US20140210916A1 - Liquid ejection head and liquid ejection apparatus - Google Patents
Liquid ejection head and liquid ejection apparatus Download PDFInfo
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- US20140210916A1 US20140210916A1 US14/244,250 US201414244250A US2014210916A1 US 20140210916 A1 US20140210916 A1 US 20140210916A1 US 201414244250 A US201414244250 A US 201414244250A US 2014210916 A1 US2014210916 A1 US 2014210916A1
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- pressure generating
- piezoelectric layer
- liquid ejection
- generating chamber
- piezoelectric
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Images
Classifications
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- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
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- B41J2/14233—Structure of print heads with piezoelectric elements of film type, deformed by bending and disposed on a diaphragm
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- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/015—Ink jet characterised by the jet generation process
- B41J2/04—Ink jet characterised by the jet generation process generating single droplets or particles on demand
- B41J2/045—Ink jet characterised by the jet generation process generating single droplets or particles on demand by pressure, e.g. electromechanical transducers
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
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- B41J2/161—Production of print heads with piezoelectric elements of film type, deformed by bending and disposed on a diaphragm
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
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- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/704—Piezoelectric or electrostrictive devices based on piezoelectric or electrostrictive films or coatings
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/87—Electrodes or interconnections, e.g. leads or terminals
- H10N30/871—Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
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- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
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- B41J2/135—Nozzles
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- B41J2002/14258—Multi layer thin film type piezoelectric element
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
- B41J2/00—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
- B41J2/005—Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by bringing liquid or particles selectively into contact with a printing material
- B41J2/01—Ink jet
- B41J2/135—Nozzles
- B41J2/14—Structure thereof only for on-demand ink jet heads
- B41J2002/14491—Electrical connection
Definitions
- the present invention relates to liquid ejection heads and liquid ejection apparatuses.
- JP-A-2009-172878 and JP-A-2009-196329 disclose a liquid ejection head including a substrate in which a pressure generating chamber that communicates with a nozzle opening for ejecting liquid is formed, and a piezoelectric element having a piezoelectric layer, a lower electrode that is formed on the lower side of the piezoelectric layer and an upper electrode that is formed on the upper side of the piezoelectric layer.
- the lower electrode is provided as an individual electrode that corresponds to each of the pressure generating chambers
- the upper electrode is provided as a common electrode for a plurality of piezoelectric elements that correspond to a plurality of pressure generating chambers.
- the above-mentioned piezoelectric element displaces when a voltage is applied across both electrodes and flexes into the pressure generating chamber.
- a significant amount of stress is generated at the interface between an area on the piezoelectric element where the upper electrode, the piezoelectric layer and the lower electrode overlap (active section) and an area other than the active section (inactive section), which causes distortion to be concentrated at this position. Since concentration of distortion may cause a problem such as crack in the piezoelectric layer that forms the piezoelectric element, it has been required to prevent such a problem.
- An advantage of some aspects of the invention is that a liquid ejection head capable of preventing or reducing a problem such as cracking in a piezoelectric layer and increasing the amount of liquid to be ejected, and a liquid ejection apparatus having the same are provided.
- a liquid ejection head includes: a substrate in which a pressure generating chamber that communicates with a nozzle opening is formed; and a piezoelectric element having a piezoelectric layer, a first electrode that is formed on a surface of the piezoelectric layer on a side of the substrate so as to correspond to the pressure generating chamber, and a second electrode that is formed on a surface of the piezoelectric layer opposite to the side on which the first electrode is formed so as to extend over a plurality of the pressure generating chambers, wherein the second electrode is formed to extend to an outside of the pressure generating chamber in a longitudinal direction of the pressure generating chamber.
- the second electrode is formed to extend to the outside of the pressure generating chamber in the longitudinal direction of the pressure generating chamber. Accordingly, concentration of distortion at the interface on the piezoelectric element is reduced compared to the case in which the second electrode is formed not to extend to the outside of the pressure generating chamber in the longitudinal direction, thereby reducing a problem such as cracking. Further, since the resistance to cracking of the piezoelectric element is improved, voltage resistance to the piezoelectric element is also improved.
- an area where the first electrode, the piezoelectric layer and the second electrode overlap may be formed to extend to an outside of the pressure generating chamber in the longitudinal direction. That is, since the area where the first electrode, the piezoelectric layer and the second electrode overlap (active section) is an area which drives when a voltage is applied, concentration of distortion at the interface on the piezoelectric element is reduced by providing the active section to extend to the outside of the pressure generating chamber in the longitudinal direction, thereby reducing a problem such as cracking.
- an opening is formed on the piezoelectric layer by removing the piezoelectric layer at a position that substantially corresponds to an area between the pressure generating chambers, and the opening may be formed to extend to an outside of the pressure generating chamber in the longitudinal direction.
- a metal layer that is disposed on the second electrode and serves as a wiring may be formed to extend to both inside and outside of the pressure generating chamber.
- the technical concept of the invention is not limited to the form of liquid ejection head, and for example, a liquid ejection apparatus having the liquid ejection head in any of the aspects described above may be regarded as one aspect of the invention. Further, a manufacturing method including a manufacturing step of piezoelectric element, liquid ejection head and liquid ejection apparatus in any of the aspects described above (for example, a manufacturing method of piezoelectric element, manufacturing method of liquid ejection head and manufacturing method of liquid ejection apparatus) may be regarded as one aspect of the invention.
- FIG. 1 is an exploded perspective view which schematically shows a recording head.
- FIG. 2 is a sectional view of the recording head in a plane parallel to the longitudinal direction.
- FIG. 3 is a plan view of an area on a substrate.
- FIGS. 4A , 4 B and 4 C are sectional views taken along the respective lines of FIG. 3 .
- FIGS. 5A , 5 B and 5 C are views which show part of manufacturing steps of a piezoelectric element in sequence.
- FIGS. 6A , 6 B and 6 C are views which show part of manufacturing steps of a piezoelectric element in sequence.
- FIG. 7 is a plan view of an area on a substrate according to a modified example.
- FIG. 8 is a view which explains an effect of the modified example.
- FIG. 9 is a schematic view of an example of an ink jet recording apparatus.
- FIG. 1 is an exploded perspective view which schematically shows an ink jet recording head 1 (hereinafter, referred to as recording head 1 ) which is an example of liquid ejection head.
- FIG. 2 is a vertical sectional view of the recording head 1 in a plane parallel to the longitudinal direction of a pressure generating chambers 12 and passing through a lower electrode film 2 that corresponds to one of the pressure generating chambers 12 .
- the recording head 1 includes a substrate (flow path forming substrate) 10 .
- the substrate 10 is formed of, for example, a silicon single crystal substrate with a vibration plate 50 disposed on one side thereof.
- the vibration plate 50 includes, for example, an elastic film 51 formed of an oxide film that is in contact with the substrate 10 , and an insulator film 55 formed of an oxide film made of a material different from that of the elastic film 51 and stacked on the elastic film 51 .
- a plurality of pressure generating chambers 12 that are separated by dividing walls 11 are arranged side by side in the short direction (width direction) thereof on the substrate 10 , and one side of the pressure generating chambers 12 are closed by the vibration plate 50 .
- ink supply paths 14 that are separated by the dividing walls 11 and communicate with the respective pressure generating chambers 12 are formed at one end of the pressure generating chambers 12 in the longitudinal direction. Further, a communication section 13 that communicates with the respective ink supply paths 14 is formed on the outer side of the ink supply paths 14 . The communication section 13 communicates with a reservoir section 31 of a protective substrate 30 , which will be described later, so as to form part of a reservoir 9 that serves as an ink chamber (liquid chamber) for all the pressure generating chambers 12 .
- Each ink supply path 14 has a cross sectional area in the width direction smaller than that of the pressure generating chamber 12 so as to keep a flow path resistance of ink that is introduced from the communication section 13 into the pressure generating chambers 12 to be constant.
- the ink supply path 14 is narrower in the width direction thereof, instead or well it may be thinner in the thickness direction of the substrate 10 so as to have a cross sectional area smaller than that of the pressure generating chamber 12 .
- the material of the substrate 10 is not limited to a silicon single crystal substrate, and may include a glass ceramic material, stainless steel, etc.
- a nozzles plate 20 is secured by using an adhesive, a heat adhesive film or the like on the surface of the substrate 10 opposite to the side on which the vibration plate 50 is disposed.
- Nozzle openings 21 that correspond to the respective pressure generating chambers 12 are formed on the nozzles plate 20 by drilling at positions adjacent to the other end of the pressure generating chambers 12 in the longitudinal direction.
- the nozzles plate 20 is formed of, for example, a glass ceramic material, silicon single crystal substrate, stainless steel, etc.
- a plurality of piezoelectric elements 3 having the lower electrode film 2 , a piezoelectric layer 5 and an upper electrode film 4 are formed on the surface of the vibration plate 50 opposite to the side of the substrate 10 and arranged side by side in the width direction thereof.
- the piezoelectric elements 3 are formed so as to correspond to the respective pressure generating chambers 12 .
- the lower electrode film 2 is defined as a first electrode which is formed on the surface of the piezoelectric layer 5 on the side of the substrate 10 and corresponds to each of the pressure generating chambers 12 .
- the upper electrode film 4 is defined as a second electrode which is formed on the surface of the piezoelectric layer 5 opposite to the side on which the first electrode of the piezoelectric layer 5 is formed and extends across an area that corresponds to the plurality of pressure generating chambers 12 .
- the piezoelectric element 3 includes an area (active section) where the lower electrode film 2 , the piezoelectric layer 5 and the upper electrode film 4 overlap. Further, the piezoelectric element 3 and the vibration plate 50 that is displaced by driving the piezoelectric element 3 are collectively defined as an actuator device.
- one of the electrodes disposed on each side of the piezoelectric layer 5 is configured as a common electrode, and the other is configured as an individual electrode.
- the lower electrode film 2 serves as the individual electrode for each of the piezoelectric elements 3 that correspond to the respective pressure generating chambers 12
- the upper electrode film 4 serves as the common electrode for all the pressure generating chambers 12 that correspond to the piezoelectric element 3 .
- a plurality of recesses are formed as openings 5 a in the piezoelectric layer 5 by removing the piezoelectric layer 5 .
- the plurality of openings 5 a are arranged side by side in the width direction thereof and are formed at positions that substantially correspond to between each of the pressure generating chambers 12 .
- each of the piezoelectric elements 3 including the active section are formed between the openings 5 a so as to correspond to each of the pressure generating chambers 12 .
- the surface of the openings 5 a are covered by the upper electrode film 4 .
- the protective substrate 30 with a compliance substrate 40 being secured thereon is mounted on the surface of the vibration plate 50 on which the piezoelectric elements are formed.
- the protective substrate 30 including a piezoelectric element holding section 32 is attached by using an adhesive 35 on the surface of the vibration plate 50 on which the piezoelectric elements 3 are formed.
- the piezoelectric element holding section 32 is positioned so as to oppose the piezoelectric elements 3 and has an inner space that is sized so as not to interfere with the movement of the piezoelectric elements 3 .
- the protective substrate 30 also includes the reservoir section 31 formed at a position that corresponds to the communication section 13 of the substrate 10 .
- the reservoir section 31 for example, penetrates through the protective substrate 30 in the thickness direction and extends in the width direction of the pressure generating chambers 12 , and accordingly, communicates with the communication section 13 of the substrate 10 as described above, thereby forming a reservoir 9 .
- the material of the protective substrate 30 may include a glass, ceramics material, metal, resin etc., it is preferable to be a material having substantially the same thermal expansion rate as that of the substrate 10 .
- the protective substrate 30 is formed of a silicon single crystalline substrate, which is the same material as that of the substrate 10 .
- a lead electrode 60 is connected to the upper electrode film 4 which is the common electrode, while a lead electrode 61 is connected to the lower electrode film 2 which is the individual electrode.
- the lead electrodes 60 , 61 and a through hole 5 b (which will be described later) that extends through the piezoelectric layer 5 for connecting the lead electrode 61 to the lower electrode film 2 are not shown in FIG. 1 .
- the lead electrodes 60 , 61 are connected to a drive circuit 120 ( FIG. 1 ) on which a drive IC for driving the piezoelectric elements 3 and the like are mounted via leads, which are not shown in the figure.
- the lead electrode 60 is a metal layer disposed on the second electrode and serves as wirings.
- the lead electrode 61 that is connected to the individual electrode is disposed on the other end in the longitudinal direction, the lead electrode 61 may be disposed on one side in the longitudinal direction.
- the compliance substrate 40 composed of a sealing film 41 and a fixation plate 42 is attached on the protective substrate 30 .
- the sealing film 41 is made of a flexible material having a low rigidity, and one side of the reservoir section 31 is sealed by the sealing film 41 .
- the fixation plate 42 is made of a rigid material such as a metal. Since an area of the fixation plate 42 which opposes the reservoir 9 is completely removed in the thickness direction to form an opening 43 , one side of the reservoir 9 is sealed only by the flexible sealing film 41 .
- ink is introduced from an external ink supply unit, which is not shown in the figure.
- a voltage is applied to each of the piezoelectric elements 3 that correspond to the pressure generating chambers 12 in response to recording signals from the drive IC so that the piezoelectric elements 3 are flexibly deformed.
- a pressure in the pressure generating chambers 12 increases, thereby allowing ink droplets (liquid) to be output (ejected) from the nozzle openings 21 .
- FIG. 3 is a plan view of an area of the substrate 10 in which the piezoelectric element 3 that corresponds to one pressure generating chamber 12 is formed.
- FIG. 4A is a vertical sectional view taken along the line IVA-IVA of FIG. 3
- FIG. 4B is a vertical sectional view taken along the line IVB-IVB of FIG. 3
- FIG. 4C is a vertical sectional view taken along the line IVC-IVC of FIG. 3 .
- FIG. 3 The outline of the pressure generating chamber 12 and the ink supply path 14 that communicates with the pressure generating chamber 12 is illustrated in FIG. 3 by the dashed two dotted line. Although the outline of the pressure generating chamber 12 and the ink supply path 14 shown in FIG. 3 is slightly different from that of FIGS. 1 and 2 , either may be employed.
- a range of the lower electrode film 2 as the individual electrode is indicated by the thin dotted line
- a range of the piezoelectric layer 5 is indicated by the bold dotted line
- a range of the upper electrode film 4 as the common electrode is indicated by the gray-colored area.
- a range of the lead electrode 60 that is partially stacked on the upper electrode film 4 and a range of lead electrode 61 that is partially stacked on the piezoelectric layer 5 are illustrated by hatching.
- the through hole 5 b is formed on the piezoelectric layer 5 such that the lead electrode 61 is electrically connected to the lower electrode film 2 via the through hole 5 b.
- the lower electrode film 2 has a length in the width direction which is smaller than that of the pressure generating chambers 12 and a length in the longitudinal direction larger than the pressure generating chambers 12 . Specifically, one end of the lower electrode film 2 in the longitudinal direction extends to the position of the ink supply paths 14 , while the other end extends over the end of the pressure generating chambers 12 . Further, the lower electrode film 2 is covered by the piezoelectric layer 5 except for a range that faces the through hole 5 b . Accordingly, a leak current from the lower electrode film 2 can be reduced to a minimum, thereby eliminating a particular measure to reduce the leak current (for example, protection by using a protective film made of a material such as aluminum oxide).
- the openings 5 a are formed at positions that substantially correspond to part of the dividing walls 11 which are located on both sides of the pressure generating chambers 12 in the width direction. As shown in FIG. 4B , the openings 5 a are formed by removing the piezoelectric layer 5 . Since such openings 5 a are formed, the piezoelectric layer 5 on the pressure generating chambers 12 is mostly included within the pressure generating chambers 12 in the width direction, while both ends of the piezoelectric layer 5 extend to the outside of the pressure generating chambers 12 in the longitudinal direction so as to completely cover the length of the pressure generating chambers 12 .
- the upper electrode film 4 extend to the outside of the pressure generating chambers 12 both in the width direction and the longitudinal direction so as to completely cover the length of the pressure generating chambers 12 . That is, in this embodiment, the active sections that correspond to the respective pressure generating chambers 12 extend to the outside of the pressure generating chambers 12 in the longitudinal direction. As shown in FIG. 3 , the length of the active section in the longitudinal direction is defined as L1, and the length of the pressure generating chambers 12 in the longitudinal direction is defined as L2 such that L1 covers the range of L2.
- the configurations of FIG. 3 are repeatedly disposed in the width direction on the substrate 10 (more specifically, on the insulator film 55 ) so as to correspond to the pressure generating chambers 12 . Accordingly, the piezoelectric layer 5 , the upper electrode film 4 and the lead electrode 60 are repeatedly disposed in the width direction (see FIG. 1 as appropriate). Further, two lead electrodes 60 of FIG. 3 (the lead electrode 60 as shown in FIG. 4A and the lead electrode 60 as shown in FIG. 4C ) are connected to each other at a specified position, which is not shown in the figure, so as to form one common electrode.
- both ends of the active section in the longitudinal direction of the pressure generating chamber 12 are configured to extend to the outside of the pressure generating chamber 12 . Accordingly, when the active section of the piezoelectric element 3 drives to flexibly deform the piezoelectric element 3 , concentration of distortion at the interface between the active section and the inactive section of the piezoelectric element 3 is reduced compared to the case in which both ends of the active section in the longitudinal direction of the pressure generating chamber 12 are configured not to extend to the outside of the pressure generating chamber 12 , thereby reducing a problem such as cracking of the piezoelectric layer 5 . Further, since the resistance to cracking of the piezoelectric element 3 is improved, voltage resistance to the piezoelectric element 3 is also improved.
- the lead electrode 60 of this embodiment extends on both the inside and outside of the pressure generating chamber 12 (across the end of the pressure generating chambers 12 ). With this arrangement of the lead electrode 60 , concentration of distortion at the interface between the active section and the inactive section of the piezoelectric element 3 or at the proximity of both ends of the piezoelectric element 3 is reduced, thereby further effectively reducing a problem such as cracking.
- the opening 5 a serves to provide the active section with a spring property by reducing the thickness of the circumference of the active section. Accordingly, the size of the opening 5 a significantly effects on the flexibility of the active section.
- a length L3 of the opening 5 a in the longitudinal direction is within the length L2 of the pressure generating chambers 12 . That is, both ends of the opening 5 a in the longitudinal direction are located at the inner side of both ends of the pressure generating chambers 12 . Accordingly, the piezoelectric layer 5 overlaps both ends of the pressure generating chambers 12 in the longitudinal direction, thereby increasing rigidity of the piezoelectric element 3 at the proximity of both ends of the pressure generating chambers 12 . As a result, concentration of distortion at the interface between the active section and the inactive section of the piezoelectric element 3 or at the proximity of both ends of the piezoelectric element 3 is reduced, thereby further effectively reducing a problem such as cracking.
- FIGS. 5A , 5 B, 5 C and FIGS. 6A , 6 B, 6 C show manufacturing steps of the piezoelectric element 3 that constitutes the recording head 1 in sequence.
- FIGS. 5A , 5 B, 5 C and FIGS. 6A , 6 B, 6 C are combination of vertical sectional views as seen from the same view point as that of FIG. 2 in a plane parallel to the longitudinal direction and vertical sectional views taken along the line D-D′ in the respective figures, showing progress in the manufacturing steps.
- the elastic film 51 formed of silicon dioxide (SiO 2 ) and the insulator film 55 formed of zirconium oxide (ZrO 2 ) are formed on the silicon single crystal substrate (not shown in the figure) which is a material of the substrate 10 (for example, see JP-A-2005-8841).
- a lower electrode film is formed by laminating platinum and iridium on the insulator film 55 , for example, by a sputtering technique.
- a thin piezoelectric layer is formed on the lower electrode film, for example, by a sol-gel process.
- the thin piezoelectric layer as used herein means that the piezoelectric layer has a thickness at least smaller than that of the piezoelectric layer 5 which is required in the resultant piezoelectric element 3 .
- FIG. 5A shows the lower electrode film 2 and the piezoelectric layer 500 on the lower electrode film 2 that have been formed by the above-mentioned patterning. In the state shown in FIG.
- the piezoelectric layer is further formed to a thickness required in the resultant piezoelectric element 3 , for example, by a sol-gel process, and then, a thin upper electrode film formed of iridium or the like is formed on the piezoelectric layer, for example, by a sputtering technique.
- the thin upper electrode film as used herein means that the upper electrode film has a thickness at least smaller than that of the upper electrode film 4 which is required in the resultant piezoelectric element 3 .
- FIG. 5B shows the piezoelectric layer 501 and the upper electrode film 400 on the piezoelectric layer 501 that have been formed in the steps so far.
- FIG. 5B shows the upper electrode film 400 and the piezoelectric layer 501 to make patterning that leaves a specific thickness of the piezoelectric layer that covers the lower electrode film 2 and the upper electrode film on the piezoelectric layer. That is, a recess that corresponds to the opening 5 a is formed.
- etching of the piezoelectric layer for forming the opening 5 a is referred to as “first etching process of the piezoelectric layer” as appropriate.
- FIG. 5C shows the piezoelectric layer 502 and the upper electrode film 401 on the piezoelectric layer 502 that have been formed in the steps so far.
- FIG. 5C shows the state shown in FIG. 5C .
- photo-etching is performed on the upper electrode film 401 and the piezoelectric layer 502 to form the through hole 5 b that allows part of the lower electrode film 2 to be exposed.
- etching of the piezoelectric layer for forming the through holes 5 b is referred to as “second etching process of the piezoelectric layer” as appropriate.
- FIG. 6A shows the piezoelectric layer 5 and the upper electrode film 402 on the piezoelectric layer 5 that have been formed in the steps so far.
- the through hole 5 b penetrates through the piezoelectric layer 5 and the upper electrode film 402 .
- etching of the piezoelectric layer for forming the opening 5 a and etching of the piezoelectric layer for forming the through hole 5 b are separately performed, whose reason will be described later.
- the upper electrode film is further formed to a thickness required in the resultant piezoelectric element 3 , for example, by a sputtering technique.
- photo-etching is performed on the upper electrode film to make patterning on the upper electrode film so as to form a specific pattern that corresponds to the respective positions where the pressure generating chambers 12 are to be formed and a specific pattern that includes the range of the respective through holes (see FIG. 3 ).
- FIG. 6B shows the upper electrode film 4 that has been formed by the above-mentioned patterning. Then, in the state shown in FIG.
- a metal layer (for example, the metal layer including gold (Au) and Nichrome (NiCr) which is a material of the lead electrodes 60 , 61 is formed, for example, by a sputtering technique, and then, photo-etching is performed on the metal layer so as to form the lead electrodes 60 , 61 .
- the lead electrode 60 is connected to the upper electrode film 4 .
- the lead electrode 61 is connected to the lower electrode film 2 via the through hole 5 b and the upper electrode film 4 ( FIG. 6B ) formed on the surface of the through hole 5 b .
- the upper electrode film 4 ( FIG. 6B ) formed on the surface of the through hole 5 b serves as part of the wirings that connect the drive circuit 120 and the individual electrode (the lower electrode film 2 ).
- FIG. 6C shows a configuration that has been formed in the steps so far.
- the configuration shown in FIG. 6C is consistent with the configuration of the piezoelectric element 3 shown in FIG. 2 and FIG. 3 .
- the recording head 1 is completed through the steps such as connecting of the protective substrate 30 on the side of the piezoelectric element 3 , forming of the pressure generating chambers 12 , the ink supply paths 14 and the like by etching the substrate 10 , connecting of the nozzles plate 20 on the substrate 10 , and connecting of the compliance substrate 40 on the protective substrate 30 .
- the above-mentioned manufacturing method of the recording head 1 is merely an example, and various modifications are possible.
- the forming method of the piezoelectric layer is also not limited to that described above, and a sputtering technique may also be used.
- the material of the piezoelectric layer may include various materials, for example, lead zirconate titanate based material and non-lead (lead-free) perovskite oxide such as barium titanate.
- the reason of the first etching process of the piezoelectric layer and the second etching process of the piezoelectric layer being separately provided in the above-mentioned manufacturing method will be described.
- the piezoelectric layer 501 is formed so as to cover the lower electrode film 2 and the insulator film 55 around the lower electrode film 2 as shown in FIG. 5B , it is not always possible due to manufacturing accuracy to easily make the thickness of the piezoelectric layer 501 on the insulator film 55 and the thickness of the piezoelectric layer 501 on the lower electrode film 2 to be the same. Particularly, uneven thickness of those layers becomes significant when the piezoelectric layer is formed by using liquid, typically by a sol-gel process.
- the optimum etching amount of the piezoelectric layer 501 to expose the insulator film 55 (to form the opening 5 a ) is different from the optimum etching amount of the piezoelectric layer 501 to expose the lower electrode film 2 (to form the through hole 5 b ). If etching for exposing the insulator film 55 and etching for exposing the lower electrode film 2 are simultaneously performed, one of the insulator film 55 and the lower electrode film 2 may suffer from over etching (excessive etching) and the other may suffer from under etching (insufficient etching), since it is difficult to precisely control the etching amount at each location.
- the lower electrode film 2 suffers from over etching during removing of the piezoelectric layer 501 on the insulator film 55 , which may cause breakage of the lower electrode film 2 . Further, in an attempt to prevent over etching of the lower electrode film 2 , the insulator film 55 may fail to be exposed.
- the insulator film 55 suffers from over etching during removing of the piezoelectric layer 501 on the lower electrode film 2 .
- the opening 5 a is thinner than the required thickness and fails to obtain the required rigidity, which may cause cracking on the opening 5 a .
- the lower electrode film 2 may fail to be exposed.
- the first etching process of the piezoelectric layer and the second etching process of the piezoelectric layer are separately provided so that optimum etching amount of the piezoelectric layer is set to obtain the thickness for each area to be processed in each process. Accordingly, optimum etching of the piezoelectric layer 501 to form the opening 5 a and optimum etching of the piezoelectric layer 501 to form the through hole 5 b can be achieved, thereby preventing the above-mentioned over etching and under etching from occurred.
- the first etching process of the piezoelectric layer and the second etching process of the piezoelectric layer may be performed in the order opposite to that is described in the above description.
- FIG. 7 is a plan view of an area on the substrate 10 according to a modified example, and similarly to FIG. 3 , shows the area in which the piezoelectric element 3 that corresponds to one pressure generating chamber 12 is formed.
- the configuration of FIG. 7 and the configuration of FIG. 3 are different in that they have different lengths of the opening 5 a in the longitudinal direction. Specifically, the opening 5 a of FIG. 7 is longer than that of FIG. 3 , and the opening 5 a of FIG. 7 is formed to extend to the outside of the pressure generating chamber 12 in the longitudinal direction. That is, in FIG. 7 , the length L3 of the opening 5 a in the longitudinal direction is formed to include the length L2 of the pressure generating chamber 12 . With this configuration, a rigidity of the piezoelectric element 3 at the proximity of both ends of the pressure generating chambers 12 in the longitudinal direction decreases, and a displacement amount of the piezoelectric element 3 at the proximity of both the pressure generating chamber 12 increases.
- FIG. 8 is a view which explains an effect of the modified example.
- FIG. 8 illustrates the positional relationship between the pressure generating chamber 12 in the longitudinal direction and the elastic film 51 that closes the upper portion of the pressure generating chamber 12 in a simplified manner.
- the active section displaces and the elastic film 51 flexes into the pressure generating chamber 12 .
- the difference between the position before the elastic film 51 flexes (the position of the elastic film 51 indicated by the solid line in FIG. 8 ) and the position after the elastic film 51 flexes in the up-down direction is the displacement amount Ah. Further, in FIG.
- the positions of the flexed elastic film is illustrated by the dotted line and the dashed two dotted line.
- the position indicated by the dotted line shows the position in a configuration in which the length L3 of the opening 5 a is within the length L2 of the pressure generating chambers 12
- the position indicated by the dashed two dotted line shows the position in a configuration (configuration of FIG. 7 ) in which the length L3 of the opening 5 a includes the length L2 of the pressure generating chamber 12 .
- the displacement amounts Ah at the center of the pressure generating chamber 12 in the longitudinal direction is substantially the same regardless of the above-mentioned difference of the length L3 of the opening 5 a .
- the displacement amounts Ah at the end portions of the pressure generating chambers 12 are different such that the displacement amounts ⁇ h are larger in the configuration in which the length L3 of the opening 5 a is longer than the length L2.
- the displacement amounts ⁇ h at the end portions of the pressure generating chambers 12 increases, the amount of liquid ejected by flexing of the piezoelectric element 3 . That is, according to the modified example shown in FIG. 7 , performance of the recording head 1 can be improved by increasing the amount of liquid ejected.
- a vertical sectional view taken along the line IVB-IVB is the same as that of FIG. 4B .
- the opening 5 a is formed similarly to the vertical sectional view taken along the line IVB-IVB, and the upper electrode film 4 and the lead electrode 60 are disposed on the opening 5 a.
- FIG. 9 is a schematic view of an example of the ink jet recording apparatus.
- cartridges 2 A, 2 B that constitute the ink supply unit are detachably mounted on the recording head units 1 A, 1 B having a recording head.
- a carriage 16 on which the recording head units 1 A, 1 B are mounted is provided on a carriage shaft 18 that is formed on an apparatus body 17 so as to be movable along the carriage shaft 18 .
- the recording head units 1 A, 1 B are configured to eject, for example, black ink composition and color ink composition, respectively.
- a drive force from a drive motor 19 is transmitted to the carriage 16 via a plurality of gears (not shown in the figure) and a timing belt 7 , the carriage 16 on which the recording head units 1 A, 1 B are mounted moves along the carriage shaft 18 .
- a platen 8 is provided along the carriage shaft 18 in the apparatus body 17 such that a recording sheet S which is a recording medium such as a sheet of paper fed by a feeding roller and the like, which are not shown in the figure, is transported on the platen 8 .
- liquid ejection head is not limited thereto.
- the invention is generally directed to liquid ejection heads, and as a matter of course, can be applied to heads that ejects liquid other than ink.
- Other liquid ejection heads may include, for example, various recording heads used for image recording apparatuses such as printers, color material ejection heads used for manufacturing color filters for liquid crystal displays and the like, electrode material ejection heads used for manufacturing electrodes for organic electroluminescence (EL) displays, field emission displays (FEDs) and the like, and bioorganic ejection heads used for manufacturing biochips.
- various recording heads used for image recording apparatuses such as printers, color material ejection heads used for manufacturing color filters for liquid crystal displays and the like, electrode material ejection heads used for manufacturing electrodes for organic electroluminescence (EL) displays, field emission displays (FEDs) and the like, and bioorganic ejection heads used for manufacturing biochips.
- EL organic electroluminescence
- FEDs field emission displays
- the piezoelectric element of the invention is not limited to that used for the liquid ejection head, and can be used for other devices.
- Other devices may include, for example, ultrasonic devices such as ultrasonic transmitters, ultrasonic motors, temperature-electricity converters, pressure-electricity converters, ferroelectric transistors, piezoelectric transducers, block filters for harmful rays such as infrared ray, optical filters using photonic crystal effect by quantum dot structure, and optical filters using thin film light interference.
- the invention is also applicable to piezoelectric elements used for sensors, and piezoelectric elements used for ferroelectric memories.
- Sensors that use a piezoelectric element may include, for example, infrared sensors, ultrasonic sensors, thermo-sensitive sensors, pressure sensors, pyroelectric sensors and gyro sensors (angular rate sensors).
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Abstract
A liquid ejection head includes a substrate in which a pressure generating chamber that communicates with a nozzle opening is formed; and a piezoelectric element having a piezoelectric layer, a first electrode that is formed on a surface of the piezoelectric layer on a side of the substrate so as to correspond to the pressure generating chamber, and a second electrode that is formed on a surface of the piezoelectric layer opposite to the side on which the first electrode is formed so as to extend over a plurality of the pressure generating chambers, wherein the second electrode is formed to extend to an outside of the pressure generating chamber in a longitudinal direction of the pressure generating chamber.
Description
- This is a continuation application of U.S. application Ser. No. 13/755,342 filed Jan. 31, 2013 which claims priority to Japanese Patent Application No. 2012-019569, filed Feb. 1, 2012 all of which are incorporated by reference herein in their entireties.
- 1. Technical Field
- The present invention relates to liquid ejection heads and liquid ejection apparatuses.
- 2. Related Art
- JP-A-2009-172878 and JP-A-2009-196329 disclose a liquid ejection head including a substrate in which a pressure generating chamber that communicates with a nozzle opening for ejecting liquid is formed, and a piezoelectric element having a piezoelectric layer, a lower electrode that is formed on the lower side of the piezoelectric layer and an upper electrode that is formed on the upper side of the piezoelectric layer. In such a liquid ejection head, the lower electrode is provided as an individual electrode that corresponds to each of the pressure generating chambers, and the upper electrode is provided as a common electrode for a plurality of piezoelectric elements that correspond to a plurality of pressure generating chambers.
- The above-mentioned piezoelectric element displaces when a voltage is applied across both electrodes and flexes into the pressure generating chamber. During flexing, a significant amount of stress is generated at the interface between an area on the piezoelectric element where the upper electrode, the piezoelectric layer and the lower electrode overlap (active section) and an area other than the active section (inactive section), which causes distortion to be concentrated at this position. Since concentration of distortion may cause a problem such as crack in the piezoelectric layer that forms the piezoelectric element, it has been required to prevent such a problem. Further, in addition to prevention of the above-mentioned problem, it has been also required to increase the amount of liquid to be output (ejected) from the pressure generating chamber to the outside of the nozzle opening by using deformation of the vibration plate in response to flexing of the piezoelectric element, thereby improving performance of the liquid ejection head.
- An advantage of some aspects of the invention is that a liquid ejection head capable of preventing or reducing a problem such as cracking in a piezoelectric layer and increasing the amount of liquid to be ejected, and a liquid ejection apparatus having the same are provided.
- According to an aspect of the invention, a liquid ejection head includes: a substrate in which a pressure generating chamber that communicates with a nozzle opening is formed; and a piezoelectric element having a piezoelectric layer, a first electrode that is formed on a surface of the piezoelectric layer on a side of the substrate so as to correspond to the pressure generating chamber, and a second electrode that is formed on a surface of the piezoelectric layer opposite to the side on which the first electrode is formed so as to extend over a plurality of the pressure generating chambers, wherein the second electrode is formed to extend to an outside of the pressure generating chamber in a longitudinal direction of the pressure generating chamber. With this configuration, the second electrode is formed to extend to the outside of the pressure generating chamber in the longitudinal direction of the pressure generating chamber. Accordingly, concentration of distortion at the interface on the piezoelectric element is reduced compared to the case in which the second electrode is formed not to extend to the outside of the pressure generating chamber in the longitudinal direction, thereby reducing a problem such as cracking. Further, since the resistance to cracking of the piezoelectric element is improved, voltage resistance to the piezoelectric element is also improved.
- According to an aspect of the invention, an area where the first electrode, the piezoelectric layer and the second electrode overlap may be formed to extend to an outside of the pressure generating chamber in the longitudinal direction. That is, since the area where the first electrode, the piezoelectric layer and the second electrode overlap (active section) is an area which drives when a voltage is applied, concentration of distortion at the interface on the piezoelectric element is reduced by providing the active section to extend to the outside of the pressure generating chamber in the longitudinal direction, thereby reducing a problem such as cracking.
- According to an aspect of the invention, an opening is formed on the piezoelectric layer by removing the piezoelectric layer at a position that substantially corresponds to an area between the pressure generating chambers, and the opening may be formed to extend to an outside of the pressure generating chamber in the longitudinal direction. With this configuration, since the opening is formed to extend to the outside of the pressure generating chamber in the longitudinal direction, a displacement amount of the piezoelectric element at the end portions of the pressure generating chamber increases, which results in increased amount of liquid ejected by flexing of the piezoelectric element.
- According to an aspect of the invention, a metal layer that is disposed on the second electrode and serves as a wiring may be formed to extend to both inside and outside of the pressure generating chamber. With this configuration, since the metal layer is formed to extend to both inside and outside of the pressure generating chamber, concentration of distortion at the interface on the piezoelectric element is further reduced, thereby reducing a problem such as cracking.
- The technical concept of the invention is not limited to the form of liquid ejection head, and for example, a liquid ejection apparatus having the liquid ejection head in any of the aspects described above may be regarded as one aspect of the invention. Further, a manufacturing method including a manufacturing step of piezoelectric element, liquid ejection head and liquid ejection apparatus in any of the aspects described above (for example, a manufacturing method of piezoelectric element, manufacturing method of liquid ejection head and manufacturing method of liquid ejection apparatus) may be regarded as one aspect of the invention.
- The invention will now be described by way of example only with reference to the accompanying drawings, wherein like numbers reference like elements.
-
FIG. 1 is an exploded perspective view which schematically shows a recording head. -
FIG. 2 is a sectional view of the recording head in a plane parallel to the longitudinal direction. -
FIG. 3 is a plan view of an area on a substrate. -
FIGS. 4A , 4B and 4C are sectional views taken along the respective lines ofFIG. 3 . -
FIGS. 5A , 5B and 5C are views which show part of manufacturing steps of a piezoelectric element in sequence. -
FIGS. 6A , 6B and 6C are views which show part of manufacturing steps of a piezoelectric element in sequence. -
FIG. 7 is a plan view of an area on a substrate according to a modified example. -
FIG. 8 is a view which explains an effect of the modified example. -
FIG. 9 is a schematic view of an example of an ink jet recording apparatus. - An embodiment of the invention will be described below with reference to the drawings.
FIG. 1 is an exploded perspective view which schematically shows an ink jet recording head 1 (hereinafter, referred to as recording head 1) which is an example of liquid ejection head.FIG. 2 is a vertical sectional view of therecording head 1 in a plane parallel to the longitudinal direction of apressure generating chambers 12 and passing through alower electrode film 2 that corresponds to one of thepressure generating chambers 12. Therecording head 1 includes a substrate (flow path forming substrate) 10. Thesubstrate 10 is formed of, for example, a silicon single crystal substrate with avibration plate 50 disposed on one side thereof. Thevibration plate 50 includes, for example, anelastic film 51 formed of an oxide film that is in contact with thesubstrate 10, and aninsulator film 55 formed of an oxide film made of a material different from that of theelastic film 51 and stacked on theelastic film 51. A plurality ofpressure generating chambers 12 that are separated by dividingwalls 11 are arranged side by side in the short direction (width direction) thereof on thesubstrate 10, and one side of thepressure generating chambers 12 are closed by thevibration plate 50. - In the
substrate 10,ink supply paths 14 that are separated by the dividingwalls 11 and communicate with the respectivepressure generating chambers 12 are formed at one end of thepressure generating chambers 12 in the longitudinal direction. Further, acommunication section 13 that communicates with the respectiveink supply paths 14 is formed on the outer side of theink supply paths 14. Thecommunication section 13 communicates with areservoir section 31 of aprotective substrate 30, which will be described later, so as to form part of areservoir 9 that serves as an ink chamber (liquid chamber) for all thepressure generating chambers 12. - Each
ink supply path 14 has a cross sectional area in the width direction smaller than that of thepressure generating chamber 12 so as to keep a flow path resistance of ink that is introduced from thecommunication section 13 into thepressure generating chambers 12 to be constant. Although theink supply path 14 is narrower in the width direction thereof, instead or as well it may be thinner in the thickness direction of thesubstrate 10 so as to have a cross sectional area smaller than that of thepressure generating chamber 12. The material of thesubstrate 10 is not limited to a silicon single crystal substrate, and may include a glass ceramic material, stainless steel, etc. - A
nozzles plate 20 is secured by using an adhesive, a heat adhesive film or the like on the surface of thesubstrate 10 opposite to the side on which thevibration plate 50 is disposed.Nozzle openings 21 that correspond to the respectivepressure generating chambers 12 are formed on thenozzles plate 20 by drilling at positions adjacent to the other end of thepressure generating chambers 12 in the longitudinal direction. Thenozzles plate 20 is formed of, for example, a glass ceramic material, silicon single crystal substrate, stainless steel, etc. - A plurality of
piezoelectric elements 3 having thelower electrode film 2, apiezoelectric layer 5 and anupper electrode film 4 are formed on the surface of thevibration plate 50 opposite to the side of thesubstrate 10 and arranged side by side in the width direction thereof. Thepiezoelectric elements 3 are formed so as to correspond to the respectivepressure generating chambers 12. Thelower electrode film 2 is defined as a first electrode which is formed on the surface of thepiezoelectric layer 5 on the side of thesubstrate 10 and corresponds to each of thepressure generating chambers 12. On the other hand, theupper electrode film 4 is defined as a second electrode which is formed on the surface of thepiezoelectric layer 5 opposite to the side on which the first electrode of thepiezoelectric layer 5 is formed and extends across an area that corresponds to the plurality ofpressure generating chambers 12. Thepiezoelectric element 3 includes an area (active section) where thelower electrode film 2, thepiezoelectric layer 5 and theupper electrode film 4 overlap. Further, thepiezoelectric element 3 and thevibration plate 50 that is displaced by driving thepiezoelectric element 3 are collectively defined as an actuator device. Generally, in thepiezoelectric element 3, one of the electrodes disposed on each side of thepiezoelectric layer 5 is configured as a common electrode, and the other is configured as an individual electrode. In this embodiment, thelower electrode film 2 serves as the individual electrode for each of thepiezoelectric elements 3 that correspond to the respectivepressure generating chambers 12, and theupper electrode film 4 serves as the common electrode for all thepressure generating chambers 12 that correspond to thepiezoelectric element 3. - As shown in
FIG. 1 , a plurality of recesses are formed asopenings 5 a in thepiezoelectric layer 5 by removing thepiezoelectric layer 5. The plurality ofopenings 5 a are arranged side by side in the width direction thereof and are formed at positions that substantially correspond to between each of thepressure generating chambers 12. In other words, each of thepiezoelectric elements 3 including the active section are formed between theopenings 5 a so as to correspond to each of thepressure generating chambers 12. The surface of theopenings 5 a are covered by theupper electrode film 4. - The
protective substrate 30 with acompliance substrate 40 being secured thereon is mounted on the surface of thevibration plate 50 on which the piezoelectric elements are formed. In this embodiment, description will be appropriately made taking the side of thecompliance substrate 40 in therecording head 1 as the upper side, and the side of thenozzles plate 20 as the lower side for reference purposes of only. Theprotective substrate 30 including a piezoelectricelement holding section 32 is attached by using an adhesive 35 on the surface of thevibration plate 50 on which thepiezoelectric elements 3 are formed. The piezoelectricelement holding section 32 is positioned so as to oppose thepiezoelectric elements 3 and has an inner space that is sized so as not to interfere with the movement of thepiezoelectric elements 3. Since thepiezoelectric elements 3 are disposed inside the piezoelectricelement holding section 32, they are substantially protected from the outside environment. Further, theprotective substrate 30 also includes thereservoir section 31 formed at a position that corresponds to thecommunication section 13 of thesubstrate 10. Thereservoir section 31, for example, penetrates through theprotective substrate 30 in the thickness direction and extends in the width direction of thepressure generating chambers 12, and accordingly, communicates with thecommunication section 13 of thesubstrate 10 as described above, thereby forming areservoir 9. Although the material of theprotective substrate 30 may include a glass, ceramics material, metal, resin etc., it is preferable to be a material having substantially the same thermal expansion rate as that of thesubstrate 10. In this embodiment, theprotective substrate 30 is formed of a silicon single crystalline substrate, which is the same material as that of thesubstrate 10. - As shown in
FIG. 2 , alead electrode 60 is connected to theupper electrode film 4 which is the common electrode, while alead electrode 61 is connected to thelower electrode film 2 which is the individual electrode. Thelead electrodes hole 5 b (which will be described later) that extends through thepiezoelectric layer 5 for connecting thelead electrode 61 to thelower electrode film 2 are not shown inFIG. 1 . Thelead electrodes FIG. 1 ) on which a drive IC for driving thepiezoelectric elements 3 and the like are mounted via leads, which are not shown in the figure. Thelead electrode 60 is a metal layer disposed on the second electrode and serves as wirings. Although in the example shown inFIG. 2 , thelead electrode 61 that is connected to the individual electrode is disposed on the other end in the longitudinal direction, thelead electrode 61 may be disposed on one side in the longitudinal direction. - Further, the
compliance substrate 40 composed of a sealingfilm 41 and afixation plate 42 is attached on theprotective substrate 30. The sealingfilm 41 is made of a flexible material having a low rigidity, and one side of thereservoir section 31 is sealed by the sealingfilm 41. Thefixation plate 42 is made of a rigid material such as a metal. Since an area of thefixation plate 42 which opposes thereservoir 9 is completely removed in the thickness direction to form anopening 43, one side of thereservoir 9 is sealed only by theflexible sealing film 41. - In the
recording head 1, ink is introduced from an external ink supply unit, which is not shown in the figure. After ink fills the inside of the path from thereservoir 9 to thenozzle opening 21, a voltage is applied to each of thepiezoelectric elements 3 that correspond to thepressure generating chambers 12 in response to recording signals from the drive IC so that thepiezoelectric elements 3 are flexibly deformed. As a result, a pressure in thepressure generating chambers 12 increases, thereby allowing ink droplets (liquid) to be output (ejected) from thenozzle openings 21. - Next, a configuration of the
piezoelectric element 3 is described in detail with further reference toFIGS. 1 , 2 and alsoFIGS. 3 , 4.FIG. 3 is a plan view of an area of thesubstrate 10 in which thepiezoelectric element 3 that corresponds to onepressure generating chamber 12 is formed.FIG. 4A is a vertical sectional view taken along the line IVA-IVA ofFIG. 3 ,FIG. 4B is a vertical sectional view taken along the line IVB-IVB ofFIG. 3 , andFIG. 4C is a vertical sectional view taken along the line IVC-IVC ofFIG. 3 . - The outline of the
pressure generating chamber 12 and theink supply path 14 that communicates with thepressure generating chamber 12 is illustrated inFIG. 3 by the dashed two dotted line. Although the outline of thepressure generating chamber 12 and theink supply path 14 shown inFIG. 3 is slightly different from that ofFIGS. 1 and 2 , either may be employed. InFIG. 3 , a range of thelower electrode film 2 as the individual electrode is indicated by the thin dotted line, a range of thepiezoelectric layer 5 is indicated by the bold dotted line, and a range of theupper electrode film 4 as the common electrode is indicated by the gray-colored area. Further, inFIG. 3 , a range of thelead electrode 60 that is partially stacked on theupper electrode film 4 and a range oflead electrode 61 that is partially stacked on thepiezoelectric layer 5 are illustrated by hatching. The throughhole 5 b is formed on thepiezoelectric layer 5 such that thelead electrode 61 is electrically connected to thelower electrode film 2 via the throughhole 5 b. - The
lower electrode film 2 has a length in the width direction which is smaller than that of thepressure generating chambers 12 and a length in the longitudinal direction larger than thepressure generating chambers 12. Specifically, one end of thelower electrode film 2 in the longitudinal direction extends to the position of theink supply paths 14, while the other end extends over the end of thepressure generating chambers 12. Further, thelower electrode film 2 is covered by thepiezoelectric layer 5 except for a range that faces the throughhole 5 b. Accordingly, a leak current from thelower electrode film 2 can be reduced to a minimum, thereby eliminating a particular measure to reduce the leak current (for example, protection by using a protective film made of a material such as aluminum oxide). - The
openings 5 a are formed at positions that substantially correspond to part of the dividingwalls 11 which are located on both sides of thepressure generating chambers 12 in the width direction. As shown inFIG. 4B , theopenings 5 a are formed by removing thepiezoelectric layer 5. Sincesuch openings 5 a are formed, thepiezoelectric layer 5 on thepressure generating chambers 12 is mostly included within thepressure generating chambers 12 in the width direction, while both ends of thepiezoelectric layer 5 extend to the outside of thepressure generating chambers 12 in the longitudinal direction so as to completely cover the length of thepressure generating chambers 12. Theupper electrode film 4 extend to the outside of thepressure generating chambers 12 both in the width direction and the longitudinal direction so as to completely cover the length of thepressure generating chambers 12. That is, in this embodiment, the active sections that correspond to the respectivepressure generating chambers 12 extend to the outside of thepressure generating chambers 12 in the longitudinal direction. As shown inFIG. 3 , the length of the active section in the longitudinal direction is defined as L1, and the length of thepressure generating chambers 12 in the longitudinal direction is defined as L2 such that L1 covers the range of L2. - The configurations of
FIG. 3 are repeatedly disposed in the width direction on the substrate 10 (more specifically, on the insulator film 55) so as to correspond to thepressure generating chambers 12. Accordingly, thepiezoelectric layer 5, theupper electrode film 4 and thelead electrode 60 are repeatedly disposed in the width direction (seeFIG. 1 as appropriate). Further, twolead electrodes 60 ofFIG. 3 (thelead electrode 60 as shown inFIG. 4A and thelead electrode 60 as shown inFIG. 4C ) are connected to each other at a specified position, which is not shown in the figure, so as to form one common electrode. - In this embodiment, both ends of the active section in the longitudinal direction of the
pressure generating chamber 12 are configured to extend to the outside of thepressure generating chamber 12. Accordingly, when the active section of thepiezoelectric element 3 drives to flexibly deform thepiezoelectric element 3, concentration of distortion at the interface between the active section and the inactive section of thepiezoelectric element 3 is reduced compared to the case in which both ends of the active section in the longitudinal direction of thepressure generating chamber 12 are configured not to extend to the outside of thepressure generating chamber 12, thereby reducing a problem such as cracking of thepiezoelectric layer 5. Further, since the resistance to cracking of thepiezoelectric element 3 is improved, voltage resistance to thepiezoelectric element 3 is also improved. - As seen from
FIGS. 2 and 3 , thelead electrode 60 of this embodiment extends on both the inside and outside of the pressure generating chamber 12 (across the end of the pressure generating chambers 12). With this arrangement of thelead electrode 60, concentration of distortion at the interface between the active section and the inactive section of thepiezoelectric element 3 or at the proximity of both ends of thepiezoelectric element 3 is reduced, thereby further effectively reducing a problem such as cracking. - The
opening 5 a serves to provide the active section with a spring property by reducing the thickness of the circumference of the active section. Accordingly, the size of theopening 5 a significantly effects on the flexibility of the active section. In this embodiment, as seen fromFIG. 3 , a length L3 of theopening 5 a in the longitudinal direction is within the length L2 of thepressure generating chambers 12. That is, both ends of theopening 5 a in the longitudinal direction are located at the inner side of both ends of thepressure generating chambers 12. Accordingly, thepiezoelectric layer 5 overlaps both ends of thepressure generating chambers 12 in the longitudinal direction, thereby increasing rigidity of thepiezoelectric element 3 at the proximity of both ends of thepressure generating chambers 12. As a result, concentration of distortion at the interface between the active section and the inactive section of thepiezoelectric element 3 or at the proximity of both ends of thepiezoelectric element 3 is reduced, thereby further effectively reducing a problem such as cracking. - Next, an example of manufacturing method of the
recording head 1 according to this embodiment will be described below.FIGS. 5A , 5B, 5C andFIGS. 6A , 6B, 6C show manufacturing steps of thepiezoelectric element 3 that constitutes therecording head 1 in sequence.FIGS. 5A , 5B, 5C andFIGS. 6A , 6B, 6C are combination of vertical sectional views as seen from the same view point as that ofFIG. 2 in a plane parallel to the longitudinal direction and vertical sectional views taken along the line D-D′ in the respective figures, showing progress in the manufacturing steps. InFIGS. 5A , 5B, 5C andFIGS. 6A , 6B, 6C, components other than those of thepiezoelectric element 3, for example, thesubstrate 10 are not shown as appropriate. First, theelastic film 51 formed of silicon dioxide (SiO2) and theinsulator film 55 formed of zirconium oxide (ZrO2) are formed on the silicon single crystal substrate (not shown in the figure) which is a material of the substrate 10 (for example, see JP-A-2005-8841). Then, a lower electrode film is formed by laminating platinum and iridium on theinsulator film 55, for example, by a sputtering technique. After that, a thin piezoelectric layer is formed on the lower electrode film, for example, by a sol-gel process. The thin piezoelectric layer as used herein means that the piezoelectric layer has a thickness at least smaller than that of thepiezoelectric layer 5 which is required in the resultantpiezoelectric element 3. - Then, photo-etching is performed on the lower electrode film and the piezoelectric layer to make patterning on the lower electrode film and the piezoelectric layer so as to form a specific pattern that corresponds to the respective positions where the
pressure generating chambers 12 are to be formed.FIG. 5A shows thelower electrode film 2 and thepiezoelectric layer 500 on thelower electrode film 2 that have been formed by the above-mentioned patterning. In the state shown inFIG. 5A , the piezoelectric layer is further formed to a thickness required in the resultantpiezoelectric element 3, for example, by a sol-gel process, and then, a thin upper electrode film formed of iridium or the like is formed on the piezoelectric layer, for example, by a sputtering technique. The thin upper electrode film as used herein means that the upper electrode film has a thickness at least smaller than that of theupper electrode film 4 which is required in the resultantpiezoelectric element 3.FIG. 5B shows thepiezoelectric layer 501 and theupper electrode film 400 on thepiezoelectric layer 501 that have been formed in the steps so far. - Then, in the state shown in
FIG. 5B , photo-etching is performed on theupper electrode film 400 and thepiezoelectric layer 501 to make patterning that leaves a specific thickness of the piezoelectric layer that covers thelower electrode film 2 and the upper electrode film on the piezoelectric layer. That is, a recess that corresponds to theopening 5 a is formed. In this embodiment, etching of the piezoelectric layer for forming theopening 5 a is referred to as “first etching process of the piezoelectric layer” as appropriate.FIG. 5C shows thepiezoelectric layer 502 and theupper electrode film 401 on thepiezoelectric layer 502 that have been formed in the steps so far. - Then, in the state shown in
FIG. 5C , photo-etching is performed on theupper electrode film 401 and thepiezoelectric layer 502 to form the throughhole 5 b that allows part of thelower electrode film 2 to be exposed. In this embodiment, etching of the piezoelectric layer for forming the throughholes 5 b is referred to as “second etching process of the piezoelectric layer” as appropriate.FIG. 6A shows thepiezoelectric layer 5 and theupper electrode film 402 on thepiezoelectric layer 5 that have been formed in the steps so far. As shown inFIG. 6A , the throughhole 5 b penetrates through thepiezoelectric layer 5 and theupper electrode film 402. According to this embodiment, in the state subsequent to that shown inFIG. 5B , etching of the piezoelectric layer for forming theopening 5 a and etching of the piezoelectric layer for forming the throughhole 5 b are separately performed, whose reason will be described later. - Then, in the state shown in
FIG. 6A , the upper electrode film is further formed to a thickness required in the resultantpiezoelectric element 3, for example, by a sputtering technique. After that, photo-etching is performed on the upper electrode film to make patterning on the upper electrode film so as to form a specific pattern that corresponds to the respective positions where thepressure generating chambers 12 are to be formed and a specific pattern that includes the range of the respective through holes (seeFIG. 3 ).FIG. 6B shows theupper electrode film 4 that has been formed by the above-mentioned patterning. Then, in the state shown inFIG. 6B , a metal layer (for example, the metal layer including gold (Au) and Nichrome (NiCr)) which is a material of thelead electrodes lead electrodes lead electrode 60 is connected to theupper electrode film 4. On the other hand, thelead electrode 61 is connected to thelower electrode film 2 via the throughhole 5 b and the upper electrode film 4 (FIG. 6B ) formed on the surface of the throughhole 5 b. The upper electrode film 4 (FIG. 6B ) formed on the surface of the throughhole 5 b serves as part of the wirings that connect thedrive circuit 120 and the individual electrode (the lower electrode film 2). -
FIG. 6C shows a configuration that has been formed in the steps so far. The configuration shown inFIG. 6C is consistent with the configuration of thepiezoelectric element 3 shown inFIG. 2 andFIG. 3 . Then, therecording head 1 is completed through the steps such as connecting of theprotective substrate 30 on the side of thepiezoelectric element 3, forming of thepressure generating chambers 12, theink supply paths 14 and the like by etching thesubstrate 10, connecting of thenozzles plate 20 on thesubstrate 10, and connecting of thecompliance substrate 40 on theprotective substrate 30. It should be noted that the above-mentioned manufacturing method of therecording head 1 is merely an example, and various modifications are possible. The forming method of the piezoelectric layer is also not limited to that described above, and a sputtering technique may also be used. Further, the material of the piezoelectric layer may include various materials, for example, lead zirconate titanate based material and non-lead (lead-free) perovskite oxide such as barium titanate. - Then, the reason of the first etching process of the piezoelectric layer and the second etching process of the piezoelectric layer being separately provided in the above-mentioned manufacturing method will be described. When the
piezoelectric layer 501 is formed so as to cover thelower electrode film 2 and theinsulator film 55 around thelower electrode film 2 as shown inFIG. 5B , it is not always possible due to manufacturing accuracy to easily make the thickness of thepiezoelectric layer 501 on theinsulator film 55 and the thickness of thepiezoelectric layer 501 on thelower electrode film 2 to be the same. Particularly, uneven thickness of those layers becomes significant when the piezoelectric layer is formed by using liquid, typically by a sol-gel process. Accordingly, the optimum etching amount of thepiezoelectric layer 501 to expose the insulator film 55 (to form theopening 5 a) is different from the optimum etching amount of thepiezoelectric layer 501 to expose the lower electrode film 2 (to form the throughhole 5 b). If etching for exposing theinsulator film 55 and etching for exposing thelower electrode film 2 are simultaneously performed, one of theinsulator film 55 and thelower electrode film 2 may suffer from over etching (excessive etching) and the other may suffer from under etching (insufficient etching), since it is difficult to precisely control the etching amount at each location. - For example, when the thickness of the
piezoelectric layer 501 on theinsulator film 55 is greater than the thickness of thepiezoelectric layer 501 on thelower electrode film 2 and etching of those layers are simultaneously performed, thelower electrode film 2 suffers from over etching during removing of thepiezoelectric layer 501 on theinsulator film 55, which may cause breakage of thelower electrode film 2. Further, in an attempt to prevent over etching of thelower electrode film 2, theinsulator film 55 may fail to be exposed. Alternatively, when the thickness of thepiezoelectric layer 501 on theinsulator film 55 is smaller than the thickness of thepiezoelectric layer 501 on thelower electrode film 2 and etching of those layers are simultaneously performed, theinsulator film 55 suffers from over etching during removing of thepiezoelectric layer 501 on thelower electrode film 2. As a result, theopening 5 a is thinner than the required thickness and fails to obtain the required rigidity, which may cause cracking on theopening 5 a. Further, in an attempt to prevent over etching of theinsulator film 55, thelower electrode film 2 may fail to be exposed. - Therefore, in this embodiment, the first etching process of the piezoelectric layer and the second etching process of the piezoelectric layer are separately provided so that optimum etching amount of the piezoelectric layer is set to obtain the thickness for each area to be processed in each process. Accordingly, optimum etching of the
piezoelectric layer 501 to form theopening 5 a and optimum etching of thepiezoelectric layer 501 to form the throughhole 5 b can be achieved, thereby preventing the above-mentioned over etching and under etching from occurred. The first etching process of the piezoelectric layer and the second etching process of the piezoelectric layer may be performed in the order opposite to that is described in the above description. - The invention is not limited to the above-mentioned embodiment and can be implemented in various embodiments within the scope of the invention without departing from its principle. For example, the following modified example can be implemented. Further, the various embodiments and modified examples which are combined as appropriate are also within the scope of the invention. In the following description, differences from the above-mentioned embodiment will be described, and configurations and effects which are the same as those of the above-mentioned embodiment will be omitted as appropriate.
-
FIG. 7 is a plan view of an area on thesubstrate 10 according to a modified example, and similarly toFIG. 3 , shows the area in which thepiezoelectric element 3 that corresponds to onepressure generating chamber 12 is formed. The configuration ofFIG. 7 and the configuration ofFIG. 3 are different in that they have different lengths of theopening 5 a in the longitudinal direction. Specifically, theopening 5 a ofFIG. 7 is longer than that ofFIG. 3 , and theopening 5 a ofFIG. 7 is formed to extend to the outside of thepressure generating chamber 12 in the longitudinal direction. That is, inFIG. 7 , the length L3 of theopening 5 a in the longitudinal direction is formed to include the length L2 of thepressure generating chamber 12. With this configuration, a rigidity of thepiezoelectric element 3 at the proximity of both ends of thepressure generating chambers 12 in the longitudinal direction decreases, and a displacement amount of thepiezoelectric element 3 at the proximity of both thepressure generating chamber 12 increases. -
FIG. 8 is a view which explains an effect of the modified example.FIG. 8 illustrates the positional relationship between thepressure generating chamber 12 in the longitudinal direction and theelastic film 51 that closes the upper portion of thepressure generating chamber 12 in a simplified manner. When a voltage is applied to thepiezoelectric element 3 that is formed to correspond to thepressure generating chamber 12 to drive the active section, the active section displaces and theelastic film 51 flexes into thepressure generating chamber 12. The difference between the position before theelastic film 51 flexes (the position of theelastic film 51 indicated by the solid line inFIG. 8 ) and the position after theelastic film 51 flexes in the up-down direction is the displacement amount Ah. Further, inFIG. 8 , the positions of the flexed elastic film is illustrated by the dotted line and the dashed two dotted line. The position indicated by the dotted line shows the position in a configuration in which the length L3 of theopening 5 a is within the length L2 of thepressure generating chambers 12, while the position indicated by the dashed two dotted line shows the position in a configuration (configuration ofFIG. 7 ) in which the length L3 of theopening 5 a includes the length L2 of thepressure generating chamber 12. - As seen from
FIG. 8 , the displacement amounts Ah at the center of thepressure generating chamber 12 in the longitudinal direction is substantially the same regardless of the above-mentioned difference of the length L3 of theopening 5 a. On the other hand, the displacement amounts Ah at the end portions of thepressure generating chambers 12 are different such that the displacement amounts Δh are larger in the configuration in which the length L3 of theopening 5 a is longer than the length L2. When the displacement amounts Δh at the end portions of thepressure generating chambers 12 increases, the amount of liquid ejected by flexing of thepiezoelectric element 3. That is, according to the modified example shown inFIG. 7 , performance of therecording head 1 can be improved by increasing the amount of liquid ejected. Moreover, in the configuration shown inFIG. 7 , a vertical sectional view taken along the line IVB-IVB is the same as that ofFIG. 4B . Further, in a vertical sectional view taken along the line IVA-IVA and a vertical sectional view taken along the line IVC-IVC, theopening 5 a is formed similarly to the vertical sectional view taken along the line IVB-IVB, and theupper electrode film 4 and thelead electrode 60 are disposed on theopening 5 a. - The above-mentioned
recording head 1 constitutes part of a recording head unit having ink flow paths that communicate with the ink cartridge and the like and is mounted on an ink jet recording apparatus which is a liquid ejection apparatus.FIG. 9 is a schematic view of an example of the ink jet recording apparatus. As shown inFIG. 9 ,cartridges recording head units carriage 16 on which therecording head units carriage shaft 18 that is formed on anapparatus body 17 so as to be movable along thecarriage shaft 18. Therecording head units drive motor 19 is transmitted to thecarriage 16 via a plurality of gears (not shown in the figure) and atiming belt 7, thecarriage 16 on which therecording head units carriage shaft 18. Further, aplaten 8 is provided along thecarriage shaft 18 in theapparatus body 17 such that a recording sheet S which is a recording medium such as a sheet of paper fed by a feeding roller and the like, which are not shown in the figure, is transported on theplaten 8. - Although the ink jet recording head has been described as an example of the liquid ejection head of the invention, the liquid ejection head is not limited thereto. The invention is generally directed to liquid ejection heads, and as a matter of course, can be applied to heads that ejects liquid other than ink. Other liquid ejection heads may include, for example, various recording heads used for image recording apparatuses such as printers, color material ejection heads used for manufacturing color filters for liquid crystal displays and the like, electrode material ejection heads used for manufacturing electrodes for organic electroluminescence (EL) displays, field emission displays (FEDs) and the like, and bioorganic ejection heads used for manufacturing biochips.
- Further, the piezoelectric element of the invention is not limited to that used for the liquid ejection head, and can be used for other devices. Other devices may include, for example, ultrasonic devices such as ultrasonic transmitters, ultrasonic motors, temperature-electricity converters, pressure-electricity converters, ferroelectric transistors, piezoelectric transducers, block filters for harmful rays such as infrared ray, optical filters using photonic crystal effect by quantum dot structure, and optical filters using thin film light interference. Further, the invention is also applicable to piezoelectric elements used for sensors, and piezoelectric elements used for ferroelectric memories. Sensors that use a piezoelectric element may include, for example, infrared sensors, ultrasonic sensors, thermo-sensitive sensors, pressure sensors, pyroelectric sensors and gyro sensors (angular rate sensors).
Claims (8)
1. A liquid ejection head comprising:
a substrate in which a pressure generating chamber that communicates with a nozzle opening is formed; and
a piezoelectric element having a piezoelectric layer, a first electrode that is formed on a surface of the piezoelectric layer on a side of the substrate so as to correspond to the pressure generating chamber, and a second electrode that is formed on a surface of the piezoelectric layer opposite to the side on which the first electrode is formed so as to extend over a plurality of the pressure generating chambers, wherein the second electrode is formed to extend to an outside of the pressure generating chamber in a longitudinal direction of the pressure generating chamber.
2. The liquid ejection head according to claim 1 wherein an area where the first electrode, the piezoelectric layer and the second electrode overlap is formed to extend to an outside of the pressure generating chamber in the longitudinal direction.
3. The liquid ejection head according to claim 1 wherein an opening is formed on the piezoelectric layer by removing the piezoelectric layer at a position that substantially corresponds to an area between the pressure generating chambers, and the opening is formed to extend to an outside of the pressure generating chamber in the longitudinal direction.
4. The liquid ejection head according to claim 1 wherein a metal layer that is disposed on the second electrode and serves as a wiring is formed to extend to both inside and outside of the pressure generating chamber.
5. A liquid ejection apparatus comprising the liquid ejection head according to claim 1 .
6. A liquid ejection apparatus comprising the liquid ejection head according to claim 2 .
7. A liquid ejection apparatus comprising the liquid ejection head according to claim 3 .
8. A liquid ejection apparatus comprising the liquid ejection head according to claim 4 .
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US14/839,070 US20150367643A1 (en) | 2012-02-01 | 2015-08-28 | Liquid ejection head and liquid ejection apparatus |
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US15/296,404 US10059101B2 (en) | 2012-02-01 | 2016-10-18 | Liquid ejection head and liquid ejection apparatus |
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US14/244,250 US20140210916A1 (en) | 2012-02-01 | 2014-04-03 | Liquid ejection head and liquid ejection apparatus |
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US9757943B2 (en) | 2014-12-26 | 2017-09-12 | Brother Kogyo Kabushiki Kaisha | Liquid jet apparatus and method for manufacturing liquid jet apparatus |
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JP5494953B2 (en) * | 2010-03-26 | 2014-05-21 | セイコーエプソン株式会社 | Piezoelectric actuator and manufacturing method thereof, liquid jet head, and liquid jet apparatus |
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-
2012
- 2012-02-01 JP JP2012019569A patent/JP5957914B2/en active Active
-
2013
- 2013-01-31 EP EP13153508.0A patent/EP2623323B1/en active Active
- 2013-01-31 CN CN201310042767.6A patent/CN103240994B/en active Active
- 2013-01-31 US US13/755,342 patent/US8727510B2/en active Active
-
2014
- 2014-04-03 US US14/244,250 patent/US20140210916A1/en not_active Abandoned
- 2014-12-10 US US14/565,942 patent/US9144977B2/en active Active
-
2015
- 2015-08-28 US US14/839,070 patent/US20150367643A1/en not_active Abandoned
- 2015-11-16 US US14/941,929 patent/US9498952B2/en active Active
-
2016
- 2016-10-18 US US15/296,404 patent/US10059101B2/en active Active
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9757943B2 (en) | 2014-12-26 | 2017-09-12 | Brother Kogyo Kabushiki Kaisha | Liquid jet apparatus and method for manufacturing liquid jet apparatus |
US10131144B2 (en) | 2014-12-26 | 2018-11-20 | Brother Kogyo Kabushiki Kaisha | Liquid jet apparatus and method for manufacturing liquid jet apparatus |
US10493760B2 (en) | 2014-12-26 | 2019-12-03 | Brother Kogyo Kabushiki Kaisha | Liquid jet apparatus and method for manufacturing liquid jet apparatus |
Also Published As
Publication number | Publication date |
---|---|
US9144977B2 (en) | 2015-09-29 |
US20150367643A1 (en) | 2015-12-24 |
US20160075137A1 (en) | 2016-03-17 |
CN103240994A (en) | 2013-08-14 |
US8727510B2 (en) | 2014-05-20 |
JP2013158909A (en) | 2013-08-19 |
CN103240994B (en) | 2015-09-30 |
US10059101B2 (en) | 2018-08-28 |
EP2623323A1 (en) | 2013-08-07 |
JP5957914B2 (en) | 2016-07-27 |
EP2623323B1 (en) | 2015-03-04 |
US20170036446A1 (en) | 2017-02-09 |
US9498952B2 (en) | 2016-11-22 |
US20130194353A1 (en) | 2013-08-01 |
US20150085024A1 (en) | 2015-03-26 |
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