LIQUID EJECTION HEAD

According to one embodiment, a liquid ejection head includes an actuator with a plurality of pressure chambers spaced from each other in a first direction. Each pressure chamber extends lengthwise in a second direction intersecting the first direction. An anti-reflection film is on an inner surface of the pressure chambers. A diaphragm portion is at an end of each pressure chamber. The diaphragm portion provides a flow cross-section that is less than the pressure chamber and is between the pressure chamber and a common chamber to which the pressure chambers are fluidly connected.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2023-026507, filed on Feb. 22, 2023, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a liquid ejection head.

BACKGROUND

In recent years, demand for high productivity from inkjet heads has increased, and increasing speeds and amounts of ejected liquid droplets has become an issue. A shear-mode shared-wall type inkjet head has high ejection power and is suitable for ejecting high-viscosity ink and large droplets. In the shear-mode shared-wall type inkjet head, the same driving column is shared by two adjacent pressure chambers, and groups of ⅓ of the total number of arranged chambers are driven at the same time. That is, a so-called three-cycle drive is commonly used. Independent drive heads have also been developed in which dummy pressure chambers are on both sides of a pressure chamber to be driven and two drive columns are used to drive each pressure chamber. A structure for inkjet heads has been developed in which a large number of grooves are formed in a piezoelectric body, the outlet/inlet of each groove is blocked for every other one of the grooves. The grooves without blocking of the outlet/inlet are used as the pressure chambers which can be independently driven, and the blocked grooves are used as air chambers (dummy pressure chambers).

In such an inkjet head, the ink is supplied from a common liquid chamber to a pressure chamber after ink liquid droplets have been ejected. In this process, a phenomenon may occur by which the nozzle overshoots and the meniscus rises. The smaller the fluid resistance of the flow path from the common liquid chamber to the nozzles, the greater the overshoot will be, and thus, if the overshoot is not accounted for, the meniscus cannot be in a stable state for ejections. Therefore, in order to increase a speed of the inkjet head, it is required to quickly ensure stable ejection characteristics. Although, there is a method of forming a diaphragm portion using a photosensitive resin at an opening of the groove (outlet/inlet of the pressure chamber) as a means of increasing the fluid resistance, due to the effects of light reflection from the bottom and the side walls of the pressure chamber during the exposure process for forming the diaphragm portion, it may be difficult to form the diaphragm portion with high precision because unintended portions of the photosensitive reason may be exposed by reflections and the like.

DETAILED DESCRIPTION

The present embodiment relates to a liquid ejection head with stable ejection characteristics.

According to one embodiment, a liquid ejection head includes an actuator with a plurality of pressure chambers spaced from each other in a first direction. Each pressure chamber extends lengthwise in a second direction intersecting the first direction. An anti-reflection film is on an inner surface of the pressure chambers. A diaphragm portion is at an end of each pressure chamber. The diaphragm portion provides a flow cross-section that is less than the pressure chamber and is between the pressure chamber and a common chamber to which the pressure chambers are fluidly connected.

Hereinafter, a configuration of an inkjet head10, which is a liquid ejection head according to a first embodiment, will be described with reference toFIGS.1to6.FIG.1is a perspective view illustrating the inkjet head according to the first embodiment.FIG.2is an exploded view of a portion of the inkjet head.FIG.3is an enlarged view illustrating a portion of the inkjet head.FIGS.4and5are enlarged cross-sectional views illustrating aspects of the inkjet head.FIG.6depicts aspects related to a method for manufacturing an inkjet head.FIG.7depicts aspects related to the inkjet heads according to an embodiment and a comparative example.FIG.8is a schematic diagram illustrating an inkjet printer, which is one type of a liquid ejection device. It is noted that, in the present description, the nozzles28and the pressure chambers31of the inkjet head10are arranged along the X axis, the pressure chambers31extend lengthwise along the Y axis, and the liquid ejection direction is along the Z axis. These depictions are for purposes of description, and embodiments are not limited thereto.

The inkjet head10is a device for ejecting ink, and is mounted, for example, inside an inkjet printer. The inkjet head10is a shear-mode shared-wall type inkjet head. For example, the inkjet head10is an independently driven inkjet head type in which pressure chambers31and air chambers32are alternately arranged. The air chamber32is a chamber (void) into which ink is not supplied and does not need to have any nozzles28. In the present embodiment, the inkjet head10is a so-called side shooter type inkjet head.

The inkjet head10has an actuator base11, a nozzle plate12, and a frame13. The actuator base11is an example of a base material. An ink chamber27is inside the inkjet head10. In the present example, ink is the liquid ejected by inkjet head10, but embodiments are not limited to ink.

The inkjet head10may include or incorporate components such as a circuit board17for controlling the operations of the inkjet head10and a manifold18forming a portion of the path between the inkjet head10and an ink tank (reservoir).

As illustrated inFIGS.2to5, the actuator base11includes a board21and a pair of actuator portions22.

The board21is formed in a rectangular plate shape from a ceramic such as alumina. The board21has a flat mounting surface. The pair of actuator portions22are joined to the mounting surface of the board. A plurality of supply holes25and a plurality of discharge holes26are formed in the board21.

As illustrated inFIGS.2and3, a pattern wiring211is formed on the board21of the actuator base11. The pattern wiring211is formed of, for example, a nickel thin film. The pattern wiring211is configured in a predetermined pattern shape to be connected to an electrode layer34(electrode) formed on the actuator portion22. Portions of the pattern wiring211may be individually addressable segments or portions connected in common with other portions of the pattern wiring211.

The supply holes25are provided to be aligned in the longitudinal direction of the actuator portions22in a central (middle) portion of the board21. The supply holes25are between the pair of actuator portions22in the X direction. The supply hole25communicates with (fluidly connects to) an ink supply portion (inlet side) of the manifold18. The supply hole25is connected to the ink tank via the ink supply portion. The supply hole25receives the ink from the ink tank to the ink chamber27. It is noted that the supply holes25are not limited to a plurality of circular holes as illustrated inFIG.2, and, in some examples, a long hole (elongated hole or oval) extending in the X direction along the actuator portion22may be used.

The discharge holes26are aligned in two columns with the supply hole25and the pair of the actuator portions22interposed therebetween. The discharge hole26communicates with the ink discharge portion (outlet side) of the manifold18. The discharge hole26is connected to the ink tank through the ink discharge portion. The discharge hole26permits return of the ink from the ink chamber27to the ink tank.

A pair of the actuator portions22are adhered to the mounting surface of the board21. The actuator portions22are aligned in two columns on the board21with the supply holes25interposed therebetween. Each actuator portion22is formed of two plate-like piezoelectric bodies made of, for example, lead zirconate titanate (PZT). The two piezoelectric bodies are bonded together so that polarization directions thereof are opposite to each other in the thickness direction. The actuator portion22is adhered to the mounting surface of the board21with, for example, a thermosetting epoxy adhesive. As illustrated inFIG.2, the actuator portions22are aligned with a column of nozzles28. The actuator portion22divides the ink chamber27into a first common chamber271on which the supply hole25opens and a second common chamber272on which the discharge hole26opens. The first common chamber271is shared by the pair of actuator portions22and a second common chamber272is to outside of each actuator portion22.

The actuator portion22slopes gradually increased from a top surface portion222side toward the board side. The cross-sectional shape along a direction (lateral direction) perpendicular to the longitudinal direction of the actuator portion22is a trapezoidal shape. The side surface portion221of the actuator portion22has inclined surfaces that are angled. The top surface portion222of the actuator portion22can be adhered to the nozzle plate12via an adhesive layer291as illustrated inFIG.6.

The actuator portion22includes a diaphragm portion240provided at the outlet/inlet of the respective pressure chambers31. The actuator portion22has a plurality of element walls33(side walls) and has grooves14forming pressure chambers31and air chambers32between the element walls33. The element wall33between adjacent grooves14functions as a driving element of a pressure chamber31.

As illustrated inFIGS.1to5, the bottom surface of the groove14and the main surface of the board21are connected by inclined side surface portions221. The plurality of pressure chambers31and the plurality of air chambers32are arranged alternately with each other. Each of the pressure chambers31and the air chambers32extend in a direction crossing the longitudinal direction of the actuator portion22and arranged in parallel in the longitudinal direction (X direction) of the actuator portion22. The grooves14forming the pressure chambers31and the air chambers32can be formed by a dicer (e.g., a saw blade), and the bottom portions of the grooves14thus formed may have a curved surface shape having a radius of curvature (R). In the present embodiment, for example, with respect to the groove14, a width dimension in the X direction is configured to be constant up to almost the bottom of the groove14, thereafter the groove14is a gently curved surface, and a cross section perpendicular to the Y direction, has a U-type shape. It is noted that in other examples the groove14may have a constant width for its entire depth, or the groove may have a fully rectangular cross section, that is, a flat bottom surface.

It is noted that the shape of the pressure chamber31and the shape of the air chamber32may be different in some examples. The element wall33is formed between an adjacent pressure chamber31and air chamber32and deforms in response to the drive signal to change the volume of the pressure chamber31.

The electrode layers34are provided on the inner wall surfaces of the pressure chamber31and the air chamber32of the actuator base11, respectively. The electrode layer34is formed, for example, of a conductive film such as a nickel thin film. The electrode layer34extends from an inner surface of the groove14onto the board21and is connected to the pattern wiring211. For example, the electrode layer34is formed at least on the side surface portion of the element wall33, that is, a side wall surface of the groove14constituting the pressure chamber31. The electrode layer34may be formed, for example, on both the side surface portion and the bottom surface portion of the pressure chamber31.

An anti-reflection film (light anti-reflection film)35is formed on the electrode layer34on the inner wall surface of the pressure chamber31of the actuator base11. For example, the anti-reflection film35is formed of a film having a higher light absorbance (or less reflectivity) than the electrodes. For example, the anti-reflection film35is formed at least on the side surface portions of the element walls33, that is, on the side wall surfaces and bottom surfaces of the grooves14constituting the pressure chambers31. The anti-reflection film35may be formed, for example, on a portion of the side surface portion and the bottom surface portion of the pressure chamber31. The anti-reflection film35is formed at least on the electrode layer34. The electrode layer34is formed between the element wall33and the anti-reflection film35.

The anti-reflection film35is made of a material having a high light absorbance at the relevant wavelengths (photolithographically relevant wavelengths). The anti-reflection film has a higher light absorbance than the electrode layer34. The anti-reflection film may be made of an organic material or may be an inorganic material. In the case of an organic material, the anti-reflection film may be formed by a film formation technique such as spray coating, vapor deposition, or the like, and in the case of an inorganic material, the anti-reflection film may be formed by sputtering, vapor deposition, or the like. As the anti-reflection film35, an adhesive based on an epoxy resin or the like may be used.

The plurality of pressure chambers31communicate with the plurality of nozzles28of the nozzle plate12joined to the top of the element wall33. Both ends of the pressure chamber31communicate with the ink chamber27. More particularly, one end opens to the first common chamber27127and the other end opens to the second common chamber272. Therefore, the ink flows in from one end of the pressure chamber31and out from the other end. The diaphragm portion240has a diaphragm port242designed to provide a larger fluid resistance than the inside of the unobstructed pressure chamber31. The diaphragm port242is formed at the open ends (communication ports) of the pressure chamber31to be between the pressure chamber31and the ink chamber27. As an example, in the present embodiment, the diaphragm portions240are formed at both ends of the pressure chamber31.

As illustrated inFIGS.4and5, the diaphragm portion240is to narrow (partially block) the opening of the pressure chamber31connected to the ink chamber27in the X direction. As an example, the diaphragm portion240forms the diaphragm port242which has a slit-shaped opening with protruding portions241serving as a diaphragm wall. The protruding portions are formed from a photosensitive resin. For example, the protruding portion241is formed from photosensitive resin coated over the anti-reflection film35.

The protruding portion241protrudes outwardly from the element wall33into the groove14at the end of the pressure chamber31. In the present embodiment, the protruding portions241are on an adjacent pair of the element walls33forming both sides of the pressure chamber31, that is, the element walls33on both sides of the groove14.

For example, the protruding portion241may be formed over the entire depth of the groove14or may be formed partially in the depth direction.

The groove14is not completely blocked by the protruding portions241. The diaphragm port242is formed between the pair of the protruding portions241. The diaphragm port242provides a flow path cross-sectional area that is less than the flow path cross-sectional area of the pressure chamber31. That is, the protruding portions241increase fluid resistance.

The diaphragm portion240can be formed by forming a photosensitive resin film244on the anti-reflection film35on the inner walls of the pressure chambers31and the air chambers32, and then curing the portions to form the protruding portions241in an exposure process.

It is noted that, if the fluid resistance of the diaphragm portion240is too large, the supplying of the ink to the pressure chamber31after the ejection of the ink liquid droplets will be delayed, which will hinder the speeding up of the ejection process. In addition, the swelling of the meniscus depends on the ink viscosity, the ejection volume, the drive frequency, and the like. Therefore, the shape of the protruding portion241and the size and position of the diaphragm port242may be set so as to provide fluid resistance according to particular expected ink supplying conditions and meniscus swelling characteristics. It is noted that, in some examples, the diaphragm portions240on opposite sides or ends may have different configurations. In an example, each of the projections241provided on the sides of a communication port of the pressure chamber31has a rectangular cross-section and a uniform cross-sectional shape along the depth direction.

The air chamber32is closed (covered) by the nozzle plate12joined to the top. In addition, both ends of the plurality of air chambers32are blocked by a cover portion23made of, for example, a photosensitive resin material. That is, between the first common chamber271and the air chamber32and between the second common chamber272and the air chamber32, the cover portion23is arranged so the air chamber32is separated from the ink chamber27. For this reason, ink does not flow into the air chamber32.

For example, the cover portion23is formed by applying photosensitive resin to both ends of the air chamber32in the same process as used for the formation of the protruding portions241. In other examples, the cover portion23may be formed in a separate process from the protruding portions241.

In some examples, the protruding portion241and the cover portion23may be formed to extend outward in the Y direction from both ends of the groove14sand these portions may be integrally continuous.

The nozzle plate12is formed of, for example, a rectangular film made of polyimide. The nozzle plate12faces the mounting surface of the actuator base11. The plurality of nozzles28are formed in the nozzle plate12so as to penetrate the nozzle plate12in the thickness direction.

In this example, a nozzle28is provided for each of the pressure chambers31on a one-to-one basis. The respective nozzle opens on the pressure chamber31. The plurality of nozzles28are aligned along the first direction and arranged in two columns corresponding to the pair of the actuator portions22. Each nozzle28is configured in a tubular shape with an axis extending in the Z direction. For example, the nozzle28may have a constant diameter or may have a shape tapering toward the central portion or the tip portion. The nozzles28are arranged to face the middle of the pressure chambers31. In some examples, nozzles28may be arranged at alternating ends of the pressure chambers31.

The frame13is made of, for example, a nickel alloy and has a rectangular shape. The frame13is interposed between the mounting surface of the actuator base11and the nozzle plate12. The frame13is adhered to the mounting surface of the actuator base11and the nozzle plate12, respectively. That is, the nozzle plate12is attached to the actuator base11via the frame13.

The manifold18is joined to the opposite side of the actuator base11from the nozzle plate12. Inside the manifold18, an ink supply unit, which is a flow path communicating with the supply hole25, and an ink discharge portion, which is a flow path communicating with the discharge hole26, are formed.

The circuit board17in this example is a film carrier package (FCP). The circuit board17has a flexible resin film51on which a plurality of wirings are formed and a driving IC52connected to the plurality of wirings of the film51. The driving IC52is electrically coupled to the electrode layers34via the wiring of the film51and the pattern wiring211.

The ink chamber27surrounded by the actuator base11, the nozzle plate12, and the frame13is formed inside the inkjet head10configured as described above. That is, the ink chamber27is formed between the actuator base11and the nozzle plate12. For example, the ink chamber27is divided into three sections in the second direction by the two actuator portions22and includes two second common chambers272as common chambers opened to the discharge holes26and the first common chamber271as a common chamber opened to the supply holes25. The first common chamber271and the second common chamber272communicate with the plurality of the pressure chambers31.

In the inkjet head10, ink circulates between the ink tank and the ink chamber27through the supply hole25, the pressure chamber31, and the discharge hole26. For example, the driving IC52applies a drive voltage to the electrode layer34of a pressure chamber31via the wiring of the film51in response to a signal input from a control unit of an inkjet printer, and thus, a potential difference occurs between the electrode layer34on the pressure chamber31and the electrode layer34on the air chamber32, so that the element wall33is selectively deformed in a shear mode. By deforming the element wall33in response to the drive signal, the volume of the pressure chamber31is changed.

Due to the shear mode deformation of the element wall33, the volume of the pressure chamber31can be increased, and thus, the pressure is decreased. Accordingly, the ink from the ink chamber27flows into the pressure chamber31.

While the volume of the pressure chamber31is increased, the driving IC52applies a drive voltage of opposite potential to the electrode layer34of the pressure chamber31. Accordingly, due to the shear mode deformation of the element wall33, the volume of the pressure chamber31is decreased, and thus, the pressure is increased. Accordingly, the ink in the pressure chamber31is ejected from the nozzle28.

As a method for manufacturing the inkjet head10, a piezoelectric member can first be attached to the plate-like board21with an adhesive or the like, and a machining process using a dicing saw, a cutting blade, or the like is performed to form the grooves14and the like in the piezoelectric member on the actuator base11. It is noted that, for example, a block-shaped base member having a thickness corresponding to a plurality of sheets may be formed in advance and then divided to manufacture a plurality of actuator bases11having a predetermined shape.

Subsequently, the electrode layer34and the pattern wiring211are formed on the inner surfaces of the grooves14and the front surface of the board21.

The anti-reflection film35is also formed on the electrode layer34on the inner surface of the grooves14constituting at least the pressure chambers31. As described above, the electrode layer34and the pattern wiring211are formed at predetermined locations on the surface of the actuator base11, and the electrode layer34is covered with the anti-reflection film35on the inner surface of the groove14.

Next, the diaphragm portion240is formed at the ends of the pressure chambers31. For example, a method for forming the diaphragm portion240includes forming a photosensitive resin film in the grooves14constituting the pressure chambers31and followed by an exposure and development process to shape the diaphragm portion240as intended.

As a film forming process, as illustrated in Act11inFIG.6, a photosensitive resin film244is formed on the inner wall of the pressure chamber31. For example, the photosensitive resin film244may reach the outside of the groove14in the extension direction and may be integrally continuous outside the groove14.

Subsequently, as the patterning process, the photosensitive resin films244are patterned on both ends of the pressure chamber31by selective exposure followed development processes. For example, in the present embodiment, after curing the portions2441constituting the protruding portions241, the diaphragm portion240having the protruding portions241is formed by performing a development processing in which unexposed portions are dissolved and removed.

In the exposure process of the patterning process, if necessary, a photomask245may be used in an ultraviolet exposure process. Such a exposure process may be repeated as necessary. The conditions of exposure direction, exposure intensity, and the like may be appropriately set. For example, as the exposure process, as illustrated in Act11, the photomask245is arranged on the top side of the element wall33, and exposure is performed from the top side through the photomask245. Then, the exposure is performed to the depth reaching the bottom of the groove14, so that the photosensitive resin film244of the portion2441constituting the protruding portion241is cured, and thus, only the portion2442corresponding to the diaphragm port242is left uncured. As an example, by setting the exposure direction in the depth direction of the pressure chamber31, the protruding portions241on both sides can be exposed to be patterned at the same time.

Since the inner surface of the groove14was covered with the anti-reflection film35beforehand, the portions other than the intended exposure portions are prevented from being irradiated with the reflected light. That is, the effects of the reflection of the light from the bottom and the side walls of the pressure chamber31during the exposure are reduced so that a desired exposure pattern can be formed. In the example illustrated by the Comparative Example 1 inFIG.7, without the anti-reflection film, the light is reflected at various angles inside the groove by the curved bottom surface and sidewalls. The photosensitive resin may be inadvertently exposed by such reflected light, so that it may be difficult to obtain a desired shape when forming the diaphragm240portion of the like. For example, in the case of forming the diaphragm portion240inside the groove14with a photosensitive resin, from the viewpoint of ensuring adhesion, a larger exposure amount is generally better, but the risk of shape defects due to the reflected light is increased with increased exposure amount. That is, without the light anti-reflection film, it is difficult to form the diaphragm in the desired shape since the ultraviolet rays will be reflected by the electrode surfaces on the bottom and the side walls of the pressure chamber31.

On the other hand, as illustrated inFIG.7, in the inkjet head10of the present embodiment, the anti-reflection film35is formed inside the groove14, and thus, the ultraviolet light used when forming the diaphragm portion240is absorbed by the anti-reflection film35, so that the shape defects that might otherwise occur due to reflected light can be suppressed.

By washing away unexposed resin with a developer solution, as illustrated in Act12, the diaphragm portion240is formed at the outlet/inlet of the pressure chamber31.

As described above, a protruding portion241made of a resin film is formed at the outlet/inlet of the pressure chamber31, and a diaphragm portion240is formed between the protruding portions241.

The diaphragm portion240and the cover portion23may be formed together at the same time in the same processing. Alternatively, the cover portion23may be formed in a separate process before or after the diaphragm portion240. In the present embodiment, the photosensitive resin film244is continuous outside the groove14, and thus, the cover portion23and the adjacent protruding portions241are formed continuously and integrally.

The actuator base11is assembled to the manifold18, and the frame13is attached to one surface of the board21of the actuator base11with a thermoplastic resin adhesive sheet.

Then, the assembled frame13, the top of the element wall33of the actuator portion22, and the surface of the protruding portion241on the nozzle plate12side are polished so as to be the same surface level. Then, the nozzle plate12is adhered to the top of the element wall33, the frame13, and the polished surface of the protruding portion241. For example, the adhesive layer291is formed by applying the adhesive29on the surface of the nozzle plate12facing the pressure chambers31, and the nozzles28are position-aligned so as to face each other, and after affixing, the adhesive29can be cured after joining. As described above, the nozzle plate12is joined to the actuator portion22, and the adhesive layer291is provided between the element wall33and the nozzle plate12. As illustrated inFIG.1, the inkjet head10is completed by connecting the driving IC52and the circuit board17to the pattern wiring211formed on the main surface of the board21via a flexible printed circuit board or the like.

Hereinafter, an example of an inkjet printer100including the inkjet head10will be described with reference toFIG.8. The inkjet printer100includes a housing111, a medium supply unit112, an image forming unit113, a medium discharge unit114, a conveying device115, and a control unit116.

The inkjet printer100is a liquid ejection device that performs an image forming process on paper P by ejecting a liquid such as ink while conveying a paper P along a predetermined conveyance path A from the medium supply unit112through the image forming unit113to the medium discharge unit114.

The housing111constitutes an outer shell of the inkjet printer100. A discharge port for discharging the paper P to the outside is provided at a predetermined position of the housing111.

The medium supply unit112includes a plurality of paper feed cassettes to hold a plurality of sheets of the paper P of various sizes.

The medium discharge unit114includes a paper discharge tray to receive the paper P discharged from the discharge port.

The image forming unit113includes a supporting portion117for supporting the paper P during processing and a plurality of head units130arranged above the supporting portion117.

The supporting portion117includes a conveying belt118provided in a loop shape in a predetermined area for image formation, a supporting plate119supporting the conveying belt118from the back side, and a plurality of belt rollers120provided on the back side of the conveying belt118.

During the image formation, the supporting portion117supports the paper P and feeds paper P at a predetermined timing by rotation of the belt roller120, so that the paper P is carried to a downstream side by the conveying belt118.

The head unit130includes inkjet heads10for four different colors in this example, ink tanks132for each inkjet head10, a connection flow path133connecting the inkjet heads10and the ink tanks132, and a circulation pump134. The head unit130is a circulation type head unit that constantly circulates the liquid through the inkjet head10and returns the liquid to the respective ink tank132.

In the present embodiment, the inkjet heads10for cyan, magenta, yellow, and black are provided along with the ink tanks132that contain the respective inks of these colors. The ink tank132is connected to the inkjet head10by the connection flow path133. The connection flow path133includes a supply flow path connected to a supply port of the inkjet head10and a recovery flow path connected to the discharge port of the inkjet head10.

In addition, a negative pressure control device such as a pump is connected to the ink tank132. The negative pressure control device performs negative pressure control inside the ink tank132, so that the ink in each nozzle28of the inkjet head10has a predetermined meniscus shape. The meniscus control may be performed according to the hydrologic head values associated with the particular inkjet head10and the ink tank132.

The circulation pump134is, for example, a liquid feed pump such as a piezoelectric pump. The circulation pump134is provided in the supply flow path. The circulation pump134is connected to the drive circuit of the control unit116by wiring and is configured to be controllable under the control of a central processing unit (CPU) or the like. The circulation pump134circulates the liquid along a circulation flow path between the inkjet head10and the ink tank132.

The conveying device115conveys the paper P along the conveyance path A from the medium supply unit112through the image forming unit113to the medium discharge unit114. The conveying device115includes a plurality of guide plate pairs121arranged along the conveyance path A and a plurality of conveying rollers122.

Each of the guide plate pairs121may be a pair of plate members arranged to face each other with the paper P passing therebetween.

The conveying rollers122are driven under the control of the control unit116, so that the paper P is conveyed to the downstream side along the conveyance path A. It is noted that sensors for detecting the state of the paper may be arranged at various points along the conveyance path A.

The control unit116(controller) may be or include a control circuit such as a CPU, a read only memory (ROM) storing various programs, a random access memory (RAM) for temporarily storing various types of data, image data, and the like, and an interface unit receiving data from the outside and outputting data to the outside.

In the inkjet printer100, when the user provides a print instruction by operating a user interface, for example, the control unit116drives the conveying device115to convey the paper P and outputs a print signal to the head unit130at a predetermined timing, so that the inkjet head10is driven to form the intended image. For the ejection operation, the inkjet head10a drive signal is transmitted to the driving IC52according to an image signal corresponding to the intended image data, and a drive voltage is selectively applied to the electrode layer34of a pressure chamber31via the wiring to drive the element wall33of the actuator portion22, so that the ink is ejected from the nozzles28, and an image is formed on the paper P on the conveying belt118. Further, the control unit116drives the circulation pump134to circulate the liquid in the circulation flow path passing through the ink tank132and the inkjet head10.

According to an embodiment, ejection stability can be improved by forming a diaphragm portion240at the outlet/inlet of the pressure chamber31.

The diaphragm portion240has openings to the first common chamber271and the second common chamber272, which are chambers shared by the pressure chambers31. The flow path cross-sectional area of the diaphragm portion240is smaller than that of the pressure chambers31. For this reason, the swelling of the meniscus is reduced when the inkjet head10ejects the liquid. Therefore, the meniscus recovers quickly, and thus, the influence on the next ejection can be reduced, so that the ejection stability can be improved.

In addition, according to an embodiment, the diaphragm portion240can be formed by forming a photosensitive resin film in the grooves14on an anti-reflection film35and performing the patterning by an exposure process, so that the diaphragm portion240can be easily formed with a small number of processes, at low cost. Furthermore, since the thickness and shape of the protruding portion241can be selected relatively freely in exposure and development process, free designing of the fluid resistance of the diaphragm portion240is also facilitated. In addition, in an embodiment, since the side surface portion221of the actuator portion22in an inclined surface, the exposure direction is less restricted, and the exposure and development processes are facilitated. In addition, the anti-reflection film35formed on the surface of the electrode layer34may also be effective in protecting the electrode layer34and improving adhesion of the photosensitive resin.

In an embodiment, the diaphragm portion240for increasing the fluid resistance is configured to have the pair of protruding portions241formed on the wall surfaces of the element walls33on both sides of the pressure chamber31, but the shape of the diaphragm portion240is not limited thereto. For example, a protrusion may be formed on a portion of the bottom surface of the pressure chamber31or a portion on the nozzle plate12side, or the bottom of the pressure chamber31may be partially filled with the photosensitive resin. In an example, the diaphragm port242has a slit shape extending in the depth direction of the groove14, but the diaphragm port242may extend in other directions or may have other shapes such as circular and elliptic shapes instead of a generally rectangular slit. In addition, the diaphragm portions240on either side may have different configurations or shapes. For example, the diaphragm portion240may be only on one end of the pressure chamber31instead of both. The protruding portions241may be differently shaped on opposite ends of the pressure chamber31. A protruding portion241may be present only on one sidewall rather than both, in some examples.

In an example, the cover portion23and the protruding portion241are formed in part inside the grooves14and thus fill part of each groove14, but the shape is not limited to thereto. For example, on the side surface of the actuator portion22, the cover portion23blocking the air chamber32and the protruding portion241partially blocking the communication port of the pressure chamber31may be formed outside the grooves14, and thus, the diaphragm portion240may be formed outside the groove14and the element wall33.

In an example, an actuator may be provided on an end face of the board21rather than a main surface thereof. In addition, the number of nozzle columns is not limited and may be one column or three or more columns.

In an embodiment, an actuator base11comprises a stacked piezoelectric member made of piezoelectric material on the board21, but embodiments are not limited to thereto. For example, the actuator base11may be formed with only the stacked piezoelectric member without the board. In addition, instead of using the two piezoelectric members, one piezoelectric member may be used.

In some examples, the air chamber32may communicate with one of the first common chamber271and the second common chamber272.

In some examples, the supply side and the discharge side may be reversed or may be configured to be switchable.

In an embodiment, one side of the pressure chamber31is the supply side, and the other side is the discharge side. Although a circulating type inkjet head where the first common chamber fluid flows in from one side of the pressure chamber and flows out from the other side was explained, the present disclosure is not limited to thereto. For example, the inkjet head may be of a non-circulating type. Furthermore, the common chambers on both sides of the pressure chamber31may be a supply side chamber in some examples, and the configuration may be such that the fluid flows into the pressure chamber31from both sides. That is, the configuration may be such that the fluid may flow in from both sides of the pressure chamber31and may flow out from a nozzle28arranged in the center of the pressure chamber31. Even in this case, by providing the diaphragm portions240at the communication ports serving as inlets on both sides of the pressure chamber31, the fluid resistance can be increased, and the ejection efficiency can be improved. In such an example, the configurations of the diaphragm portions240formed at the opposite ends may be different or the same.

In an embodiment, the diaphragm portions240are formed at both ends of the pressure chamber31, but the present disclosure is not limited thereto, and the diaphragm portion240may be formed only on one end. For example, a diaphragm portion240having a higher fluid resistance is formed on one end, but the other end may be configured to have the same cross-sectional area as the inside of the pressure chamber31.

In an embodiment, a side shooter type inkjet head in which both sides of the pressure chamber31communicate with an ink chamber is exemplified, but the present disclosure is not limited to thereto. For example, an end shooter type in which only one end of the pressure chamber31communicates with an ink chamber27may be adopted.

In an embodiment, an example where the protruding portions241are formed on both sidewalls is described, but the present disclosure is not limited to thereto. For example, the protruding portion241may be formed only on one element wall33instead of both.

In The liquid to be ejected is not limited to ink for printing, and a liquid containing conductive particles for forming a wiring pattern on a printed wiring board may be adopted in other examples. In general, the liquid to be ejected is not a limitation.

In an embodiment, the inkjet head is used in a liquid ejection device such as an inkjet printer, but the present disclosure is not limited thereto and embodiments may include, for example, 3D printers, industrial manufacturing machines, and medical applications.

According to at least one embodiment described above, it is possible to provide a liquid ejection head and a method for manufacturing the liquid ejection head capable of ensuring stable ejection characteristics.