Liquid discharge head

Abstract

To enhance rigidity of the whole liquid discharge head, compared to a conventional liquid discharge head.SOLUTION: A liquid discharge head 1 has a piezoelectric element 34, a nozzle substrate 41 provided with nozzles N, a communication plate 31 which is positioned on the upper part of the nozzle substrate 41, and is provided with a communication flow channel 314 communicating with the nozzle N, a pressure chamber substrate 32 which is positioned on the upper part of the communication plate 31, and is provided with a pressure chamber C that communicates with the communication flow channel 314 and imparts a pressure to liquid, and a sealing plate 35 which is positioned on the upper part of the pressure chamber substrate 32 and has a recess 350 for sealing a space where the piezoelectric element 34 is arranged, wherein the ratio of the thickness of the sealing plate 35 to the total of the thicknesses of the nozzle substrate 41, the communication plate 31, the pressure chamber substrate 32 and the sealing plate 35 is 50% or more.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] Conventionally, a liquid ejection head provided in a liquid ejection device that ejects a liquid such as ink is known.

[0003] For example, Patent Document 1 discloses a liquid ejection head including a nozzle substrate provided with nozzles for ejecting a liquid, a communication plate provided with communication channels through which the liquid flows, a pressure chamber substrate provided with pressure chambers that communicate with the communication channels and apply pressure to the liquid, and a sealing plate provided with recesses in which piezoelectric elements are arranged.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the liquid ejection head disclosed in Patent Document 1, when emphasizing miniaturization, it is conceivable to make the thickness of each member constituting the liquid ejection head as thin as possible. However, the thinner the thickness of each member, the lower the rigidity of the entire liquid ejection head.

Means for Solving the Problems

[0006] A liquid ejection head according to one aspect of the present invention includes a piezoelectric element, a nozzle substrate provided with nozzles, a communication plate located above the nozzle substrate and provided with a communication flow path communicating with the nozzles, a pressure chamber substrate located above the communication plate and provided with a pressure chamber communicating with the communication flow path and applying pressure to a liquid, and a sealing plate located above the pressure chamber substrate and provided with a recess for sealing a space in which the piezoelectric element is disposed. In the liquid ejection head, a ratio of the thickness of the sealing plate to a total thickness of the nozzle substrate, the communication plate, the pressure chamber substrate, and the sealing plate is 50% or more.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0008] 1: First Embodiment Hereinafter, a liquid ejection device 100 according to a first embodiment will be described with reference to FIGS. 1 to 5.

[0009] 1-1: Outline of Liquid Ejection Device FIG. 1 is a configuration diagram illustrating a liquid ejection device 100 according to a first embodiment.

[0010] The liquid ejection device 100 is an inkjet printing device that ejects ink onto the medium 12. The medium 12 is typically printing paper, but any printing target such as a resin film or fabric can be used as the medium 12. Note that ink is an example of a "liquid".

[0011] The liquid ejection device 100 includes a liquid container 14 that stores ink. As the liquid container 14, for example, a cartridge that is detachable from the liquid ejection device 100, a bag-shaped ink pack formed of a flexible film, or an ink tank that can be refilled with ink can be adopted. A plurality of types of inks with different colors are stored in the liquid container 14.

[0012] The liquid ejection device 100 includes a plurality of liquid ejection heads 1, a control unit 20, a conveyance mechanism 22, and a movement mechanism 24.

[0013] The control unit 20 includes a processing circuit such as a CPU or an 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.

[0014] The conveyance mechanism 22 conveys the medium 12 in the Y1 direction along the Y axis under the control of the control unit 20. Hereinafter, the Y1 direction and the Y2 direction opposite to the Y1 direction are collectively referred to as the Y-axis direction. Also, hereinafter, the X1 direction along the X axis intersecting the Y axis and the X2 direction opposite to the X1 direction are collectively referred to as the X-axis direction. Also, hereinafter, the Z1 direction along the Z axis intersecting the X axis and the Y axis and the Z2 direction opposite to the Z1 direction are collectively referred to as the Z-axis direction. In the present embodiment, as an example, a case where the X axis, the Y axis, and the Z axis are orthogonal to each other will be assumed for explanation. However, the present invention is not limited to such a mode. The X axis, the Y axis, and the Z axis only need to intersect each other. In this embodiment, the Z2 direction is defined as "up" and the Z1 direction is defined as "down". In this specification, the expression "element B is disposed above element A" does not limit the configuration to one in which element A and element B are in direct contact. A configuration in which element A and element B are not in direct contact is also included in the concept of "element B is disposed above element A".

[0015] The moving mechanism 24 reciprocates the plurality of liquid ejection heads 1 in the X1 direction and the X2 direction under the control of the control unit 20. The moving mechanism 24 includes a storage case 242 that houses the plurality of liquid ejection heads 1 and an endless belt 244 to which the storage case 242 is fixed. Note that the liquid container 14 may be housed in the storage case 242 together with the liquid ejection head 1.

[0016] 1-2: Outline of Liquid Ejection Head Hereinafter, the outline of the liquid ejection head 1 will be described with reference to FIGS. 2 and 3.

[0017] FIG. 2 is an exploded perspective view of the liquid ejection head 1, and FIG. 3 is a cross-sectional view taken along line a-a in FIG. 2.

[0018] As shown in FIGS. 2 and 3, the liquid ejection head 1 includes a flow path structure 30, a plurality of piezoelectric elements 34, a sealing plate 35, a housing portion 36, and a wiring board 51. The flow path structure 30 is a structure in which flow paths for supplying ink to each of the plurality of nozzles N are formed inside. The flow path structure 30 is composed of a communication plate 31, a pressure chamber substrate 32, a diaphragm 33, a nozzle substrate 41, and a vibration absorber 42. The diaphragm 33 and the plurality of piezoelectric elements 34 constitute an actuator 3. Each member constituting the flow path structure 30 is a long plate-like member along the Y axis. The pressure chamber substrate 32 and the housing portion 36 are disposed on the surface of the communication plate 31 on the Z2 side. On the other hand, the nozzle substrate 41 and the vibration absorber 42 are disposed on the surface of the communication plate 31 on the Z1 side. Each member is fixed by, for example, an adhesive.

[0019] As shown in FIG. 2, the nozzle substrate 41 is a plate-shaped member that is long in the Y-axis direction and extends substantially parallel to the XY plane. Here, "substantially parallel" is a concept that includes cases where, in addition to being completely parallel, it can be regarded as parallel considering errors. In the present embodiment, "substantially parallel" is a concept that includes cases where it can be regarded as parallel considering an error of about 10%. The nozzle substrate 41 is manufactured, for example, by processing a single-crystalline silicon substrate using semiconductor manufacturing techniques such as etching, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the nozzle substrate 41.

[0020] A plurality of nozzles N are formed in the nozzle substrate 41. Here, the nozzle N is a through-hole provided in the nozzle substrate 41. In the present embodiment, it is assumed that the plurality of nozzles N formed in the nozzle substrate 41 include a plurality of nozzles N1 arranged to extend in the Y-axis direction and a plurality of nozzles N2 arranged to extend in the Y-axis direction at positions in the X2 direction as viewed from the plurality of nozzles N1. Hereinafter, the plurality of nozzles N1 extending in the Y-axis direction are referred to as a nozzle row Ln1, and the plurality of nozzles N2 extending in the Y-axis direction are referred to as a nozzle row Ln2. Further, hereinafter, the nozzle row Ln1 and the nozzle row Ln2 may be collectively referred to as a nozzle row Ln.

[0021] As shown in FIGS. 2 and 3, a communication plate 31 is provided at a position in the Z2 direction as viewed from the nozzle substrate 41. The communication plate 31 is a plate-shaped member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The communication plate 31 is manufactured, for example, by processing a single-crystalline silicon substrate using semiconductor manufacturing techniques, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the communication plate 31.

[0022] As illustrated in FIGS. 2 and 3, a communication plate 31 is formed with a space Ra, a plurality of supply channels 312, a plurality of communication channels 314, and a relay liquid chamber 316. The space Ra is an opening formed in a long shape along the Y-axis. Each of the supply channels 312 and the communication channels 314 is a through-hole formed for each nozzle N. The relay liquid chamber 316 is a space formed in a long shape along the Y-axis across a plurality of nozzles N. The relay liquid chamber 316 communicates the space Ra and the plurality of supply channels 312 with each other. Each of the plurality of communication channels 314 overlaps with one nozzle N corresponding to the communication channel 314 in a plan view seen in the Z-axis direction.

[0023] As shown in FIGS. 2 and 3, a pressure chamber substrate 32 is provided at a position in the Z2 direction as viewed from the communication plate 31. The pressure chamber substrate 32 is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The pressure chamber substrate 32 is manufactured, for example, by processing a single-crystalline silicon substrate using semiconductor manufacturing technology, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the pressure chamber substrate 32.

[0024] As illustrated in FIGS. 2 and 3, the pressure chamber substrate 32 is provided with a plurality of pressure chambers C1 and a plurality of pressure chambers C2. Each of the pressure chambers C1 and the pressure chambers C2 is formed by a wall surface 320 of the pressure chamber substrate 32 and is a space that is long in a plan view along the X-axis. Each of the pressure chambers C1 and the pressure chambers C2 is a space located between the communication plate 31 and the diaphragm 33. The pressure chamber C1 is formed for each nozzle N1. The pressure chamber C2 is formed for each nozzle N2. As illustrated in FIG. 2, the plurality of pressure chambers C1 are arranged along the Y-axis. Similarly, the plurality of pressure chambers C2 are arranged along the Y-axis. As illustrated in FIGS. 2 and 3, each of the pressure chambers C1 and the pressure chambers C2 communicates with the communication channels 314 and the supply channels 312. Therefore, the pressure chamber C1 communicates with the nozzle N1 through the communication channel 314 and communicates with the space Ra through the supply channel 312 and the relay liquid chamber 316. Similarly, the pressure chamber C2 communicates with the nozzle N2 through the communication channel 314 and communicates with the space Ra through the supply channel 312 and the relay liquid chamber 316. Hereinafter, the pressure chambers C1 and the pressure chambers C2 may be collectively referred to as the pressure chamber C.

[0025] As shown in FIGS. 2 and 3, a diaphragm 33 is provided at a position in the Z2 direction as viewed from the pressure chamber substrate 32. The diaphragm 33 is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane. Further, the diaphragm 33 is a member that can vibrate elastically. Part or all of the diaphragm 33 may be a separate member from the pressure chamber substrate 32 or may be integral.

[0026] As illustrated in FIGS. 2 and 3, piezoelectric elements 34 are formed on each of the surfaces of the diaphragm 33 on the side opposite to the pressure chamber C1 and on the side opposite to the pressure chamber C2. One piezoelectric element 34 is provided corresponding to one pressure chamber C1 or one pressure chamber C2. The piezoelectric element 34 is a long passive element along the X-axis in plan view. The piezoelectric element 34 generates a pressure for discharging ink. That is, the piezoelectric element 34 varies the pressure of the ink in the pressure chamber C1 or the pressure chamber C2.

[0027] As illustrated in FIG. 2, the plurality of piezoelectric elements 34 are divided into a first piezoelectric element row Lp1 and a second piezoelectric element row Lp2 that are arranged side by side at intervals along the X-axis. Each of the first piezoelectric element row Lp1 and the second piezoelectric element row Lp2 is a set of a plurality of piezoelectric elements 34 linearly arranged along the Y-axis. The second piezoelectric element row Lp2 is provided at a different position in a crossing direction that crosses the first piezoelectric element row Lp1 in a predetermined direction. The predetermined direction is a direction along the Y-axis and is the direction in which the plurality of piezoelectric elements 34 included in the first piezoelectric element row Lp1 are arranged. It should be noted that the predetermined direction can also be said to be the direction in which the plurality of piezoelectric elements 34 included in the second piezoelectric element row Lp2 are arranged. The crossing direction is a direction along the X-axis and is the direction in which the first piezoelectric element row Lp1 and the second piezoelectric element row Lp2 are arranged. The first piezoelectric element row Lp1 corresponds to the nozzle row Ln1. Further, the second piezoelectric element row Lp2 corresponds to the nozzle row Ln2.

[0028] As shown in FIGS. 2 and 3, a sealing plate 35 for protecting a plurality of piezoelectric elements 34 is provided at a position in the Z2 direction as viewed from the piezoelectric elements 34. The sealing plate 35 seals the piezoelectric elements 34. The sealing plate 35 is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The sealing plate 35 is manufactured, for example, by processing a single crystal silicon substrate using semiconductor manufacturing technology, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the sealing plate 35.

[0029] The sealing plate 35 protects a plurality of piezoelectric elements 34 and reinforces the mechanical strength of the pressure chamber substrate 32 and the diaphragm 33. Further, a recess 350 for covering a part of each of the plurality of piezoelectric elements 34 is provided on the surface in the Z1 direction among the two surfaces of the sealing plate 35 having the Z-axis direction as the normal direction. The recess 350 allows displacement due to the vibration of the piezoelectric element 34. Further, the recess 350 seals the space in which the piezoelectric elements 34 are arranged, and prevents the piezoelectric elements 34 from deteriorating due to the influence of moisture or the like.

[0030] A wiring substrate 51 is joined to the surface of the diaphragm 33. The wiring substrate 51 is a mounting component on which a plurality of wirings for electrically connecting the control unit 20 and the liquid ejection head 1 are formed. For example, a flexible wiring substrate 51 such as an FPC (Flexible Printed Circuit) or an FFC (Flexible Flat Cable) is preferably adopted. A drive signal and a reference voltage for driving the piezoelectric elements 34 are supplied from the wiring substrate 51 to each piezoelectric element 34.

[0031] As shown in FIGS. 2 and 3, a housing portion 36 is provided at a position in the Z2 direction as viewed from the communication plate 31. The housing portion 36 is a plate-like member that is long in the Y-axis direction and extends substantially parallel to the XY plane. The housing portion 36 is formed, for example, by injection molding of a resin material, but known materials and manufacturing methods may be arbitrarily adopted for the manufacture of the housing portion 36.

[0032] The housing portion 36 is a case for storing ink supplied to the plurality of pressure chambers C. A space Rb and a supply port 361 are formed in the housing portion 36. The supply port 361 is a pipeline through which ink is supplied from the liquid container 14 and communicates with the space Rb. The space Rb in the housing portion 36 and the space Ra in the communication plate 31 communicate with each other. The space composed of the space Ra and the space Rb functions as a liquid storage chamber R for storing ink supplied to the plurality of pressure chambers C. The ink supplied from the liquid container 14 and passing through the supply port 361 is stored in the liquid storage chamber R. The ink stored in the liquid storage chamber R branches from the relay liquid chamber 316 to each supply flow path 312 and is supplied and filled in the plurality of pressure chambers C in parallel.

[0033] The vibration absorber 42 is a flexible film or plate that constitutes the wall surface of the liquid storage chamber R and absorbs pressure fluctuations of the ink in the liquid storage chamber R.

[0034] 1-3: Configuration near the pressure chamber FIG. 4 is a configuration diagram of the vicinity of the pressure chamber C1 provided in the liquid ejection head 1 according to the first embodiment. As described above, the sealing plate 35, the piezoelectric element 34, the diaphragm 33, the pressure chamber substrate 32, the communication plate 31, and the nozzle substrate 41 are laminated in the Z-axis direction from the Z2 side to the Z1 side. Also, a pressure chamber C1 is formed in the pressure chamber substrate 32.

[0035] When the thickness of the sealing plate 35 in the Z-axis direction is L1, the thickness of the pressure chamber substrate 32 in the Z-axis direction is L2, the thickness of the communication plate 31 in the Z-axis direction is L3, and the thickness of the nozzle substrate 41 in the Z-axis direction is L4, in the liquid ejection head 1 according to the present embodiment, the value of the thickness L1 is 50% or more of the total value of the thickness L1, the thickness L2, the thickness L3, and the thickness L4. It is still better if the value of the thickness L1 is 55% or more of the total value of the thickness L1, the thickness L2, the thickness L3, and the thickness L4. Also, the value of the thickness L1 may be 70% or less of the total value of the thickness L1, the thickness L2, the thickness L3, and the thickness L4. However, it is not necessary to provide an upper limit to the ratio of the value of the thickness L1 to the total value of the thickness L1, the thickness L2, the thickness L3, and the thickness L4. More precisely, it is more accurate to add the thickness of the diaphragm 33 and the thickness of the piezoelectric element 34 to the total value of the thickness l1, the thickness L2, the thickness L3, and the thickness L4 and calculate the ratio of the thickness L1 to that. However, since the diaphragm 33 and the piezoelectric element 34 are extremely thin compared to other members, they are within a range that can be sufficiently ignored.

[0036] For example, when the thickness L2 = 70 μm (microns), the thickness L3 = 400 μm, and the thickness L4 = 65 μm, the thickness L1 is 535 μm or more. Also, in this case, it is still better if the thickness L1 is 654 μm or more. As an example, the thickness L1 is 725 μm.

[0037] FIG. 5 is a configuration diagram in the vicinity of the pressure chamber C1 provided in the liquid ejection head 5 according to the comparative example. Also in the liquid ejection head 5 according to the comparative example, similar to the liquid ejection head 1, the sealing plate 35, the piezoelectric element 34, the diaphragm 33, the pressure chamber substrate 32, the communication plate 31, and the nozzle substrate 41 are laminated from the Z2 side to the Z1 side in the Z-axis direction. Also, a pressure chamber C1 is formed in the pressure chamber substrate 32.

[0038] In the liquid ejection head 5, when the thickness of the sealing plate 35 in the Z-axis direction is Z1, the thickness of the pressure chamber substrate 32 in the Z-axis direction is L2, the thickness of the communication plate 31 in the Z-axis direction is L3, and the thickness of the nozzle substrate 41 in the Z-axis direction is L4, the value of the thickness Z1 is less than 50% of the total value of the thickness Z1, the thickness L2, the thickness L3, and the thickness L4. For example, when the thickness L2 = 70 μm, the thickness L3 = 400 μm, and the thickness L4 = 65 μm, the thickness Z1 is less than 535 μm. As an example, the thickness Z1 is 400 μm.

[0039] The assembly of the sealing plate 35, the piezoelectric element 34, the diaphragm 33, the pressure chamber substrate 32, the communication plate 31, and the nozzle substrate 41 will hereinafter be referred to as the "actuator assembly". The actuator assembly according to the comparative example has a thinner sealing plate 35 compared to the actuator assembly according to the present embodiment. For this reason, the actuator assembly according to the comparative example has lower rigidity compared to the actuator assembly according to the present embodiment. The lower the rigidity of the actuator assembly, the more likely the shapes of the diaphragm 33, the plurality of pressure chambers C1, and the plurality of pressure chambers C2 will be deformed as a result of stress being applied to the actuator assembly from the outside or inside of the actuator assembly during the manufacture of the actuator assembly. For this reason, the lower the rigidity of the actuator assembly, the more likely it is that variations will occur in the ejection characteristics for each nozzle N. Further, during the manufacture of the actuator assembly, the actuator assembly is heated, but the lower the rigidity of the actuator assembly, the more likely it is that warping will occur in the actuator assembly. The higher the degree of warping that occurs in the entire actuator assembly, the higher the degree of warping that occurs in the nozzle substrate 41. As a result, the degree to which the ejection direction of the ink in each individual nozzle N deviates from the original direction also increases, and the accuracy of the landing position decreases.

[0040] In order to solve the above problems, it is preferable to increase the rigidity of the actuator assembly. In order to increase the rigidity of the actuator assembly, it is conceivable to increase the thickness of each member constituting the actuator assembly. However, when the thickness of the pressure chamber substrate 32 is increased, the volume of the pressure chamber C1 or the pressure chamber C2 increases, resulting in the actual discharge amount deviating from the desired discharge amount. Further, when the thicknesses of the communication plate 31 and the nozzle substrate 41 are increased, the flow path resistance increases.

[0041] In the liquid discharge head 1 according to the present embodiment, by increasing the thickness of the sealing plate 35 as compared with the liquid discharge head 5 related to the proportionality, while avoiding the above problems, it is possible to increase the rigidity of the actuator assembly and thus the rigidity of the entire liquid discharge head 1.

[0042] 1-4: Effects achieved by this embodiment The liquid discharge head 1 according to the present embodiment includes a piezoelectric element 34, a nozzle substrate 41, a communication plate 31, a pressure chamber substrate 32, and a sealing plate 35. The nozzle substrate 41 is provided with nozzles N for discharging ink. The communication plate 31 is located above the nozzle substrate 41. The communication plate 31 is provided with communication flow paths 314 communicating with the nozzles N. The pressure chamber substrate 32 is located above the communication plate 31. The pressure chamber substrate 32 is provided with pressure chambers C communicating with the communication flow paths 314 and applying pressure to the ink. The sealing plate 35 is located above the pressure chamber substrate 32. The pressure chamber substrate 32 is provided with a recess 350 for sealing the space in which the piezoelectric element 34 is disposed. The ratio of the thickness of the sealing plate 35 to the total thickness of the nozzle substrate 41, the communication plate 31, the pressure chamber substrate 32, and the sealing plate 35 is 50% or more.

[0043] Since the liquid discharge head 1 has the above configuration, its rigidity is higher than that of a conventional liquid discharge head in which the nozzle substrate 41, the communication plate 31, and the pressure chamber substrate 32 have the same dimensions. Specifically, by making the thickness of the sealing plate 35 provided in the liquid discharge head 1 thicker than the thickness of the sealing plate provided in the conventional liquid discharge head, the rigidity of the liquid discharge head 1 becomes higher than the rigidity of the conventional liquid discharge head.

[0044] Further, in the liquid ejection head 1 according to the present embodiment, the ratio of the thickness of the sealing plate 35 to the total thickness of the nozzle substrate 41, the communication plate 31, the pressure chamber substrate 32, and the sealing plate 35 may be 55% or more.

[0045] Since the liquid ejection head 1 has the above configuration, its rigidity is further increased as compared with a conventional liquid ejection head.

[0046] Further, in the liquid ejection head 1 according to the present embodiment, the ratio of the thickness of the sealing plate 35 to the total thickness of the nozzle substrate 41, the communication plate 31, the pressure chamber substrate 32, and the sealing plate 35 may be 70% or less.

[0047] Since the liquid ejection head 1 has the above configuration, while increasing the rigidity by increasing the thickness of the sealing plate 35 as compared with a conventional liquid ejection head, the thicknesses of the nozzle substrate 41, the communication plate 31, and the pressure chamber substrate 32 can be ensured.

[0048] 2: Modification The above embodiments can be variously modified. Specific modification modes are exemplified below. The modes exemplified below and the modes shown in the above embodiments can be appropriately combined within a range not conflicting with each other. In the modification examples exemplified below, for elements whose actions and functions are equivalent to those of the embodiments, the reference numerals referred to in the above description are used, and the detailed descriptions thereof are appropriately omitted.

[0049] 2-1: Modification 1 FIG. 6 is a configuration diagram near the pressure chamber C1 provided in the liquid ejection head 1A according to Modification 1. In the liquid ejection head 1 according to the first embodiment, the sealing plate 35 made of a single member is laminated on the Z2 side of the piezoelectric element 34. On the other hand, in the liquid ejection head 1A according to the present modification, the sealing plate 35A is laminated on the Z2 side of the piezoelectric element 34, and the sealing plate 35B is laminated on the Z2 side of the sealing plate 35A. In other words, in the present modification, the sealing plate 35 having two sealing plates, the sealing plate 35A and the sealing plate 35B, is laminated on the Z2 side of the piezoelectric element 34.

[0050] As shown in FIG. 6, the sealing plate 35A has a recess 350, similar to the sealing plate 35 in the first embodiment. On the other hand, the sealing plate 35B is different from the sealing plate 35 in the first embodiment and does not have a recess 350.

[0051] In this modification, when the thickness of the sealing plate 35A is L11 and the thickness of the sealing plate 35B is L12, the value of the thickness L1 of the sealing plate 35 is the sum of the value of the thickness L11 and the value of the thickness L12. Also in this modification, the value of the thickness L11 and the value of the thickness L12 are equal.

[0052] Similar to the first embodiment, the value of the thickness L1 is 50% or more of the sum of the thicknesses L1, L2, L3, and L4. It is even better if the value of the thickness L1 is 55% or more of the sum of the thicknesses L1, L2, L3, and L4. Also, the value of the thickness L1 may be 70% or less of the sum of the thicknesses L1, L2, L3, and L4. However, it is not necessary to set an upper limit on the ratio of the value of the thickness L1 to the sum of the thicknesses L1, L2, L3, and L4.

[0053] Since the value of the thickness L11 and the value of the thickness L12 are equal, each of the value of the thickness L11 and the value of the thickness L12 is 25% or more of the sum of the thicknesses L1, L2, L3, and L4. It is even better if each of the value of the thickness L11 and the value of the thickness L12 is 27.5% or more of the sum of the thicknesses L1, L2, L3, and L4. Also, each of the value of the thickness L11 and the value of the thickness L12 may be 35% or less of the sum of the thicknesses L1, L2, L3, and L4. However, it is not necessary to set an upper limit on the ratio of each of the value of the thickness L11 and the value of the thickness L12 to the sum of the thicknesses L1, L2, L3, and L4.

[0054] For example, when the thickness L2 = 70 μm, the thickness L3 = 400 μm, and the thickness L4 = 65 μm, each of the thicknesses L11 and L12 is 267.5 μm or more. Also, in this case, it is even better if each of the thicknesses L11 and L12 is 327.5 μm or more. As an example, each of the thicknesses L11 and L12 is 400 μm.

[0055] When each of the thicknesses L11 and L12 is 400 μm, as each of the sealing plates 35A and 35B, it is possible to directly use them without changing the thickness of a widely used single-crystal silicon substrate. As a result, the manufacturing of the liquid ejection head 1A according to the first modified example becomes easy.

[0056] 2-2: Second Modified Example FIG. 7 is a configuration diagram near the pressure chamber C1 provided in the liquid ejection head 1B according to the second modified example. In the liquid ejection head 1B according to this modified example, similar to the liquid ejection head 1A according to the first modified example, the sealing plate 35A is laminated on the Z2 side of the piezoelectric element 34, and the sealing plate 35B is laminated on the Z2 side of the sealing plate 35A. In other words, also in this modified example, on the Z2 side of the piezoelectric element 34, the sealing plate 35 having two sealing plates, the sealing plate 35A and the sealing plate 35B, is laminated.

[0057] However, in the liquid ejection head 1A according to the first modified example, the thickness L11 of the sealing plate 35A and the thickness L12 of the sealing plate 35B were equal. On the other hand, in the liquid ejection head 1B according to the second modified example, the thickness L11 of the sealing plate 35A and the thickness L12 of the sealing plate 35B are different from each other. Note that the value of L12 may be larger than the value of L11, or the value of L11 may be larger than the value of L12.

[0058] Also in this modification, similar to Modification 1, each of the value of thickness L11 and the value of thickness L12 is 25% or more of the total value of thicknesses L1, L2, L3, and L4. It is still better if each of the value of thickness L11 and the value of thickness L12 is 27.5% or more of the total value of thicknesses L1, L2, L3, and L4. Also, each of the value of thickness L11 and the value of thickness L12 may be 35% or less of the total value of thicknesses L1, L2, L3, and L4. However, an upper limit may not be provided for the ratio that each of the value of thickness L11 and the value of thickness L12 occupies in the total value of thicknesses L1, L2, L3, and L4.

[0059] For example, when thickness L2 = 70 μm, thickness L3 = 400 μm, and thickness L4 = 65 μm, each of thickness L11 and thickness L12 is 267.5 μm or more. Also, in this case, it is still better if each of thickness L11 and thickness L12 is 327.5 μm or more. As an example, thickness L11 is 400 μm and thickness L12 is 725 μm.

[0060] When thickness L11 is 400 μm and thickness L12 is 725 μm, it becomes possible to make the rigidity of the entire liquid ejection head 1B according to Modification 2 higher than the rigidity of the entire liquid ejection head 1 according to the first embodiment. Also, different from the case of increasing the thickness of the sealing plate 35 itself having normal functions like the liquid ejection head 1 according to the first embodiment, in the liquid ejection head 1B according to Modification 2, the thickness of the sealing plate 35A having normal functions is not changed, and a sealing plate 35B for the purpose of increasing rigidity is laminated on the Z2 side of the sealing plate 35A. That is, in the liquid ejection head 1B according to Modification 2, after diverting the sealing plate 35A in which the recess 350 is formed in advance and which is normally used, a sealing plate 35B for the purpose of increasing rigidity is laminated on the Z2 side of the sealing plate 35A. As a result, since it is not necessary to form the recess 350 in the sealing plate 35 that is thicker than normal after increasing the thickness of the sealing plate 35 itself having normal functions, the manufacturing of the liquid ejection head 1B according to Modification 2 becomes easier compared to the liquid ejection head 1 according to the first embodiment.

Explanation of Reference Numerals

[0061] 1, 1A, 1B: Liquid ejection head, 3: Actuator, 5: Liquid ejection head, 12: Medium, 14: Liquid container, 20: Control unit, 22: Conveyor mechanism, 24: Moving mechanism, 30: Flow path structure, 31: Communication plate, 32: Pressure chamber substrate, 33: Diaphragm, 34: Piezoelectric element, 35, 35A, 35B: Sealing plate, 36: Housing part, 41: Nozzle substrate, 42: Vibration absorber, 51: Wiring substrate, 100: Liquid ejection device, 242: Storage case, 244: Endless belt, 312: Supply flow path, 314: Communication flow path, 316: Relay liquid chamber, 320: Wall surface, 350: Recess, 361: Supply port, C, C1, C2: Pressure chamber, L1, L11, L12, L2, L3, L4: Thickness, Ln, Ln1, Ln2: Nozzle row, Lp1: First piezoelectric element row, Lp2: Second piezoelectric element row, N, N1, N2: Nozzle, R: Liquid storage chamber, Ra, Rb: Space

Claims

1. A piezoelectric element, a nozzle substrate provided with nozzles, a communication plate located above the nozzle substrate and provided with a communication flow path communicating with the nozzles, a pressure chamber substrate located above the communication plate and provided with a pressure chamber communicating with the communication flow path for applying pressure to a liquid, a sealing plate located above the pressure chamber substrate and provided with a recess for sealing the space where the piezoelectric element is disposed, a liquid ejection head comprising: The ratio of the thickness of the sealing plate to the total thickness of the nozzle substrate, the communication plate, the pressure chamber substrate, and the sealing plate is 50% or more. A liquid ejection head characterized by this.

2. The ratio of the thickness of the sealing plate to the total thickness of the nozzle substrate, the communication plate, the pressure chamber substrate, and the sealing plate is 55% or more. The liquid ejection head according to claim 1, characterized by this.

3. The ratio of the thickness of the sealing plate to the total thickness of the nozzle substrate, the communication plate, the pressure chamber substrate, and the sealing plate is 70% or less. The liquid ejection head according to claim 1, characterized by this.

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