Liquid ejection head

Abstract

To prevent the liquid level of a nozzle from breaking. [Solution] The device comprises a flow path substrate having a flow path, a nozzle substrate having a nozzle penetrating between a first surface and a second surface connecting the flow path to the outside and having a second surface joined to the flow path substrate, and an energy generating element that generates energy for ejecting liquid from the nozzle, wherein when the direction in which the flow path substrate and the nozzle substrate are stacked is defined as the first direction and the direction perpendicular to the first direction is defined as the second direction, the nozzle is composed of a first nozzle portion that penetrates from the first surface to a connection position within the nozzle substrate, and a second nozzle portion that is a hole that penetrates from the connection position to the second surface, the width of the first nozzle portion is constant in the second direction regardless of its position in the first direction, and the width of the second nozzle portion gradually increases in the second direction such that the amount of increase in width in the second direction decreases as its position in the first direction approaches the second surface.

Description

[Technical Field]

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

[0002] Conventionally, liquid ejection heads that eject liquid such as ink from nozzles provided in a nozzle substrate have been disclosed. For example, Patent Document 1 discloses a nozzle having a first nozzle section and a second nozzle section arranged side by side in the plate thickness direction of the nozzle substrate. The first nozzle section is provided in the liquid ejection direction relative to the second nozzle section, and is provided in the plate thickness direction with the same shape as an opening provided on the surface of the nozzle substrate in the ejection direction. The inner surface of the second nozzle section has a surface that is linearly inclined with respect to the plate thickness direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-011032 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional nozzles described above, the liquid level in the nozzle may break, causing air bubbles to get inside the nozzle. [Means for solving the problem]

[0005] A liquid ejection head according to a preferred aspect of the present disclosure includes a flow path substrate having a flow path, a nozzle substrate having a first surface and a second surface bonded to the flow path substrate and a nozzle communicating the flow path with the outside so as to penetrate between the first surface and the second surface, and an energy generating element that generates energy for ejecting liquid from the nozzle, wherein when the direction in which the flow path substrate and the nozzle substrate are stacked is defined as a first direction and a direction perpendicular to the first direction is defined as a second direction, the nozzle is composed of a first nozzle portion that penetrates from the first surface to a connection position in the nozzle substrate, and a second nozzle portion that is a hole that penetrates from the connection position to the second surface, wherein the width of the first nozzle portion is constant in the second direction regardless of its position in the first direction, and the width of the second nozzle portion in the second direction gradually increases as its position in the first direction approaches the second surface, with the amount of increase in width in the second direction decreasing. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a liquid ejection device 100 according to the present embodiment. [Figure 2] FIG. 2 is an exploded perspective view of the liquid ejection head 1. [Figure 3] 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is a plan view of the liquid ejection head 1 as viewed in the +Z direction. [Figure 5] FIG. 2 is an enlarged cross-sectional view of the vicinity of the piezoelectric element PZq. [Figure 6] FIG. 3 is a diagram for explaining a drive signal Com. [Figure 7] 10A and 10B are diagrams for explaining the phenomenon of air bubbles being mixed in the nozzle NA. [Figure 8] 4A and 4B are diagrams for explaining the state of forces acting on ink in a nozzle NA. [Figure 9] 4A and 4B are diagrams for explaining the state of force acting on ink in a nozzle NB. [Figure 10] 10A and 10B are diagrams for explaining why the pressure transmitted toward the first nozzle portion NP1 becomes excessive. [Figure 11]10A and 10B are diagrams for explaining why the pressure transmitted toward the first nozzle portion NP1 becomes excessive. [Figure 12] View of nozzle N in the +Z direction. [Figure 13] 13 is a cross-sectional view taken along line XIII-XIII in FIG. 12. [Figure 14] 14 is a cross-sectional view taken along line XIV-XIV in FIG. 12. [Figure 15] FIG. 10 is a diagram for explaining a nozzle NC in a second embodiment. [Figure 16] FIG. 10 is a diagram for explaining a nozzle ND in a first modified example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. However, in each drawing, the dimensions and scale of each part are appropriately different from those of the actual parts. Furthermore, since the embodiments described below are preferred specific examples of the present disclosure, various technically preferable limitations are applied, but 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] A. Embodiment A liquid ejection device 100 according to this embodiment will be described below with reference to FIG.

[0009] A1. Overview of the liquid ejection device 100 1 is an explanatory diagram showing an example of a liquid ejection device 100 according to this embodiment. The liquid ejection device 100 according to this embodiment is an inkjet printing device that ejects ink onto a medium PP. The medium PP is, for example, printing paper, but any printing target such as a resin film or fabric can also be used as the medium PP.

[0010] 1, the liquid ejection device 100 includes a liquid container 93 that stores ink. The liquid container 93 may be, for example, a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack made of flexible film, or an ink tank that can be refilled with ink. The liquid container 93 stores a plurality of types of ink with different colors.

[0011] 1, the liquid ejection device 100 includes a control device 90, a movement mechanism 91, a transport mechanism 92, and a circulation mechanism 94. Of these, the control device 90 includes a processing circuit such as a CPU or FPGA, and a storage circuit such as a semiconductor memory, and controls each element of the liquid ejection device 100. Here, CPU is an abbreviation for Central Processing Unit, and FPGA is an abbreviation for Field Programmable Gate Array. Furthermore, the movement mechanism 91 transports the medium PP in the +Y direction under the control of the control device 90. Note that, hereinafter, the +Y direction and the -Y direction opposite to the +Y direction will be collectively referred to as the Y-axis direction.

[0012] Further, under the control of the control device 90, the transport mechanism 92 reciprocates the multiple liquid ejection heads 1 in the +X direction and the -X direction, which is the direction opposite to the +X direction. Note that, hereinafter, the +X direction and the -X direction are collectively referred to as the X-axis direction. Here, the +X direction is a direction that intersects with the +Y direction. For example, the +X direction is a direction perpendicular to the +Y direction. The transport mechanism 92 includes a storage case 921 that stores the multiple liquid ejection heads 1, and an endless belt 922 to which the storage case 921 is fixed. Note that the liquid container 93 and the circulation mechanism 94 may be stored in the storage case 921 together with the liquid ejection heads 1.

[0013] Moreover, under the control of the control device 90, the circulation mechanism 94 supplies ink stored in the liquid container 93 to a supply flow path RB1 provided in the liquid ejection head 1. Furthermore, under the control of the control device 90, the circulation mechanism 94 recovers ink stored in a discharge flow path RB2 provided in the liquid ejection head 1, and returns the recovered ink to the supply flow path RB1. The supply flow path RB1 and the discharge flow path RB2 will be described later with reference to FIG.

[0014] As illustrated in FIG. 1 , a control device 90 supplies the liquid ejection head 1 with a drive signal Com for driving the liquid ejection head 1 and a control signal SI for controlling the liquid ejection head 1. The liquid ejection head 1 is driven by the drive signal Com under the control of the control signal SI, causing some or all of the M nozzles N of the liquid ejection head 1 to eject ink in the +Z direction. Here, the value M is an integer greater than or equal to 1. The +Z direction is a direction that intersects the +X and +Y directions. For example, the +Z direction is a direction perpendicular to the +X and +Y directions. Hereinafter, the +Z direction and the −Z direction, which is the direction opposite the +Z direction, may be collectively referred to as the Z-axis direction. To facilitate intuitive understanding of the description, the +Z direction may be referred to as the “downward direction” and the −Z direction may be referred to as the “upward direction.” Furthermore, the downward portion of a certain element may be referred to as the “lower portion,” and the upward portion of a certain element may be referred to as the “upper portion.” The nozzle N will be described later with reference to FIGS.

[0015] The liquid ejection head 1 ejects ink from some or all of the M nozzles N in conjunction with the transport of the medium PP by the moving mechanism 91 and the reciprocating movement of the liquid ejection head 1 by the transport mechanism 92, and causes the ejected ink to land on the surface of the medium PP, thereby forming a desired image on the surface of the medium PP.

[0016] A2. Overview of Liquid Ejection Head 1 An overview of the liquid ejection head 1 will be described below with reference to Figures 2 to 5. Figure 2 is an exploded perspective view of the liquid ejection head 1, Figure 3 is a cross-sectional view taken along line III-III in Figure 2, and Figure 4 is a plan view of the liquid ejection head 1 as viewed in the +Z direction.

[0017] As illustrated in Figures 2 and 3, the liquid ejection head 1 includes a nozzle substrate 60, compliance sheets 61 and 62, a communication plate 2, a pressure chamber substrate 3, a vibration plate 4, a storage chamber forming substrate 5, and a wiring substrate 8.

[0018] As illustrated in FIG. 2 , the nozzle substrate 60 is a plate-like member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and M nozzles N are formed on the nozzle substrate 60. Here, the term "substantially parallel" is a concept that includes not only completely parallel but also parallel alignment with allowance for error. The nozzle substrate 60 is manufactured by processing a silicon monocrystalline substrate using semiconductor manufacturing techniques such as etching. However, any known material and manufacturing method may be used to manufacture the nozzle substrate 60. The nozzles N are through-holes formed in the nozzle substrate 60. In this embodiment, as an example, it is assumed that M nozzles N are arranged in the nozzle substrate 60 to form a nozzle row Ln extending in the Y-axis direction.

[0019] The nozzle substrate 60 has a surface FN1 facing the +Z direction and a surface FN2 facing the -Z direction. The surface FN2 is bonded to the pressure chamber substrate 3. The surface FN2 is closer to the pressure chamber substrate 3 than the surface FN1. The surface FN1 is an example of a "first surface." The surface FN2 is an example of a "second surface."

[0020] 2 and 3, a communication plate 2 is provided in the −Z direction of the nozzle substrate 60. The communication plate 2 is a plate-shaped member that is long in the Y-axis direction and extends substantially parallel to the XY plane, and forms an ink flow path.

[0021] Specifically, one supply flow path RA1 and one discharge flow path RA2 are formed in the communication plate 2. Of these, the supply flow path RA1 communicates with a supply flow path RB1 (described later) and is provided to extend in the Y-axis direction. Furthermore, the discharge flow path RA2 communicates with a discharge flow path RB2 (described later) and is provided to extend in the Y-axis direction in the -X direction as viewed from the supply flow path RA1.

[0022] The communication plate 2 is also formed with M nozzle flow paths RN corresponding to the M nozzles N in a one-to-one relationship, M communication flow paths RR1 corresponding to the M nozzles N in a one-to-one relationship, M communication flow paths RR2 corresponding to the M nozzles N in a one-to-one relationship, M communication flow paths RK1 corresponding to the M nozzles N in a one-to-one relationship, M communication flow paths RK2 corresponding to the M nozzles N in a one-to-one relationship, one communication flow path RX1 common to the M nozzles N, and one communication flow path RX2 common to the M nozzles N. The communication plate 2 may also be provided with M communication flow paths RX1 corresponding to the M nozzles N in a one-to-one relationship, and M communication flow paths RX2 corresponding to the M nozzles N in a one-to-one relationship.

[0023] Of these, communicating flow passage RX1 communicates with supply flow passage RA1 and is provided so as to extend in the X-axis direction in the -X direction as viewed from supply flow passage RA1. Also, communicating flow passage RK1 communicates with communicating flow passage RX1 at an end in the -X direction and is provided so as to extend in the Z-axis direction. Also, communicating flow passage RR1 is provided so as to extend in the Z-axis direction in the -X direction as viewed from communicating flow passage RK1.

[0024] Furthermore, the communication flow path RX2 communicates with the discharge flow path RA2 and is provided so as to extend in the X-axis direction in the +X direction as viewed from the discharge flow path RA2. The communication flow path RK2 communicates with the communication flow path RX2 at an end in the +Z direction and is provided so as to extend in the Z-axis direction. The communication flow path RR2 is provided so as to extend in the Z-axis direction in the +X direction as viewed from the communication flow path RK2 and in the -X direction as viewed from the communication flow path RR1.

[0025] Further, the nozzle flow path RN communicates with the communication flow path RR1 and the communication flow path RR2, and is provided so as to extend in the X-axis direction, in the -X direction as seen from the communication flow path RR1, and in the +X direction as seen from the communication flow path RR2. The nozzle flow path RN communicates with the nozzle N corresponding to the nozzle flow path RN.

[0026] The communicating plate 2 is manufactured by processing a silicon single crystal substrate using semiconductor manufacturing technology, for example. However, any known material or manufacturing method may be used to manufacture the communicating plate 2.

[0027] 2 and 3, a pressure chamber substrate 3 is provided on the -Z side of the communication plate 2. The pressure chamber substrate 3 is a plate-shaped member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and has an ink flow path formed therein.

[0028] Specifically, M pressure chambers CB1 are formed in the pressure chamber substrate 3, each having a one-to-one correspondence with the M nozzles N, and M pressure chambers CB2 are formed in each having a one-to-one correspondence with the M nozzles N. Of these, the pressure chamber CB1 communicates with the communication flow path RK1 and the communication flow path RR1, and is provided so as to extend in the X-axis direction, connecting the +X side end of the communication flow path RK1 to the −X side end of the communication flow path RR1 when viewed from the Z-axis direction. Furthermore, the pressure chamber CB2 communicates with the communication flow path RK2 and the communication flow path RR2, and is provided so as to extend in the X-axis direction, connecting the −X side end of the communication flow path RK2 to the +X side end of the communication flow path RR2 when viewed from the Z-axis direction.

[0029] The pressure chamber substrate 3 is manufactured by processing a silicon single crystal substrate using, for example, semiconductor manufacturing technology. However, any known material or manufacturing method may be used to manufacture the pressure chamber substrate 3.

[0030] In the following, the ink flow path that connects the supply flow path RA1 and the discharge flow path RA2 is referred to as the circulation flow path RJ. As illustrated in FIG. 4, the communication flow paths RX1 and RX2 are connected by M circulation flow paths RJ, which correspond one-to-one to the M nozzles N. As described above, each circulation flow path RJ includes a communication flow path RK1 that communicates with the communication flow path RX1, a pressure chamber CB1 that communicates with the communication flow path RK1, a communication flow path RR1 that communicates with the pressure chamber CB1, a nozzle flow path RN that communicates with the communication flow path RR1, a communication flow path RR2 that communicates with the nozzle flow path RN, a pressure chamber CB2 that communicates with the communication flow path RR2, and a communication flow path RK2 that communicates with the pressure chamber CB2. In this embodiment, as an example, it is assumed that each circulation flow path RJ extends in the X-axis direction.

[0031] As can be seen from FIG. 3 , the nozzle N passes through between the surface FN1 and the surface FN2, connecting the circulation channel RJ to the outside. The circulation channel RJ is provided by the pressure chamber substrate 3 and the communication plate 2. The circulation channel RJ is an example of a "channel." The pressure chamber substrate 3 and the communication plate 2 are an example of a "channel substrate." In other words, in the first embodiment, the "channel substrate" is formed by the pressure chamber substrate 3 and the communication plate 2.

[0032] 2 and 3, a diaphragm 4 is provided on the -Z side of the pressure chamber substrate 3. The diaphragm 4 is a plate-like member that is elongated in the Y-axis direction and extends substantially parallel to the XY plane, and is a member that can vibrate elastically.

[0033] As illustrated in FIGS. 2 and 3, M piezoelectric elements PZ1 corresponding one-to-one to the M pressure chambers CB1 and M piezoelectric elements PZ2 corresponding one-to-one to the M pressure chambers CB2 are provided on the -Z side of the vibration plate 4. Hereinafter, the piezoelectric elements PZ1 and PZ2 will be collectively referred to as piezoelectric element PZq. The piezoelectric element PZq is a passive element that deforms in response to changes in the potential of the drive signal Com. In other words, the piezoelectric element PZq is an example of an "energy generating element" that generates energy for ejecting ink from the nozzle N based on the drive signal Com. Note that, below, the suffix "q" may be added to the reference numeral indicating a component or signal of the liquid ejection head 1 that corresponds to the piezoelectric element PZq.

[0034] Fig. 5 is an enlarged cross-sectional view of the vicinity of the piezoelectric element PZq. As illustrated in Fig. 5, the piezoelectric element PZq is a laminated body in which a piezoelectric body ZMq is interposed between a lower electrode ZDq to which a predetermined reference potential VBS is supplied and an upper electrode ZUq to which a drive signal Com is supplied. When viewed from the -Z direction, for example, the piezoelectric element PZq is the portion where the lower electrode ZDq, the upper electrode ZUq, and the piezoelectric body ZMq overlap. Furthermore, a pressure chamber CBq is provided in the +Z direction of the piezoelectric element PZq.

[0035] As described above, the piezoelectric element PZq is driven and deformed in response to changes in the potential of the drive signal Com. The diaphragm 4 vibrates in conjunction with the deformation of the piezoelectric element PZq. When the diaphragm 4 vibrates, the pressure inside the pressure chamber CBq fluctuates. As the pressure inside the pressure chamber CBq fluctuates, ink filled inside the pressure chamber CBq passes through the communication channel RRq and the nozzle channel RN and is ejected from the nozzle N.

[0036] As illustrated in FIGS. 2 and 3, a wiring board 8 is mounted on the -Z side surface of the diaphragm 4. The wiring board 8 is a component for electrically connecting the control device 90 and the liquid ejection head 1. A flexible wiring board such as an FPC or FFC is preferably used as the wiring board 8. Here, FPC is an abbreviation for Flexible Printed Circuit, and FFC is an abbreviation for Flexible Flat Cable. A drive circuit 81 is mounted on the wiring board 8. The drive circuit 81 is an electric circuit that switches whether or not to supply a drive signal Com to the piezoelectric element PZq under the control of a control signal SI. As illustrated in FIG. 5, the drive circuit 81 supplies the drive signal Com to the upper electrode ZUq of the piezoelectric element PZq via a wiring 810.

[0037] In the following, the drive signal Com supplied to the piezoelectric element PZ1 may be referred to as drive signal Com1, and the drive signal Com supplied to the piezoelectric element PZ2 may be referred to as drive signal Com2. In this embodiment, when ink is ejected from a nozzle N, it is assumed that the waveform of the drive signal Com1 supplied by the drive circuit 81 to the piezoelectric element PZ1 corresponding to the nozzle N is substantially the same as the waveform of the drive signal Com2 supplied by the drive circuit 81 to the piezoelectric element PZ2 corresponding to the nozzle N. Here, "substantially the same" is a concept that includes cases where they are completely the same, as well as cases where they can be considered to be the same taking error into consideration.

[0038] 2 and 3, a storage chamber forming substrate 5 is provided on the −Z side of the communication plate 2. The storage chamber forming substrate 5 is a member that is long in the Y-axis direction, and has an ink flow path formed therein. Specifically, one supply flow path RB1 and one discharge flow path RB2 are formed in the reservoir chamber forming substrate 5. Of these, the supply flow path RB1 is connected to the supply flow path RA1 and is provided so as to extend in the Y-axis direction in the -Z direction as viewed from the supply flow path RA1. The discharge flow path RB2 is connected to the discharge flow path RA2 and is provided so as to extend in the Y-axis direction in the -Z direction as viewed from the discharge flow path RA2 and in the -X direction as viewed from the supply flow path RB1. The reservoir chamber forming substrate 5 is also provided with an inlet 51 communicating with the supply flow path RB1 and an outlet 52 communicating with the discharge flow path RB2. Ink is supplied to the supply flow path RB1 from a liquid container 93 via the inlet 51. Ink stored in the discharge flow path RB2 is recovered via the outlet 52. The reservoir chamber forming substrate 5 is also provided with an opening 50. Inside the opening 50, the pressure chamber substrate 3, the diaphragm 4, and the wiring substrate 8 are provided. The reservoir chamber forming substrate 5 is formed, for example, by injection molding of a resin material. However, any known material or manufacturing method may be used to manufacture the reservoir chamber forming substrate 5.

[0039] In this embodiment, ink supplied from the liquid container 93 to the inlet 51 flows into the supply channel RA1 via the supply channel RB1. Some of the ink that flows into the supply channel RA1 flows into the pressure chamber CB1 via the communication channel RX1 and the communication channel RK1. Some of the ink that flows into the pressure chamber CB1 flows into the pressure chamber CB2 via the communication channel RR1, the nozzle channel RN, and the communication channel RR2. Some of the ink that flows into the pressure chamber CB2 flows into the communication channel RK2, the communication channel RX2, the discharge channel RA2, and the discharge channel RB2, and is discharged from the discharge port 52. When the piezoelectric element PZ1 is driven by the drive signal Com1, some of the ink filling the pressure chamber CB1 is discharged from the nozzle N via the communication channel RR1 and the nozzle channel RN. When the piezoelectric element PZ2 is driven by the drive signal Com2, some of the ink filling the pressure chamber CB2 is discharged from the nozzle N via the communication channel RR2 and the nozzle channel RN.

[0040] 2 and 3, a compliance sheet 61 is provided on the +Z side surface of the communicating plate 2 so as to block the supply channel RA1, the communicating channel RX1, and the communicating channel RK1. The compliance sheet 61 is made of an elastic material and absorbs pressure fluctuations of the ink in the supply channel RA1, the communicating channel RX1, and the communicating channel RK1. Furthermore, a compliance sheet 62 is provided on the +Z side surface of the communicating plate 2 so as to block the discharge channel RA2, the communicating channel RX2, and the communicating channel RK2. The compliance sheet 62 is made of an elastic material and absorbs pressure fluctuations of the ink in the discharge channel RA2, the communicating channel RX2, and the communicating channel RK2.

[0041] As described above, the liquid ejection head 1 according to this embodiment circulates ink from the communication flow path RX1 to the communication flow path RX2 via the circulation flow path RJ. Therefore, in this embodiment, even if there is a period during which the ink inside the pressure chamber CBq is not ejected from the nozzle N, it is possible to prevent ink from remaining stagnant inside the pressure chamber CBq and in the nozzle flow path RN, etc. Therefore, in this embodiment, even if there is a period during which the ink inside the pressure chamber CBq is not ejected from the nozzle N, it is possible to suppress an increase in viscosity of the ink inside the pressure chamber CBq, and it is possible to prevent an ejection abnormality in which ink cannot be ejected from the nozzle N due to an increase in viscosity of the ink.

[0042] Furthermore, the liquid ejection head 1 according to this embodiment can eject the ink filled inside the pressure chamber CB1 and the ink filled inside the pressure chamber CB2 from the nozzle N. Therefore, with the liquid ejection head 1 according to this embodiment, it is possible to increase the amount of ink ejected from the nozzle N, compared to, for example, an embodiment in which only the ink filled inside one pressure chamber CBq is ejected from the nozzle N.

[0043] A3. Drive signal Com Fig. 6 is a diagram for explaining the drive signal Com. The drive signal Com has one or more ejection waveforms PD shown in Fig. 6. The ejection waveform PD has, in this order, a first expansion element EF1, a first hold element PW1, a contraction element ET, a second hold element PW2, and a second expansion element EF2.

[0044] The first expansion element EF1 changes the potential to expand the pressure chamber CBq. Specifically, the first expansion element EF1 changes the potential from a reference potential V0, which is the starting potential of the ejection waveform PD, to a minimum potential VL. The first hold element PW1 is connected to the end of the first expansion element EF1 and maintains the minimum potential VL. The contraction element ET is connected to the end of the first hold element PW1 and changes the potential to contract the pressure chamber CBq. Specifically, the contraction element ET changes the potential from the minimum potential VL to a maximum potential VH. The second hold element PW2 is connected to the end of the contraction element ET and maintains the maximum potential VH. The second expansion element EF2 is connected to the end of the second hold element PW2 and changes the potential to expand the pressure chamber CBq. Specifically, the second expansion element EF2 changes the potential from the maximum potential VH to the reference potential V0.

[0045] When the piezoelectric element PZq receives the ejection waveform PD, it generates a negative pressure in the pressure chamber CBq based on the first expansion element EF1, and then generates a positive pressure in the pressure chamber CBq based on the contraction element ET, thereby ejecting ink from the nozzle N. When negative pressure is generated in the pressure chamber CBq, the surface of the ink in the nozzle N is pulled in the -Z direction. Below, the surface of the ink in the nozzle N may be referred to as the "meniscus." Pulling the meniscus in the -Z direction may also be referred to as "pull." When positive pressure is generated in the pressure chamber CBq, the meniscus is pushed in the +Z direction. Pushing the meniscus in the +Z direction may also be referred to as "push." ​​The ejection waveform PD is a so-called pull-push-pull waveform.

[0046] Hereinafter, the potential difference between the highest potential VH and the lowest potential VL in the ejection waveform PD may be referred to as a potential difference ΔVh.

[0047] A4. About the shape of nozzle N Because the meniscus is exposed to air, solvents such as water contained in the ink may evaporate, causing the ink to thicken. One method for eliminating thickened ink near the nozzle N is to supply unthickened ink to the circulation channel RJ and replace the thickened ink near the nozzle N with unthickened ink. To efficiently replace the ink near the nozzle N, the nozzle N may be configured to include a first nozzle portion that penetrates from the surface FN1 to the connection position SP within the nozzle substrate 60 along the Z-axis direction, and a second nozzle portion that is a hole that penetrates from the connection position SP to the surface FN2. For example, the nozzle NA in the first reference example may include a first nozzle portion NP1 that is provided on the surface FN1 along the Z-axis direction and has the same shape as the opening 601, and a second nozzle portion NAP2 that is provided on the surface FN2 along the Z-axis direction and has the same shape as the opening 602, which is larger than the opening 601. However, air bubbles may be trapped inside the nozzle NA. When air bubbles are introduced into the nozzle NA, the Helmholtz natural frequency within the flow path changes due to the large compliance of the air bubbles. Hereinafter, the Helmholtz natural frequency within the flow path may be referred to as the natural frequency Tc. Compliance is a physical quantity that indicates the ease of deformation due to pressure. The ejection waveform PD is designed to eject ink properly when there are no air bubbles in the flow path. Therefore, if the natural frequency Tc changes, ink ejection may become unstable. Examples of unstable ejection include deviation of the ink ejection direction from the specified direction, failure to eject ink from the nozzle N, and variations in the amount of ink ejected. The phenomenon of air bubbles being introduced into the nozzle NA is explained using Figure 7.

[0048] Fig. 7 is a diagram for explaining the phenomenon of air bubbles being mixed in the nozzle NA of the first reference example. Fig. 7 shows the state of ink near the nozzle NA before and while the ejection waveform PD is supplied to the piezoelectric element PZq when the nozzle N is the nozzle NA.

[0049] At time t1, before the ejection waveform PD is supplied to the piezoelectric element PZq, the vibration of the meniscus MN caused by the previous ejection waveform PD has attenuated. Furthermore, at time t1, the meniscus MN is approximately parallel to the XY plane in the Z-axis direction and at approximately the same position as the opening 601.

[0050] At time t2, which is the time immediately after the first expansion element EF1 starts supplying to the piezoelectric element PZq, the meniscus MN is pulled in the -Z direction. Next, at time t3, which is the time immediately before the first expansion element EF1 finishes supplying to the piezoelectric element PZq, the apex of the meniscus MN in the -Z direction is included inside the second nozzle portion NAP2.

[0051] At time t4, which is the time immediately after the contraction element ET starts supplying to the piezoelectric element PZq, the meniscus MN is pushed in the +Z direction. Furthermore, a portion of the apex of the meniscus MN in the -Z direction is taken into the nozzle NA as a bubble BL. Next, at time t5, which is the time immediately before the contraction element ET finishes supplying to the piezoelectric element PZq, the meniscus MN is pushed further in the +Z direction. Even at time t5, the bubble BL exists inside the nozzle NA.

[0052] The phenomenon shown in Figure 7 is more likely to occur when the following three conditions are met: The first condition is that the reference potential V0 is high; The second condition is that the period of the first expansion element EF1 and the period of the contraction element ET are short; and The third condition is that the potential difference ΔVh is large.

[0053] 7 may also occur in other modes than when the ejection waveform PD is supplied to the piezoelectric element PZq. For example, the phenomenon shown in Fig. 7 may occur even when the ejection waveform PD does not include the second expansion component EF2, i.e., when a so-called pull-push waveform is supplied to the piezoelectric element PZq.

[0054] The reason why air bubbles get mixed in will be explained using the nozzle NA and the nozzle NB of the second reference example.

[0055] FIG. 8 is a diagram illustrating the state of forces acting on ink in nozzle NA. FIG. 9 is a diagram illustrating the state of forces acting on ink in nozzle NB. Nozzle NB differs from nozzle NA in that it has a second nozzle portion NBP2 instead of the second nozzle portion NAP2. The second nozzle portion NBP2 differs from the second nozzle portion NAP2 in that the inner surface of the second nozzle portion NBP2 is linearly inclined with respect to the Z-axis direction. FIG. 8 shows the state of forces acting on ink in nozzle NA at time t3 shown in FIG. 7. FIG. 9 shows the state of forces acting on ink in nozzle NB at time t3 when an ejection waveform PD is supplied to piezoelectric element PZq corresponding to pressure chamber CBq communicating with nozzle NB. In FIGS. 8 and 9, arrows drawn inside the ink indicate the magnitude and direction of the forces acting on the ink.

[0056] 8 and 9, the volume of ink below the second nozzle portion NBP2 is smaller than the volume of ink below the second nozzle portion NAP2. Therefore, the magnitude of the force in the ink of the nozzle NB toward the nozzle central axis AZ is smaller than the magnitude of the force in the ink of the nozzle NA toward the nozzle central axis AZ. By reducing the magnitude of the force toward the nozzle central axis AZ, the force that directs the ink toward the nozzle central axis AZ is reduced, so the nozzle NB can be less likely to take in air bubbles than the nozzle NA.

[0057] However, even in the nozzle NB in ​​which the inner surface of the second nozzle part NBP2 is linearly inclined with respect to the Z-axis direction, the meniscus MN may break and air bubbles may get mixed in the inside of the nozzle NB. Below, we will explain what happens when air bubbles get mixed in the inside of the nozzle NB.

[0058] If the wall surface SFB2 at the top of the second nozzle portion NBP2 of the nozzle NB is gently inclined, the meniscus MN may collapse, causing air bubbles to be mixed in. Generally, ink is ejected from the nozzle by applying pressure to the nozzle from a pressure chamber located in the -Z direction from the nozzle. The area near the top of the second nozzle portion NBP2 is the region to which pressure from the pressure chamber CBq is applied. If the wall surface SFB2 near the top of the second nozzle portion NBP2 is gently inclined, the pressure transmitted toward the first nozzle portion NP1 of the nozzle NB may become excessive. Below, using Figures 10 and 11, we will explain cases where the pressure transmitted toward the first nozzle portion NP1 of the nozzle NB becomes excessive.

[0059] 10 and 11 are diagrams illustrating a case where the pressure transmitted toward the first nozzle portion NP1 of the nozzle NB becomes excessive. The arrows in the ink in FIGS. 10 and 11 indicate the magnitude and direction of the pressure from the pressure chamber CBq. The inclination of the wall surface SFB2 shown in FIG. 10 is gentler than the inclination of the wall surface SFB2 shown in FIG. 11. As can be seen from FIGS. 10 and 11, when the wall surface SFB2 of the second nozzle portion NBP2 is linearly inclined with respect to the Z-axis direction, the opening 602 becomes larger as the inclination of the wall surface SFB2 becomes gentler. Since the magnitude of the force is the product of the area and the pressure, as the opening 602 becomes larger, i.e., the area becomes larger, the magnitude of the force acting downward from the pressure chamber CBq relative to the surface FN2 increases. Because the cross-sectional area of ​​the first nozzle portion NP1 in the Z-axis direction is the same in FIGS. 10 and 11, the pressure transmitted toward the first nozzle portion NP1 of the nozzle NB shown in FIG. 10 becomes excessive compared to the nozzle NB shown in FIG. 11. If the pressure transmitted toward the first nozzle portion NP1 of the nozzle NB becomes excessive, there is a risk that the meniscus MN will break.

[0060] If the inclination of the wall surface SFB2 at the bottom of the second nozzle portion NBP2 of the nozzle NB is steep, the -Z-direction point of the meniscus MN is more likely to reach the second nozzle portion NBP2, causing the meniscus MN to collapse and potentially introducing air bubbles. Generally, the smaller the cross-sectional area of ​​the nozzle as viewed in the Z-axis direction, the more easily the meniscus MN flows in the Z-axis direction. This is because, if the volume of the pressure chamber CBq fluctuates, the amount of ink inside the nozzle N increases or decreases in accordance with the fluctuating volume. Furthermore, since the volume is calculated by multiplying the cross-sectional area by the height if the cross-sectional shape is constant, the smaller the cross-sectional area of ​​the nozzle in the Z-axis direction, the longer the length of the flow in the Z-axis direction. If the inclination of the wall surface SFB2 at the bottom of the second nozzle portion NBP2 is steep, this means that the cross-sectional area as viewed in the Z-axis direction does not change significantly. Therefore, since the ease with which the meniscus MN flows in the Z-axis direction is not significantly different between the first nozzle portion NP1 and the second nozzle portion NBP2, it is thought that the meniscus MN flows more easily into the second nozzle portion NBP2. On the other hand, if the slope of the wall surface SFB2 is gentle at the lower part of the second nozzle portion NBP2, the cross-sectional area of ​​the second nozzle portion NBP2 when viewed in the Z-axis direction will be larger than the cross-sectional area of ​​the first nozzle portion NP1 when viewed in the Z-axis direction. Therefore, the ease with which the meniscus MN flows in the Z-axis direction in the second nozzle portion NBP2 will be smaller than the ease with which the meniscus MN flows in the Z-axis direction in the first nozzle portion NP1, making it more difficult for the apex of the meniscus MN in the -Z direction to reach the inside of the second nozzle portion NBP2, and making it more difficult for the meniscus MN to collapse.

[0061] From the above, the inventors have found through experiments and experience that it is better to make the inclination of the wall surface SFB2 steeper in the upper part of the second nozzle portion NBP2 of the nozzle N and to make the inclination of the wall surface SFB2 gentler in the lower part of the second nozzle portion NBP2. Hereinafter, the nozzle N in the first embodiment will be described with reference to Figures 12 to 14.

[0062] A5: Shape of the nozzle N in the first embodiment FIG. 12 is a view of nozzle N viewed in the +Z direction. FIG. 13 is a cross-sectional view taken along line XIII-XIII in FIG. 12, and FIG. 14 is a cross-sectional view taken along line XIV-XIV in FIG. 12. Nozzle N differs from nozzle NA and nozzle NB in ​​that it includes a second nozzle portion NP2. The first nozzle portion NP1 penetrates from the surface FN1 to the connection position SP within the nozzle substrate 60. The second nozzle portion NP2 is a hole that penetrates from the connection position SP to the surface FN2. The width of the first nozzle portion NP1 in the X-axis direction is constant regardless of its position in the Z-axis direction. Specifically, the width of the first nozzle portion NP1 in the X-axis direction is twice the length of the radius R1 of the opening 601. As shown in FIGS. 13 and 14, the first nozzle portion NP1 extends along the Z-axis direction. However, the extension direction of the first nozzle portion NP1 is not limited to the Z-axis direction, and may be inclined with respect to the Z-axis direction. As shown in Fig. 12, when viewed in the +Z direction, the outline of the opening 601 and the outline of the opening 602 are circular. However, the outline of the opening 601 and the outline of the opening 602 are not limited to being circular and may be elliptical. As shown in Fig. 12, when viewed in the +Z direction, the center of the opening 601 and the center of the opening 602 overlaps with the nozzle central axis AZ.

[0063] The Z-axis direction is an example of a "first direction." The X-axis direction is an example of a "second direction." The Y-axis direction is an example of a "third direction." However, the "second direction" is not limited to the X-axis direction as long as it is a direction perpendicular to the Z-axis direction. Furthermore, the "third direction" may be any direction perpendicular to the "first direction" and the "second direction."

[0064] As shown in FIGS. 13 and 14, the position of the connection position SP in the Z-axis direction is position z0.

[0065] The width of the second nozzle portion NP2 in the X-axis direction gradually increases, with the amount of width expansion in the X-axis direction decreasing as the position in the Z-axis direction approaches the surface FN2. In other words, the slope of the wall surface SF2 is gentle at the bottom of the second nozzle portion NP2 and becomes steeper toward the top of the second nozzle portion NP2. The minimum width of the second nozzle portion NP2 in the X-axis direction is twice the radius R1 of the opening 601. The maximum width of the second nozzle portion NP2 in the X-axis direction is twice the radius R2 of the opening 602. As shown in FIG. 13 , the width x2 in the X-axis direction when the position in the Z-axis direction is position z2 is longer than the width x1 in the X-axis direction when the position in the Z-axis direction is position z1. Position z2 is located in the -Z direction relative to position z1. The amount of width expansion Δx1 in the X-axis direction at position z1 is greater than the amount of width expansion Δx2 in the X-axis direction at position z2. The expansion amount Δx1 and the expansion amount Δx2 are the expansion amounts of the width in the X-axis direction relative to the minute amount Δz in the Z-axis direction. Position z1 and position z2 are arbitrary positions in the Z-axis direction within the second nozzle portion NP2. The minute amount Δz may be any length, but is preferably, for example, approximately 5% to 15% of the width LZ2 of the second nozzle portion NP2 in the Z-axis direction.

[0066] As shown in FIG. 14, the width of the first nozzle portion NP1 in the Y-axis direction is constant regardless of its position in the Z-axis direction. The width of the first nozzle portion NP1 in the Y-axis direction is twice the radius R1, and the minimum width of the second nozzle portion NP2 in the Y-axis direction is twice the radius R1. The maximum width of the second nozzle portion NP2 in the Y-axis direction is twice the radius R2. As shown in FIG. 14, the width y2 in the Y-axis direction at position z2 is longer than the width y1 in the Y-axis direction at position z1. The amount of width expansion Δy1 in the Y-axis direction at position z1 is greater than the amount of width expansion Δy2 in the X-axis direction at position z2.

[0067] As shown in FIG. 13, when viewed from the +Y direction, the wall surface SF2 of the nozzle substrate 60 that defines the second nozzle portion NP2 is curved. Specifically, the outline of the wall surface SF2 when viewed from the +Y direction is an arc. Similarly, as shown in FIG. 14, when viewed from the +X direction, the wall surface SF2 of the nozzle substrate 60 that defines the second nozzle portion NP2 is curved. Specifically, the outline of the wall surface SF2 when viewed from the +X direction is an arc. In other words, the wall surface SF2 is formed so that the surface FN2 is hollowed out in a substantially hemispherical shape. The curvature of the wall surface SF2 is constant. However, the curvature of the wall surface SF2 does not have to be constant.

[0068] 13, at the connection position SP, the width of the first nozzle portion NP1 in the Z-axis direction and the width of the second nozzle portion NP2 in the Z-axis direction are equal to each other. In other words, at the connection position SP, there is no plane parallel to the XY plane. Note that "the two widths are equal to each other" includes not only the case where the two widths are completely equal, but also the case where the two widths can be considered equal when error is taken into consideration.

[0069] As shown in Fig. 13, the angle θ1 at the connection position SP is in the range of 180 degrees or more and 270 degrees or less. The angle θ1 is the angle on the nozzle N side of the angle formed between the first nozzle portion NP1 and the second nozzle portion NP2. Specifically, the angle θ1 is an angle of 180 degrees or more formed between the wall surface SF1 of the first nozzle portion NP1 and the tangent line TL1 at the connection position SP of the second nozzle portion NP2 in a cross section that is parallel to the XZ plane and passes through the nozzle central axis AZ. The angle θ1 is an example of the "first angle."

[0070] The angle θ1 is preferably in the range of 217 degrees or more and 270 degrees or less, and more preferably in the range of 250 degrees or more and 270 degrees or less. The angle θ1 is, for example, 253 degrees. The angle θ1 can also be said to be the angle obtained by adding the angle θ3 to 180 degrees. The angle θ3 is the angle of the tangent line TL1 to the Z axis. The angle θ3 is, for example, 73 degrees. The angle θ1 is preferably greater than the angle obtained by adding the angle θ4 to 180 degrees. The angle θ4 is the angle of the imaginary line segment LV1 with respect to the Z axis direction in a cross section that is parallel to the XZ plane and passes through the nozzle central axis AZ. The imaginary line segment LV1 is a line segment connecting the connection position SP of the second nozzle part NP2 and the connection position SQ of the second nozzle part NP2 and the opening 602. The angle θ4 can be calculated, for example, as follows.

[0071] θ4=arctan((R2-R1) / LZ2)

[0072] However, arctan() is the inverse function of the tangent function.

[0073] As shown in FIG. 13, angle θ2 is in the range of 180 degrees or more and 270 degrees or less. Angle θ2 is the angle on the nozzle N side of the angle between the second nozzle portion NP2 and the surface FN2. Specifically, angle θ2 is parallel to the YZ plane, and is an angle of 180 degrees or more between the surface FN2 and a tangent TL2 to the opening 602 of the second nozzle portion NP2 in a cross section passing through the nozzle central axis AZ. Angle θ2 is preferably greater than angle θ1. Furthermore, angle θ2 is preferably greater than the angle obtained by adding angle θ5 to 180 degrees. Angle θ5 is the angle obtained by subtracting angle θ4 from 90 degrees. Angle θ2 is an example of a "second angle."

[0074] As shown in FIGS. 13 and 14, the width LZ1 of the first nozzle portion NP1 in the Z-axis direction is shorter than the width LZ2.

[0075] A5: Summary of the first embodiment As described above, the liquid ejection head 1 in the first embodiment includes a pressure chamber substrate 3 and a communication plate 2 in which a circulation channel RJ is provided, a nozzle substrate 60 in which a nozzle N is provided that connects the circulation channel RJ to the outside by penetrating between surfaces FN1 and FN2 and whose surface FN2 is joined to the communication plate 2, and a piezoelectric element PZq that generates energy for ejecting ink from the nozzle N. If the direction in which the communication plate 2 and the nozzle substrate 60 are stacked is the Z-axis direction and the direction perpendicular to the Z-axis direction is the X-axis direction, the nozzle N is composed of a first nozzle portion NP1 that penetrates from surface FN1 to a connection position SP in the nozzle substrate 60, and a second nozzle portion NP2 that is a hole that penetrates from the connection position SP to surface FN2. The width of the first nozzle portion NP1 in the X-axis direction is constant regardless of its position in the Z-axis direction. The width of the second nozzle portion NP2 in the X-axis direction gradually increases, with the amount of increase in width in the X-axis direction decreasing as the position in the X-axis direction approaches the surface FN2. According to the first embodiment, by making the inclination of the wall surface SF2 in the X-axis direction steeper at the upper part of the second nozzle portion NP2 and gentler at the lower part of the second nozzle portion NP2, it is possible to prevent the meniscus MN from breaking up, compared to the nozzle NB of the second reference example. By preventing the meniscus MN from breaking up, it is possible to prevent air bubbles from entering the nozzle N.

[0076] At the connection position SP, the width of the first nozzle portion NP1 in the Z-axis direction and the width of the second nozzle portion NP2 in the Z-axis direction are equal to each other. In nozzles where a surface parallel to the XY plane exists at the connection position SP, ink may stagnate on this parallel surface, causing thickened ink to accumulate. Therefore, according to the first embodiment, air bubbles can be prevented from accumulating compared to nozzles where a surface parallel to the XY plane exists at the connection position SP.

[0077] Furthermore, when the second nozzle portion NP2 is viewed from the Y-axis direction, which is orthogonal to the Z-axis and X-axis directions, the wall surface SF2 of the nozzle substrate 60 that defines the second nozzle portion NP2 is curved. According to the first embodiment, the flow inside the nozzle N can be made smoother compared to the aspect in which the wall surface SF2 is in the shape of a broken line.

[0078] At the connection position SP, the angle θ1 is in the range of 180 degrees or more and 270 degrees or less. Furthermore, at the connection position SP, the angle θ1 is preferably in the range of 217 degrees or more and 270 degrees or less, and more preferably in the range of 250 degrees or more and 270 degrees or less.

[0079] Furthermore, the angle θ2 is in the range of greater than 180 degrees and less than 270 degrees. Furthermore, the angle θ2 is preferably greater than the angle θ1. Combining the above ranges, the angle θ1 is preferably greater than 250 degrees and less than the angle θ2. When the angle θ2 is greater than the angle θ1, the inclination of the wall surface SF2 at the −Z direction end of the second nozzle portion NP2 is steeper than in a case where the angle θ1 is greater than the angle θ2. This prevents excessive pressure from being transmitted to the first nozzle portion NP1 of the nozzle NB. Furthermore, in a case where the angle θ1 is greater than the angle θ2, for example, when the angle θ1 is very close to 270 degrees, a region that is not strictly horizontal to the XY plane but can be considered to be approximately horizontal occurs near the connection position SP of the second nozzle portion NP2. This region can cause ink to stagnate, resulting in thickened ink accumulating. As a result, according to the first embodiment, compared to the case where angle θ1 is greater than angle θ2, it is possible to prevent the pressure transmitted toward the first nozzle portion NP1 of the nozzle NB from becoming excessive, while also preventing thickened ink from accumulating.

[0080] Furthermore, the width of the first nozzle portion NP1 in the Y-axis direction is constant regardless of its position in the Z-axis direction, and the width of the second nozzle portion NP2 in the Y-axis direction gradually increases as its position in the Z-axis direction approaches face FN2, with the amount of increase in width in the Y-axis direction decreasing. According to the first embodiment, by making the slope in the Y-axis direction steeper at the upper part of the second nozzle portion NP2 and gentler at the lower part of the second nozzle portion NP2, the collapse of the meniscus MN is suppressed compared to the nozzle NB, which is the second reference example, and the inclusion of air bubbles can be suppressed.

[0081] Furthermore, the width LZ1 of the first nozzle portion NP1 in the Z-axis direction is shorter than the width LZ2 of the second nozzle portion NP2 in the Z-axis direction. By shortening the width LZ1, the resistance to the ink is reduced. Therefore, if the ink is highly viscous, it is preferable to shorten the width LZ1. However, shortening the width LZ1 makes it easier for the meniscus MN to reach the second nozzle portion NP2. Therefore, even if the ink is highly viscous, the nozzle N in the first embodiment can prevent the meniscus MN from breaking.

[0082] B: Second embodiment The shape of the nozzle N is not limited to the nozzle N shown in the first embodiment. A second embodiment will be described below.

[0083] Fig. 15 is a diagram for explaining the nozzle NC in the second embodiment. Fig. 15 shows a cross section of the nozzle NC taken along line XIII-XIII in Fig. 12. The nozzle NC differs from the nozzle N in that it has a second nozzle portion NPC2 instead of the second nozzle portion NP2.

[0084] Similar to the second nozzle portion NP2, the width of the second nozzle portion NPC2 in the X-axis direction gradually increases as its position in the Z-axis direction approaches the plane FN2, with the amount of width expansion in the X-axis direction decreasing. In other words, the slope of the wall surface SFC2 is gentle at the bottom of the second nozzle portion NPC2, and the slope of the wall surface SFC2 becomes steeper toward the top of the second nozzle portion NPC2. However, in the second embodiment, the ratio of the radius RC2 of the opening 602C to the radius R1 of the opening 601 is smaller than the ratio of the radius R2 of the opening 602 to the radius R1 of the opening 601. As shown in FIG. 15 , the width xC2 in the X-axis direction when the position in the Z-axis direction is position z2 is longer than the width xC1 in the X-axis direction when the position in the Z-axis direction is position z1. The amount of width expansion ΔxC1 in the X-axis direction at position z1 is greater than the amount of width expansion ΔxC2 in the X-axis direction at position z2.

[0085] Although not shown, the width in the Y-axis direction at position z2 is longer than the width in the Y-axis direction at position z1. The amount of increase in width in the Y-axis direction at position z1 is greater than the amount of increase in width in the X-axis direction at position z2.

[0086] As shown in Fig. 15, the angle θC1 at the connection position SP is in the range of 180 degrees or more and 270 degrees or less. The angle θC1 is the angle on the nozzle N side of the angle formed between the first nozzle portion NP1 and the second nozzle portion NPC2. Specifically, the angle θC1 is an angle of 180 degrees or more formed between the wall surface SF1 and a tangent line TLC1 at the connection position SP of the second nozzle portion NPC2 in a cross section that is parallel to the XZ plane and passes through the nozzle central axis AZ. In the second embodiment, the angle θC1 is an example of the "first angle."

[0087] Like angle θ1, angle θC1 is preferably in the range of 217 degrees or more and 270 degrees or less, and more preferably in the range of 250 degrees or more and 270 degrees or less. Angle θC1 is, for example, 217 degrees. Angle θC1 can also be said to be the angle obtained by adding angle θC3 to 180 degrees. Angle θC3 is the angle of tangent line TLC1 with respect to the Z axis. Angle θC3 is, for example, 37 degrees.

[0088] As shown in FIG. 15, the angle θC2 is in the range of 180 degrees or more and 270 degrees or less. The angle θC2 is the angle on the nozzle N side of the angle formed between the second nozzle portion NPC2 and the surface FN2. Specifically, the angle θC2 is parallel to the YZ plane, and is an angle of 180 degrees or more formed between the surface FN2 and a tangent TLC2 to the opening 602 of the second nozzle portion NPC2 in a cross section passing through the nozzle central axis AZ. The angle θC2 is preferably larger than the angle θC1. In the second embodiment, the angle θC2 is an example of the "second angle."

[0089] C: Modified Example The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within the scope of not mutually contradictory.

[0090] C1: First modified example In each of the above-described embodiments, the width LZ1 of the first nozzle portion NP1 in the Z-axis direction is shorter than the width LZ2 of the first nozzle portion NP1 in the Z-axis direction, but this is not limited to this. A first modified example will now be described.

[0091] Fig. 16 is a diagram illustrating a nozzle ND in a first modified example. Fig. 15 shows a cross section of the nozzle ND taken along line XIII-XIII in Fig. 12. The nozzle ND differs from the nozzle N in that it has a first nozzle portion NPD1 instead of the first nozzle portion NP1 and a second nozzle portion NPD2 instead of the second nozzle portion NP2. The width LZD1 in the Z-axis direction of the first nozzle portion NPD1 is longer than the width LZD2 in the Z-axis direction of the second nozzle portion NPD2.

[0092] The nozzle ND is particularly effective when, for example, the nozzle substrate 60 is thin, or when the ink is highly viscous and it is desired to increase the diameter of the second nozzle portion NPD2.

[0093] C2: Second modified example In each of the above-described embodiments, the pressure chamber substrate 3 and the communication plate 2 are separate bodies, but they may also be an integrated flow path substrate.

[0094] C3: Third modified example In each of the above-described embodiments, the nozzle N communicates with the nozzle flow path RN, but this is not limiting. For example, the nozzle N may be located in the +Z direction of the communication flow path RR1 in the nozzle substrate 60. Alternatively, the circulation flow path RJ may not have the communication flow path RR1, and the nozzle N may be located at the opening of the pressure chamber CB1 in the -X direction.

[0095] C4: Fourth variant In the above-described embodiments, the piezoelectric element PZq is an example of an "energy generating element," but is not limited to this. The energy generating element may be a heating element that converts electrical energy into thermal energy and generates bubbles inside the pressure chamber CBq by heating, thereby varying the pressure inside the pressure chamber CBq.

[0096] C5: Fifth variant In each of the above-described embodiments, a serial-type liquid ejection device in which a storage case 921 containing a liquid ejection head 1 is moved 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 medium PP.

[0097] C6: Sixth Variation The liquid ejection device 100 exemplified in each of the above-described embodiments can be employed in various devices, such as facsimile machines and copiers, as well as devices dedicated to printing. However, the uses 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 organism is used as a manufacturing device for manufacturing biochips, for example. [Explanation of symbols]

[0098] 1...liquid ejection head, 2...communication plate, 3...pressure chamber substrate, 4...vibration plate, 5...storage chamber forming substrate, 8...wiring substrate, 50...opening, 51...inlet port, 52...outlet port, 60...nozzle substrate, 61, 62...compliance sheet, 81...drive circuit, 90...control device, 91...movement mechanism, 92...transport mechanism, 93...liquid container, 94...circulation mechanism, 100...liquid ejection device, 601, 602, 602C...opening, 810...wiring, 921...storage case, 922... endless belt, AZ... nozzle center axis, BL... air bubble, CB1, CB2, CBq... pressure chamber, Com, Com1, Com2... drive signal, EF1... first expansion element, EF2... second expansion element, ET... contraction element, FN1, FN2... surface, LV1... virtual line segment, Ln... nozzle row, MN... meniscus, N, NA, NB, NC, ND... nozzle, NAP2, NBP2... second nozzle section, NP1, NPD1... first nozzle section, NP2, NPC2, NPD2...second nozzle part, PD...discharge waveform, PP...medium, PW1...first holding element, PW2...second holding element, PZ1, PZ2, PZq...piezoelectric element, R1, R2...radius, RA1...supply flow path, RA2...discharge flow path, RB1...supply flow path, RB2...discharge flow path, RC2...radius, RJ...circulation flow path, RK1, RK2...connecting flow path, RN...nozzle flow path, RR1, RR2, RRq, RX1, RX2...connecting flow path, SF1, SF2, SFB2, S FC2...wall surface, SI...control signal, SP,SQ...connection position, TL1,TL2,TLC1,TLC2...tangent, Tc...natural vibration frequency, V0,VBS...reference potential, VH...highest potential, VL...lowest potential, ZDq...lower electrode, ZMq...piezoelectric body, ZUq...upper electrode, ΔVh...potential difference, Δx1,Δx2,ΔxC1,ΔxC2,Δy1,Δy2...magnification amount, Δz...minute amount, θ1,θ2,θ3,θ4,θ5,θC1,θC2,θC3...angle.

Claims

1. a flow channel substrate on which a flow channel is provided; a nozzle substrate having a first surface and a second surface, the nozzle penetrating between the first surface and the second surface and communicating the flow path with the outside, and the second surface joined to the flow path substrate; an energy generating element that generates energy for ejecting liquid from the nozzle; and a direction in which the flow path substrate and the nozzle substrate are stacked is referred to as a first direction; When a direction perpendicular to the first direction is defined as a second direction, the nozzle is composed of a first nozzle portion that penetrates from the first surface to a connection position in the nozzle substrate, and a second nozzle portion that is a hole that penetrates from the connection position to the second surface, the first nozzle portion has a constant width in the second direction regardless of its position in the first direction, A liquid ejection head characterized in that the second nozzle portion gradually increases in width in the second direction, with the amount of increase in width in the second direction decreasing as the position in the first direction approaches the second surface.

2. 2. The liquid ejection head according to claim 1, wherein, at the connection position, the width of the first nozzle portion in the first direction and the width of the second nozzle portion in the first direction are equal to each other.

3. The liquid ejection head according to claim 1, characterized in that, when the second nozzle portion is viewed from a third direction perpendicular to the first direction and the second direction, the wall surface of the nozzle substrate defining the second nozzle portion is curved.

4. 2. The liquid ejection head according to claim 1, wherein, at the connection position, a first angle, which is an angle on the nozzle side of the angle formed between the first nozzle portion and the second nozzle portion, is within a range of 180 degrees or more and 270 degrees or less.

5. 5. The liquid ejection head according to claim 4, wherein the first angle is in the range of 217 degrees to 270 degrees at the connection position.

6. 6. The liquid ejection head according to claim 5, wherein the first angle is in the range of 250 degrees to 270 degrees at the connection position.

7. The liquid ejection head according to claim 4 , wherein a second angle, which is an angle on the nozzle side of the angle formed between the second nozzle portion and the second surface, is within a range of 180 degrees or more and 270 degrees or less.

8. 8. The liquid ejection head according to claim 7, wherein the second angle is larger than the first angle.

9. When a direction perpendicular to the first direction and the second direction is defined as a third direction, the first nozzle portion has a constant width in the third direction regardless of its position in the first direction, The liquid ejection head according to claim 1, characterized in that the width of the second nozzle portion in the third direction gradually increases as the position in the first direction approaches the second surface, with the amount of increase in width in the third direction decreasing.

10. 2. The liquid ejection head according to claim 1, wherein the width of the first nozzle portion in the first direction is smaller than the width of the second nozzle portion in the first direction.

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