Liquid dispensing head and liquid dispensing system

Abstract

To improve performance of discharging air bubble mixing in liquid in individual flow paths, without increasing flow rates of liquid flowing through the individual flow paths.SOLUTION: A liquid discharge head 1 comprises: first substrates 11c and 11d having lower surfaces to which a nozzle 21 opens and having a pressure chamber 23 communicated with the nozzle formed therein; and a piezoelectric element 12 arranged on an upper surface of the first substrate to oppose to the pressure chamber. The pressure chamber extends in a first direction, which has liquid inflow port 23x and a liquid outflow port 23y at one end side and at the other end side in the first direction. The nozzle is arranged between the inflow port and the outflow port in the first direction. When viewed from a second direction orthogonal to the first direction, an upper wall 23a of the pressure chamber is curved to protrude downward, in a state where voltages are not yet applied to the piezoelectric element.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a liquid ejection head that ejects liquid from a nozzle and a liquid ejection system including the liquid ejection head.

Background Art

[0002] As a liquid ejection head, an inkjet recording head (see Patent Document 1) including a nozzle, a pressure chamber communicating with the nozzle, an ink supply passage connected to one end of the pressure chamber, and an ink discharge passage connected to the other end of the pressure chamber is known. In this inkjet recording head, ink is circulated through the ink supply passage, the pressure chamber, and the ink discharge passage. Thereby, sedimentation of ink components in the ink flow path and drying of the ink near the nozzle can be prevented. In addition, air bubbles mixed in the ink in the ink flow path can be discharged.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the inkjet recording head having the above configuration, when the flow rate of the ink in the pressure chamber is increased, the ejection direction of the ink droplets ejected from the nozzle may tilt from a desired direction to a certain direction. Specifically, the ejection direction of the ink droplets may tilt from a desired direction (for example, the vertical direction) to the direction in which the ink flows in the pressure chamber (the direction from the above one end to the above other end of the pressure chamber). Therefore, it is not preferable to increase the flow rate of the ink in the pressure chamber. However, when the flow rate of the ink in the pressure chamber is not increased, it becomes difficult to efficiently discharge air bubbles mixed in the ink in the pressure chamber.

[0005] The present invention aims to improve the discharge of air bubbles mixed in the liquid within a pressure chamber without increasing the flow rate of the liquid flowing through the pressure chamber, in a liquid discharge head equipped with a configuration for circulating the liquid within a pressure chamber. [Means for solving the problem]

[0006] According to an aspect of the present invention, a liquid discharge head is provided, comprising: a first substrate having a lower surface from which a nozzle opens and a pressure chamber communicating with the nozzle formed therein; and a piezoelectric element disposed on the upper surface of the first substrate so as to face the pressure chamber, wherein the pressure chamber extends in a first direction parallel to the lower surface of the first substrate, has a liquid inlet at one end in the first direction and a liquid outlet at the other end in the first direction, the nozzle is disposed between the inlet and the outlet in the first direction, and when viewed from a second direction parallel to the lower surface of the first substrate and perpendicular to the first direction, the upper wall of the pressure chamber is curved to be convex downward when no voltage is applied to the piezoelectric element.

[0007] In a liquid discharge head according to an aspect of the present invention, the upper wall of the pressure chamber is curved such that it is convex downward when viewed from the second direction and no voltage is applied to the piezoelectric element. Within the pressure chamber, the liquid flows from the inlet to the outlet. Therefore, even if air bubbles enter the liquid in the pressure chamber from the nozzle, these bubbles can be easily moved along the upper wall of the pressure chamber to the outlet. In other words, in a liquid discharge head having a configuration that circulates the liquid in the pressure chamber, it is possible to improve the discharge of air bubbles mixed in the liquid in the pressure chamber without increasing the flow rate of the liquid flowing through the pressure chamber. [Effects of the Invention]

[0008] According to the liquid discharge head of the present invention, it is possible to improve the discharge of air bubbles mixed in the liquid within the pressure chamber without increasing the flow rate of the liquid flowing through the pressure chamber. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view of a printer equipped with a head according to an embodiment of the present invention. [Figure 2] This is a plan view of the head. [Figure 3] This is a cross-sectional view of the head along the line III-III in Figure 2. [Figure 4] This is a block diagram showing the electrical configuration of a printer. [Figure 5] This is a cross-sectional view of the modified head, corresponding to Figure 3. [Figure 6] This is a cross-sectional view corresponding to Figure 3 of a head relating to another modified example. [Modes for carrying out the invention]

[0010] Referring to Figure 1, a schematic configuration of a printer 100 equipped with a head 1 according to an embodiment of the present invention will be described.

[0011] The printer 100 (an example of a liquid ejection system) comprises a head unit 1x including four heads 1 (an example of a liquid ejection head), a platen 3, a transport mechanism 4, and a controller 5.

[0012] A sheet of paper 9 is placed on top of the platen 3.

[0013] The transport mechanism 4 comprises two pairs of rollers 4a and 4b. When the transport motor 4m is driven by the controller 5, the pairs of rollers 4a and 4b rotate while gripping the paper 9, and the paper 9 is transported in the transport direction (an example of the first direction). The two pairs of rollers 4a and 4b are positioned to grip the platen 3 in the transport direction.

[0014] The head unit 1x is a line-type (a system in which ink is ejected from the nozzles 21 (see Figures 2 and 3) onto the paper 9 while its position is fixed) and is elongated in the paper width direction (an example of a second direction). The four heads 1 are arranged in a staggered pattern in the paper width direction.

[0015] Here, the paper width direction is orthogonal to the conveyance direction. Both the paper width direction and the conveyance direction are orthogonal to the vertical direction.

[0016] The controller 5 has a ROM (Read Only Memory), a RAM (Random Access Memory), and an ASIC (Application Specific Integrated Circuit). The ASIC executes recording processing and the like according to the program stored in the ROM. In the recording process, the controller 5 controls the driver IC 1d (see FIG. 4) of each head 1 and the conveyance motor 4m based on a recording command (including image data) input from an external device such as a PC, and records an image on the paper 9. Further, the controller 5 controls the positive pressure pump 7P and the negative pressure pump 7Q (see FIGS. 2 and 4), and circulates ink between the ink tank 7 and each head 1 as will be described later.

[0017] Next, referring to FIGS. 2 and 3, the configuration of the head 1 will be described.

[0018] The head 1 has a flow path substrate 11 and a plurality of piezoelectric elements 12.

[0019] As shown in FIG. 3, the flow path substrate 11 has four plates 11a to 11d adhered to each other. All of the plates 11a to 11d are formed of silicon, but the upper surface side of the plate 11c has become silicon oxide by firing when forming the piezoelectric layer 12b described later. A common flow path 30 is formed in the plate 11a. A plurality of individual flow paths 20 are formed in the plates 11b to 11d. The plurality of individual flow paths 20 are located below the common flow path 30. The plates 11c and 11d adhered to each other are an example of the first substrate. The plates 11a and 11b adhered to each other are an example of the second substrate.

[0020] As shown in FIG. 2, the common flow path 30 includes feedback flow paths 31 and 32 and a supply flow path 33 arranged in the conveyance direction. The feedback flow paths 31 and 32 and the supply flow path 33 each extend in the paper width direction. The supply flow path 33 is arranged between the feedback flow path 31 and the feedback flow path 32 in the conveyance direction.

[0021] The supply flow path 33 communicates with the ink tank 7 through a supply port 33x. The feedback flow paths 31 and 32 each communicate with the ink tank 7 through discharge ports 31y and 32y, respectively. The supply port 33x is formed at one end (the upper side in FIG. 2) of the supply flow path 33 in the paper width direction. The discharge ports 31y and 32y are each formed at the other end (the lower side in FIG. 2) of the feedback flow paths 31 and 32 in the paper width direction. The supply port 33x and the discharge ports 31y and 32y open on the upper surface of the plate 11a.

[0022] The ink tank 7 stores the ink supplied to the head 1.

[0023] The individual flow paths 20 include a plurality of first individual flow paths 20a connecting the feedback flow path 31 and the supply flow path 33, and a plurality of second individual flow paths 20b connecting the feedback flow path 32 and the supply flow path 33. The plurality of first individual flow paths 20a are arranged at equal intervals in the paper width direction. Similarly, the plurality of second individual flow paths 20b are also arranged at equal intervals in the paper width direction. The plurality of first individual flow paths 20a are shifted by a half pitch in the paper width direction with respect to the plurality of second individual flow paths 20b. Each first individual flow path 20a straddles the feedback flow path 31 and the supply flow path 33 in the conveyance direction. Each second individual flow path 20b straddles the feedback flow path 32 and the supply flow path 33 in the conveyance direction.

[0024] As shown in FIG. 2, the ink in the ink tank 7 is supplied from the supply port 33x to the supply flow path 33 by driving the positive pressure pump 7P under the control of the controller 5. The ink supplied to the supply flow path 33 is supplied to each of the plurality of first individual flow paths 20a and the plurality of second individual flow paths 20b while moving from one side to the other side in the paper width direction within the supply flow path 33. The ink supplied to the multiple first individual flow paths 20a flows out into the return flow path 31 and moves within the return flow path 31 from one side to the other in the paper width direction. Then, under the control of the controller 5, the negative pressure pump 7Q is driven, and the ink is discharged from the return flow path 31 via the outlet 31y and returned to the ink tank 7. The ink supplied to the multiple second individual flow paths 20b flows out into the return flow path 32 and moves within the return flow path 32 from one side to the other in the paper width direction. Then, under the control of the controller 5, the negative pressure pump 7Q is driven, and the ink is discharged from the return flow path 32 via the outlet 32y and returned to the ink tank 7. By circulating the ink between the head 1 and the ink tank 7 in this way, air bubbles in the ink are removed and the ink viscosity is prevented. Note that the thick arrows in Figure 2 indicate the flow of ink.

[0025] Each individual flow path 20 includes a nozzle 21, a pressure chamber 23, and two connecting flow paths 25. As shown in Figure 3, the nozzle 21 is composed of a through hole formed in the plate 11d and opens to the lower surface of the plate 11d. As shown in Figure 2, the pressure chamber 23 has a substantially rectangular planar shape that is elongated in the conveying direction. Also, as shown in Figure 3, the pressure chamber 23 has a substantially rectangular cross-sectional shape that is elongated in the conveying direction. A recess 11cx is formed on the lower surface of the plate 11c at a position opposite to the nozzle 21, and the pressure chamber 23 is defined by the recess 11cx and the plate 11d which is bonded to the lower surface of the plate 11c. In other words, the upper wall 23a of the pressure chamber 23 is formed by the thin-walled portion of the plate 11c (the portion whose thickness is reduced by the recess 11cx). On the other hand, the lower wall 23b of the pressure chamber 23 is formed by the plate 11d. Furthermore, the side walls 23c and 23d of the pressure chamber 23 are formed by the thickened portion of the plate 11c (the portion where the recess 11cx is not formed). As shown in Figure 3, the connecting channel 25 is composed of through holes formed in the plate 11b and the upper wall 23a of the pressure chamber 23. Recesses 11bx are formed on the lower surface of the plate 11b at positions facing each pressure chamber 23. The plate 11b is bonded to the upper surface of the plate 11c such that a plurality of piezoelectric elements 12, which will be described later, are housed within the recesses 11bx.

[0026] As shown in Figures 2 and 3, one end 231 and the other end 232 of the pressure chamber 23 constituting the second individual flow path 20b overlap vertically with the supply flow path 33 and the return flow path 32, respectively, in the direction of transport. An inlet 23x and an outlet 23y are formed in the upper wall 23a of the pressure chamber 23 constituting the second individual flow path 20b. Specifically, the inlet 23x is located on the side of the one end 231 of the pressure chamber 23 in the direction of transport, and the outlet 23y is located on the side of the other end 232 of the pressure chamber 23 in the direction of transport. The inlet 23x and the outlet 23y of the pressure chamber 23 constituting the second individual flow path 20b are connected to the supply flow path 33 and the return flow path 32, respectively, via a connecting flow path 25. Similarly, the other end and one end of the pressure chamber 23 constituting the first individual flow path 20a overlap vertically with the supply flow path 33 and the return flow path 31, respectively, in the direction of transport. Furthermore, the inlet 23x and outlet 23y of the pressure chamber 23 constituting the first individual flow path 20a are connected to the supply flow path 33 and the return flow path 31, respectively, via the connecting flow path 25.

[0027] In each individual flow path 20, one of the two connecting flow paths 25 extends upward from the pressure chamber 23 and is connected to the supply flow path 33. The other of the two connecting flow paths 25 extends upward from the pressure chamber 23 and is connected to the return flow path 31 or the return flow path 32. In each individual flow path 20, the nozzle 21 is positioned between one end and the other end of the pressure chamber 23 in the transport direction.

[0028] The ink supplied to the supply channel 33 moves downward through one of the connecting channels 25 and is supplied to the pressure chamber 23. The ink supplied to the pressure chamber 23 moves horizontally, some of which is ejected from the nozzle 21, and the remainder moves upward through the other connecting channel 25 and flows into the return channel 31 or the return channel 32. The arrows in Figure 3 indicate the flow of ink.

[0029] Multiple piezoelectric elements 12 are arranged on the upper surface of the plate 11c so as to face each of the multiple pressure chambers 23 formed in the plate 11c.

[0030] As shown in Figure 3, each piezoelectric element 12 includes, from bottom to top, a common electrode 12a, a piezoelectric layer 12b, and individual electrodes 12c. The common electrode 12a is made of a metallic material and is provided to be common to multiple pressure chambers 23. The piezoelectric layer 12b is formed by firing (annealing) a piezoelectric material mainly composed of, for example, lead zirconate titanate (PZT). The piezoelectric layer 12b is provided to be common to multiple pressure chambers 23 and covers the top and sides of the common electrode 12a. The individual electrodes 12c are made of a metallic material and have a substantially rectangular planar shape that is long in the transport direction. The individual electrodes 12c are provided for each pressure chamber 23 and are formed on the top surface of the piezoelectric layer 12b so as to face the pressure chamber 23.

[0031] Each individual electrode 12c is electrically connected to the driver IC 1d (see Figure 4) via individual wiring 13. The common electrode 12a is also electrically connected to the driver IC 1d via common wiring (not shown). The driver IC 1d maintains the potential of the common electrode 12a at ground potential while changing the potential of the individual electrodes 12c.

[0032] Here, when no voltage is applied to the individual electrodes 12c, the piezoelectric layer 12b deforms to become convex downward due to residual stress during firing, as shown in Figure 3. As a result, the upper wall 23a of the pressure chamber 23 and the common electrode 12a are curved so that, when viewed from the paper width direction, they are located at their lowest point near the center of the transport direction of the pressure chamber 23. Therefore, the upper surface 23a1 of the pressure chamber 23 is also curved so that it is located at its lowest point near the center of the transport direction. Specifically, when viewed from the paper width direction, the height from the lower surface 23b1 to the upper surface 23a1 of the pressure chamber 23 decreases continuously along the transport direction from the inlet 23x to the lowest protruding part 23z of the upper wall 23a of the pressure chamber (hereinafter referred to as the lowest part 23z), and increases continuously along the transport direction from the lowest part 23z to the outlet 23y.

[0033] The vertical displacement D of the lowest portion 23z from the uncurved portion of the upper wall 23a of the pressure chamber 23 (the portion where the piezoelectric element 12 is not formed) is, for example, about 200 to 800 nm. Tensile stress is generated in the piezoelectric layer 12b, and compressive stress is generated in the diaphragm 12a.

[0034] The nozzle 21 is located at the same position as the lowest part 23z in the transport direction. In other words, when viewed from the paper width direction, the nozzle 21 is positioned directly below the lowest part 23z.

[0035] Next, the operation of the piezoelectric element 12 when ejecting ink from a specific nozzle 21 will be described. First, when ink is not ejected from the nozzle 21 (standby state), the common electrode 12a is maintained at ground potential, and a predetermined voltage is applied to the individual electrode 12c corresponding to the pressure chamber 23 communicating with the nozzle 21. At this time, an electric field parallel to the polarization direction is generated in the piezoelectric layer 12b between the individual electrode 12c and the common electrode 12a. As a result, the piezoelectric layer 12b contracts in a horizontal direction perpendicular to the polarization direction and deforms to become convex toward the pressure chamber 23. Consequently, the common electrode 12a and the upper wall 23a of the pressure chamber 23 are curved to become even more convex downwards compared to the state when no predetermined voltage is applied to the individual electrode 12c. Specifically, the lowest part 23z is displaced downwards by, for example, about 0.5 to 1.5 μm below the uncurved part of the upper wall 23a of the pressure chamber 23 (the part where the piezoelectric element 12 is not formed). Here, as shown in Figure 3, the wiring 13 extends from the individual electrode 12c in the direction from the outlet 23y toward the inlet 23x. Therefore, the end of the piezoelectric layer 12b on the inlet 23x side is less prone to deformation compared to other parts. As a result, the downward displacement of the upper wall 23a of the pressure chamber 23 is greater near the outlet 23y than near the inlet 23x. Consequently, the lowest part 23z shifts from the center of the pressure chamber 23 toward the outlet 23y side in the transport direction. In other words, the lowest part 23z is located between the center of the pressure chamber 23 and the outlet 23y in the transport direction. In the standby state, as described above, the controller 5 drives the positive pressure pump 7P and the negative pressure pump 7Q to circulate ink between the head 1 and the ink tank 7. Therefore, an ink flow occurs within the pressure chamber 23 from the inlet 23x toward the outlet 23y.

[0036] Then, when ink is ejected from the nozzle 21, the potential of the individual electrode 12c corresponding to the pressure chamber 23 communicating with the nozzle 21 is first switched to the ground potential. As a result, the piezoelectric layer 12b between the individual electrode 12c and the common electrode 12a returns to the state it was in when no predetermined voltage was applied to the individual electrode 12c. Consequently, the amount of downward displacement of the upper wall 23a of the pressure chamber 23 becomes smaller than when a predetermined voltage is applied to the individual electrode 12c, and the volume of the pressure chamber 23 increases. Next, the predetermined voltage is applied to the individual electrode 12c again. At this time, the piezoelectric layer 12b between the individual electrode 12c and the common electrode 12a deforms again so as to become convex towards the pressure chamber 23. As a result, the amount of downward displacement of the upper wall 23a of the pressure chamber 23 becomes larger than when no predetermined voltage is applied to the individual electrode 12c, and the volume of the pressure chamber 23 decreases. This increases the ink pressure in the pressure chamber 23, and ink is ejected from the nozzle 21. Even when ejecting ink, the controller 5 drives the positive pressure pump 7P and the negative pressure pump 7Q to circulate the ink between the head 1 and the ink tank 7. Therefore, within the pressure chamber 23, an ink flow occurs from the inlet 23x towards the outlet 23y.

[0037] As described above, the upper wall 23a of the pressure chamber 23 is curved so as to be convex downward when viewed from the paper width direction, when no predetermined voltage is applied to the individual electrodes 12c. Air bubbles mixed in the ink in the pressure chamber 23 move toward the upper surface 23a1 of the pressure chamber 23. According to this embodiment, the upper surface 23a1 of the pressure chamber 23 is inclined upward from the lowest part 23z toward the outlet 23y. Therefore, air bubbles that reach the upper surface 23a1 of the pressure chamber 23 can be smoothly moved along the upper surface 23a1 to the outlet 23y. As a result, air bubbles mixed in the ink in the pressure chamber 23 can be efficiently discharged without increasing the flow rate of ink flowing through the pressure chamber 23.

[0038] In this embodiment, the inlet 23x and outlet 23y are formed on the upper wall 23a of the pressure chamber 23. Therefore, bubbles that mix with the ink in the pressure chamber 23 and move toward the upper surface 23a1 of the pressure chamber 23 can be efficiently discharged from the outlet 23y.

[0039] Furthermore, in this embodiment, the two connecting channels 25 connected to each pressure chamber 23 extend upward from the inlet 23x and outlet 23y, respectively. The two connecting channels 25 are then each connected to a common channel 30 located further above. As a result, air bubbles mixed in the ink within the pressure chamber 23 can be efficiently discharged into the common channel 30 via the outlet 23y and the connecting channels 25.

[0040] In this embodiment, when a voltage is applied to the individual electrodes 12c, the upper wall 23a of the pressure chamber 23 is deformed to be even more convex downward than when no voltage is applied to the individual electrodes 12c. Therefore, without increasing the flow rate of ink flowing through the pressure chamber 23, air bubbles mixed in the ink within the pressure chamber 23 can be efficiently moved toward the outlet 23y. As a result, air bubbles mixed in the ink within the pressure chamber 23 can be efficiently discharged.

[0041] In this embodiment, the lowest portion 23z of the upper wall 23a of the pressure chamber 23 is at the same position as the nozzle 21 in the transport direction. Air bubbles mixed into the ink in the pressure chamber 23 from the nozzle 21 move from the nozzle 21 towards the lowest portion 23z directly above it, but are carried further towards the outlet 23y side than the lowest portion 23z by the flow of ink in the pressure chamber 23. Therefore, according to this embodiment, air bubbles mixed into the ink in the pressure chamber 23 from the nozzle 21 can be reliably moved towards the outlet 23y side than the lowest portion 23z, and can be efficiently discharged from the outlet 23y.

[0042] In this embodiment, when viewed from the paper width direction, the height of the pressure chamber 23 from the lower surface 23b to the upper surface 23a is continuously increasing along the transport direction from the lowest part 23z to the outlet 23y. Therefore, air bubbles mixed into the nozzle in the pressure chamber 23 can be efficiently moved toward the outlet 23y. As a result, air bubbles mixed into the ink in the pressure chamber 23 can be efficiently discharged.

[0043] [Differentiation] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various design modifications are possible as long as they are within the scope of the claims.

[0044] In the above embodiment, the lowest portion 23z was at the same position as the nozzle 21 in the transport direction, but this is not limited to this. For example, the nozzle 21 may be positioned between the lowest portion 23z and the outlet 23y in the transport direction. In the above embodiment, as shown in Figure 3, the wiring 13 extends from the individual electrode 12c in the direction from the outlet 23y toward the inlet 23x, bypasses the connecting channel 25, and further extends along the transport direction. For this reason, the end of the piezoelectric layer 12b on the inlet 23x side is less prone to deformation than other parts. As a result, when a predetermined voltage is applied to the individual electrode 12c, the amount of downward displacement of the upper wall 23a of the pressure chamber 23 is slightly greater near the outlet 23y than near the inlet 23x. In other words, the lowest portion 23z is shifted from the center of the pressure chamber 23 toward the outlet 23y side in the transport direction. Therefore, the position of the nozzle 21 in the transport direction may be the same as the lowest part 23z when a predetermined voltage is applied to the individual electrodes 12c, or, as shown in head 1A in Figure 5, it may be between the lowest part 23z and the outlet 23y when a predetermined voltage is applied to the individual electrodes 12c. This makes it possible to easily move air bubbles mixed in the ink in the pressure chamber 23 from the nozzle 21 to the outlet 23y, regardless of whether a predetermined voltage is applied to the individual electrodes 12c.

[0045] In the above embodiment, the inlet 23x and outlet 23y were formed on the upper wall 23a of the pressure chamber 23, but this is not limited to this. For example, as shown in head 1B in Figure 6, the inlet 23x and outlet 23y may be formed on the upper end of the side wall 23c on one side in the conveying direction and the upper end of the side wall 23d on the other side of the pressure chamber 23, respectively. In this case as well, air bubbles mixed in the ink in the pressure chamber 23 can be efficiently discharged. In this case, the connecting passage 25 connected to the inlet 23x and the supply passage 33 communicating with the pressure chamber 23 via the connecting passage 25, and the connecting passage 25 connected to the outlet 23y and the return passages 31, 32 communicating with the pressure chamber 23 via the connecting passage 25 may be formed on the plate 11c.

[0046] In the above embodiment, the positive pressure pump 7P and the negative pressure pump 7Q may be set such that the absolute value of the positive pressure from the positive pressure pump 7P is smaller than the absolute value of the negative pressure from the negative pressure pump 7Q. This allows the pressure chamber 23 to be kept under negative pressure, and the upper wall 23a of the pressure chamber 23 to be easily curved so that it is convex downwards.

[0047] In the above embodiment, one supply channel 33 was sandwiched in the transport direction by two return channels 31 and 32, but this is not limited to this configuration. For example, one return channel may be sandwiched in the transport direction by two supply channels.

[0048] The head unit 1x is not limited to a line type, but may also be a serial type (a system in which liquid is ejected from the nozzle to the target object while moving in a scanning direction parallel to the paper width direction).

[0049] The material to be ejected is not limited to paper; it may also be cloth, a circuit board, or the like.

[0050] The liquid discharged from the nozzle is not limited to ink, but may be any liquid (for example, a processing liquid that causes components in the ink to coagulate or precipitate).

[0051] The present invention is not limited to printers, but can also be applied to facsimile machines, copiers, multifunction devices, etc. Furthermore, the present invention can also be applied to liquid ejection heads used for purposes other than image recording (for example, liquid ejection heads that eject conductive liquid onto a substrate to form a conductive pattern). [Explanation of Symbols]

[0052] 1 head 5 Controllers 7 Ink Tanks 7P positive pressure pump 7Q Vacuum Pump 12 Piezoelectric element 20 individual channels 21 nozzles 23 Pressure chamber 23x inlet 23y outlet 25 Connecting channel 30 Common channel 31,32 Feedback channel 31y,32y outlet 33 Supply channel 33x supply ports 100 Printers

Claims

1. A liquid dispensing head, A first substrate having a lower surface from which a nozzle opens and a pressure chamber having a pressure chamber in communication with the nozzle, The upper surface of the first substrate is provided with a piezoelectric element arranged to face the pressure chamber, The pressure chamber extends in a first direction parallel to the lower surface of the first substrate, has a liquid inlet at one end in the first direction, and has a liquid outlet at the other end in the first direction. The nozzle is positioned between the inlet and the outlet in the first direction, When viewed from a second direction parallel to the lower surface of the first substrate and perpendicular to the first direction, the upper wall of the pressure chamber is curved so as to be convex downward when no voltage is applied to the piezoelectric element. A liquid discharge head characterized in that the vertical displacement of the lowest portion of the upper wall of the pressure chamber, which protrudes the most downward, from the non-curved portion of the upper wall of the pressure chamber is 200 to 800 nm.

2. The liquid discharge head according to claim 1, wherein the inlet and outlet are formed in the upper wall of the pressure chamber.

3. The second substrate further comprises a supply channel through which the liquid supplied to the pressure chamber flows, a first connecting channel connecting the supply channel and the inlet, a return channel through which the liquid discharged from the pressure chamber flows, a second connecting channel connecting the return channel and the outlet, and a recess. The liquid dispensing head according to claim 2, wherein the second substrate is laminated on the upper surface of the first substrate such that the piezoelectric element is housed in the recess of the second substrate.

4. The pressure chamber has a first side wall on one end and a second side wall on the other end, The inlet is formed at the upper end of the first side wall, The liquid discharge head according to claim 1, wherein the outlet is formed at the upper end of the second side wall.

5. The liquid discharge head according to claim 4, wherein the first substrate further comprises a supply channel connected to the inlet through which the liquid supplied to the pressure chamber flows, and a return channel connected to the outlet through which the liquid discharged from the pressure chamber flows.

6. The liquid discharge head according to any one of claims 1 to 5, wherein, when viewed from the second direction, the upper wall of the pressure chamber deforms to be more convex downward when a voltage is applied to the piezoelectric element than when no voltage is applied to the piezoelectric element.

7. The liquid discharge head according to claim 1, wherein, when viewed from the second direction, the nozzle is positioned in the same location as the lowest protruding portion of the upper wall of the pressure chamber in the first direction, or between the lowest protruding portion of the upper wall of the pressure chamber and the outlet.

8. The liquid discharge head according to claim 1, wherein, when viewed from the second direction, the nozzle is positioned at the same location as the portion of the upper wall of the pressure chamber that protrudes most downward in the first direction.

9. The liquid discharge head according to claim 2, wherein, when viewed from the second direction, the height from the lower surface to the upper surface of the pressure chamber increases continuously from the lowest protruding portion of the upper wall of the pressure chamber toward the outlet.

10. The piezoelectric element comprises a first electrode disposed on the upper surface of the first substrate, a piezoelectric layer disposed on the upper surface of the first electrode so as to face the pressure chamber, and a second electrode disposed on the upper surface of the piezoelectric layer so as to face the pressure chamber. The liquid discharge head according to claim 1, wherein, when no voltage is applied to the piezoelectric element, tensile stress is generated in the piezoelectric layer and compressive stress is generated in the upper wall of the pressure chamber.

11. A liquid dispensing system, A first substrate having a lower surface from which a nozzle opens and a pressure chamber having a pressure chamber in communication with the nozzle, On the upper surface of the first substrate, a piezoelectric element is arranged so as to face the pressure chamber, A supply channel through which liquid supplied to the pressure chamber flows, a return channel through which the liquid discharged from the pressure chamber flows, and a recess are formed, and a second substrate is laminated on the upper surface of the first substrate so that the piezoelectric element is housed in the recess, A tank for storing the aforementioned liquid, A positive pressure pump connected to the tank and the supply channel, The system comprises the aforementioned return channel and a negative pressure pump connected to the tank, The pressure chamber extends in a first direction parallel to the lower surface of the first substrate, has a liquid inlet at one end in the first direction, and has a liquid outlet at the other end in the first direction. The nozzle is positioned between the inlet and the outlet in the first direction, When viewed from a second direction parallel to the lower surface of the first substrate and perpendicular to the first direction, the upper wall of the pressure chamber is curved so as to be convex downward when no voltage is applied to the piezoelectric element. The vertical displacement of the lowest protruding portion of the upper wall of the pressure chamber from the uncurved portion of the upper wall of the pressure chamber is 200 to 800 nm. The inlet and outlet are formed in the upper wall of the pressure chamber. The second substrate further has a first connecting channel that connects the supply channel and the inlet, and a second connecting channel that connects the return channel and the outlet. The liquid discharge system wherein the pressure chamber is maintained at a negative pressure when no voltage is applied to the piezoelectric element.

12. A liquid dispensing system, A first substrate having a lower surface through which a nozzle opens, a pressure chamber communicating with the nozzle, a supply channel through which liquid supplied to the pressure chamber flows, and a return channel through which the liquid discharged from the pressure chamber flows, On the upper surface of the first substrate, a piezoelectric element is arranged so as to face the pressure chamber, A tank for storing the aforementioned liquid, A positive pressure pump connected to the tank and the supply channel, The system comprises the aforementioned return channel and a negative pressure pump connected to the tank, The pressure chamber extends in a first direction parallel to the lower surface of the first substrate, and has a first side wall at one end in the first direction and a second side wall at the other end in the first direction. An inlet for the liquid is formed at the upper end of the first side wall of the pressure chamber. An outlet for the liquid is formed at the upper end of the second side wall of the pressure chamber. The nozzle is positioned between the inlet and the outlet in the first direction, When viewed from a second direction parallel to the lower surface of the first substrate and perpendicular to the first direction, the upper wall of the pressure chamber is curved so as to be convex downward when no voltage is applied to the piezoelectric element. The vertical displacement of the lowest protruding portion of the upper wall of the pressure chamber from the uncurved portion of the upper wall of the pressure chamber is 200 to 800 nm. The first substrate further has a first connecting channel that connects the supply channel and the inlet, and a second connecting channel that connects the return channel and the outlet. The liquid discharge system wherein the pressure chamber is maintained at a negative pressure when no voltage is applied to the piezoelectric element.

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