Patent Grant
11458730
The present application is based on, and claims priority from JP Application Serial Number 2020-034756, filed Mar. 2, 2020, the disclosure of which is hereby incorporated by reference herein in its entirety.
Embodiments of the present disclosure relate to a liquid ejecting head, an actuator, a liquid ejecting apparatus, and a method for manufacturing a liquid ejecting head.
In a piezoelectric-type liquid ejecting head of related art, a lower electrode, a piezoelectric layer, and an upper electrode are formed in layers in this order over a diaphragm. In order to prevent the development of a crack, etc. in a piezoelectric layer, a liquid ejecting head disclosed in JP-A-2016-58467 includes an upper electrode layer extending to an area for inhibiting the flexural deformation of the piezoelectric layer, a common metal layer extending to a position overlapping with this area, and a common adhesion layer extending to an end of the upper electrode layer beyond a position overlapping with the common metal layer. The thickness of the upper electrode layer is constant.
In the area for inhibiting the flexural deformation of the piezoelectric layer, an overlapping portion that overlaps with the upper electrode layer becomes distorted when a voltage is applied to the piezoelectric layer, whereas a non-overlapping portion that does not overlap with the upper electrode layer does not become distorted. In particular, the frequency of the distortional operation of the overlapping portion is high when the frequency of a drive pulse supplied from electrodes to the piezoelectric layer is high. For this reason, in the liquid ejecting head described above, the boundary between the overlapping portion and the non-overlapping portion in the piezoelectric layer is prone to cracking, etc.
The problem explained above occurs not only in liquid ejecting heads but also in various actuators and liquid ejecting apparatuses, etc. equipped with a piezoelectric layer.
A liquid ejecting head according to a certain aspect of the present disclosure is a liquid ejecting head that ejects liquid, comprising: a diaphragm; a first electrode; a piezoelectric layer; and a second electrode, wherein the diaphragm, the first electrode, the piezoelectric layer, and the second electrode are comprised in this order in a first direction, the second electrode includes a first portion that is next to the piezoelectric layer in the first direction and is electrically conductive, a length in the first direction is defined as a thickness, one position in a second direction intersecting with the first direction is defined as a first position, another one position is defined as a second position that is closer to an end of the second electrode in the second direction than the first position is, and when above definition is given, the thickness of the first portion at the second position is less than the thickness of the first portion at the first position.
A liquid ejecting apparatus according to a certain aspect of the present disclosure includes the liquid ejecting head described above and a control unit that controls operation of ejecting the liquid from the liquid ejecting head described above.
An actuator according to a certain aspect of the present disclosure includes: a diaphragm; a first electrode; a piezoelectric layer; and a second electrode, wherein the diaphragm, the first electrode, the piezoelectric layer, and the second electrode are comprised in this order in a first direction, the second electrode includes a first portion that is next to the piezoelectric layer in the first direction and is electrically conductive, a length in the first direction is defined as a thickness, one position in a second direction intersecting with the first direction is defined as a first position, another one position is defined as a second position that is closer to an end of the second electrode in the second direction than the first position is, and when above definition is given, the thickness of the first portion at the second position is less than the thickness of the first portion at the first position.
A method for manufacturing a liquid ejecting head according to a certain aspect of the present disclosure is a method for manufacturing a liquid ejecting head that includes a diaphragm, a first electrode, a piezoelectric layer, and a second electrode in this order in a first direction, wherein the second electrode includes a first portion that is next to the piezoelectric layer in the first direction and is electrically conductive, a plurality of positions in a second direction intersecting with the first direction includes a first position and a second position, the second position being closer to an end of the second electrode than the first position is, and the first portion includes a first conductive portion and a second conductive portion, the method comprising: a layering step of forming the first electrode and the piezoelectric layer in layers in this order over the diaphragm; a first conductive portion forming step of forming the first conductive portion that is next to the piezoelectric layer in the first direction; and a second conductive portion forming step of forming, at the first position, the second conductive portion that is next to the first conductive portion in the first direction, and not forming the second conductive portion at the second position.
Embodiments of the present disclosure will now be described. Of course, the embodiments are described below just for showing some examples of the present disclosure, and not all of the features described in the embodiments are necessarily indispensable to the solution provided by the present disclosure.
First, an overview of the technique included in the present disclosure is presented below.
In the present application, a numerical range “Min to Max” means a range of values equal to or greater than the minimum value Min and equal to or less than the maximum value Max. Compositional ratios expressed by chemical formulae represent stoichiometric proportion, and substances expressed by the chemical formulae include those deviating from the stoichiometric proportion.
As illustrated in
For example, the first portion P1 may include a first thickness portion T1, which is located at the first position L1 in the second direction (X-axis direction) intersecting with the first direction (+Z direction), and a second thickness portion T2, which is located at the second position L2 that is closer to the end E1 of the second electrode 34c in the second direction (X-axis direction) than the first position L1 is. In this instance, the second thickness portion T2 is thinner than the first thickness portion T1.
In the description below, a portion where the piezoelectric layer 34b and the second electrode 34c overlap with each other along the X-axis direction (the piezoelectric layer 34b and the second electrode 34c overlap with each other when viewed in the −Z direction) is referred to as the overlapping portion OL of the piezoelectric layer 34b. A portion where the piezoelectric layer 34b and the second electrode 34c do not overlap with each other along the X-axis direction (the piezoelectric layer 34b and the second electrode 34c do not overlap with each other when viewed in the −Z direction) is referred to as the non-overlapping portion NOL of the piezoelectric layer 34b. A voltage with a varying drive pulse is applied to the overlapping portion OL. Almost no voltage is applied to the non-overlapping portion NOL. If the thickness of the second electrode 34c is constant, the voltage applied to the piezoelectric layer 34b changes sharply at the boundary between the overlapping portion OL and the non-overlapping portion NOL. Such a sharp change in the voltage at the boundary is inferred to cause cracking, etc. in the piezoelectric layer 34b.
In the above embodiment of the disclosed technique, in which the second electrode 34c includes the first portion P1 that is electrically conductive, the thickness t2 of the first portion P1 at the second position L2 that is relatively near the end E1 of the second electrode 34c in the second direction (X-axis direction) intersecting with the first direction (+Z direction) (for example, the thickness of the second thickness portion T2) is less than the thickness t1 of the first portion P1 at the first position L1 that is relatively distant from the end E1 of the second electrode 34c in the second direction (X-axis direction) (for example, the thickness of the first thickness portion T1). Because of this structure, the electric resistance of the first portion P1 at the second position L2 (for example, the second thickness portion T2) is higher than that at the first position L1 (for example, the first thickness portion T1). Since the voltage level of a drive pulse changes, the voltage applied to the piezoelectric layer 34b is akin to an alternating-current voltage. Charging and discharging of electric charges are inhibited to some extent at the second position L2, at which the electric resistance is higher (for example, the second thickness portion T2), in the first portion P1. Therefore, in the piezoelectric layer 34b, the applied voltage in the neighborhood of the boundary between the overlapping portion OL and the non-overlapping portion NOL changes gently. For this reason, the above embodiment makes it possible to provide a liquid ejecting head that prevents a problem such as the development of a crack from occurring at the boundary between the overlapping portion and the non-overlapping portion in the piezoelectric layer 34b.
The second electrode 34c may further include a second portion P2 that is next to the first portion P1 in the first direction (+Z direction) and is less conductive than the first portion P1. The second portion P2, which is less conductive, serves as a structure component that prevents a crack, etc. from being developed in the piezoelectric layer 34b. Since the second electrode 34c includes the second portion P2, it is possible to more effectively prevent a problem such as the development of a crack from occurring at the boundary between the overlapping portion and the non-overlapping portion in the piezoelectric layer 34b. If the second portion P2 has a compressive stress, the second portion P2 is able to fulfill its function as a crack-preventing structure more effectively. The second electrode 34c may further include a third portion P3 that is next to the second portion P2 in the first direction (+Z direction) and is more conductive than the second portion P2.
As illustrated in
As illustrated in
An actuator 12 according to a certain embodiment of the disclosed technique includes the diaphragm 33, the first electrode 34a, the piezoelectric layer 34b, and the second electrode 34c in this order in the first direction (+Z direction). The second electrode 34c includes the first portion P1 that is next to the piezoelectric layer 34b in the first direction (+Z direction) and is electrically conductive. The thickness of the first portion P1 at the second position L2, denoted as t2, is less than the thickness of the first portion P1 at the first position L1, denoted as t1.
In the above embodiment of the disclosed technique, in which the second electrode 34c includes the first portion P1 that is electrically conductive, the thickness t2 of the first portion P1 at the second position L2 that is relatively near the end E1 of the second electrode 34c in the second direction (X-axis direction) intersecting with the first direction (+Z direction) (for example, the thickness of the second thickness portion T2) is less than the thickness t1 of the first portion P1 at the first position L1 that is relatively distant from the end E1 of the second electrode 34c in the second direction (X-axis direction) (for example, the thickness of the first thickness portion T1). Because of this structure, the electric resistance of the first portion P1 at the second position L2 (for example, the second thickness portion T2) is higher than that at the first position L1 (for example, the first thickness portion T1). Therefore, in the piezoelectric layer 34b, the applied voltage in the neighborhood of the boundary between the overlapping portion OL and the non-overlapping portion NOL changes gently. Therefore, the above embodiment makes it possible to provide an actuator that prevents a problem such as the development of a crack from occurring at the boundary between the overlapping portion and the non-overlapping portion in the piezoelectric layer.
As illustrated in
In the above embodiment of the disclosed technique, in which the second electrode 34c includes the first portion P1 that is electrically conductive, the second conductive portion CD2 does not exist at the second position L2 that is relatively near the end E1 of the second electrode 34c in the second direction (X-axis direction) intersecting with the first direction (+Z direction), and the thickness of the first portion P1 at the second position L2 is less than the thickness of the first portion P1 at the first position L1 that is relatively distant from the end E1 of the second electrode 34c in the second direction (X-axis direction). Because of this structure, the electric resistance of the portion of the second electrode 34c at the second position L2 is higher than that at the first position L1. Therefore, in the piezoelectric layer 34b, the applied voltage in the neighborhood of the boundary between the overlapping portion OL and the non-overlapping portion NOL changes gently. Therefore, the above embodiment makes it possible to provide a method for manufacturing a liquid ejecting head that prevents a problem such as the development of a crack from occurring at the boundary between the overlapping portion and the non-overlapping portion in the piezoelectric layer.
The meaning of “comprising: a diaphragm, a first electrode, a piezoelectric layer, and a second electrode in this order in a first direction” encompasses, but is not limited to, a case where there is a portion where the first electrode does not overlap with the diaphragm, a case where there is a portion where the piezoelectric layer does not overlap with the first electrode, and a case where there is a portion where the second electrode does not overlap with the piezoelectric layer.
The ordinal numbers such as “first”, “second”, and “third” used in the present application are terms for identifying and distinguishing, from one another, a plurality of components that have similarities. As such, these ordinal numbers are not intended to mean a sequential order.
The liquid ejecting apparatus 100 illustrated in
Liquid containers CT, in which the liquid LQ is contained, are mounted on the supply unit 14. A hard container made of a synthetic resin, a bag-type soft pack made of a flexible film, a liquid tank that can be replenished with the liquid LQ, or the like can be used as the liquid container CT. If the liquid LQ is ink, the hard container is called as an ink cartridge, and the soft pack is called as an ink pack. The supply unit 14 supplies the liquid LQ to the liquid ejecting head 10.
In accordance with control by the control unit 20, the liquid ejecting head 10 ejects the liquid LQ in the form of droplets DR from nozzles NZ. The liquid droplets DR are designed to be ejected in the −Z direction. If the medium MD is a print target, onto which printing is performed, the medium MD is a material that holds a plurality of dots DT formed by a plurality of liquid droplets DR. Paper, a synthetic resin, a cloth, metal, or the like can be used as the medium MD. The shape of the medium MD is not specifically limited. Examples of the shape of the medium MD are: a rectangular shape, a roll shape, a substantially circular shape, a polygonal shape other than a rectangle, a three-dimensional shape, etc. The liquid ejecting apparatus 100 is called as an ink-jet printer if configured to form a print image on the medium MD by ejecting ink droplets as the liquid droplets DR.
The term “liquid LQ” as used herein encompasses, but is not limited to, various kinds of liquid widely, for example, ink, a synthetic resin such as a photo-curable resin, an etchant, a living organism, and a lubricant. The term “ink” as used herein encompasses, but is not limited to, a wide variety of ink, for example, a solution in which dye is dissolved in a solvent, and a sol in which solid particles such as pigment or metal particles are dispersed in a dispersion medium.
In accordance with control by the control unit 20, the transportation unit 22 transports the medium MD in the +X direction. If the liquid ejecting apparatus 100 is a line printer, the plural nozzles NZ of the liquid ejecting head 10 are arranged throughout the entire width of the medium MD in the Y-axis direction. The liquid ejecting apparatus 100 may be equipped with a reciprocation drive unit that causes the liquid ejecting head 10 to move in the +Y direction and the −Y direction, as in a serial printer.
A circuit that includes, for example, a CPU or an FPGA, a ROM, a RAM, and the like may be used as the control unit 20. CPU is an acronym for Central Processing Unit. FPGA is an acronym for Field Programmable Gate Array. ROM is an acronym for Read Only Memory. RAM is an acronym for Random Access Memory. A circuit that includes “System on a Chip”, which is abbreviated as SoC, may be used as the control unit 20. By controlling each component included in the liquid ejecting apparatus 100, the control unit 20 controls the operation of ejecting the liquid droplets DR from the liquid ejecting head 10.
If the liquid ejecting apparatus 100 is an ink-jet printer, a plurality of dots DT is formed on the medium MD when a plurality of liquid droplets DR ejected from the liquid ejecting head 10 lands onto the surface of the medium MD, which is transported by the transportation unit 22, A print image is formed on the medium MD as a result of this operation.
The liquid ejecting head 10 illustrated in
The nozzle substrate 41 is a plate-like member bonded to the −Z-directional end surface 31f of the communication substrate 31. The nozzle substrate 41 has the plurality of nozzles NZ from which the liquid LQ is ejected. The nozzle substrate 41 illustrated in
A liquid-repellent coat that has liquid repellency may be provided on the nozzle surface 41a. The liquid-repellent coat is not specifically limited as long as it is repellent to liquid. For example, a metal film that includes a fluorine polymer, a molecular film of metalalkoxide that has liquid repellency, etc., may be used as the liquid-repellent coat.
The compliance substrate 42 is bonded to the surface 31f of the communication substrate 31 outside the nozzle substrate 41. The compliance substrate 42 illustrated in
The communication substrate 31 is provided over the nozzle substrate 41 and the compliance substrate 42 and under the pressure compartment substrate 32 and the housing member 36. The pressure compartment substrate 32 and the housing member 36 are bonded to the +Z-directional end surface 31h of the communication substrate 31. The communication substrate 31 has the space Ra common to the plurality of nozzles NZ, the relay liquid chamber 31c common to the plurality of nozzles NZ, supply holes 31a separated from one another individually to correspond to the nozzles NZ, and the communication holes 31b separated from one another individually to correspond to the nozzles NZ. The space Ra has a shape of an elongated cavity whose longer-side direction is along the Y axis. The relay liquid chamber 31c is an elongated space whose longer-side direction is along the Y axis. The space Ra, which is common to the plurality of nozzles NZ, is in communication with the plurality of supply holes 31a through the relay liquid chamber 31c. The communication substrate 31 illustrated in
The communication substrate 31 may be made of one or more kinds of material selected from the group including, for example, a silicon substrate, metal, ceramics, and the like. The communication substrate 31 is manufactured by, for example, processing a monocrystalline silicon substrate by using a semiconductor manufacturing technology such as photolithography and etching, etc. Of course, however, known materials and methods can be used for manufacturing the communication substrate 31.
The pressure compartment substrate 32 includes the plurality of pressure compartments Cl for applying, to the liquid LQ, pressure for ejecting the liquid LQ from the nozzles NZ. The pressure compartment substrate 32 includes the diaphragm 33 and the piezoelectric elements 34 on a surface that is the opposite of a surface facing the communication substrate 31. Of the pressure compartment substrate 32, the −Z-directional portion relative to the diaphragm 33 is hereinafter referred to as a pressure compartment substrate body portion 32a.
The pressure compartment substrate body portion 32a is bonded to the +Z-directional end surface 31h of the communication substrate 31. The pressure compartment substrate body portion 32a includes the plurality of pressure compartments Cl separated from one another individually to correspond to the nozzles NZ. Each of the plurality of pressure compartments Cl is located between the nozzle substrate 41 and the diaphragm 33 and is configured as a rectangular space whose longer-side direction is along the Y axis. The pressure compartment substrate body portion 32a includes two pressure-compartment rows, each of which is made up of a plurality of pressure compartments Cl arranged linearly in the Y-axis direction. Each of the plurality of pressure compartments Cl is in communication with the corresponding one of the plurality of supply holes 31a at its one end in the longer-side direction and is in communication with the corresponding one of the plurality of communication holes 31b at its opposite end in the longer-side direction.
The pressure compartment substrate body portion 32a may be made of one or more kinds of material selected from the group including, for example, a silicon substrate, metal, ceramics, and the like. The pressure compartment substrate body portion 32a is manufactured by, for example, processing a monocrystalline silicon substrate by using a semiconductor manufacturing technology such as photolithography and etching, etc. In this instance, if a silicon oxide layer is formed on the surface of a monocrystalline silicon substrate by thermal oxidation, etc., it is possible to use the silicon oxide layer as the diaphragm 33. Of course, however, known materials and methods can be used for manufacturing the pressure compartment substrate body portion 32a.
The diaphragm 33 integrated with the pressure compartment substrate body portion 32a has elasticity and constitutes a part of the wall surfaces of each compartment Cl. The diaphragm 33 may be made of one or more kinds of material selected from the group including, for example, silicon oxide symbolized as SiOx, metal oxide, ceramics, a synthetic resin, and the like. The symbol SiOx according to its stoichiometric proportion represents silicon dioxide SiO2; however, the subscript may be actually deviated from x=2. It is possible to form the diaphragm 33 by using, for example, thermal oxidation, a physical vapor growth method including sputtering, a vacuum deposition method including CVD, a liquid-phase method including spin coating, or the like. CVD is an acronym for Chemical Vapor Deposition.
The diaphragm 33 may include a plurality of layers, for example, an elastic layer 33a and an insulating layer 33b, as illustrated in
Of course, the material of the diaphragm 33 is not limited to the above example. For example, the diaphragm 33 may be made of silicon nitride symbolized as SiNx, titanium oxide symbolized as TiOx, aluminum oxide symbolized as AlOx, hafnium oxide symbolized as HfOx, magnesium oxide symbolized as MgOx, lanthanum aluminum oxide, or the like.
The piezoelectric elements 34, which are individually driven separately from one another to correspond to the pressure compartments Cl, are provided integrally on the +Z-directional end surface of the diaphragm 33. The piezoelectric element 34 and the diaphragm 33 are included in the actuator 12 that applies pressure to the pressure compartment Cl. The pressure compartment substrate 32 illustrated in
The first electrode 34a, the first portion P1 of the second electrode 34c, the third portion P3 of the second electrode 34c, and the third electrode 37 may be made of a conductive material such as, for example, metal such as iridium or platinum, conductive metal oxide such as indium tin oxide symbolized as ITO, or the like. If an electrode is made of iridium, the principal component of the electrode is iridium. In this instance, the electrode may be substantially made of iridium except for impurities or may contain a secondary component whose content is less than the content of the principal component. The thickness of the first electrode 34a is not specifically limited. The thickness of the first electrode 34a may be, for example, approximately 50 to 300 nm.
For example, TiOx, tantalum oxide symbolized as TaOx, AlOx, ZrOx, SiOx, or the like can be used as the material of the second portion P2 of the second electrode 34c.
If the second portion P2 is made of TiOx, the principal component of the second portion P2 is TiOx. In this instance, the second portion P2 may be substantially made of TiOx except for impurities or may contain a secondary component whose content is less than the content of the principal component. The symbol TiOx according to its stoichiometric proportion represents titanium dioxide TiO2; however, the subscript may be actually deviated from x=2.
If the second portion P2 is made of TaOx, the principal component of the second portion P2 is TaOx. In this instance, the second portion P2 may be substantially made of TaOx except for impurities or may contain a secondary component whose content is less than the content of the principal component. The symbol TaOx according to its stoichiometric proportion represents tantalum pentoxide Ta2O5; however, the subscript value may be actually deviated from x=2.5.
If the second portion P2 is made of AlOx, the principal component of the second portion P2 is AlOx. In this instance, the second portion P2 may be substantially made of AlOx except for impurities or may contain a secondary component whose content is less than the content of the principal component. The symbol AlOx according to its stoichiometric proportion represents aluminum trioxide Al2O3; however, the subscript value may be actually deviated from x=1.5.
If the second portion P2 is made of ZrOx, the principal component of the second portion P2 is ZrOx. In this instance, the second portion P2 may be substantially made of ZrOx except for impurities or may contain a secondary component whose content is less than the content of the principal component. The symbol ZrOx according to its stoichiometric proportion represents zirconium dioxide ZrO2; however, the subscript may be actually deviated from x=2.
If the second portion P2 is made of SiOx, the principal component of the second portion P2 is SiOx. In this instance, the second portion P2 may be substantially made of SiOx except for impurities or may contain a secondary component whose content is less than the content of the principal component. The symbol SiOx according to its stoichiometric proportion represents silicon dioxide SiO2; however, the subscript may be actually deviated from x=2.
The piezoelectric layer 34b may be made of a material that has a perovskite structure, etc., for example, lead zirconate titanate symbolized as PZT, relaxor ferroelectrics obtained by adding metal such as niobium or nickel, etc. to PZT, lead-free perovskite-type oxide such as a BiFeOx—BaTiOy piezoelectric material, etc. The thickness of the piezoelectric layer 34b is not specifically limited. The thickness of the piezoelectric layer 34b may be, for example, approximately 0.7 to 5 μm.
The protective substrate 35 includes a space 35a for protecting the plurality of piezoelectric elements 34. The protective substrate 35 further includes a through hole 35b through which the wiring substrate 51 is routed out. The protective substrate 35 is bonded to the +Z-directional end surface of the diaphragm 33. The protective substrate 35 bonded thereto enhances the mechanical strength of the pressure compartment substrate 32. The protective substrate 35 may be made of one or more kinds of material selected from the group including, for example, a silicon substrate, metal, ceramics, a synthetic resin, and the like. The protective substrate 35 is manufactured by, for example, processing a monocrystalline silicon substrate by using a semiconductor manufacturing technology such as photolithography and etching, etc. Of course, however, known materials and methods can be used for manufacturing the protective substrate 35.
The housing member 36 is bonded to the +Z-directional end surface 31h of the communication substrate 31 outside the pressure compartment substrate 32 and the protective substrate 35. The housing member 36 illustrated in
The wiring substrate 51 is a flexible mount component that includes a drive circuit for driving the piezoelectric elements 34. The wiring substrate 51 is connected to the +Z-directional end surface of the diaphragm 33 between the piezoelectric-element rows. The connection portion of the wiring substrate 51 to the diaphragm 33 is connected to the first electrode 34a and the second electrode 34c via lead wires 52 illustrated in
As described above, the liquid LQ that flows out of the liquid container CT flows through the supply inlet 36a, the liquid reservoir RS, the relay liquid chamber 31c, the individual supply hole 31a, the individual pressure compartment Cl, the individual communication hole 31b, and the individual nozzle NZ in this order. When the piezoelectric element 34 is driven to cause the pressure compartment Cl to contract, the liquid droplet DR is ejected from the nozzle NZ in the −Z direction.
As illustrated in
In order to prevent cracking, etc. described above from occurring, it is conceivable that a liquid adhesive for bonding the protective substrate 35 to the diaphragm 33 is applied from a region on the non-overlapping portion NOL to the second electrode 34c over the overlapping portion OL of the piezoelectric layer 34b. The applied adhesive, after curing or solidification, serves as a crack-preventing structure. However, the adhesive might not be able to be applied stably because it is necessary to apply the adhesive, which is a fluid, to a region from the piezoelectric layer 34b to the second electrode 34c.
An alternative conceivable approach is to make a portion that is in contact with the boundary between the overlapping portion OL and the non-overlapping portion NOL, of each first electrode 34a, narrower. Making this portion narrower reduces a portion where distortional operation occurs at the overlapping portion OL in the neighborhood of the boundary in the piezoelectric layer 34b. However, even if a portion where distortional operation occurs is reduced, the fact remains that it is prone to cracking, etc.
Another alternative conceivable approach is to form a wiring pattern that bypasses the boundary between the overlapping portion OL and the non-overlapping portion NOL for each first electrode 34a. If this approach is taken, a space for forming the wiring pattern that bypasses the boundary on the diaphragm 33 is necessary.
Still another alternative conceivable approach is to form a protective film such as a film of AlOx from a region on the non-overlapping portion NOL to the second electrode 34c over the overlapping portion OL of the piezoelectric layer 34b. If this approach is taken, there is a possibility that the piezoelectric layer 34b might be deteriorated in the process of forming the protective film on the non-overlapping portion NOL where the piezoelectric layer 34b is exposed.
To provide a solution, in the specific example described here, the first portion P1 of the second electrode 34c, which is a conductive portion that is next to the piezoelectric layer 34b in the +Z direction, is configured to be thin in the neighborhood of the end E1 of the second electrode 34c. This structure prevents a problem such as the development of a crack from occurring. With reference to
As illustrated in
As illustrated in
As illustrated in
In the specific example described here, the +Z direction is an example of a first direction, and the X-axis direction is an example of a second direction intersecting with the first direction. Therefore, the first portion P1 includes the first thickness portion T1, which is located at the first position L1 in the second direction intersecting with the first direction, and the second thickness portion T2, which is located at the second position L2 that is closer to the end E1 of the second electrode 34c in the second direction than the first position L1 is. The second thickness portion T2 is thinner than the first thickness portion T1. Because of this structure, the electric resistance of the second thickness portion T2, which is relatively near the end E1, is higher than that of the first thickness portion T1. That is, the electric resistance of the first portion P1 at the second position L2 is higher than that at the first position L1. Since the voltage level of a drive pulse changes, the voltage applied to the piezoelectric layer 34b is akin to an alternating-current voltage. Charging and discharging of electric charges are inhibited to some extent by the second thickness portion T2, the electric resistance of which is higher, that is, at the second position L2 in the first portion P1. Therefore, in the pressure compartment non-corresponding area AC0 of the piezoelectric layer 34b, the applied voltage in the neighborhood of the boundary between the overlapping portion OL and the non-overlapping portion NOL changes gently. Therefore, the change in distortion at the boundary between the overlapping portion OL and the non-overlapping portion NOL in the piezoelectric layer 34b is gentle. This prevents a problem such as the development of a crack from occurring at the boundary between the overlapping portion OL and the non-overlapping portion NOL.
In the second electrode 34c, the second portion P2, which is less conductive than the first portion P1, is next to the first portion P1 in the +Z direction. For example, if the principal component of the second portion P2 is TiOx or TaOx, the second portion P2 is less conductive than the first portion P1. It will be advantageous if the second portion P2 is made of an insulating substance such as TiOx, AlOx, SiOx, or the like. The second portion P2 exists at the second position L2, which is relatively near the end E1 of the second electrode 34c, and does not exist at the first position L1. If the second portion P2 is less conductive than the first portion P1, the electric resistance of a layered portion made up of the second portion P2 and the second thickness portion T2 in the first portion P1 is determined mainly depending on the electric resistance of the second thickness portion T2. Due to the higher electric resistance of the second thickness portion T2, in the pressure compartment non-corresponding area AC0 of the piezoelectric layer 34b, the applied voltage in the neighborhood of the boundary between the overlapping portion OL and the non-overlapping portion NOL changes gently. This prevents a problem such as the development of a crack from occurring at the boundary between the overlapping portion OL and the non-overlapping portion NOL in the piezoelectric layer 34b. Moreover, since the second portion P2 located at the second position L2 serves as a structure component that enhances the strength of the piezoelectric layer 34b, it is possible to effectively prevent a problem such as the development of a crack from occurring at the boundary between the overlapping portion OL and the non-overlapping portion NOL.
It will be advantageous if the Young's modulus of the second portion P2, which is less conductive, is greater than that of the first portion P1, which is more conductive. For example, if the principal component of the first portion P1 is iridium and the principal component of the second portion P2 is TiOx, the second portion P2 has a greater Young's modulus than the first portion P1. If the second portion P2 has a greater Young's modulus than the first portion P1, it is possible to effectively prevent a problem such as the development of a crack from occurring at the boundary between the overlapping portion OL and the non-overlapping portion NOL in the piezoelectric layer 34b.
It will be advantageous if the Young's modulus of the second portion P2 is greater than that of the third portion P3, which is more conductive. For example, if the principal component of the third portion P3 is iridium and the principal component of the second portion P2 is TiOx, the second portion P2 has a greater Young's modulus than the third portion P3.
It will be advantageous if the second portion P2, which is less conductive, has a compressive stress. For example, if the second portion P2 is an oxide film such as TiOx, TaOx, AlOx, ZrOx, or SiOx, etc., the second portion P2 has a compressive stress. An oxide film of these kinds is compressively stressed strongly if formed by thermal oxidation of a metal film. The piezoelectric layer 34b is prone to cracking when a force is applied in a direction of contracting in the X-axis direction due to the distortional operation of the overlapping portion OL. The second portion P2 that has a compressive stress applies a force for widening the layer-boundary surface of the piezoelectric layer 34b in the X-axis direction through the first portion P1. Therefore, the contraction of the piezoelectric layer 34b in the X-axis direction is suppressed. For this reason, if the second portion P2 has a compressive stress, it is possible to effectively prevent a problem such as the development of a crack from occurring at the boundary between the overlapping portion OL and the non-overlapping portion NOL in the piezoelectric layer 34b.
As illustrated in
In the second electrode 34c, the third portion P3, which is more conductive than the second portion P2, exists at the second position L2, which is relatively near the end E1 of the second electrode 34c, and does not exist at the first position L1. The third portion P3 is next to the second portion P2 in the +Z direction. For example, if the principal component of the third portion P3 is iridium, the third portion P3 is more conductive than the second portion P2. Furthermore, if the third portion P3 is thicker than the second thickness portion T2 in the first portion P1, the conductive property of the first thickness portion T1 in the first portion P1 is substantially equal to the conductive property of the third portion P3. The substantial equality between the conductive property of the first thickness portion T1 and the conductive property of the third portion P3 mentioned here means that a ratio of the electric conductivity of the third portion P3 to the electric conductivity of the first thickness portion T1 is 0.8 or higher and 1.2 or lower.
In the specific example described here, the principal component of the first portion P1 is the same as the principal component of the third portion P3. Of course, the principal component of the third portion P3 may be the same as the principal component of the second thickness portion T2 in the first portion P1 or may be different therefrom. For example, it is possible to choose a certain kind of precious metal such as iridium or platinum as the principal component of the second thickness portion T2, which is next to the piezoelectric layer 34b in the +Z direction, and choose a certain kind of low-cost metal such as aluminum or tungsten as the principal component of the third portion P3, which is away from the piezoelectric layer 34b. Even if these materials are used, it is possible to sufficiently set the second electrode 34c, which is next to the piezoelectric layer 34b in the +Z direction, at a reference level and thus apply a drive pulse with an appropriate voltage to the piezoelectric layer 34b. Therefore, it is possible to reduce the cost of the liquid ejecting head 10.
As illustrated in
At the second position L2 where the second thickness portion T2 in the first portion P1 exists, the second electrode 34c includes the first portion P1, the second portion P2 formed on the first portion P1, and the third portion P3 formed on the second portion P2 in this order in the +Z direction. Since the second thickness portion T2 is thinner than the first thickness portion T1, the electric resistance of the second thickness portion T2 is higher than that of the first thickness portion T1, making the change in distortion at the boundary between the overlapping portion OL and the non-overlapping portion NOL in the piezoelectric layer 34b gentle. Moreover, since the second portion P2, which is less conductive, is formed on the second thickness portion T2, the second portion P2 serves as a structure component that enhances the strength of the piezoelectric layer 34b.
A third thickness portion T3 located at the second position L2 in the third portion P3 illustrated in
The thickness t1 of the first thickness portion T1 in the first portion P1 of the second electrode 34c may be approximately 15 to 30 nm. The thickness t2 of the second thickness portion T2 in the first portion P1 of the second electrode 34c may be approximately 3 to 6 nm. The thickness tp2 of the second portion P2 of the second electrode 34c may be approximately 10 to 50 nm. The thickness t3 of the third portion P3 of the second electrode 34c may be approximately 9 to 27 nm.
In the second electrode 34c illustrated in
As illustrated in
As described above, when a predetermined voltage is applied between the first electrode 34a and the second electrode 34c, the amount of distortion of the piezoelectric layer 34b at the second position L2 is smaller than the amount of distortion of the piezoelectric layer 34b at the first position L1 and is larger than the amount of distortion of the piezoelectric layer 34b at the third position L3. Since this suppresses a sharp change in distortion at the boundary between the overlapping portion OL and the non-overlapping portion NOL in the piezoelectric layer 34b, a problem such as the development of a crack is unlikely to occur at the boundary between the overlapping portion OL and the non-overlapping portion NOL.
The actuator 12 illustrated in
In the process of forming the second portion P2, which is less conductive, it is possible to form a portion that is less conductive in the third electrode 37, too.
The continuing portion 38 of the third electrode 37 illustrated in
The thickness t5 of the fourth portion P4 of the continuing portion 38 is substantially equal to the thickness t2 of the first portion P1 of the second electrode 34c. The thickness tp5 of the fifth portion P5 of the continuing portion 38 is substantially equal to the thickness tp2 of the second portion P2 of the second electrode 34c. Similarly to the second portion P2 of the second electrode 34c, for example, TiOx, TaOx, AlOx, ZrOx, or SiOx, etc. can be used as the material of the fifth portion P5, which is less conductive. The thickness t6 of the sixth portion P6 of the continuing portion 38 is substantially equal to the thickness t3 of the third portion P3 of the second electrode 34c. When it is stated that the thickness of a certain portion is equal to the thickness of another portion, the statement means that a ratio therebetween is 0.8 or higher and 1.2 or lower.
The fourth portion P4 of the continuing portion 38 has conductive property that is substantially equal to the conductive property of the second thickness portion T2 in the first portion P1 of the second electrode 34c, and is next to the piezoelectric layer 34b in the +Z direction. The fourth portion P4 is thin, similarly to the second thickness portion T2 of the second electrode 34c. Therefore, the electric resistance of the fourth portion P4 is higher than that of the first thickness portion T1 in the first portion P1 of the second electrode 34c. The higher electric resistance of the fourth portion P4 prevents migration, a phenomenon of an electric current flow between the second electrode 34c and the third electrode 37, from occurring.
The fifth portion P5 of the continuing portion 38 is less conductive than the fourth portion P4 and is next to the fourth portion P4 in the +Z direction. For example, if the principal component of the fifth portion P5 is TiOx or TaOx, the fifth portion P5 is less conductive than the fourth portion P4. It will be advantageous if the fifth portion P5 is made of an insulating substance such as TiOx, AlOx, SiOx, or the like. Since the continuing portion 38 of the third electrode 37 has the fifth portion P5, which is less conductive, electric field intensity between the second electrode 34c and the third electrode 37 decreases, and migration, a phenomenon of an electric current flow between the second electrode 34c and the third electrode 37, is prevented effectively. In particular, since the distance between the fifth portion P5 and the second electrode 34c is shorter than the distance between the lead wire 52b and the second electrode 34c in the X-axis direction, the migration mentioned here is prevented effectively.
The sixth portion P6 of the continuing portion 38 has conductive property that is substantially equal to the conductive property of the third portion P3 of the second electrode 34c, and is next to the fifth portion P5 in the +Z direction. Since the lead wire 52b is next to the sixth portion P6 in the +Z direction, wiring for supplying a drive signal to the piezoelectric layer 34b through the third electrode 37 and the first electrode 34a is formed efficiently.
The principal component of the sixth portion P6 may be the same as the principal component of the fourth portion P4 or may be different therefrom. For example, it is possible to choose a certain kind of precious metal such as iridium or platinum as the principal component of the fourth portion P4, which is next to the piezoelectric layer 34b in the +Z direction, and choose a certain kind of low-cost metal such as aluminum or tungsten as the principal component of the sixth portion P6, which is away from the piezoelectric layer 34b.
The pressure compartment substrate 32 is produced from a silicon wafer made of monocrystalline silicon. First, as illustrated in
Next, a layering step is performed. As illustrated in
Next, as illustrated in
Next, as illustrated in
The second portion P2 for preventing a crack from being developed in the piezoelectric layer 34b is not formed directly on the piezoelectric layer 34b but formed on the first conductive portion CD1, thereby being distanced from the piezoelectric layer 34b in the +Z direction. Therefore, degradation that might occur if a protective film were formed directly on the piezoelectric layer 34b is prevented.
Next, as illustrated in
The second portion P2, which is less conductive, exists at the second position L2 and does not exist at the first position L1. Therefore, in the second conductive portion forming step, the second conductive portion CD2 that is next to the first conductive portion CD1 in the +Z direction is formed at the first position L1, and the second conductive portion CD2 is not formed at the second position L2. The third portion P3, which is next to the second portion P2 in the +Z direction, is formed at the second position L2 in the second conductive portion forming step.
Next, a lead wire forming step, in which the lead wires 52 are formed as illustrated in
Next, a protective substrate bonding step, in which the protective substrate 35 illustrated in
Next, a pressure compartment substrate forming step, in which the pressure compartment substrate 32 before division is formed from the pressure compartment substrate wafer 132, is performed. The pressure compartment substrate forming step includes a thinning step, a pressure compartment forming step, and a dividing step. In the thinning step, the pressure compartment substrate wafer 132 is made thinner into a predetermined thickness by applying a thinning treatment thereto from the side that is the opposite of the side where the protective substrate 35 is provided. In the pressure compartment forming step, the pressure compartments Cl are formed in the thinned pressure compartment substrate wafer 132. In the dividing step, the pressure compartment substrate 32 and the protective substrate 35 are cut into a chip size. One or more kinds of method selected from the group including, for example, grinding, dry etching such as plasma etching, wet etching, CMP, and the like can be used for reducing the thickness of the pressure compartment substrate wafer 132. CMP is an acronym for Chemical Mechanical Polishing. The method for forming the pressure compartments Cl in the thinned pressure compartment substrate wafer 132 is not specifically limited. For example, the pressure compartments Cl are formed with high precision by, through a mask, performing anisotropic etching of the pressure compartment substrate wafer 132 from the side that is the opposite of the side where the protective substrate 35 is provided. Alkaline solution such as potassium hydroxide solution can be used as an etchant. Of course, dry etching such as plasma etching may be used instead of wet etching for forming the pressure compartments Cl. In the dividing step, unnecessary parts of the pressure compartment substrate 32 and the protective substrate 35 are removed.
Next, a communication substrate bonding step is performed. In the communication substrate bonding step, the communication substrate 31, which has liquid flow passages, including the supply holes 31a, the communication holes 31b, and the relay liquid chamber 31c, is bonded to the pressure compartment substrate 32. The communication substrate 31 can be manufactured from a communication substrate wafer, which is, for example, a silicon wafer. The method for forming liquid flow passages in the communication substrate wafer is not specifically limited. For example, the relay liquid chamber 31c is formed by etching the communication substrate wafer through a first mask, and the supply holes 31a and the communication holes 31b are formed by etching the communication substrate wafer through a second mask. The etching may be wet etching or dry etching. The communication substrate 31 is bonded to the pressure compartment substrate body portion 32a by using, for example, an adhesive. Normal-temperature activation bonding, plasma activation bonding, etc. may be used for bonding the communication substrate 31 to the pressure compartment substrate 32.
After the step described above, a nozzle substrate bonding step, in which the nozzle substrate 41 is bonded to the −Z-directional end surface 31f of the communication substrate 31, is performed. The nozzle substrate 41 can be manufactured from a nozzle substrate wafer, which is, for example, a silicon wafer. The method for forming the nozzles NZ in the nozzle substrate wafer is not specifically limited. For example, the nozzles NZ are formed by etching the nozzle substrate wafer through a mask. For example, the nozzle substrate 41 is bonded to the surface 31f of the communication substrate 31 by using an adhesive.
A compliance substrate bonding step, in which the compliance substrate 42 is bonded to the −Z-directional end surface 31f of the communication substrate 31, is further performed. For example, the compliance substrate 42 is bonded to the surface 31f of the communication substrate 31 by using an adhesive.
A housing member bonding step, in which the housing member 36 is bonded to the +Z-directional end surface 31h of the communication substrate 31, is further performed. For example, the housing member 36 is bonded to the surface 31h of the communication substrate 31 by using an adhesive.
A wiring substrate connection step, in which the wiring substrate 51 is connected to the lead wires 52, is further performed.
The liquid ejecting head 10 including the actuator 12 illustrated in
The manufacturing method described above may be modified as needed, for example, by changing the order of the steps. For example, the wiring substrate connection step may be performed before the housing member bonding step.
The piezoelectric element 34, in which the second thickness portion T2 located at the second position L2 closer to the end E1 of the second electrode 34c is thinner than the first thickness portion T1 located at the first position L1 in the first portion P1 of the second electrode 34c, is manufactured using the manufacturing method described above. Therefore, the manufacturing method according to the specific example described here makes it possible to provide an advantageous example of manufacturing the liquid ejecting head 10 and the liquid ejecting apparatus 100 for preventing a problem such as the development of a crack from occurring at the boundary between the overlapping portion OL and the non-overlapping portion NOL in the piezoelectric layer 34b.
As illustrated in
The second portion P2 for preventing a crack from being developed in the piezoelectric layer 34b, and the fifth portion P5 for preventing migration from occurring, are not formed directly on the piezoelectric layer 34b but formed on the first conductive portion CD1, thereby being distanced from the piezoelectric layer 34b in the +Z direction. Therefore, degradation that might occur if a protective film were formed directly on the piezoelectric layer 34b is prevented.
Next, as illustrated in
Since the continuing portion 38 of the third electrode 37 has the fifth portion P5, which is less conductive, electric field intensity between the second electrode 34c and the third electrode 37 decreases, and migration, a phenomenon of an electric current flow between the second electrode 34c and the third electrode 37, is prevented effectively.
Next, the lead wire forming step, which includes the lead wire stacking step and the patterning step, is performed. It is possible to form the lead wires 52 by, for example, depositing a film of metal such as gold. A physical vapor growth method, etc. can be used for depositing the film of metal. Lithography, etc. can be used for the patterning. By going through the lead wire forming step, the lead wire 52a is stacked on a part of the second electrode 34c, and the lead wire 52b is stacked on a part of the third electrode 37 such that the distance between the fifth portion P5 and the second electrode 34c is shorter than the distance between the lead wire 52b and the second electrode 34c in the X-axis direction. This prevents the migration described earlier effectively.
After the above step, the protective substrate bonding step of bonding the protective substrate 35 illustrated in
The liquid ejecting head 10 including the actuator 12 illustrated in
The specific example illustrated in
A printer as an example of a liquid ejecting apparatus includes, for example, a copier, a facsimile, a multi-function peripheral, and the like, besides a print-only machine. Of course, the liquid ejecting apparatus is not limited to a printer.
Liquid ejected from a fluid ejecting head encompasses, but is not limited to, fluid such as a solution in which a solute such as dye is dissolved in a solvent, a sol in which solid particles such as pigments or metal particles are dissolved in a dispersion medium, and the like. Such liquid encompasses, but is not limited to, a solution of ink, liquid crystal, a conductive material, a living organism, and the like. The liquid ejecting apparatus includes, for example, an apparatus for manufacturing a color filter for a liquid crystal display, etc., an apparatus for manufacturing electrodes for an organic EL display, etc., a biochip manufacturing apparatus, a manufacturing apparatus for forming the wiring of a wiring substrate, etc. The organic EL mentioned here is an abbreviation for organic electroluminescence.
In the specific example described above, the second electrode 34c is a common electrode that is common to the plurality of nozzles NZ. However, the disclosed technique may be applied to a configuration in which the second electrode is an individual electrode. If the second electrode is an individual electrode, the first electrode may be a common electrode that is common to the plurality of nozzles NZ, and/or the piezoelectric layer may be common to the plurality of nozzles NZ.
The actuator 12 disclosed in the specific example described above may be applied to devices such as, for example, an ultrasonic wave oscillator, an ultrasonic motor, a piezoelectric transformer, a piezoelectric speaker, a piezoelectric pump, a pressure-electricity converter, and the like.
As explained above, the present disclosure with various embodiments makes it possible to provide a technique of an actuator, a liquid ejecting head, a liquid ejecting apparatus, etc. that prevents a problem such as the development of a crack from occurring at the boundary between an overlapping portion and a non-overlapping portion in a piezoelectric layer. Of course, basic operations and basic effects described above can be obtained also from a technique that is made up of only elements of an independent claim.
The present disclosure may be implemented in a configuration obtained by replacing any of components disclosed in the foregoing examples with each other or one another or changing a combination thereof, in a configuration obtained by replacing any of components disclosed in the foregoing examples and known art with each other or one another or changing a combination thereof, and the like. These configurations, etc. are also within the scope of the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2020-034756 | Mar 2020 | JP | national |
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| 20210268798 A1 | Sep 2021 | US |
