric elements 560. A constant potential, for example, is supplied to the upper electrode 563. Examples of metal materials for these electrodes include platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), copper (Cu), etc., and one of these can be used alone or two or more can be combined in the form of an alloy or a laminate.

[0044] The piezoelectric body 562 is made of a piezoelectric material such as lead zirconate titanate (Pb(Zr,Ti)O3). In the example shown in Fig. 4, the piezoelectric body 562 is in the form of a strip extending in the direction along the Y-axis so as to be continuous across the plurality of piezoelectric elements 560. Here, the piezoelectric body 562 is provided with through-holes 562a that extend through the piezoelectric body 562 in the direction along the X-axis in regions that correspond in plan view to the gaps between adjacent pressure chambers C. Note that the piezoelectric body 562 may be provided individually for each piezoelectric element 560.

[0045] In such a piezoelectric element 560, when a voltage is applied between the lower electrode 561 and the upper electrode 563, the piezoelectric body 562 is deformed by the inverse piezoelectric effect. When the vibration plate 550 vibrates in conjunction with this deformation, the pressure in the pressure chamber C fluctuates, causing ink to be ejected from the nozzle N.

[0046] 4, the above-described piezoelectric element 560 is electrically connected to a wiring substrate 590 via a lead electrode 91 and a common wiring 92. Here, the lead electrode 91 and the common wiring 92 are bonded to the wiring substrate 590 and the piezoelectric element 560, respectively.

[0047] The lead electrode 91 is provided individually for each piezoelectric element 560 and is electrically connected to the lower electrode 561 of the corresponding piezoelectric element 560. On the other hand, the common wiring 92 is provided in common to the plurality of piezoelectric elements 560 and is electrically connected to the upper electrode 563.

[0048] The lead electrodes 91 and the common wiring 92 are disposed at intervals from each other. Here, it is preferable that the lead electrodes 91 and the common wiring 92 are formed collectively in the same film formation process. In this case, the manufacturing process of the liquid ejection head 50 can be simplified, and as a result, the cost of the liquid ejection head 50 can be reduced.

[0049] The lead electrode 91 has an electrode layer 91a and an adhesive layer 91b. These are stacked in the Z1 direction in the order of adhesive layer 91b and electrode layer 91a. Similarly, the common wiring 92 has an electrode layer 92a and an adhesive layer 92b. These are stacked in the Z1 direction in the order of adhesive layer 92b and electrode layer 92a.

[0050] Each of the electrode layers 91a, 92a is a conductive layer. The material of each of the electrode layers 91a, 92a may be any conductive material, and is not particularly limited, but examples thereof include metals such as gold (Au), copper (Cu), titanium (Ti), tungsten (W), nickel (Ni), chromium (Cr), platinum (Pt), and aluminum (Al). Among these, gold (Au) is preferably used as the material of the lead electrode 91 and the common wiring 92.

[0051] Adhesion layers 91b and 92b are layers for increasing the adhesion between electrode layers 91a and 92a and vibration plate 550. For example, when electrode layers 91a and 92a are made of gold, nickel chrome is preferably used as the material for adhesion layers 91b and 92b. Note that the material for adhesion layers 91b and 92b is not limited to nickel chrome and may be, for example, nickel, chrome, a nickel alloy, or a chrome alloy.

[0052] The adhesive layer 91b is disposed between the base layer 5 and the electrode layer 91a. By disposing the adhesive layer 91b between the base layer 5 in this way, the adhesiveness between the lead electrode 91 and the base layer 5 is improved, and therefore, penetration of moisture into the interface can be suppressed.

[0053] When the electrode layer 91a is made of gold, the adhesion layer 91b is preferably made of nickel chrome. This allows for improved adhesion between the electrode layer 91a and the base layer 5, even when the electrode layer 91a is made of gold. Nickel chrome also has a relatively high ionization tendency (i.e., a relatively high natural potential), making it susceptible to corrosion. Therefore, as will be described later, making the base layer 5 out of a nonmetallic, insulating material significantly reduces corrosion of the lead electrode 91.

[0054] 4 and 5, lead electrode 91 is connected to lower electrode 561 and is drawn out for each piezoelectric element 560 from above lower electrode 561 in a direction toward wiring substrate 590 onto diaphragm 550. On the other hand, common wiring 92 is drawn out from above upper electrode 563 in a direction toward wiring substrate 590 onto diaphragm 550 at both ends of upper electrode 563 in the Y1 direction and Y2 direction, as shown in FIG.

[0055] 5, an underlayer 5 is disposed below the lead electrode 91. In this embodiment, the underlayer 5 is integrally formed with an insulating film 552 of the vibration plate 550. In other words, the insulating film 552 functions as the underlayer 5 below the lead electrode 91. In this manner, the liquid ejection head 50 includes the underlayer 5.

[0056] In this way, since the diaphragm 550 includes the base layer 5, the manufacturing process of the liquid ejection head 50 can be simplified compared to an embodiment in which the base layer 5 is formed separately from the diaphragm 550. Furthermore, compared to an embodiment in which a layer separate from the layer that constitutes the diaphragm 550 is used, the amount of adhesive used to bond the wiring board 590 and the lead electrodes 91 can be reduced.

[0057] As shown in FIG. 5, the upper surface of the underlayer 5, that is, the surface of the underlayer 5 facing the Z1 direction, has a first uneven surface F1.

[0058] The first uneven surface F1 is formed by the base layer 5 having a plurality of protrusions 60. Each of the plurality of protrusions 60 is a convex portion provided on the surface of the base layer 5 facing the Z1 direction. In the example shown in FIG. 5, each of the protrusions 60 has a shape that narrows toward the tip. The plurality of protrusions 60 are arranged along the longitudinal direction of the lead electrode 91. A recess is provided between two adjacent protrusions 60 among the plurality of protrusions 60. Furthermore, as shown in FIG. 6, each of the protrusions 60 overlaps with the lead electrode 91 in plan view. In the example shown in FIG. 6, each of the protrusions 60 has a rectangular shape in plan view. The shape of the protrusions 60 is not limited to the examples shown in FIGS. 5 and 6 and may be any shape.

[0059] In this embodiment, the height H1 of each protrusion 60 is smaller than the thickness of the insulating film 552, and preferably is 0.3 to 0.9 times the thickness of the insulating film 552.

[0060] The method for forming such base layer 5 may be, for example, a method in which a material constituting base layer 5 is deposited using a mask made of resist or the like, and then the mask is removed to form a patterned base layer 5, or a method in which the material constituting base layer 5 is deposited uniformly, and then patterned by etching or the like to form base layer 5. Note that base layer 5 does not have to be a layer that constitutes diaphragm 550, and may be a layer separate from the layer that constitutes diaphragm 550.

[0061] The upper surface of the lead electrode 91, i.e., the surface of the lead electrode 91 facing the Z1 direction, has a second uneven surface F2 whose shape is derived from the first uneven surface F1. The shape derived from the first uneven surface F1 is a shape having convex portions at positions that overlap with convex portions of the first uneven surface F1 in a plan view, or a shape having concave portions at positions that overlap with concave portions of the first uneven surface F1 in a plan view, and is typically a shape that follows the first uneven surface F1 or a shape that is approximate to the first uneven surface F1.

[0062] The second uneven surface F2 is formed by the lead electrode 91 having a plurality of protrusions 70. Each of the plurality of protrusions 70 is a convex portion provided on the surface of the lead electrode 91 facing the Z1 direction. In the example shown in FIG. 5, each of the protrusions 70 has a shape that narrows toward the tip. The plurality of protrusions 70 are arranged along the longitudinal direction of the lead electrode 91. A recess is provided between two adjacent protrusions 70 among the plurality of protrusions 70. Although not shown, each of the protrusions 70 has a shape corresponding to the protrusion 60, i.e., a substantially rectangular shape, in plan view. The shape of the protrusions 70 is not limited to the examples shown in FIGS. 5 and 6 and may be any shape.

[0063] In this embodiment, the height H2 of each protrusion 70 is approximately the same as the height H1 of the protrusion 60, and specifically, is 0.8 to 1.2 times the height H1.

[0064] Such a second uneven surface F2 is formed, for example, by depositing a film of the lead electrode 91 on the first uneven surface F1. That is, the second uneven surface F2 is formed by depositing the constituent material of the lead electrode 91 under the influence of the shape of the first uneven surface F1.

[0065] The wiring substrate 590 is bonded to the second uneven surface F2 with adhesive B. As a result, the recesses of the second uneven surface F2 function as escape grooves when the adhesive B is pressed, ensuring reliable contact between the protrusions 70 of the second uneven surface F2 and the wiring substrate 590. Therefore, even if the adhesive B is a non-conductive adhesive, a reliable electrical connection can be achieved between the lead electrodes 91 and the wiring substrate 590. Here, by using a non-conductive adhesive such as an epoxy adhesive as the adhesive B, the pitch between the multiple lead electrodes 91 can be shortened. As a result, the pitch of the nozzles N can be narrowed.

[0066] The underlayer 5 is made of a non-metallic, insulating material. This reduces corrosion of the lead electrodes 91 due to contact between the lead electrodes 91 and the underlayer 5, even if moisture penetrates between the lead electrodes 91 and the underlayer 5. This corrosion is, for example, bimetallic corrosion, also known as galvanic corrosion. Reducing corrosion of the lead electrodes 91 in this way improves the reliability of the liquid ejection head 50.

[0067] In this embodiment, the base layer 5 is made of the same material as the insulating film 552. Here, the material making up the base layer 5 is preferably any one of ZrO2, TiO2, Al2O3, SiO2, and SiN, which allows the base layer 5 to function suitably as part of the diaphragm 550.

[0068] When the material constituting the underlayer 5 is ZrO2, there is an advantage that the underlayer 5 is less likely to dissolve or decompose because ZrO2 has a relatively high chemical stability.

[0069] The base layer 5 may be provided separately from the insulating film 552, or may be made of a different material from the insulating film 552. The material making up the base layer 5 may be a non-metallic, insulating material, such as an oxide, nitride, or oxynitride other than the above-mentioned materials, or a piezoelectric material such as Pb(Zr,Ti)O3. The material making up the base layer 5 may contain impurities in addition to the above-mentioned materials.

[0070] In this embodiment, the base layer 5 is composed of a single layer, and therefore there is no interface within the base layer 5, which reduces the penetration of moisture into the base layer 5. The base layer 5 may be composed of two or more layers as long as it is composed of a non-metallic, insulating material. The constituent material of the layers below the base layer 5 may be a metal or a conductive material.

[0071] B: Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiment, for elements whose actions and functions are similar to those of the first embodiment, the reference numerals used in the description of the first embodiment will be used, and detailed descriptions of each element will be omitted as appropriate.

[0072] 7 is a cross-sectional view of a liquid ejection head 50A according to the second embodiment. The liquid ejection head 50 has the same configuration as the liquid ejection head 50 of the first embodiment, except that it includes a vibration plate 550A instead of the vibration plate 550 of the first embodiment, and that it also includes a plurality of protrusions 60A and a base layer 5A.

[0073] Diaphragm 550A is configured similarly to diaphragm 550 of the first embodiment, except that it includes insulating film 553 instead of insulating film 552 of the first embodiment. Insulating film 553 is configured similarly to insulating film 552 of the first embodiment, except that the shape in plan view is different.

[0074] Diaphragm 550A has a region where insulating film 553 is provided on elastic film 551, and a region where insulating film 553 is not provided on elastic film 551. Piezoelectric element 560 is provided on diaphragm 550A in the region where insulating film 553 is provided on elastic film 551. On the other hand, base layer 5A and a plurality of protrusions 60A are provided on diaphragm 550A in the region where insulating film 553 is not provided on elastic film 551.

[0075] Like the underlayer 5 of the first embodiment, the underlayer 5A is made of a nonmetallic insulating material such as an oxide, nitride, or oxynitride. For example, the underlayer 5A is made of Al2O3. This reduces corrosion of the lead electrode 91 due to contact between the lead electrode 91 and the underlayer 5A, even if moisture penetrates between the lead electrode 91 and the underlayer 5A.

[0076] The base layer 5A is a moisture-resistant protective film that protects the surface of the diaphragm 550A. This reduces corrosion of the diaphragm 550A. Furthermore, compared to an embodiment in which the base layer 5A is provided separately from the protective film, the manufacturing process for the liquid ejection head 50A can be simplified. Note that the base layer 5A may be a layer separate from the protective film.

[0077] Furthermore, the underlayer 5A is preferably made of the same material as the moisture-resistant protective film that protects the surface of the lower electrode 561 or the upper electrode 563. This simplifies the manufacturing process of the liquid ejection head 50A.

[0078] As shown in FIG. 7, the upper surface of the underlayer 5A, that is, the surface of the underlayer 5 facing the Z1 direction, has a first uneven surface F1.

[0079] The first uneven surface F1 of this embodiment is formed by a plurality of protrusions 60A provided below the base layer 5A. Each of the plurality of protrusions 60A is a convex portion disposed between the base layer 5A and the diaphragm 550A. In the example shown in FIG. 7, each of the protrusions 60A has a shape that narrows toward the tip. The plurality of protrusions 60A are arranged along the longitudinal direction of the lead electrode 91. A recess is provided between two adjacent protrusions 60A among the plurality of protrusions 60A. Furthermore, each of the protrusions 60A overlaps with the lead electrode 91 in plan view. Note that the shape of the protrusions 60A is not limited to the example shown in FIG. 7 and may be any shape. Furthermore, the shape of the protrusions 60A in plan view may also be any shape.

[0080] Each protrusion 60A is composed of multiple laminated layers. In the example shown in FIG. 7, each protrusion 60A has layers 61, 62, and 63. The constituent materials of layers 61, 62, and 63 are not particularly limited and may be any material, and may be non-metallic or metallic, and may be insulating or conductive. The number of layers constituting each protrusion 60A is not limited to the example shown in FIG. 7 and may be two or less layers or four or more layers.

[0081] The constituent material of at least one of the layers 61, 62, and 63 is preferably the same material as the lower electrode 561 or the upper electrode 563. In this way, by forming the plurality of protrusions 60A from the same material as the lower electrode 561 or the upper electrode 563, the manufacturing process of the liquid ejection head 50A can be simplified even if the unevenness is formed on the base layer 5A using a layer separate from the base layer 5A.

[0082] The plurality of protrusions 60A provided below the base layer 5A are not limited to being made of the same material as the vibration plate 550A or the electrodes, but may be provided on a layer separate from the vibration plate 550A and the electrodes, or may be provided on a substrate such as the pressure chamber substrate 520.

[0083] The second embodiment described above also makes it possible to improve the reliability of the liquid ejection head 50A.

[0084] F: Variation The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Any of the following embodiments can be combined as desired within the scope of their mutual compatibility.

[0085] F1: Variation 1 In the above-described embodiment, the upper electrode 563 is a common electrode, but the present invention is not limited to this, and the upper electrode 563 may be an individual electrode for each piezoelectric element 650. In this case, the lower electrode 561 may be a common electrode shared by the plurality of piezoelectric elements 560.

[0086] F2: Variation 2 In the above-described embodiment, an example is given in which a common wiring substrate 590 is used for the first nozzle row Ln1 and the second nozzle row Ln2, but this is not limited to this example, and separate wiring substrates 590 may be used for the first nozzle row Ln1 and the second nozzle row Ln2.

[0087] F3: Variation 3 In each of the above-described embodiments, a serial-type liquid ejection device 100 in which a transport body 41 equipped with a liquid ejection head 50 moves back and forth has been exemplified, but the present disclosure can also be applied to a line-type liquid ejection device in which multiple nozzles N are distributed across the entire width of the recording medium M.

[0088] F4: Variation 4 The liquid ejection device 100 exemplified in the above embodiment may be employed in various devices such as facsimile machines and copiers, in addition to devices dedicated to printing, and the applications of the present disclosure are not particularly limited. However, the applications of the liquid ejection device are not limited to printing. For example, a liquid ejection device that ejects a solution of a color material is used as a manufacturing device for forming color filters for display devices such as liquid crystal display panels. Furthermore, a liquid ejection device that ejects a solution of a conductive material is used as a manufacturing device for forming wiring and electrodes on a wiring board. Furthermore, a liquid ejection device that ejects a solution of an organic substance related to a living body is used as a manufacturing device for manufacturing biochips, for example.

[0089] G: Notes A summary of this disclosure is provided below.

[0090] (Appendix 1) A first aspect, which is a preferred example of the liquid ejection head of the present disclosure, comprises a piezoelectric element that applies pressure to a pressure chamber that communicates with a nozzle that ejects liquid, a wiring board that supplies a drive signal to drive the piezoelectric element and lead electrodes that are bonded to the piezoelectric element, and a base layer that is arranged below the lead electrodes, wherein the upper surface of the base layer has a first uneven surface, the upper surface of the lead electrode has a second uneven surface that is shaped like the first uneven surface, the wiring board is bonded to the second uneven surface, and the base layer is made of a non-metallic, insulating material.

[0091] In the above-described embodiment, since the base layer is made of a non-metallic, insulating material, even if moisture penetrates between the lead electrode and the base layer, corrosion of the lead electrode due to contact between the lead electrode and the base layer can be reduced, thereby improving the reliability of the liquid ejection head.

[0092] (Note 2) In a second aspect, which is a preferred example of the first aspect, the lead terminal has an adhesive layer disposed between the lead terminal and the base layer. In this aspect, the adhesiveness between the lead terminal and the base layer is improved, thereby preventing moisture from penetrating the interface.

[0093] (Appendix 3) In a third aspect, which is a preferred example of the second aspect, the lead electrode has an electrode layer made of gold, and the adhesion layer is disposed between the base layer and the electrode layer and made of nickel chromium. In the above aspect, even if the electrode layer is made of gold, the adhesion between the electrode layer and the base layer can be improved. Furthermore, nickel chromium has a relatively high ionization tendency (i.e., a relatively high natural potential), and therefore is prone to corrosion. Therefore, by making the base layer out of a nonmetallic, insulating material, the effect of reducing corrosion of the lead electrode is significantly achieved.

[0094] (Note 4) In a fourth aspect, which is a preferred example of any of the first to third aspects, the material constituting the underlayer is any of ZrO2, TiO2, Al2O3, SiO2, and SiN. In the above aspect, the underlayer can be made to function favorably as part of the diaphragm.

[0095] (Supplementary Note 5) In a fifth aspect, which is a preferred example of any of the first to fourth aspects, the liquid ejection head further includes a vibration plate that vibrates due to the piezoelectric element, and the vibration plate includes the base layer. In this aspect, the manufacturing process of the liquid ejection head can be simplified compared to an aspect in which the base layer is formed separately from the vibration plate.

[0096] (Note 6) In a sixth aspect, which is a preferred example of the fifth aspect, the material constituting the underlayer is ZrO2. This aspect has the advantage that the underlayer is less likely to dissolve or decompose because ZrO2 has relatively high chemical stability.

[0097] (Supplementary Note 7) In a seventh aspect, which is a preferred example of any of the first to fourth aspects, the device includes a diaphragm that vibrates due to the piezoelectric element, and the base layer is a moisture-resistant protective film that protects the surface of the diaphragm. In the above aspect, corrosion of the diaphragm can be reduced.

[0098] (Appendix 8) In an eighth aspect, which is a preferred example of any of the first to seventh aspects, the piezoelectric element has a lower electrode, an upper electrode, and a piezoelectric body disposed between the lower electrode and the upper electrode, and below the base layer are provided a plurality of protrusions made of the same material as the lower electrode or the upper electrode, and the base layer is made of the same material as a moisture-resistant protective film that protects the surface of the lower electrode or the upper electrode. In the above aspect, because the plurality of protrusions are made of the same material as the lower electrode or the upper electrode, the manufacturing process of the liquid ejection head can be simplified even if the unevenness is formed on the base layer using a layer separate from the base layer.

[0099] (Supplementary Note 9) In a ninth aspect, which is a preferred example of any of the first to eighth aspects, the underlayer is composed of a single layer. In the above aspect, since there is no interface within the underlayer, it is possible to reduce the penetration of moisture into the underlayer. [Explanation of symbols]

[0100] 5...underlayer, 5A...underlayer, 10...liquid container, 20...control module, 30...transport mechanism, 40...movement mechanism, 41...transport body, 42...transport belt, 50...liquid ejection head, 50A...liquid ejection head, 60...protrusion, 60A...protrusion, 61...layer, 62...layer, 63...layer, 70...protrusion, 91...lead electrode, 91a...electrode layer, 91b...adhesion layer, 92...common wiring, 92a...electrode layer, 92b...adhesion layer, 100...liquid ejection device, 510...communicating substrate, 520...pressure chamber substrate, 530...nozzle plate, 540...vibration absorber, 550...vibration plate, 550A...vibration plate, 551...elastic film, 552...insulating film, 55 3...insulating film, 560...piezoelectric element, 561...lower electrode, 562...piezoelectric body, 562a...through hole, 563...upper electrode, 570...protective substrate, 580...case, 590...wiring substrate, 600...drive circuit, 650...piezoelectric element, B...adhesive, C...pressure chamber, Com...drive signal, F1...first uneven surface, F2...second uneven surface, FN...nozzle surface, H1...height, H2...height, HL...inlet, Ln1...first nozzle row, Ln2...second nozzle row, M...recording medium, N...nozzle, Na...communicating flow path, R...reservoir, R1...flow path, R2...flow path, Ra...supply flow path, S...space, SI...control signal, Vin...supply drive signal.

Claims

1. a piezoelectric element that applies pressure to a pressure chamber that communicates with a nozzle that ejects liquid; lead electrodes bonded to a wiring board that supplies a drive signal for driving the piezoelectric element and to the piezoelectric element; a base layer disposed below the lead electrode, an upper surface of the underlayer having a first uneven surface; an upper surface of the lead terminal has a second uneven surface having a shape derived from the first uneven surface; the wiring substrate is bonded to the second uneven surface; the underlayer is made of a non-metallic, insulating material; A liquid ejection head characterized by:

2. The lead electrode has an adhesive layer disposed between the lead electrode and the base layer.

2. The liquid ejection head according to claim 1.

3. the lead electrode has an electrode layer made of gold, the adhesion layer is disposed between the base layer and the electrode layer and is made of nickel chromium; 3. The liquid ejection head according to claim 2.

4. The material constituting the underlayer is ZrO ２ , TiO ２ , Al ２ O ３ , SiO ２ , SiN, 4. The liquid ejection head according to claim 1, wherein the ink is a liquid having a thickness of 100 nm or less.

5. a vibration plate vibrated by the piezoelectric element, The diaphragm includes the base layer.

4. The liquid ejection head according to claim 1, wherein the ink is a liquid having a thickness of 100 nm or less.

6. The material constituting the underlayer is ZrO ２ That is, 6. The liquid ejection head according to claim 5.

7. a vibration plate vibrated by the piezoelectric element, The underlayer is a moisture-resistant protective film that protects the surface of the diaphragm.

4. The liquid ejection head according to claim 1, wherein the ink is a liquid having a thickness of 100 nm or less.

8. The piezoelectric element is A lower electrode; an upper electrode; a piezoelectric body disposed between the lower electrode and the upper electrode, a plurality of protrusions made of the same material as the lower electrode or the upper electrode are provided below the underlayer; the underlayer is made of the same material as a moisture-resistant protective film that protects the surface of the lower electrode or the upper electrode; 4. The liquid ejection head according to claim 1, wherein the ink is a liquid having a thickness of 100 nm or less.

9. The underlayer is composed of one layer.

4. The liquid ejection head according to claim 1, wherein the ink is a liquid having a thickness of 100 nm or less.

Images