Liquid discharge head

Abstract

To improve displacement characteristics of a diaphragm while suppressing damage to a lower surface of the diaphragm and wall surfaces of a pressure chamber substrate.SOLUTION: A liquid discharge head comprises: an energy generating element that generates energy for applying pressure to liquid in a pressure chamber; a diaphragm that vibrates due to the energy; a pressure chamber substrate that has wall surfaces coming into contact with part of a bottom surface of the diaphragm, and defines the pressure chamber; and a protective film provided so as to cover both the bottom surface of the diaphragm and the wall surfaces of the pressure chamber substrate. The bottom surface of the diaphragm is provided with a bottom part having a flat shape and a curved part having a curved shape adjacent to the bottom part in a shorter side direction of the pressure chamber. The thickness of the protective film at a first position, which is located at the center of the bottom part in the shorter side direction of the pressure chamber, is a first thickness, and the thickness of the protective film at a second position, where the curved part is disposed, is a second thickness that is thinner than the first thickness.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses an inkjet recording head including an ink cavity in which ink is stored and an actuator that changes the pressure in the ink cavity. In this inkjet recording head, a film having hydrophilicity and alkali resistance is formed on the inner wall surface of the ink cavity.

[0003] Patent Document 2 discloses a liquid ejection head including an energy generation element that generates energy for applying pressure to a liquid in a pressure chamber, a diaphragm that vibrates by the energy, and a pressure chamber substrate that is in contact with a part of the bottom surface of the diaphragm. In this liquid ejection head, a concave portion having a bottom portion and a curved portion in the shape of a curved surface surrounding the bottom portion is provided on the bottom surface of the diaphragm.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the liquid ejection head described in Patent Document 2, since the diaphragm is easily bent at the curved portion, there is an advantage that the displacement characteristics are improved. However, in such a liquid ejection head, if a protective film is formed to have a uniform thickness as in Patent Document 1, there is a disadvantage that the displacement of the diaphragm is inhibited by the protective film.

Means for Solving the Problems

[0006] One aspect of the liquid ejection head of the present disclosure includes an energy generation element that generates energy for applying pressure to the liquid in the pressure chamber, a diaphragm that vibrates by the energy, a pressure chamber substrate that has a wall surface in contact with a part of the bottom surface of the diaphragm and partitions the pressure chamber, and a protective film provided so as to cover the bottom surface of the diaphragm and the wall surface of the pressure chamber substrate. In the liquid ejection head, a bottom portion having a planar shape and a curved portion adjacent to the bottom portion in the short side direction of the pressure chamber and having a curved surface shape are provided on the bottom surface of the diaphragm. The thickness of the protective film at a first position that is the center of the bottom portion in the short side direction of the pressure chamber is a first thickness, and the thickness of the protective film at a second position where the curved portion is disposed is a second thickness that is thinner than the first thickness.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0008] Hereinafter, preferred embodiments according to the present disclosure will be described with reference to the accompanying drawings. Note that the dimensions and scales of each part in the drawings are appropriately different from the actual ones, and there are also some parts schematically shown for easy understanding. Also, the scope of the present disclosure is not limited to these forms unless otherwise specified in the following description.

[0009] In the following description, the X-axis, Y-axis, and Z-axis that intersect each other are appropriately used. Also, in the following, one direction along the X-axis is the X1 direction, and the direction opposite to the X1 direction is the X2 direction. Similarly, the directions opposite to each other along the Y-axis are the Y1 direction and the Y2 direction. Also, the directions opposite to each other along the Z-axis are the Z1 direction and the Z2 direction. The Z1 direction is an example of the "lamination direction". Also, looking in the direction along the Z-axis may be referred to as "plan view".

[0010] Typically, the Z-axis is the vertical axis, and the Z2 direction corresponds to vertically downward. However, the Z-axis does not have to be the vertical axis. Also, the X-axis, Y-axis, and Z-axis typically intersect each other at right angles, but are not limited thereto, and for example, they may intersect at an angle within the range of 80° or more and 100° or less.

[0011] 1. Embodiment 1-1. Overall Configuration of Liquid Discharge Device FIG. 1 is a configuration diagram schematically showing a liquid discharge device 100 including a liquid discharge head 50 according to an embodiment. The liquid discharge device 100 is an inkjet printing device that discharges ink, which is an example of "liquid", as droplets onto a medium M. The medium M is typically printing paper. Note that the medium M is not limited to printing paper, and may be a printing target of any material such as a resin film or cloth.

[0012] As shown in FIG. 1, the liquid discharge device 100 includes a liquid container 10, a control unit 20, a conveyance mechanism 30, a movement mechanism 40, and a liquid discharge head 50.

[0013] The liquid container 10 is a container for storing ink. Specific examples of the liquid container 10 include, for example, a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack formed of a flexible film, and an ink tank that can be refilled with ink. Note that the type of ink stored in the liquid container 10 is not particularly limited and is arbitrary.

[0014] The control unit 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, and controls the operations of the respective elements of the liquid ejection device 100.

[0015] The conveyance mechanism 30 conveys the medium M in the Y2 direction under the control of the control unit 20. The moving mechanism 40 reciprocates the liquid ejection head 50 in the X1 direction and the X2 direction under the control of the control unit 20. In the example shown in FIG. 1, the moving mechanism 40 includes a substantially box-shaped carriage 41 that houses the liquid ejection head 50 and a conveyance belt 42 to which the carriage 41 is fixed. Note that the number of liquid ejection heads 50 mounted on the carriage 41 is not limited to one and may be a plurality. Further, in addition to the liquid ejection head 50, the aforementioned liquid container 10 may be mounted on the carriage 41.

[0016] The liquid ejection head 50 ejects the ink supplied from the liquid container 10 in the Z2 direction from each of a plurality of nozzles onto the medium M under the control of the control unit 20. By performing this ejection in parallel with the conveyance of the medium M by the conveyance mechanism 30 and the reciprocating movement of the liquid ejection head 50 by the moving mechanism 40, an image made of ink is formed on the surface of the medium M. Note that the configuration and manufacturing method of the liquid ejection head 50 will be described in detail later.

[0017] 1-2. Overall Configuration of Liquid Ejection Head FIG. 2 is an exploded perspective view of a liquid ejection head 50 according to an embodiment. FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2. As shown in FIGS. 2 and 3, the liquid ejection head 50 includes a flow path substrate 51, a pressure chamber substrate 52, a nozzle plate 53, a vibration absorber 54, a diaphragm 55, a plurality of piezoelectric elements 56, a sealing plate 57, a case 58, and a wiring substrate 59. Each of the plurality of piezoelectric elements 56 is an example of an "energy generating element".

[0018] In a region located in the Z1 direction with respect to the flow path substrate 51, the pressure chamber substrate 52, the diaphragm 55, the plurality of piezoelectric elements 56, the case 58, and the sealing plate 57 are installed. On the other hand, in a region located in the Z2 direction with respect to the flow path substrate 51, the nozzle plate 53 and the vibration absorber 54 are installed. Each element of the liquid ejection head 50 is a plate-like member that is generally long in the direction along the Y axis, and is joined to each other by, for example, an adhesive.

[0019] As shown in FIG. 2, the nozzle plate 53 is a plate-like member provided with a plurality of nozzles N arranged in the direction along the Y axis. Each nozzle N is a through hole for allowing ink to pass through. Thus, the nozzle plate 53 has a plurality of nozzles N for ejecting ink. The nozzle plate 53 is manufactured, for example, by processing a single crystal silicon substrate by a semiconductor manufacturing technique using a processing technique such as dry etching or wet etching. However, other known methods and materials may be appropriately used for manufacturing the nozzle plate 53.

[0020] The flow path substrate 51 is a plate-like member for forming an ink flow path. As shown in FIGS. 2 and 3, the flow path substrate 51 is provided with an opening R1, a plurality of supply flow paths Ra, and a plurality of communication flow paths Na. The opening R1 is an elongated through-hole that extends in the direction along the Y-axis in a plan view when viewed in the direction along the Z-axis so as to be continuous across the plurality of nozzles N. On the other hand, each of the supply flow path Ra and the communication flow path Na is a through-hole provided individually for each nozzle N. Each of the plurality of supply flow paths Ra communicates with the opening R1. The flow path substrate 51 is manufactured, for example, by processing a silicon single crystal substrate by semiconductor manufacturing technology, similarly to the nozzle plate 53 described above. However, other known methods and materials may be appropriately used for the manufacture of the flow path substrate 51.

[0021] The pressure chamber substrate 52 is a plate-like member provided with a plurality of pressure chambers C corresponding to the plurality of nozzles N. The pressure chamber C is a space located between the flow path substrate 51 and the diaphragm 55 and is called a cavity for applying pressure to the ink filled in the pressure chamber C. The pressure chamber C applies pressure to the ink by the vibration of the diaphragm 55. The plurality of pressure chambers C are arranged in the direction along the Y-axis. Each pressure chamber C is composed of holes 52a that open on both surfaces of the pressure chamber substrate 52 and has an elongated shape extending in the direction along the X-axis. Therefore, the longitudinal direction of the pressure chamber C is the direction along the X-axis, and the short side direction of the pressure chamber C is the direction along the Y-axis. Thus, the pressure chamber substrate 52 has a plurality of pressure chambers C communicating with the nozzles N. The end of each pressure chamber C in the X2 direction communicates with the corresponding supply flow path Ra. On the other hand, the end of each pressure chamber C in the X1 direction communicates with the corresponding communication flow path Na. The pressure chamber substrate 52 is manufactured, for example, by processing a silicon single crystal substrate by semiconductor manufacturing technology, similarly to the nozzle plate 53 described above. However, other known methods and materials may be appropriately used for the manufacture of each of the pressure chamber substrates 52.

[0022] The diaphragm 55 is disposed on the surface of the pressure chamber substrate 52 facing the Z1 direction. The diaphragm 55 is an elastically deformable plate-like member and vibrates by the drive of the piezoelectric element 56. The details of the diaphragm 55 will be described later with reference to FIG. 5.

[0023] On the surface of the diaphragm 55 facing the Z1 direction, a piezoelectric element 56 is disposed. The piezoelectric element 56 generates energy for applying pressure to the liquid in the pressure chamber C. More specifically, the piezoelectric element 56 is a passive element that deforms upon supply of a drive signal and has an elongated shape extending in a direction along the X-axis. Note that one piezoelectric element 56 is provided for each pressure chamber, and the plurality of piezoelectric elements 56 are arranged in a direction along the Y-axis so as to correspond to the plurality of pressure chambers C. When the diaphragm 55 vibrates in conjunction with the deformation of the piezoelectric element 56, the pressure in the pressure chamber C fluctuates. Thus, when the diaphragm 55 vibrates by the energy generated by the piezoelectric element 56, ink is ejected from the nozzle N. Details of the piezoelectric element 56 will be described later with reference to FIGS. 4 and 5.

[0024] The case 58 is a member for storing ink supplied to the plurality of pressure chambers C, and is joined to the surface of the flow path substrate 51 facing the Z1 direction by an adhesive or the like. The case 58 is made of, for example, a resin material and is manufactured by injection molding. The case 58 is provided with a housing portion R2 and an inlet IH. The housing portion R2 is a concave portion having an outer shape corresponding to the opening R1 of the flow path substrate 51. The inlet IH is a through hole communicating with the housing portion R2. The space formed by the opening R1 and the housing portion R2 functions as a liquid storage chamber R, which is a reservoir for storing ink. Ink from the liquid container 10 is supplied to the liquid storage chamber R through the inlet IH.

[0025] The vibration absorber 54 is a member for absorbing pressure fluctuations in the liquid storage chamber R. The vibration absorber 54 is, for example, a compliance substrate which is a flexible sheet member capable of elastic deformation. The vibration absorber 54 is disposed on the surface of the flow path substrate 51 facing the Z2 direction so as to block the opening R1 of the flow path substrate 51 and the plurality of supply channels Ra and form the bottom surface of the liquid storage chamber R.

[0026] The sealing plate 57 is a structure that protects the plurality of piezoelectric elements 56 and reinforces the mechanical strength of the pressure chamber substrate 52 and the diaphragm 55. The sealing plate 57 is joined to the surface of the diaphragm 55 by, for example, an adhesive. The sealing plate 57 is provided with recesses for accommodating the plurality of piezoelectric elements 56.

[0027] A wiring substrate 59 is joined to the surface of the pressure chamber substrate 52 or the diaphragm 55 facing the Z1 direction. The wiring substrate 59 is a mounting component on which a plurality of wirings for electrically connecting the control unit 20 and the liquid ejection head 50 are formed. The wiring substrate 59 is, for example, a flexible wiring substrate such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable). A drive circuit 60 for driving the piezoelectric elements 56 is mounted on the wiring substrate 59. The drive circuit 60 selectively supplies drive signals for driving the respective piezoelectric elements 56 to the respective piezoelectric elements 56 via the wiring substrate 59.

[0028] 1-3. Diaphragm and Piezoelectric Elements FIG. 4 is a plan view showing a part of the liquid ejection head 50 according to the embodiment. FIG. 5 is a cross-sectional view taken along line B-B in FIG. 4. Hereinafter, the diaphragm 55 and the piezoelectric elements 56 will be described in detail based on FIGS. 4 and 5. Prior to the description of the diaphragm 55 and the piezoelectric elements 56, first, the pressure chamber substrate 52 will be described.

[0029] As shown in FIGS. 4 and 5, the pressure chamber substrate 52 is provided with holes 52a that constitute the pressure chambers C. Accordingly, between two adjacent holes 52a in the pressure chamber substrate 52, a wall-like partition 52b extending in the direction along the X axis is provided. The pressure chamber substrate 52 is manufactured, for example, by processing a silicon single crystal substrate using semiconductor manufacturing technology. In FIG. 4, the planar shape of the holes 52a in the case of being formed by anisotropic etching on a silicon single crystal substrate with a plane orientation of (110) is indicated by a broken line. Note that the planar shape of the holes 52a is not limited to the example shown in FIG. 4 and is arbitrary.

[0030] The formation of the pressure chamber C is performed after the formation of the piezoelectric element 56. The formation of the pressure chamber C is carried out, for example, by anisotropically etching a surface of the silicon single crystal substrate different from the surface on which the piezoelectric element 56 is formed among both surfaces of the silicon single crystal substrate after the formation of the piezoelectric element 56. At this time, as the etching solution for the anisotropic etching, for example, an aqueous potassium hydroxide solution (KOH) or the like is used. Further, at this time, when the first layer 55a is made of silicon oxide, the first layer 55a functions as a stop layer for stopping the anisotropic etching. After the formation of the pressure chamber C as described above, the flow path substrate 51 or the like is bonded to the pressure chamber substrate 52 with an adhesive. Note that after the formation of the piezoelectric element 56, if necessary, the surface of the silicon single crystal substrate opposite to the surface on which the piezoelectric element 56 is formed among both surfaces is ground by CMP (chemical mechanical polishing) or the like, and planarization of the surface or thickness adjustment of the substrate is performed.

[0031] As shown in FIG. 4, in a plan view, the piezoelectric element 56 overlaps the pressure chamber C. As shown in FIG. 5, the piezoelectric element 56 includes a lower electrode 56a, a piezoelectric body 56b, and an upper electrode 56c, and these are laminated in the Z1 direction in this order. In this way, the upper electrode 56c is provided above the piezoelectric body 56b, while the lower electrode 56a is provided below the piezoelectric body 56b. Note that the piezoelectric element 56 may be configured such that electrode and piezoelectric body layers are alternately laminated in multiple layers between the lower electrode 56a and the upper electrode 56c and expand and contract toward the diaphragm 55. Further, other layers such as a layer for enhancing adhesion may be appropriately interposed between the layers of the piezoelectric element 56 or between the piezoelectric element 56 and the diaphragm 55.

[0032] The lower electrode 56a is an individual electrode that is arranged separately from each other for each piezoelectric element 56. Specifically, a plurality of lower electrodes 56a extending in the direction along the X axis are arranged at intervals in the direction along the Y axis. A drive signal including a predetermined voltage pulse is supplied from the control unit 20 to the lower electrode 56a of each piezoelectric element 56.

[0033] The lower electrode 56a has, for example, a layer made of iridium (Ir) and a layer made of titanium (Ti), and these are laminated in this order in the Z1 direction. Iridium is an electrode material with excellent conductivity. Therefore, by using iridium as the constituent material of the lower electrode 56a, the lower electrode 56a can be made to have a lower resistance. In addition, when forming the piezoelectric body 56b, the layer made of titanium causes island-shaped Ti to serve as crystal nuclei to control the orientation of the piezoelectric body 56b, thereby enhancing the crystallinity or orientation of the piezoelectric body 56b. Note that instead of, or in addition to, the layer made of iridium, a layer made of another metal material may be provided.

[0034] In the examples shown in FIGS. 4 and 5, the piezoelectric body 56b has a strip shape extending in the direction along the Y axis so as to be continuous across a plurality of piezoelectric elements 56. In the example shown in FIG. 4, in the piezoelectric body 56b, through holes 56b1 penetrating the piezoelectric body 56b are provided so as to extend in the direction along the X axis in regions corresponding in plan view to the gaps between the pressure chambers C adjacent to each other. Thereby, as seen in the cross section shown in FIG. 5, the piezoelectric body 56b is provided individually for each piezoelectric element 56. Note that the piezoelectric body 56b may be provided individually for a plurality of piezoelectric elements 56.

[0035] The piezoelectric body 56b is made of a second piezoelectric material having piezoelectricity. The second piezoelectric material is a piezoelectric material having a perovskite crystal structure represented by the general composition formula ABO3. Specifically, the material constituting the piezoelectric body 56b is, for example, a piezoelectric material containing one or more elements selected from lead (Pb), titanium (Ti), zirconium (Zr), potassium (K), sodium (Na), niobium (Nb), barium (Ba), iron (Fe), bismuth (Bi), tantalum (Ta), chromium (Cr), iridium (Ir), hafnium (Hf), lithium (Li), carbon (C), and lanthanum (La). The piezoelectric material is not particularly limited, and examples thereof include barium titanate (BaTiO3), lead zirconate titanate (Pb(Zr,Ti)O3), potassium sodium niobate ((K,Na)NbO3), and the like.

[0036] The upper electrode 56c is a strip-shaped common electrode that extends in the direction along the Y-axis so as to be continuous across a plurality of piezoelectric elements 56. A predetermined constant potential is supplied to the upper electrode 56c.

[0037] The upper electrode 56c is made of, for example, iridium (Ir). Note that the constituent material of the upper electrode 56c is not limited to iridium, and may be, for example, a metal material such as titanium (Ti), platinum (Pt), aluminum (Al), nickel (Ni), gold (Au), or copper (Cu). Further, for the upper electrode 56c, one of these metal materials may be used alone, or two or more of them may be used in combination in a form such as lamination.

[0038] In the above piezoelectric element 56, when a voltage is applied between the lower electrode 56a and the upper electrode 56c, the piezoelectric body 56b deforms due to the inverse piezoelectric effect. A diaphragm 55 is joined to the piezoelectric element 56, and the diaphragm 55 vibrates as the piezoelectric body 56b deforms.

[0039] As shown in FIG. 5, the diaphragm 55 has a first layer 55a and a second layer 55b in this order along the Z1 direction, which is the direction from the pressure chamber substrate 52 toward the piezoelectric element 56.

[0040] The first layer 55a is an insulating film made of, for example, silicon oxide (SiO2). The second layer 55b is an elastic film made of, for example, zirconium oxide (ZrO2). Note that the material constituting the first layer 55a is not limited to SiO2, and may be, for example, a single substance of silicon (Si), a nitride, or an oxynitride. The material constituting the second layer 55b is not limited to ZrO2, and may be, for example, a single substance of zirconium (Zr), a nitride, or an oxynitride, or may be a material containing, as constituent elements, one or more elements selected from titanium (Ti), aluminum (Al), tantalum (Ta), chromium (Cr), and hafnium (Hf) in any state of a single substance, an oxide, a nitride, or an oxynitride. Further, the configuration of the diaphragm 55 is not limited to the illustrated configuration. For example, a layer such as an adhesion layer may be interposed between the first layer 55a and the second layer 55b.

[0041] A recess 70 is provided on the bottom surface of the diaphragm 55 described above. The bottom surface of the diaphragm 55 is the plate surface closer to the pressure chamber substrate 52 among the pair of plate surfaces of the diaphragm 55. In the example shown in FIG. 5, the bottom surface of the diaphragm 55 is the surface facing the Z2 direction of the diaphragm 55. The recess 70 has a shape extending along the pressure chamber C in plan view. The width W1, which is the length of the recess 70 in the direction along the Y axis, is larger than the width W0, which is the length of the hole 52a in the direction along the Y axis. Although not shown, the length of the recess 70 in the direction along the X axis is larger than the length of the hole 52a in the direction along the X axis. Note that the length of the recess 70 in the direction along the X axis may be equal to the length of the hole 52a in the direction along the X axis.

[0042] The diaphragm 55 described above has a vibration region PV that vibrates by driving the piezoelectric element 56. The vibration region PV is a part of the diaphragm 55 and is a portion that overlaps the pressure chamber C in plan view.

[0043] The vibration region PV is divided into a first region RE1 and a second region RE2. The first region RE1 is a region that overlaps the piezoelectric body 56b in plan view. The second region RE2 is a region that does not overlap the piezoelectric body 56b in plan view. By having the second region RE2 in the vibration region PV, the deformation efficiency of the vibration region PV by the piezoelectric element 56 can be increased as compared with a mode in which the vibration region PV is composed of only the first region RE1.

[0044] A protective film 80 for protecting the wall surface from ink is disposed on the wall surface of the pressure chamber C. The protective film 80 is a film having higher resistance to the ink in the pressure chamber C than the diaphragm 36. As the constituent material of the protective film 80, any material having resistance to the ink in the pressure chamber C may be used and is not particularly limited. For example, silicon oxides such as silicon oxide (SiO2), nickel oxide (NiO X ), metal oxides such as tantalum oxide (TaO X ) and zirconium oxide (ZrO2), and metals such as nickel (Ni) and chromium (Cr) can be mentioned. The protective film 80 may be composed of a single layer of a single material or a laminate of a plurality of layers of different materials.

[0045] As described above, the liquid ejection head 50 includes a piezoelectric element 56 which is an example of an "energy generating element", a diaphragm 55, a pressure chamber substrate 52, and a protective film 80. Here, the thickness of the protective film 80 varies depending on the position. Hereinafter, the recess 70 and the protective film 80 will be described in detail with reference to FIG. 6.

[0046] FIG. 6 is an enlarged cross-sectional view for explaining the recess 70 of the diaphragm 55 and the protective film 80. As shown in FIG. 6, the recess 70 includes a bottom portion 71 and a curved portion 72. Therefore, the bottom portion 71 and the curved portion 72 are provided on the bottom surface of the diaphragm 55. The bottom portion 71 is the bottom surface of the recess 70 and is a portion having a shape in a plane orthogonal to the Z axis. The curved portion 72 is a portion having a shape of a curved surface adjacent to the bottom portion 71 in the short side direction of the pressure chamber C. The curved portion 72 is a concave curved surface extending from both ends of the bottom portion 71 in the direction along the Y axis to both ends of the recess 70 in the Y axis direction. Therefore, the curved portion 72 is curved in a concave shape when viewed in a cross section orthogonal to the X axis.

[0047] The length of the curved portion 72 in the direction along the Z axis is equal to the depth d of the recess 70. Also, the width W which is the length of the curved portion 72 in the direction along the Y axis is approximately equal to 1 / 2 of the difference between the width W1 of the recess 70 and the width W0 of the hole 52a. The magnitude relationship between the width W and the depth d is not particularly limited, but it is preferably in the relationship where W / d is 0.5 or more and 1.5 or less, and more preferably in the relationship where W / d is 0.8 or more and 1.2 or less.

[0048] Thus, since the curved portion 72 is provided on the bottom surface of the diaphragm 55, the displacement characteristics of the diaphragm 55 can be improved as compared with the aspect in which the curved portion 72 is omitted.

[0049] The pressure chamber substrate 52 has a surface F1 facing in the Z1 direction and a wall surface F2 continuous with the surface F1. The surface F1 is the surface joined to the diaphragm 55. The wall surface F2 is the surface including the wall surface of the hole 52a and is in contact with the bottom surface of the diaphragm 55. The wall surface F2 has a surface F2a and a surface F2b. The surface F2a extends along the Z axis when viewed in the direction along the X axis. The surface F2b is the surface spanning between the surface F1 and the surface F2a. In the example shown in FIG. 6, the surface F2b is inclined with respect to the surface F1 when viewed in the direction along the X axis. Thus, the inner wall surface of the pressure chamber C includes the wall surface of the recess 70 and the wall surface F2. Also, when viewed in the direction along the Z axis, the boundary between the bottom portion 71 and the curved portion 72 substantially coincides with the position of the surface F2a. Note that the surface F2b may not be inclined with respect to the surface F1 when viewed in the direction along the X axis. That is, the surface F2b may be located on the same plane as the surface F1. In this case, the wall surface of the hole 52a is constituted by the surface F2a.

[0050] As described above, the pressure chamber substrate 52 has a wall surface F2 in contact with a part of the bottom surface of the diaphragm 55 and partitions the pressure chamber C.

[0051] The protective film 80 is provided so as to cover the bottom surface of the diaphragm 55 and the wall surface F2 of the pressure chamber substrate 52. The protective film 80 is a film having higher resistance to the ink in the pressure chamber C than the diaphragm 36 and is provided over the wall surface of the recess 70 and the wall surface F2.

[0052] The thickness of the protective film 80 at the first position P1 which is the center of the bottom portion 71 in the short side direction of the pressure chamber C is the first thickness t1. The thickness of the protective film 80 at the second position P2 where the curved portion 72 is disposed is the second thickness t2 which is thinner than the first thickness t1.

[0053] Thus, since the thickness of the protective film 80 in the curved portion 72 is the second thickness t2 which is thinner than the first thickness t1, it is possible to suitably exhibit the effect of improving the displacement characteristics of the diaphragm 55 by the curved portion 72 while suppressing damage to the bottom surface of the diaphragm 55 and the wall surface F2 of the pressure chamber substrate 52.

[0054] The specific first thickness t1 is not particularly limited. For example, it is within the range of 20 nm or more and 150 nm or less, preferably within the range of 25 nm or more and 100 nm or less. When the first thickness t1 is within such a range, there is an advantage that it is easy to realize a suitable magnitude relationship between the first thickness t1 and the second thickness t2.

[0055] The second thickness t2 is preferably 3% or more and 10% or less of the first thickness t1. That is, t2 / t1 is preferably 0.03 or more and 0.10 or less. When the first thickness t1 and the second thickness t2 are in such a relationship, both the effect of improving the displacement characteristics of the diaphragm 55 by the curved portion 72 and the effect of suppressing damage to the bottom surface of the diaphragm 55 and the wall surface F2 of the pressure chamber substrate 52 by the protective film 80 are preferably achieved.

[0056] The second thickness t2 is smaller than the length of the curved portion 72 in the short direction of the pressure chamber C. Thereby, it is possible to prevent the curved portion 72 from being completely filled by the protective film 80. As a result, the effect of improving the displacement characteristics of the diaphragm 55 by the curved portion 72 can be preferably exhibited.

[0057] The specific second thickness t2 is not particularly limited. For example, it is within the range of 0.5 nm or more and 15 nm or less, preferably within the range of 1 nm or more and 12 nm or less. When the second thickness t2 is within such a range, there is an advantage that it is easy to realize a suitable magnitude relationship between the first thickness t1 and the second thickness t2.

[0058] The thickness of the protective film 80 at the third position P3 closer to the end than the first position P1 of the bottom portion 71 in the short direction of the pressure chamber C is the third thickness t3 between the first thickness t1 and the second thickness t2. When the first thickness t1, the second thickness t2, and the third thickness t3 are in such a relationship, a sudden change in the thickness of the protective film 80 can be reduced. As a result, the durability of the protective film 80 can be enhanced.

[0059] The third thickness t3 is preferably 75% or more and 90% or less of the first thickness t1. That is, t3 / t2 is preferably 0.75 or more and 0.90 or less. When the first thickness t1 and the third thickness t3 are in such a relationship, it is possible to make the second thickness t2 a suitable thickness while reducing a sharp change in the thickness of the protective film 80.

[0060] The specific third thickness t3 is not particularly limited. For example, it is in the range of 15 nm or more and 100 nm or less, and preferably in the range of 20 nm or more and 90 nm or less. When the third thickness t3 is within such a range, there is an advantage that it is easy to realize a suitable size relationship among the first thickness t1, the second thickness t2, and the third thickness t3.

[0061] The first position P1 is a position where all of the piezoelectric body 56b, the upper electrode 56c, and the lower electrode 56a overlap when viewed from the Z1 direction which is the height direction. On the other hand, the third position P3 is a position where at least a part of the piezoelectric body 56b, the upper electrode 56c, and the lower electrode 56a do not overlap when viewed from the Z1 direction which is the height direction. That is, the third position P3 is located in the second region RE2 without being located in the first region RE1 when viewed in the direction along the Z axis. When the first position P1 and the third position P3 are in such positions, the effect of improving the displacement characteristics of the diaphragm 55 by the curved portion 72 can be preferably exerted.

[0062] The thickness of the protective film 80 on the wall surface F2 is a fourth thickness t4 which is thinner than the first thickness t1. Thereby, it becomes easy to make the second thickness t2 thinner than the first thickness t1.

[0063] The specific fourth thickness t4 is not particularly limited. For example, it is in the range of 3 nm or more and 30 nm or less, and preferably in the range of 5 nm or more and 25 nm or less. When the fourth thickness t4 is within such a range, there is an advantage that it is easy to realize a suitable size relationship between the first thickness t1 and the second thickness t2.

[0064] 1-4. Method for manufacturing a liquid ejection head FIG. 7 is a diagram for explaining a method of manufacturing the liquid ejection head 50 according to the embodiment. As shown in FIG. 7, the method of manufacturing the liquid ejection head 50 includes, in this order, a step ST1 of forming the diaphragm 55 and the piezoelectric element 56, a step ST2 of forming the holes 52a and the recess 70, and a step ST3 of forming the protective film 80.

[0065] In the step ST1 shown in the upper part of FIG. 7, after forming the diaphragm 55, the piezoelectric element 56 is formed. The diaphragm 55 is formed by forming the first layer 55a and the second layer 55b in this order on a substrate 520 such as a silicon single crystal substrate for forming the pressure chamber substrate 52.

[0066] For example, when the substrate 520 is a silicon single crystal substrate, the first layer 55a is formed by thermally oxidizing the substrate 520. Note that the method of forming the first layer 55a is not limited to the method by thermal oxidation, and for example, a method such as a CVD method or an atomic layer deposition (ALD) method may be used.

[0067] For example, when the second layer 55b is made of zirconium oxide, the second layer 55b is formed by forming a zirconium layer by a film forming method such as a sputtering method on the first layer 55a and then thermally oxidizing the layer. Note that the method of forming the second layer 55b is not limited to the method by thermal oxidation, and for example, a method such as a CVD method or an atomic layer deposition (ALD) method may be used.

[0068] The piezoelectric element 56 is formed by forming the lower electrode 56a, the piezoelectric body 56b, and the upper electrode 56c in this order.

[0069] The lower electrode 56a is formed by known film formation techniques such as sputtering and known processing techniques using photolithography and etching. The piezoelectric body 56b is formed, for example, by forming a precursor layer of the piezoelectric body by the sol-gel method and then firing and crystallizing the precursor layer. The upper electrode 56c is formed in the same manner as the lower electrode 56a, for example, by known film formation techniques such as sputtering and known processing techniques using photolithography and etching.

[0070] In the process ST2 shown by the interruption in FIG. 7, the substrate 520 is etched to form the hole 52a and the recess 70. Thereby, the pressure chamber substrate 52 is obtained.

[0071] Specifically, for example, in the process ST2, after forming a mask on the surface of the substrate 520 opposite to the surface in contact with the diaphragm 55 among the both surfaces of the substrate 520, anisotropic etching is performed through the mask, and then the mask is removed with a removing solution.

[0072] The mask is made of, for example, silicon nitride (SiN) and is formed by known film formation techniques such as sputtering and known processing techniques using photolithography and etching. As the etching solution for the anisotropic etching, for example, an aqueous potassium hydroxide solution (KOH) or the like is used. By the anisotropic etching, the hole 52a is formed, and at this time, a part of the recess 70 is formed by over-etching. For removing the mask, for example, when the mask is made of silicon nitride, hydrofluoric acid (HF) is used as the removing solution. When removing the mask, the first layer 55a of the diaphragm 55 is isotropically etched with the removing solution. Thereby, the recess 70 is obtained.

[0073] In the process ST3 shown at the lower stage in FIG. 7, a protective film 80 is formed by a vapor phase film formation method such as CVD (chemical vapor deposition).

[0074] Here, when forming the protective film by CVD, it is usually carried out in an extremely low-pressure environment around 0.1 Pa. In this embodiment, the protective film 80 is formed by CVD or the like under a pressure relatively close to atmospheric pressure, specifically, a pressure of 1 Pa or more and 100,000 Pa or less, more preferably 1 Pa or more and 100 Pa or less. In this case, since the straightness in the film formation direction increases, it is considered that film formation becomes difficult in the curved portion 72 of the concave portion 70. Thereby, the relationship between the aforementioned first thickness t1 and the second thickness t2 can be realized.

[0075] 2. Modification Each form in the above examples can be variously modified. Specific modification modes applicable to each of the above forms are exemplified below. Note that two or more modes arbitrarily selected from the following examples can be appropriately combined within a range that does not conflict with each other.

[0076] 2-1. Modification 1 In the above-described embodiment, an aspect is exemplified in which the lower electrode 56a is an individual electrode and the upper electrode 56c is a common electrode. However, the present invention is not limited to this aspect, and the lower electrode 56a may be a common electrode and the upper electrode 56c may be an individual electrode.

[0077] 2-2. Modification 2 In the above-described embodiment, the piezoelectric body 56b is provided in common for a plurality of pressure chambers C. However, the present invention is not limited to this, and the piezoelectric body 56b may be divided for each pressure chamber C. Also, both the lower electrode 56a and the upper electrode 56c may be individual electrodes.

[0078] 2-3. Modification 3 In the above-described embodiment, an aspect is exemplified in which the piezoelectric element 56 is an energy generating element. However, the present invention is not limited to this aspect. For example, the energy generating element may be a heating element that varies the pressure of the ink by generating bubbles inside the pressure chamber C by heating.

[0079] 2-4. Modification 4 In the foregoing embodiment, a serial liquid ejecting apparatus 100 that reciprocates a carriage 41 mounting a liquid ejecting head 50 is illustrated. However, the present disclosure can also be applied to a line type liquid ejecting apparatus in which a plurality of nozzles N are distributed over the entire width of a medium M.

[0080] 2-5. Modification Example 5 The liquid ejecting apparatus 100 illustrated in the foregoing embodiment can be adopted in various apparatuses such as a facsimile apparatus and a copying machine in addition to a device dedicated to printing. However, the use of the liquid ejecting apparatus of the present disclosure is not limited to printing. For example, a liquid ejecting apparatus that ejects a solution of a coloring material is used as a manufacturing apparatus for forming a color filter of a liquid crystal display device. In addition, a liquid ejecting apparatus that ejects a solution of a conductive material is used as a manufacturing apparatus for forming wirings and electrodes of a wiring board.

Examples

[0081] Hereinafter, specific examples of the present invention will be described. Note that the present invention is not limited to the following examples.

[0082] A. Manufacture of Liquid Ejecting Head A-1. Example 1 A liquid ejecting head as shown in FIG. 5 was manufactured. Here, a protective film was formed by CVD. As shown in FIG. 8, the first thickness t1 of the protective film was 25.0 nm, the second thickness t2 of the protective film was 2.5 nm, the third thickness t3 of the protective film was 22.0 nm, and the fourth thickness t4 of the protective film was 7.0 nm.

[0083] A-2. Examples 2-13 A liquid ejecting head was manufactured in the same manner as in Example 1 except that the film thickness of the protective film was different as shown in FIG. 5. Here, the film thickness of the protective film was changed by changing the pressure when forming the protective film.

[0084] B. Evaluation of Liquid Ejecting Head The characteristics of the liquid ejecting heads of Examples 1-13 were evaluated according to the following criteria. The results of this evaluation are also shown in FIG. 5.

[0085] Reference A: The function of the protective film is preferably exerted, and the displacement characteristics of the diaphragm are excellent. B: Although inferior to A, the compatibility between the function of the protective film and the displacement characteristics of the diaphragm is achieved.

[0086] As described above, in Examples 1-13, it is possible to improve the displacement characteristics of the diaphragm while suppressing damage to the bottom surface of the diaphragm and the wall surface of the pressure chamber substrate. In particular, in Examples 1-5, the compatibility between the function of the protective film and the displacement characteristics of the diaphragm is preferably achieved.

Explanation of Reference Numerals

[0087] 10… Liquid container, 20… Control unit, 30… Conveying mechanism, 36… Diaphragm, 40… Moving mechanism, 41… Carriage, 42… Conveyor belt, 50… Liquid ejection head, 51… Flow path substrate, 52… Pressure chamber substrate, 52a… Hole, 52b… Partition wall, 53… Nozzle plate, 54… Vibration absorber, 55… Diaphragm, 55a… First layer, 55b… Second layer, 56… Piezoelectric element, 56a… Lower electrode, 56b… Piezoelectric body, 56b1… Through hole, 56c… Upper electrode, 57… Sealing plate, 58… Case, 59… Wiring substrate, 60… Drive circuit, 70… Recess, 71… Bottom, 72… Curved portion, 80… Protective film, 100… Liquid ejection device, 520… Substrate, C… Pressure chamber, F1… Surface, F2… Wall surface, F2a… Surface, F2b… Surface, IH… Inlet, M… Medium, N… Nozzle, Na… Communication flow path, P1… First position, P2… Second position, P3… Third position, PV… Vibration region, R… Liquid storage chamber, R1… Opening, R2… Accommodation portion, RE1… First region, RE2… Second region, Ra… Supply flow path, ST1… Process, ST2… Process, ST3… Process, W… Width, W0… Width, W1… Width, d… Depth, f2b… Surface, t1… First thickness, t2… Second thickness, t3… Third thickness, t4… Fourth thickness.

Claims

1. An energy generating element that generates energy for applying pressure to a liquid in a pressure chamber, a diaphragm that vibrates by the energy, a pressure chamber substrate that has a wall surface in contact with a part of the bottom surface of the diaphragm and partitions the pressure chamber, and a protective film provided so as to cover the bottom surface of the diaphragm and the wall surface of the pressure chamber substrate, wherein a liquid discharge head, on the bottom surface of the diaphragm, a bottom portion having a planar shape, a curved portion that is adjacent to the bottom portion in the short direction of the pressure chamber and has a curved shape, are provided, the thickness of the protective film at a first position that is the center of the bottom portion in the short direction of the pressure chamber is a first thickness, the thickness of the protective film at a second position where the curved portion is disposed is a second thickness that is thinner than the first thickness, A liquid discharge head characterized by the above.

2. The second thickness is 3% or more and 10% or less of the first thickness, The liquid discharge head according to claim 1, characterized by the above.

3. The thickness of the protective film at a third position closer to the end than the first position of the bottom portion in the short direction of the pressure chamber is a third thickness between the first thickness and the second thickness, The liquid discharge head according to claim 1, characterized by the above.

4. The third thickness is 75% or more and 90% or less of the first thickness, The liquid discharge head according to claim 3, characterized by the above.

5. The energy generating element, a piezoelectric body, an upper electrode provided on the upper portion of the piezoelectric body, a lower electrode provided on the lower portion of the piezoelectric body, and has, the first position is a position where all of the piezoelectric body, the upper electrode, and the lower electrode overlap when viewed from the height direction, the third position is a position where at least a part of the piezoelectric body, the upper electrode, and the lower electrode do not overlap when viewed from the height direction, The liquid discharge head according to claim 3, characterized by the above.

6. The thickness of the protective film on the wall surface is a fourth thickness that is thinner than the first thickness, The liquid discharge head according to claim 1, characterized by the above.

7. The second thickness is smaller than the length of the curved portion in the short direction of the pressure chamber, The liquid discharge head according to claim 1, characterized by the above.

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