Patent Description:
A piezoelectric actuator using a piezoelectric material such as "PZT" (lead zirconate titanate) can be used as driving source of a liquid ejecting apparatus such as an inkjet printer head. In an inkjet printer head, a configuration in which many grooves are formed at a fine pitch in a body of piezoelectric material to provide divided columnar elements to serve as nozzle actuators is known. Wirings are connected to drive such actuators. However, if the columnar elements of the piezoelectric material are thin or fragile, it can be difficult to mount such piezoelectric actuators with adhesive or the like since when pressure is applied damage may occur. Therefore, it is considered that solder might be used for the mounting. However, when the piezoelectric actuator is heated during a mounting process, the performance of the piezoelectric material may deteriorate.

The document <CIT> (D1) discloses a conventional liquid ejecting head.

To this end, there is provided a liquid ejecting head and a liquid ejecting apparatus according to appended claims.

In general, according to one embodiment, a liquid ejecting head includes a piezoelectric member, electrodes, and a wiring substrate. The piezoelectric member has a plurality of piezoelectric elements formed of a piezoelectric material. The electrodes are formed on the piezoelectric member. The wiring substrate is joined to the electrodes by solder. The solder has a melting point of less than or equal to <NUM>/<NUM> of the Curie point of the piezoelectric material.

Hereinafter, an inkjet head <NUM> (which is a liquid ejecting head) and an inkjet recording apparatus <NUM> (which is a liquid ejecting apparatus) according to certain example embodiments will be described with reference to <FIG>. <FIG> and <FIG> are cross-sectional views illustrating schematic configurations of the inkjet head <NUM>. <FIG> is a cross-sectional view illustrating a configuration of a part of an FPC. <FIG> is table of correspondence between types of solder and their melting points. <FIG> is a diagram illustrating aspects of a method for manufacturing the inkjet head <NUM>. <FIG> is a diagram illustrating a schematic configuration of the inkjet recording apparatus <NUM>. The aspects and/or elements depicted in the drawings are not necessarily to scale and relative dimensions and the like may be varied from actuality and from drawing to drawing for purposes of explanation.

As illustrated in <FIG> and <FIG>, the inkjet head <NUM> includes a base <NUM> (substrate), actuator units <NUM>, a flow passage member <NUM>, a nozzle plate <NUM> including a plurality of nozzles <NUM>, a frame unit <NUM> serving as a structure unit, and a driving circuit <NUM>. For example, the inkjet head <NUM> includes two actuator units <NUM>, two nozzle rows in which the nozzles <NUM> are arranged along a row direction (the X direction), two pressure chamber rows in which pressure chambers <NUM> are arranged along the row direction, and two element rows in which piezoelectric elements <NUM> and <NUM> are arranged along the row direction. In the present embodiment, a stacking direction of piezoelectric layers <NUM>, a vibration direction of the piezoelectric elements <NUM> and <NUM>, and a vibration direction of a vibration plate <NUM> are oriented in the Z direction.

The actuator units <NUM> are joined to one side of the base <NUM>. The actuator units <NUM> are provided, for example, on the base <NUM>. For example, two actuator units <NUM> are disposed side by side in the Y direction. In <FIG> and <FIG>, only one actuator unit <NUM> is specifically depicted, but each actuator unit <NUM> has a similar structure.

The actuator unit <NUM> is formed from a piezoelectric material and includes a plurality of driving piezoelectric elements <NUM> and a plurality of non-driving piezoelectric elements <NUM> alternately arranged in the row direction, and a connection portion <NUM> connecting the plurality of piezoelectric elements <NUM> and <NUM> on the base <NUM> side.

In the actuator unit <NUM>, the plurality of driving piezoelectric elements <NUM> and the plurality of non-driving piezoelectric elements <NUM> are arranged at a constant interval.

In this example, the driving piezoelectric elements <NUM> and the non-driving piezoelectric elements <NUM> are each configured in a rectangular parallelepiped columnar shape and have the same external shape. The actuator unit <NUM> is divided into a plurality of portions by a plurality of grooves <NUM> with the same width. The plurality of driving piezoelectric elements <NUM> and the plurality of non-driving piezoelectric elements <NUM> are thus all arranged at the same pitch by the grooves <NUM> therebetween.

For example, by setting the depth of the groove <NUM> to be less than the entire height of a stacked piezoelectric member <NUM> in the Z direction, the connection portion <NUM> can be formed integrally, and it is possible to form a shape in which one side is divided into a plurality of portions but the other side remains connected.

For example, the plurality of driving piezoelectric elements <NUM> and the plurality of non-driving piezoelectric elements <NUM> are each formed in a rectangular shape in which a transverse direction is oriented in the row direction of the element row and a longitudinal direction is oriented in an extension direction orthogonal to the row direction and the Z direction in a plan view when viewed in the Z direction.

The driving piezoelectric elements <NUM> are arranged at positions facing the plurality of pressure chambers <NUM> formed in the flow passage member <NUM> in the Z direction. For example, central positions of the driving piezoelectric elements <NUM> in the row direction and the extension direction and central positions of the pressure chambers <NUM> in the row direction and the extension direction are arranged side by side in the Z direction.

The non-driving piezoelectric elements <NUM> are arranged at positions facing a plurality of partition walls <NUM> formed in the flow passage member <NUM> in the Z direction. For example, the central positions of the driving piezoelectric elements <NUM> in the row direction and the extension direction and central positions of the partition walls <NUM> in the row direction and the extension direction are arranged side by side in the Z direction.

For example, the actuator unit <NUM>, may be formed by forming the grooves <NUM> by dicing of a stacked piezoelectric material (e.g., stacked piezoelectric member <NUM>, see also <FIG>) may mounted/joined to stacked piezoelectric material before the dicing process. Electrodes or the like are provided for the plurality of columnar elements thus formed, and the plurality of driving piezoelectric elements <NUM> and the plurality of non-driving piezoelectric elements <NUM> alternately disposed are formed. The plurality of driving piezoelectric elements <NUM> and the plurality of non-driving piezoelectric elements <NUM> are disposed alternately in parallel with the grooves <NUM> interposed therebetween in the row direction.

For example, the stacked piezoelectric member <NUM> used for forming the actuator unit <NUM> is formed by stacking and baking (heating) sheet-shaped piezoelectric materials.

A piezoelectric material forming the driving piezoelectric element <NUM> and the non-driving piezoelectric element <NUM> is, for example, the stacked piezoelectric member <NUM> depicted in <FIG>. The driving piezoelectric element <NUM> and the non-driving driving piezoelectric element <NUM> each include the stacked piezoelectric layers <NUM> and internal electrodes <NUM> and <NUM> formed in a main surface of each piezoelectric layer <NUM>. For example, the driving piezoelectric element <NUM> and the non-driving piezoelectric element <NUM> have the same stacked structure. The driving piezoelectric element <NUM> and the non-driving piezoelectric element <NUM> include external electrodes <NUM> and <NUM> formed on surfaces thereof.

The piezoelectric layer <NUM> is formed, for example, as a thin sheet of a piezoelectric ceramic material such as a lead zirconate titanate (PZT)-based or lead-free sodium potassium niobate (KNN)-based material. The piezoelectric layers <NUM> are stacked and adhered (laminated) to each other. For example, the thickness direction and the stacking direction of the piezoelectric layers <NUM> in the present embodiment are disposed along the vibration direction (the Z direction).

The internal electrodes <NUM> and <NUM> are conductive films formed of a bakeable conductive material such as silver palladium in a predetermined shape. The internal electrodes <NUM> and <NUM> are formed in a predetermined region on the main surface of a piezoelectric layer <NUM>. The internal electrodes <NUM> and <NUM> have different polarities from each other. For example, an internal electrode <NUM> is formed in a region at one end of the piezoelectric layer <NUM> extending in the Y direction but does not reach the other (opposite) end of the piezoelectric layer <NUM>. An internal electrode <NUM> is formed at a region at the opposite end of the piezoelectric layer <NUM> extending in the Y direction but does not reach the opposite end of the piezoelectric layer (the end where the internal electrode <NUM> begins). The internal electrodes <NUM> and <NUM> are connected to the external electrodes <NUM> and <NUM> formed on the lateral surfaces of the piezoelectric elements <NUM> and <NUM>, respectively.

The stacked piezoelectric member <NUM> configuring the driving piezoelectric element <NUM> and the non-driving piezoelectric element <NUM> further includes a dummy layer <NUM> on at least one on the base <NUM> side and a nozzle plate <NUM> side of the stack. The dummy layer <NUM> is formed of, for example, the same material as that of the piezoelectric layer <NUM> but is not deformed in operation since an electrode is formed on only one side and thus an electric field is not applied thereto (or thereacross). For example, the dummy layer <NUM> does not function as a piezoelectric body, but serves as a base for fixing the actuator unit <NUM> to the base <NUM>, or serves as a polishing margin that might be utilized when the actuator unit <NUM> is polished for accuracy during or after assembly.

The external electrodes <NUM> and <NUM> are formed on the surfaces of the driving piezoelectric elements <NUM> and the non-driving piezoelectric elements <NUM>, and configured to gather (lead out) ends of the internal electrodes <NUM> and <NUM>. For example, the external electrodes <NUM> and <NUM> are formed on opposite end surfaces in the extension direction of the piezoelectric layer <NUM>, respectively. The external electrodes <NUM> and <NUM> can be formed as a film of nickel (Ni), chromium (Cr), gold (Au), or the like using a known method such as a plating or sputtering method. The external electrodes <NUM> and <NUM> have different polarities. The external electrodes <NUM> and <NUM> are disposed on different lateral surfaces of the driving piezoelectric elements <NUM> and the non-driving piezoelectric elements <NUM>.

In the present embodiment, the external electrode <NUM> serves as an individual electrode and the external electrode <NUM> serves as a common electrode. The external electrodes <NUM> (serving as the individual electrodes for the plurality of driving piezoelectric elements <NUM> and the plurality of non-driving piezoelectric elements <NUM>) are formed with a junction portion <NUM> which is on one lateral surface of the stacked piezoelectric member <NUM>, and the electrode layers are divided by the grooves <NUM> so that the external electrodes <NUM> can be independently addressed/operated. For the external electrodes <NUM> (serving as the common electrode), the electrode layers are connected to each other on the lateral surface of the stacked piezoelectric member <NUM> so that the external electrodes <NUM> are each connected to one another (for example, external electrodes <NUM> are ground terminals or the like).

Each external electrode <NUM> is connected to the driving circuit <NUM> via the FPC <NUM> (serving as a flexible substrate which is an example of a wiring substrate) at the junction <NUM> on the lateral surface of piezoelectric member <NUM>). For example, each individual external electrode <NUM> is connected to a control unit <NUM> (serving as a driving unit) via a driving IC <NUM> of the driving circuit <NUM> by the FPC <NUM> and is configured so that driving can be independently controlled by a control circuit <NUM>. In other examples, the disposition of the common and individual electrodes may be reversed. The external electrodes <NUM> may be routed at the junction <NUM> on the external electrode <NUM> side and may be connected to the driving circuit <NUM> via the FPC <NUM>.

The dummy layer <NUM> is formed of the same material as that of the piezoelectric layer <NUM>. The dummy layer <NUM> is not deformed since an electrode is formed on only one side and an electric field is not applied. That is, the dummy layer <NUM> does not function as a piezoelectric actuator, but serves as the base for fixing or as polishing margin.

A removal portion <NUM> that has an inclined surface obliquely inclined to the stacking direction is formed in an end on the base <NUM> side of a lateral surface on the individual electrode side of the stacked piezoelectric member <NUM> configuring the piezoelectric elements <NUM> and <NUM>. The removal portion <NUM> is a chamfered portion formed by cutting the corner into a tapered shape so that a region of the piezoelectric element <NUM> at the end of the base <NUM> side is recessed in a direction away from the FPC <NUM>.

The removal portion <NUM> extends in the stacking direction and the arrangement direction of the pressure chambers <NUM>. For example, the removal portion <NUM> is provided in the dummy layer <NUM>. That is, in the piezoelectric element <NUM>, a portion which does not function as the piezoelectric body and is not deformed can be partially cut and formed in an inclined surface shape to provide the removal portion <NUM>. In some examples, the removal portion <NUM> may be located in the piezoelectric layer <NUM>. In this case, the removal portion <NUM> is formed at positions avoiding the internal electrodes <NUM> and <NUM> and the external electrodes <NUM> and <NUM>.

The vibration direction of each of the piezoelectric elements <NUM> and <NUM> is oriented in the stacking direction and is displaced in a d33 direction by applying an electric field.

For example, each of the piezoelectric elements <NUM> and <NUM> comprises <NUM> to <NUM> layers, a thickness of each such stacked layer is set to <NUM> to <NUM>, and the layer thickness multiplied by the number of stacked layers is less than <NUM>,<NUM>.

The driving piezoelectric elements <NUM> vibrate when a voltage is applied to the internal electrodes <NUM> and <NUM> via the external electrodes <NUM> and <NUM>. In the present embodiment, the driving piezoelectric elements <NUM> vertically vibrate in the stacking direction of the piezoelectric layers <NUM>. The vertical vibration mentioned herein is, for example, "vibration in a thickness direction defined by a piezoelectric constant d33". The driving piezoelectric elements <NUM> displace the vibration plate <NUM> to deform the pressure chambers <NUM>.

The flow passage member <NUM> includes the vibration plate <NUM> disposed to face the actuator unit <NUM> in a deformation direction and a flow passage substrate <NUM> stacked on the vibration plate <NUM>.

The vibration plate <NUM> is provided between the flow passage substrate <NUM> and the actuator units <NUM> in the vibration direction. The vibration plate <NUM> forms the flow passage member <NUM> together with the flow passage substrate <NUM>.

The vibration plate <NUM> is joined to one side of the piezoelectric layers <NUM> of the plurality of piezoelectric elements <NUM> and <NUM> in the vibration direction, that is, the surface of the nozzle plate <NUM> side. The vibration plate <NUM> is configured to be deformable (flexible), for example. The vibration plate <NUM> is joined to the driving piezoelectric elements <NUM> and the non-driving piezoelectric elements <NUM> of the actuator units <NUM> and the frame unit <NUM>. For example, the vibration plate <NUM> includes a vibration region <NUM> facing the piezoelectric elements <NUM> and <NUM> and a support region <NUM> facing the frame unit <NUM>.

The vibration region <NUM> has, for example, a plate shape disposed so that the thickness direction is along the vibration direction of the piezoelectric layers <NUM>. The vibration plate <NUM> extends in a surface direction oriented in the arrangement direction of the plurality of driving piezoelectric elements <NUM> and the plurality of non-driving piezoelectric elements <NUM>. The vibration plate <NUM> is, for example, a metal plate. The vibration plate <NUM> has a plurality of vibration portions which face a pressure chamber <NUM> and can be displaced individually. The vibration plate <NUM> can be formed by integrally connecting the plurality of vibration portions.

For example, the vibration plate <NUM> is formed of nickel or a stainless steel (SUS) plate and a thickness dimension in the vibration direction is about <NUM> to <NUM>. In the vibration region <NUM>, creases or steps may be formed in portions adjacent to the vibration portions or between the vibration portions adjacent to each other so that the plurality of vibration portions can be more easily displaced. The vibration region <NUM> is deformed when portions disposed to face the driving piezoelectric elements <NUM> are displaced through expansion and compression of the driving piezoelectric elements <NUM>. For example, the vibration plate <NUM> is formed by an electroforming method or the like since a very thin and complicated shape may be necessary. The vibration plate <NUM> is joined to the upper end surfaces of the actuator units <NUM> by an adhesive or the like.

The support region <NUM> is a plate-shaped member disposed between the frame unit <NUM> and the flow passage substrate <NUM>. The support region <NUM> includes a communication portion <NUM> that has a through-hole communicating with a common chamber <NUM>.

For example, the communication portion <NUM> may include a filter member that has many pores through which a liquid can pass as the through-hole.

The flow passage substrate <NUM> is disposed between the nozzle plate <NUM> and the vibration plate <NUM>. The flow passage substrate <NUM> is joined to one side of the vibration plate <NUM>.

The flow passage substrate <NUM> includes a peripheral wall <NUM> joined to the outer edge of the vibration plate <NUM>, the partition walls <NUM> partitioning ink passages <NUM>, and a guide wall <NUM> that forms a guide flow passage <NUM>. In the flow passage substrate <NUM>, the ink passage <NUM> including the pressure chambers <NUM> is partitioned by the partition walls <NUM>.

Inside the flow passage substrate <NUM>, the plurality of pressure chambers <NUM> are partitioned by the partition walls <NUM>. That is, both sides of the pressure chambers <NUM> are formed by partition walls <NUM>. The pressure chambers <NUM> each communicate with one of the nozzles <NUM> formed in the nozzle plate <NUM>. In the pressure chambers <NUM>, the side opposite to the nozzle plate <NUM> is closed by the vibration plate <NUM>.

The plurality of pressure chambers <NUM> are spaces formed on one side of the vibration region <NUM> of the vibration plate <NUM> and communicate with the common chamber <NUM> via the guide flow passage <NUM> and the communication portion <NUM>. The plurality of pressure chambers <NUM> communicate with the nozzles <NUM> formed in the nozzle plate <NUM>. In the pressure chambers <NUM>, the side opposite to the nozzle plate <NUM> is closed by the vibration plate <NUM>.

The plurality of pressure chambers <NUM> hold a liquid supplied from the common chamber <NUM> (via the guide flow passage <NUM>) and are deformed by vibration of the vibration plate <NUM> to eject liquid from the nozzles <NUM>.

The partition walls <NUM> are arranged in parallel and partition the plurality of guide flow passages <NUM>, and configure the lateral sides of both the guide flow passages <NUM> and the pressure chambers <NUM>. The partition walls <NUM> are disposed to face the non-driving piezoelectric elements <NUM> via the vibration plate <NUM> and are supported by the non-driving piezoelectric elements <NUM>. The plurality of partition walls <NUM> are provided at the same pitch as a pitch at which the plurality of pressure chambers <NUM> are arranged.

The nozzle plate <NUM> is formed in a rectangular plate shape with a thickness of about <NUM> to <NUM> and formed of, for example, a metal such as SUS-Ni or a resin such as a polyimide. The nozzle plate <NUM> is disposed on one side of the flow passage substrate <NUM> to cover an opening on one side of the pressure chambers <NUM>.

The plurality of nozzles <NUM> are arranged to form nozzle rows. For example, the nozzles <NUM> are provided in two rows and the nozzles <NUM> are provided at positions corresponding to the plurality of pressure chambers <NUM> arranged in two rows. In the present embodiment, the nozzles <NUM> are provided at positions near the ends of the pressure chambers <NUM> in the extension direction.

The frame unit <NUM> is a structure joined to the vibration plate <NUM> together with the piezoelectric elements <NUM> and <NUM>. The frame unit <NUM> is provided on the side of the piezoelectric elements <NUM> and <NUM> and the vibration plate <NUM> opposite to the flow passage substrate <NUM> and is, for example, disposed to be adjacent to the actuator unit <NUM> in the present embodiment. The frame unit <NUM> configures the outline (outer perimeter) of the inkjet head <NUM>. The frame unit <NUM> may form a portion of a liquid flow passage inside. In the present embodiment, the frame unit <NUM> is joined to the vibration plate <NUM> and the common chamber <NUM> is formed between the frame unit <NUM> and the vibration plate <NUM>.

The common chamber <NUM> is formed inside the frame unit <NUM> and communicates with the pressure chambers <NUM> via the guide flow passages <NUM> and the communication portions <NUM> provided in the vibration plate <NUM>.

The driving circuit <NUM> has a flexible printed circuit (FPC) <NUM> of which one end is connected to the external electrodes <NUM> and <NUM>. The driving IC <NUM> is mounted on the FPC <NUM>, and a printed wiring substrate <NUM> mounted on the other end of the FPC <NUM> from the external electrodes <NUM> and <NUM>.

The driving circuit <NUM> drives the driving piezoelectric elements <NUM> by applying a driving voltage to the external electrodes <NUM> and <NUM> by the driving IC <NUM> and ejects liquid droplets from the nozzles <NUM> by increasing and decreasing volumes of the pressure chambers <NUM>.

The FPC <NUM> is connected to the plurality of external electrodes <NUM> and <NUM>. As the FPC <NUM>, a chip-on film (COF) on which the driving IC <NUM> is mounted as an electronic component can be used.

The FPC <NUM> is connected to the junction <NUM> on the lateral surface of the stacked piezoelectric member <NUM>. As illustrated in <FIG>, the FPC <NUM> includes a base layer <NUM>, an electrode layer <NUM>, a solder layer <NUM>, an adhesion layer <NUM>, and an insulation cover layer <NUM>.

The base layer <NUM> can be a polyimide sheet or the like. The electrode layer <NUM> is formed of a conductive material such as a metal and is formed in a predetermined pattern on the surface of the base layer <NUM>. The electrode layer <NUM> is, for example, a copper foil or the like. On a surface of the electrode layer <NUM>, the solder layer <NUM> is formed over a junction region that is to be joined to the piezoelectric elements <NUM>. The solder layer <NUM> is formed by solder plating to a thickness of about <NUM> to <NUM>. In outside the junction region on the surface of the electrode layer <NUM>, the insulation cover layer <NUM> can be formed with the adhesion layer <NUM> interposed therebetween.

The FPC <NUM> is electrically and mechanically connected to the external electrodes <NUM> by causing the junction region (where the solder layer <NUM> is formed) to face the junction <NUM>, appropriately aligning the junction region with the junction <NUM>, heating the junction region, and melting the solder of the solder layer <NUM>. In some examples, the FPC <NUM> may be connected to some of the external electrodes <NUM> which may be routed to the junction <NUM>. The heating may be performed by using a general heating tool or emitting an infrared laser or the like passing through the base layer <NUM> of the FPC <NUM>. The joining may be performed by solder by pressurization of, for example, about <NUM> although the pressurization may be different depending on conditions such as warpage tolerance of components.

For the solder layer <NUM>, a type of lead-free solder with a melting point equal to or less than <NUM> / <NUM> of the Curie point of the piezoelectric material used in the actuator unit <NUM> while still being equal to or greater the highest temperature at the junction <NUM> during operations (highest attainment temperature) can be selected from among various types of solder, such as those shown in <FIG>. Here, the highest attainment temperature at the junction <NUM> is the highest temperature at the junction <NUM> that may be assumed (or estimated) to occur during the driving of the inkjet head <NUM>. For example, the highest attainment temperature is a predetermined value calculated based on an expected heat generation temperature of the driving IC <NUM>. A temperature of a mounted portion becomes higher due to the heat generated by the piezoelectric body and thermal insulation of heat of the driving IC <NUM> via the FPC <NUM>. For example, the temperature of the mounted portion in printing at a duty ratio of <NUM>% may be assumed to result in the highest attainment temperature. Alternatively, a highest expected operating temperature of an element such as the driving IC <NUM> or the piezoelectric member <NUM> may be set as the highest attainment temperature for the junction <NUM>. It may be preferable in most instances to use solder with a melting point of at least <NUM>. The duty ratio in this context is the ratio of the period of a driving signal (pulse signal) to the maximum pulse width of the driving signal and is expressed in the following expression: <MAT>.

For example, as the solder of the solder layer <NUM>, tin-bismuth-indium (Sn-Bi-In) alloy with a melting point in the range of <NUM> to <NUM>, Sn-52In alloy with a melting point of <NUM>, Sn-58Bi alloy with of melting point of <NUM>, indium (In) with a melting point of <NUM>, or the like may be used. For example, a Curie point of a piezoelectric material is about <NUM>, and Sn-In-based or Sn-Bi-based solder can thus be appropriate for an injection head incorporating the stacked piezoelectric member <NUM> in which the highest attainment temperature for the junction <NUM> is considered to be <NUM>.

In the FPC <NUM>, the thickness outside the junction region can be greater than the thickness of the junction region due to the difference between the thickness of the solder layer <NUM> and a sum of the thicknesses of the insulation cover layer <NUM> and the adhesion layer <NUM>, and thus a step is formed on the surface of the FPC <NUM>. The solder layer <NUM> is disposed to face the junction <NUM>, and the insulation cover layer <NUM> is disposed to face the removal portion <NUM>.

The driving IC <NUM> is connected to the external electrodes <NUM> and <NUM> via the FPC <NUM>. The driving IC <NUM> is an electronic component used for ejection control.

The driving IC <NUM> generates a control signal and a driving signal for operating each driving piezoelectric element <NUM>. The driving IC <NUM> generates a control signal for control such as an ink ejection timing or selection of the driving piezoelectric elements <NUM> ejecting ink in accordance with an image signal input from the control unit <NUM> of the inkjet recording apparatus <NUM> on which the inkjet head <NUM> is mounted. The driving IC <NUM> generates a voltage to be applied to the driving piezoelectric elements <NUM>, that is, a driving signal, in accordance with the control signal from the control unit <NUM>. If the driving IC <NUM> applies the driving signal to the driving piezoelectric elements <NUM>, the driving piezoelectric elements <NUM> are driven to displace the vibration plate <NUM> and change the volumes of the pressure chambers <NUM>. Accordingly, the ink filled in the pressure chambers <NUM> causes pressure vibration. Because of the pressure vibration, the ink is ejected from the nozzles <NUM> communicating with the pressure chambers <NUM>. The inkjet head <NUM> may be configured to realize grayscale expression by changing the number or volume of ink droplets to be landed to one pixel. The inkjet head <NUM> may be configured so that the number of ink droplets to be landed to one pixel can be changed by changing the number of times the ink is ejected. In this way, the driving IC <NUM> is an example of an application unit that applies the driving signal to the driving piezoelectric elements <NUM>.

For example, the driving IC <NUM> includes a data buffer, a decoder, and a driver. The data buffer stores time-series printing data for each driving piezoelectric element <NUM>. The decoder controls the driver based on the printing data stored in the data buffer for each driving piezoelectric element <NUM>. The driver outputs the driving signal for operating each driving piezoelectric element <NUM> under the control of the decoder. The driving signal is, for example, a voltage to be applied to each driving piezoelectric element <NUM>.

The printed wiring substrate <NUM> can also be referred to as a printing wiring assembly (PWA) on which various electronic components or connectors may be mounted and includes a head control circuit <NUM>. The printed wiring substrate <NUM> is connected to the control unit <NUM> of the inkjet recording apparatus <NUM>.

In the inkjet head <NUM>, ink flow passages including the plurality of pressure chambers <NUM> communicating with the nozzles <NUM>, a plurality of guide flow passages <NUM> respectively communicating the plurality of pressure chambers <NUM>, and the common chamber <NUM> communicating with the plurality of guide flow passages <NUM> are formed by the nozzle plate <NUM>, the frame unit <NUM>, the flow passage substrate <NUM>, and the vibration plate <NUM>. For example, the common chamber <NUM> connects to a cartridge so that ink can be supplied to each pressure chamber <NUM> via the common chamber <NUM>. All the driving piezoelectric elements <NUM> are connected so that a voltage can be applied by wirings. In the inkjet head <NUM>, the driving piezoelectric elements <NUM> of the driving target vibrate in, for example, the stacking direction, that is, the thickness direction of each piezoelectric layer <NUM>, for example, if the control unit <NUM> of the inkjet recording apparatus <NUM> applies the driving voltage to the electrodes <NUM> and <NUM> by the driving IC <NUM>. That is, the driving piezoelectric elements <NUM> vertically vibrate.

Specifically, the control unit <NUM> applies the driving voltage to the internal electrodes <NUM> and <NUM> of the driving piezoelectric elements <NUM> to selectively drive particular driving piezoelectric elements <NUM> as necessary. Then, by deforming the vibration plate <NUM> in combination of deformation in a tensile direction and deformation in a compression direction by the driving piezoelectric elements <NUM> of the driving target and changing the volumes of the pressure chambers <NUM>, a liquid is guided from the common chamber <NUM> to be ejected from the nozzles <NUM>.

An example of a method for manufacturing the inkjet head <NUM> according to the present embodiment will be described. First, the internal electrodes <NUM> and <NUM> are formed of a piezoelectric material formed in a sheet shape by a printing process (e.g., a lithographic method). The plurality of piezoelectric layers <NUM> including the internal electrodes <NUM> and <NUM> are stacked to form the stacked piezoelectric member <NUM> by a baking process and a polarization process.

Then, the stacked piezoelectric member <NUM> in which the internal electrodes <NUM> and <NUM> are formed in advance is disposed on the base <NUM>. For example, if two actuator units <NUM> are to be formed, the stacked piezoelectric member <NUM> may be divided into two by a grooving process after the integrally configured stacked piezoelectric member <NUM> is joined to the base <NUM>, or alternatively two stacked piezoelectric members <NUM> configuring the two actuator units <NUM> may be prepared separately.

Subsequently, the external electrodes <NUM> and <NUM> are formed on end surfaces of the stacked piezoelectric member <NUM> by a printing process. Then, the removal portion <NUM> is formed on the end at which the external electrodes <NUM> are disposed by a dicing process. The electrode layer of the portion on the base <NUM> side of the external electrode <NUM> is removed by forming the removal portion <NUM>. Further, by forming the plurality of grooves <NUM> with a depth reaching portions in which electrodes are removed by the removal portion <NUM>, one side of the stacked piezoelectric member <NUM> in the Z direction is divided into a plurality of pieces. In this way, the stacked piezoelectric member <NUM> of which one end is divided into a plurality of portions and the other end is still connected is formed. At this time, by forming the plurality of grooves <NUM> at a predetermined pitch and dividing the stacked piezoelectric member <NUM> into the plurality of portions, a plurality of columnar elements serving as the plurality of piezoelectric elements <NUM> and <NUM> arranged at the same pitch can be formed. In this way, the plurality of driving piezoelectric elements <NUM> and the plurality of non-driving piezoelectric elements <NUM> arranged at the same pitch are formed.

Here, by forming the grooves <NUM> at the depth reaching the removal portion <NUM> in which the electrode layers are removed, the electrode layers on the side on which the removal portion <NUM> is formed serve as independently individual electrodes separated from each other. On the other hand, the electrode layers on the lateral surface in which the removal portion <NUM> is not formed configure the common electrodes in which the electrode layers continue in a region closer to the base <NUM> than the bottoms of the grooves. Further, adhesion to the base <NUM> is performed with an adhesive or the like by performing a polarization process of the piezoelectric elements <NUM>.

In the junction <NUM>, the FPC <NUM> is connected to the external electrodes <NUM> and <NUM>, for example, by solder mounting or the like. Further, the printed wiring substrate <NUM> including the head control circuit <NUM> is connected to the FPC <NUM>.

The vibration plate <NUM>, the flow passage substrate <NUM>, and the nozzle plate <NUM> are stacked and positioned on the actuator units <NUM> with joining materials interposed therebetween, the frame units <NUM> are disposed on the outer circumference of the actuator units <NUM>, the plurality of members are joined to complete the inkjet head <NUM>.

Hereinafter, an example of the inkjet recording apparatus <NUM> including the inkjet head <NUM> will be described with reference to <FIG>. The inkjet recording apparatus <NUM> includes a casing <NUM>, a medium supply unit <NUM>, an image forming unit <NUM>, a medium discharging unit <NUM>, a conveyance device <NUM>, and a control unit <NUM>.

The inkjet recording apparatus <NUM> is a liquid ejecting apparatus that performs an image forming process on a sheet P by ejecting a liquid such as ink while conveying the sheet P serving as a printing medium from the medium supply unit <NUM> through the image forming unit <NUM> along a predetermined conveyance path R reaching the medium discharging unit <NUM>.

The casing <NUM> forms the outside of the inkjet recording apparatus <NUM>. A discharging port through which the sheet P is discharged outside is included at a predetermined portion of the casing <NUM>.

The medium supply unit <NUM> includes a plurality of feeding cassettes and is configured so that the plurality of sheets P with various sizes are stacked and retained.

The medium discharging unit <NUM> includes a discharging tray configured to retain the sheet P discharged from the discharging port.

The image forming unit <NUM> includes a support unit <NUM> that supports the sheet P and includes a plurality of head units <NUM> disposed to face the upper side of the support unit <NUM>.

The support unit <NUM> includes a conveyance belt <NUM> that is provided in a loop shape in a predetermined region where image forming is performed, a support plate <NUM> that supports the conveyance belt <NUM> from a rear side, and a plurality of belt rollers <NUM> provided on the rear side of the conveyance belt <NUM>.

The support unit <NUM> conveys the sheet P downstream by supporting the sheet P on a retainment surface which is the upper surface of the conveyance belt <NUM> and feeding the conveyance belt <NUM> at a predetermined timing with rotation of the belt rollers <NUM>.

The head unit <NUM> includes a plurality of inkjet heads <NUM> (e.g., four-color heads), ink tanks <NUM> for each of the inkjet heads <NUM>, connection flow passages <NUM> connecting the inkjet heads <NUM> to the respective ink tanks <NUM>, and supply pumps <NUM>.

In the present embodiment, the inkjet heads <NUM> of four colors, cyan, magenta, yellow, and black and an ink tank <NUM> for each are included. The ink tanks <NUM> are connected to the respective inkjet heads <NUM> by a connection flow passage <NUM>.

A negative pressure control device such as a pump or the like is connected to the ink tank <NUM>. By providing a negative pressure (relative to water head pressures at the inkjet heads <NUM>), the ink supplied to each nozzle <NUM> of the inkjet head <NUM> can be formed in a meniscus of a predetermined shape.

The supply pump <NUM> is, for example, a liquid feeding pump such as a piezoelectric pump. The supply pump <NUM> is provided in a supply flow passage. The supply pump <NUM> is connected to the control circuit <NUM> of the control unit <NUM> by a wiring and is configured so that the supply pump <NUM> can be controlled by the control unit <NUM>. The supply pump <NUM> supplies a liquid to the inkjet head <NUM>.

The conveyance device <NUM> conveys the sheet P from the medium supply unit <NUM> through the image forming unit <NUM> along the conveyance path R. The conveyance device <NUM> includes a plurality of guide plate pairs <NUM> disposed along the conveyance path R and a plurality of conveyance rollers <NUM>.

Each of the guide plate pairs <NUM> includes a pair of plate members disposed to face each other with the conveyed sheet P passing therebetween and serves to guides the sheet P along the conveyance path R.

The conveyance rollers <NUM> are driven to be rotated under the control of the control unit <NUM> so that the sheet P is conveyed downstream along the conveyance path R. In the conveyance path R, a sensor detecting a sheet conveyance status is disposed at each relevant position.

The control unit <NUM> includes a control unit <NUM> such as a CPU (central processing unit), a read-only memory (ROM) that stores various programs and the like, a random access memory (RAM) that temporarily stores various types of variable data, image data, and the like, and an interface unit that inputs data from the outside and outputs data to the outside.

In the inkjet recording apparatus <NUM>, if a printing instruction given by a user operating an operation input unit in an interface is detected, the control unit <NUM> drives the inkjet heads <NUM> by driving the conveyance device <NUM> to convey the sheet P and outputs a printing signal to the head units <NUM> at a predetermined timing. The inkjet heads <NUM> transmit a driving signal to the driving IC <NUM> as an image signal in accordance with image data for an ejecting operation, applying the driving voltages to the internal electrodes <NUM> and <NUM>, selectively to drive the piezoelectric elements <NUM> to vibrate to eject the ink from the necessary nozzles <NUM> by changing the volumes of the pressure chambers <NUM>, and thus form an image on the sheet P on the conveyance belt <NUM>. As a liquid ejecting operation, the control unit <NUM> supplies the ink from the ink tanks <NUM> to the common chambers <NUM> of the inkjet heads <NUM> by driving the supply pumps <NUM>.

Here, a driving operation of driving the inkjet head <NUM> will be described. The inkjet head <NUM> according to the present embodiment includes the driving piezoelectric element <NUM> disposed to face the pressure chamber <NUM>, and the driving piezoelectric element <NUM> is connected by a wiring so that a voltage can be applied. The control unit <NUM> transmits a driving signal to the driving IC <NUM> by an image signal in accordance with image data, applies a driving voltage to the internal electrodes <NUM> and <NUM> of the driving piezoelectric element <NUM> of the driving target, and selectively deforms the driving piezoelectric element <NUM> of the driving target. Then, a liquid is ejected by changing the volume of the pressure chamber <NUM> in combination of deformation in the tensile direction and deformation in the compression direction of the vibration plate <NUM>.

For example, the control unit <NUM> alternately performs a expanding and compression operation. In the inkjet head <NUM>, in the expanding operation of increasing an internal volume of the target pressure chamber <NUM>, the driving piezoelectric element <NUM> of the driving target is contracted and the driving piezoelectric element <NUM> which is not the driving target is not deformed. In the inkjet head <NUM>, in the compression operation of decreasing the internal volume of the target pressure chamber <NUM>, the driving piezoelectric element <NUM> of the target is stretched. The non-driving piezoelectric element <NUM> is not deformed.

In the inkjet head <NUM> and the inkjet recording apparatus <NUM> according to the above-described embodiment, the FPC <NUM> can be directly joined to the electrodes of the piezoelectric member by solder. That is, by setting a melting point of the solder within a range equal to or less than <NUM> / <NUM> of the Curie point of the piezoelectric member material, it is possible to perform mounting with high reliability without deterioration. For example, the PZT generally has a deterioration point which is about <NUM> / <NUM> of the Curie point. However, by setting the melting point of the solder of the solder layer <NUM> of the FPC <NUM> to be equal to or less than <NUM> / <NUM> of the Curie point of the piezoelectric material, it is possible to prevent the piezoelectric material from deteriorating. Since an electronic component such as the driving IC <NUM> mounted on the FPC <NUM>, the piezoelectric body, and the periphery of the piezoelectric body generate heat during operation and the piezoelectric body itself generates heat when driven, the temperature at junction <NUM> may increase to about <NUM> to <NUM>, for example. Therefore, if the melting point of the solder used at the junction <NUM> is too low, reliability in operation deteriorates. In the present embodiment, by setting the melting point of the solder to be equal to or greater than the highest attainment temperature expected at the junction <NUM>, it is possible to prevent the solder from being melted during the operation and avoid a mounting failure (connection failure).

With soldering, the FPC can be directly mounted on a piezoelectric structure portion by solder and the joining is performed without pressurization. Therefore, the thin and fragile piezoelectric elements divided by the grooves can be mounted without being damaged. In particular, the piezoelectric elements can be mounted without applying large pressures even in a configuration in which a joining strength of the piezoelectric material and the electrode material as in the stacked piezoelectric member <NUM> is weak.

A specific material or configuration of the piezoelectric elements <NUM> and <NUM> may be appropriately changed.

In an embodiment, the plurality of piezoelectric layers <NUM> are stacked and the driving piezoelectric elements <NUM> are driven through the vertical vibration (d33) in the stacking direction, but the present disclosure is not limited thereto. For example, the present disclosure can also be applied to a form in which the driving piezoelectric elements <NUM> are configured as a single-layered piezoelectric member or a form in which the driving piezoelectric elements <NUM> are driven through lateral vibration displaced in a d31 direction.

The arrangement of the nozzles <NUM> or the pressure chambers <NUM> is not limited. For example, the nozzles <NUM> may be arranged in two or more rows. An air chamber serving as a dummy chamber may be formed between the plurality of pressure chambers <NUM>. The inkjet head of an embodiment may be either a non-circulation type inkjet head or a circulation type inkjet head or either a side-shooter type inkjet head or an end-shooter inkjet head.

An example in which the piezoelectric elements <NUM> and <NUM> include the dummy layers <NUM> at both ends in the stacking direction is described but the present disclosure is not limited thereto. A dummy layer <NUM> may be included on only one side of the piezoelectric elements <NUM> and <NUM>, or excluded entirely. In addition, a configuration or a positional relationship of various components including the flow passage member <NUM>, the nozzle plate <NUM>, and the frame unit <NUM> can be appropriately changed.

An example in which the driving IC <NUM> functions as the heat generating element setting the highest attainable temperature was described, but the present disclosure is not limited thereto. For example, the heat generating element of concern may be a mounted component other than the driving IC <NUM> or may be the actuator unit <NUM>.

A liquid to be ejected is not limited to printing ink. For example, an apparatus or the like ejecting a liquid containing conductive particles for forming a wiring pattern of a printed wiring substrate may be used.

In an embodiment, the inkjet head <NUM> is used for a liquid ejecting apparatus such as an inkjet printer is described, but the present disclosure is not limited thereto. For example, the inkjet head <NUM> can also be advantageously used for a 3D printer, an industrial manufacturing machine, a medical device, or the like.

According to at least one of the above-described embodiments, it is possible to easily set a desired flow passage shape.

Claim 1:
A liquid ejecting head (<NUM>), comprising:
a piezoelectric member including a plurality of piezoelectric elements formed of a piezoelectric material;
a plurality of electrodes formed on the piezoelectric member; and
a wiring substrate (<NUM>) joined to the plurality of electrodes by solder, wherein
a melting point of the solder is less than or equal to <NUM>/<NUM> of the Curie point of the piezoelectric material.