Liquid dispensing head

Abstract

To provide a liquid dispensing head suitable for high-speed operation. [Solution] The liquid discharge head comprises a piezoelectric element having a piezoelectric layer, a diaphragm that vibrates when driven by the piezoelectric element, and a pressure chamber substrate that defines a pressure chamber that applies pressure to the liquid by the vibration of the diaphragm. The pressure chamber substrate, the diaphragm, and the piezoelectric element are stacked in the stacking direction in that order, and the density of the diaphragm is higher than the density of the liquid in the pressure chamber. Furthermore, in the region of the diaphragm, when the region that bends toward the pressure chamber when driven by the piezoelectric element is defined as a flexible portion in the width direction intersecting the stacking direction, and the region located above the side wall defining the pressure chamber is defined as a non-flexible portion, it is preferable that the density of the flexible portion of the diaphragm is higher than the density of the non-flexible portion.

Description

[Technical Field]

[0001] This invention relates to a liquid dispensing head. [Background technology]

[0002] Image forming apparatuses equipped with a liquid ejection head that ejects liquids such as ink onto a medium such as printing paper have been proposed for some time. As such a liquid ejection head, a piezo-type head is known that ejects the liquid filled in the pressure chamber from a nozzle by vibrating a diaphragm that constitutes the wall of the pressure chamber with a piezoelectric element.

[0003] Patent Document 1 discloses a liquid discharge head that discharges liquid by contracting a pressure chamber through the application of voltage to a piezoelectric element. In this document, the diaphragm includes, for example, silicon dioxide (SiO2). In this document, the change in polarization is suppressed and the compliance of the diaphragm is reduced by providing at least one potential stabilization period during the damped vibration of the meniscus in the nozzle. As a result, the vibration period of the meniscus is reduced, enabling high-speed driving. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2002-331664 [Overview of the project] [Problems that the invention aims to solve]

[0005] The technology described in Patent Document 1 achieves high-speed drive by adjusting the applied potential. Thus, there is a need to increase the speed of the liquid ejection head drive in order to improve printing speed. However, adjusting the voltage for each piezoelectric element to achieve high-speed drive is time-consuming. Therefore, there is a need to achieve high-speed drive using other methods. [Means for solving the problem]

[0006] A liquid discharge head according to a preferred embodiment of the present invention comprises a piezoelectric element having a piezoelectric layer, a diaphragm that vibrates by driving the piezoelectric element, and a pressure chamber substrate that partitions a pressure chamber for applying pressure to a liquid by the vibration of the diaphragm, wherein the pressure chamber substrate, the diaphragm, and the piezoelectric element are stacked in the stacking direction in that order, and the density of the diaphragm is higher than the density of the liquid in the pressure chamber. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram illustrating the configuration of an image forming apparatus according to the first embodiment. [Figure 2] Figure 1 is an exploded perspective view of the liquid dispensing head. [Figure 3] This is a cross-sectional view of a portion of the liquid dispensing head shown in Figure 1. [Figure 4] Figure 3 is a cross-sectional view of the diaphragm and piezoelectric element. [Figure 5] This is a cross-sectional view of the diaphragm and piezoelectric element of the first modified example. [Modes for carrying out the invention]

[0008] Preferred embodiments of the present invention will be described below with reference to the attached drawings. Note that the dimensions or scale of each part in the drawings may differ from the actual dimensions as appropriate, and some parts are shown schematically for ease of understanding. Furthermore, the scope of the present invention is not limited to these embodiments unless otherwise stated in the following description. Also, "element β on element γ" is not limited to a configuration in which element γ and element β are in direct contact, but also includes configurations in which element γ and element β are not in direct contact. "Element γ and element β are equal" means that element γ and element β are substantially equal, including manufacturing tolerances, etc. Also, "element α and element β are stacked" means that element α and element β are aligned in the vertical direction, and it is not required that element α and element β are in direct contact.

[0009] 1. First Embodiment 1-1. Overall configuration of the image forming apparatus 100 FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus 100 according to the first embodiment. Hereinafter, for convenience of explanation, the X-axis, Y-axis, and Z-axis orthogonal to each other will be appropriately used for explanation. Also, one direction along the X-axis is denoted as the X1 direction, and the direction opposite to the X1 direction is denoted as the X2 direction. Similarly, one direction along the Y-axis is denoted as the Y1 direction, and the direction opposite to the Y1 direction is denoted as the Y2 direction. One direction along the Z-axis is denoted as the Z1 direction, and the direction opposite to the Z1 direction is denoted as the Z2 direction. Looking in the direction along the Z-axis is referred to as "plan view". Also, the "lamination direction" is the direction along the Z-axis. The Z-axis is typically a vertical axis. The Z2 direction is the upper side, and the Z1 direction is the lower side. However, the Z-axis does not necessarily have to be a vertical axis. Also, the X-axis, Y-axis, and Z-axis are typically orthogonal to each other, but are not limited thereto, and for example, they may intersect at an angle within the range of 80° or more and 100° or less.

[0010] The image forming apparatus 100 in FIG. 1 is an inkjet printing apparatus that discharges a liquid such as ink onto a medium 90. The medium 90 is typically printing paper, but a printing object of any material such as a resin film or fabric can be used as the medium 90. As illustrated in FIG. 1, a liquid container 9 for storing a liquid is installed in the image forming apparatus 100. For example, a cartridge detachable from the image forming apparatus 100, a bag-shaped liquid pack formed of a flexible film, or a liquid tank capable of replenishing liquid is used as the liquid container 9.

[0011] The image forming apparatus 100 includes a control unit 20, a medium conveyance mechanism 22, a movement mechanism 24, and a liquid discharge head 3. The control unit 20 includes one or more processing circuits such as a CPU (Central Processing Unit) or an FPGA (Field Programmable Gate Array), and one or more storage circuits such as a semiconductor memory, and comprehensively controls each element of the image forming apparatus 100.

[0012] The media conveyance mechanism 22 conveys the media 90 in a direction along the Y-axis under the control of the control unit 20. Further, the movement mechanism 24 reciprocates the liquid ejection head 3 along the X-axis under the control of the control unit 20. The movement mechanism 24 includes a substantially box-shaped carrier 242 that houses the liquid ejection head 3 and a conveyor belt 244 to which the carrier 242 is fixed. A configuration in which a plurality of liquid ejection heads 3 are mounted on the carrier 242 or a configuration in which the liquid container 9 is mounted on the carrier 242 together with the liquid ejection head 3 may also be adopted.

[0013] The liquid ejection head 3 ejects the liquid supplied from the liquid container 9 onto the media 90 from a plurality of nozzles under the control of the control unit 20. By ejecting the liquid onto the media 90 by each liquid ejection head 3 in parallel with the conveyance of the media 90 by the media conveyance mechanism 22 and the repeated reciprocation of the carrier 242, an image is formed on the surface of the media 90.

[0014] Note that the image forming apparatus 100 is of a serial head type in which the liquid ejection head 3 reciprocates on the media 90. However, the image forming apparatus 100 may be of a line head type in which the liquid ejection head 3 is fixed.

[0015] 1-2. Overall Configuration of Liquid Ejection Head 3 FIG. 2 is an exploded perspective view of the liquid ejection head 3 shown in FIG. 1. FIG. 3 is a partial cross-sectional view of the liquid ejection head shown in FIG. 1 and is a cross-sectional view taken along line a-a in FIG. 2. The cross-section shown in FIG. 3 is a cross-section parallel to the X-Z plane. Note that the Z-axis is an axis along the liquid ejection direction by the liquid ejection head 3.

[0016] As illustrated in Figure 2, the liquid discharge head 3 comprises a plurality of nozzles N arranged along the Y-axis. The plurality of nozzles N in the first embodiment are divided into a first row La and a second row Lb, which are spaced apart from each other and arranged side by side along the X-axis. Each of the first row La and the second row Lb is a collection of a plurality of nozzles N arranged linearly along the Y-axis. The liquid discharge head 3 has a structure in which the elements associated with each nozzle N in the first row La and the elements associated with each nozzle N in the second row Lb are arranged substantially symmetrically. In the following description, the elements corresponding to the first row La will be described in detail, and the descriptions of the elements corresponding to the second row Lb will be omitted as appropriate.

[0017] As illustrated in Figures 2 and 3, the liquid discharge head 3 comprises a flow path forming substrate 31, a pressure chamber substrate 32, a diaphragm 33, a nozzle plate 37, a vibration absorber 38, a plurality of piezoelectric elements 5, a sealant 35, a housing portion 36, and a wiring board 40. Each of the flow path forming substrate 31, pressure chamber substrate 32, diaphragm 33, nozzle plate 37, vibration absorber 38, sealant 35, and housing portion 36 is a long, plate-shaped member along the Y-axis. Furthermore, the nozzle plate 37, flow path forming substrate 31, pressure chamber substrate 32, diaphragm 33, and sealant 35 are arranged in this order in the Z2 direction.

[0018] The nozzle plate 37 is a plate-shaped member on which a plurality of nozzles N are formed. Each of the plurality of nozzles N is a circular through-hole for discharging liquid. The nozzle plate 37 is joined to the Z1 direction surface of the flow path forming substrate 31, for example, by adhesive.

[0019] The channel-forming substrate 31 forms channels through which liquid flows. Specifically, the channel-forming substrate 31 has a space Ra, an intermediate liquid chamber Rb, a plurality of supply channels 312, and a plurality of communication channels 314. Space Ra is an elongated opening formed along the Y-axis. Each of the supply channels 312 and communication channels 314 is a through-hole formed for each nozzle N. Each communication channel 314 overlaps a corresponding nozzle N in a plan view from the Z1 direction. The intermediate liquid chamber Rb is an elongated space formed along the Y-axis across multiple nozzles N, and connects space Ra and the plurality of supply channels 312 to each other. A pressure chamber substrate 32 is bonded to the Z2 direction surface of the channel-forming substrate 31 with adhesive.

[0020] Multiple pressure chambers C1 are formed in the pressure chamber substrate 32. The pressure chamber substrate 32 partitions the pressure chambers C1, which apply pressure to the liquid by the vibration of the diaphragm 33. The pressure chamber substrate 32 is made of, for example, silicon oxide (SiO2). x The pressure chamber C1 is composed of the following components. The liquid discharged from the nozzle N is stored in the pressure chamber C1. The pressure chamber C1 is located between the nozzle plate 37 and the diaphragm 33 and is a space formed by the inner wall surface of the pressure chamber substrate 32. A pressure chamber C1 is formed for each nozzle N. The pressure chamber C1 is an elongated space and extends in the X1 direction. Multiple pressure chambers C1 are arranged along the Y axis. Each pressure chamber C1 communicates with the communication channel 314 and the supply channel 312. Therefore, the pressure chamber C1 communicates with the nozzle N via the communication channel 314 and with the space Ra via the supply channel 312 and the intermediate liquid chamber Rb.

[0021] The nozzle plate 37, the channel-forming substrate 31, and the pressure chamber substrate 32 are manufactured by processing a silicon (Si) single crystal substrate using semiconductor manufacturing technologies such as photolithography and etching. However, known materials and manufacturing methods can be arbitrarily used for the manufacture of the nozzle plate 37, the channel-forming substrate 31, and the pressure chamber substrate 32.

[0022] The diaphragm 33 is connected to the surface of the pressure chamber substrate 32 opposite to the flow channel forming substrate 31. The diaphragm 33 is positioned on the pressure chamber C1 and is elastically deformable. The diaphragm 33 vibrates when driven by the piezoelectric element 5. The diaphragm 33 is a plate-like member formed in a long rectangular shape along the Y-axis in a plan view. A part of the diaphragm 33 may be integrally formed with the pressure chamber substrate 32, or it may be a separate part joined together with an adhesive or the like.

[0023] A piezoelectric element 5 is formed on the surface of the diaphragm 33 opposite to the pressure chamber C1. A piezoelectric element 5 is provided for each pressure chamber C1. The piezoelectric element 5 is elongated in shape along the X-axis in a plan view. The piezoelectric element 5 is a driving element that is driven when a driving signal is applied, and it applies pressure to the liquid in the pressure chamber C1.

[0024] The seal 35 is bonded to the diaphragm 33, for example, by adhesive. The seal 35 is a structure that protects the multiple piezoelectric elements 5 and reinforces the mechanical strength of the pressure chamber substrate 32 and the diaphragm 33. A recess is formed in the seal 35 on the surface facing the diaphragm 33. The multiple piezoelectric elements 5 are housed inside this recess. The seal 35 also has a space 353 through which the wiring board 40 is inserted.

[0025] The housing portion 36 is joined to the flow channel forming substrate 31, for example, by adhesive. The housing portion 36 is a case for storing liquid supplied to a plurality of pressure chambers C1. The housing portion 36 is formed, for example, by injection molding of a resin material. The housing portion 36 has a space Rc, a supply port 361, and a space 362. The supply port 361 is a conduit through which liquid is supplied from the liquid container 9 and communicates with space Rc. Space Rc communicates with space Ra of the flow channel forming substrate 31. The space composed of space Rc and space Ra functions as a liquid storage chamber R for storing liquid supplied to the plurality of pressure chambers C1. Liquid supplied from the liquid container 9 and passing through the supply port 361 is stored in the liquid storage chamber R. The liquid stored in the liquid storage chamber R branches from the relay liquid chamber Rb to each supply flow channel 312 and is supplied in parallel to the plurality of pressure chambers C1. Also, space 362 overlaps with space 353 of the sealing body 35 in a plan view. The wiring board 40 is inserted through spaces 353 and 362.

[0026] The wiring board 40 is connected to the diaphragm 33. The wiring board 40 is a mounted component on which multiple wires are formed for electrically connecting the control unit 20 and the liquid discharge head 3. For example, a flexible substrate such as an FPC (Flexible Printed Circuit) or FFC (Flexible Flat Cable) is preferably used for the wiring board 40. A drive signal and a reference voltage for driving the piezoelectric elements 5 are supplied from the wiring board 40 to each piezoelectric element 5.

[0027] Furthermore, a vibration absorber 38 is bonded to the Z1-direction surface of the channel-forming substrate 31, for example, by an adhesive. The vibration absorber 38 is a flexible film that constitutes the wall surface of the space Ra and absorbs pressure fluctuations of the liquid in the liquid storage chamber R.

[0028] In this liquid discharge head 3, when the piezoelectric element 5 is deflected and deformed by the application of voltage, the diaphragm 33 deflects and vibrates in a direction that reduces the volume of the pressure chamber C1. As a result, the pressure in the pressure chamber C1 changes, and the liquid in the pressure chamber C1 is discharged from the nozzle N. After the liquid is discharged, the piezoelectric element 5 returns to its original position.

[0029] Furthermore, although the liquid discharge head 3 includes all the elements shown in Figure 3, the components of the liquid discharge head 3 do not necessarily have to include all of these elements, and may also include additional elements.

[0030] 1-3. Piezoelectric element 5 and diaphragm 33 Figure 4 is a cross-sectional view showing the diaphragm 33 and piezoelectric element 5 in Figure 3. The cross-section shown in Figure 4 is parallel to the YZ plane.

[0031] As shown in Figure 4, the piezoelectric element 5 mainly consists of a lower electrode 51, a piezoelectric layer 53, and an upper electrode 52. The lower electrode 51, the piezoelectric layer 53, and the upper electrode 52 are stacked in a direction along the Z-axis, which is the stacking direction.

[0032] The lower electrode 51 is provided above the diaphragm 33. The lower electrode 51 is an individual electrode provided for each piezoelectric element 5. A drive signal with fluctuating voltage is applied to the lower electrode 51. The lower electrode 51 is elongated along the X-axis. Multiple lower electrodes 51 are arranged along the Y-axis with spacing between them. The lower electrode 51 contains a conductive material.

[0033] The piezoelectric layer 53 is provided above the lower electrode 51. The piezoelectric layer 53 is, for example, a strip-shaped dielectric film that is continuous along the Y-axis across multiple piezoelectric elements 5. The piezoelectric layer 53 is, for example, a strip extending along the Y-axis and is separated for each piezoelectric element 5 by the formation of multiple notches. The piezoelectric layer 53 is composed of, for example, a piezoelectric material having a perovskite-type crystal structure.

[0034] Examples of the piezoelectric material include lead titanate (PbTiO3), lead zirconate titanate (PZT: Pb(Zr,Ti)O3), lead zirconate (PbZrO3), lead lanthanum titanate ((Pb,La),TiO3), lead lanthanum zirconate titanate ((Pb,La)(Zr,Ti)O3), lead zirconium niobate titanate (Pb(Zr,Ti,Nb)O3), lead zirconium magnesium niobate titanate (Pb(Zr,Ti)(Mg,Nb)O3), and potassium sodium niobate (KNN: (K,Na)NbO3). Among these, lead zirconate titanate (PZT) is preferably used as the constituent material of the piezoelectric layer 53.

[0035] The upper electrode 52 is provided above the piezoelectric layer 53. The upper electrode 52 is a strip-shaped common electrode that extends along the Y-axis so as to be continuous across multiple piezoelectric elements 5. A predetermined reference voltage is applied to the upper electrode 52. The upper electrode 52 contains a conductive material.

[0036] A voltage equivalent to the difference between the reference voltage applied to the upper electrode 52 and the drive signal corresponding to the discharge amount supplied to the lower electrode 51 is applied to the piezoelectric layer 53. The piezoelectric layer 53 deforms as a result of the voltage applied between the lower electrode 51 and the upper electrode 52, causing the piezoelectric element 5 to bend and deform, i.e., vibrate.

[0037] The diaphragm 33 vibrates when driven by the piezoelectric element 5. In the illustrated example, the diaphragm 33 is composed of a laminate including a first layer 331 and a second layer 332. The first layer 331 is in contact with the lower electrode 51 and the pressure chamber substrate 32. The second layer 332 is positioned above the first layer 331. The second layer 332 is located closer to the piezoelectric element 5 than the first layer 331. The second layer 332 is made of, for example, zirconium oxide (ZrO x The first layer 331 is formed of an insulating material such as silicon oxide (SiO2). The second layer 332 is formed by known film deposition techniques such as sputtering. x It includes and is formed by thermal oxidation of a part of the pressure chamber substrate 32. The diaphragm 33 may be composed of one layer or three or more layers.

[0038] Furthermore, the diaphragm 33 has a flexible portion S1 and a non-flexible portion S2. The flexible portion S1 and the non-flexible portion S2 are regions in the cross-section viewed in the direction along the Y-axis, which is the width direction. The flexible portion S1 is a part of the diaphragm 33 that bends toward the pressure chamber C1 when driven by the piezoelectric element 5. The non-flexible portion S2 is a part of the diaphragm 33 that is located above the side wall 32a that partitions the pressure chamber C1.

[0039] Furthermore, the flexible portion S1 has an overlapping region S11 and a non-overlapping region S12. The overlapping region S11 and the non-overlapping region S12 are regions in the cross-section viewed in the direction along the Y-axis, which is the width direction. The overlapping region S11 is the region of the flexible portion S1 that overlaps with the piezoelectric layer 53 in the direction along the Z-axis, which is the stacking direction. The non-overlapping region S12 is the region of the flexible portion S1 that does not overlap with the piezoelectric layer 53 in the direction along the Z-axis, which is the stacking direction.

[0040] Furthermore, the overlapping region S11 has a first region S111 and a second region S112. The first region S111 and the second region S112 are regions in the cross-section viewed in the direction along the Y-axis, which is the width direction. The first region S111 is the region that overlaps with the lower electrode 51 in the direction along the Z-axis, which is the stacking direction. The second region S112 is the region that does not overlap with the lower electrode 51 in the direction along the Z-axis, which is the stacking direction, and where the diaphragm 33, the lower electrode 51, the piezoelectric layer 53, and the upper electrode 52 overlap. In other words, the first region S111 is the region where the piezoelectric layer 53 is sandwiched between the lower electrode 51 and the upper electrode 52 in the direction along the Z-axis, which is the stacking direction. The second region S112 is the region where the piezoelectric layer 53 is not sandwiched between the lower electrode 51 and the upper electrode 52 in the direction along the Z-axis, which is the stacking direction.

[0041] Here, in a piezo-type liquid discharge head 3 having a piezoelectric element 5 and a diaphragm 33, high-speed driving is required. In conventional liquid discharge heads, the diaphragm contains silicon dioxide, and high-speed driving was achieved by adjusting the potential applied to the piezoelectric element.

[0042] In contrast, this embodiment provides a liquid discharge head 3 suitable for high-speed driving by a method other than adjusting the potential. Specifically, in this embodiment, a liquid discharge head 3 suitable for high-speed driving is provided by making the density of the diaphragm 33 greater than the density of the liquid in the pressure chamber C1. Note that the density of the liquid is the density of the liquid filling the pressure chamber C1, regardless of whether or not pressure is applied to the liquid by the diaphragm 33.

[0043] By making the density of the diaphragm 33 greater than the density of the liquid in the pressure chamber C1, the natural vibration period Tc of the liquid discharge head 3 can be shortened. Therefore, a liquid discharge head 3 suitable for high-speed operation can be provided.

[0044] Specifically, the mass of the diaphragm 33 can be increased by increasing its density. This allows the natural vibration period Tc of the pressure chamber C1 to be shortened when the pressure chamber C1 is filled with liquid.

[0045] Conventional diaphragms were primarily made of materials such as silicon dioxide. Therefore, the mass of the diaphragm 33 tends to be smaller than the mass of the pressure chamber C1 when it is filled with liquid. Because the mass of the diaphragm 33 is lighter than the mass of the liquid in the pressure chamber C1, the natural vibration period Tc becomes longer when the pressure chamber C1, including the liquid, is vibrated. A long natural vibration period Tc makes it difficult for residual vibrations to attenuate, and during high-speed discharge, these residual vibrations interfere with the next discharge vibration. As a result, the liquid discharge becomes unstable.

[0046] Let fa be the natural frequency of the diaphragm 33 when there is no liquid in the pressure chamber C1, and let fc be the natural frequency of the diaphragm 33 when there is liquid in the pressure chamber C1. In this case, the relationship between the natural frequencies fa and fc is expressed by the following equation (1), where Ma is the mass of the diaphragm 33 and Mi is the mass of the liquid in the pressure chamber C1.

number

[0047] Strictly speaking, the mass Ma is determined by the masses of the piezoelectric element 5 and the diaphragm 33 involved in the vibration of the pressure chamber C1. However, assuming that the weight of the piezoelectric element 5 remains constant, the mass Ma is considered to be the mass of the diaphragm 33. Changing the weight of the piezoelectric element 5 is undesirable because it would significantly alter the characteristics of the piezoelectric element, so it is assumed to remain constant.

[0048] From equation (1) above, the natural frequency fa when there is liquid in the pressure chamber C1, i.e., when mass Mi > 0, is smaller than the natural frequency fa when there is no liquid in the pressure chamber C1, i.e., when mass Mi = 0. In other words, the natural vibration period Tc is longer when there is liquid in the pressure chamber C1 compared to when there is no liquid. For example, when Mi = 3 × Ma, the natural frequency fc = 1 / 2fa. When Mi = 8 × Ma, the natural frequency fc = 1 / 3fa. The larger the mass Mi is relative to the mass Ma, the smaller the natural frequency fc becomes. Since the natural vibration period Tc is inversely proportional to the natural frequency fa, the larger the mass Ma of the diaphragm 33, the longer the natural vibration period Tc becomes.

[0049] The mass Ma of the diaphragm 33 is determined by its density, width, length, and thickness. Increasing the width and length increases the pressure chamber C1. As a result, the mass Mi of the liquid increases, making it difficult to increase the mass Ma of the diaphragm 33 relative to the liquid mass Mi. Regarding the thickness, for example, the stiffness of the diaphragm 33, i.e., the second moment of area, increases with the cube of the thickness, so increasing the thickness makes it more difficult for the diaphragm 33 to displace. For this reason, increasing the thickness of the diaphragm 33 to increase its mass Ma is not optimal. In contrast, increasing the density of the diaphragm 33 is optimal for increasing its mass Ma. By increasing the density of the diaphragm 33, the natural vibration period Tc can be shortened while avoiding the problems with width, length, and thickness mentioned above.

[0050] For these reasons, in this embodiment, the density of the diaphragm 33 is increased to be greater than the density of the liquid in the pressure chamber C1, thereby increasing the mass Ma of the diaphragm 33 and reducing the degree to which the natural frequency fc is smaller than the natural frequency fa. As a result, the natural vibration period Tc can be shortened, and a liquid discharge head 3 suitable for high-speed operation can be provided.

[0051] Furthermore, from the viewpoint of increasing the density of the diaphragm 33, it is preferable that the density of the diaphragm 33 is higher than the density of the pressure chamber substrate 32. The pressure chamber substrate 32 is, for example, silicon oxide (SiO2). x It consists of ).

[0052] Furthermore, as mentioned above, in this embodiment, unlike conventional techniques for adjusting the potential, high-speed driving is achieved through the structure of the liquid discharge head 3. However, even higher speed driving may be achieved by combining the liquid discharge head 3 of this embodiment with a technique for adjusting the potential.

[0053] Furthermore, as mentioned above, the diaphragm 33 has a flexible portion S1 and a non-flexible portion S2. Preferably, the density in the flexible portion S1 is higher than the density in the non-flexible portion S2. By increasing the density in the flexible portion S1, the density of the diaphragm 33 related to the natural frequency fa can be increased. Also, considering vibration as displacement, when transmitting vibration energy, it is preferable to increase the density of the portion close to the piezoelectric element 5, which is the vibration source. Therefore, by increasing the density of the flexible portion S1 above the density of the non-flexible portion S2, the vibration of the piezoelectric element 5 can be efficiently transmitted to the diaphragm 33 and further to the liquid in the pressure chamber C1.

[0054] Furthermore, as mentioned above, the flexible portion S1 has an overlapping region S11 and a non-overlapping region S12. Preferably, the density of the diaphragm 33 in the overlapping region S11 is higher than the density of the diaphragm 33 in the non-overlapping region S12. By increasing the density in the overlapping region S11, the density of the diaphragm 33 related to the natural frequency fa can be increased. In addition, by increasing the density of the overlapping region S11 compared to the density of the non-overlapping region S12, the vibration of the piezoelectric element 5 can be transmitted efficiently.

[0055] Also, as described above, the overlapping region S11 preferably has a first region S111 and a second region S112. The density of the diaphragm 33 in the first region S111 is preferably higher than the density of the diaphragm 33 in the second region S112. By increasing the density in the first region S111, the density of the diaphragm 33 related to the natural frequency fa can be increased. Also, by increasing the density of the first region S111 higher than the density of the second region S112, the vibration of the piezoelectric element 5 can be efficiently transmitted.

[0056] Also, the density of the flexible portion S1 is not particularly limited, but is preferably 2.70 g / cm 3 or more and 9.68 g / cm 3 or less, and more preferably 3.20 g / cm 3 or more and 4.44 g / cm 3 or less.

[0057] By being within such a range, the natural vibration period Tc can be shortened compared to the case of being outside the range, enabling high-speed ejection. Also, it is possible to suppress the possibility that the diaphragm 33 becomes difficult to displace due to too high density.

[0058] Also, the density of the second layer 332 is preferably higher than the density of the first layer 331. As described above, when transmitting vibration energy, it is preferable to increase the density of the portion closer to the piezoelectric element 5 which is the vibration source. Therefore, by increasing the density of the second layer 332 higher than the density of the first layer 331, the vibration of the piezoelectric element 5 can be efficiently transmitted.

[0059] The density of the diaphragm 33 is determined, for example, by the density of the material of the first layer 331, the density of the material of the second layer 332, and the ratio of the thicknesses of the first layer 331 and the second layer 332. For example, consider the case where the first layer 331 contains silicon dioxide (SiO2) and the second layer 332 contains zirconium dioxide (ZrO2). The density of silicon dioxide is 2.65 g / cm 3 and the density of zirconium dioxide is 5.68 g / cm 3 is.

[0060] For example, if SiO2:ZrO2 = 3:2, the average density of the diaphragm 33 is 3.68 g / cm³. 3 For example, if SiO2:ZrO2 = 5:1, the average density of the diaphragm 33 is 3.16 g / cm³. 3 For example, if SiO2:ZrO2 = 2:3, the average density of the diaphragm 33 is 4.47 g / cm³. 3 The above ratio of SiO2 to ZrO2 is adjusted, for example, by the film thickness.

[0061] Furthermore, the second layer 332 may contain at least one of tantalum (Ta), chromium (Cr), hafnium (Hf), iron (Fe), and lead (Pb). By including any of these, the density of the second layer 332 can be adjusted to be higher.

[0062] For example, the second layer 332 may have other components added in addition to the main component. Specifically, for example, if the main component of the second layer 332 is zirconium oxide (ZrOx), then a material containing at least one of Ta, Cr, Hf, Fe, and Pb may be added as another component. The main component is a component that makes up 50% or more of the constituent material of the second layer 332. Examples of such other components include hafnium oxide (HfOx). x ) are examples of other components. In addition, titanium (Ti), silicon (Si), aluminum (Al), iridium (Ir), and carbon (C) may be included.

[0063] The inclusion of these other components in the second layer 332 adjusts the density of the second layer 332, and consequently, the density of the diaphragm 33. Furthermore, when the main component of the second layer 332 is zirconium oxide, the inclusion of hafnium oxide as another component increases the average density of the diaphragm 33, as well as improving its strength and heat resistance.

[0064] For example, consider the case where the first layer 331 is composed of silicon dioxide, the second layer 332 contains zirconium dioxide as its main component, and the second layer 332 contains hafnium dioxide as another component. The density of silicon dioxide is 9.68 g / cm³. 3 For example, if SiO2:ZrO2 = 5:1 and the amount of hafnium dioxide added is 5%, then the density of the diaphragm 33 is 4.59 g / cm³. 3 For example, if SiO2:ZrO2 = 5:1 and the amount of hafnium dioxide added is 20%, the density of the diaphragm 33 is 4.95 g / cm³. 3 That is the case.

[0065] For example, when the second layer 332 is formed by sputtering and thermal oxidation, a sputtering target containing a mixture of zirconium and hafnium is used. Subsequently, the second layer 332, in which hafnium oxide is added to zirconium oxide, is formed through a thermal oxidation process. Alternatively, a layer composed of zirconium and a layer composed of hafnium may be laminated by sputtering, and hafnium may be diffused into the zirconium layer by thermal oxidation to form the second layer 332.

[0066] Furthermore, the density of the flexible portion S1 is preferably at least half the density of the piezoelectric material constituting the piezoelectric layer 53. For example, if the density of PZT in the piezoelectric layer 53 is 7.7 g / cm³, the density of the diaphragm 33 is preferably 3.9 g / cm³ or more. In this way, by making the density of the diaphragm 33 connected to the piezoelectric element 5 half the density of the piezoelectric layer 53, the mass of the diaphragm 33 can be increased while efficiently transmitting the vibrations of the piezoelectric element 5.

[0067] The density of the flexible portion S1 may be less than half the density of the piezoelectric material constituting the piezoelectric layer 53. For example, if the piezoelectric layer 53 is composed of KNN, the density of KNN is 4.5 g / cm³.

[0068] Furthermore, it is preferable that the thickness T3 of the diaphragm 33 is greater than the thickness T5 of the piezoelectric element 5. When the thickness T3 of the diaphragm 33 is greater than the thickness T5 of the piezoelectric element 5, the diaphragm 33 can be displaced more efficiently compared to when it is smaller, and the vibrations of the diaphragm 33 can be efficiently transmitted to the pressure chamber C1.

[0069] The thickness T3 of the diaphragm 33 is not particularly limited, but it is preferably between 1.46 μm and 3.0 μm. As the thickness T3 increases, the second moment of area increases, and the displacement of the diaphragm 33 decreases. Therefore, by keeping the thickness T3 within the specified range, the decrease in the displacement of the diaphragm 33 can be suppressed compared to when it is outside the range. In addition, the risk of damage to the diaphragm 33 due to displacement caused by a thickness T3 that is too thin can be suppressed.

[0070] 2. Variations The embodiments illustrated above can be modified in various ways. Specific examples of modifications that can be applied to the aforementioned embodiments are given below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate, to the extent that they do not contradict each other.

[0071] 2-1. First variation Figure 5 is a cross-sectional view of the diaphragm 33A and piezoelectric element 5 of the first modified example. As shown in Figure 5, in the first modified example, the diaphragm 33A is composed of one layer. The diaphragm 33A is made of, for example, zirconium oxide (ZrO x ), or hafnium oxide (HfO x It consists of ) and the like.

[0072] In this modified example, where the diaphragm 33A is composed of a single layer, the density of the flexible portion S1 is not particularly limited, but is approximately 2.70 g / cm³, similar to the embodiment. 3 More than 9.68g / cm 3 The following is preferable:

[0073] By using the diaphragm 33A of this modified example, a liquid discharge head 3 suitable for high-speed driving can be provided, similar to the embodiment.

[0074] 2-2. Other variations For example, a conductor that functions as a weight may be placed on the upper electrode 52. This conductor is made of an electrically low-resistance conductive material such as gold. By providing the conductor, the voltage drop of the reference voltage at the upper electrode 52 is suppressed.

[0075] The main component of the second layer 332 is not limited to zirconium oxide (ZrOx), but may be one element, oxide, or nitride selected from titanium (Ti), silicon (Si), aluminum (Al), chromium (Cr), iridium (Ir), carbon (C), iron (Fe), and Pb (lead).

[0076] The density of the diaphragm 33 may be higher than the density of the pressure chamber substrate 32. Furthermore, the density of the flexible portion S1 of the diaphragm 33 may be higher than the density of the pressure chamber substrate 32. For example, the diaphragm 33 and the pressure chamber substrate 32 may be formed from the same material, such as silicon oxide, but by increasing the density of the diaphragm 33 as in this embodiment, the vibration period can be suitably shortened.

[0077] Furthermore, in the above-described embodiment, the lower electrode 51 is an individual electrode and the upper electrode 52 is a common electrode, but the lower electrode 51 may be a common electrode and the upper electrode 52 may be an individual electrode.

[0078] Furthermore, the "liquid discharge head" may be a circulating type head having a so-called circulation channel.

[0079] "Image forming apparatus" can be used not only in equipment dedicated to printing, but also in various other devices such as facsimile machines and photocopiers. The applications of image forming apparatus are not limited to printing. For example, an image forming apparatus that dispenses a colorant solution is used as a manufacturing apparatus to form color filters for display devices such as liquid crystal display panels. Also, an image forming apparatus that dispenses a conductive material solution is used as a manufacturing apparatus to form wiring and electrodes on a wiring board. Furthermore, an image forming apparatus that dispenses a solution of organic matter related to living organisms is used, for example, as a manufacturing apparatus to produce biochips.

[0080] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the embodiments described above. Furthermore, the configuration of each part of the present invention can be replaced with any configuration that performs a similar function to the embodiments described above, and any configuration can be added.

[0081] 3. Addendum From the above embodiments or modifications, for example, the following embodiments can be understood.

[0082] A liquid discharge head according to a first embodiment, which is a preferred example of the present disclosure, comprises a piezoelectric element having a piezoelectric layer, a diaphragm that vibrates by driving the piezoelectric element, and a pressure chamber substrate that partitions a pressure chamber for applying pressure to a liquid by the vibration of the diaphragm, wherein the pressure chamber substrate, the diaphragm, and the piezoelectric element are stacked in the stacking direction in that order, and the density of the diaphragm is higher than the density of the liquid in the pressure chamber.

[0083] In such a liquid discharge head, the vibration period of the liquid discharge head can be shortened by making the density of the diaphragm greater than the density of the liquid in the pressure chamber.

[0084] In the liquid discharge head of the second embodiment, which is a first preferred example, in the region of the diaphragm, in the width direction intersecting the stacking direction, the region that bends toward the pressure chamber by the driving of the piezoelectric element is defined as a flexible portion, and the region located above the side wall that partitions the pressure chamber is defined as a non-flexible portion, the density of the flexible portion of the diaphragm is higher than the density of the non-flexible portion.

[0085] With such a liquid dispensing head, increasing the density in the flexible section allows for a greater density of the diaphragm, which is related to the natural frequency. Furthermore, considering vibration as displacement, when transmitting vibration energy, it is preferable to increase the density in the section close to the density of the piezoelectric element, which is the vibration source. Therefore, by increasing the density of the flexible section compared to the density of the non-flexible section, the vibration of the piezoelectric element can be transmitted efficiently.

[0086] In the liquid discharge head of the third embodiment, which is a second preferred example, in the flexible portion, when the region overlapping with the piezoelectric layer in the width direction and the stacking direction is defined as an overlapping region, and the region not overlapping with the piezoelectric layer is defined as a non-overlapping region, the density of the diaphragm in the overlapping region is higher than the density of the diaphragm in the non-overlapping region.

[0087] With this liquid discharge head, increasing the density in the overlapping region allows for a greater density of the diaphragm related to the natural frequency. Furthermore, by increasing the density in the overlapping region compared to the density in the non-overlapping region, the vibrations of the piezoelectric element can be transmitted more efficiently.

[0088] In a liquid discharge head of a fourth embodiment, which is a third preferred example, the piezoelectric element has a lower electrode, a piezoelectric layer formed on the lower electrode, and an upper electrode formed on the piezoelectric layer, and in the overlapping region of the diaphragm, when the region in the stacking direction in which the piezoelectric layer is sandwiched between the lower electrode and the upper electrode is defined as a first region, and the region in the stacking direction in which the piezoelectric layer is not sandwiched between the lower electrode and the upper electrode is defined as a second region, the density of the diaphragm in the first region is higher than the density of the diaphragm in the second region.

[0089] With this liquid discharge head, increasing the density in the first region makes it possible to increase the density of the diaphragm related to the natural frequency. Furthermore, by making the density of the first region higher than the density of the second region, the vibrations of the piezoelectric element can be transmitted efficiently.

[0090] In the liquid dispensing head of the fifth embodiment, which is a preferred example of the first to third embodiments, when the region of the diaphragm that bends toward the pressure chamber by the driving of the piezoelectric element in the width direction intersecting the stacking direction is defined as the flexible portion, the density of the flexible portion of the diaphragm is 2.70 g / cm³. 3 More than 9.68g / cm 3 The following applies:

[0091] This type of liquid discharge head allows for a shorter vibration period, enabling high-speed discharge. Furthermore, it suppresses the risk of the diaphragm becoming difficult to displace due to excessively high density in the flexible section.

[0092] In the liquid dispensing head of the sixth embodiment, which is a fifth preferred example, the density of the flexible portion is 3.20 g / cm³. 3 More than 4.44g / cm 3 The following applies:

[0093] This type of liquid dispensing head allows for a shorter vibration period, enabling high-speed dispensing.

[0094] In the liquid dispensing head of the seventh embodiment, which is a fifth preferred example, the density of the flexible portion is at least half the density of the piezoelectric material constituting the piezoelectric layer.

[0095] With this liquid dispensing head, by halving the density of the diaphragm connected to the piezoelectric element, the diaphragm can be made heavier while efficiently transmitting the vibrations of the piezoelectric element.

[0096] In the eighth embodiment of the liquid discharge head, which is a preferred example of the first to seven, the diaphragm is formed from multiple layers, comprising a first layer and a second layer located closer to the piezoelectric element than the first layer, wherein the density of the second layer of the diaphragm is higher than the density of the first layer of the diaphragm.

[0097] In such a liquid dispensing head, when transmitting vibrational energy, it is preferable to increase the density of the portion close to the density of the piezoelectric element, which is the vibration source. By increasing the density of the second layer compared to the density of the first layer, the vibrations of the piezoelectric element can be transmitted efficiently.

[0098] In a liquid discharge head of the ninth embodiment, which is a preferred example of the first to seven, the diaphragm is formed from multiple layers, comprising a first layer containing Si and a second layer containing Zr, located closer to the piezoelectric element than the first layer, wherein the second layer contains at least one of Ta, Cr, Hf, Fe, and Pb.

[0099] With such a liquid dispensing head, the density of the second layer can be adjusted to be higher than that of the first layer by including these components.

[0100] In the liquid discharge head of the tenth embodiment, which is a preferred example of the first to nine, the thickness of the diaphragm is greater than the thickness of the piezoelectric element.

[0101] With such a liquid discharge head, the diaphragm can be displaced efficiently, and the vibrations of the diaphragm can be efficiently transmitted to the pressure chamber.

[0102] In the liquid discharge head of the 11th embodiment, which is a preferred example of the 1st to 10, the thickness of the diaphragm is 1.46 μm or more and 3.0 μm or less.

[0103] With such a liquid discharge head, within the scope of this configuration, the decrease in the amount of displacement of the diaphragm can be suppressed.

[0104] In the 11th embodiment of the liquid discharge head, which is a preferred example of the 1st to 10, the density of the diaphragm is higher than the density of the pressure chamber substrate.

[0105] With such a liquid discharge head, the vibration period can be suitably shortened even when the diaphragm and the pressure chamber substrate are made of the same material. [Explanation of symbols]

[0106] 3...Liquid discharge head, 5...Piezoelectric element, 32...Pressure chamber substrate, 32a...Side wall, 33...Diaphragm, 51...Lower electrode, 52...Upper electrode, 53...Piezoelectric layer, 100...Image forming apparatus, 331...First layer, 332...Second layer, C1...Pressure chamber, Ma...Mass, Mi...Mass, S1...Flexible part, S11...Overlapping region, S111...First region, S112...Second region, S12...Non-overlapping region, S2...Non-flexible part, T3...Thickness, T5...Thickness, Tc...Natural vibration period, fa...Natural frequency, fc...Natural frequency.

Claims

1. A piezoelectric element having a piezoelectric layer, A diaphragm that vibrates by driving the piezoelectric element, It comprises a pressure chamber substrate that partitions a pressure chamber that applies pressure to a liquid by the vibration of the diaphragm, The pressure chamber substrate, the diaphragm, and the piezoelectric element are stacked in that order in the stacking direction. The density of the diaphragm is higher than the density of the liquid in the pressure chamber. A liquid dispensing head characterized by the following features.

2. In the liquid discharge head according to claim 1, In the region of the diaphragm, when the region that bends toward the pressure chamber due to the driving of the piezoelectric element in the width direction intersecting the stacking direction is defined as a flexible portion, and the region located above the side wall that partitions the pressure chamber is defined as a non-flexible portion, The density of the flexible portion of the diaphragm is higher than the density of the non-flexible portion. A liquid dispensing head characterized by the following features.

3. In the liquid dispensing head according to claim 2, In the flexible portion, when the region in the width direction overlaps with the piezoelectric layer in the stacking direction is defined as an overlapping region, and the region that does not overlap with the piezoelectric layer is defined as a non-overlapping region, The density of the diaphragm in the overlapping region is higher than the density of the diaphragm in the non-overlapping region. A liquid dispensing head characterized by the following features.

4. In the liquid dispensing head according to claim 3, The piezoelectric element comprises a lower electrode, a piezoelectric layer formed on the lower electrode, and an upper electrode formed on the piezoelectric layer. In the overlapping region of the diaphragm, when the region in the stacking direction where the piezoelectric layer is sandwiched between the lower electrode and the upper electrode is defined as the first region, and the region in the stacking direction where the piezoelectric layer is not sandwiched between the lower electrode and the upper electrode is defined as the second region, The density of the diaphragm in the first region is higher than the density of the diaphragm in the second region. A liquid dispensing head characterized by the following features.

5. In the liquid dispensing head according to any one of claims 1 to 3, In the region of the diaphragm, when the region that bends toward the pressure chamber due to the driving of the piezoelectric element is defined as a flexible portion in the width direction intersecting the stacking direction, The density of the flexible portion of the diaphragm is 2.70 g / cm³. ３ 9.68g / cm or more ３ The following is: A liquid dispensing head characterized by the following features.

6. In the liquid discharge head according to claim 5, The density of the flexible part is 3.20 g / cm³. ３ 4.44g / cm or more ３ The following is: A liquid dispensing head characterized by the following features.

7. In the liquid discharge head according to claim 5, The density of the flexible portion is at least half the density of the piezoelectric material constituting the piezoelectric layer. A liquid dispensing head characterized by the following features.

8. In the liquid dispensing head according to any one of claims 1 to 4, The diaphragm is formed from multiple layers, and includes a first layer and a second layer located closer to the piezoelectric element than the first layer. The density of the second layer of the diaphragm is higher than the density of the first layer of the diaphragm. A liquid dispensing head characterized by the following features.

9. In the liquid dispensing head according to any one of claims 1 to 4, The diaphragm is formed from multiple layers, comprising a first layer containing Si, and a second layer containing Zr, located closer to the piezoelectric element than the first layer. The second layer includes at least one of Ta, Cr, Hf, Fe, and Pb. A liquid dispensing head characterized by the following features.

10. In the liquid dispensing head according to any one of claims 1 to 4, The thickness of the diaphragm is greater than the thickness of the piezoelectric element. A liquid dispensing head characterized by the following features.

11. In the liquid dispensing head according to any one of claims 1 to 4, The thickness of the diaphragm is 1.46 μm or more and 3.0 μm or less. A liquid dispensing head characterized by the following features.

12. In the liquid dispensing head according to any one of claims 1 to 4, The density of the diaphragm is higher than the density of the pressure chamber substrate. A liquid dispensing head characterized by the following features.

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