Patent Description:
A liquid ejection head of a known type has a plurality of partition walls that are formed at fixed intervals and an actuator formed of piezoelectric ceramics. There are ink flow paths between adj acent partition walls provided on a substrate made of ceramic. A driving electrode is formed on a side surface of each partition wall. In such a liquid ejection head, an end surface of the partition wall is formed as an inclined surface extending outward from the top to the bottom thereof, and a leader wire of the driving electrode is formed on the inclined surface of the partition wall and a portion of the substrate. Such a liquid ejection head is, for example, an inkjet head that ejects ink.

In order to speed up the ejection of the liquid, a liquid ejection head using an independent drive structure with a pressure chamber for ejecting the liquid from a nozzle and an air chamber for not ejecting the liquid is also known. In the liquid ejection head having an independent drive structure, electrodes of pressure chambers are bundled near the center of the substrate to form a common electrode, and electrodes of non-ejecting air chambers are led out towards the driver IC side.

However, in such a liquid ejection head, if the liquid is ejected by simultaneously driving all the nozzles, the drive waveform effectively differs between an end portion and a center portion of the nozzles arranged in a row, and print quality, such as printed dot diameter and linearity deteriorates.

<CIT> discloses a chevron type printhead with alternately arranged pressure and dummy chambers.

To solve the above problems, there is provided a liquid ejection head according to claim <NUM>.

Embodiments provide a liquid ejection head capable of suppressing deterioration of print quality even if a common electrode is used.

In general, according to one embodiment, a liquid ejection head includes a plate having a plurality of nozzles arranged along a first direction. The liquid ejection head further includes a substrate on the plate and has a hole extending along the first direction and through which liquid is supplied for ejection from the nozzles. The liquid ejection head further includes a first actuator on the substrate along the hole. The first actuator has a plurality of pressure chambers, from which the liquid is ejected through the nozzles, and a plurality of air chambers. Each air chamber is disposed between two of the pressure chambers that are adjacent to each other. The liquid ejection head further includes a plurality of individual electrodes formed on the substrate and each is connected to a corresponding one of the pressure chambers. The liquid ejection head further includes a common electrode formed on the substrate and an inner peripheral surface of the hole.

Hereinafter, a liquid ejection head <NUM> and a liquid ejection apparatus (corresponding to liquid ejection device) <NUM> incorporating the liquid ejection head <NUM> will be described with reference to <FIG>.

<FIG> is a perspective view illustrating the liquid ejection head <NUM> according to the first embodiment, and <FIG> is a bottom view of the liquid ejection head <NUM>. <FIG> is a bottom view of the liquid ejection head <NUM> in which a nozzle plate <NUM> is not illustrated. <FIG> is a perspective view of a head body <NUM> of the liquid ejection head <NUM> in which a part of the nozzle plate <NUM> is cut away, and <FIG> is a cross-sectional view of the head body <NUM>. <FIG> is a plan view of a substrate <NUM>, actuators <NUM>, and a plurality of individual electrodes <NUM> and a common electrode <NUM> of the head body <NUM>. <FIG> is a cross-sectional view of the substrate <NUM>, the actuators <NUM>, and the plurality of individual electrodes <NUM> and the common electrode <NUM> of the head body <NUM>. <FIG> is a cross-sectional view of the actuator <NUM> and the plurality of individual electrodes <NUM> and common electrodes <NUM> of the head body <NUM>. <FIG> is a schematic diagram illustrating the liquid ejection apparatus <NUM> having the liquid ejection head <NUM>. For the sake of description in each figure, one or more components are illustrated enlarged, reduced, or omitted as appropriate.

The liquid ejection head <NUM> is a share mode ink jet head provided in the liquid ejection apparatus <NUM> such as an ink jet printing apparatus illustrated in <FIG>, for example. The liquid ejection head <NUM> is provided in a head unit <NUM> including a supply tank <NUM> as a liquid storage unit provided in the liquid ejection apparatus <NUM>.

Ink as a liquid stored in the supply tank <NUM> is supplied to the liquid ejection head <NUM>. The liquid ejection head <NUM> may be a non-circulating type head that does not circulate ink, or may be a circulating type head that circulates ink. In this embodiment, the liquid ejection head <NUM> of the non-circulating type head will be described. The liquid ejection head <NUM> is connected to a temperature control device <NUM> provided in the liquid ejection apparatus <NUM>, and a temperature control liquid (e.g., water) for controlling the temperature of the ink is supplied thereto.

As illustrated in <FIG>, the liquid ejection head <NUM> includes the head body <NUM>, a manifold unit <NUM>, a circuit board <NUM>, and a cover <NUM>. For example, the liquid ejection head <NUM> is a side shooter type, four-row integrated structure head including two sets of head bodies <NUM> each having a pair of actuators <NUM>.

The head body <NUM> ejects a liquid. As illustrated in <FIG>, the head body <NUM> includes the substrate <NUM>, a frame body (corresponding to frame) <NUM>, an actuator <NUM> having a plurality of pressure chambers <NUM> and a plurality of air chambers <NUM>, and the nozzle plate <NUM>.

The head body <NUM> includes a common liquid chamber <NUM> that communicates with the plurality of pressure chambers <NUM> of the actuator <NUM>. The primary side of the plurality of pressure chambers <NUM> is an upstream side of the plurality of pressure chambers <NUM> in a direction in which the liquid flows. The secondary side of the plurality of pressure chambers <NUM> is a downstream side of the plurality of pressure chambers <NUM> in the direction in which the liquid flows.

The head body <NUM> includes a plurality of individual electrodes <NUM> for driving the plurality of pressure chambers <NUM> of the actuator <NUM> and a single or a plurality of common electrodes <NUM> that simultaneously drive the plurality of pressure chambers <NUM> on the substrate <NUM> and the actuator <NUM>.

In this embodiment, the head body <NUM> includes two actuators <NUM>, and the common liquid chamber <NUM> includes one first common liquid chamber <NUM> and two second common liquid chambers <NUM>. For example, the first common liquid chamber <NUM>, communicates with openings on the primary side of the plurality of pressure chambers <NUM> of the actuator <NUM> (i.e., inlets of the pressure chambers <NUM>), and the second common liquid chamber <NUM> communicates with openings on the secondary side (i.e., outlets of the pressure chambers <NUM>) of the plurality of pressure chambers <NUM> of the actuator <NUM>.

The substrate <NUM> is formed in a rectangular plate shape by, for example, a ceramic material. The substrate <NUM> is formed, for example, in a rectangular shape that is long in one direction. A wiring pattern that is a part of the plurality of individual electrodes <NUM> and a wiring pattern that is a part of the single common electrode <NUM> are formed on one surface of the substrate <NUM>. A pair of actuators <NUM> are provided on one surface of the substrate <NUM> so as to be aligned in the lateral direction of the substrate <NUM>. The substrate <NUM> has a single supply port <NUM> and a plurality of discharge ports <NUM>. The supply port <NUM> and the discharge ports <NUM> are through-holes penetrating the substrate <NUM>.

The supply port <NUM> is an inlet for supplying ink to the first common liquid chamber <NUM>. The supply port <NUM> is a through-hole formed in the center of the substrate <NUM> in the lateral direction. The supply port <NUM> extends along the longitudinal direction of the substrate <NUM>. In other words, the supply port <NUM> is, for example, a long hole along the longitudinal direction of the actuator <NUM> and the longitudinal direction of the first common liquid chamber <NUM>. The supply port <NUM> is provided between the pair of actuators <NUM> and opens at a position facing the first common liquid chamber <NUM>.

The discharge port <NUM> is an outlet for discharging ink from the second common liquid chamber <NUM>. A plurality of discharge ports <NUM>, for example, four discharge ports, are provided. Each discharge port <NUM> is located, for example, between the first common liquid chamber <NUM> and each second common liquid chamber <NUM>, and is adjacent to each of both ends in the longitudinal direction of each of the pair of actuators <NUM>. The plurality of discharge ports <NUM> may be provided in the second common liquid chamber <NUM>.

The frame body <NUM> is fixed to one main surface of the substrate <NUM> with an adhesive or the like. The frame body <NUM> surrounds the supply port <NUM>, the plurality of discharge ports <NUM>, and the actuator <NUM> that are provided on the substrate <NUM>.

For example, the frame body <NUM> is formed in a rectangular frame shape to form an opening along the longitudinal direction of the frame body <NUM>. The pair of actuators <NUM>, the supply port <NUM> and four discharge ports <NUM> are disposed in the opening of the frame body <NUM>.

The pair of actuators <NUM> are adhered to a mounting surface of the substrate <NUM>. The pair of actuators <NUM> are provided on the substrate <NUM> to be aligned in two rows with the supply port <NUM> interposed therebetween. The actuator <NUM> is formed in a plate shape that is long in one direction. The actuator <NUM> is disposed in the opening of the frame body <NUM> and adhered to the main surface of the substrate <NUM>.

As illustrated in <FIG>, the actuator <NUM> includes the plurality of pressure chambers <NUM> disposed at equal intervals in the longitudinal direction and the air chambers <NUM> disposed at equal intervals in the longitudinal direction and disposed between adjacent pressure chambers <NUM> on the central side in the longitudinal direction. In other words, the plurality of pressure chambers <NUM> and air chambers <NUM> are alternately disposed in the actuator <NUM> along the longitudinal direction.

The surface of the actuator <NUM> opposite to the substrate <NUM> is adhered to the nozzle plate <NUM>. The actuators <NUM> are disposed to be aligned at equal intervals in the longitudinal direction, and each of the actuators <NUM> is formed with a plurality of grooves along a direction orthogonal to the longitudinal direction. The plurality of grooves form the plurality of pressure chambers <NUM> and the plurality of air chambers <NUM>. In other words, the actuator <NUM> includes a plurality of piezoelectric bodies <NUM> which are drive elements disposed to be aligned at equal intervals in the longitudinal direction and are walls forming the grooves therebetween. The plurality of piezoelectric bodies <NUM> form the plurality of pressure chambers <NUM> and the plurality of air chambers <NUM> between adjacent piezoelectric bodies <NUM>, and a volume of the pressure chamber <NUM> is changed according to a driving voltage applied to the piezoelectric bodies <NUM>.

For example, a width of the actuator <NUM> in the lateral direction gradually increases from the top side toward the substrate <NUM> side. A cross-sectional shape of the actuator <NUM> is formed into a trapezoidal shape. That is, the actuator <NUM> has an inclined surface <NUM> that is inclined to form a side surface portion in the lateral direction. The side surface portion (i.e., the inclined surface <NUM>) is disposed so as to face the first common liquid chamber <NUM> and the second common liquid chamber <NUM>.

As a specific example, the actuator <NUM> is formed of a laminated piezoelectric member obtained by bonding two pieces of piezoelectric materials having a rectangular plate shape long in one direction so as to face each other so that polarization directions of the two pieces of piezoelectric materials are opposite to each other. Here, the piezoelectric material is, for example, lead zirconate titanate (PZT). The actuator <NUM> is adhered to the mounting surface of the substrate <NUM> by, for example, a thermosetting epoxy adhesive. Then, the actuator <NUM> is cut to form the inclined surface <NUM>, for example. In addition, the surfaces of the substrate <NUM> and the actuator <NUM> on which the plurality of individual electrodes <NUM> and common electrodes <NUM> are patterned are polished. In the actuator <NUM>, for example, a plurality of grooves forming the plurality of pressure chambers <NUM> and the plurality of air chambers <NUM> are formed, and the piezoelectric bodies <NUM> (i.e., the drive elements) which are side walls partitioning adjacent grooves are formed.

On the actuator <NUM>, a wiring pattern that is a part of the plurality of individual electrodes <NUM> and a wiring pattern that is a part of the single or the plurality of common electrodes <NUM> are formed.

The pressure chamber <NUM> is deformed during operations such as printing by the liquid ejection head <NUM>, so that ink is ejected from the nozzle <NUM>. The pressure chamber <NUM> has an inlet that opens to the first common liquid chamber <NUM> and an outlet that opens to the second common liquid chamber <NUM>. Ink flows into the pressure chamber <NUM> from the inlet and ink flows out from the outlet of the pressure chamber <NUM>. The pressure chamber <NUM> may be configured such that ink flows in from both openings described as the inlet and the outlet.

As illustrated in <FIG>, the air chamber <NUM> is separated from each of the first common liquid chamber <NUM> and the second common liquid chamber <NUM> by a liquid barrier wall <NUM> formed of a photosensitive resin or the like. As a specific example, the liquid barrier wall <NUM> of the air chamber <NUM> is formed by pouring an ultraviolet curable resin into the groove forming the air chamber <NUM> and then irradiating a necessary portion, for example, both ends, which are the inlet and outlet sides of the groove, with ultraviolet rays using a mask plate or the like. Such a liquid barrier wall <NUM> prevents ink from entering the air chamber <NUM>. The air chamber <NUM> is also sealed by the nozzle plate <NUM>, and the nozzle <NUM> is not disposed therein. Therefore, ink does not flow into the air chamber <NUM>.

The nozzle plate <NUM> is formed in a plate shape. The nozzle plate <NUM> is fixed to the main surface of the frame body <NUM> on the side opposite to the substrate <NUM> with an adhesive or the like. The nozzle plate <NUM> has a plurality of nozzles <NUM> formed at positions facing the plurality of pressure chambers <NUM>. In this embodiment, the nozzle plate <NUM> includes two rows of nozzles <NUM> in which a plurality of nozzles <NUM> are aligned in one direction.

The first common liquid chamber <NUM> is formed between the central sides of the pair of actuators <NUM> except for both ends of the pair of actuators <NUM>, and forms an ink flow path from the supply port <NUM> to the openings (i.e., inlets) on the primary side of the plurality of pressure chambers <NUM> of each actuator <NUM>. The first common liquid chamber <NUM> extends along the longitudinal direction of the actuator <NUM>.

Each of the second common liquid chambers <NUM> is formed between each actuator <NUM> and the frame body <NUM>. Each of the second common liquid chambers <NUM> forms an ink flow path from the openings (i.e., outlets) on the secondary side of the plurality of pressure chambers <NUM> to the discharge port <NUM>. The second common liquid chambers <NUM> extend along the longitudinal direction of the actuator <NUM>.

Through the plurality of individual electrodes <NUM>, a driving voltage is applied to the plurality of piezoelectric bodies <NUM> which are piezoelectric bodies. The plurality of individual electrodes <NUM> individually deform the pressure chambers <NUM>. The individual electrodes <NUM> are formed by a wiring pattern formed on the substrate <NUM> and a wiring pattern formed on the actuator <NUM>.

As a specific example, as illustrated in <FIG>, the plurality of individual electrodes <NUM> are formed on the inner surface of each pressure chamber <NUM>, the inclined surface <NUM> of the actuator <NUM>, and the substrate <NUM>. Specifically, the individual electrode <NUM> is formed on the surface of the piezoelectric body <NUM> forming the pressure chamber <NUM> and a part of a piezoelectric member forming the bottom of the pressure chamber <NUM>. The individual electrode <NUM> is formed on, for example, the inclined surface <NUM> and the polished surface of the substrate <NUM>. The individual electrode <NUM> extends from the inside of the pressure chamber <NUM> to an end portion of the substrate <NUM> in the lateral direction, and an end portion of the individual electrode <NUM> is disposed at a connection portion <NUM> to which the circuit board <NUM> of the substrate <NUM> is connected. The individual electrode <NUM> is provided so as to be in close contact with the bottom of the pressure chamber <NUM> and the surface of the piezoelectric member forming the piezoelectric body <NUM>. The individual electrode <NUM> is formed of, for example, a nickel thin film. The individual electrode <NUM> is not limited to the nickel thin film, and may be formed of, for example, a thin film of gold or copper. The thickness of the individual electrode <NUM> is, for example, <NUM> to <NUM>.

Through the common electrode <NUM>, the same drive voltage is applied to all of the plurality of piezoelectric bodies <NUM>. The common electrode <NUM> deforms the plurality of pressure chambers <NUM> at the same time. The common electrode <NUM> is formed by the wiring pattern formed on the substrate <NUM> and the wiring pattern formed on the actuator <NUM>. The common electrode <NUM> is a wiring pattern provided from the inner peripheral surface of the supply port <NUM> of the substrate <NUM> to the piezoelectric body <NUM> forming the plurality of air chambers <NUM>. The common electrode <NUM> is connected to the circuit board <NUM>.

As a specific example, as illustrated in <FIG>, the common electrode <NUM> is formed on the substrate <NUM> while avoiding the inner surface of each air chamber <NUM>, the inclined surface <NUM> of the actuator <NUM>, and a region where the individual electrodes <NUM> are formed. Specifically, the common electrode <NUM> is formed on the surface of the piezoelectric body <NUM> forming each air chamber <NUM> and a part of the piezoelectric member configuring the bottom of the air chamber <NUM>. The common electrode <NUM> is provided on the inclined surface <NUM> from the inside of each air chamber <NUM> toward the center of the substrate <NUM>, and is formed on the polished surface of the substrate <NUM> between the pair of actuators <NUM> and on the inner peripheral surface of the supply port <NUM>. The common electrode <NUM> extends to the end portion of the substrate <NUM> in the lateral direction, and the end portion of the common electrode <NUM> is disposed at the connection portion <NUM> to which the circuit board <NUM> of the substrate <NUM> is connected.

In other words, the common electrode <NUM> is provided at the center of the substrate <NUM> in the lateral direction between the connection portion <NUM> formed at the end portion of the substrate <NUM> in the lateral direction and the pair of actuators <NUM>. As illustrated in <FIG>, a part of the common electrode <NUM> provided at the center of the substrate <NUM> in the lateral direction is provided on the inner peripheral surface of the supply port <NUM> at the center of the substrate <NUM> in the lateral direction so as to extend in the thickness direction of the substrate <NUM>. A part of the common electrode <NUM> is provided on the surface the piezoelectric member forming each air chamber <NUM> from the center of the substrate <NUM> in the lateral direction.

The common electrode <NUM> is provided so as to be in close contact with the bottom of the air chamber <NUM> and the surface of the piezoelectric member forming the piezoelectric body <NUM>. The common electrode <NUM> is formed of, for example, a nickel thin film. The common electrode <NUM> is not limited to the nickel thin film, and may be formed of, for example, a thin film of gold or copper. The thickness of the common electrode <NUM> is, for example, <NUM> to <NUM>.

For example, the common electrode <NUM> is covered with an adhesive that adheres the frame body <NUM> to the substrate <NUM> on the lower surface of the frame body <NUM>.

As illustrated in <FIG>, <FIG>, and <FIG>, the manifold unit <NUM> includes a manifold <NUM>, a top plate <NUM>, an ink supply pipe <NUM>, an ink discharge pipe <NUM>, and a temperature control water supply pipe <NUM> (which is paired with a temperature control water discharge pipe of the manifold unit <NUM> on the opposite side, for example). The numbers of and positions of the ink supply pipes <NUM>, the ink discharge pipes <NUM>, the temperature control water supply pipes <NUM>, and the temperature control water discharge pipes can be appropriately varied.

The manifold <NUM> is formed in a plate shape or a block shape. As illustrated in <FIG>, the manifold <NUM> includes a supply flow path <NUM>, which communicates with the supply port <NUM> of the substrate <NUM> and forms a liquid supply flow path, a discharge flow path, which communicates with the discharge port <NUM> of the substrate <NUM> and forms a liquid discharge flow path, and a temperature control flow path <NUM> which forms a fluid flow path for temperature control.

One main surface of the manifold <NUM> is fixed to the main surface of the substrate <NUM>. The top plate <NUM> is fixed to a surface of the manifold <NUM> opposite to the main surface to which the substrate <NUM> is fixed. For example, the ink supply pipe <NUM>, the ink discharge pipe <NUM>, the temperature control water supply pipe <NUM>, and the temperature control water discharge pipe are fixed to the manifold <NUM> via the top plate <NUM>.

The supply flow path <NUM> is a flow path formed in the manifold <NUM> by holes and grooves. The supply flow path <NUM> fluidly connects the ink supply pipe <NUM> and the supply port <NUM> of the substrate <NUM>.

The discharge flow path is a flow path formed in the manifold <NUM> by holes and grooves. The discharge flow path fluidly connects the ink discharge pipe <NUM> and the discharge port <NUM> of the substrate <NUM>.

The temperature control flow path <NUM> is a flow path formed in the manifold <NUM> by holes and grooves. The temperature control flow path <NUM> fluidly connects the temperature control water supply pipe <NUM> and the temperature control water discharge pipe.

The ends of the temperature control flow path <NUM> are openings connected to the temperature control water supply pipe <NUM> and the temperature control water discharge pipe provided on one surface of the manifold <NUM>. The temperature control flow path <NUM> is formed for heat exchange with the substrate <NUM> fixed to the manifold <NUM>.

The top plate <NUM> is provided on the surface of the manifold <NUM> opposite to the surface on which the substrate <NUM> is provided. The top plate <NUM> covers the manifold <NUM> to seal the supply flow path <NUM>, the discharge flow path, and the temperature control flow path <NUM>.

The top plate <NUM> has an opening for connecting the pipes <NUM>, <NUM>, and <NUM>, and communicating with the pipes <NUM>, <NUM>, and <NUM> and the flow paths <NUM> and <NUM>.

The ink supply pipe <NUM> is connected to the supply flow path <NUM>. The ink discharge pipe <NUM> is connected to the discharge flow path. The temperature control water supply pipe <NUM> is connected to the primary side of the temperature control flow path <NUM>, and the and the temperature control water discharge pipe is connected to the secondary side.

As illustrated in <FIG>, the circuit board <NUM> includes a plurality of wiring films <NUM> of which one end is connected to the connection portion <NUM> of the substrate <NUM>, a driver IC <NUM> mounted on each of the wiring films <NUM>, and a printed wiring board <NUM> mounted on the other end of the plurality of wiring films <NUM>.

The circuit board <NUM> drives the actuator <NUM> by applying a drive voltage to a wiring pattern of the actuator <NUM> by the driver IC <NUM> to increase or decrease the volume of the pressure chamber <NUM> and eject droplets from the nozzle <NUM>.

Each wiring film <NUM> is connected to the plurality of individual electrodes <NUM> and common electrodes <NUM>. For example, the wiring film <NUM> is an anisotropic conductive film (ACF) fixed to a connection portion of the substrate <NUM> by thermos-compression bonding or the like. A plurality of wiring films <NUM> to be connected are provided for, for example, one head body <NUM>. In this embodiment, two wiring films <NUM> are connected to one actuator <NUM>. The wiring film <NUM> is, for example, a chip on film (COF) on which the driver IC <NUM> is mounted.

The driver IC <NUM> is connected to the plurality of individual electrodes <NUM> and the common electrode <NUM> via the wiring film <NUM>. The driver IC <NUM> may be connected to the plurality of individual electrodes <NUM> and the common electrode <NUM> by other means such as an anisotropic paste (ACP), a non-conductive film (NCF), and a non-conductive paste (NCP) instead of the wiring film <NUM>.

The printed wiring board <NUM> is a printing wiring assembly (PWA) on which various electronic components and connectors are mounted.

The cover <NUM> includes, for example, an outer shell <NUM> that covers the side surfaces of the pair of head bodies <NUM>, the manifold unit <NUM>, and the circuit board <NUM>, and a mask plate <NUM> that covers a part of the pair of head bodies <NUM> on the nozzle plate <NUM> side.

The outer shell <NUM> exposes, for example, the ink supply pipe <NUM>, the ink discharge pipe <NUM>, the temperature control water supply pipe <NUM> and the temperature control water discharge pipe, and the end portion of the circuit board <NUM> of the manifold unit <NUM> to the outside.

The mask plate <NUM> shown in <FIG> covers a portion of the pair of head bodies <NUM> excluding the plurality of nozzles <NUM> and the periphery of the plurality of nozzles <NUM> of the nozzle plate <NUM>.

The liquid ejection head <NUM> configured as described above includes the plurality of individual electrodes <NUM> that can individually apply a drive voltage to each piezoelectric body <NUM>, and the common electrode <NUM> that can apply the drive voltage to all the piezoelectric bodies <NUM> on the head body <NUM>.

Therefore, the liquid ejection head <NUM> can selectively drive the plurality of pressure chambers <NUM> individually or in common. Then, if the pressure chamber <NUM> is driven, the pressure chamber <NUM> undergoes share mode deformation, and the ink supplied into the pressure chamber <NUM> is pressurized. Therefore, the liquid ejection head <NUM> can selectively eject the pressurized ink from the nozzle <NUM> facing the pressure chamber <NUM>.

The common electrode <NUM> is formed not only on the mounting surface of the actuator <NUM> of the substrate <NUM>, the inclined surface <NUM> of the actuator <NUM>, and the inner surface of the air chamber <NUM>, but also on the inner peripheral surface of the supply port <NUM> formed on the substrate <NUM>.

By providing the common electrode <NUM> on the inner peripheral surface of the supply port <NUM> as well, the liquid ejection head <NUM> can have a larger electrode surface area for the common electrode <NUM>, and thus the resistance of the common electrode <NUM> can be reduced. Therefore, even if spacing between rows of the piezoelectric bodies <NUM> of the actuator <NUM> becomes narrower, generation of a difference in ejection performance between the center side and the end portion side in an alignment direction of the nozzles <NUM> can be suppressed.

The ink jet printing apparatus <NUM> including a plurality of liquid ejection heads <NUM> will now be described with reference to <FIG>. The ink jet printing apparatus <NUM> includes a casing <NUM>, a medium supply unit <NUM>, an image forming unit <NUM>, a medium discharge unit <NUM>, a conveyer <NUM>, a maintenance device <NUM>, and a controller <NUM>. The inkjet printing apparatus <NUM> includes a temperature control device that adjusts the temperature of ink supplied to the liquid ejection heads <NUM>.

The ink jet printing apparatus <NUM> is an ink jet printer that performs image forming processing by ejecting ink while conveying, for example, paper P as a recording medium along a conveyance path <NUM> from the medium supply unit <NUM> through the image forming unit <NUM> to the medium discharge unit <NUM>.

The medium supply unit <NUM> includes a plurality of paper feed cassettes <NUM>. The image forming unit <NUM> includes a support portion <NUM> that supports paper, and a plurality of head units <NUM> that are disposed so as to face each other above the support portion <NUM>. The medium discharge unit <NUM> includes a paper discharge tray <NUM>.

The support portion <NUM> includes a conveyance belt <NUM> provided in a loop shape in a predetermined area for which image formation is performed, a support plate <NUM> for supporting the conveyance belt <NUM> from the back side, and a plurality of belt rollers <NUM> provided on the back side of the conveyance belt <NUM>.

The head units <NUM> include the liquid ejection heads <NUM>, a plurality of supply tanks <NUM> as liquid tanks mounted on the liquid ejection heads <NUM>, and pumps <NUM> for supplying ink, connection flow paths <NUM> for connecting the liquid ejection heads <NUM> and the supply tanks <NUM>.

In this embodiment, the liquid ejection heads <NUM> are ink ejection heads of four colors of cyan, magenta, yellow, and black, and the supply tanks <NUM> store ink of those four colors. The supply tank <NUM> is connected to the liquid ejection head <NUM> by the connection flow path <NUM>.

The pump <NUM> is a liquid feed pump configured with, for example, a piezoelectric pump. The pump <NUM> is connected to the controller <NUM> and is driven and controlled by the controller <NUM>.

The connection flow path <NUM> includes a supply flow path connected to the ink supply pipe <NUM> of the liquid ejection head <NUM>. The connection flow path <NUM> includes a recovery flow path connected to the ink discharge pipe <NUM> of the liquid ejection head <NUM>. For example, if the liquid ejection head <NUM> is the non-circulating type liquid ejection head, the recovery flow path is connected to the maintenance device <NUM>, and if the liquid ejection head <NUM> is the circulating type liquid ejection head, the recovery flow path is connected to the supply tank <NUM>.

The conveyer <NUM> conveys paper P along the conveyance path <NUM> from the paper feed cassette <NUM> of the medium supply unit <NUM> to the paper discharge tray <NUM> of the medium discharge unit <NUM> through the image forming unit <NUM>. The conveyer <NUM> includes a plurality of guide plate pairs <NUM> to <NUM> and a plurality of conveyance rollers <NUM> to <NUM> disposed along the conveyance path <NUM>. The conveyer <NUM> supports paper P so as to be relatively movable to the liquid ejection head <NUM>.

The maintenance device <NUM> sucks and recovers ink remaining on the outer surface of the nozzle plate <NUM> during maintenance, for example. If the liquid ejection head <NUM> is a non-circulating type liquid ejection head, the maintenance device <NUM> recovers ink in the head body <NUM> during maintenance. Such a maintenance device <NUM> includes a tray, a tank, or the like for storing the recovered ink.

The controller <NUM> includes a processor such as a CPU (central processing unit) <NUM>, a memory such as a read only memory (ROM) for storing various programs and a random access memory (RAM) for temporarily storing various variable data and image data, and a network interface circuit for receiving data from the outside and outputting data to the outside.

According to the liquid ejection head <NUM> and the liquid ejection apparatus <NUM> configured as described above, by providing the common electrode <NUM> on the inner peripheral surface of the supply port <NUM> which is a long hole, deterioration of print quality can be suppressed even if the common electrode <NUM> is provided.

Embodiments are not limited to the specific configuration described above and various modifications and variations are contemplated.

For example, in the example described above, a pair of head bodies <NUM> are provided in the liquid ejection head <NUM>. Alternatively, the liquid ejection head <NUM> may have one head body <NUM>. Although the above-described head body <NUM> has a pair of actuators <NUM>, the head body <NUM> may have a single actuator <NUM>.

In the example described above, in the head body <NUM>, the common electrode <NUM> is also provided on the inner peripheral surface of the supply port <NUM> to increase the electrode surface area of the common electrode <NUM> in order to reduce the resistance of the common electrode <NUM>, but the head body <NUM> is not limited to this arrangement.

For example, as in a second embodiment illustrated in <FIG>, the head body <NUM> of the liquid ejection head <NUM> may have a configuration in which a groove portion <NUM> is provided on a surface of the substrate <NUM>, which is a region where the common electrode <NUM> is formed, between the actuator <NUM> and supply port <NUM>. For example, the groove portion <NUM> is formed by a plurality of grooves <NUM>. The groove <NUM> extends along the longitudinal direction of the actuator <NUM>, in other words, along the longitudinal direction of the supply port <NUM>. The plurality of grooves <NUM> (e.g., three grooves) are disposed to be aligned in the lateral direction of the actuator <NUM>, for example. The cross-sectional shape of the groove <NUM> in the lateral direction is formed in a V shape. That is, a width of the groove <NUM> in the lateral direction gradually decreases from an upper end side toward the bottom. The common electrode <NUM> is also formed on the inclined surface which is the upper surface of the plurality of grooves <NUM> formed on the substrate <NUM>.

In the head body <NUM> of the liquid ejection head <NUM> according to the second embodiment, the common electrode <NUM> is formed not only on the inner peripheral surface of the supply port <NUM> but also on the upper surfaces of the plurality of grooves <NUM>. Therefore, the head body <NUM> can further reduce the resistance of the common electrode <NUM> by increases in the surface area of the common electrode <NUM>. The head body <NUM> has a configuration in which the surface area of the substrate <NUM> is improved by forming the groove portion <NUM> in a region where the common electrode <NUM> is formed on the substrate <NUM>.

Since the groove <NUM> can be formed on the substrate <NUM> by processing a part of the mounting surface of the substrate <NUM>, the surface area of the region where the common electrode <NUM> is provided can be easily increased. The groove portion <NUM> is not limited to the depicted plurality of V-shaped grooves <NUM> extending in one direction. For example, the groove portion <NUM> may be formed by a plurality of rectangular or conical grooves or recesses. However, in order to form the common electrode <NUM>, the surface of the groove portion <NUM> is desirably an inclined surface with respect to the mounting surface of the substrate <NUM>. The number of grooves <NUM> is not limited to three and can be set as appropriate.

Although the above-described liquid ejection head <NUM> is a non-circulating type head, the liquid discharge head <NUM> may be a circulating type head and have a configuration in which the actuator <NUM> includes a second pressure chamber, which is for purging and of which an opening on the primary side is connected to the second common liquid chamber <NUM>, and a third common liquid chamber is included on the secondary side of the second pressure chamber.

By providing the common electrode also on the inner peripheral surface of the supply port, which is a long hole, deterioration of print quality can be suppressed even when a common electrode is used.

Claim 1:
A liquid ejection head (<NUM>), comprising:
a plate (<NUM>) including a plurality of nozzles arranged along a first direction;
a substrate (<NUM>) on the plate (<NUM>) and including a hole extending along the first direction and through which liquid is supplied for ejection from the plurality of nozzles;
a first actuator (<NUM>) on one surface of the substrate (<NUM>) along the hole in the first direction and including:
a plurality of pressure chambers (<NUM>) through which the liquid is supplied from the hole to the nozzles, and
a plurality of air chambers (<NUM>), each air chamber disposed between two of the pressure chambers (<NUM>) that are adjacent to each other;
a plurality of individual electrodes (<NUM>), each individual electrode on the one surface of the substrate (<NUM>) and connected to a corresponding one of the pressure chambers (<NUM>);
a common electrode (<NUM>) on the one surface of the substrate (<NUM>) and an inner peripheral surface of the hole, and
a second actuator (<NUM>) on the substrate (<NUM>) along the hole in the first direction, wherein
the hole is between the first and second actuators (<NUM>).